tag:blogger.com,1999:blog-57361038980806828322024-03-14T00:33:54.193-04:00AvaMakesThingsava makes things and posts about themAvahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.comBlogger52125tag:blogger.com,1999:blog-5736103898080682832.post-46952181595393115052022-10-16T18:44:00.001-04:002022-10-16T22:23:01.984-04:00Bonsai Chile<p> This is my take on a "bonchi", or bonsai-style chile. The pepper is <i>Capsicum baccatum</i>, Bishop's Crown. I generally followed the advice on <a href="https://fatalii.net/bonchi">https://fatalii.net/bonchi</a> to turn a 3-year old, 4-foot tall indoor plant into a mini tree. While the big chop at the start was nervewracking, it's been growing great ever since.</p><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0FW_im9vFDA_5coC76yBHRvIbuaFd3Vsyud_YnT-uYamrsI5Ke3WL6dWFYpkjywSWAFUmqN9laQesYhjUyyf0Tyjo2smMhKSPLT354KAtmYPncj3mR3sWtxN4KdfWsOZGkwNR5F8sKb64y5gsqtsqkBFTPtr2M1QwLWoCRwTaFqC-viQyeMI_8K_Bsw/s3825/bonchi_pretty.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="3825" data-original-width="2904" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0FW_im9vFDA_5coC76yBHRvIbuaFd3Vsyud_YnT-uYamrsI5Ke3WL6dWFYpkjywSWAFUmqN9laQesYhjUyyf0Tyjo2smMhKSPLT354KAtmYPncj3mR3sWtxN4KdfWsOZGkwNR5F8sKb64y5gsqtsqkBFTPtr2M1QwLWoCRwTaFqC-viQyeMI_8K_Bsw/w486-h640/bonchi_pretty.jpg" width="486" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhHlj29niyXOMB8yCA8TT5-QR-z6brRZAM-OgkSuc-qdW_MjsdBoYQi88WOoJxiWuGN_gYNdWu-oK9rA0QdShBmfeK45H0BtjGiTDGFm6iW3x4QluzGYVmo9WJ6t_Kh9xVcPrNsoThMT0hGXRgADaj-WFe6B9-h-dy_HAgLb1hHqy2Cqr6suljHV2lIrg/s4032/IMG_1888.HEIC" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4032" data-original-width="3024" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhHlj29niyXOMB8yCA8TT5-QR-z6brRZAM-OgkSuc-qdW_MjsdBoYQi88WOoJxiWuGN_gYNdWu-oK9rA0QdShBmfeK45H0BtjGiTDGFm6iW3x4QluzGYVmo9WJ6t_Kh9xVcPrNsoThMT0hGXRgADaj-WFe6B9-h-dy_HAgLb1hHqy2Cqr6suljHV2lIrg/w480-h640/IMG_1888.HEIC" width="480" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIK89j9f_ua6tJvJ2qqPYIwehMQxaGt5B689UEyXLZmeKTopZFz9Mif3P41xooJ6pRdIgcB-u-G9jrpaUcka9zWgXjq2AkRIeVQG2kwM4K7qSxC1Cz2YOkEWKOkfBuZS7nqTC8e0nC3DfdV853ziB6stGB6h_iswPhVcqz0FJMf2XHimiF_TYzTIFyiA/s4032/IMG_1896.HEIC" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="4032" data-original-width="3024" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIK89j9f_ua6tJvJ2qqPYIwehMQxaGt5B689UEyXLZmeKTopZFz9Mif3P41xooJ6pRdIgcB-u-G9jrpaUcka9zWgXjq2AkRIeVQG2kwM4K7qSxC1Cz2YOkEWKOkfBuZS7nqTC8e0nC3DfdV853ziB6stGB6h_iswPhVcqz0FJMf2XHimiF_TYzTIFyiA/w480-h640/IMG_1896.HEIC" width="480" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">This is how it started, with a severe chop to a 3-year old plant and a new life on the countertop.</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEic0sEz0EAvQIHnwQ01BpjxhQMk0hHdUI6WsxpFhBwA3NXLwJzf-lWQ76MNh4cvihc_3zGBkxl_cnUCnF8a7a-WYAdS-r_lwTULTVOCJSv78NhJqJKiCFGBCQnT-bg2tEIGjotWHxQQgIR_OrmGJAh9FC93-ZkEELEWGidGtOaSwkJLsq9JJONhwmcstA/s1816/bonchi_start.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1816" data-original-width="1225" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEic0sEz0EAvQIHnwQ01BpjxhQMk0hHdUI6WsxpFhBwA3NXLwJzf-lWQ76MNh4cvihc_3zGBkxl_cnUCnF8a7a-WYAdS-r_lwTULTVOCJSv78NhJqJKiCFGBCQnT-bg2tEIGjotWHxQQgIR_OrmGJAh9FC93-ZkEELEWGidGtOaSwkJLsq9JJONhwmcstA/w432-h640/bonchi_start.jpg" width="432" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">152-day timelapse between first chop and first harvest.</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;"><div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen="" class="BLOG_video_class" height="424" src="https://www.youtube.com/embed/vPWu0ZsIn3o" width="510" youtube-src-id="vPWu0ZsIn3o"></iframe></div><br /> </div><br /><p></p>Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-55930466988501125722021-02-03T00:11:00.001-05:002021-02-03T00:11:29.285-05:00Daily webcomics email digest (self-hosted miniflux RSS server on RaspberryPi)<p>I want to keep up with a bunch of webcomics series without having to remember their update schedules. To do that, I set up a self-hosted RSS server (Miniflux) on Raspberry Pi to monitor for any updates, then wrote a script to email myself a daily 7am digest that directly links to the new pages.</p><p>Yes. This is complete overkill.</p><p>See, over the years I've kept track of ongoing series by just keeping a folder of bookmarked links. But some series update pages multiple times a week, some have short weekly chapters, some have monthly chapters, some have irregular schedules, and some of my favorites are on uncertain hiatus. I got irritated with the number of times I'd click through my bookmarks list and get nothing new.</p><p><br /></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuj3c94qaRO8nvuUZzrR8jmaq_OU25Z9OoF1L5yk5fXLhPU6oETPPI0DEpX9JpBMlh8nXPTholylg5Cs6TvAr-uuvzTwlW-zoMt9rBh0jrJVrz0Wgmt7kFDRHF3jo8Dby0bTCl1tGkFpDo/s591/bookmarks.jpg" style="margin-left: auto; margin-right: auto;"><img alt="bookmarks folder contains 22 comics" border="0" data-original-height="591" data-original-width="413" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhuj3c94qaRO8nvuUZzrR8jmaq_OU25Z9OoF1L5yk5fXLhPU6oETPPI0DEpX9JpBMlh8nXPTholylg5Cs6TvAr-uuvzTwlW-zoMt9rBh0jrJVrz0Wgmt7kFDRHF3jo8Dby0bTCl1tGkFpDo/w280-h400/bookmarks.jpg" title="bookmarks folder contains 22 comics" width="280" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">The number of comics in this folder was getting out of hand.</td></tr></tbody></table><br /><p>Why didn't I just designate Sunday mornings to check all of the comics? I don't have the self control for that. And, that method doesn't solve the hiatus issue or me getting distracted because possibly there's a new update.</p><p>Some of these are hosted on Webtoons, Tumblr, or other platforms that let you subscribe to alerts. But I wanted one daily email for comics, not fifty bajillion. An easy way to collect all updates in one place would be through a RSS reader with an email extension, since almost every webpage has RSS support and it's fairly simple to drop websites without an existing feed into an RSS generator. There are a bunch of decent, free RSS reader services out there. But weirdly, I couldn't find a single free RSS reader that would send email digests without having to interface through Zapier / IFTTT / etc (not-free tasker services). And having to log in to a RSS reader instead of checking my email was a no-go for me. </p><p>If I needed to set up my own email daemon, I might as well self-host the RSS database too. And, I wanted to put these on a separate computer that I could leave running 24/7. I used a Raspberry Pi 3B+ on a headless SSH setup for this project. Again, complete overkill.</p><p>I went with a <a href="https://github.com/miniflux/v2" rel="nofollow" target="_blank">Miniflux</a> build for the RSS server. It comes with a nice snappy interface, is open-source, and more relevantly has a Python API with lots of <a href="https://miniflux.app/docs/api.html" rel="nofollow" target="_blank">documentation</a>. As a bonus, it supports a Docker build for Raspbian. So all I had to do was follow the instructions, spin up docker-compose, and launch Pi's localhost webpage. Nice!</p><p>RSS comics server that checks for updates in the background, done.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg90HKLU7-ab47gdQjPHUq4Ay48sWXQKMS15KCerS7q7zrk7w2v7pDSKhyHH1_FcrIsnNa2aandKtr_5g9ZSCSf9toSt9zAUjbhj3dn8mTmFnV41IWN5woShOvu-8Vko8DvJw5yyrb5s8jr/s1534/miniflux_feeds.JPG" style="margin-left: auto; margin-right: auto;"><img alt="Miniflux comics feed webpage" border="0" data-original-height="1534" data-original-width="793" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg90HKLU7-ab47gdQjPHUq4Ay48sWXQKMS15KCerS7q7zrk7w2v7pDSKhyHH1_FcrIsnNa2aandKtr_5g9ZSCSf9toSt9zAUjbhj3dn8mTmFnV41IWN5woShOvu-8Vko8DvJw5yyrb5s8jr/w330-h640/miniflux_feeds.JPG" title="Miniflux comics feed webpage" width="330" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Managing the comic feeds through the browser-based UI </td></tr></tbody></table><br /><div>Next task was to write some code to pull page links from any unread comics and format a email message. This is easily accomplished for most comics by grabbing the default link encoded in the RSS feed alert. But a few RSS feeds had some quirks that needed individual attention. Unsounded's alert url points to the comments section instead of the updated page, but the page link could be extracted from the image links in the html content. And Kingdom's webhost creates an empty placeholder page a week before importing scanlated images, so the desired chapter is always one behind the alert.</div><div><br /></div><div>The code snippet below creates an html message with the current date and time, and formats each comic update in a bullet-point list. Then it tells the server to mark all as read.</div><div><br /><div>
<!--HTML generated using hilite.me--><div style="background: rgb(255, 255, 255); border-color: gray; border-image: initial; border-style: solid; border-width: 0.1em 0.1em 0.1em 0.8em; border: solid gray; overflow: auto; padding: 0.2em 0.6em; width: auto;"><table><tbody><tr><td><pre style="line-height: 125%; margin: 0px;"> 1
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tz <span style="color: #333333;">=</span> timezone(<span style="background-color: #fff0f0;">'US/Eastern'</span>)
now <span style="color: #333333;">=</span> datetime<span style="color: #333333;">.</span>now(tz)
dt_string <span style="color: #333333;">=</span> now<span style="color: #333333;">.</span>strftime(<span style="background-color: #fff0f0;">"%B %d, %Y %I:%M %p"</span>)
message <span style="color: #333333;">=</span> f<span style="background-color: #fff0f0;">'<b> {dt_string} </b><br><ul>'</span>
<span style="color: #008800; font-weight: bold;">for</span> entry <span style="color: black; font-weight: bold;">in</span> entries[<span style="background-color: #fff0f0;">'entries'</span>]:
series_title <span style="color: #333333;">=</span> entry[<span style="background-color: #fff0f0;">'feed'</span>][<span style="background-color: #fff0f0;">'title'</span>]
series_id <span style="color: #333333;">=</span> entry[<span style="background-color: #fff0f0;">'feed_id'</span>]
panel_title <span style="color: #333333;">=</span> entry[<span style="background-color: #fff0f0;">'title'</span>]
panel_url <span style="color: #333333;">=</span> entry[<span style="background-color: #fff0f0;">'url'</span>]
panel_content <span style="color: #333333;">=</span> entry[<span style="background-color: #fff0f0;">'content'</span>]
<span style="color: #008800; font-weight: bold;">if</span> series_id <span style="color: #333333;">==</span> <span style="color: #0000dd; font-weight: bold;">19</span>: <span style="color: #888888;">#unsounded default url links to tumblr not comic</span>
soup <span style="color: #333333;">=</span> BeautifulSoup(panel_content, <span style="background-color: #fff0f0;">'html.parser'</span>)
link <span style="color: #333333;">=</span> soup<span style="color: #333333;">.</span>find(<span style="background-color: #fff0f0;">'a'</span>,href<span style="color: #333333;">=</span><span style="color: #008800; font-weight: bold;">True</span>)
panel_url <span style="color: #333333;">=</span> link[<span style="background-color: #fff0f0;">'href'</span>]
<span style="color: #008800; font-weight: bold;">elif</span> series_id <span style="color: #333333;">==</span> <span style="color: #0000dd; font-weight: bold;">10</span>: <span style="color: #888888;">#kingdom updates to placeholder chapters, so increment one chapter back</span>
ch_num <span style="color: #333333;">=</span> re<span style="color: #333333;">.</span>search(<span style="background-color: #fff0f0;">r'\d+'</span>, panel_url)<span style="color: #333333;">.</span>group()
new_ch_num <span style="color: #333333;">=</span> <span style="color: #007020;">str</span>(<span style="color: #007020;">int</span>(ch_num)<span style="color: #333333;">-</span><span style="color: #0000dd; font-weight: bold;">1</span>)
panel_url <span style="color: #333333;">=</span> panel_url<span style="color: #333333;">.</span>replace(ch_num, new_ch_num)
panel_title <span style="color: #333333;">=</span> panel_title<span style="color: #333333;">.</span>replace(ch_num, new_ch_num)
message <span style="color: #333333;">=</span> message <span style="color: #333333;">+</span> f<span style="background-color: #fff0f0;">'<li><a href={panel_url}>{series_title} - {panel_title}</a>'</span>
message <span style="color: #333333;">=</span> message <span style="color: #333333;">+</span> <span style="background-color: #fff0f0;">'</ul>'</span>
client<span style="color: #333333;">.</span>mark_category_entries_as_read(category_id)
<span style="color: #008800; font-weight: bold;">return</span> message
</pre></td></tr></tbody></table></div>
</div></div>
<div><br /></div><div>After that, I needed to give the script OAuth2 credentials to send emails through Gmail. <a href="https://blog.macuyiko.com/post/2016/how-to-send-html-mails-with-oauth2-and-gmail-in-python.html" rel="nofollow" target="_blank">This guide</a> provided straightforward instructions and a useful code template for Python3. I did modify the <span style="font-family: courier;">refresh_authorization</span><span style="font-family: inherit;"> function to pass over a new refresh token if the current one's about to expire.</span></div><div><span style="font-family: inherit;"><br /></span></div><div><span style="font-family: inherit;">To make the new refresh token persist across runs, I wrote a function to rewrite the line that stores the string. I don't fully understand how Python allows writing to a file that's currently open:</span></div><div><br /></div>
<!--HTML generated using hilite.me--><div style="background: rgb(255, 255, 255); border-color: gray; border-image: initial; border-style: solid; border-width: 0.1em 0.1em 0.1em 0.8em; border: solid gray; overflow: auto; padding: 0.2em 0.6em; width: auto;"><table><tbody><tr><td><pre style="line-height: 125%; margin: 0px;"> 1
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content <span style="color: #333333;">=</span> []
<span style="color: #008800; font-weight: bold;">with</span> <span style="color: #007020;">open</span>(__file__,<span style="background-color: #fff0f0;">"r"</span>) <span style="color: #008800; font-weight: bold;">as</span> f:
<span style="color: #008800; font-weight: bold;">for</span> line <span style="color: black; font-weight: bold;">in</span> f:
content<span style="color: #333333;">.</span>append(line)
<span style="color: #008800; font-weight: bold;">with</span> <span style="color: #007020;">open</span>(__file__,<span style="background-color: #fff0f0;">"w"</span>) <span style="color: #008800; font-weight: bold;">as</span> f:
content[<span style="color: #0000dd; font-weight: bold;">36</span>] <span style="color: #333333;">=</span> <span style="background-color: #fff0f0;">"GOOGLE_REFRESH_TOKEN = {n}</span><span style="background-color: #fff0f0; color: #666666; font-weight: bold;">\n</span><span style="background-color: #fff0f0;">"</span><span style="color: #333333;">.</span>format(n<span style="color: #333333;">=</span>refresh_token) <span style="color: #888888;">#modifies line 37</span>
<span style="color: #008800; font-weight: bold;">for</span> i <span style="color: black; font-weight: bold;">in</span> <span style="color: #007020;">range</span>(<span style="color: #007020;">len</span>(content)):
f<span style="color: #333333;">.</span>write(content[i])
<span style="color: #008800; font-weight: bold;">def</span> <span style="color: #0066bb; font-weight: bold;">send_mail</span>(fromaddr, toaddr, subject, message):
new_token, oauth_response <span style="color: #333333;">=</span> refresh_authorization(GOOGLE_CLIENT_ID, GOOGLE_CLIENT_SECRET, GOOGLE_REFRESH_TOKEN)
<span style="color: #008800; font-weight: bold;">if</span> new_token:
refresh_token <span style="color: #333333;">=</span> oauth_response[<span style="background-color: #fff0f0;">'refresh_token'</span>]
<span style="color: #008800; font-weight: bold;">else</span>:
refresh_token <span style="color: #333333;">=</span> []
access_token <span style="color: #333333;">=</span> oauth_response[<span style="background-color: #fff0f0;">'access_token'</span>]
expires_in <span style="color: #333333;">=</span> oauth_response[<span style="background-color: #fff0f0;">'expires_in'</span>]
auth_string <span style="color: #333333;">=</span> generate_oauth2_string(fromaddr, access_token, as_base64<span style="color: #333333;">=</span><span style="color: #008800; font-weight: bold;">True</span>)
<span style="color: #333333;">...</span>
</pre></td></tr></tbody></table></div>
<div><br /></div><div>(in hindsight, using a pickle file to store the refresh_token variable would've been more reasonable)</div><div><br /></div><div>Main function is fairly simple. Connect to server, find out how many unread comics there are, format the subject text and message html, and send an email:</div><div><br /></div>
<!--HTML generated using hilite.me--><div style="background: rgb(255, 255, 255); border-color: gray; border-image: initial; border-style: solid; border-width: 0.1em 0.1em 0.1em 0.8em; border: solid gray; overflow: auto; padding: 0.2em 0.6em; width: auto;"><table><tbody><tr><td><pre style="line-height: 125%; margin: 0px;"> 1
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client <span style="color: #333333;">=</span> miniflux<span style="color: #333333;">.</span>Client(MINIFLUX_URL, api_key<span style="color: #333333;">=</span>MINIFLUX_CLIENT_API)
entries <span style="color: #333333;">=</span> client<span style="color: #333333;">.</span>get_entries(status<span style="color: #333333;">=</span><span style="background-color: #fff0f0;">'unread'</span>, limit<span style="color: #333333;">=</span><span style="color: #0000dd; font-weight: bold;">100</span>, direction<span style="color: #333333;">=</span><span style="background-color: #fff0f0;">'desc'</span>)
<span style="color: #008800; font-weight: bold;">if</span> <span style="background-color: #fff0f0;">'total'</span> <span style="color: black; font-weight: bold;">in</span> entries:
unread_count <span style="color: #333333;">=</span> entries[<span style="background-color: #fff0f0;">'total'</span>]
<span style="color: #008800; font-weight: bold;">if</span> unread_count <span style="color: #333333;">==</span> <span style="color: #0000dd; font-weight: bold;">0</span>:
<span style="color: #007020;">print</span>(<span style="background-color: #fff0f0;">'process successful, no new comics'</span>)
exit()
<span style="color: #008800; font-weight: bold;">elif</span> unread_count <span style="color: #333333;">==</span> <span style="color: #0000dd; font-weight: bold;">1</span>:
subjectmessage <span style="color: #333333;">=</span> f<span style="background-color: #fff0f0;">'This morning</span><span style="background-color: #fff0f0; color: #666666; font-weight: bold;">\'</span><span style="background-color: #fff0f0;">s {unread_count} comic update'</span>
<span style="color: #008800; font-weight: bold;">else</span>:
subjectmessage <span style="color: #333333;">=</span> f<span style="background-color: #fff0f0;">'This morning</span><span style="background-color: #fff0f0; color: #666666; font-weight: bold;">\'</span><span style="background-color: #fff0f0;">s {unread_count} comic updates'</span>
bodyhtml <span style="color: #333333;">=</span> process_unreads(client, entries, COMICS_CATEGORY_ID)
new_token, refresh_token <span style="color: #333333;">=</span> send_mail(GMAIL_SENDER, GMAIL_RECEIVER,
subjectmessage,
bodyhtml)
<span style="color: #008800; font-weight: bold;">if</span> new_token:
save_token_string(refresh_token)
<span style="color: #007020;">print</span>(<span style="background-color: #fff0f0;">'email sent successfully'</span>)
exit()
<span style="color: #008800; font-weight: bold;">else</span>:
<span style="color: #007020;">print</span>(<span style="background-color: #fff0f0;">'weird error occured'</span>)
exit()
</pre></td></tr></tbody></table></div>
<div><br /></div><div class="separator" style="clear: both; text-align: left;">That's the digest updater script! (<a href="https://gist.github.com/avachen/391db99690cbd94780b24e1f62ce2da8" target="_blank">link to view full code</a>)</div><div class="separator" style="clear: both; text-align: left;">Last thing is to schedule a cronjob to run this code every day at 7am. </div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">The result is pretty much everything I wanted! </div><div class="separator" style="clear: both; text-align: left;">All comics in one email sitting in my inbox, and I can put filters to snooze it until after work if I failed to wake up early enough to click on it.</div><div class="separator" style="clear: both; text-align: center;"><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjnCE3LWCGlbnlqHhdb1p7FlUqP7iZr81NNtDV0k_CwrDhDu0LdSNWRCUmebdrn6GvIW8BgwL5V-37Ff6DRwug2Dy7qONcf8FpteIkV5z0m95q3O6_nXmzIVvq4jd5yJG1GOTDYGy3o25KE/s806/email_line.JPG"><img alt="inbox screenshot with new digest email" border="0" data-original-height="67" data-original-width="806" height="54" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjnCE3LWCGlbnlqHhdb1p7FlUqP7iZr81NNtDV0k_CwrDhDu0LdSNWRCUmebdrn6GvIW8BgwL5V-37Ff6DRwug2Dy7qONcf8FpteIkV5z0m95q3O6_nXmzIVvq4jd5yJG1GOTDYGy3o25KE/w640-h54/email_line.JPG" title="inbox screenshot with new digest email" width="640" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_vyKxXSdElE_YtbdOCenZ4ByAgGuDb8zdm1I6YzF_5DYvzDHCLSJXtFOLgZECey34vJTLhm-Sn1JPuxb6QRrZAhsmNAqphm4NEkVqWLOK6pLava8O5eD7ucGBD67SKrMIKp0YSQiFqcBJ/s665/email_content.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="email body lists four updated comics" border="0" data-original-height="220" data-original-width="665" height="133" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_vyKxXSdElE_YtbdOCenZ4ByAgGuDb8zdm1I6YzF_5DYvzDHCLSJXtFOLgZECey34vJTLhm-Sn1JPuxb6QRrZAhsmNAqphm4NEkVqWLOK6pLava8O5eD7ucGBD67SKrMIKp0YSQiFqcBJ/w400-h133/email_content.JPG" title="email body lists four updated comics" width="400" /></a></div><br /><div>I also now have an easy way to set up RSS digest emails for any other category. A weekly digest for MITERS folks' blogs are an obvious next step.</div><div><br /></div><div>Then there's the Raspberry Pi begging to be utilized for more intensive automated things. More to come when I think of something cool.</div><div><br /></div><div><br /></div>Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com1tag:blogger.com,1999:blog-5736103898080682832.post-59209828478975245162020-08-19T02:39:00.008-04:002020-08-25T19:31:59.157-04:00A method of generating pixel-art from digital images in limited-color palettes, suitable for DIY cross-stitch patterns<p></p><p><a href="https://rip-in-pepperinos.itch.io/bless-this-snek" target="_blank">If you want this pattern, it's available as a pay-what-you-wish PDF and KXStitch download on itch.io</a></p><p>My friend made a cross-stitch piece, and it's been generating a surprising amount of enthusiasm!<br /></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhehvFhmSlPl5TuwEQUhdWHnrUX4zrGgw5gAqr74vR8JH1dQx2nep52xQW1rZxz2LuAGCcBW9VHavX6zZilg2LKlC86j_ARJGstNMhLFI5gjIwwomqQRr1O5SyYJo7afmhimGnttoZ7-zpf/s2048/cadmus_crossstitch.jpg" style="margin-left: auto; margin-right: auto;"><img alt="cross-stitch pattern of a corn snake depicted as an ouroboros with text Bless This Snek in the center. The pet corn snake's head is resting on top of its stitched portrait." border="0" data-original-height="1536" data-original-width="2048" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhehvFhmSlPl5TuwEQUhdWHnrUX4zrGgw5gAqr74vR8JH1dQx2nep52xQW1rZxz2LuAGCcBW9VHavX6zZilg2LKlC86j_ARJGstNMhLFI5gjIwwomqQRr1O5SyYJo7afmhimGnttoZ7-zpf/w640-h480/cadmus_crossstitch.jpg" title="cross-stitch pattern of a corn snake depicted as an ouroboros with text Bless This Snek in the center. The pet corn snake's head is resting on top of its stitched portrait." width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Cadmus the corn snake with his portrait<br /></td></tr></tbody></table><p><span></span></p><a name='more'></a>(shameless reddit plugs <a href="https://www.reddit.com/r/CrossStitch/comments/iat9k5/fo_homecoming_gift_for_my_housemate_and_their/" target="_blank">one</a>, <a href="https://www.reddit.com/r/snakes/comments/ibc22e/a_crossstitch_for_my_housemates_corn_snake_cadmus/" target="_blank">two</a>, <a href="https://www.reddit.com/r/Snek/comments/ibc5z1/tank_sweet_tank_for_my_housemates_snek/" target="_blank">three</a>)<p></p><p>While you will have to talk to <a href="https://old.reddit.com/user/rip_in_pepperinos" rel="nofollow" target="_blank">/u/rip_in_pepperinos</a> about the final steps of sampling points (digitally doable, see <a href="https://www.avamakesthings.com/2020/08/whale-blackwork-pattern.html">my blackwork post</a>), picking thread closest-colors, adding text, and ultimately sewing the piece (around 30 hours of stitching!)... converting from a photo or drawing to a pixel-art proto-pattern is relatively straightforward.<br />(10 min – 1 hr process, depending on how familiar you are with the tools)</p><h3 style="text-align: justify;"></h3><blockquote><h3 style="text-align: justify;">Method Recipe (each step links to sections of this blog post):</h3><p style="text-align: justify;"><a href="https://www.avamakesthings.com/2020/08/image-to-pixel-art-cross-stitch.html#step1">1. Resize image to desired DPI and stitch-pattern size (Cadmus was 25 DPI, 300 px (6 in) length)</a></p><p style="text-align: justify;"><a href="https://www.avamakesthings.com/2020/08/image-to-pixel-art-cross-stitch.html#step2">2. Posterize image to desired number of colors</a></p><p style="text-align: justify;"><a href="https://www.avamakesthings.com/2020/08/image-to-pixel-art-cross-stitch.html#step3">3. (optional) Use hue/saturation adjustment and magic wand tool to recolor image to your desired color palette</a></p></blockquote><p></p><blockquote><a href="https://www.avamakesthings.com/2020/08/image-to-pixel-art-cross-stitch.html#step4">4. (optional) Other quality-of-life things that you can do to be more kind to the sewer / pattern-maker</a> </blockquote><p></p><blockquote><p style="text-align: justify;"><span style="text-align: left;"> </span></p></blockquote><p style="text-align: justify;"></p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIdHsVKUKw_oeK9ujCQ5M7oHd_8YuHAUw4FEkheG_vaP0FEfqd9uW78YTkI3AOx6gQ7c4ZC-56FNlQMWL-uUZkbQL4Gu78q7X9ku3-3J1z8aK2acA8bEPBq_fsAgCFT1F6b3CGafEfR14Q/s2048/cadmus_sketch.jpeg" style="margin-left: auto; margin-right: auto;"><img alt="marker drawing of corn snake as an ouroboros" border="0" data-original-height="1536" data-original-width="2048" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIdHsVKUKw_oeK9ujCQ5M7oHd_8YuHAUw4FEkheG_vaP0FEfqd9uW78YTkI3AOx6gQ7c4ZC-56FNlQMWL-uUZkbQL4Gu78q7X9ku3-3J1z8aK2acA8bEPBq_fsAgCFT1F6b3CGafEfR14Q/w640-h480/cadmus_sketch.jpeg" title="marker drawing of corn snake as an ouroboros" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Original drawing using six markers (plus white paper)</td></tr></tbody></table><br /><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7yS8Jw_GXpJOOSayt8nA9doWfSNJcX-eLoOQali5JeF4ow5jmYimbd9f8V15VMG2Qd247_YSgAj6V-jTn1NEGicv3LHIKsxC5XE6kzgwibeBH9jYgAkpGSRI5Hl9teBEFtIYzHALH92VD/s1897/cadmus_pixel.png" style="margin-left: auto; margin-right: auto;"><img alt="final pixel art rendition" border="0" data-original-height="1811" data-original-width="1897" height="611" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7yS8Jw_GXpJOOSayt8nA9doWfSNJcX-eLoOQali5JeF4ow5jmYimbd9f8V15VMG2Qd247_YSgAj6V-jTn1NEGicv3LHIKsxC5XE6kzgwibeBH9jYgAkpGSRI5Hl9teBEFtIYzHALH92VD/w640-h611/cadmus_pixel.png" title="final pixel art rendition" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Finished pixel-art using eleven colors <br />(plus some extra colors from digital artifacts, which I did not fix but you can! Will be addressed later in this post)</td></tr></tbody></table><p></p><blockquote>Note: the original marker drawing for the Cadmus pattern, although being a quick sketch, is something I am extremely uninterested in responding to and redrawing by commission. Art requires practice and emotional labor, and monetizing art is an actual job. If you came here looking for someone to create a custom drawing of your beloved pet from a photo, go find a professional artist whose style you like and pay their posted price. I guarantee you that they are making below minimum wage for the hours and labor required for them to pursue their passion. If <i>you</i> want your photo to look more like a drawing / painting but find art difficult, don't lose hope! Both the pixelating process and some style plug-in programs that I mention later in this post mimic some painting-like abstractions and only require artistic taste, not technique.</blockquote><p>You will need a graphics editor software with the ability to resize an image, adjust brightness/contrast, a "magic wand" select-by-color tool with adjustable tolerance, a "paint bucket" fill-selection tool, and a paint palette that allows you to enter HEX values and save custom colors. These are all tools that any basic, free graphics program will have (popular multi-OS programs include Inkscape and GIMP). For this application, you will probably want a program that already includes a "Posterize Effect", which automatically reduces the number of colors in an image (commonly used to produce graphics for posters). There are free website-based tools that will do this for you if your graphics program doesn't have it by default. It's also nice, but not necessary, to use a program with image layer functionality. Throughout this post, I am using <a href="https://www.getpaint.net/" rel="nofollow" target="_blank">Paint.Net</a>, a free program for Windows.</p><p></p><p>Basically, our goal is to convert a high-resolution, many-color image to a low-resolution, few-color one. At minimum, we first use the resize function to achieve pixelation and limit spatial resolution then use the posterize function to limit colors.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIyhbvh0nV5AWMv-6qLyP9MrCoB-zp6PD1pbC9WFiYUL-5K6xmIC-CMRZ4cJAq_MOpijafstp5jS51Jb9tGCz4YwvNEFSH1YbdELbM83K2lw3huQ6YYGZhsQZYDJ3dbD0SNX1TybX97Pas/s2007/hands.png" style="margin-left: auto; margin-right: auto;"><img alt="progression of four images that become increasingly pixelated and color-limited" border="0" data-original-height="439" data-original-width="2007" height="140" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjIyhbvh0nV5AWMv-6qLyP9MrCoB-zp6PD1pbC9WFiYUL-5K6xmIC-CMRZ4cJAq_MOpijafstp5jS51Jb9tGCz4YwvNEFSH1YbdELbM83K2lw3huQ6YYGZhsQZYDJ3dbD0SNX1TybX97Pas/w640-h140/hands.png" title="progression of four images that become increasingly pixelated and color-limited" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Left to right: Original stock image photo, Resized and zoomed in, Posterized, Re-tinting and changed color saturation (optional). Click on this image to see full-sized pixelation view!</td></tr></tbody></table><p>However, we can play with our graphics software and give the photo some artsy effects before using this pipeline. Any basic digital effect that either lowers resolution (blurs, outlines, brightness and contrast adjustment) or removes color variation (convert to grayscale or sepia, convert to binary black/white, adjust hue or saturation, adjust brightness or contrast) is useful to us.</p><p>Many programs support free plugins from community members. Here, I take the original stock photo and use <a href="https://forums.getpaint.net/topic/113220-boltbaits-plugin-pack-for-pdn-v4212-and-beyond-updated-july-16-2020/" rel="nofollow" target="_blank">BoltBait's "Pastel Effect"</a> to get a watercolor style that both blurs and reduces color variety in the image.</p><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgidmmHFDXt02jOcd12Fkr1GQe3mCNsaRoKCdDydKz3Gp4aqSoxn0AEpBbiQAAu6dfeB0h34NLa87fo6WKrsIfIz3IP7lNk51f0rUMFEf1lupM93Av81lwBUhzIATNoVs1A2pCFmpJumEgW/s500/pastel_hands.png" style="margin-left: auto; margin-right: auto;"><img alt="stock photo using pastel effect to achieve a painted style with saturated blues and oranges" border="0" data-original-height="431" data-original-width="500" height="345" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgidmmHFDXt02jOcd12Fkr1GQe3mCNsaRoKCdDydKz3Gp4aqSoxn0AEpBbiQAAu6dfeB0h34NLa87fo6WKrsIfIz3IP7lNk51f0rUMFEf1lupM93Av81lwBUhzIATNoVs1A2pCFmpJumEgW/w400-h345/pastel_hands.png" title="stock photo using pastel effect to achieve a painted style with saturated blues and oranges" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Boltbait's 'Pastel Effect' with Size value 5 and Roughness value 255</td></tr></tbody></table><br /><div>Most graphics programs will include a range of image adjustment and effects options by default, and these go a long way towards making a photo look like an artistic rendering. Learn to love 'Undo' buttons and make some art!<br /><br /><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0cPeHWD4Paug_qPFHbDMXFtijpiLRG2LpG9qLFGo-v_rJj-EPF3EGQSBa8hZdBjMUBUQ6FSLSrB_imMUTAp3Y8ydqy0toVX77oL8X91NStOap6IasTVzH8aNw44Ji81Ej3e1i2dirVKod/s500/pastel_hands_purple_inksketch.png" style="margin-left: auto; margin-right: auto;"><img alt="pastel image recolored to purples and greens with a sketch-like black outline effect adding shadows" border="0" data-original-height="431" data-original-width="500" height="345" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg0cPeHWD4Paug_qPFHbDMXFtijpiLRG2LpG9qLFGo-v_rJj-EPF3EGQSBa8hZdBjMUBUQ6FSLSrB_imMUTAp3Y8ydqy0toVX77oL8X91NStOap6IasTVzH8aNw44Ji81Ej3e1i2dirVKod/w400-h345/pastel_hands_purple_inksketch.png" title="pastel image recolored to purples and greens with a sketch-like black outline effect adding shadows" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Boltbait's Pastel Effect (see previous image)<br />Hue/Saturation adjusted to -103 to get a green/purple color scheme.<br />Brightness adjusted to -75 and contrast to 50 to amplify watercolor effect.<br /> Ink Sketch effect applied with Outline value 75 and Coloring value 100.<br /><br /></td></tr></tbody></table><p>Consider this "watercolor" version. At this point, we have taken a fairly-detailed image of two human hands holding hands and reduced the colors to just purples, blues, greens, and black. We have captured most of the highlights and shadows as well-defined blocks of color, and have simplified most of the shapes in this image without making the hands unrecognizable — all of this before even starting the stitch-pixelation routine.</p><p>I'll walk through the pipeline steps with both the original hands-stock-image (called "Photo" going forward) and the recolored green/purple (called "Painting") to further highlight how stylistic changes carry forward into pixelation.</p><p><br /></p><h3 id="step1" style="text-align: left;"> Step 1: Resize image to desired DPI and stitch-pattern size (and take advantage of screenshots)</h3><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwlRw3YIbgp-Lcmsl-oRDT06VYmsU2UPt-fc9YaALh8tQpLxA4DE6xaWHtd8NSenWZSqK_S_zG2V5ombw2F2hkBtDGwaj72ObORFqfsqLMBNj6lCZ9r5Q8cXGa1EXOMVnDW_x_x2VTl8Sh/s2048/hands_resized.JPG" style="margin-left: auto; margin-right: auto;"><img alt="resized Photo (left) and Painting (right), with Resize menu showing resolution changed to 25 DPI and height changed to 6 inches" border="0" data-original-height="1061" data-original-width="2048" height="332" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwlRw3YIbgp-Lcmsl-oRDT06VYmsU2UPt-fc9YaALh8tQpLxA4DE6xaWHtd8NSenWZSqK_S_zG2V5ombw2F2hkBtDGwaj72ObORFqfsqLMBNj6lCZ9r5Q8cXGa1EXOMVnDW_x_x2VTl8Sh/w640-h332/hands_resized.JPG" title="resized Photo (left) and Painting (right), with Resize menu showing resolution changed to 25 DPI and height changed to 6 inches" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Most image-resize functions allow you to change image resolution and width/height. For our purposes, the actual resampling algorithm used by the graphics editor is unimportant.</td></tr></tbody></table><div><br /></div><div>Many graphics programs have a hard time forcing image elements to adhere to strict grid systems. If your program has a snap-to-grid feature and a pixelate distortion function (not uncommon, but mine does not) then you can achieve the same effect with those methods.</div><div><br /></div><div>This method forces the graphics editor to use a grid system by limiting the number of pixels available to it (and then you can still save a high-resolution image by taking a screenshot of your display)</div><div><br /></div><div>The "Resize Image" function (sometimes called "Scale Image") is usually in the "Image" sub-menu. You will want to change the image resolution to your desired pattern resolution (25 Dots Per Inch is common). The width and height setting will define how big the final pattern is. You will also want to make any compositional changes (such as cropping image to change where the center point is) at this time.</div><div><br /></div><div>After you've resized your image, maybe you want your piece to use even larger pixel blocks. You can continue reducing the resolution if you like; just keep in mind that your image pixel dimensions (length and width) need to evenly divide by whatever resolution you are picking. Some graphics programs let you specify units in the resize menu so you don't have to do arithmetic, but if not... be careful!</div><div><br /></div><h3 id="step2" style="text-align: left;">Step 2: Posterize image to desired number of colors</h3><div>This is the main step. At this point, you have an image in the approximate visual style that you're going for, and all you need to do make the image not require infinite colors. This means that you have outlines, highlights, and shadows where you want them (although you definitely can add these by hand later).</div><div><br /></div><div>The "Posterize" filter recolors an image using a specified number of colors. It will use a Nearest-Neighbors algorithm to find a set of colors that best match the original image. In Paint.Net, the settings give you control over the maximum number of RGB values available to the algorithm.</div><div><br /></div><div>A quick go-over of simplified digital color theory: Light that comes from your computer screen is made from Red, Green, and Blue light additively mixing, so colors are defined by RGB "channels". White is maximum values of all channels. Black is no light of any color (not actually true, but this is simplified color theory). Pure Red is just that with no Green or Blue. One bit (unit of data) of Red will be pure red. More bits in the Red channel will increase the numbers of levels of intensity (more subtleties in color) the computer screen will display. Behind the scenes, Paint.Net is taking your specified number of colors per RGB channel and thresholding the RGB bits defining the colors it is showing you.</div><div><br /></div><div>In Paint.Net, each color channel normally has up to 256 possible values (0 through 255). The posterize tool lets you limit from 2 to 64. The total maximum number of colors your image will have is the multiplication of each color channel's threshold (so limiting to 8 values per channel, as below, forces a maximum of 512 color possibilities). The additional requirement of attempting to match original colors makes the below image contain significantly fewer than 512 colors.</div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitKZnGNb2RKjBQOE1hSKXR-ZxQR74iauSZedMl_uRx853nqFdbboo37qBnqm5muUFzo9mAU3fvP4-LMSWzJ2pw7W4jnxGBEbRaI98jxSuyZyrm5mv5PRRYeThoSkSyA8NOODhwrq8kEUz9/s2048/photo_posterized_linked.JPG" style="margin-left: auto; margin-right: auto;"><img alt="Hands stock photo with posterize effect, which convert subtle gradients of shade and hue into blocks of uniform colors" border="0" data-original-height="1320" data-original-width="2048" height="412" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitKZnGNb2RKjBQOE1hSKXR-ZxQR74iauSZedMl_uRx853nqFdbboo37qBnqm5muUFzo9mAU3fvP4-LMSWzJ2pw7W4jnxGBEbRaI98jxSuyZyrm5mv5PRRYeThoSkSyA8NOODhwrq8kEUz9/w640-h412/photo_posterized_linked.JPG" title="Hands stock photo with posterize effect, which convert subtle gradients of shade and hue into blocks of uniform colors" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Photo with RGB thresholds each set to value 8, such that image is limited to 512 possible colors.<br /></td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">You might be wondering what the "linked" checkbox is for. Typically, to maintain an average adherence to the original color scheme you would want the same thresholds for the RGB channels. But maybe you wouldn't mind a rosier image, as in below. If you limit the red hues more than green or blue, the algorithm has fewer shades of red available and overall saturation of reddish components become more intense (sorta counter-intuitive that decreasing red threshold value increases output redness). </div><div class="separator" style="clear: both; text-align: center;"><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUajkfuf2KFFpSdBD77vLZViOsxXqUQGA8WLB38C7BzrY1FVSbpN9kL_fhO-A_zxrrczmXm4Phyl9RYN4ya6rWnuULNRx6rsyxtjIuJHBie2m7_kZoajDr8GysZRWby6HNH6x2D6Hc_Inm/s2048/photo_posterized_unlinked.JPG" style="margin-left: auto; margin-right: auto;"><img alt="posterized Photo example with the hands colored in a peachier tone than in the previous image." border="0" data-original-height="1325" data-original-width="2048" height="414" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUajkfuf2KFFpSdBD77vLZViOsxXqUQGA8WLB38C7BzrY1FVSbpN9kL_fhO-A_zxrrczmXm4Phyl9RYN4ya6rWnuULNRx6rsyxtjIuJHBie2m7_kZoajDr8GysZRWby6HNH6x2D6Hc_Inm/w640-h414/photo_posterized_unlinked.JPG" title="posterized Photo example with the hands colored in a peachier tone than in the previous image." width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Less of the forearm and backs of hands contain the greenish shading component when R channel is set to value 6 (G and B channels remain at value 8).</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjeTeCopqKcvAzjHUREnpWd4_1UmV0h4D1KeeQ-XFjwKs6hyphenhyphencjvcDG85Mb3frwIytYIaf9AZojyFNQkKiC4_k_xgGVIomONrBQb4L83iVXi_NrFfNjJn-E0SzddWB00RrrPTWY7ieH4BN2m/s2048/painting_posterized_linked.JPG" style="margin-left: auto; margin-right: auto;"><img alt="posterize thresholds of 8 colors per channel do not significantly affect the predominately green/purple Painting Render" border="0" data-original-height="1317" data-original-width="2048" height="412" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjeTeCopqKcvAzjHUREnpWd4_1UmV0h4D1KeeQ-XFjwKs6hyphenhyphencjvcDG85Mb3frwIytYIaf9AZojyFNQkKiC4_k_xgGVIomONrBQb4L83iVXi_NrFfNjJn-E0SzddWB00RrrPTWY7ieH4BN2m/w640-h412/painting_posterized_linked.JPG" title="posterize thresholds of 8 colors per channel do not significantly affect the predominately green/purple Painting Render" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">If your image is color-limited to begin with, Posterize filters have less of an effect.<br /></td></tr></tbody></table><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPMiM6ixNpMBdv2PwKw7gOBgIYAp-sP9fiwxsuoGaYyk6zRWb__xCoh-UNjypSq1EawcYlXNqbjBpaAjxxF0pbo2aY6l3HmWXGLeQBxiolM7Q9YGRZAa_b8L5OxJN8oDMgd5oI_da5JGgi/s1518/painting_overposterizedx2.jpg" style="margin-left: auto; margin-right: auto;"><img alt="The watercolor Painting with identical color blocks but greater saturation in hues" border="0" data-original-height="1517" data-original-width="1518" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPMiM6ixNpMBdv2PwKw7gOBgIYAp-sP9fiwxsuoGaYyk6zRWb__xCoh-UNjypSq1EawcYlXNqbjBpaAjxxF0pbo2aY6l3HmWXGLeQBxiolM7Q9YGRZAa_b8L5OxJN8oDMgd5oI_da5JGgi/w400-h400/painting_overposterizedx2.jpg" title="The watercolor Painting with identical color blocks but greater saturation in hues" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">It is possible to apply the Posterize filter more than once. Eventually reduction in numbers of colors ends and you only see changes in color saturation.<br /></td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><div>(If you like the posterize idea but having to select RGB channel values bug you, Paint.Net forums have various other implementations (<a href="https://forums.getpaint.net/topic/110520-poster-new-as-of-28th-october-2016/" rel="nofollow" target="_blank">link 1</a>, <a href="https://forums.getpaint.net/topic/12940-posterize-in-hsv-space/" rel="nofollow" target="_blank">link 2</a>) of the idea using Hue/Saturation/Value bands (HSV). There are also a number of browser tools that you can pop your image into and manually select a color palette - I would recommend using a full-resolution screenshot of your pixelated image)</div><div><br /></div><div>At this point, you now have a perfectly viable pixel-art piece. In fact, for the Cadmus piece I stopped here and passed it on for use as a pattern — this worked out great! However, there was a fair bit of work between having the Cadmus pixel art and getting a feasible cross-stitch pattern. Much of this work can be avoided with minimal extra effort on the pixel-art generator side.</div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEisHwDoyNTapRL9RV-FO6E3aE0OtHBqSd27BOrwgwM4Fz8kH9PjxRaTi-hXkZLOrtBJVJ884hX7h5HTNxED48j96GziVKfDXf213jFi8WPqNfibd1gDop9DlKLSiVlQ1Om3EPHya68I2yvU/s2048/hands_grid.JPG" style="margin-left: auto; margin-right: auto;"><img alt="closeup view of pixel-art hands photo" border="0" data-original-height="1580" data-original-width="2048" height="494" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEisHwDoyNTapRL9RV-FO6E3aE0OtHBqSd27BOrwgwM4Fz8kH9PjxRaTi-hXkZLOrtBJVJ884hX7h5HTNxED48j96GziVKfDXf213jFi8WPqNfibd1gDop9DlKLSiVlQ1Om3EPHya68I2yvU/w640-h494/hands_grid.JPG" title="closeup view of pixel-art hands photo" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">You could just get the thread colors and stitch based on this, but you can do better</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><div>Here, we learn from my initial mistakes and strive to be better. A side takeaway from this post is an example of someone making a tool for someone else to use, but not being familiar enough with the use cases to imagine and include all of the obvious useful features.</div><div><br /></div><div>Critical feedback is a nice thing! This pipeline might get some update posts of additional features that would be useful or current features that seem to be unnecessary.</div><div><br /></div><h3 id="step3" style="text-align: left;">Step 3: Recolor image to match thread colors that actually exist</h3><div>Paint.Net's posterize function tries to find a palette that closest-matches the current image, subject to your specified number-of-colors restriction. It won't necessarily use colors that actually exist in thread (some programs' posterize tools let you specify a list of colors, in which case you've already done this step). For this, you will appreciate applying your changes in a different layer so you can see which sections of the image have been recolored by toggling layer visibility.</div><div><br /></div><div>This step makes heavy use of the Magic Wand tool, which selects areas of an image based on color. When you click on a pixel with this tool, it will select all other pixels (we are using Global mode; you can also use it in Contiguous mode to only select neighbors) that are similar in color based on a threshold value. The threshold value is the key variable: below are two selections of black pixels (shown as red here for contrast) with threshold values set to 30 and 60, respectively.</div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpFergbDFxDwAUgsyh5_h9F8wBU57Xk9-oVtIpEtotvBVp4tAvJOMeCdaW8UbP9jXn_2PXs8R2sdeOSR7l4B9V0eyNa8jE_T0bwEyfC1MRY0tezRIT2JccFTBmcc4w_M4tkSokUFqpFGCS/s2048/painting_magicwand_black30.JPG" style="margin-left: auto; margin-right: auto;"><img alt="Painting with black pixels selected, but much of the dark shadows in the forearm and hand are unselected despite appearing black to the eye" border="0" data-original-height="1627" data-original-width="2048" height="508" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpFergbDFxDwAUgsyh5_h9F8wBU57Xk9-oVtIpEtotvBVp4tAvJOMeCdaW8UbP9jXn_2PXs8R2sdeOSR7l4B9V0eyNa8jE_T0bwEyfC1MRY0tezRIT2JccFTBmcc4w_M4tkSokUFqpFGCS/w640-h508/painting_magicwand_black30.JPG" title="Painting with black pixels selected, but much of the dark shadows in the forearm and hand are unselected despite appearing black to the eye" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">A threshold value of 30 misses many pixels that should be colored black</td></tr></tbody></table><div><br /><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAOI3gafR-m6XtDJdQx1sOZfBmuJyEP4MeI-c7O088EaBjVHbppLoWbiRvyyQlgmoXKDj-vTybLG-11XNe7uP6ZsTrGHtj8hT_PoMWvguu4rIkWA61mTzloG-WkmYQLUpmp2KcY0xcvzrt/s2048/painting_magicwand_black60.JPG" style="margin-left: auto; margin-right: auto;"><img alt="Painting with black pixels selected, but selection includes pixels that are colored medium-purple, green, and blue" border="0" data-original-height="1667" data-original-width="2048" height="521" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAOI3gafR-m6XtDJdQx1sOZfBmuJyEP4MeI-c7O088EaBjVHbppLoWbiRvyyQlgmoXKDj-vTybLG-11XNe7uP6ZsTrGHtj8hT_PoMWvguu4rIkWA61mTzloG-WkmYQLUpmp2KcY0xcvzrt/w640-h521/painting_magicwand_black60.JPG" title="Painting with black pixels selected, but selection includes pixels that are colored medium-purple, green, and blue" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">A threshold value of 60 nearly wipes out the purple-blue color gradients</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">Most of your threshold values will be in the 10 to 40 range, depending on how subtle your desired coloring is. Again, learn to love the Undo feature.</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">Once you have a selection boundary, you can recolor it (Paint Bucket or Fill tool, again with a Global setting). In particular, you can specify the new color using a Hex code that you extracted from a thread picker database.</div><div class="separator" style="clear: both; text-align: center;"><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmexH1UHBEWkMoPDAO56rFmVpbJOMmAF6hAcVMeHXm65wRSEeeyaCzZRjDX7tZJFqPLbcNhGADusj4W0ovaEaSWqFR5w4IokQPn4K3lEAHoGnUX5gBJHORSGqUi9GDSpm86KZVeMpkwN70/s697/color_selection_menu.JPG" style="margin-left: auto; margin-right: auto;"><img alt="A color menu screen featuring a row of saved colors (palette), a color wheel with white in the center and a saturated rainbow at the edge, sliders for RGB and HSV-alpha, and a text box for entering a Hex color code" border="0" data-original-height="541" data-original-width="697" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjmexH1UHBEWkMoPDAO56rFmVpbJOMmAF6hAcVMeHXm65wRSEeeyaCzZRjDX7tZJFqPLbcNhGADusj4W0ovaEaSWqFR5w4IokQPn4K3lEAHoGnUX5gBJHORSGqUi9GDSpm86KZVeMpkwN70/w400-h311/color_selection_menu.JPG" title="A color menu screen featuring a row of saved colors (palette), a color wheel with white in the center and a saturated rainbow at the edge, sliders for RGB and HSV-alpha, and a text box for entering a Hex color code" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Most programs allow you to select a color by colorwheel, RGB, Hex, and HSV</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">This step can be a pain, but it does guarantee you full control over color selection and colorblock contours. If preserving graininess doesn't matter, you can handwave away much of this and just let your (or your patternmaker's) brain interpolate reasonable color boundaries.</div><div class="separator" style="clear: both; text-align: center;"><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBjF3MbBVLK0BVxH3mlkhBHtfim0UnxezW57Sif3Wj8OKBs2YXQSB9wAtaTnn7E3EskmW5GsIUr017WAY7m6BF86wCTceTi3r388Uel70wyL7DubvwsSUaxDK_H_xC3iGoaZ9gjs1u9sX6/s1836/painting_magicwand_recolor.JPG" style="margin-left: auto; margin-right: auto;"><img alt="recolored Watercolor Painting using user-selected color palette" border="0" data-original-height="1832" data-original-width="1836" height="639" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBjF3MbBVLK0BVxH3mlkhBHtfim0UnxezW57Sif3Wj8OKBs2YXQSB9wAtaTnn7E3EskmW5GsIUr017WAY7m6BF86wCTceTi3r388Uel70wyL7DubvwsSUaxDK_H_xC3iGoaZ9gjs1u9sX6/w640-h639/painting_magicwand_recolor.JPG" title="recolored Watercolor Painting using user-selected color palette" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Can you spot the differences between the posterized version and the recolored version?</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheCKzPfbp5bjl9MQEmwfiossZ-I39cZfQ6gMhEAEDT0_mJN8hYp2xDXvN6TiZ2vlnBOUoXMxr89uQd2nbf0Ae_4LKpdpl6FhMSO6tixxh2-Moz31d9yFS8rEMAos4z-OBGHHYnhHwMOC4W/s348/painting_palette.JPG" style="margin-left: auto; margin-right: auto;"><img alt="16 colors used in Watercolor Painting. Black/white, 2 purples, 5 blues, 2 yellows, 5 greens." border="0" data-original-height="36" data-original-width="348" height="41" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheCKzPfbp5bjl9MQEmwfiossZ-I39cZfQ6gMhEAEDT0_mJN8hYp2xDXvN6TiZ2vlnBOUoXMxr89uQd2nbf0Ae_4LKpdpl6FhMSO6tixxh2-Moz31d9yFS8rEMAos4z-OBGHHYnhHwMOC4W/w400-h41/painting_palette.JPG" title="16 colors used in Watercolor Painting. Black/white, 2 purples, 5 blues, 2 yellows, 5 greens." width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Color palette used for all pixels in final Watercolor Painting pixel-art</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><div>We're done! Remember to send screenshots and not direct copies of your pixel-art, as compression outside of your image-editing software will make a zoomed out version of your 150 x 150 pixel image look very blurry. However, you should also remember to save your working-copy as-is, since any future changes on a not-downsampled image will be difficult.</div><div><br /></div><h3 id="step4" style="text-align: left;">Step 4: Extra quality-of-life things like toggling grids and rulers, landmark lines</h3><div>Paint.Net's default toolbar includes toggles for viewing the XY side-rulers and pixel gridlines. Usually the gridlines are useful, but if you wanted to port your image to a cross-stitch pattern generator (ours used <a href="https://kde.org/applications/graphics/org.kde.kxstitch" rel="nofollow" target="_blank">KXStitch</a> for Linux, but <a href="https://lordlibidan.com/best-cross-stitch-pattern-software/" rel="nofollow" target="_blank">there are others</a>) the gridlines are likely to cause unwanted image artifacts.</div><div><br /></div><div>I also didn't anticipate that the sewer would want to see the side rulers once given a pixel-gridlined PDF, but in retrospect this is an obvious feature to include when you're sending complicated digital images to someone. </div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNTP4EVau4oIY6Ouh147fD7K9Uvzg8q50cEIWb02DzkunMTDlfqXIwmh5KoFYaowW8myhO80VD4c0gD81kHBP2EihxuysJM98orV1oBgZifPEdBejkmSjvyB9xfP9AcHDXdkfaLWdVQ3B3/s1852/painting_nogrid.JPG" style="margin-left: auto; margin-right: auto;"><img alt="Watercolor Painting image without the thin grey grid overlay outlining each pixel" border="0" data-original-height="1844" data-original-width="1852" height="637" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNTP4EVau4oIY6Ouh147fD7K9Uvzg8q50cEIWb02DzkunMTDlfqXIwmh5KoFYaowW8myhO80VD4c0gD81kHBP2EihxuysJM98orV1oBgZifPEdBejkmSjvyB9xfP9AcHDXdkfaLWdVQ3B3/w640-h637/painting_nogrid.JPG" title="Watercolor Painting image without the thin grey grid overlay outlining each pixel" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Watercolor painting with rulers, minus pixel grid</td></tr></tbody></table><div><br /></div><div>It also would be useful to include midpoint lines in a contrasting color (for your sanity, put this in a separate layer from the art) and other landmarks as needed.</div><div><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUZS1oOO3Shn613AtwX_KuOuw67Smeo4IcKVMonveRightPVHdNWkX9eHIv07t8vb8WXnDTD6Me_21nuXNhH1cdxEqRHutou7TSwRVaq7cbUSmeRQ4naOvdSpKl06km_yCMRCpfxAp89rv/s1952/painting_landmarklines.JPG" style="margin-left: auto; margin-right: auto;"><img alt="Watercolor Painting with a horizontal and vertical red line marking the midpoints of the image" border="0" data-original-height="1952" data-original-width="1851" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUZS1oOO3Shn613AtwX_KuOuw67Smeo4IcKVMonveRightPVHdNWkX9eHIv07t8vb8WXnDTD6Me_21nuXNhH1cdxEqRHutou7TSwRVaq7cbUSmeRQ4naOvdSpKl06km_yCMRCpfxAp89rv/w607-h640/painting_landmarklines.JPG" title="Watercolor Painting with a horizontal and vertical red line marking the midpoints of the image" width="607" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Watercolor painting with ruler and red midpoint-landmark lines</td></tr></tbody></table><div><br /></div><p></p></div>Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-2987167675310585652020-08-08T20:45:00.006-04:002020-08-25T19:32:24.870-04:00Whale Blackwork PatternI've been working on some digital art!<div>This is intended to be a 12"x12" pattern (25 dpi) for blackwork, an embroidery technique that accomplishes neat shading effects with variations in fill pattern and line weight.</div><div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgWtGXrpkXkJsW8TfilsHWX4M2sY7D8Ymm5Gu5CLTm3UHqTkjyuYDhLwnTmjBb61xy-s0jsypQPvC7vuYwN0xlUdtaqwgXMmmtypp4mOBt-KoINBQfTG65DmTJ4jL2cEg0c1xPb0tWNJZd/s2048/whale.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="Embroidery pattern depicting a whale and fish" border="0" data-original-height="2048" data-original-width="2048" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgWtGXrpkXkJsW8TfilsHWX4M2sY7D8Ymm5Gu5CLTm3UHqTkjyuYDhLwnTmjBb61xy-s0jsypQPvC7vuYwN0xlUdtaqwgXMmmtypp4mOBt-KoINBQfTG65DmTJ4jL2cEg0c1xPb0tWNJZd/w640-h640/whale.jpg" title="Embroidery pattern depicting a whale and fish" width="640" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;"><span><a name='more'></a></span>The intricate, repeating designs lend themselves well to lasso-selection and tessellation functions present in most graphics editing software. I used Paint.NET and aligned patterns to a grid by eye, but these could easily be procedurally generated. There's some <a href="https://computationalcreativity.net/iccc2017/CCW/CCW2017_paper_2.pdf" target="_blank">interesting academic literature on the topic</a>.</div><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9_t5pKoINTkGJzblemibIKVrdBqtxmdYpzX3U365GpUXOGSte4yFmm3UkTMVGiPf9SzuLPqsBfXa58IML6VVKIO_CotkpOBI0JMAvu7-3HkGQSh8UltCAv9qaD46s0vKILF946tSYhJYx/s2048/whale_closeup2.JPG" style="display: block; margin-left: 1em; margin-right: 1em; padding: 1em 0px; text-align: center;"><img alt="close up image of tail that shows shading effects from variations in fill pattern" border="0" data-original-height="1098" data-original-width="2048" height="343" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh9_t5pKoINTkGJzblemibIKVrdBqtxmdYpzX3U365GpUXOGSte4yFmm3UkTMVGiPf9SzuLPqsBfXa58IML6VVKIO_CotkpOBI0JMAvu7-3HkGQSh8UltCAv9qaD46s0vKILF946tSYhJYx/w640-h343/whale_closeup2.JPG" title="close up image of tail that shows shading effects from variations in fill pattern" width="640" /></a></div><div class="separator" style="clear: both; text-align: left;">For the tail and flipper, I used a single geometric motif and added or removed elements to change visual density.</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbQLyUJOe2lxXWAga63zEqMX5_yw3K96Zcrq_pcDMd8CabNN7eIM25VQ6xhDPrdkvIOljN5iYw_GRAW8i6mqtEdqrZ2SYim3k9IvFskNlZ5jbZt9RvVCmXCN8Yolpkxx7p1NSeE4gSHyh5/s357/motif.jpg" style="display: block; margin-left: auto; margin-right: auto; padding: 1em 0px;"><img alt="Image of a geometric pattern that increases in complexity and shading from left to right" border="0" data-original-height="117" data-original-width="357" height="131" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbQLyUJOe2lxXWAga63zEqMX5_yw3K96Zcrq_pcDMd8CabNN7eIM25VQ6xhDPrdkvIOljN5iYw_GRAW8i6mqtEdqrZ2SYim3k9IvFskNlZ5jbZt9RvVCmXCN8Yolpkxx7p1NSeE4gSHyh5/w400-h131/motif.jpg" title="Image of a geometric pattern that increases in complexity and shading from left to right" width="400" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Motif and variations used in tail and flipper<br /></td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">For the main body, I used a rigging pattern in a foreground layer and varied elements in the background. This made blending styles between tail and body a bit easier, although the process also created some invalid line intersections that I had to manually clean afterwards.</div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcxnC9URi1FgW6YNgy4dNHEvf6qFz9roVgUbqDEd1DsbercSMroQCy3Fm_vWAsK3TqLnYqepNmq3E8dOxvBpQvm2RCScn4T79GmQreOEILlK2NtuXcWhn2_7QSJwryg5q6b-vIDZML8oi7/s700/motif2.jpg" style="display: block; margin-left: auto; margin-right: auto; padding: 1em 0px;"><img alt="Image of a geometric pattern with increasingly dense background patterns from left to right" border="0" data-original-height="140" data-original-width="700" height="128" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcxnC9URi1FgW6YNgy4dNHEvf6qFz9roVgUbqDEd1DsbercSMroQCy3Fm_vWAsK3TqLnYqepNmq3E8dOxvBpQvm2RCScn4T79GmQreOEILlK2NtuXcWhn2_7QSJwryg5q6b-vIDZML8oi7/w640-h128/motif2.jpg" title="Image of a geometric pattern with increasingly dense background patterns from left to right" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Rigging motif and main background variations used in whale body</td></tr></tbody></table><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: left;">The eye pupil uses a uniformly-dense fill pattern in a relative swath of negative space to provide a focal point, although it does not register as "dark" as the tail or the star-shaped intersections on the back. The eyebrow uses long swaths of single lines (a rarity here) to get visual interest. </div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">In general, I found it difficult to guess <i>a priori </i>which patterns would strongly contrast versus blend nicely. The waves-under-the-netting at the belly took a few tries to get a vertical offset that didn't completely disappear behind the knots. I also had to delete a bunch of horizontal and vertical lines where this motif is used at the upper section of the whale head (compare with the back section of the body moving towards the tail) to avoid creating complete asterisks, which draw the eye away from the flipper and eye.</div><div class="separator" style="clear: both; text-align: left;"><br /></div><table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto;"><tbody><tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFTBEWgQvAflP06Jxuv1-2zlt0Ew8eSLaO1PKBFTg44FsmUlSzGK8FGFS11aDFLBXyn7SCp5i-GpJxxJc1thFwrfEDxUnwj_jSe36kEzQ9J6rO8Vs804NKzsysjUwyYI8zcohjHklTCdvj/s400/whale_closeup3.JPG" style="display: block; margin-left: auto; margin-right: auto; padding: 1em 0px;"><img alt="Image comparing body and eye pattern densities" border="0" data-original-height="132" data-original-width="400" height="211" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFTBEWgQvAflP06Jxuv1-2zlt0Ew8eSLaO1PKBFTg44FsmUlSzGK8FGFS11aDFLBXyn7SCp5i-GpJxxJc1thFwrfEDxUnwj_jSe36kEzQ9J6rO8Vs804NKzsysjUwyYI8zcohjHklTCdvj/w640-h211/whale_closeup3.JPG" title="Image comparing body and eye pattern densities" width="640" /></a></td></tr><tr><td class="tr-caption" style="text-align: center;">Asterisk-intersections (left) used on the caudal section don't seem like they would conflict close to the eye (right) when zoomed in, but end up making contrasting dark pixels from zoomed out.</td></tr></tbody></table><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">I was particularly happy about the subtle weave where the body's and jaw's rigging patterns meet. Looking back on it, some of the intersections need a bit more thickness where the ropes bend around each other. I also missed cleaning up some of the diagonals on the teeth that don't quite reach a grid vertex. Oops.</div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKnM_w65JGaPKQxwROcMuqZQRvob9BbHDmlo-YQqQSaXnFiuI9LSHUeFfX1zqoFEt24-hS6bn_XvtF2Ef4qobgbQhjmiERQwNri_Q4LL3GqV3QeYVwtrM8UDeDx7WgAgT3pZf7fUvBk3mp/s2048/whale_closeup1.JPG" style="display: block; margin-left: 1em; margin-right: 1em; padding: 1em 0px; text-align: center;"><img alt="close up of the eye and mouth area of whale pattern" border="0" data-original-height="1112" data-original-width="2048" height="348" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKnM_w65JGaPKQxwROcMuqZQRvob9BbHDmlo-YQqQSaXnFiuI9LSHUeFfX1zqoFEt24-hS6bn_XvtF2Ef4qobgbQhjmiERQwNri_Q4LL3GqV3QeYVwtrM8UDeDx7WgAgT3pZf7fUvBk3mp/w640-h348/whale_closeup1.JPG" title="close up of the eye and mouth area of whale pattern" width="640" /></a></div><div class="separator" style="clear: both; text-align: left;">This art style is really cool and provides a lot of space to embed fun thematic easter eggs (the challenge for this project was to have mostly nautical fill patterns), so I'll definitely play around with this more. I would spend more effort finding or making a snap-to-user-defined-grid function before doing another large piece like this, though.</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">Whale!</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">--</div><div class="separator" style="clear: both; text-align: left;">None of these fill patterns are mine. (minus basic things like the pupil and some shading variations)</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">Most of the constituent motifs come from <a href="https://string-or-nothing.com/2011/06/25/ensamplario-atlantio-blackwork-filling-collection-pdfs-for-download/" target="_blank">Kim Brody Salazar's <i>Ensamplario Atlantio vol I</i></a> (the background fish and one of the geometric fills are<a href="https://string-or-nothing.com/2020/01/15/ensamplario-atlantio-ii/" target="_blank"> derived from vol II</a>), where her blog was also a fantastic resource for understanding what sewers expect from a needlework chart.</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">The eyebrow comes from <a href="https://www.vectorstock.com/royalty-free-vector/seamless-wave-pattern-vector-526009" target="_blank">paul_june's seamless-wave-pattern-vector</a> and was modified to fit grid constraints.</div><div class="separator" style="clear: both; text-align: left;"><br /></div><div class="separator" style="clear: both; text-align: left;">The overall whale design is a riff off of <a href="https://www.etsy.com/listing/548056144/complete-embroidery-kit-deep-dive-whale" target="_blank">HookLineTinker's "Deep Dive"</a>. </div></div>Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com2tag:blogger.com,1999:blog-5736103898080682832.post-1302768820935103972019-03-09T22:40:00.002-05:002020-08-25T19:33:09.709-04:00Ava Up and Running (and especially climbing!)<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihAomjY-M9vB2bMVNsAa0Zi1hJMsocPWA17hxgPiuxTRtK2kZc8PFJMF9Xjmu1bfHj5UM_pA8mejGC4Nx27Km92yFohbJe74HQ1ht4IPkA4RfN9lLOvPrs8VDdx-hUWuR01QJY-3YqjVAM/s1600/20190309_124939.jpg" style="display: inline; margin-left: 1em; margin-right: 1em; text-align: center;"><img alt="photo showing bare feet and climbing shoes" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEihAomjY-M9vB2bMVNsAa0Zi1hJMsocPWA17hxgPiuxTRtK2kZc8PFJMF9Xjmu1bfHj5UM_pA8mejGC4Nx27Km92yFohbJe74HQ1ht4IPkA4RfN9lLOvPrs8VDdx-hUWuR01QJY-3YqjVAM/w640-h480/20190309_124939.jpg" title="photo showing bare feet and climbing shoes" width="640" /></a></div>
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<span><a name='more'></a></span>I CAN CLIMB NOW!!!!!!!!!!!!! I sat at my computer for a few minutes trying to find the right words to capture the emotion I have when saying this, but it's really just this simple. I now have what I've been working towards for the past 18 m<span style="font-family: inherit;">onths <span style="background-color: white; color: #222222;">— a body strong* and coordinated enough that I can focus on footwork and balance, rather than "will my leg collapse in this position" or "will I hurt myself." </span></span><br />
<span style="background-color: white; color: #222222;">*<span style="font-size: x-small;">(still have to wear a brace on the wall)</span></span><br />
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Let's recap:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFd6uKolrv9vzuxTbhLO3pr6ekDHL9_ywr81jjQaPfFGZkkI4FzgEhy_tV70Wt-Poivqerg63PKNM6KW6QhYWVi_dDt851TCeCIuzBKX_o2f3_3z0nPwIucd2u9y09GnkGp1ADKpc_eEw3/s1600/image-20170827_132205.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="photo showing a swollen left leg and unaffected right leg" border="0" data-original-height="1311" data-original-width="1600" height="326" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFd6uKolrv9vzuxTbhLO3pr6ekDHL9_ywr81jjQaPfFGZkkI4FzgEhy_tV70Wt-Poivqerg63PKNM6KW6QhYWVi_dDt851TCeCIuzBKX_o2f3_3z0nPwIucd2u9y09GnkGp1ADKpc_eEw3/w400-h326/image-20170827_132205.jpg" title="photo showing a swollen left leg and unaffected right leg" width="400" /></a></div>
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8/20/2017</div>
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T +2 days</div>
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This is when I was wishfully hoping I had just sprained my knee.<br />Then I learned I would need two surgeries and a whole lot of work.</div>
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<a href="https://i.imgur.com/l3h4szt.gif" style="margin-left: 1em; margin-right: 1em;"><img alt="video clip of the author taking small walking steps" border="0" height="400" src="https://i.imgur.com/l3h4szt.gif" title="video clip of the author taking small walking steps" width="350" /></a></div>
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8/29/2017</div>
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T +10 days</div>
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Relearning how to walk! </div>
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<br /><a href="https://i.imgur.com/MM5veyL.gif" style="margin-left: 1em; margin-right: 1em;"><img alt="video clip of the author jogging but swinging her arms as if preparing for a sprint" border="0" height="321" jogging="" src="https://i.imgur.com/MM5veyL.gif" title="video clip of the author jogging but swinging her arms as if preparing for a sprint" width="400" /></a></div>
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9/03/2018</div>
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T + 1 year</div>
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Really derpy running; the muscle power's there but I can't move my legs fast enough to actually run.</div>
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<a href="https://i.imgur.com/4IHUHde.gif" style="margin-left: 1em; margin-right: 1em;"><img alt="video clip of the author running a short distance" border="0" data-original-height="284" data-original-width="450" height="250" src="https://i.imgur.com/4IHUHde.gif" title="video clip of the author running a short distance" width="400" /></a></div>
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3/09/2019</div>
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T + 1.5 years</div>
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Gonna start working on that 10min mile.</div>
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I still have a long way to go before graduating from PT and being completely back in shape <span style="background-color: white; color: #222222;">— and</span><span style="background-color: white; color: #222222;"> fending off arthritis and strengthening my leg will be a lifelong project </span><span style="background-color: white; color: #222222;">— but I'm excited about the progress I've made. My list of "things I can't do yet" is getting smaller and smaller each month (trying to get approval for pivoting/cutting sports like frisbee and skiing next) and I'm ready to be outside doing things!</span></div>
<span><!--more--></span><span><!--more--></span><span><!--more--></span>Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com1tag:blogger.com,1999:blog-5736103898080682832.post-45393988488927079682018-11-25T23:41:00.001-05:002020-08-10T22:44:21.925-04:00How Jumping Spiders Jump<div style="text-align: center;">
<iframe title="Jumping Spider Talk Video Recording" allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture" allowfullscreen="" frameborder="0" height="315" src="https://www.youtube.com/embed/_Tu41CK9g14" width="560"></iframe><br />
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I gave a talk at CEE's 35 Anniversary conference about some of my current research in the Shamble Lab - our current understanding of how jumping spiders jump, and how we set up the simulations and physical experiments to figure that out.</div>
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PS: I am RSI '12, but I'm not / never was a software engineer at Two Sigma. </div>
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Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-49059295896704102672018-06-23T18:16:00.005-04:002020-08-25T19:33:39.674-04:00leg reconstruction<div class="separator" style="clear: both; text-align: left;">
Hey! It's been a while, so I'm here with a different kind of post. It's now been 5 months since my surgery and 10 months since I wrecked my leg (8/18 accident, 10/6 first surgery, 1/23 final reconstruction), and this post is on how a bunch of doctors (and my biology!) made me a new leg.</div><span><a name='more'></a></span><div class="separator" style="clear: both; text-align: left;"><br /></div>
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<b>Note for squeamish people : basically every photo after this is a bruised or stitched-up or otherwise wrecked leg.</b> I have the more 'scary' surgery photos hidden behind a spoiler button, but skip this post if medical photos make you uncomfortable.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiqP3MXv4p5FAJyJBbCbx6oHJCMyA5cPGwdwiU61oPA16RsWi04nAwhwRwge17wiAlDD9XwnwN8DLeHB1ZmQaPmkkPnJkLjETbt00hCl76SAfriLelI9Ga9Sa-2_dMjvznZ2ZzBUd6HWmhs/s1600/20171001_150013.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo showing sign from the perspective of the author's line of sight" border="0" data-original-height="1600" data-original-width="1535" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiqP3MXv4p5FAJyJBbCbx6oHJCMyA5cPGwdwiU61oPA16RsWi04nAwhwRwge17wiAlDD9XwnwN8DLeHB1ZmQaPmkkPnJkLjETbt00hCl76SAfriLelI9Ga9Sa-2_dMjvznZ2ZzBUd6HWmhs/w382-h400/20171001_150013.jpg" title="photo showing sign from the perspective of the author's line of sight" width="382" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">It turns out all the accessible-route signs are above eye height if you're on crutches. It's probably even more out-of-sight if you were in a wheelchair.</td></tr>
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So 10 months ago I fell off a bouldering wall at the gym. I hit the mattress with my left knee at a funny angle and heard a loud pop on impact (the same as when you open a sealed jar). I immediately knew I fucked up, even though it didn't hurt that much. To my surprise, I could walk on the leg so I hoped it might've just been a sprain. And x-rays from urgent care the day after showed nothing broken, so the doctor also thought it probably wasn't a big deal (they gave me a brace and told me to go ahead and walk on it)</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjhJ4qMAjR7J-61oWJHws9GBmI-trXhcbc16C0wHDabQ5wRquvLenmKh1ns4vlu2G7poPpzmW701rZ9I4OBzrafYmPZWK8KwSi6OJgRaSSyDO-KlbKEPUx8lQlV5-Besf_Kr5b5RXZ9FvG/s1600/image-20170827_132205.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo showing a swollen left leg and unaffected right leg" border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjhJ4qMAjR7J-61oWJHws9GBmI-trXhcbc16C0wHDabQ5wRquvLenmKh1ns4vlu2G7poPpzmW701rZ9I4OBzrafYmPZWK8KwSi6OJgRaSSyDO-KlbKEPUx8lQlV5-Besf_Kr5b5RXZ9FvG/w400-h300/image-20170827_132205.jpg" title="photo showing a swollen left leg and unaffected right leg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Left leg super swollen compared to right</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwAwoJeVwHfeAlylVdiPZ5yldbBfwpx2-jUVj8MDTB-7DuviuJXRe6PlMYGTOQMkAFLp8zkPvaaGycHNWDQ-wuLqCIR-IXmNxVxIEemjpM6EMzGaGah5s2QlElsCMb3OoG8TeQWrwA-h1u/s1600/image-20170823_184611.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo showing swollen leg with deep purple coloring around the knee crease" border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwAwoJeVwHfeAlylVdiPZ5yldbBfwpx2-jUVj8MDTB-7DuviuJXRe6PlMYGTOQMkAFLp8zkPvaaGycHNWDQ-wuLqCIR-IXmNxVxIEemjpM6EMzGaGah5s2QlElsCMb3OoG8TeQWrwA-h1u/w300-h400/image-20170823_184611.jpg" title="photo showing swollen leg with deep purple coloring around the knee crease" width="300" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Bruising underneath the knee</td></tr>
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Of course when I got the MRI results back, it was pretty clear I actually wrecked everything. The two major things were completely tearing an ACL and more importantly tearing half of my patellar tendon.<br />
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The MRI scans are really cool, too. If you haven't gotten an MRI before, you (the patient) can request a CD loaded with software to flip through axial, frontal, and side views (MRIs come in stacks of image slices). I also used <a href="http://www.radiologyassistant.nl/en/p42764e8fe927e/knee-non-meniscal-pathology.html" target="_blank">this great website</a> to compare my images to both healthy and injured knees.<br />
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<b>Note: I am not a doctor. I backsolved knowing the radiologist's report and after being told exactly how/what/where was broken. Don't make armchair diagnoses without a medical degree.</b><br />
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</b> Some quick MRI facts: My images are T2 weighted, so hydrated things appear lighter. Air is very dark. Muscles are supposed to be a neutral gray, and tendons are very dark. Fat is super bright.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEieXpjBj7D50t-rgTp9m24lQKZr5UccEMlWlOQGJ2fJhlzDtkBFBHls1ny_Yb2IE_QySK7Rp5lYG3ND18NxZhfuGTavPFKGqACuQDSm68iZfZG_MGzDY8Oscfxqsc9HFqs5j3j-otK8KHp0/s1600/knee-tendons-ligaments.jpg" style="margin-left: auto; margin-right: auto;"><img alt="labeled diagram of ligaments and bone features of the knee" border="0" data-original-height="564" data-original-width="700" height="321" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEieXpjBj7D50t-rgTp9m24lQKZr5UccEMlWlOQGJ2fJhlzDtkBFBHls1ny_Yb2IE_QySK7Rp5lYG3ND18NxZhfuGTavPFKGqACuQDSm68iZfZG_MGzDY8Oscfxqsc9HFqs5j3j-otK8KHp0/w400-h321/knee-tendons-ligaments.jpg" title="labeled diagram of ligaments and bone features of the knee" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Quick cheat sheet on knee anatomy<br />
<a href="https://www.healthpages.org/health-a-z/knee-pain-symptoms-causes-treatment/" target="_blank">(from www.healthpages.com)</a></td></tr>
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Focusing first on the ACL - this is one of the ligaments that runs diagonally inside the knee joint. It keeps the tibia bone from sliding in front of the femur, and is important for rotational stability.<br />
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On the left is a side view of the knee and on the right is the location of that image slice in frontal view. The normal ACL runs through a notch in the femur and connects to the upper bone at the back. There's... not supposed to be an air gap. (green circle)<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgspHuzeATIseC59znoX2u4yhpmjthfxN1MGa-QSKNZcJw9vXcmpUwaTBzoXMMs-PGuEy7FbqWZ5GvI3Zx3-8USUQam1NeILJieqes1mbC6nFxHlg-OPFyw3bFmzfvVleOxyK9bzcLo8rl6/s1600/acl_tear_annotated.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="MRI image of knee with a discontinuity at the ACL" border="0" data-original-height="358" data-original-width="1600" height="344" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgspHuzeATIseC59znoX2u4yhpmjthfxN1MGa-QSKNZcJw9vXcmpUwaTBzoXMMs-PGuEy7FbqWZ5GvI3Zx3-8USUQam1NeILJieqes1mbC6nFxHlg-OPFyw3bFmzfvVleOxyK9bzcLo8rl6/w1536-h344/acl_tear_annotated.jpg" title="MRI image of knee with a discontinuity at the ACL" width="1536" /></a></div>
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If there's an air gap then that means the ACL is completely torn and retracted (think broken rubber band) somewhere. I backed up a few slices and found it curled against itself.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_Ac6yauS83tB5NhNdmz6p8pCnSEDmbNWUC1hfWwfUz955Q3wEsIISroDgy_zPjdZB6QQ08xgqzTWo3XelI7n25Oe9e1m7Arfcoq4L5nUgq9jWN18pOUUJ8qrZLVU7goY3krd2S-w9pbki/s1600/acl_annotated.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="MRI image of knee with a curled piece of soft tissue in front of the bone" border="0" data-original-height="717" data-original-width="1600" height="367" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_Ac6yauS83tB5NhNdmz6p8pCnSEDmbNWUC1hfWwfUz955Q3wEsIISroDgy_zPjdZB6QQ08xgqzTWo3XelI7n25Oe9e1m7Arfcoq4L5nUgq9jWN18pOUUJ8qrZLVU7goY3krd2S-w9pbki/w819-h367/acl_annotated.jpg" title="MRI image of knee with a curled piece of soft tissue in front of the bone" width="819" /></a></div>
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The other major injury was the patellar tendon. The patellar tendon below the kneecap and the quadriceps tendon above work to extend the leg. My fall partially tore it (transverse tear, like opening a sideways zipper)<br />
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Below is what the tendons should look like - completely black, solid strips.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEietMMtlTSviXlPEr7homRBRhY0EN3cHRV9hnocyC1OudBgy6zAdaFa_QdNGPN2UIbF9fzkDEZnYL3b4YsTN4RQHF9FVC88rLk1JFf9Yb7TCDXqZ9O_u36_kZov7yJDLXnjO9VIhs19VZ3y/s1600/patellar_fine_1_annotated.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="MRI image showing faint taut lines of soft tissue" border="0" data-original-height="728" data-original-width="1600" height="298" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEietMMtlTSviXlPEr7homRBRhY0EN3cHRV9hnocyC1OudBgy6zAdaFa_QdNGPN2UIbF9fzkDEZnYL3b4YsTN4RQHF9FVC88rLk1JFf9Yb7TCDXqZ9O_u36_kZov7yJDLXnjO9VIhs19VZ3y/w655-h298/patellar_fine_1_annotated.jpg" title="MRI image showing faint taut lines of soft tissue" width="655" /></a></div>
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And here's the broken side. Compared to the intact quadriceps tendon, the patellar tendon here looks frayed (because it is!)<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQoikQRY3P43L2Ow4b0bi21fqMen4qB665T55fKQIQAHKImkbNj8NRi7uQtKvatdQ0xUJgLvl_r4cSvKVVvCzWNnuefNO6eUbabKVuWCFhcwdIJwsCw8gXjCNZzD64R2ImyXciamS9R25w/s1600/patellar_torn_1_annotated.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="MRI image showing squiggly loose soft tissue where a taut tendon line should be" border="0" data-original-height="717" data-original-width="1600" height="366" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQoikQRY3P43L2Ow4b0bi21fqMen4qB665T55fKQIQAHKImkbNj8NRi7uQtKvatdQ0xUJgLvl_r4cSvKVVvCzWNnuefNO6eUbabKVuWCFhcwdIJwsCw8gXjCNZzD64R2ImyXciamS9R25w/w819-h366/patellar_torn_1_annotated.jpg" title="MRI image showing squiggly loose soft tissue where a taut tendon line should be" width="819" /></a></div>
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The patellar tendon is the more important injury, but its rehab interferes with ACL recovery. So, the first surgery just dealt with the patellar tendon and left the ACL alone. It's not like I would be running anytime soon anyway.<br />
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The surgeon grafted on a cadaver's tendon and sewed it to the intact part. Then we both let biology and PT take care of the rest.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNq11ndsUSgnc9fXyiuYxGmgeQJk9sQS_0MQAIo-Gfcj6ZDncX1uNtxdXTT3FOsCH-fJsYm342W-TTK-z04cm4NW7cAx0fna5jX_gte8MSM-ll3v5Nw9ujTO8I4DdUEucYlEVCbdmDTR3N/s1600/20170908_113459.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo of a very swollen and inflamed leg with a line of stitches" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNq11ndsUSgnc9fXyiuYxGmgeQJk9sQS_0MQAIo-Gfcj6ZDncX1uNtxdXTT3FOsCH-fJsYm342W-TTK-z04cm4NW7cAx0fna5jX_gte8MSM-ll3v5Nw9ujTO8I4DdUEucYlEVCbdmDTR3N/w360-h640/20170908_113459.jpg" title="photo of a very swollen and inflamed leg with a line of stitches" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">bandages came off 3 days post-surgery. Still very swollen.</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2aFXhlpJKeiLPkXYUKGtXotSLFVKA7fvZGEjGPLTgDfBzElFkvXayoj4hPfErOLAJZTaDp4eprI5GNMk86kUrFk9YjI3K3vBdqXY4beAU6mUZJcb20UIYhD0rpWK53kC33lOXx30wGEi-/s1600/20170910_104603.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo of a swollen non-inflamed leg next to the unaffected leg" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2aFXhlpJKeiLPkXYUKGtXotSLFVKA7fvZGEjGPLTgDfBzElFkvXayoj4hPfErOLAJZTaDp4eprI5GNMk86kUrFk9YjI3K3vBdqXY4beAU6mUZJcb20UIYhD0rpWK53kC33lOXx30wGEi-/w480-h640/20170910_104603.jpg" title="photo of a swollen non-inflamed leg next to the unaffected leg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">1 week. Swelling's down</td></tr>
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The first objective for PT was to regain range of motion, which took a few weeks.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjybmIOoql4Hta3RXE9hiErBJ2c7uMqkbne84eit31AKa6ovh8n8tI_fyJFreEJVoMobWji1XxGcHRho0aPjqUfyhW9AVX41jqhjcg4wR5q2-5kWZJmWpunKZ-0TIOx-SscxDWlIlS307Zc/s1600/image-20170918_142717.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo of a leg in a knee brace showing angle markings" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjybmIOoql4Hta3RXE9hiErBJ2c7uMqkbne84eit31AKa6ovh8n8tI_fyJFreEJVoMobWji1XxGcHRho0aPjqUfyhW9AVX41jqhjcg4wR5q2-5kWZJmWpunKZ-0TIOx-SscxDWlIlS307Zc/w480-h640/image-20170918_142717.jpg" title="photo of a leg in a knee brace showing angle markings" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Started off with only 20deg of flexion</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9WaEifY-Za9bHfgAOuzZmGm99ObZCF4qgrcrxk_1ixF910URK307c3MAqoXu0i7sW60Ja8WoXUqd4MTjoUL3IJPkAhzvOUL1L9az19rfkwqFMaeL0uyPJZ94JJZXeexfRGeLEXHjmTIdm/s1600/20170921_113442.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo of a leg in a knee brace showing angle markings" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9WaEifY-Za9bHfgAOuzZmGm99ObZCF4qgrcrxk_1ixF910URK307c3MAqoXu0i7sW60Ja8WoXUqd4MTjoUL3IJPkAhzvOUL1L9az19rfkwqFMaeL0uyPJZ94JJZXeexfRGeLEXHjmTIdm/w480-h640/20170921_113442.jpg" title="photo of a leg in a knee brace showing angle markings" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Quick progression 3 days later.<br />
Got full 130deg a month later (though right leg can get to 150deg)</td></tr>
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The second objective was to regain strength in the quad muscles. They atrophied while the leg was immobilized and I needed them to be strong enough to handle an ACL. (The stronger the muscles, the less stress placed on the ligaments and tendons)</div>
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An interesting discovery I made during rehab was how important re-training neural connections was to regaining control of my leg. The majority of the recovery felt like the scene from <i>Kill Bill </i>where she commands her toe to move:</div>
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<a href="https://media0.giphy.com/media/jShO5xcE9p4aY/giphy.gif" style="margin-left: 1em; margin-right: 1em;"><img alt="scene from movie Kill Bill with subtitle Wiggle Your Big Toe" border="0" data-original-height="206" data-original-width="500" height="262" src="https://media0.giphy.com/media/jShO5xcE9p4aY/giphy.gif" title="scene from movie Kill Bill with subtitle Wiggle Your Big Toe" width="640" /></a></div>
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I had regained most of my muscle strength early on, but there was a delay between commanding my muscle to move and the knee actually bending.</div>
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Human biology is really cool. My leg didn't really feel like an extension of my body until I got the attached neurons to properly work in concert. <a href="https://www.ted.com/talks/hugh_herr_how_we_ll_become_cyborgs_and_extend_human_potential" target="_blank">According to videos like this</a>, the same premise should apply when neurons seamlessly interact with inorganic muscles too.</div>
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Anyway, at the end of January I was deemed functional enough to get more parts. For this procedure, the surgeon opted to use an autograft (results in a stronger ligament but is a more invasive surgery) from my right (intact) knee.</div>
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(For anyone actually closely following this blog, yes I did fit two woodworking projects between the surgeries. Good deadline motivation!)</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEistG8ebbS7inEG0De3VQqDyqFkXndXeD4PFj39K1TANnNx6qwBM2YIILYPmEiX-RQFntp8s28F1uOitdd5czSD-v9e1Y5FXOd3uhsLNp3vdedKxXu5oeERdfMhpuS9lhhhRuwnbsNFUFCy/s1600/20170906_062855.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo of the author in a hospital bed" border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEistG8ebbS7inEG0De3VQqDyqFkXndXeD4PFj39K1TANnNx6qwBM2YIILYPmEiX-RQFntp8s28F1uOitdd5czSD-v9e1Y5FXOd3uhsLNp3vdedKxXu5oeERdfMhpuS9lhhhRuwnbsNFUFCy/w300-h400/20170906_062855.jpg" title="photo of the author in a hospital bed" width="300" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Me before getting new parts</td></tr>
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The ACL reconstruction is also really cool. Nearly all of it required just two small portals (I think they also reopened some of the previous incision scar since it was available)</div>
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<button>Spoiler: Surgery Scope Photos</button></div>
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Arthroscope images<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://www.blogger.com/IMAGE%20URL%20HERE" style="margin-left: auto; margin-right: auto;"><img alt="arthroscope snapshots showing soft tissue and cartilage" height="514" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpWdPKmMwHeo5Qn061y4hd3Q_lcJZmWwTQex1dgyEq_S8h8jPjS42RspLXof0-uNoKrSB_aBA7H1yDPR9wv6yFJHHEd-ZWsefM0XFtz8PFlnjVplFGKoKuvuY3I-3tB2s0d3q_V31U_rht/w640-h514/SCAN0001.jpg" style="border: none;" title="arthroscope snapshots showing soft tissue and cartilage" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Navigating to the femoral notch and finding the torn ACL and meniscus</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2SnX4rf7Nf-O-aEgPPxFahB_ugiYw65NVlt7rkuO9rZ91l9EnMt9bO4T-wGMgDFsv8ElOazkMr8zyLAjTC2lL4ASVq3xWsRhKCwI5Zrn3VlRjEL-o4iSdH0KwrhDukwMCgKQL9ALM0_Lw/s1600/SCAN0002.jpg" style="margin-left: auto; margin-right: auto;"><img alt="arthroscope snapshots showing a drill boring a hole through cartilage and bone" border="0" data-original-height="1276" data-original-width="1600" height="510" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2SnX4rf7Nf-O-aEgPPxFahB_ugiYw65NVlt7rkuO9rZ91l9EnMt9bO4T-wGMgDFsv8ElOazkMr8zyLAjTC2lL4ASVq3xWsRhKCwI5Zrn3VlRjEL-o4iSdH0KwrhDukwMCgKQL9ALM0_Lw/w640-h510/SCAN0002.jpg" title="arthroscope snapshots showing a drill boring a hole through cartilage and bone" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Drilling and reaming an access tunnel through the femur to pass the new graft through</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkVRIF4o1vXLok2KP6d5ARU9PytIY2ELefpnfO87BEPGpJEe8urwPncPBef_YnQTaUYMwTxe9h2lQZRt0bcFpZlfKynaW-CWgBQsM_aAVvC8jLSD-Qc9_TsoGKtw9gCUs1bHGqXC17poKD/s1600/SCAN0003.jpg" style="margin-left: auto; margin-right: auto;"><img alt="arthroscope snapshots showing a blue string and a drill tip" border="0" data-original-height="1279" data-original-width="1600" height="510" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkVRIF4o1vXLok2KP6d5ARU9PytIY2ELefpnfO87BEPGpJEe8urwPncPBef_YnQTaUYMwTxe9h2lQZRt0bcFpZlfKynaW-CWgBQsM_aAVvC8jLSD-Qc9_TsoGKtw9gCUs1bHGqXC17poKD/w640-h510/SCAN0003.jpg" title="arthroscope snapshots showing a blue string and a drill tip" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Feeding new graft (attached with blue thread) and drilling screw holes into femur and tibia.</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgJDUSFSxQWnofR227XK_S-PZ22QCrP6En16qwZTUFfXD1VtOnEzvF6EIxuh69WPIoFJaHH7W01K9LYTAFg0PWbrDWr_sNhwP6KA6_EmqBEfmh8EEbM9ZDbpEAKfAuqzkkqjP9TWcqWxO9/s1600/SCAN0004.jpg" style="margin-left: auto; margin-right: auto;"><img alt="arthroscope snapshots showing tap threads and tendon tissue" border="0" data-original-height="1287" data-original-width="1600" height="514" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgJDUSFSxQWnofR227XK_S-PZ22QCrP6En16qwZTUFfXD1VtOnEzvF6EIxuh69WPIoFJaHH7W01K9LYTAFg0PWbrDWr_sNhwP6KA6_EmqBEfmh8EEbM9ZDbpEAKfAuqzkkqjP9TWcqWxO9/w640-h514/SCAN0004.jpg" title="arthroscope snapshots showing tap threads and tendon tissue" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Tapping hole, adding screw eyelet, then attaching and tensioning new graft.</td></tr>
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And finally, here I am 5 months later!<br />
I've now been cleared to bike and go to the gym, and hopefully begin running, pivoting, and otherwise return to sports by the end of the year.<br />
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This is likely to be a perpetual in-progress project - not much is really known about what affects outcomes of major joint surgery. The evidence is both depressing (<a href="https://www.nytimes.com/2017/11/06/health/arthritis-risk-acl.html" target="_blank">high likelihoods of developing early-onset arthritis and other complications within 10 years</a>) and optimistic (<a href="https://kneesurgeryrecovery.com/blogs/news/new-study-suggests-first-year-rehab-is-key-after-acl-surgery" target="_blank">aggressive first-year rehab is key</a>)<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidMVKgP434VYQsD64BjDBFLK7KNNm4vb3xXHbE9xnQlT0yvL4kOoS24UhYOBAwMkX9ghemGOFRT-3VkgDjRXcL54SaY-gQrp7Ju0XcScrETAdxn8CIr6k16twu_Q3tP15_VqNbkM3HOLmU/s1600/20180623_144053.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo of the author's legs with scars on the knees" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidMVKgP434VYQsD64BjDBFLK7KNNm4vb3xXHbE9xnQlT0yvL4kOoS24UhYOBAwMkX9ghemGOFRT-3VkgDjRXcL54SaY-gQrp7Ju0XcScrETAdxn8CIr6k16twu_Q3tP15_VqNbkM3HOLmU/w480-h640/20180623_144053.jpg" title="photo of the author's legs with scars on the knees" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Note the four circular scars on the left leg (2 from screws, 2 arthroscope ports). </td></tr>
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I'm planning on a 1year update in August on this topic, and also a post next month on a related walking-gait side project. Hopefully I'll continue to be on the up-and-up and will have more cool things to show then!</div>
Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-37092000672414036712017-12-29T11:45:00.004-05:002020-08-27T19:58:16.380-04:00Calipers Box round 2 (post 2/2)<div class="separator" style="clear: both; text-align: left;">
Hinge detail. I messed up a bit with the mortise widths, so I cut shims from scrap walnut and sanded them flat. The hinges for this one also open 180deg per giftee's request (they turned out so nice I'm thinking of modifying mine to open flat too)</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjDPitl-RVwYyj1_jrJ8iO4t88eQTHAF4pt4OANfDG8ATTQbJeOB-_-qVCJL4Ri16BApEn5f9gFdeNAp386SA8hKKSYtYvfBRmd8e7ypDRxfV_iDHmpXbrTf8im7Fi-EoiApOLYmfglFpv/s1600/20171205_183844.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="brass hinge and wooden shim in carved box inset" border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjDPitl-RVwYyj1_jrJ8iO4t88eQTHAF4pt4OANfDG8ATTQbJeOB-_-qVCJL4Ri16BApEn5f9gFdeNAp386SA8hKKSYtYvfBRmd8e7ypDRxfV_iDHmpXbrTf8im7Fi-EoiApOLYmfglFpv/w320-h240/20171205_183844.jpg" title="brass hinge and wooden shim in carved box inset" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgVYX95QJny5FQxrDH28gPNPpJ4mq6awXUX9zKSw6W9t3Hncm-O_iEAjgeZuohdTTHhoWsP2OW5pT2k2ViBdShWrS0mmWxMmnOzJg7Plxgh0wsNjd2yYPBvEiKCA91h_7L3kU5oWMDHRLJn/s1600/20171205_183828.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="brass hinge and wooden shim in carved box inset" border="0" data-original-height="1600" data-original-width="1200" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgVYX95QJny5FQxrDH28gPNPpJ4mq6awXUX9zKSw6W9t3Hncm-O_iEAjgeZuohdTTHhoWsP2OW5pT2k2ViBdShWrS0mmWxMmnOzJg7Plxgh0wsNjd2yYPBvEiKCA91h_7L3kU5oWMDHRLJn/w240-h320/20171205_183828.jpg" title="brass hinge and wooden shim in carved box inset" width="240" /></a></div>
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Putting finish on the inside. I masked the pockets because I'm putting felt in this box (glue doesn't stick well to polyurethane.) I'm using satin polyurethane because it offers a marginally better protective layer than oil finishes, and it keeps enough of the grain texture to avoid looking awfully glassy.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpXc-uZdYMh7tEfH84Ag14qWNaV2TCqWDPTS0LIj1HH1_5xdi5blbS4Nflb4w1kn78_l_8zRRIakvjhp_hk7gcfModcfGsMk7IP6Hfub7hU0RHcNWRpv8YUEdt-8iUfwOCK2fKCkpfKLuU/s1600/20171216_154729.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="wooden box with masking tape around pockets" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpXc-uZdYMh7tEfH84Ag14qWNaV2TCqWDPTS0LIj1HH1_5xdi5blbS4Nflb4w1kn78_l_8zRRIakvjhp_hk7gcfModcfGsMk7IP6Hfub7hU0RHcNWRpv8YUEdt-8iUfwOCK2fKCkpfKLuU/w640-h480/20171216_154729.jpg" title="wooden box with masking tape around pockets" width="640" /></a></div>
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<span><a name='more'></a></span>Outlining felt with sharpie. The calipers pocket took two pieces, so I shaved the overlapping section into a taper to remove the bump.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTBuMET3QQCZc9JVhoyqIoFSA-JN5q1rrBHCXPlsX0ICkcTWHh79esTCQ1qL5q8xCip5iAAZeFIAsasBuzvLrEMK2Yy3vfTA-hSurFA-nld5oh6W0vKAa5sS8UDvvk6nJKe-I7OksUiQH7/s1600/20171217_174535.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="felt pressed into pocket cavities and marked with sharpie" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTBuMET3QQCZc9JVhoyqIoFSA-JN5q1rrBHCXPlsX0ICkcTWHh79esTCQ1qL5q8xCip5iAAZeFIAsasBuzvLrEMK2Yy3vfTA-hSurFA-nld5oh6W0vKAa5sS8UDvvk6nJKe-I7OksUiQH7/w480-h640/20171217_174535.jpg" title="felt pressed into pocket cavities and marked with sharpie" width="480" /></a></div>
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This glue is the best (<a href="http://www.avamakesthings.com/search/label/climbing%20feet">I originally got it for gluing shoe rubber...</a>) but it has noxious fumes. Ventilate well when using it!<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8YJfS1jbTDnlqHcTAB7FjGYyN1tXUQCB10kXAwjh5olT5sWtwt0nGldgvlKQBNxDg1MFDpIrdLsn7_qaR41DCCMpVgVR09vQcUgj3GuFUN4QA_dqBUpOTvRpwQJc4p2Ij9ROKH1H_LsVx/s1600/20171217_184356.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="piece of felt prepped with colle de cologne glue" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8YJfS1jbTDnlqHcTAB7FjGYyN1tXUQCB10kXAwjh5olT5sWtwt0nGldgvlKQBNxDg1MFDpIrdLsn7_qaR41DCCMpVgVR09vQcUgj3GuFUN4QA_dqBUpOTvRpwQJc4p2Ij9ROKH1H_LsVx/w640-h480/20171217_184356.jpg" title="piece of felt prepped with colle de cologne glue" width="640" /></a></div>
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The back of a knife is good for pressing the felt into tight corners. I left the box to dry overnight, then scraped/sanded off excess glue.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpRBSnJCG80lkjZfVxaMkdty4DzYMcLPMXSi5RYfZoRF6yPUYv1jY0yDTEOqMUYzYpCcl-uhNHDCzhwyrwRPcqd9FqL_gsak7pYeB_Xv4mQBHl-RaDTxXeGHkGdUEs0PbawiclzGKuBaOV/s1600/20171217_184807.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="felt pressed into pockets with excess trimmed" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpRBSnJCG80lkjZfVxaMkdty4DzYMcLPMXSi5RYfZoRF6yPUYv1jY0yDTEOqMUYzYpCcl-uhNHDCzhwyrwRPcqd9FqL_gsak7pYeB_Xv4mQBHl-RaDTxXeGHkGdUEs0PbawiclzGKuBaOV/w640-h480/20171217_184807.jpg" title="felt pressed into pockets with excess trimmed" width="640" /></a></div>
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Putting finish on the back.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-rIUi_gA_37lSqlt2U8yzBjZskR2U91g2-3bRS-TG26_kOSK4t-aFpPailI9x7dtpPeOOAjeozpLYTsbfznNLkNC30EDKQ37kA4j_yklQ-hDUN_NEY5EA1AcwaBnAoFUGP7an5mA0dBs4/s1600/20171219_230341.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="box with polyurethane coat" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-rIUi_gA_37lSqlt2U8yzBjZskR2U91g2-3bRS-TG26_kOSK4t-aFpPailI9x7dtpPeOOAjeozpLYTsbfznNLkNC30EDKQ37kA4j_yklQ-hDUN_NEY5EA1AcwaBnAoFUGP7an5mA0dBs4/w640-h480/20171219_230341.jpg" title="box with polyurethane coat" width="640" /></a></div>
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I completed this box in time for Christmas! These photos are taken with a much nicer viewcamera.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSzurO0gNcIsq-fr4OGiq8bcX0pQy_h5R3NAjoWO87tySx0uJAtiZ-Wr76igkSDtSHxrKQliTG9cQwSdWprI43IU9EifXEuAYG2nqZf6u7kWVLaMIwpH-aueGNXOYrCUXYwEcqv_uKS3bx/s1600/DSC05346_r.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="closeup view of calipers in box" border="0" data-original-height="1067" data-original-width="1600" height="426" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSzurO0gNcIsq-fr4OGiq8bcX0pQy_h5R3NAjoWO87tySx0uJAtiZ-Wr76igkSDtSHxrKQliTG9cQwSdWprI43IU9EifXEuAYG2nqZf6u7kWVLaMIwpH-aueGNXOYrCUXYwEcqv_uKS3bx/w640-h426/DSC05346_r.jpg" title="closeup view of calipers in box" width="640" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCRRuxzObbKKuryRLfks2NDk-gneK7sM6BzqxIMnFJd1tqjxxhkqPExFfT2jrKBryGgmBcefB8wF5KYmP-_7ONX6gwgD8fkxqGUC7KObhqABSqc3kXykRo4tS701rRlRc0oQLF1HXQW-wu/s1600/DSC05348_r.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="photo of calipers in box" border="0" data-original-height="1067" data-original-width="1600" height="426" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCRRuxzObbKKuryRLfks2NDk-gneK7sM6BzqxIMnFJd1tqjxxhkqPExFfT2jrKBryGgmBcefB8wF5KYmP-_7ONX6gwgD8fkxqGUC7KObhqABSqc3kXykRo4tS701rRlRc0oQLF1HXQW-wu/w640-h426/DSC05348_r.jpg" title="photo of calipers in box" width="640" /></a></div>
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2/2 boxes done! Glamour shots in the sunlight.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFVGg8PukSzc1DHZy_u-5CcDtF8QBEIiYn0kq7xE5QPhiPJ9QnZgUO0L8QGnV0scuNUQj6pZpRrq3yBJ7r5mI_LnNcUm2e3KC4uJ7BOm2hs9W5EwQG5DGFjljcNwoL8qDu5NhjLJgUguaS/s1600/20171221_112758.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="small and large walnut calipers boxes" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFVGg8PukSzc1DHZy_u-5CcDtF8QBEIiYn0kq7xE5QPhiPJ9QnZgUO0L8QGnV0scuNUQj6pZpRrq3yBJ7r5mI_LnNcUm2e3KC4uJ7BOm2hs9W5EwQG5DGFjljcNwoL8qDu5NhjLJgUguaS/w640-h480/20171221_112758.jpg" title="small and large walnut calipers boxes" width="640" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg1DqwFRGdpg4Kbb8EY4-WVEZumnhZI_iGy638RJ7p30DQPpOh6y6d-jjEvbYM079Z1mbROdBda3UxzyPQ1fZ_RCOmyI3ZJVhezbcBYFm0G_1ssn8dXLJjoH1ZaEJ4SaT5RG-f5MpJvQ_2U/s1600/20171221_112719.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="lids of small and large calipers boxes" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg1DqwFRGdpg4Kbb8EY4-WVEZumnhZI_iGy638RJ7p30DQPpOh6y6d-jjEvbYM079Z1mbROdBda3UxzyPQ1fZ_RCOmyI3ZJVhezbcBYFm0G_1ssn8dXLJjoH1ZaEJ4SaT5RG-f5MpJvQ_2U/w640-h480/20171221_112719.jpg" title="lids of small and large calipers boxes" width="640" /></a></div>
<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-53001569630901807252017-12-17T00:14:00.002-05:002020-08-25T19:34:26.792-04:00Farmhouse Table<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlbjntYQYIl1Y7NBsMZFVEu0X7F7BFSmNxnI07c29YfJyKVoQbNqDurgEE2Hs9uBtsD5CE7Qjbr3-X0AbIW_VbVWArDVRViOn6NgcC0-hNp2Hd2-bPrHEw0LYzSRuVOGbq6HBNBZEfmCY6/s1600/20171210_201153.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="photo of finished wooden table" border="0" data-original-height="1147" data-original-width="1600" height="458" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlbjntYQYIl1Y7NBsMZFVEu0X7F7BFSmNxnI07c29YfJyKVoQbNqDurgEE2Hs9uBtsD5CE7Qjbr3-X0AbIW_VbVWArDVRViOn6NgcC0-hNp2Hd2-bPrHEw0LYzSRuVOGbq6HBNBZEfmCY6/w640-h458/20171210_201153.jpg" title="photo of finished wooden table" width="640" /></a></div>
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We needed a dining table, so I made a table! I bought wood from a lumberyard, then spent two months in the HobbyShop trying to finish this in time to put food on it for Thanksgiving (spoiler: just barely did it in time)</div>
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Wood required for this project:</div>
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<ul>
<li>5 6ft 2x10s</li>
<li>4 6ft 2x4s</li>
<li>2 6ft 4x4s</li>
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as well as assorted 1" wooden dowels and miscellaneous hardware. I'll point out the important ones when they get used.<br />
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The first step, as always, is a planning sketch. I got inspiration from a google images search with terms 'farmhouse trestle table', but wanted to include some personal touches like tapered legs and breadboard ends.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgB4SkGiczcsbEBn9-RQEyC8JIrrZUxqIVfa7RooVjfHyeHePe2Db8F27rVE3AkqYkTZOEY4_aHlLCRT3M9eMFT7thgwLk0SUPLyMHth8kIYfyNR4CPDdx-XRfwewbtLsyc_CJOt7C42urO/s1600/20171129_011016.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="sketches of wooden part dimensions" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgB4SkGiczcsbEBn9-RQEyC8JIrrZUxqIVfa7RooVjfHyeHePe2Db8F27rVE3AkqYkTZOEY4_aHlLCRT3M9eMFT7thgwLk0SUPLyMHth8kIYfyNR4CPDdx-XRfwewbtLsyc_CJOt7C42urO/w480-h640/20171129_011016.jpg" title="sketches of wooden part dimensions" width="480" /></a></div>
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I started with the top. I squared-up 2x10s with the jointer and tablesaw, and glued them up.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUa_RMvS2ZuZwu9eVutcjO14FS58NEtz_R8QDadU8LJoiLOl0IgfSRUrT3t0wGy_lYj4STvwIENIdU45qgu1Zd3k6KeYWxD0vrauboPTbhvUmp-hpo23OD3BVPKd2k3RG3PYJ4OFLwh-v0/s1600/20170927_175718.jpg" style="margin-left: auto; margin-right: auto;"><img alt="tabletop boards dry-clamped together" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUa_RMvS2ZuZwu9eVutcjO14FS58NEtz_R8QDadU8LJoiLOl0IgfSRUrT3t0wGy_lYj4STvwIENIdU45qgu1Zd3k6KeYWxD0vrauboPTbhvUmp-hpo23OD3BVPKd2k3RG3PYJ4OFLwh-v0/w640-h480/20170927_175718.jpg" title="tabletop boards dry-clamped together" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Clamping boards down to check for warpage</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLZdt8fcRHKfGmfo24ujJMFztc26-e4Cxb8ChLgfA53JICMhAI7wvhOSXp8JXYISQfsCqfqe6iNc_1AMAy0taPc6kn6XkA0Fpuw0dzA3EVeCmIcJgnEPAdn9uD6gL-aCa4VnoSaetqMHh-/s1600/20170927_181353.jpg" style="margin-left: auto; margin-right: auto;"><img alt="pencil markings on boards ensuring that they get glued in the correct order" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLZdt8fcRHKfGmfo24ujJMFztc26-e4Cxb8ChLgfA53JICMhAI7wvhOSXp8JXYISQfsCqfqe6iNc_1AMAy0taPc6kn6XkA0Fpuw0dzA3EVeCmIcJgnEPAdn9uD6gL-aCa4VnoSaetqMHh-/w640-h480/20170927_181353.jpg" title="pencil markings on boards ensuring that they get glued in the correct order" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Drawing all over boards to mark grain orientations I'm happy with</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUa3W0eowEtRSNM40NehbhlzBFwWg1DTgjyY9XsTQE1dUacNUI-8e2sWZSt6pnZSfAuKX6rT0M9I6CU4vEDwGPIlg6Y2i1t2goME293TX1wMZGlLx3fWWf29HOcPmJ9lqaWcloD0KYsD22/s1600/20170927_183526.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="top view of glueup that shows thin slivers of wood protecting the tabletop from clamps" border="0" data-original-height="1600" data-original-width="1200" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUa3W0eowEtRSNM40NehbhlzBFwWg1DTgjyY9XsTQE1dUacNUI-8e2sWZSt6pnZSfAuKX6rT0M9I6CU4vEDwGPIlg6Y2i1t2goME293TX1wMZGlLx3fWWf29HOcPmJ9lqaWcloD0KYsD22/w240-h320/20170927_183526.jpg" title="top view of glueup that shows thin slivers of wood protecting the tabletop from clamps" width="240" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrUg4oGX10cneT-tJj0adWDlOHcUEvCAbfmNXevKa6kddiBWYHpPnu3saifXOjIOMweg5uKbwF2CFVM9_GcpVppe2g7dSKRl_XbqJBffEdqXQBZPXvHoTGEEybUDM3sSAuMENnT2IK5AxH/s1600/20170927_183515.jpg"><img alt="photo of tabletop boards being glued and clamped together" border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrUg4oGX10cneT-tJj0adWDlOHcUEvCAbfmNXevKa6kddiBWYHpPnu3saifXOjIOMweg5uKbwF2CFVM9_GcpVppe2g7dSKRl_XbqJBffEdqXQBZPXvHoTGEEybUDM3sSAuMENnT2IK5AxH/w320-h240/20170927_183515.jpg" title="photo of tabletop boards being glued and clamped together" width="320" /></a></div>
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A note about grain orientation for long glue-ups like this. The standard dimensional lumber I'm using is plain-sawn (as opposed to quarter sawn). Being plain-sawn (flat sawn) means that the boards contain the curvature of the growth rings.</div>
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<tr><td style="text-align: center;"><img alt="plain sawn (left) cuts flat slices across the log, so each plank's cross section contains smiley-face-shaped curvature. Rift (middle) and quarter (right) sawn take radial slices, so the resulting planks have more uniform and straight grain in cross-section" height="158" src="http://summittforestproducts.com/wp-content/uploads/2016/10/download-1.jpg" style="margin-left: auto; margin-right: auto;" title="plain sawn (left) cuts flat slices across the log, so each plank's cross section contains smiley-face-shaped curvature. Rift (middle) and quarter (right) sawn take radial slices, so the resulting planks have more uniform and straight grain in cross-section" width="400" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://summittforestproducts.com/wp-content/uploads/2016/10/download-1.jpg" target="_blank">summitforestproducts.com</a></td></tr>
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This also means that since moisture loss is greatest along the growth rings, plain-sawn boards in particular are prone to curling away from the direction of the growth rings. This webpage does a good job of explaining the phenomenon further: <a href="https://www.popularwoodworking.com/article/why-wood-warps" target="_blank">popularwoodworking.com/article/why-wood-warps</a>.</div>
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<tr><td style="text-align: center;"><img src="https://twwcdn-thewoodwhisperer.netdna-ssl.com/wp-content/uploads/cup-150x64.gif" style="margin-left: auto; margin-right: auto;" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="https://www.thewoodwhisperer.com/articles/avoiding-cupped-panels/" target="_blank">thewoodwhisperer.com</a></td></tr>
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This kind of warpage, called cupping, only curls the board around 1/8", but to prevent a runaway feedback loop it's good practice to alternate the grain orientations on adjacent boards. This way it averages out and is less apparent in the final tabletop.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0qKWyR7SmBXeYGJfhTUdpDeBah2ZQqglx5J5iF9MeMuQ3RiHfeTdBq65IdBoeYj9ndOjixy-wQpZJcICabwV5RHSmq_9l060M6SS-Xo1gLVsniMf2tDD0QqrYzKd42arhiXtatCXxpq8p/s1600/woodgrain.png" style="margin-left: auto; margin-right: auto;"><img alt="diagram of two planks next to each other, one with wood grain in smiley-face (curving upwards) orientation and the other with a frowny-face (curving downwards) orientation" border="0" data-original-height="180" data-original-width="657" height="108" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0qKWyR7SmBXeYGJfhTUdpDeBah2ZQqglx5J5iF9MeMuQ3RiHfeTdBq65IdBoeYj9ndOjixy-wQpZJcICabwV5RHSmq_9l060M6SS-Xo1gLVsniMf2tDD0QqrYzKd42arhiXtatCXxpq8p/w400-h108/woodgrain.png" title="diagram of two planks next to each other, one with wood grain in smiley-face (curving upwards) orientation and the other with a frowny-face (curving downwards) orientation" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Glue boards so that the endgrain lines up like so</td></tr>
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I leaned up my glue monstrosity against a wall and started working on the frame components. First up were the 4x4 legs. I wanted to make them slightly tapered, so they would look less like dimensional lumber. To cut repeatable tapers, I made a bandsaw jig that fit the miter track.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-QW7VbfhEEelpzeTK6xVJiOz0QtemmB1dCgyC_V9OnA1cEZGn2Q9SI7usw3WIq8ppRhtr3cGnNvXNRKqLYQia-pnFu8J60wa6rCxgB624fj3mF3Les9Pu5eItmZCG08ovI2c_cG_CFe-V/s1600/20171004_203417.jpg" style="margin-left: auto; margin-right: auto;"><img alt="4x4 held at an angle to the bandsaw blade using a plywood jig" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-QW7VbfhEEelpzeTK6xVJiOz0QtemmB1dCgyC_V9OnA1cEZGn2Q9SI7usw3WIq8ppRhtr3cGnNvXNRKqLYQia-pnFu8J60wa6rCxgB624fj3mF3Les9Pu5eItmZCG08ovI2c_cG_CFe-V/w640-h480/20171004_203417.jpg" title="4x4 held at an angle to the bandsaw blade using a plywood jig" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">leg clamped down in the jig</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgoG7BoiQtijgEblLYJL_Pmz2gXhypfY-hTnKmNdgG6IZWX9RJB22QHtbb_tiJnZtRO4JmEowgd6yHPckKoupAMOCImd9_GAlYXR4GfPG086Nuq3eBHPR3sezxYN9v3k7sqAMhXyRVEVih/s1600/20171004_203428.jpg" style="margin-left: auto; margin-right: auto;"><img alt="jig consists of a piece of plywood screwed at an angle stacked on top of a plywood base plate. Two clamps on top hold the wood to the jig." border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgoG7BoiQtijgEblLYJL_Pmz2gXhypfY-hTnKmNdgG6IZWX9RJB22QHtbb_tiJnZtRO4JmEowgd6yHPckKoupAMOCImd9_GAlYXR4GfPG086Nuq3eBHPR3sezxYN9v3k7sqAMhXyRVEVih/w400-h300/20171004_203428.jpg" title="jig consists of a piece of plywood screwed at an angle stacked on top of a plywood base plate. Two clamps on top hold the wood to the jig." width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">side view of jig</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGnlaBJfTKNevWpdPOW-Hh-pDqoFQ_xF0waa2jsDBTjpfGWRsn7_cvP0rSFP4Moh9xyuvudn_mizrPSqOjqdcvKCt6P8TFltqUB2JkBUBTJAqI0CfCGhGvQdWKi3TyP9rQJ2iqUkKuNgKk/s1600/20171004_204021.jpg" style="margin-left: auto; margin-right: auto;"><img alt="piece of already-cut wood being realigned on the jig to cut additional faces" border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGnlaBJfTKNevWpdPOW-Hh-pDqoFQ_xF0waa2jsDBTjpfGWRsn7_cvP0rSFP4Moh9xyuvudn_mizrPSqOjqdcvKCt6P8TFltqUB2JkBUBTJAqI0CfCGhGvQdWKi3TyP9rQJ2iqUkKuNgKk/w400-h300/20171004_204021.jpg" title="piece of already-cut wood being realigned on the jig to cut additional faces" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">note the tapered shim on the bottom to compensate for already-cut sides</td></tr>
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After tapering the legs, I cut each one of them to proper length. I relied on google's estimate of 30" for the average height of a dinner table. I also used the cut-off tapered scraps as shims to align the legs on the chopsaw (otherwise they wouldn't sit flat.)<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1ABAt23TrvT5H4O3zD1r2_kkHkMG4NQHb_vbne6ufYAFENhETCkaB6Bmzauevn9GGs9tnia4qNNZvmFTy9KaAk98NuYJnVs0rLFSqctGgJWj4ahR2J4OLK9ypD-kutGPZ2dO1X9Ocsdps/s1600/20171018_174104.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="when tapered shims are added, the wooden leg lies square against the cutting table" border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1ABAt23TrvT5H4O3zD1r2_kkHkMG4NQHb_vbne6ufYAFENhETCkaB6Bmzauevn9GGs9tnia4qNNZvmFTy9KaAk98NuYJnVs0rLFSqctGgJWj4ahR2J4OLK9ypD-kutGPZ2dO1X9Ocsdps/w400-h300/20171018_174104.jpg" title="when tapered shims are added, the wooden leg lies square against the cutting table" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZaiwyYrgb16Sdc2NF7se117_zlpTpJb5jIJ4Ndtbo-I_ogonX45aDbyIZaKZHQiYcggKDKIyqMBXuO3GtHwf9CdYJgkzspn4CauqPdfFW-afpJ7UWIPrMTx85B9OcESs3GcxC7CsmMP61/s1600/20171018_174006.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="table leg being cut by a chop saw" border="0" data-original-height="1200" data-original-width="1600" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZaiwyYrgb16Sdc2NF7se117_zlpTpJb5jIJ4Ndtbo-I_ogonX45aDbyIZaKZHQiYcggKDKIyqMBXuO3GtHwf9CdYJgkzspn4CauqPdfFW-afpJ7UWIPrMTx85B9OcESs3GcxC7CsmMP61/w200-h150/20171018_174006.jpg" title="table leg being cut by a chop saw" width="200" /></a></div>
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Following that, I used a V-shaped jig to cut a 3" flat into the tops of the legs. The mounting bolts will go here.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjccXC1zQhnq2BU954EW17hX8HVNeREP_irQBTAALSM-Szyj0PH8OrC-ywrwAzqM8xCBFWImjNG1l_YB2NnaqYhouYvN7LALpInvLNwQ2FHUME7TDi6lhzStXPPQGxGvV-R9GIj5PAc-8SJ/s1600/20171018_175142.jpg" style="margin-left: auto; margin-right: auto;"><img alt="V-shaped jigs allow the tapered-square leg to rest on its diagonal" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjccXC1zQhnq2BU954EW17hX8HVNeREP_irQBTAALSM-Szyj0PH8OrC-ywrwAzqM8xCBFWImjNG1l_YB2NnaqYhouYvN7LALpInvLNwQ2FHUME7TDi6lhzStXPPQGxGvV-R9GIj5PAc-8SJ/w640-h480/20171018_175142.jpg" title="V-shaped jigs allow the tapered-square leg to rest on its diagonal" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">cutting the flat</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg50KRHLtPZUc3K-QGKsmnmHbpB3C4b4BZ4PDyrVtUM3F0_GxbXHrft3Bla4aUmXFWxA0xlv31A1YFjZmg2yJp6agWz5ti-tuLX06rF9X1LShszv9hiFemdhmcpiP3g90mDNvObzXFx6EOH/s1600/20171018_175512.jpg" style="margin-left: auto; margin-right: auto;"><img alt="the V-jig also works to hold the leg in a vice for hand-sawing" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg50KRHLtPZUc3K-QGKsmnmHbpB3C4b4BZ4PDyrVtUM3F0_GxbXHrft3Bla4aUmXFWxA0xlv31A1YFjZmg2yJp6agWz5ti-tuLX06rF9X1LShszv9hiFemdhmcpiP3g90mDNvObzXFx6EOH/w480-h640/20171018_175512.jpg" title="the V-jig also works to hold the leg in a vice for hand-sawing" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">cutting the flat</td></tr>
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In the interest of making an entirely disassemble-able frame, I'm mounting the legs to the apron using <a href="http://www.rockler.com/surface-mount-corner-brackets-for-table-aprons" target="_blank">these premade corner brackets.</a> I marked bolt locations with a punch, then drilled pilot holes on the drillpress.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuCtfvVZtE3gB6Y1nSIi2TzcUp-NJL4IjtvuyPcPqVEnpRSCHgRMINIxKbdnH8dbwDoQdk6njdl5TQWS4yc9S9lsS-LNGJyRRlhoCdyqrZFxdewAloz6u1DOWlK9LVjVSF0N32x0awG9p1/s1600/20171025_185036.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="drilling holes at the punch marks" border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuCtfvVZtE3gB6Y1nSIi2TzcUp-NJL4IjtvuyPcPqVEnpRSCHgRMINIxKbdnH8dbwDoQdk6njdl5TQWS4yc9S9lsS-LNGJyRRlhoCdyqrZFxdewAloz6u1DOWlK9LVjVSF0N32x0awG9p1/w400-h300/20171025_185036.jpg" title="drilling holes at the punch marks" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIrVMfYgML6Kn4ENKKopzrizm0PjUX55F6t7mDHA87m-uk3Xy1kYua_v6YZGI0iiIPc86RJ0Vp33GCMVTm1GjKB97z1XTaUuwCI8ooIl60p-LmkkPjcmLzn3mZ6bI_i06BUccVDDqq0whc/s1600/20171025_184523.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="Using the bracket to mark where to drill holes" border="0" data-original-height="1600" data-original-width="1200" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIrVMfYgML6Kn4ENKKopzrizm0PjUX55F6t7mDHA87m-uk3Xy1kYua_v6YZGI0iiIPc86RJ0Vp33GCMVTm1GjKB97z1XTaUuwCI8ooIl60p-LmkkPjcmLzn3mZ6bI_i06BUccVDDqq0whc/w150-h200/20171025_184523.jpg" title="Using the bracket to mark where to drill holes" width="150" /></a></div>
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I threaded on <a href="https://www.amazon.com/gp/product/B001DT16DW/ref=oh_aui_detailpage_o07_s00?ie=UTF8&psc=1" target="_blank">the hanger bolts</a> using a nut and a socket wrench (the two ends have different thread sizes, so the nut bites on enough to apply torque with the wrench.) Afterwards, I repaired the threads using a die.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_1nR2C1Wl5E444yi99IneFA6D51MmkJjANwQI3gBwcKIDtr_60o0e0JOTkKns_oQ-vKK8fr78qGnayIZ5ea-KqFDyLGuUO04hvHr2-5N9fRvaLorfyluAq45v1tespN_S5-lBYXU3iq2v/s1600/20171028_132442_1.gif" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="the author using a die to reform any smashed threads on the bolt" border="0" data-original-height="496" data-original-width="368" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh_1nR2C1Wl5E444yi99IneFA6D51MmkJjANwQI3gBwcKIDtr_60o0e0JOTkKns_oQ-vKK8fr78qGnayIZ5ea-KqFDyLGuUO04hvHr2-5N9fRvaLorfyluAq45v1tespN_S5-lBYXU3iq2v/w237-h320/20171028_132442_1.gif" title="the author using a die to reform any smashed threads on the bolt" width="237" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj2M8EY0xtzXwxmVmt6-DzGosHjQvYDZ2-0Pi108PKWSxjGXQjCpWWkvL1izCJ_S9bE8nHHm8pxizh31VdZ5wUYixIxgcWfSthv_25VIvN60SNlZWYiC3K_qtQkxWoquhX6XzgLiBqQOQo/s1600/20171025_190029.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="doublesided bolts screw into the wood and have threads to accept fasteners, but do not have a convenient hex surface to attach a wrench to" border="0" data-original-height="1600" data-original-width="1200" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj2M8EY0xtzXwxmVmt6-DzGosHjQvYDZ2-0Pi108PKWSxjGXQjCpWWkvL1izCJ_S9bE8nHHm8pxizh31VdZ5wUYixIxgcWfSthv_25VIvN60SNlZWYiC3K_qtQkxWoquhX6XzgLiBqQOQo/w240-h320/20171025_190029.jpg" title="doublesided bolts screw into the wood and have threads to accept fasteners, but do not have a convenient hex surface to attach a wrench to" width="240" /></a></div>
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Last step on the legs was drilling clearance holes and adding threaded inserts to the bottom to <a href="https://www.amazon.com/gp/product/B06XH52SJW/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1" target="_blank">accommodate adjustable feet</a>. Then the legs were done!</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfMPOK31SOxUfim6YLnAwOVpg5icyT1j0LoiPlv2-kMBwmSQAct_rVk0c9Z0mzRacEiEV-G6kmm40KezYnc6C-115nkKJNc4H6zTIukCggV-RtZbAv_Vxmd-N2BW_8nwnmIyw_P9Tq-2eN/s1600/20171028_125847.jpg" style="margin-left: auto; margin-right: auto;"><img alt="threaded inserts provide screw access in the endgrain without splitting the wood" border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfMPOK31SOxUfim6YLnAwOVpg5icyT1j0LoiPlv2-kMBwmSQAct_rVk0c9Z0mzRacEiEV-G6kmm40KezYnc6C-115nkKJNc4H6zTIukCggV-RtZbAv_Vxmd-N2BW_8nwnmIyw_P9Tq-2eN/w300-h400/20171028_125847.jpg" title="threaded inserts provide screw access in the endgrain without splitting the wood" width="300" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Hammering in threaded inserts</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiBWILkIAG3Yzeh2LuTBMbq9OXu7XTZpPiVnXzFGpJwXYRA-UF7LxlIn5jLfsgJuOl3sID9S8NRvMW-bPr88NItjtS42PwrAtskmyXWAXe7-mPcyF5FwkR3GJo8GJGTdFZQ6ovP7hyphenhyphengmUD/s1600/20171025_193246.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="photo showing four complete tablelegs" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgiBWILkIAG3Yzeh2LuTBMbq9OXu7XTZpPiVnXzFGpJwXYRA-UF7LxlIn5jLfsgJuOl3sID9S8NRvMW-bPr88NItjtS42PwrAtskmyXWAXe7-mPcyF5FwkR3GJo8GJGTdFZQ6ovP7hyphenhyphengmUD/w640-h480/20171025_193246.jpg" title="photo showing four complete tablelegs" width="640" /></a></div>
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Moving on to the apron, I cut 2x4s to size and then added a thin dado using the tablesaw to accommodate <a href="http://www.rockler.com/table-top-fasteners" target="_blank">these Z-clip table fasteners</a>. Clamping the tabletop to the apron using these slots will allow for seasonal moisture expansion and lessen the chances of cracking the table. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgloLK_UNjw1nJz7iHrlVLoAtlQDClpdhMSkZsMnTbXo2WlG174ugd6Wwt00fkBhoE-27uysNLrjA9MHa1QSUWa_msKyPx7ZrAva6ejF2vNEYiW7BjsHZ38sS5S3UCEivP4a_NW3n4oOEIO/s1600/20171018_192107.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="pieces of wood with long thin slots cut along one face" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgloLK_UNjw1nJz7iHrlVLoAtlQDClpdhMSkZsMnTbXo2WlG174ugd6Wwt00fkBhoE-27uysNLrjA9MHa1QSUWa_msKyPx7ZrAva6ejF2vNEYiW7BjsHZ38sS5S3UCEivP4a_NW3n4oOEIO/w640-h480/20171018_192107.jpg" title="pieces of wood with long thin slots cut along one face" width="640" /></a><br />
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Because the legs are tapered, I needed to taper the ends of the apron as well. I measured the leg angles and set the chop saw to a 1deg angle (this ended up being slightly too much, but the gaps aren't too noticeable)</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMbfxUDmMqvxYPBLvI5r4HJp08lBDihWNF5YI9B7gwy0GvfX2u_e62gBjJzNaHuddGh9UxlF74sahbwbOpgixA3WjlzRbPtOIt3kKXf7mGi4jKy-_bmWMQ87n2KVrwWTLHoqBoPW5LW6RU/s1600/20171018_193203.jpg" style="margin-left: auto; margin-right: auto;"><img alt="chop saws can be rotated relative to their fences" border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMbfxUDmMqvxYPBLvI5r4HJp08lBDihWNF5YI9B7gwy0GvfX2u_e62gBjJzNaHuddGh9UxlF74sahbwbOpgixA3WjlzRbPtOIt3kKXf7mGi4jKy-_bmWMQ87n2KVrwWTLHoqBoPW5LW6RU/w300-h400/20171018_193203.jpg" title="chop saws can be rotated relative to their fences" width="300" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Setting chopsaw angle</td></tr>
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I used a kreg jig to drill pocket holes for the lateral (front-back) stretcher pieces and the center apron reinforcement. Since I had tapered the lateral stretcher pieces already, I used my cut-off shims to compensate for angle (lower left photo).<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHZ1xe3XCco1eCd7gzbssw9Jwd4p88LMKOAF0rsreGKqqpdn1oa7vnEOnzss2VL9IhxBRIAQvCQBtuSkV7U9gnCjtac4pmAbw7x66PAbvow_2WBfxoX55el-rVZIA9vIhvwbFgf4PFNt5X/s1600/20171025_175433.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="kreg jigs have guide holes to enable drilling at shallow angles without splitting or splintering the wood" border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgHZ1xe3XCco1eCd7gzbssw9Jwd4p88LMKOAF0rsreGKqqpdn1oa7vnEOnzss2VL9IhxBRIAQvCQBtuSkV7U9gnCjtac4pmAbw7x66PAbvow_2WBfxoX55el-rVZIA9vIhvwbFgf4PFNt5X/w400-h300/20171025_175433.jpg" title="kreg jigs have guide holes to enable drilling at shallow angles without splitting or splintering the wood" width="400" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjH_WLmGosuGcSBr43V5NM-cHKGoJO3W32FWpNY7Qt5udNg1sb1drvh_hrXzpoMWHZpZEESVk8EmEkap9k781da7qAkVWiY6a7tQThjU3sTuolyTXhEfb8G8XMDipI0uKawd8541cqtF4I5/s1600/20171025_181922.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="apron pieces with screw pockets for attaching to tablelegs" border="0" data-original-height="1600" data-original-width="1200" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjH_WLmGosuGcSBr43V5NM-cHKGoJO3W32FWpNY7Qt5udNg1sb1drvh_hrXzpoMWHZpZEESVk8EmEkap9k781da7qAkVWiY6a7tQThjU3sTuolyTXhEfb8G8XMDipI0uKawd8541cqtF4I5/w240-h320/20171025_181922.jpg" title="apron pieces with screw pockets for attaching to tablelegs" width="240" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfvpyC34zCtu23WMWfScKaY-a3VLhvpsCMt3qkg-se3q-l_HmgxVW7QU1ZQnWykDZLWp1qsa3AGWPHjtIHgrF5rpLJkTSTaEqryZRk5JjmK-lmBIj-dcdJJ8kuPzuntks6VEacOMB9ySun/s1600/20171025_175553.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="drilling screw pockets into wooden beams using a kreg jig" border="0" data-original-height="1600" data-original-width="1200" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfvpyC34zCtu23WMWfScKaY-a3VLhvpsCMt3qkg-se3q-l_HmgxVW7QU1ZQnWykDZLWp1qsa3AGWPHjtIHgrF5rpLJkTSTaEqryZRk5JjmK-lmBIj-dcdJJ8kuPzuntks6VEacOMB9ySun/w240-h320/20171025_175553.jpg" title="drilling screw pockets into wooden beams using a kreg jig" width="240" /></a></div>
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Then I dry-fitted the frame and pronounced it done! I packed away the frame pieces and continued work on the tabletop.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjthWvix03WSleNt6nJK9ninvO9I7LryVkdfbVwFo6a9KBtDb6CFKD2UY5yc5Pc_-XdZm_5ysh0l-MQrjlXJ1KXuNZHIKlVI-7QdPS9rhbDSq_kDhUFrPgy2r2a7wW4FTeYMN-pgIVECap_/s1600/20171028_163327.jpg" style="margin-left: auto; margin-right: auto;"><img alt="table frame screwed together but not yet glued. The background contains large planks of wood lying against the wall and many shelves of tools" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjthWvix03WSleNt6nJK9ninvO9I7LryVkdfbVwFo6a9KBtDb6CFKD2UY5yc5Pc_-XdZm_5ysh0l-MQrjlXJ1KXuNZHIKlVI-7QdPS9rhbDSq_kDhUFrPgy2r2a7wW4FTeYMN-pgIVECap_/w640-h480/20171028_163327.jpg" title="table frame screwed together but not yet glued. The background contains large planks of wood lying against the wall and many shelves of tools" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Dry-fitting frame. Look at all the lovely HobbyShop space in the background<br /><br /></td></tr>
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My original plan was to only have thin breadboard ends as aesthetics and protection for the endgrain, but then the HobbyShop shopmaster went on a rant about how fine furniture's details needed to serve more practical purposes than just aesthetics and that I needed to do breadboards right.</div>
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Suffice to say, I ended up making proper breadboard ends and it was overkill.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjxtKXahyQYU7JMC-LWhJwPKGuaUrLsoScykhktzRf4tZr5rUXj2IrmmhCLiQUOhyphenhyphenZSgIBgTO9-BpLTkCPDO_JKlZ-pI8h91ZnvP_HrfHXwvdBO3LYS6s9j7v17owGH_lsyz-P-gFfJWI8n/s1600/20171129_0110162.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="sketch diagram of breadboard dimensions. Breadboards are narrow pieces of wood that cover the ends of the main tabletop planks" border="0" data-original-height="1600" data-original-width="529" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjxtKXahyQYU7JMC-LWhJwPKGuaUrLsoScykhktzRf4tZr5rUXj2IrmmhCLiQUOhyphenhyphenZSgIBgTO9-BpLTkCPDO_JKlZ-pI8h91ZnvP_HrfHXwvdBO3LYS6s9j7v17owGH_lsyz-P-gFfJWI8n/w130-h400/20171129_0110162.jpg" title="sketch diagram of breadboard dimensions. Breadboards are narrow pieces of wood that cover the ends of the main tabletop planks" width="130" /></a> <img src="https://images.woodmagazine.mdpcdn.com/sites/default/files/styles/article_hero__450x300/public/image/2016/06/13/100673905_0.jpg?timestamp=1465831257" /></div>
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<span style="font-size: x-small;"><a href="https://www.woodmagazine.com/woodworking-tips/techniques/joinery/breadboard" target="_blank">woodmagazine.com</a></span></div>
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Breadboard ends serve two purposes. First, they mechanically counteract cupping (see note on grain orientation above.) Second, they reduce exposed endgrain surface area (endgrain is more fragile).</div>
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Properly-attached breadboard ends need to allow for wood expansion; otherwise stresses will crack the table. This rules out glue as a reasonable attachment mechanism. Instead, I chose to use woodmagazine's method of concealed mortise&tenon + dowel slots. I also decided to use popularwoodworking's method of combining the mortise&tenon with a tongue&groove joint, which allows me to make more concealed mistakes without sacrificing structural integrity. (<a href="https://www.popularwoodworking.com/techniques/joinery/breadboard-ends-2" target="_blank">popularwoodworking also has an excellent guide to breadboard ends in general, check it out</a>)</div>
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As a final detail, I chose to make the mortise&tenon have a slight shoulder above the pockets. Since I'm an amateur and was certain I wouldn't be able to get the breadboards completely flush, I wanted to ensure the inevitable gap would get concealed by some wood versus going through the entire table. This ended up being a good call even if it made everything else more complicated.</div>
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I marked up both breadboards with a marking gauge, then tried mortising them on the mill. That went terribly (board was too tall and vibrated loudly).</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0Q2WMJd-fPnPr8pB6B-g4gTP1zevH4aMWlktrLWrBxJ-cl75YHzKPlmtExPTet4FQ-yTRL0iszKSGSZ-kLl33KBDtLL84ogDvene17IuuLEbAf-VYAHLqRPqghwOFulnKjIe0fiASUJ26/s1600/20171021_153816.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="attempting to bore a pocket in a piece of wood using the mill" border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0Q2WMJd-fPnPr8pB6B-g4gTP1zevH4aMWlktrLWrBxJ-cl75YHzKPlmtExPTet4FQ-yTRL0iszKSGSZ-kLl33KBDtLL84ogDvene17IuuLEbAf-VYAHLqRPqghwOFulnKjIe0fiASUJ26/w320-h240/20171021_153816.jpg" title="attempting to bore a pocket in a piece of wood using the mill" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnaei_Nxt-Yb0FzRMsBZJv4C5yxeS4h2_gmLDbzRek3sO4ADVVF2jTNcvv_AxK-4CSisWNGiqx3GGTdADe0zUqBkCTkY0eGQjYXwTKVY1FOtbJeq4vXlohEAKOZDDMpJx42PUKSTSWAZ-C/s1600/20171021_144926.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="Using a marking gauge to scribe a half inch offset from the sides of the board" border="0" data-original-height="1600" data-original-width="1200" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgnaei_Nxt-Yb0FzRMsBZJv4C5yxeS4h2_gmLDbzRek3sO4ADVVF2jTNcvv_AxK-4CSisWNGiqx3GGTdADe0zUqBkCTkY0eGQjYXwTKVY1FOtbJeq4vXlohEAKOZDDMpJx42PUKSTSWAZ-C/w240-h320/20171021_144926.jpg" title="Using a marking gauge to scribe a half inch offset from the sides of the board" width="240" /></a></div>
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Second attempt was with the mortising machine (new tool!), which went much better. With this machine (effectively a horizontal mill), the workpiece is clamped flat while the tool is moved in XY with a joystick lever. Stop-nuts on the ballscrews let me set a repeatable mortise width and depth.</div>
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First I milled out the pockets, then went back and did the shoulder mortise.<br />
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlx5cE5J_xsHhYlAboZ72rffLstgklxGwg7g_IfynLQzCtbPLM5gAewBA-0HO5Z3E49a71orr4ylEURfVQpDNJ0vbE0mu_tS6gtxcUvLWHdtgausNuYi9aaddt_tUPkZa6wvqI1_zz1djI/s1600/20171025_201458.jpg" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img alt="A mortising tool is effectively a drill press spindle lying flat on a table, and can cut notches into the sides of wooden planks" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlx5cE5J_xsHhYlAboZ72rffLstgklxGwg7g_IfynLQzCtbPLM5gAewBA-0HO5Z3E49a71orr4ylEURfVQpDNJ0vbE0mu_tS6gtxcUvLWHdtgausNuYi9aaddt_tUPkZa6wvqI1_zz1djI/w640-h480/20171025_201458.jpg" title="A mortising tool is effectively a drill press spindle lying flat on a table, and can cut notches into the sides of wooden planks" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">I marked the far edge of each mortise to keep even spacing</td></tr>
</tbody></table>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhn_xBupbgGvJBSb_tpqjbJH1Z-jyyrXsxeQYUghGN_jfMwdOkjvDAWEZvnm_gzCXpt90Hk2KeGDegGW9ZnJVVxNgyfZM7AqFlmcAOs_1iB57xEn77q2NjLh3kfHeyTzW4Mtvzav8lOE9Vn/s1600/20171102_172640.jpg" style="margin-left: auto; margin-right: auto;"><img alt="Cutting the shoulder mortise, which is a shallower pocket than the deep notches" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhn_xBupbgGvJBSb_tpqjbJH1Z-jyyrXsxeQYUghGN_jfMwdOkjvDAWEZvnm_gzCXpt90Hk2KeGDegGW9ZnJVVxNgyfZM7AqFlmcAOs_1iB57xEn77q2NjLh3kfHeyTzW4Mtvzav8lOE9Vn/w640-h480/20171102_172640.jpg" title="Cutting the shoulder mortise, which is a shallower pocket than the deep notches" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Shoulder mortise</td></tr>
</tbody></table>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxLSsSPesuWFpF4lqlttTWEIEgdxMJbsaJ62HreeTKf6IOaj1CImcx5kNV4C9WVFJJBzs9muh7Afz-oB0ePt1o09AMH_H04y4WLUksjCE98PCGrPgk18gziLkcc7QCTRCAO52yObqsZX5O/s1600/20171104_122746.jpg" style="margin-left: auto; margin-right: auto;"><img alt="two planks of wood with mortises for each of the tabletop ends and a shoulder pocket" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxLSsSPesuWFpF4lqlttTWEIEgdxMJbsaJ62HreeTKf6IOaj1CImcx5kNV4C9WVFJJBzs9muh7Afz-oB0ePt1o09AMH_H04y4WLUksjCE98PCGrPgk18gziLkcc7QCTRCAO52yObqsZX5O/w480-h640/20171104_122746.jpg" title="two planks of wood with mortises for each of the tabletop ends and a shoulder pocket" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">completed breadboards</td></tr>
</tbody></table>
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With breadboards done, I put the tabletop on sawhorses and cut it to size with a track saw. Then, I scraped off excess dried glue and started cutting tenons with a plunge router.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwtf4YCjzIpSJLbqHSgL3bqy8oa3JF2UBD4aOnR-Hp0trtzCfrSB6z01IOuxnnVo74g3DZFmnIRFxZlfXqTeu8H-aSFy4SXocieVWyz900URjZCKnzwrqdrFWVzpkZB11k49loUjGliZAB/s1600/20171104_125610.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo showing a clamp jaw slotted into a recess on the underside of the aluminum track" border="0" data-original-height="1200" data-original-width="1600" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiwtf4YCjzIpSJLbqHSgL3bqy8oa3JF2UBD4aOnR-Hp0trtzCfrSB6z01IOuxnnVo74g3DZFmnIRFxZlfXqTeu8H-aSFy4SXocieVWyz900URjZCKnzwrqdrFWVzpkZB11k49loUjGliZAB/w400-h300/20171104_125610.jpg" title="photo showing a clamp jaw slotted into a recess on the underside of the aluminum track" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">This tracksaw is cleverly extruded to have built-in channels for clamps</td></tr>
</tbody></table>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQ5_erS0Ci3h7YGzL0-mLeIxicrgjNfOc05CFc0Ihr2elTatOYqy8n3QkB2DsBDU17xvqOWmiTO0bwT2l_11ogARRPP4D5myFPMzbsH4L-aZmAWjCgmicVled510K3nmtisE5X3wScaEjd/s1600/20171104_133606.jpg" style="margin-left: auto; margin-right: auto;"><img alt="a photo of the tabletop on sawhorses, with dowel plugs, measuring tools, and a notebook scattered on top." border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQ5_erS0Ci3h7YGzL0-mLeIxicrgjNfOc05CFc0Ihr2elTatOYqy8n3QkB2DsBDU17xvqOWmiTO0bwT2l_11ogARRPP4D5myFPMzbsH4L-aZmAWjCgmicVled510K3nmtisE5X3wScaEjd/w640-h480/20171104_133606.jpg" title="a photo of the tabletop on sawhorses, with dowel plugs, measuring tools, and a notebook scattered on top." width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Planning phase</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><img alt="a tracksaw track is a long, narrow aluminum plate with a rail to cut straight for long distances" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoRpflFd_QUkPT6FG7kqvL2Xca5dlJ-o86STZ_vgR7LMmvgOu7VB2CTEsNFXM-GOkLkKZt2A7DPubFbsVVLo_2d-ypviDjALsuXL9JrvoXvSjsx6iIA7fmdTunF3PJWDW_sCD-VsbgmBrp/w640-h480/20171104_163357.jpg" style="margin-left: auto; margin-right: auto;" title="a tracksaw track is a long, narrow aluminum plate with a rail to cut straight for long distances" width="640" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The tracksaw track also makes a great straight-edge guide for the router</td></tr>
</tbody></table>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoRpflFd_QUkPT6FG7kqvL2Xca5dlJ-o86STZ_vgR7LMmvgOu7VB2CTEsNFXM-GOkLkKZt2A7DPubFbsVVLo_2d-ypviDjALsuXL9JrvoXvSjsx6iIA7fmdTunF3PJWDW_sCD-VsbgmBrp/s1600/20171104_163357.jpg" style="margin-left: 1em; margin-right: 1em;"></a><br /></div>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgoRpflFd_QUkPT6FG7kqvL2Xca5dlJ-o86STZ_vgR7LMmvgOu7VB2CTEsNFXM-GOkLkKZt2A7DPubFbsVVLo_2d-ypviDjALsuXL9JrvoXvSjsx6iIA7fmdTunF3PJWDW_sCD-VsbgmBrp/s1600/20171104_163357.jpg" style="margin-left: 1em; margin-right: 1em;"></a><br />
I routed both shoulder-depth and tongue-depth tenons, then flipped the tabletop over and did the same on the other side. I then used a saw to form the tongues. Luckily for me, this process cut out the tear-out on the outer edges of the tabletop and let me hide my bad technique!<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgL5F4evMbuGBhzfHn2uu3c_fQ9_L9SraAxt44iDrm2aeZ91Eay4IXJe7-Wp8ZrMGVyv37LFUwqNzws9eLL5VaW1BEsDzb88WL9yi_JOGizryh4lBQev6TfHwH4WpueBQsYtyLj8PN_t8DL/s1600/20171110_112514.jpg" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img alt="photo showing some splitting in the wood on the outer edge of a tenon" border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgL5F4evMbuGBhzfHn2uu3c_fQ9_L9SraAxt44iDrm2aeZ91Eay4IXJe7-Wp8ZrMGVyv37LFUwqNzws9eLL5VaW1BEsDzb88WL9yi_JOGizryh4lBQev6TfHwH4WpueBQsYtyLj8PN_t8DL/w320-h240/20171110_112514.jpg" title="photo showing some splitting in the wood on the outer edge of a tenon" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJYP_7oXwkCwVurHtmpvwKrcdzDTUbQgAW_IfjoNygWM56ioz1Ll5hwRL01zmxNHaDu-R8H-ia-EX_k3aOX8stLzBzfaPq0hTqokS76xN9YnPU2XBVkDtXrIulT2mukprHy9L-teJvXdxD/s1600/20171110_121551.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="sawing off the outer edges creates square, clean surfaces" border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJYP_7oXwkCwVurHtmpvwKrcdzDTUbQgAW_IfjoNygWM56ioz1Ll5hwRL01zmxNHaDu-R8H-ia-EX_k3aOX8stLzBzfaPq0hTqokS76xN9YnPU2XBVkDtXrIulT2mukprHy9L-teJvXdxD/w300-h400/20171110_121551.jpg" title="sawing off the outer edges creates square, clean surfaces" width="300" /></a></div>
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Because my mortises were cut using a routing bit, I needed to round off the sides of the tongues. I did this with a coarse file. The process was very trial-and-error, but eventually both parts fit snug.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMfLIxtMj4NUsOw7nczlOvVbq_Avx6n42fXJzqTd4o0bWDyFidPS8IIJEiqhdy4SrwUmn62HCnqe9HO9RZH-lmHdjWyUfJ_TmrvmikIOAo0YrsVY7_F3VhG9JA7WPBkr2V_THrbVb7viAq/s1600/20171114_184039.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="photo of the tabletop with four wooden tongues ready to slot into the breadboard pockets" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMfLIxtMj4NUsOw7nczlOvVbq_Avx6n42fXJzqTd4o0bWDyFidPS8IIJEiqhdy4SrwUmn62HCnqe9HO9RZH-lmHdjWyUfJ_TmrvmikIOAo0YrsVY7_F3VhG9JA7WPBkr2V_THrbVb7viAq/w480-h640/20171114_184039.jpg" title="photo of the tabletop with four wooden tongues ready to slot into the breadboard pockets" width="480" /></a></div>
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Once the breadboard was attached, I drilled the 3 dowel holes that need to become slots (to avoid overconstraint). One hole is left for later, because it remains circular. Drill bit used is a forstner bit, which produces the crispest edges.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhr2-yHxAKEfDSBKThcqFGe1atmrgSe_13w-TywTzDM9E54Q1w8u3-8KLTyxn_M_P_njiG81Y1UIO3U2FhsZWZ-jh-k4Js5TOUvz84WMZ-wJ2nlorCGt2jHGHzC-J5R_MuUEvxtFfMEDwGb/s1600/20171116_172725.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="holes are drilled through the breadboard-tabletop assembly before enlarging the tenon holes into slots." border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhr2-yHxAKEfDSBKThcqFGe1atmrgSe_13w-TywTzDM9E54Q1w8u3-8KLTyxn_M_P_njiG81Y1UIO3U2FhsZWZ-jh-k4Js5TOUvz84WMZ-wJ2nlorCGt2jHGHzC-J5R_MuUEvxtFfMEDwGb/w480-h640/20171116_172725.jpg" title="holes are drilled through the breadboard-tabletop assembly before enlarging the tenon holes into slots." width="480" /></a></div>
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Then I pried the breadboard off again. Drilling dowel holes through both breadboard and tabletop in one operation ensures that my slots are located in the right place.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQY9xF2ougbZf9nG5VWxZltL_hL6O21Zu7XaR7d403draNAGxEiT7Fvzdn65nZN0hZdR8JUkmmknL3beuxbXzfDhV5qu4og1o-O-e0pXSmwEI2fwLt8dqf0ot_ViFyMs_fBvhZLnoq1HDJ/s1600/20171114_202319.jpg"><img alt="photo of tabletop with breadboard removed, showing holes drilled into three of the tenons" border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQY9xF2ougbZf9nG5VWxZltL_hL6O21Zu7XaR7d403draNAGxEiT7Fvzdn65nZN0hZdR8JUkmmknL3beuxbXzfDhV5qu4og1o-O-e0pXSmwEI2fwLt8dqf0ot_ViFyMs_fBvhZLnoq1HDJ/w480-h640/20171114_202319.jpg" title="photo of tabletop with breadboard removed, showing holes drilled into three of the tenons" width="480" /></a></div>
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After creating slots with a round file, I reattached the breadboard, pounded in dowels, then cut them flush. I only added glue to the uppermost section of the dowel - having the dowels glued to the tongues would make the slots useless.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZqafL899Sj_wShUoK-DfZsIjgMdfcTekwQcTQCPXlPBVGFMnLamCMZOXR0ccVeowuBh0Bn9U82WTe208ndcUpxLOTVn3x6yCU0q0Jnn92BTxXx46660TZH3bFeUqMGEnli2oGyvP8JB2L/s1600/20171115_175049.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="cutting the excess dowel ends with a hand saw" border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZqafL899Sj_wShUoK-DfZsIjgMdfcTekwQcTQCPXlPBVGFMnLamCMZOXR0ccVeowuBh0Bn9U82WTe208ndcUpxLOTVn3x6yCU0q0Jnn92BTxXx46660TZH3bFeUqMGEnli2oGyvP8JB2L/w300-h400/20171115_175049.jpg" title="cutting the excess dowel ends with a hand saw" width="300" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpQscTw4B3cz6AguJIjdSIFk18HU1urfqeshblRDunZhNXjQDGfG_WRKStdJlGpz5LPQx8j3WVyI5CWaqJjhxm_slRpVXhh_H5Te783ETR_hLUp-TuDDvP-1R5dHG08fCYF3XNwfYiAjB_/s1600/20171116_173521.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="tenons with holes enlarged into oblong slots" border="0" data-original-height="1600" data-original-width="1200" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjpQscTw4B3cz6AguJIjdSIFk18HU1urfqeshblRDunZhNXjQDGfG_WRKStdJlGpz5LPQx8j3WVyI5CWaqJjhxm_slRpVXhh_H5Te783ETR_hLUp-TuDDvP-1R5dHG08fCYF3XNwfYiAjB_/w300-h400/20171116_173521.jpg" title="tenons with holes enlarged into oblong slots" width="300" /></a></div>
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State of the tabletop! Left side is waiting for glue to dry before cutting them with the flush-cut saw.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivhRlrJfcRc1L1pi5D9nY26k3U3fODInQF8khBv3ZJUud8OedebSLLxLUD3uWv0MP0IFjQkpSvYPUtE8VUAtanTOH_8dBLp5woAxab_yXWJAmEMhhLsDC0SwO0C_AZgWOl482k0HPPIIJS/s1600/20171116_175818.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="tabletop with one breadboard's dowels cut flush" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEivhRlrJfcRc1L1pi5D9nY26k3U3fODInQF8khBv3ZJUud8OedebSLLxLUD3uWv0MP0IFjQkpSvYPUtE8VUAtanTOH_8dBLp5woAxab_yXWJAmEMhhLsDC0SwO0C_AZgWOl482k0HPPIIJS/w640-h480/20171116_175818.jpg" title="tabletop with one breadboard's dowels cut flush" width="640" /></a></div>
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I waited a day for glue to dry, then got Coby and other members of the HobbyShop to help me maneuver this tabletop to the thickness sander. That tool was an immense time-saver, turning a roughly multiple-day sanding job into 3 hours of work.<br />
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After cleaning up sawdust, I applied two coats of satin wipe-on polyurethane (1000-grit sanding between coats). The frame parts got one coat.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7zg7p8Qnkg05pGrRWRFk7KNacjey7CC_j-vzHRA1EiCJEHEglkhjkM1iuY9Xr_1Cq-BSyGvJtXBjueBTP3gkJQBZGi2DAqnJgcVh3_m8TXtel8qN9uNan-Hf1XOmzDtjPydVHfsCsYWJE/s1600/20171118_140332.jpg" style="margin-left: auto; margin-right: auto;"><img alt="polyurethane increases contrast in the wood grain. The end grain of the dowels becomes much darker than the surrounding wood." border="0" data-original-height="1600" data-original-width="1200" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7zg7p8Qnkg05pGrRWRFk7KNacjey7CC_j-vzHRA1EiCJEHEglkhjkM1iuY9Xr_1Cq-BSyGvJtXBjueBTP3gkJQBZGi2DAqnJgcVh3_m8TXtel8qN9uNan-Hf1XOmzDtjPydVHfsCsYWJE/w480-h640/20171118_140332.jpg" title="polyurethane increases contrast in the wood grain. The end grain of the dowels becomes much darker than the surrounding wood." width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Revealing the pretty colors is the best part!</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhoxvCg9CF6D6WJYaShIhLdxx6Kvw6SQVfPrSs5C7MgSw_7iAKIoDWWPAyx3L8VTeDYzX82Md74hyVi7Q8RI-agucSo-uIpQwd8DLzr99cVrxUU97OP9k35bNBBs4d2XWLgpEviB9RlHriT/s1600/20171118_160237.jpg" style="margin-left: auto; margin-right: auto;"><img alt="table components stacked near each other for air drying" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhoxvCg9CF6D6WJYaShIhLdxx6Kvw6SQVfPrSs5C7MgSw_7iAKIoDWWPAyx3L8VTeDYzX82Md74hyVi7Q8RI-agucSo-uIpQwd8DLzr99cVrxUU97OP9k35bNBBs4d2XWLgpEviB9RlHriT/w640-h480/20171118_160237.jpg" title="table components stacked near each other for air drying" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">All parts finished and drying</td></tr>
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I never understood why most woodworkers immediately paint or stain their pine/fir pieces. I actually really like the warm golden color.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJV12CT7UNAFdNmwLlaCP2LjKgI5rMGGjom1Q83bqGv9Cegq4QiXQZS45h5mSF0MO8aGw0-J3d02gkenxfry7_c3w6-0rhNbFtQGqFiDkwNQPNYQr0Tz9MYfeLa2H3GqKB5IhBYFOcxZya/s1600/20171118_160244.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="top view of tabletop showing off the matte sheen from the polyurethane" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJV12CT7UNAFdNmwLlaCP2LjKgI5rMGGjom1Q83bqGv9Cegq4QiXQZS45h5mSF0MO8aGw0-J3d02gkenxfry7_c3w6-0rhNbFtQGqFiDkwNQPNYQr0Tz9MYfeLa2H3GqKB5IhBYFOcxZya/w640-h480/20171118_160244.jpg" title="top view of tabletop showing off the matte sheen from the polyurethane" width="640" /></a></div>
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Once dry, these pieces all got bundled into a hatchback by my tetris-genius roommate and unloaded into our kitchen. I assembled this table in an evening, where the longest step was centering the tabletop over the frame. Tools required: screwdrivers (and drill because I'm lazy) and pliers.</div>
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A two-month project: done!</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFiOk9ZE_USz3jpJOAbUxZGwgoWV5Ln3K3XC4WKx02nNgzI5OyvD6KS7FTec7xmlWEvLyKA6uaJLaJGVlyo9ubkh_7Wpd9oaZ6Pci4LcDEbdRPNyFk8uwiU5HzUdBNlBh_AQa0KJfnAey8/s1600/20171123_011501.jpg" style="margin-left: auto; margin-right: auto;"><img alt="underside of the assembled table showing the tabletop attached to the apron with screw-in clips" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFiOk9ZE_USz3jpJOAbUxZGwgoWV5Ln3K3XC4WKx02nNgzI5OyvD6KS7FTec7xmlWEvLyKA6uaJLaJGVlyo9ubkh_7Wpd9oaZ6Pci4LcDEbdRPNyFk8uwiU5HzUdBNlBh_AQa0KJfnAey8/w640-h480/20171123_011501.jpg" title="underside of the assembled table showing the tabletop attached to the apron with screw-in clips" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Unclear what's going on with the whitebalance in this/next picture</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinMKHl3dq-RCVfJa9P2T6hTsPiGljsR0oj-yZvUleGMtzRKDlvwupgVcMqqQh-KqFWsbXVyXK_JYfE6Snn6_-HdvAh2QGrb7FJULGerUM3Mt9xdukPDgH1KqtHY6Tz3YHJdcrSOean4f57/s1600/20171123_011426.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo of table in the author's kitchen" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEinMKHl3dq-RCVfJa9P2T6hTsPiGljsR0oj-yZvUleGMtzRKDlvwupgVcMqqQh-KqFWsbXVyXK_JYfE6Snn6_-HdvAh2QGrb7FJULGerUM3Mt9xdukPDgH1KqtHY6Tz3YHJdcrSOean4f57/w640-h480/20171123_011426.jpg" title="photo of table in the author's kitchen" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Assembled table!</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUutYkSh5qipI87Yw1zPlS8HXLQLKn49JL1VBzucWygSt7xH_vINBpB8_iGsM21-qMwr9TzKG_OZpY31bqAgrTIw6bSRYXGAK89rjQaepqqC1nuh8MxiRKuhSgY2xG61UllkrhIIWyTeoq/s1600/IMG_2115.JPG" style="margin-left: auto; margin-right: auto;"><img alt="photo of table with platters of thanksgiving foods arrayed for serving" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjUutYkSh5qipI87Yw1zPlS8HXLQLKn49JL1VBzucWygSt7xH_vINBpB8_iGsM21-qMwr9TzKG_OZpY31bqAgrTIw6bSRYXGAK89rjQaepqqC1nuh8MxiRKuhSgY2xG61UllkrhIIWyTeoq/w640-h480/IMG_2115.JPG" title="photo of table with platters of thanksgiving foods arrayed for serving" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Finished in time for Thanksgiving</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj49lQtVmTf2zlw4LN_kXu95NeYTZL24kTK8iUIov4KJfFRDUQJxvG-znxdrud9vGJutL2pHIdY5L8VwPR0_QPUQVCVfkJ51Gp2XdwR0qobQL5K_YUj1KNc4FQcoXXUZAmt3mO7YsuJPiLB/s1600/20171123_104429.jpg" style="margin-left: auto; margin-right: auto;"><img alt="photo of the table with breakfast laid out on it" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj49lQtVmTf2zlw4LN_kXu95NeYTZL24kTK8iUIov4KJfFRDUQJxvG-znxdrud9vGJutL2pHIdY5L8VwPR0_QPUQVCVfkJ51Gp2XdwR0qobQL5K_YUj1KNc4FQcoXXUZAmt3mO7YsuJPiLB/w640-h480/20171123_104429.jpg" title="photo of the table with breakfast laid out on it" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">celebratory coffee and cheesecake</td></tr>
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<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-21144480486595664042017-10-23T18:00:00.001-04:002020-08-12T01:17:43.386-04:00Art and Pickles<div class="separator" style="clear: both; text-align: center;">
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Made some art for a friend, made some pickles for me (and roommates!)<br />
Art is chalk pastel on scrap matboard.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQ-qukE7TCwsBMFEQSKeUO84fqE86WsOw_Bg9GpN9MQCHYDh0E5btHb-XBXO8Rg5y31eGEMOFlsYGTfLPUsqok0h9_dGT5KMK_5p4teUWEZCffDjidpz-vTshVBzGES8AVxbIHFwxuC923/s1600/20171006_003526.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="multicolor drawing of a forehead and wispy mohawk" border="0" data-original-height="1026" data-original-width="1600" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQ-qukE7TCwsBMFEQSKeUO84fqE86WsOw_Bg9GpN9MQCHYDh0E5btHb-XBXO8Rg5y31eGEMOFlsYGTfLPUsqok0h9_dGT5KMK_5p4teUWEZCffDjidpz-vTshVBzGES8AVxbIHFwxuC923/w400-h256/20171006_003526.jpg" title="multicolor drawing of a forehead and wispy mohawk" width="400" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPsZHq2NmdyClHL1-JUlbrKXdlS3mueiE-TF90DWLmuYlxyE9L9hRwdnkZ0HvSao2UR6AsidXhHC0inpt-TFxEK0uc8yRsVAcougZ8lENgCtseuTHmqJ_6Kv2-H4q7IgE9d43ks98Gss0x/s1600/20171006_003549.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="drawing of two arms firespinning with devil sticks, a type of juggling prop" border="0" data-original-height="1587" data-original-width="1600" height="396" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhPsZHq2NmdyClHL1-JUlbrKXdlS3mueiE-TF90DWLmuYlxyE9L9hRwdnkZ0HvSao2UR6AsidXhHC0inpt-TFxEK0uc8yRsVAcougZ8lENgCtseuTHmqJ_6Kv2-H4q7IgE9d43ks98Gss0x/w400-h396/20171006_003549.jpg" title="drawing of two arms firespinning with devil sticks, a type of juggling prop" width="400" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpQKlKmQ4JwSQjF4_LshcVRuoofuImcpwVPt2GOCUbUA9IEwFY7wKx4OcRBLTLigWZlI9p96jnE52FwXaRkM3vKk7M7wXZgGuxSLB7iYleiKZCe9g50FU_VQN6fm-y07CBNhUL-aGMlxjJ/s1600/20171006_003612.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="drawing of a wooden spaceship against a galaxy background" border="0" data-original-height="1269" data-original-width="1600" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpQKlKmQ4JwSQjF4_LshcVRuoofuImcpwVPt2GOCUbUA9IEwFY7wKx4OcRBLTLigWZlI9p96jnE52FwXaRkM3vKk7M7wXZgGuxSLB7iYleiKZCe9g50FU_VQN6fm-y07CBNhUL-aGMlxjJ/w400-h316/20171006_003612.jpg" title="drawing of a wooden spaceship against a galaxy background" width="400" /></a><br />This one is derived from some panels of <a href="https://imagecomics.com/comics/series/saga" target="_blank">Saga, an excellent (but super NSFW) comic series</a>.</div>
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Pickles are various kinds of fermented or refrigerator pickles.<br />
(avoiding botulism in canned pickles is too much effort to bother with)<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzq05L954Rdyn5wqH7XCZ0pi_Jdi5YhX5mmpbZpkgeNmZKEQ5CrHgNdcGr5JOrWywCwroUAUHsKe-m9Xm6Xy3NzH3voEO_T11Vq60By29FFz1uoWGuA0p4gDNboTToWxjmFj94RRLuJsRf/s1600/20171021_184944.jpg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img alt="a bowl of finished pickles, showing a red radish slice cut into a flower shape" border="0" data-original-height="1600" data-original-width="1254" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzq05L954Rdyn5wqH7XCZ0pi_Jdi5YhX5mmpbZpkgeNmZKEQ5CrHgNdcGr5JOrWywCwroUAUHsKe-m9Xm6Xy3NzH3voEO_T11Vq60By29FFz1uoWGuA0p4gDNboTToWxjmFj94RRLuJsRf/w250-h320/20171021_184944.jpg" title="a bowl of finished pickles, showing a red radish slice cut into a flower shape" width="250" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5RaufEqe8cip67vF7RjLVC6i9a6pmCOwBplJHs9fa2QVl8XYeYShSBz4e3VodNAp3cwAqXoEnFKs_KzOCxYARsn52WfudNfDR9tHwPwd7HfWMWqe7XxmKvlGcyohfgc-SD9n-qVBr_D14/s1600/20171023_003003.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="jars of daikon (left) and carrot/radish (middle) quick pickles, and napa cabbage kimchi (right)" border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5RaufEqe8cip67vF7RjLVC6i9a6pmCOwBplJHs9fa2QVl8XYeYShSBz4e3VodNAp3cwAqXoEnFKs_KzOCxYARsn52WfudNfDR9tHwPwd7HfWMWqe7XxmKvlGcyohfgc-SD9n-qVBr_D14/w320-h240/20171023_003003.jpg" title="jars of daikon (left) and carrot/radish (middle) quick pickles, and napa cabbage kimchi (right)" width="320" /></a></div>
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I cut the radishes into flowers for one of the carrot-radish jars, but the small red radishes were a little too delicate and most of the slices lost their petals in the process.</div>
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<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-85960178986126901812017-10-22T22:44:00.002-04:002020-08-26T22:44:09.138-04:00Calipers Box round 2 (post 1/2)<div style="clear: both; text-align: left;">
Still working on box#2! (I borked my leg and picked up a dining-table project, so this is still ongoing)</div>
This means I have the opportunity to take more photos of the steps I missed last time.<br />
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After <a href="http://www.avamakesthings.com/2017/05/free-hand-milling-calipers-pocket.html">milling out the calipers profile, etch-a-sketch style</a> and seating the tool in the bottom half, I traced out the remainder on the top blank. This one needed a void for the round bezel-dial and not much else.<br />
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Here I'm also matching up the ends to mark where the hinges go.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXbR_Yyegrr2_C2MTrwWf1PniJd8DBZhNA-2Vm2wFSP1wZa2RxVDAB2bcado0lvU6WW0b4VVCrSvZPB2m4vVG9J8hfDvVDX2VQ4wZEO76nhZjkb8oItOYBXSbuJk8NUv_nWH4Pp6EJFUjs/s1600/20170708_165314.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="walnut board with pocket in the shape of callipers and pencil markings for planned hinge pockets" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjXbR_Yyegrr2_C2MTrwWf1PniJd8DBZhNA-2Vm2wFSP1wZa2RxVDAB2bcado0lvU6WW0b4VVCrSvZPB2m4vVG9J8hfDvVDX2VQ4wZEO76nhZjkb8oItOYBXSbuJk8NUv_nWH4Pp6EJFUjs/w640-h480/20170708_165314.jpg" title="walnut board with pocket in the shape of callipers and pencil markings for planned hinge pockets" width="640" /></a></div>
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Milling out the bezel void with a ball endmill for extra aesthetics. Hinge and magnet mortises happened afterwards.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZuc0XROuEoet0lky-ZcyAclX1XcSisNRpUUyHQSLYsXDRiZ3PBJFfWWXO-8RtvMxsRXbGUFDLv6usMqjLLoDGPVUC7xjLyRepVi6Hp9do0bKyHDlboSJVkfZRTdrDiPKqXUZmstSekKgh/s1600/20170812_140510.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="circular pocket with rounded bottom edge done with conversational CNC mill" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZuc0XROuEoet0lky-ZcyAclX1XcSisNRpUUyHQSLYsXDRiZ3PBJFfWWXO-8RtvMxsRXbGUFDLv6usMqjLLoDGPVUC7xjLyRepVi6Hp9do0bKyHDlboSJVkfZRTdrDiPKqXUZmstSekKgh/w640-h480/20170812_140510.jpg" title="circular pocket with rounded bottom edge done with conversational CNC mill" width="640" /></a><br />
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I was lazy and decided to lasercut all my inlay pieces. They are 3/32" thick and would've been a pain.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCkHylG9gLVRJAAiL8G1hGi7MrqhTQiLHimNylZwVP5kgjZXIkXMFtslj8qsSFLpzmK8YP0qBD5qOG_5ciLwm1KlRiEUFc1MGUj0WXmHyqrIB11qHZmWn9jPVt7XTMXXCYilABBHKdlptV/s1600/20170708_165301.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="pocket for closure magnet with matching lasercut pine inlay cover" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCkHylG9gLVRJAAiL8G1hGi7MrqhTQiLHimNylZwVP5kgjZXIkXMFtslj8qsSFLpzmK8YP0qBD5qOG_5ciLwm1KlRiEUFc1MGUj0WXmHyqrIB11qHZmWn9jPVt7XTMXXCYilABBHKdlptV/w640-h480/20170708_165301.jpg" title="pocket for closure magnet with matching lasercut pine inlay cover" width="640" /></a></div>
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<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-41088542498887243592017-08-27T20:24:00.008-04:002020-08-26T23:47:32.842-04:002015 EC Rollercoaster Construction<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4UOZio98QD9xX2qjdjIc3h8Gi4GTly5i_4RJLkyD1l32x60gQajLc8zHu_FY6Yc0HM3BSe-Rl6XXVsjkwMrZO2whwOgVMCC5ZD6jM_FIu-h2z7jp8mVYMZzMoMw0SUDb7tYzCZCWDKPqQ/s1600/coasterbostonglobe.png" style="margin-left: 1em; margin-right: 1em;"><img alt="Boston Globe article with photo of rollercoaster and headline "Why yes, that IS a roller coaster on MIT's campus"" border="0" data-original-height="1600" data-original-width="1598" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi4UOZio98QD9xX2qjdjIc3h8Gi4GTly5i_4RJLkyD1l32x60gQajLc8zHu_FY6Yc0HM3BSe-Rl6XXVsjkwMrZO2whwOgVMCC5ZD6jM_FIu-h2z7jp8mVYMZzMoMw0SUDb7tYzCZCWDKPqQ/w638-h640/coasterbostonglobe.png" title="Boston Globe article with photo of rollercoaster and headline "Why yes, that IS a roller coaster on MIT's campus"" width="638" /></a></div>
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<span><a name='more'></a></span>It's rollercoaster season again! If you're around MIT campus this week, the 2017 coaster will be up and running (should be completed tonight, actually!)<br />
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So with that, and me being laid up in bed with a busted knee... I should hurry up and do a construction post about the <a href="http://www.avamakesthings.com/2015/10/east-campus-rollercoaster-2015.html">2015 rollercoaster!</a> (only two years delayed........)<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwk4B2UIna1gCTWsMJ4-2ayKw_q3sEFI0RxN6q0Bui89uPOHt8hqtWAcsUDqoBpPkGFlZcc2_7vzkdnz-PXhM2Cfil4JBP4X7jxTqm7OO69WSRZv828dIs3NQZK4lqUGarSgrPHz4_hO8c/s1600/20150819_165314.jpg" style="margin-left: auto; margin-right: auto;"><img alt="three students digging with shovels" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwk4B2UIna1gCTWsMJ4-2ayKw_q3sEFI0RxN6q0Bui89uPOHt8hqtWAcsUDqoBpPkGFlZcc2_7vzkdnz-PXhM2Cfil4JBP4X7jxTqm7OO69WSRZv828dIs3NQZK4lqUGarSgrPHz4_hO8c/w360-h640/20150819_165314.jpg" title="three students digging with shovels" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Digging holes for a cinderblock/pier block foundation</td></tr>
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East Campus has the best back-to-school traditions. Freshman at MIT get to pick which dorms they want to live in, and each dorm has its own character it wants to show off. At East Campus?</div>
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"We're cool people! Build cool things with us!"</div>
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So that's where the tradition of building large wooden structures comes from. The upperclassmen come back at the end of summer, set down luggages, and immediately get to work. From groundbreaking (above) to wiring lights and putting together a DJ set, all time and effort is devoted to making a student-led, student-made hell of a dance party (the coaster, the fort, all of it is ostensibly for this dance party)... all within around 10 days! Then everyone admires the fruits of their efforts for around another week, and then the following weekend it all gets deconstructed before classes start.</div>
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The story of an East Campus rollercoaster, of course, begins way before construction starts. In January, about 7months before, several enterprising groups of students propose projects they want to lead. Sometimes these include a rollercoaster (~2005-2008; 2014-2015; 2017), almost always they include a wooden fort, <a href="http://www.avamakesthings.com/2017/02/2016-ec-clubhouse-construction.html">sometimes they're mildly different</a>. The student chairs in charge of organizing REX (the back-to-school-event), select projects to fit a budget and get to work planning logistics and fundraising. The project leaders get to work too.</div>
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<iframe allowfullscreen="" alt="Computer rendering of roller coaster design" frameborder="0" height="315" src="https://www.youtube.com/embed/7KbkV1xvrl0" width="560"></iframe><br /></div>
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There's drawings and models and acceleration simulations to be made, and a whole bunch of math. Luckily most of the structural calculations can take advantage of years of tradition with previous wooden projects. The few novel calculations for the 2015 coaster were to figure out how to safely handle a 90deg drop (safety both with regards to acceptable G-forces on the rider and structural loading on the track)</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi8XKr7YcdqmX3mzkcccncqzTP4NfsL6D2uGxDCvOobYyYh7u-EIfCoOcDJYChm9nuI-5siQJZynwpk1CZEMQvnoJ7gmda_G-Hj6owwDUtbP3XrwbcnUecfwtBgFQc1BGDYw0l8c80KK-ei/s1600/Capture.JPG" style="margin-left: auto; margin-right: auto;"><img alt="spreadsheet calculations for allowable yield and bending stress" border="0" data-original-height="1223" data-original-width="1600" height="488" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi8XKr7YcdqmX3mzkcccncqzTP4NfsL6D2uGxDCvOobYyYh7u-EIfCoOcDJYChm9nuI-5siQJZynwpk1CZEMQvnoJ7gmda_G-Hj6owwDUtbP3XrwbcnUecfwtBgFQc1BGDYw0l8c80KK-ei/w640-h488/Capture.JPG" title="spreadsheet calculations for allowable yield and bending stress" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Some examples of the structural calculations</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjycJUZdql8MePvfljZgEQ5EOQ1tf0RaQwLsgcXpLRz26i2AbykTbD0y6JV_tl6q9RLYODZIJImJlalUUhqwGvf5dZ5bk3K_pFJVzYMbwhUpTGg6U_TeISV7_a4LW5kHPZyPiM8YzBPhfEL/s1600/paper7.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="dimensioned engineering drawing of roller coaster" border="0" data-original-height="785" data-original-width="1600" height="312" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjycJUZdql8MePvfljZgEQ5EOQ1tf0RaQwLsgcXpLRz26i2AbykTbD0y6JV_tl6q9RLYODZIJImJlalUUhqwGvf5dZ5bk3K_pFJVzYMbwhUpTGg6U_TeISV7_a4LW5kHPZyPiM8YzBPhfEL/w640-h312/paper7.JPG" title="dimensioned engineering drawing of roller coaster" width="640" /></a></div>
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By the end of spring, the designs are done and drawings are ready to send off. Rollercoasters have to get approval from MIT EHS, a structural engineering PE, an architect, Cambridge Fire Dept, and City of Cambridge (it's classified as a temporary building). The REX chairs do a fantastic job of organizing the meetings and getting everyone convinced; over the summer they and the project leads get to sit in a ton of meetings.</div>
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Anyway once the designs and BOMs are finalized, safety plans and assembly instructions (think lego manuals) get written up, and everyone gets hyped for rush to start!</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjE8JFDuQRmbOEWCsCO_uQK_jXvM2Kl53i-jxTBg1CJpZ-TMACaYzFEpUCkX9tUvQh8jM3-8ax6gCpAIlR-faB7xwPPHHyUzs2hq2037458TX9FowjE6emTMX9L9oGotJPEFRfNVJk9XMl_/s1600/20150822_163951.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="vertical posts and ground-floor spandrel beams installed" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjE8JFDuQRmbOEWCsCO_uQK_jXvM2Kl53i-jxTBg1CJpZ-TMACaYzFEpUCkX9tUvQh8jM3-8ax6gCpAIlR-faB7xwPPHHyUzs2hq2037458TX9FowjE6emTMX9L9oGotJPEFRfNVJk9XMl_/w360-h640/20150822_163951.jpg" title="vertical posts and ground-floor spandrel beams installed" width="360" /></a></div>
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The loading tower is the first structure to go up. Its placement determines the location and orientation of the rest of the rollercoaster, and it also requires the highest concentration of manpower. </div>
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The 2014 and 2015 towers were attached to the fort. The 2017 coaster tower is separate.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9AiZAbxbBUiX4iJXeFQg7SK66ZdOYXOHhb_PKsPqE18QsYZsuMnOLb3d1aI23naGEz95E9ASomU62oE6oBvY0bkUazHZ1OVzjco2etqjd5jO-SbnJLlLreM2-J57wDeqqWmvJGnuqsOQR/s1600/paper4.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="non-dimensioned engineering drawings of main two storey tower" border="0" data-original-height="1240" data-original-width="1600" height="494" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9AiZAbxbBUiX4iJXeFQg7SK66ZdOYXOHhb_PKsPqE18QsYZsuMnOLb3d1aI23naGEz95E9ASomU62oE6oBvY0bkUazHZ1OVzjco2etqjd5jO-SbnJLlLreM2-J57wDeqqWmvJGnuqsOQR/w640-h494/paper4.JPG" title="non-dimensioned engineering drawings of main two storey tower" width="640" /></a></div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyFXbVfRZTPKHvFlFCNBd5ouU_iAl2PM5f5kOsQdspHai8FPcSN_cWDauvi-czyCZc5Vd6Nl8PDlugLAFZ7zwI5gtqHiz4bwOfgwMZQEC0dd71qLXHoNZR2ZgO6JtUQ7yR4x1OVzhjmgAt/s1600/20150825_210339.jpg" style="margin-left: auto; margin-right: auto;"><img alt="person on a ladder fastening bolts through vertical posts while another person stabilizes the ladder" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyFXbVfRZTPKHvFlFCNBd5ouU_iAl2PM5f5kOsQdspHai8FPcSN_cWDauvi-czyCZc5Vd6Nl8PDlugLAFZ7zwI5gtqHiz4bwOfgwMZQEC0dd71qLXHoNZR2ZgO6JtUQ7yR4x1OVzhjmgAt/w360-h640/20150825_210339.jpg" title="person on a ladder fastening bolts through vertical posts while another person stabilizes the ladder" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Starting to install 3rd floor spandrels</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCH2CH6IZDAvwMwN9ZmY0nVpLHsoJdnxvtCVeJNtL2tA6jXPfSbnxwauVvYfM6Nc3RoaPnsZVNI99plDDZeHsyscHgK2RrUgrg_oINjMveKJ8TMqp23-BUZFB2zfY4dPyAE6RfT4Vf_JAV/s1600/20150827_193540.jpg" style="margin-left: auto; margin-right: auto;"><img alt="towers with timber guardrails, one railing 21" above floor height and one 42" above floor height per OSHA guidelines" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCH2CH6IZDAvwMwN9ZmY0nVpLHsoJdnxvtCVeJNtL2tA6jXPfSbnxwauVvYfM6Nc3RoaPnsZVNI99plDDZeHsyscHgK2RrUgrg_oINjMveKJ8TMqp23-BUZFB2zfY4dPyAE6RfT4Vf_JAV/w360-h640/20150827_193540.jpg" title="towers with timber guardrails, one railing 21" above floor height and one 42" above floor height per OSHA guidelines" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">First things to go up on every floor are temporary safety railings.</td></tr>
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Once the third storey of the tower is done, then it's time to attach all of the frames. These frames were created while the project leads focused on the tower - they're good things to delegate and use to teach freshmen how to use power tools.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjW4eGBZlP9eGB8X97GyhICsQjyRHEXHdGe-87qxy8pVlqrEEuSKsE5LAgczrG4Oul9Wo6DzUxWpryX7ECh0QnTpQzShWDqCJgsDh715FYd12peTHomrnqLGz0lqb2P8-k-PeVoNH4FEIUR/s1600/paper3.JPG" style="margin-left: auto; margin-right: auto;"><img alt="engineering drawing with dimensions and parts list" border="0" data-original-height="1230" data-original-width="1600" height="492" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjW4eGBZlP9eGB8X97GyhICsQjyRHEXHdGe-87qxy8pVlqrEEuSKsE5LAgczrG4Oul9Wo6DzUxWpryX7ECh0QnTpQzShWDqCJgsDh715FYd12peTHomrnqLGz0lqb2P8-k-PeVoNH4FEIUR/w640-h492/paper3.JPG" title="engineering drawing with dimensions and parts list" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A representative frame's construction sheet</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipYLnK6CfZuv3GHSYVJP-hNS9x0vDBjcJLEAtpniS8_U7zaKDI0W-t8C7xsIi-EjgcGt-B-iaGbjHtIpC0bVotbRPcg6G8b0YGPN-V6Yr_VT2oQ-2darWBkCa7gdMYeNyRj5te81Ak47Bf/s1600/footprint.JPG" style="margin-left: auto; margin-right: auto;"><img alt="engineering drawing with planned distance to each main track support" border="0" data-original-height="1239" data-original-width="1600" height="494" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipYLnK6CfZuv3GHSYVJP-hNS9x0vDBjcJLEAtpniS8_U7zaKDI0W-t8C7xsIi-EjgcGt-B-iaGbjHtIpC0bVotbRPcg6G8b0YGPN-V6Yr_VT2oQ-2darWBkCa7gdMYeNyRj5te81Ak47Bf/w640-h494/footprint.JPG" title="engineering drawing with planned distance to each main track support" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Locations of each frame</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGFehi-bDN_zizT1RqfnIUGHhngdNmrKK8f2a0jDJLU3LlKWTULnasSyhMCsdvMKE5XXDYdmvhW0BEfUfKC24do-1uLwlQkNYf9i9ZFBCuL1S7V5shN-KOIT6l6BkQR9dyQJXWYDndGG1v/s1600/20150827_213812.jpg" style="margin-left: auto; margin-right: auto;"><img alt="students connecting main structural supports" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhGFehi-bDN_zizT1RqfnIUGHhngdNmrKK8f2a0jDJLU3LlKWTULnasSyhMCsdvMKE5XXDYdmvhW0BEfUfKC24do-1uLwlQkNYf9i9ZFBCuL1S7V5shN-KOIT6l6BkQR9dyQJXWYDndGG1v/w360-h640/20150827_213812.jpg" title="students connecting main structural supports" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Frame Assembly<br /><br /></td></tr>
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While frames are going up, track pieces start getting added to the coaster skeleton. Each track section is a simple 2x4 unit assembled with a jig - another good thing to use for teaching freshmen - and slide against the previous section just like a puzzlepiece. These sections interpolate the desired track curvature onto the rollercoaster frame.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgouTCgFBblwA-HjDM9MQJc8Ni6v6gD3IQ1N8ZNYWqC5W0EVttABecqd6LGzWXHhW1__jYUxdTInHpcHkxHG1L_Xs2Q-Ogj3pBQmfezomk6IfMRKCIXBeYXdSbN-dfZg7E-5_yxpWogImrQ/s1600/20150828_170244.jpg" style="margin-left: auto; margin-right: auto;"><img alt="students driving screws with hand drills" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgouTCgFBblwA-HjDM9MQJc8Ni6v6gD3IQ1N8ZNYWqC5W0EVttABecqd6LGzWXHhW1__jYUxdTInHpcHkxHG1L_Xs2Q-Ogj3pBQmfezomk6IfMRKCIXBeYXdSbN-dfZg7E-5_yxpWogImrQ/w360-h640/20150828_170244.jpg" title="students driving screws with hand drills" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Putting track sections on the vertical drop.</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0G6Ad7qmduNf7JyHows6Ds9VPhBcT_mDEls22DVAtY1xjCJAufq3E1ILFNEy1cc2_bET3KYpCbc3Yapwv-TprISYToi-7gDw5II09WFjHSyR9wKD3L303r1VPy1_HXL0KlDcXAcTtGaW_/s1600/paper2.JPG" style="margin-left: auto; margin-right: auto;"><img alt="dimensioned engineering drawing with parts list and requested quantity to build" border="0" data-original-height="1240" data-original-width="1600" height="494" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0G6Ad7qmduNf7JyHows6Ds9VPhBcT_mDEls22DVAtY1xjCJAufq3E1ILFNEy1cc2_bET3KYpCbc3Yapwv-TprISYToi-7gDw5II09WFjHSyR9wKD3L303r1VPy1_HXL0KlDcXAcTtGaW_/w640-h494/paper2.JPG" title="dimensioned engineering drawing with parts list and requested quantity to build" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Instruction sheet for a track section</td></tr>
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The track sections are first attached to the previous section with a single screw (allows it to pivot.) Then a vertical support is attached to determine angle before the rest of the screws are added. This ensures that the rough curvature of the track follows the original design.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQmNOV5t1ZhN6HD12yvy_17VxaGh3FpqvwrfOdBzWolRnpAB-e24bE-D68GxKKwWULQarFZixaUf8HF9ne2iPtSfRYLFOMFQma2HvcW0kcStR3HHVq6mfzuMNDXuRHuk2FuE6ra6IdGpXP/s1600/paper6.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="engineering drawing with estimated vertical heights of track supports" border="0" data-original-height="1250" data-original-width="1600" height="498" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjQmNOV5t1ZhN6HD12yvy_17VxaGh3FpqvwrfOdBzWolRnpAB-e24bE-D68GxKKwWULQarFZixaUf8HF9ne2iPtSfRYLFOMFQma2HvcW0kcStR3HHVq6mfzuMNDXuRHuk2FuE6ra6IdGpXP/w640-h498/paper6.JPG" title="engineering drawing with estimated vertical heights of track supports" width="640" /></a></div>
Once the rough curvature of the rollercoaster is established, multiple layers of plywood are tacked on to form the track. Other notable features of the rollercoaster include the work platforms that are not only useful during construction but also make safely dragging the cart back possible.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKrY4vPVexyYayNehC9rr_y7lalStHku6sEsvs6vhszVg7K0i4qQ1aCoeQAfwZnnOYh9M9O95GI3VtGNJz0gw_uPcGK3SJHuv0FoE8MgUSKYbjD1I6uQDfKEZLtL5XyiZJTH59tnUF2LdJ/s1600/paper8.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="engineering drawing with callouts "plywood attached to supports with 1-1/4" wood screws", "wheels overhang track by 3/4 inches", and "Guardrails installed on all work platforms 4' above the ground"" border="0" data-original-height="818" data-original-width="1600" height="326" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhKrY4vPVexyYayNehC9rr_y7lalStHku6sEsvs6vhszVg7K0i4qQ1aCoeQAfwZnnOYh9M9O95GI3VtGNJz0gw_uPcGK3SJHuv0FoE8MgUSKYbjD1I6uQDfKEZLtL5XyiZJTH59tnUF2LdJ/w640-h326/paper8.JPG" title="engineering drawing with callouts "plywood attached to supports with 1-1/4" wood screws", "wheels overhang track by 3/4 inches", and "Guardrails installed on all work platforms 4' above the ground"" width="640" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAZxqE9Vg1SCb3_kWX8tTemdGclvtZTfsx_iPZ9gCz0pnu4PMozTqnjMAXWE0dbnQfWkZnNPNGhJ2PY9tABwaK4HIlL4bkWzUEmdG1r2a6m8HSzJmK0bXXWSBz2ng-AH4xyaRwNZaCdeAc/s1600/paper5.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="engineering drawing with callouts "Track surface made from 3 layers of 5/16 inch plywood. Layers will be offset by 2 feet 8 inches in order to avoid lining up edges" and "2x4 cross beams every 18 inches along track"" border="0" data-original-height="1240" data-original-width="1600" height="496" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAZxqE9Vg1SCb3_kWX8tTemdGclvtZTfsx_iPZ9gCz0pnu4PMozTqnjMAXWE0dbnQfWkZnNPNGhJ2PY9tABwaK4HIlL4bkWzUEmdG1r2a6m8HSzJmK0bXXWSBz2ng-AH4xyaRwNZaCdeAc/w640-h496/paper5.JPG" title="engineering drawing with callouts "Track surface made from 3 layers of 5/16 inch plywood. Layers will be offset by 2 feet 8 inches in order to avoid lining up edges" and "2x4 cross beams every 18 inches along track"" width="640" /></a></div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrjpIh_boTrqWEcrj1TST7QUmdqGwisEZgnpIgsqGqifEoNAIgixNhtorg8FpQ3bDeh-mC0fqKE4p7g7jgliykAjvJsfV21T99ja0yMf3F-Z7XNuEDPZfQadEJMP0tYK9fRVnG9qa6H50R/s1600/20150829_014352.jpg" style="margin-left: auto; margin-right: auto;"><img alt="" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrjpIh_boTrqWEcrj1TST7QUmdqGwisEZgnpIgsqGqifEoNAIgixNhtorg8FpQ3bDeh-mC0fqKE4p7g7jgliykAjvJsfV21T99ja0yMf3F-Z7XNuEDPZfQadEJMP0tYK9fRVnG9qa6H50R/w360-h640/20150829_014352.jpg" title="" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Adding vertical supports to the track units. </td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPUz1a26rQhYXVVneh6s6_DMf-7AmlmsDiuNlLxpZWXEFxEJnKmv9GuHztnwQuQY-lfN_yEFKILMdaTrL70ZO-1fLnOH5lcWNH_MLNtjZfJNki5ie42012sUJOABkmBBth3O6ZNiuJkqu6/s1600/paper.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="" border="0" data-original-height="1243" data-original-width="1600" height="496" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPUz1a26rQhYXVVneh6s6_DMf-7AmlmsDiuNlLxpZWXEFxEJnKmv9GuHztnwQuQY-lfN_yEFKILMdaTrL70ZO-1fLnOH5lcWNH_MLNtjZfJNki5ie42012sUJOABkmBBth3O6ZNiuJkqu6/s640/paper.JPG" title="" width="640" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPil9sx2nXTy1jw77s_-h_LnyrDsj8zxtY2dnyECUXuQLZQbiqSBl1-vJlPLA6s4UCdKOE-Rh5oeYVa4k-6BqFQV4v0r_idtHT-vIfdgvgdXO7gj_8XX6Mti_a6OAzZvJ9bn-0fvUsLH6K/s1600/11921812_10205066847138723_7657729268504999725_o.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="image of the roller coaster cart after an unmanned trial run" border="0" data-original-height="900" data-original-width="1600" height="360" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPil9sx2nXTy1jw77s_-h_LnyrDsj8zxtY2dnyECUXuQLZQbiqSBl1-vJlPLA6s4UCdKOE-Rh5oeYVa4k-6BqFQV4v0r_idtHT-vIfdgvgdXO7gj_8XX6Mti_a6OAzZvJ9bn-0fvUsLH6K/w640-h360/11921812_10205066847138723_7657729268504999725_o.jpg" title="image of the roller coaster cart after an unmanned trial run" width="640" /></a><br />
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And that's the coaster! There's a good construction timelapse video of the fort and rollercoaster below.</div>
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<iframe allowfullscreen="" frameborder="0" height="315" src="https://www.youtube.com/embed/7iPUDKMWAkU" width="560"></iframe></div>
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(video credit: Banti Gheneti)</div>
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You might be wondering about the cart. The cart is an ridiculously-heavy wood and aluminum-plate contraption bolted to a bucket seat (5-point harness!)</div>
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I didn't have any pictures of it from REX, but I did take some afterwards when it was in storage.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdeGO5UkJIi484xXr6_g5v2q10JIqVK9eoHcJXuzevc4j0myziDcInabJ4QX8DLOb6Y_eKdiLGIG30kOA17sFxE92k-IdOYzTkskfrudFNLAegWNZQr4DwQuohQCKx7bPKjvmfwGz02mML/s1600/IMG_3704.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="wooden cart minus bucket seat" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjdeGO5UkJIi484xXr6_g5v2q10JIqVK9eoHcJXuzevc4j0myziDcInabJ4QX8DLOb6Y_eKdiLGIG30kOA17sFxE92k-IdOYzTkskfrudFNLAegWNZQr4DwQuohQCKx7bPKjvmfwGz02mML/w640-h480/IMG_3704.JPG" title="wooden cart minus bucket seat" width="640" /></a></div>
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The 2015 cart has a total of 8 wheels rolling on top of the track, along with 4 wheels beneath (to prevent the cart from flying off) and 4 on the outer edge (preventing skidding). The side wheels received extra abrasion protection via heat-shrunk soda bottles (a MITERS tradition).</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgReJvwdd3EAzyx2b_Jx9D7GF7r5XmYIB4cdqmod87ty5Y05ZxwbnBGr2AqWNta827rNmn8R19232LlziCSoGXDoI70r0UyhgCD1RazMFYv3L4pCegxArM7TjfZILLZCKtsxTSjSnX2_P7q/s1600/IMG_3705.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="close up view of wheels encased in a thick plastic film" border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgReJvwdd3EAzyx2b_Jx9D7GF7r5XmYIB4cdqmod87ty5Y05ZxwbnBGr2AqWNta827rNmn8R19232LlziCSoGXDoI70r0UyhgCD1RazMFYv3L4pCegxArM7TjfZILLZCKtsxTSjSnX2_P7q/w320-h240/IMG_3705.JPG" title="close up view of wheels encased in a thick plastic film" width="320" /></a></div>
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The cart clears the steep track curvature by having a bent frame, ~10deg total.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAvEAzfPiKXlw3SzWMIkNv14KylyR39XqX3JZ3VTIHhySNnymIuaDu1TOOd-gKjWiWhSydVkIalzZi2ZyzatN-4F2iRL0iakYdSYjs-IfdGwzxonbp9teeMtMuHJOnrSUiB8x1AD-bwLvJ/s1600/IMG_3708.JPG" style="margin-left: 1em; margin-right: 1em;"><img alt="closeup view of aluminum plate joining two angled pieces of wood" border="0" data-original-height="1200" data-original-width="1600" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAvEAzfPiKXlw3SzWMIkNv14KylyR39XqX3JZ3VTIHhySNnymIuaDu1TOOd-gKjWiWhSydVkIalzZi2ZyzatN-4F2iRL0iakYdSYjs-IfdGwzxonbp9teeMtMuHJOnrSUiB8x1AD-bwLvJ/w320-h240/IMG_3708.JPG" title="closeup view of aluminum plate joining two angled pieces of wood" width="320" /></a></div>
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So what made this rollercoaster different from the previous year's? Not much, except for the vertical drop. How vertical is vertical?<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsT4zYIHEYqlVQed5kYhH-gWaUlkkOLF_VC0HFx-uyyhpeoZhw-kFY-xUjIGCoi11ij7rI9kx8u6gRCG51hZDsfd_iajA_Et8dh4UNzkASU_jEUHd6cyl1pru01cgrUUUKhDujVdIhYSa8/s1600/20150905_153814.jpg" style="margin-left: auto; margin-right: auto;"><img alt="safety sign showing a truck falling off a cliff with caption UNDEFINED GRADE" border="0" data-original-height="1600" data-original-width="900" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhsT4zYIHEYqlVQed5kYhH-gWaUlkkOLF_VC0HFx-uyyhpeoZhw-kFY-xUjIGCoi11ij7rI9kx8u6gRCG51hZDsfd_iajA_Et8dh4UNzkASU_jEUHd6cyl1pru01cgrUUUKhDujVdIhYSa8/w225-h400/20150905_153814.jpg" title="safety sign showing a truck falling off a cliff with caption UNDEFINED GRADE" width="225" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Art credit: Emily Tencate<br /><br /></td></tr>
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<a href="http://www.dailymail.co.uk/news/article-2662875/Are-brave-Goliath-Six-Flags-open-worlds-tallest-steepest-fastest-wooden-roller-coaster.html" target="_blank">The record for steepest wooden rollercoaster is held by Goliath, in Six Flags (Illinois), with an 85deg drop</a>.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhg929DcncWWXkiDedrH8d0DOT8mx82mR_26FtNGQpJg4tRJT2_pwawNSog5EWUgHWlc9SP9clM0modPhpO391Vaycx2cy9RoewyTTohl9t8N3QSedhWpn1qp8SakTe6m11E4_8Vtf5DgBf/s1600/steep.JPG" style="margin-left: auto; margin-right: auto;"><img alt="screenshot of list of angles of descent for current steepest wooden rollercoasters" border="0" data-original-height="880" data-original-width="800" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhg929DcncWWXkiDedrH8d0DOT8mx82mR_26FtNGQpJg4tRJT2_pwawNSog5EWUgHWlc9SP9clM0modPhpO391Vaycx2cy9RoewyTTohl9t8N3QSedhWpn1qp8SakTe6m11E4_8Vtf5DgBf/w290-h320/steep.JPG" title="screenshot of list of angles of descent for current steepest wooden rollercoasters" width="290" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">http://www.ultimaterollercoaster.com/coasters/records/wood-roller-coasters.php</td></tr>
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We set out to beat this record and make a true vertical drop. And we did!</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi28Y8GbD3lE2ynY54mMQr7rpawwZONPajfchWv1fdeaGTJIowepVhg8Q2KD9UFiuPV29X-IeH3WxNFGfBz73SW6bM7Agoybsn0Otta6uS_txOqPRuD_xgS7XdHakzqvP-EAdNVukJ1tonC/s1600/20150904_154026.jpg" style="margin-left: auto; margin-right: auto;"><img alt="angle measurement of 90.3 degrees from the horizontal, slightly steeper than a vertical drop" border="0" data-original-height="1600" data-original-width="900" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi28Y8GbD3lE2ynY54mMQr7rpawwZONPajfchWv1fdeaGTJIowepVhg8Q2KD9UFiuPV29X-IeH3WxNFGfBz73SW6bM7Agoybsn0Otta6uS_txOqPRuD_xgS7XdHakzqvP-EAdNVukJ1tonC/w360-h640/20150904_154026.jpg" title="angle measurement of 90.3 degrees from the horizontal, slightly steeper than a vertical drop" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Technically beat a world record! (Steepest Drop, Wooden Rollercoaster)</td></tr>
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We reached out to Guiness world records, but they didn't make it over in time for deconstruction. Oh well.</div>
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<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.comtag:blogger.com,1999:blog-5736103898080682832.post-9226653771592863982017-07-02T00:04:00.005-04:002020-08-28T21:18:59.915-04:00Calipers Box<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGnozjNIpjs_uaoOwW4OwBBXOpxONDEz45kajz47L9G4RDZBXO6KYaoU0RqkvNQerGi0i-jOE_RGFtxdJGf5CF9WPaWvN7Quyk0SEUMz_ulSaNZTCrM2N19Sk5zcMVzrVe9zrTt3xw_3cd/s1600/20170630_180818.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="walnut hinged box with dark striations and "angel-step figure" on the left side" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGnozjNIpjs_uaoOwW4OwBBXOpxONDEz45kajz47L9G4RDZBXO6KYaoU0RqkvNQerGi0i-jOE_RGFtxdJGf5CF9WPaWvN7Quyk0SEUMz_ulSaNZTCrM2N19Sk5zcMVzrVe9zrTt3xw_3cd/w640-h480/20170630_180818.jpg" title="walnut hinged box with dark striations and "angel-step figure" on the left side" width="640" /></a></div>
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Finished pictures first. I completed the first of my set of calipers boxes (this one was the guinea pig version) and learned a lot about RealPersonWoodworking! The wood is domestic walnut, with cedar inserts on the inside. <span><a name='more'></a></span>This box is for me, to replace the incredibly mediocre stock case my calipers came with.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYdcwgaJC9l9_DAJribhyphenhyphenplJhsQYDtOr04_PYOdXEV162LNY0c1n_9g3Fp7f5Y5uyHKPuiGeCXzYDo2rtVmQHsAnC6xgzx67ivgaBFY3oqAVaEoIefgL58DR4wgd8_zVloZ4Mouk5F3K8h/s1600/20170630_180851.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="top view of box showing additional lengthwise striations (comes from spiral growth of the tree trunk)" border="0" data-original-height="858" data-original-width="1600" height="342" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYdcwgaJC9l9_DAJribhyphenhyphenplJhsQYDtOr04_PYOdXEV162LNY0c1n_9g3Fp7f5Y5uyHKPuiGeCXzYDo2rtVmQHsAnC6xgzx67ivgaBFY3oqAVaEoIefgL58DR4wgd8_zVloZ4Mouk5F3K8h/w640-h342/20170630_180851.jpg" title="top view of box showing additional lengthwise striations (comes from spiral growth of the tree trunk)" width="640" /></a></div>
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I got incredibly lucky with the selection of half-inch walnut boards at the store; found one with really nice figuring on one end. Of course the top side gets the prettier half. </div>
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Finish was two coats of satin polyurethane rubbed on with paper towels, which did a surprisingly good job of preserving the grain texture. Would use again.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgo0Jti1NtY60g2jbZHyR_lhyphenhyphenUPXsHdH1CfoXvxJiWPh9L-Ff26fsqGZ8u1E-Gh689Kda8GhHpkdQXqLZoOtxMsyYoUW6RzKPa_29SI2_FIHCbN9Yqrrb6eWHYHH4Y8nEMh0PTjEew3yy5/s1600/20170630_180756.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="open view of box showing calipers sitting in custom pocket" border="0" data-original-height="1075" data-original-width="1600" height="428" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgo0Jti1NtY60g2jbZHyR_lhyphenhyphenUPXsHdH1CfoXvxJiWPh9L-Ff26fsqGZ8u1E-Gh689Kda8GhHpkdQXqLZoOtxMsyYoUW6RzKPa_29SI2_FIHCbN9Yqrrb6eWHYHH4Y8nEMh0PTjEew3yy5/w640-h428/20170630_180756.jpg" title="open view of box showing calipers sitting in custom pocket" width="640" /></a></div>
Calipers! I couldn't find any reasonably-sturdy brass latches for this box thickness, so I inset magnet closures (two sets of neodymium magnets). I plan to use this in machine-shop settings with lots of steel filings around, so I covered the magnets with cedar-endgrain inlay. Filings can now be easily brushed off without getting stuck.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhi0xCZhkoR2tGekNVw5MZ48K-XetHpkH3llTtO79R3ye8pz4ZHhwDTkZcvG4vB2bh1k2YD7pe9fPsbGnc97cYTOyBc8dskYsj684YEvkw7WPhjdOCyjV8GPPYe7803-_Rk35fPE3Z9-mpx/s1600/20170630_180744.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="close up of high-contrast red cedar inlay covering magnet closure" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhi0xCZhkoR2tGekNVw5MZ48K-XetHpkH3llTtO79R3ye8pz4ZHhwDTkZcvG4vB2bh1k2YD7pe9fPsbGnc97cYTOyBc8dskYsj684YEvkw7WPhjdOCyjV8GPPYe7803-_Rk35fPE3Z9-mpx/w640-h480/20170630_180744.jpg" title="close up of high-contrast red cedar inlay covering magnet closure" width="640" /></a></div>
Here's a closeup of the cedar. I chopsawed a lump of scrap and lasercut the resulting endgrain slice (~1/16" thick). It was glued into the pocket and then made flush with finger planes and lots of sandpaper. I also have a rounded half-slot (don't know what those are actually called) for easier box opening. That was made with a router.<br />
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I missed some spots of glue (dark spots at the edges) when I was cleaning everything before putting the finish on, which makes me mildly sad. Lessons for next time.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgM0eryh4GjKkBhzBbC40e1vaS4lqpjhvaEVRCdRXSgdryft7aK5cAoT87in8dAKt3AvuCAVEPcrkIoMO3C6XjbwUyrV9qHP3zp3PwW3jz_tBOlf5Z1-hT-tU-g2BDASPJQJZHOV3vBSyKH/s1600/20170630_180658.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="close up view of box edge showing minor imperfections" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgM0eryh4GjKkBhzBbC40e1vaS4lqpjhvaEVRCdRXSgdryft7aK5cAoT87in8dAKt3AvuCAVEPcrkIoMO3C6XjbwUyrV9qHP3zp3PwW3jz_tBOlf5Z1-hT-tU-g2BDASPJQJZHOV3vBSyKH/w640-h480/20170630_180658.jpg" title="close up view of box edge showing minor imperfections" width="640" /></a></div>
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All the pockets were freehand milled (<a href="http://www.avamakesthings.com/2017/05/free-hand-milling-calipers-pocket.html">I posted a fun video of me playing etch-a-sketch here</a>) then cleaned up with chisels.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhA5vBXsFCNa8v0CHtaxPWNl0kgzo-O-HNL5v1foQe1cLrsfrR-ZaQ_pzPllU7JmNLuQY5-yFkWnMoumdBeUaqpPnrC9VqoRAxry_8OQ-g2Henxsk2HyDFIkR1VbG9hl1Yod9Rt9vdP-FUh/s1600/20170526_145835.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="bottom milled blank with torn up sections of wood near the calipers jaws' area" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhA5vBXsFCNa8v0CHtaxPWNl0kgzo-O-HNL5v1foQe1cLrsfrR-ZaQ_pzPllU7JmNLuQY5-yFkWnMoumdBeUaqpPnrC9VqoRAxry_8OQ-g2Henxsk2HyDFIkR1VbG9hl1Yod9Rt9vdP-FUh/w640-h480/20170526_145835.jpg" title="bottom milled blank with torn up sections of wood near the calipers jaws' area" width="640" /></a></div>
Here's what the rough blank looks like coming off the mill. Originally I was going to felt the bottoms and therefore didn't care about surface finish in the pocket, but I liked the plain wood more... so more chiseling/sanding than expected.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguKMVShWtgHqLw7fUo2bNsKRt8z9kIPxE_2D_102nsYMmXioDLa9GuNPTNSNfBe-M8N1COijFFVwZsDEQFQpB6p67vAT9lVq8YUqrhJ69cPplPDfCl7pbc8VJ3kmKkJ8fd3sylXoZzyP5e/s1600/image-20170529_165546.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="box with top and bottom attached with hinges" border="0" data-original-height="1200" data-original-width="1600" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguKMVShWtgHqLw7fUo2bNsKRt8z9kIPxE_2D_102nsYMmXioDLa9GuNPTNSNfBe-M8N1COijFFVwZsDEQFQpB6p67vAT9lVq8YUqrhJ69cPplPDfCl7pbc8VJ3kmKkJ8fd3sylXoZzyP5e/w640-h480/image-20170529_165546.jpg" title="box with top and bottom attached with hinges" width="640" /></a></div>
Hardware is the good stuff - brass 90deg Brusso stop hinges. <br />
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Here I'm checking fit; shortly after this I had to alter my magnet setup to use two magnets instead of one.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjmg8h3kGMRAUfly-Rijl8LZlssN_8P_0-AFj_UrJGZFalqZGtClzPwmnMUDu0Mo-oFtupVGVLG3d4-WdFR5E-kCuuVZ4SrsxuLI6AL4rQQu7-KRDcfq9iuaOxgTXya1kBuzI-kAnqyy_H/s1600/20170630_181237.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="side by side comparison of original and custom cases" border="0" data-original-height="908" data-original-width="1600" height="362" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjmg8h3kGMRAUfly-Rijl8LZlssN_8P_0-AFj_UrJGZFalqZGtClzPwmnMUDu0Mo-oFtupVGVLG3d4-WdFR5E-kCuuVZ4SrsxuLI6AL4rQQu7-KRDcfq9iuaOxgTXya1kBuzI-kAnqyy_H/w640-h362/20170630_181237.jpg" title="side by side comparison of original and custom cases" width="640" /></a></div>
Finished box is smaller than the old carrying case in all dimensions, so it's much more portable. More importantly, my calipers don't rattle around in this new one.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3NAt_cXNdijTPmLpFHbFOBDU3UogR0_ymqleTYzm_AwPMGtk35HFhT6Qe2zHU5qpi-SstQviS5FlRTJrRAH5d3K7zAw21NXh92cL2nitGypvbi2wCyZkSvk-epmVFRjFMXa_cm8WvwxaR/s1600/20170630_181128.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="side by side view showing differences in thickness" border="0" data-original-height="703" data-original-width="1600" height="280" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3NAt_cXNdijTPmLpFHbFOBDU3UogR0_ymqleTYzm_AwPMGtk35HFhT6Qe2zHU5qpi-SstQviS5FlRTJrRAH5d3K7zAw21NXh92cL2nitGypvbi2wCyZkSvk-epmVFRjFMXa_cm8WvwxaR/w640-h280/20170630_181128.jpg" title="side by side view showing differences in thickness" width="640" /></a></div>
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Mitutoyo is a quality calipers company, I don't know why their cases are so inefficient.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2kgfjqTssaCbVAwUptxJyP4GT-eQ5KEka1jHatAl9CM9vqCT8_Cv5ReaWG0j-RPg9wWR6wqpjD-Sq-Ag3IYIqkZuwhLlGjcuQrmLtLmOBSyngy3N5Mw6Jv5TBZjXrbwFaUEdtgd52DAU5/s1600/20170630_180647.jpg" style="margin-left: 1em; margin-right: 1em;"><img alt="calipers in finished walnut case" border="0" data-original-height="1484" data-original-width="1600" height="592" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2kgfjqTssaCbVAwUptxJyP4GT-eQ5KEka1jHatAl9CM9vqCT8_Cv5ReaWG0j-RPg9wWR6wqpjD-Sq-Ag3IYIqkZuwhLlGjcuQrmLtLmOBSyngy3N5Mw6Jv5TBZjXrbwFaUEdtgd52DAU5/w640-h592/20170630_180647.jpg" title="calipers in finished walnut case" width="640" /></a></div>
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Made a box! One down, one to go.</div>
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<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-33291967889243441262017-05-29T17:31:00.003-04:002020-08-28T21:21:39.817-04:00free-hand milling calipers pocket<div style="text-align: left;">I'm in the process of making a set of calipers boxes, where I'm roughing out the pockets on the mill and then cleaning up with chisels.</div>
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Mill pocketing is done free-handed, because it's more fun. It's like playing with an etch-a-sketch, but better!</div>
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<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/219429916?title=0&byline=0&portrait=0" title="Machining Video" webkitallowfullscreen="" width="640"></iframe><br /></div>
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<span style="font-size: x-small;">video 2x speed</span></div>
Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-12814880280288018292017-05-22T20:44:00.001-04:002020-08-28T21:28:29.060-04:00[2.70] Final Testing & DocumentationLast 2.70 post woooo!<br />
After <a href="http://www.avamakesthings.com/2017/05/270-mcm-wall-mount-vertical-axis.html">assembling the vertical axis</a>, all that was left was bolting on the wooden desktop and testing.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjO1kU6pLGH6tbvoqH6rU7gwseBJkeHuT_zIKm3Tt-RFLYo99xBfVrJEq7MJa_HGd_F0YEJECKlk4PDVWS1bfF4OzBENUDFye0RVrAqp8Z3QCHuSmBkiMMAht5dg4JBDt2Bi8VyL3defZWG/s1600/20170515_145746.jpg" style="margin-left: auto; margin-right: auto;"><img alt="laptop posed on desk at seated-height setting" border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjO1kU6pLGH6tbvoqH6rU7gwseBJkeHuT_zIKm3Tt-RFLYo99xBfVrJEq7MJa_HGd_F0YEJECKlk4PDVWS1bfF4OzBENUDFye0RVrAqp8Z3QCHuSmBkiMMAht5dg4JBDt2Bi8VyL3defZWG/w640-h480/20170515_145746.jpg" title="laptop posed on desk at seated-height setting" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">pretty computer on pretty desk</td></tr>
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For the purposes of this class, I kept power & software fairly rudimentary. The motor is powered from a 12V supply (using alligator cables) and driven with an H-bridge/Arduino/USB setup hooked directly to my laptop. I'm just running the generic stepper library and not trying to use microstepping, so the motor is ridiculously loud and inefficient compared to its potential.<br />
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Between assembly and testing the HobbyShop staff started storing stuff on my desk...<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipO1-ryMTIsLKioOrHUGGckRFCrSRMcHS7Tj5iwV2b5_4jahp3HtOcfqe31UnJoL_65VUeohruEopWU1bmJy_XeR5Q9RNkvbqKxXnn3nl5eD_1GP6fnh-2XVAX9VTWe8o06XouO32ICHR8/s1600/20170512_175837.jpg" style="margin-left: auto; margin-right: auto;"><img alt="bike helmet and attire piled on desk with motor power supply and cables underneath" border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEipO1-ryMTIsLKioOrHUGGckRFCrSRMcHS7Tj5iwV2b5_4jahp3HtOcfqe31UnJoL_65VUeohruEopWU1bmJy_XeR5Q9RNkvbqKxXnn3nl5eD_1GP6fnh-2XVAX9VTWe8o06XouO32ICHR8/w240-h320/20170512_175837.jpg" title="bike helmet and attire piled on desk with motor power supply and cables underneath" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">HobbyShop staff trust my desk as a shelf.<br />
Powersupply below. Foam cup only holds screws (no liquid don't worry)</td></tr>
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It goes up and down! Tuning the Arduino code to behave with a not-actually-a-stepper-driver at a reasonable speed while not causing ridiculous vibrations took some time.<br />
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<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/218506238?title=0&byline=0&portrait=0" webkitallowfullscreen="" width="640"></iframe><br /></div>
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I conducted some repeatability abbe-error tests with a laser pointer. The laser fixture was clamped to the desk and pointed towards the wall, 1m away (there was a brick column in the way!).<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8jEW5vb800_uO1mA_Xp5L63-XBcKFwXUM_ajgNtpGjWRaCo2cxIsAlNLwrpXocWj1TMA4mj32hurIBnwuaCTdjK0eQtF20cxruhrdgQcFweWtlTx5u0H5pN6SCrF8bahhbVdz0XuAlw2F/s1600/20170515_145501.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8jEW5vb800_uO1mA_Xp5L63-XBcKFwXUM_ajgNtpGjWRaCo2cxIsAlNLwrpXocWj1TMA4mj32hurIBnwuaCTdjK0eQtF20cxruhrdgQcFweWtlTx5u0H5pN6SCrF8bahhbVdz0XuAlw2F/s640/20170515_145501.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Laserpointer assembly clamped to the center of the desk.</td></tr>
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The test shown below has the desk commanded to move between two set points 14cm apart. The laser-projected locations of the lower setpoint were marked on a piece of paper, from which positioning error can be determined from average deviation. This positioning error (unweighted) ended up being an average of 2.39mm over the 1m distance, so 0.33mm error over the 14cm travel.</div>
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This desk therefore has an unweighted positioning error of 2.4 microns per mm-travel.<br />
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<iframe allowfullscreen="" class="giphy-embed" frameborder="0" height="480" src="https://giphy.com/embed/1rJHoWZt97NWU" width="270"></iframe><iframe allowfullscreen="" frameborder="0" height="480" mozallowfullscreen="" src="https://player.vimeo.com/video/218508297?title=0&byline=0&portrait=0" webkitallowfullscreen="" width="270"></iframe></div>
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An unweighted desk is an unused desk. The desk-requirements allow for an unweighted desk when moving, but it still needs to hold stuff.</div>
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I grabbed 2.5lb (1.134kg) and 10lb (4.536kg) weights and observed their effects when placed on different areas of the desk relative to the rail-ballscrew shafts. </div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-odtdTRDCwHCZCZSi4cPeN8sfLEikfePSH7lLS5cdiDkvv8SLxNkeStimbj0LPl85sqJpgbvRS7tI4YRrxZ1XtSDh3rrxG0RZkS-RWVBtJltVoTufjszdiy9lJl_eoCpPa6iyNAoZJ2YC/s1600/20170515_144808.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-odtdTRDCwHCZCZSi4cPeN8sfLEikfePSH7lLS5cdiDkvv8SLxNkeStimbj0LPl85sqJpgbvRS7tI4YRrxZ1XtSDh3rrxG0RZkS-RWVBtJltVoTufjszdiy9lJl_eoCpPa6iyNAoZJ2YC/s320/20170515_144808.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">2.5lb weight at (-430, 420)</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCJ7P3-WyQszwOpq8BWW9_sYtWIePLM-LRhzRQgTK-KrPupELOw53GWLT9iMYThkT5DmZbh8_zO6_o77zf9Ju31mwcFY7qJxxV6rywO6pIDxAG0mJ_9tS_h_3OwogH0_yo9Yf-GkktzxO5/s1600/20170515_144706.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="280" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCJ7P3-WyQszwOpq8BWW9_sYtWIePLM-LRhzRQgTK-KrPupELOw53GWLT9iMYThkT5DmZbh8_zO6_o77zf9Ju31mwcFY7qJxxV6rywO6pIDxAG0mJ_9tS_h_3OwogH0_yo9Yf-GkktzxO5/s640/20170515_144706.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Experiment with 20lbs at (0, 250)</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXkCUgpjXuKfHDxYnxcKFaq02XdaQfWMWwFPwFsl9hVRPNbbllr0ykbFjeJj00EdtcJvtzXlH7GgnbR06yaQ1UOvYtss6S6Yzs0kykHfOy4tF2lD_OpRZom0xsn5-Y_20XCah6UU7mia2m/s1600/diagram.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="218" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXkCUgpjXuKfHDxYnxcKFaq02XdaQfWMWwFPwFsl9hVRPNbbllr0ykbFjeJj00EdtcJvtzXlH7GgnbR06yaQ1UOvYtss6S6Yzs0kykHfOy4tF2lD_OpRZom0xsn5-Y_20XCah6UU7mia2m/s320/diagram.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Coordinate system for desk tests</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTHqiv3PAhifoiDloBiazx2U00TTgr07dqpFV0D66p2fyRj56XVVxcEv2Zrif75h4-pLIs0ijs6_XREm0iRbUuzfMU6pcOsP_4E5HJOeM-7YkVg3AGW43z8dJ91Cjd4VTCCYq4Vb1PkKk5/s1600/weightedres.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="224" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgTHqiv3PAhifoiDloBiazx2U00TTgr07dqpFV0D66p2fyRj56XVVxcEv2Zrif75h4-pLIs0ijs6_XREm0iRbUuzfMU6pcOsP_4E5HJOeM-7YkVg3AGW43z8dJ91Cjd4VTCCYq4Vb1PkKk5/s640/weightedres.JPG" width="640" /></a></div>
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After adding HDPE skids (<a href="http://www.avamakesthings.com/2017/05/270-mcm-wall-mount-vertical-axis.html">see vertical axis build post</a>), I experimentally determined max yaw displacement by pushing on the corner of the desk until it hit the hardstops. These projected errors were +19.83mm and -22.24mm for a vaguely 10lbf push.</div>
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Using the same Abbe error equations as the<a href="http://www.avamakesthings.com/search/label/linear%20axis"> previous linear axis testing</a>,<br />
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$\alpha_{pitch} = \frac{\delta_y}{L}$</div>
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and</div>
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$err_{pitch} = \frac{\delta_y y}{L+y}$</div>
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$\alpha_{roll} = \frac{\delta_x}{L}$</div>
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and</div>
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$err_{roll} = \frac{\delta_x x}{L+x}$</div>
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where I'm making the approximation that vertical displacement only comes from pitch and horizontal displacement from roll since I have so few samples and since the measurements are reasonably close within sets.</div>
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Using these error calculations, I calculated pitch, roll, and yaw stiffnesses of the desk, where roll stiffness > pitch > yaw by approximately an order of magnitude each.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiind1Mji2I1gcuumw2249HbKzmIuQF_cXTr1u1T6X7Ed62QvWQ0JS-aR1S5t_wABT_IRPA247wA27hJeRM3cIQGdnsfD7Xw83QjU5wWahC32cUYEXmcNNMyq_feqWuU8mJes_NSM1k4bbw/s1600/stiffnessres.JPG" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="112" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiind1Mji2I1gcuumw2249HbKzmIuQF_cXTr1u1T6X7Ed62QvWQ0JS-aR1S5t_wABT_IRPA247wA27hJeRM3cIQGdnsfD7Xw83QjU5wWahC32cUYEXmcNNMyq_feqWuU8mJes_NSM1k4bbw/s640/stiffnessres.JPG" width="640" /></a></div>
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I also did some qualitative testing, and discovered that my system is too low-friction and too backdrivable for my motor to support loads as predicted by the error spreadsheet. That's kinda expected, given that my system uses a high-pitch ballscrew.</div>
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However, an unfortunate consequence of this is that a load of ~7lbs (laptop + 2.5lb weight) is the most this actuator can take while traveling up and down at speed, and it sounds terrible doing it. I could have tuned the system to run at a lower speed, but this is somewhat difficult to do with my software setup. Soooo... meh.</div>
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<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/218510076?title=0&byline=0&portrait=0" webkitallowfullscreen="" width="640"></iframe><br /></div>
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<span style="font-size: x-small;">Desk happilly traveling with 20N loads, then getting upset at 30N load.</span></div>
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This means I can type on my laptop and put my elbows on this desk, but putting my legs on the desk backdrives the motor (no power). If power were turned on, it would likely hold more; however putting 20lb on the desk draws 3A current, at which point I start to worry about thermal dissipation in my H-bridge driver setup.<br />
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<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/218511179?title=0&byline=0&portrait=0" webkitallowfullscreen="" width="640"></iframe><br />
<span style="font-size: x-small;">Even small dynamic loads lower the desk.</span><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiOoTiE6ThEi6lZfi7EA1-SC_LcBvLEsRe5m_hvw5i6a_YW_ewBifRVXcWgHNtWAFydkYnQDPgRT7Ycciev2sluBu2H5e-gqIs3Fmr29fxRIb0vx6AJ0CloXqvton25nHY0dQ5dsdIpi_tC/s1600/20170515_160259.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiOoTiE6ThEi6lZfi7EA1-SC_LcBvLEsRe5m_hvw5i6a_YW_ewBifRVXcWgHNtWAFydkYnQDPgRT7Ycciev2sluBu2H5e-gqIs3Fmr29fxRIb0vx6AJ0CloXqvton25nHY0dQ5dsdIpi_tC/s320/20170515_160259.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The desk holds laptop and legs in static-loading just fine</td></tr>
</tbody></table>
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Adding a gearbox between my motorshaft and the ballscrew would help make my desk sittable, but in its current setup I doubt it would hold close to bodyweight before either my motordriver overheats or my rails break. So, no-go on the "Real Desk" functional requirement.</div>
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The desk does hold at least static-108N (laptop + 20lb weights) without failing, so it does meet the class calculation-standards with 100N loads (albeit barely; it probably wouldn't meet the expected 2x safety factor). </div>
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Circling back to the original error predictions for a 100N load, I had expected to get 0.23mm displacement from the theoretical desk. Instead, I got 2.87 - an order of magnitude higher.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgNtbTEEk1tLiVUiCUTxAs4OOHTXN4pKqQiDNMy_jlNHP0jwidBspfrngzQPFe4_KatcG37CNO0Fhxjg8l07G0yKo4ESfj5rcpoKEt30aMnSlSzRc8bHoq0n54UBHLCQoyoKXZb-s2_Q7l/s1600/original.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" height="326" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjgNtbTEEk1tLiVUiCUTxAs4OOHTXN4pKqQiDNMy_jlNHP0jwidBspfrngzQPFe4_KatcG37CNO0Fhxjg8l07G0yKo4ESfj5rcpoKEt30aMnSlSzRc8bHoq0n54UBHLCQoyoKXZb-s2_Q7l/s640/original.JPG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">What went wrong?</td></tr>
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Searching through the error spreadsheet, I found a problem with my model.</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcP9GHeOQ9ikHfBDuv_SitaJxQd72wyZNtjAQckBeZTMgPwIPqQlCuSvQkZ5cKTmx4ne2XL2va9JFImXP7rGZsbOFSAfebNL_rSBgSy6nu7GnkesIg2INe4iV12sZsV_P2uCrFvMGn9WwQ/s1600/oops.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" height="530" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcP9GHeOQ9ikHfBDuv_SitaJxQd72wyZNtjAQckBeZTMgPwIPqQlCuSvQkZ5cKTmx4ne2XL2va9JFImXP7rGZsbOFSAfebNL_rSBgSy6nu7GnkesIg2INe4iV12sZsV_P2uCrFvMGn9WwQ/s640/oops.JPG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Linear stiffness of the carriage in the model equals bearing stiffness</td></tr>
</tbody></table>
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I had included flexures in my carriage to account for parallelism-errors with the rails, and had discovered that the rail-shafts bend before the flexures do when I was <a href="http://www.avamakesthings.com/2017/05/270-mcm-wall-mount-vertical-axis.html">assembling the vertical axis.</a> And that makes sense - the rails are only 8mm in diameter and have an unsupported length of ~350mm, whereas the ball-bushings are set in a thick block of aluminum.</div>
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I had considered shaft stiffness before (in that post, actually), but at the time I was only concerned with whether deflections approached yield stress. Returning back to those calculations, and changing rotation and linear stiffnesses in the spreadsheet to be an average of ballscrew and rail shaft stiffnesses, I get some more reasonable results.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtxwWel3PnfkJRVvfmoFvB3BNYAdFI-Gxij9DsV8RgDhNaLpT1MJzUvio4W1CWzn1PbpPLYBAy5cGZz75fjs7bwUh78zqNLeI15Zrr4jNMw3EC3ECEv4U8VJhJAhghU1qQja7oXljFYoHc/s1600/shafts.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" height="216" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtxwWel3PnfkJRVvfmoFvB3BNYAdFI-Gxij9DsV8RgDhNaLpT1MJzUvio4W1CWzn1PbpPLYBAy5cGZz75fjs7bwUh78zqNLeI15Zrr4jNMw3EC3ECEv4U8VJhJAhghU1qQja7oXljFYoHc/s640/shafts.JPG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Shaft compliance calculations</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0FYVk-Cfen35HTPRD8hGvwLVjlOu6mxQ_P67GD9wTin40E4FIva4SYDuFe2GfxIrlmZ46-1QC6ZV8QbxJg2XkjHTqfxR3Rca3XzOpCb4wX8aSngoLPcLL0otespb2C-ZXFfSI-WHkrQm7/s1600/new.JPG" style="margin-left: auto; margin-right: auto;"><img border="0" height="148" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0FYVk-Cfen35HTPRD8hGvwLVjlOu6mxQ_P67GD9wTin40E4FIva4SYDuFe2GfxIrlmZ46-1QC6ZV8QbxJg2XkjHTqfxR3Rca3XzOpCb4wX8aSngoLPcLL0otespb2C-ZXFfSI-WHkrQm7/s640/new.JPG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">new results. Note the F = kX displacement.</td></tr>
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Reality only matches models when the models are accurate - shaft stiffness is where my order of magnitude discrepancy came from.</div>
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That's it for the 2.70 desk!</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaSoGC2EVVAcn3tVJVLYjXd9iQ2j2P7WBVir9n5rIXrBmOBYlhK8PCddGSxyBChriKGEmzJzgjOkOgb3Uj8So_-k9-C-z_4Rhavh8KREU0TtgqhVTdv_MlP831RzSLAZ6OULkgtqcMi1e1/s1600/20170515_145752.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgaSoGC2EVVAcn3tVJVLYjXd9iQ2j2P7WBVir9n5rIXrBmOBYlhK8PCddGSxyBChriKGEmzJzgjOkOgb3Uj8So_-k9-C-z_4Rhavh8KREU0TtgqhVTdv_MlP831RzSLAZ6OULkgtqcMi1e1/s640/20170515_145752.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Desk being a desk.</td></tr>
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Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-39780810750971041172017-05-20T23:32:00.001-04:002020-08-01T21:41:42.050-04:00[2.70] MCM: Wall-mount Vertical Axis<div class="separator" style="clear: both; text-align: center;">
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This post is about the design, fabrication, and assembly of the desk's vertical axis.</div>
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The vertical axis builds upon <a href="http://www.avamakesthings.com/search/label/linear%20axis">preliminary linear axis work, documented here.</a></div>
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Concept outlined <a href="http://www.avamakesthings.com/p/270-desk-concept-layout.html">in a previous post.</a></div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUWNnN2DBs4_R8c6XkV5U6IQsTKojtOi0v3nKN2hafqJbgU5uade-P73YHHfKjtcZjgNXLyMQWEHQDikpD9YzT9Gp7moEQYSezqwSgTUsMEOL5o2imIJRUCDqJYAS8Ux5mDafPeKEiQ6GN/s1600/vert.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="584" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUWNnN2DBs4_R8c6XkV5U6IQsTKojtOi0v3nKN2hafqJbgU5uade-P73YHHfKjtcZjgNXLyMQWEHQDikpD9YzT9Gp7moEQYSezqwSgTUsMEOL5o2imIJRUCDqJYAS8Ux5mDafPeKEiQ6GN/s640/vert.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Sketch diagram, CAD model, finished assembly on-wall</td></tr>
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Designing the vertical axis was focused on reusing a THK ballscrew assembly I already had. This ballscrew <a href="http://www.avamakesthings.com/2017/04/270-seek-and-geek-10-ballscrew.html">required a bit of reconditioning before use</a>, and no longer had a datasheet/drawing on file from the manufacturer, but I found a close approximation from which I could estimate numbers.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgg_6vTgteVn-SQ8-v-FYyjolyvsrTBsjMWEp7hQJY44Syeac7qzhJAjnJ-Vwpc9L8E3CMQ3-cq0IROoWk-3eTZxGENwE13swICgAJ2uof1yEQ8hRn6sELlrxZACYbaWyIJqcZrJjUf9vZL/s1600/ballscrew.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="260" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgg_6vTgteVn-SQ8-v-FYyjolyvsrTBsjMWEp7hQJY44Syeac7qzhJAjnJ-Vwpc9L8E3CMQ3-cq0IROoWk-3eTZxGENwE13swICgAJ2uof1yEQ8hRn6sELlrxZACYbaWyIJqcZrJjUf9vZL/s640/ballscrew.PNG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="http://www.thkstore.com/products/feed-screw/ball-screws/bnk-set.html?thk_shaft_od_mm=7537&thk_lead_mm=6712" target="_blank">THK BNK1205-2.5RRGT+330LC3Y machine drawing</a></td></tr>
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This particular ballscrew assembly has a dynamic load rating (axial) of 3.7kN and a stiffness of 120 N/<span style="background-color: white; color: #222222;"><span style="font-family: inherit;">μm, so at least it won't be the thing that breaks first.</span></span><br />
<span style="background-color: white; color: #222222;"><span style="font-family: inherit;"><br />
</span></span> <span style="background-color: white; color: #222222;"><span style="font-family: inherit;">I also had on hand a number of Misumi-brand <a href="https://us.misumi-ec.com/vona2/detail/110300026540/?HissuCode=LMU8" target="_blank">LMU8</a> linear bushings and <a href="http://uk.misumi-ec.com/vona2/detail/221000058301/?HissuCode=608Z" target="_blank">608Z</a> bearings, so the desk rails would continue to be the 8mm diameter steel rods (though I swapped out my original rods for 400mm long hardened-steel ones). Coincidentally, the free end of the ballscrew has a diameter of 8mm.</span></span><br />
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</span></span> <span style="background-color: white; color: #222222;"><span style="font-family: inherit;">The unibody carriage was machined from a single piece of 6061-T6 rectangle stock. Since it was the most complicated component to machine, I tackled it first. </span></span><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPhiIlLDFYisdleKurwO0ROI9be3cGDA13IETTOv8HDa6YoWaIZfcvgjCoVHCkZZbtuWoDfwB-x1lcM4gD6sm18XM_I9jfOFoivD8DN-P1WHkv1NYWaW_L4ih54IYrBrDhy0ew_jITOjaz/s1600/drawing4.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="502" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPhiIlLDFYisdleKurwO0ROI9be3cGDA13IETTOv8HDa6YoWaIZfcvgjCoVHCkZZbtuWoDfwB-x1lcM4gD6sm18XM_I9jfOFoivD8DN-P1WHkv1NYWaW_L4ih54IYrBrDhy0ew_jITOjaz/s640/drawing4.PNG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Carriage machine drawing: manual mill and bandsaw</td></tr>
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The most critical dimensions of the carriage were parallelism and symmetry of the bushing-throughholes relative to the ballnut pocket, followed by surface flatness for the plane attaching to the desktop.</div>
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To ensure that the ballscrew dictated carriage positioning vs the rails, I bandsawed flexures into the carriage - one allows compliance in yaw, and the other in roll. Careful positioning in assembly would take care of pitch. It turned out that these flexures were unnecessary; the rails themselves were compliant enough.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0DxswK6RiGChwhsrYQbQMMd_MVYHqhNhR5DvcFJrlnWu3JewCA19LIhwj8Vp7ZxSg-LeXafNjiRKtAAoLTWfLaif-TYQKMGeL97Kf-ns_R6t8aKzxui-INa-io2_BiUWVYc9XBcnRwfTV/s1600/20170521_000003.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi0DxswK6RiGChwhsrYQbQMMd_MVYHqhNhR5DvcFJrlnWu3JewCA19LIhwj8Vp7ZxSg-LeXafNjiRKtAAoLTWfLaif-TYQKMGeL97Kf-ns_R6t8aKzxui-INa-io2_BiUWVYc9XBcnRwfTV/s320/20170521_000003.jpg" width="262" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Shaft compliance of 8mm rails</td></tr>
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Bushing clearance holes were oversized by 0.05mm to provide a <a href="http://www.engineersedge.com/class_iv.htm" target="_blank">slight interference fit</a>. Bushings were first added and held in place with retaining rings; after rails were inserted in the assembly I fixed the bushings in-place with Loctite 648.</div>
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The ballnut pocket took advantage of the preexisting hole pattern, although after machining I realized I had forgotten to make one set of holes tap-clearance instead of screw-clearance. I fixed my mistakes by drilling two access-holes and dropped M5 nuts in the bolt-paths (oops). </div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUzfKR9o004LDLeYorVlOE2bjecVcu1572UGlod84UIDOMt-rjJilaotOi6JCkNBu-4WsX4N8zh8RGFQoW16oHRSK8AwtJJmQffC1ia4EgstbsgltsIpXG4OmDISS4UXKSkApiyzGT51Vd/s1600/20170516_152135.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiUzfKR9o004LDLeYorVlOE2bjecVcu1572UGlod84UIDOMt-rjJilaotOi6JCkNBu-4WsX4N8zh8RGFQoW16oHRSK8AwtJJmQffC1ia4EgstbsgltsIpXG4OmDISS4UXKSkApiyzGT51Vd/s320/20170516_152135.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Bushings with retaining rings</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjb1GbY9CdyMSgJUmavZfAYHkGclfIPrKfwFQxfy9_zytT-rebY9_8qdTtqNodJMNKclSgSE6mCRRmufXaPUjKsDc5r0rpvzKt7zLG2e_ecXbGMB_2NTe6W3g_JaBPhBNxU8GogYxrRut-h/s1600/20170516_151511.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjb1GbY9CdyMSgJUmavZfAYHkGclfIPrKfwFQxfy9_zytT-rebY9_8qdTtqNodJMNKclSgSE6mCRRmufXaPUjKsDc5r0rpvzKt7zLG2e_ecXbGMB_2NTe6W3g_JaBPhBNxU8GogYxrRut-h/s320/20170516_151511.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Carriage with ballnut in place</td></tr>
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The other major reuse-element was the motor. Final desk is going with a MachMotion 23-size stepper instead of the previous Nema 17-motor, which allows me more freedom in friction and weight loads on the ballscrew. Torque required to drive a ballscrew is:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCCtmhXW7DY1gSUbi_PshnHTbuWlau7fmd2J0DUxCspA7Kpo0AZMGcQae3BZxOl85Ih1zY9MmkpHDgVKrAWMuijzR7ThDSEeoA8p_2gRHt306HaVanfCkPN0STSfXgQ06Timtqhpu0xzNS/s1600/Capture.PNG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="60" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCCtmhXW7DY1gSUbi_PshnHTbuWlau7fmd2J0DUxCspA7Kpo0AZMGcQae3BZxOl85Ih1zY9MmkpHDgVKrAWMuijzR7ThDSEeoA8p_2gRHt306HaVanfCkPN0STSfXgQ06Timtqhpu0xzNS/s200/Capture.PNG" width="200" /></a></div>
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<span style="font-family: inherit;"><span style="background-color: white; color: #222222;">where F = load (N), R = ballscrew lead (mm) and<span style="font-family: inherit;"> </span></span></span><span style="background-color: white; color: #222222;"><span style="font-family: inherit;">η = efficiency (assume 90% for ballscrew). For an expected desk axial load of 1000N and a ballscrew with a 5mm lead, torque required should be somewhere around 0.89Nm, which this motor can supply. </span></span><br />
<span style="background-color: white; color: #222222;"><span style="font-family: inherit;"><br /></span></span>
<span style="background-color: white; color: #222222;"><span style="font-family: inherit;">I also don't need to worry about actuator resonance of the ballscrew... any reasonable speed running this desk will be under the critical speed.</span></span><br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmMAl9DU7vpx-o6Sr9KjTPOD49a4zBLvuO9qIhJl9panVg7F9qUb64OjQmxe7voBx4bky6oQAiJabKE7GstfuMu67CZDn0c2CaEtxEAsJzuRDnsTjaThP2QstDybtJx8vtk-CSdjOpz2Rp/s1600/20170521_000110.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="211" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmMAl9DU7vpx-o6Sr9KjTPOD49a4zBLvuO9qIhJl9panVg7F9qUb64OjQmxe7voBx4bky6oQAiJabKE7GstfuMu67CZDn0c2CaEtxEAsJzuRDnsTjaThP2QstDybtJx8vtk-CSdjOpz2Rp/s320/20170521_000110.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">calculating critical speed of a simply supported lead screw</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyQrs4sVM0pAiYvlNZW-r46qJOmyIrj66bL5I3k85NibwDl4F8VI48sF8T3qm851u9nmhOpYMvw7QG_3SzYQxUKx1vyY357Sgr-UkDsDLgfGi_bgMHeVsbveLpCKA-kTm9FBnF2mbkcnCf/s1600/st23.PNG" imageanchor="1" style="clear: right; float: right;"><img border="0" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyQrs4sVM0pAiYvlNZW-r46qJOmyIrj66bL5I3k85NibwDl4F8VI48sF8T3qm851u9nmhOpYMvw7QG_3SzYQxUKx1vyY357Sgr-UkDsDLgfGi_bgMHeVsbveLpCKA-kTm9FBnF2mbkcnCf/s320/st23.PNG" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-l657_ACUN-UDmkZG0IQyvqmFunHKO9O-tKg9tqN5vb_X6ObVq8faTk8gpnsEXDeRSKIFZu4L9XycTugPxoHAzpICCWCPQy66_Looi0j1yf0tn_-b0Pei2paXgBMcwi-_LpdeqT4Pc7NB/s1600/20170520_171801.jpg" imageanchor="1"><img border="0" height="272" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-l657_ACUN-UDmkZG0IQyvqmFunHKO9O-tKg9tqN5vb_X6ObVq8faTk8gpnsEXDeRSKIFZu4L9XycTugPxoHAzpICCWCPQy66_Looi0j1yf0tn_-b0Pei2paXgBMcwi-_LpdeqT4Pc7NB/s320/20170520_171801.jpg" width="320" /></a> </div>
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<span style="font-size: x-small;">Motor & flexible coupling (left). Self-made drawing from motor measurements (right)</span></div>
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I needed to make a motor mount that coupled to the ballscrew driver block. The motor itself is coupled to the driveshaft via a flexible coupling, so precision concentricity wasn't strictly required. Clearance hole patterns from both the motor and the driver block were drilled into a piece of angle stock, and the motor got bolted in place after attaching the coupling. This assembly method minimized overconstraint, though enough was present that the motor ended up being louder than necessary.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDcN897yZernMQHNOCn-Zg_DYv4fdqkHF90QY3hEWQI-I0mR4f2DLOmwJ5-oTufO4cMuSnV4qdhA3pEikNceX2U1pl4UMPmCf69gKB3UBp1n5v23mOettkpSwRUI9PZBFC0OyfLjgVQ747/s1600/drawing1.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDcN897yZernMQHNOCn-Zg_DYv4fdqkHF90QY3hEWQI-I0mR4f2DLOmwJ5-oTufO4cMuSnV4qdhA3pEikNceX2U1pl4UMPmCf69gKB3UBp1n5v23mOettkpSwRUI9PZBFC0OyfLjgVQ747/s400/drawing1.PNG" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Motor mount drawing</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMe-V_6twpTZBUUmTo3Oea79UlXV1H3eQruEGsFK1V5W-PictaLTzzAzzJabrbl6fkMPM8757__6G-sEcWLLsfHiW9xKNjk10IzSJ1Jxi2Y7Yob55UHoTB-42RYn2rQSUrAS1djLbD4hvK/s1600/20170516_151253.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="219" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMe-V_6twpTZBUUmTo3Oea79UlXV1H3eQruEGsFK1V5W-PictaLTzzAzzJabrbl6fkMPM8757__6G-sEcWLLsfHiW9xKNjk10IzSJ1Jxi2Y7Yob55UHoTB-42RYn2rQSUrAS1djLbD4hvK/s640/20170516_151253.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Motor mount, driver block (with flexible coupling inside), and carriage</td></tr>
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You might notice funny white blocks that got added the carriage. After the first desk-expo on May 10 (documentation trailing behind project schedules once again), I decided that despite originally not caring about deflection in yaw the amount I got was a little ridiculous. The purpose of these HDPE skids (from leftover kayak plastic!) was to act as hardstops against the wall to minimize desk rotation.</div>
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There was pretty minimal planning before machining these skids and adding them in - just measuring required distances on the desk with a tape measure and matched-machining a pair to ensure dimensions were the same.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzbpUygi4FpXGEkevZjW83otr8evyTs6wR7b5H7SO9hJuEHpLOn_-lfcDy4wi2HzuAp2726Q8YbVfVTv67M5fM2k4qdlb4HnN4VvSN7jW5UQwhUub8nAQvoMqcz3LDh74R6xUPeSX_IIWl/s1600/20170520_174821.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzbpUygi4FpXGEkevZjW83otr8evyTs6wR7b5H7SO9hJuEHpLOn_-lfcDy4wi2HzuAp2726Q8YbVfVTv67M5fM2k4qdlb4HnN4VvSN7jW5UQwhUub8nAQvoMqcz3LDh74R6xUPeSX_IIWl/s320/20170520_174821.jpg" width="210" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6beyNq4rPNl8hfKPFAjzljv7V1zUznOaeUuTZ-HXIWjd-80ecJZ6I8YvkYi6LU0hW9mvMrYjcxCWu5ZO6vu1qgyhOtilTNrcjojG7UDXxhtWZOFi-hbbrVMafbyIqko0WUWwIU6sgvSYy/s1600/20170516_153852.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6beyNq4rPNl8hfKPFAjzljv7V1zUznOaeUuTZ-HXIWjd-80ecJZ6I8YvkYi6LU0hW9mvMrYjcxCWu5ZO6vu1qgyhOtilTNrcjojG7UDXxhtWZOFi-hbbrVMafbyIqko0WUWwIU6sgvSYy/s320/20170516_153852.jpg" width="240" /></a></div>
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The motor coupling I got ended up being a millimeter too large for the ballscrew shaft, so I shimmed it with a drilled-through, bandsaw-slotted bushing.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLlucc77EYrrXisVhnWT_cNm_Iv-cYPIVQiOMzRS44CGOmwvLMAusrOUZRZFWbYhna12vALbal8uvqegIqGxoMLe87h7PlOq1SMd-2uvLCEWsihFo11_28sKPqVo7bYBO6e-7XaUGnwqDn/s1600/20170516_152016.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="227" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLlucc77EYrrXisVhnWT_cNm_Iv-cYPIVQiOMzRS44CGOmwvLMAusrOUZRZFWbYhna12vALbal8uvqegIqGxoMLe87h7PlOq1SMd-2uvLCEWsihFo11_28sKPqVo7bYBO6e-7XaUGnwqDn/s320/20170516_152016.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Bushing-shim, coupling, ballscrew shaft</td></tr>
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I made a support block to match the commercial driver-block on the ballscrew assembly. This block held a 608Z bearing which would then press against the ballscrew shaft when bolted to the wall plate. The only critical dimension here was making sure the distance from the bearing center to the wall was the same as on the driver block. Everything else could be aligned in assembly.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlIRtUNrZBgS5p_QvwRa7MTSsDEc5a5m1n0rF0ztzZD7ZE_gER5WOB1SgG7wrIQMyxwkLQEjo53so9V3t8h3iyRhSCJWZDEoYGHEYZKUrh8O_sHPODAgMOAKUgzZ80Tvqt85nucijaLiBP/s1600/drawing3.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhlIRtUNrZBgS5p_QvwRa7MTSsDEc5a5m1n0rF0ztzZD7ZE_gER5WOB1SgG7wrIQMyxwkLQEjo53so9V3t8h3iyRhSCJWZDEoYGHEYZKUrh8O_sHPODAgMOAKUgzZ80Tvqt85nucijaLiBP/s320/drawing3.PNG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Machine drawing for shaft-support block</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh25wb-FSk3QoEJN4goDdD0sBFwgngWNOWx9NFXrapBvLPA_60RQFiVK2E0w8PAWJHLaOErTEz6yp6rw_sxSo3DJJuRhNeDcDS_uo6K6mH6tIxDVHUqlIl0puXxUXXTwPIqOjvDg2jZp5oj/s1600/20170516_151026.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh25wb-FSk3QoEJN4goDdD0sBFwgngWNOWx9NFXrapBvLPA_60RQFiVK2E0w8PAWJHLaOErTEz6yp6rw_sxSo3DJJuRhNeDcDS_uo6K6mH6tIxDVHUqlIl0puXxUXXTwPIqOjvDg2jZp5oj/s320/20170516_151026.jpg" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Shaft support block with bearing</td></tr>
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In the middle of assembling everything I decided I wanted to flip which side of the driver block was contacting the wall, which then made the support block dimension slightly off. I got two washers and pressed them into the pine wallplate with a vice until they were the correct height. </div>
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I made a set of 4 mounting blocks for the rails, which clamped them to the wallplate. These blocks were bandsawed in half after they were machined. </div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjrSiEF9UTBVY76P1AWjb6M7iMDGw1qa6Cqe9AeMlmvXIZqtOfXXZOuDWhLi92_ycK3traoPdFLllRrkPc99Q3Ad1OP6MDWrxI4LbUHWR4uAyaTZlVuvqxKvAslxbsfSPwvs6V99fKobqcz/s1600/drawing2.PNG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjrSiEF9UTBVY76P1AWjb6M7iMDGw1qa6Cqe9AeMlmvXIZqtOfXXZOuDWhLi92_ycK3traoPdFLllRrkPc99Q3Ad1OP6MDWrxI4LbUHWR4uAyaTZlVuvqxKvAslxbsfSPwvs6V99fKobqcz/s320/drawing2.PNG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Drawing for rail-mount blocks x 4</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcs9j1WLHOCglId_IkYWKTF17r-VcpiuqibkSNCOCmHDuwHLHFkgE6lfFsQBvWqwnmKu5Gl8_XH8fPYLVhg1UnoZJlwWcdctIeaZ6F3z29BglX9eqoUXmzfa6yGS2BDzpZTqQAEMUyqTJH/s1600/20170516_150457.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhcs9j1WLHOCglId_IkYWKTF17r-VcpiuqibkSNCOCmHDuwHLHFkgE6lfFsQBvWqwnmKu5Gl8_XH8fPYLVhg1UnoZJlwWcdctIeaZ6F3z29BglX9eqoUXmzfa6yGS2BDzpZTqQAEMUyqTJH/s320/20170516_150457.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A stack of blocks</td></tr>
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Everything was first horizontally assembled on the table to position holes in the wallplate, then bolts were fed through the holes, wallplate was screwed to the wall, and everything got reassembled in-space.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzIE3gEOCMLG2N14AM43HTnBScNiaM8zQfeAnX4PIaXGaJ0qYko_HO60hvbbHhTAvy-w9XO0UBuPTqVoVnP3CpSyGxTlD9YwB6GbeMh3fsNc_s6rLBOHmjIKzbk9alMaKipR55G7SRG_s_/s1600/20170515_172735.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgzIE3gEOCMLG2N14AM43HTnBScNiaM8zQfeAnX4PIaXGaJ0qYko_HO60hvbbHhTAvy-w9XO0UBuPTqVoVnP3CpSyGxTlD9YwB6GbeMh3fsNc_s6rLBOHmjIKzbk9alMaKipR55G7SRG_s_/s320/20170515_172735.jpg" width="240" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKkMbSwala-QZJ9nJFZtEhmrLqlsL0stD9Ewdtha3TfEuLjyzqG5ltxbmSTM6tWdG-66NLyxQvBH_7Z6nX8rTsDCVtsFyqd6bAXPFQBR_TfMSzo_D06_t0rSYhfEiy-odkT93SGmqm_Cql/s1600/20170515_172923.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKkMbSwala-QZJ9nJFZtEhmrLqlsL0stD9Ewdtha3TfEuLjyzqG5ltxbmSTM6tWdG-66NLyxQvBH_7Z6nX8rTsDCVtsFyqd6bAXPFQBR_TfMSzo_D06_t0rSYhfEiy-odkT93SGmqm_Cql/s320/20170515_172923.jpg" width="299" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCSLn7uQmPStRrqqPWRYCDK8rmecVdSvC_NVrJu-S4I7iJFCwdDLSxNRSSBuZX8IF9BAcy1R-ZBykZ8FfGxaSvgrPISzzIvBSct2EakeUqUSso5DiEmhqhzusM_sg5qNep5N5GW0bdodiq/s1600/20170516_150233.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCSLn7uQmPStRrqqPWRYCDK8rmecVdSvC_NVrJu-S4I7iJFCwdDLSxNRSSBuZX8IF9BAcy1R-ZBykZ8FfGxaSvgrPISzzIvBSct2EakeUqUSso5DiEmhqhzusM_sg5qNep5N5GW0bdodiq/s320/20170516_150233.jpg" width="320" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWD_-CX18vBHMXktR32sKPDo2wAhpljA_BqGrjDptFK9E4dYdxmY05GVaaoAaYTx41Ua6DwYvTQGGrmjGvmDcQACMI0NoZqvzRKSJbSBXoolJjH4yhg3_-Uo4f2Y0OgZidK3YAvjgpoexp/s1600/20170515_172517.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWD_-CX18vBHMXktR32sKPDo2wAhpljA_BqGrjDptFK9E4dYdxmY05GVaaoAaYTx41Ua6DwYvTQGGrmjGvmDcQACMI0NoZqvzRKSJbSBXoolJjH4yhg3_-Uo4f2Y0OgZidK3YAvjgpoexp/s640/20170515_172517.jpg" width="480" /></a></div>
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Vertical axis ready to accept the desktop!<br />
<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-63615151190850394162017-05-20T01:49:00.001-04:002017-05-20T02:11:58.676-04:00[2.70] Desk CAD Images<div class="separator" style="clear: both; text-align: left;">
CAD and renders in Solidworks: <a href="https://drive.google.com/file/d/0BzbyrnvMpW2heGdIVWFEaGIxYjQ/view?usp=sharing" target="_blank">downloadable zip here</a>.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhu7DpzF7hmNd14QniuDwd76Jgo_uyY-g5l_v8Gjc-BvDBzUVVHsk2a0yxH2zXlpRgl037OzBsK-CR8z1IHFT6e2oLtl-APwiQUklhhkGv-QmjA1Q53IdfOS8Cphy1MA2kT3_LQ7tUiBpxX/s1600/renderstructure.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="446" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhu7DpzF7hmNd14QniuDwd76Jgo_uyY-g5l_v8Gjc-BvDBzUVVHsk2a0yxH2zXlpRgl037OzBsK-CR8z1IHFT6e2oLtl-APwiQUklhhkGv-QmjA1Q53IdfOS8Cphy1MA2kT3_LQ7tUiBpxX/s640/renderstructure.JPG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Vertical Axis Module</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgA0tmO6grLl7BonJ4g9h4RseMnsOngOSfbL5NM4Z3mDjVq-n2JFIl3XBdZnIFgx2u5JqhdYeFKvb3jFsHoQEr8j8jJ7ic58Qx57hZNAV6OcDJW7U-TdY07cYhxrhoCYzwbyMoCUYG3uczf/s1600/renderfront.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="528" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgA0tmO6grLl7BonJ4g9h4RseMnsOngOSfbL5NM4Z3mDjVq-n2JFIl3XBdZnIFgx2u5JqhdYeFKvb3jFsHoQEr8j8jJ7ic58Qx57hZNAV6OcDJW7U-TdY07cYhxrhoCYzwbyMoCUYG3uczf/s640/renderfront.JPG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Front view</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwVVEa0i3pfrzoWkNj5ZUYSoHd9jevc-whetjWB9959S6b_2ksPxEQkzGNdkuSmdq29GblViR7cBfMkpU0NKS1Uyxv3SYcrtpcJEgF_XCTv2E2IoHTEM0MOU033QKDJDidvGiJFBnNyk4P/s1600/renderback.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="576" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwVVEa0i3pfrzoWkNj5ZUYSoHd9jevc-whetjWB9959S6b_2ksPxEQkzGNdkuSmdq29GblViR7cBfMkpU0NKS1Uyxv3SYcrtpcJEgF_XCTv2E2IoHTEM0MOU033QKDJDidvGiJFBnNyk4P/s640/renderback.JPG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Rear view, wall plate transparent to show structure</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7nhXHsq4Yc3hP3usIOO3vPjxJHm8NPh49Kp3fc37iH1V2MmkJOCT1pj5FmqGfy1Ai7c6oyU4CYAeTTUHJGKBUB_krRGA4mgpxZHy8tIM_Km9p5elqbQzG0xX1aO3hyVkEDy5gsdHmo2Px/s1600/renderside.JPG" imageanchor="1" style="clear: left; float: left;"></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUdMSV9XIX2o0j4By9pcqtgEOQjY68NsohKWvvdIK7fmI4PWwUaqm8TCkK4Sue__TgKyNVO5RVSHkjck20lGhF-wvAp7ACT1B13sGlntL0dunO_qnTkbwTQ-aIJWy0C6VFx3cp0Z_aopGy/s1600/renderiso.JPG" imageanchor="1" style="clear: right; float: right;"><img border="0" height="254" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUdMSV9XIX2o0j4By9pcqtgEOQjY68NsohKWvvdIK7fmI4PWwUaqm8TCkK4Sue__TgKyNVO5RVSHkjck20lGhF-wvAp7ACT1B13sGlntL0dunO_qnTkbwTQ-aIJWy0C6VFx3cp0Z_aopGy/s320/renderiso.JPG" width="320" /></a><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7nhXHsq4Yc3hP3usIOO3vPjxJHm8NPh49Kp3fc37iH1V2MmkJOCT1pj5FmqGfy1Ai7c6oyU4CYAeTTUHJGKBUB_krRGA4mgpxZHy8tIM_Km9p5elqbQzG0xX1aO3hyVkEDy5gsdHmo2Px/s320/renderside.JPG" width="320" /></div>
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<span style="font-size: x-small;">Side view (left) and iso view (right)</span></div>
Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-90140297630442210752017-04-28T01:25:00.000-04:002020-08-27T19:47:19.511-04:00[2.70] Seek and Geek #10: BallscrewSummary: Hardware debugging is a lot like code debugging, but involves more acetone.<br />
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I had acquired a ballscrew assembly from one of the loading docks, and was really excited about using it as the main actuator for this desk. (This is the same ballscrew from <a href="http://inkandbolts.blogspot.com/2017/02/270-seek-and-geek-week-1.html">Kris's first seek&geek</a>) Even though there was no obvious part number or datasheet, I could estimate the stiffness by looking at similar ballscrews and felt pretty happy using this approximation in the rest of my calculations.</div>
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The ballscrew assembly has been sitting on my bookshelf for years with the same wrapping I found it with - paper towels and packing tape. This week I took off the wrapping and started dimensioning things... and started this very wild ride.<br />
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<tr><td class="tr-caption" style="text-align: center;">Ballscrew assembly pre-shenanigans</td></tr>
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Long story short, I accidentally discovered the true reason it was wrapped up. I had thought the towels were simply to prevent dust from getting in the bearings, but the true reason was to prevent pine resin from contaminating everything else!<br />
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At the base of the ballscrew where the supporting block bearing is, there was a glob of pine resin. In my excitement to measure all the dimensions, I had allowed the ball nut to sink into this resin. So suddenly, the entire assembly was seized!<br />
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In retrospect, what I should have done was soak the entire assembly in acetone to dissolve all the grease and resin. But, for some reason, I thought there would be rubber or plastic components that would be unhappy with the solvent bath. So I painstakingly took everything apart, soaked everything in acetone, reassembled the pieces, and finally relubricated all the parts!<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhiM6brMAmzi4AFQaeViQ6mw29NTeRblk0cFNiB2SCyVYOCjUBRU2JsYE4ICZp1IL-kOhLhhNAZt48nDqosXmdih6s8KBtgmFMAI7-XJlpqIeu13xPvyKgt14UdYHELyi9MTQaMarJNiDtn/s1600/20170425_013157.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="188" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhiM6brMAmzi4AFQaeViQ6mw29NTeRblk0cFNiB2SCyVYOCjUBRU2JsYE4ICZp1IL-kOhLhhNAZt48nDqosXmdih6s8KBtgmFMAI7-XJlpqIeu13xPvyKgt14UdYHELyi9MTQaMarJNiDtn/s640/20170425_013157.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Fixing my mistakes</td></tr>
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First discovery: the two bearings in the driver block are in a face-to-face configuration. They use 8mm ID flanged bearings, where the outer flange is held in place and the inner races are preloaded by a torqued nut compressing them against the 12mm screw.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxXnmEQJsmihooZ3f8jcpgw_p1u08L9Md3lX3F0GZqGorCbesiBPYEJHlrLKAILVIyrekPShM8xSa1i8H9YyjZeO-UwCHlb2pAJ0r51flAag0JaT9Umt9jrN5AMORWlT7oDA-IaWQy2ue2/s1600/Untitled.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxXnmEQJsmihooZ3f8jcpgw_p1u08L9Md3lX3F0GZqGorCbesiBPYEJHlrLKAILVIyrekPShM8xSa1i8H9YyjZeO-UwCHlb2pAJ0r51flAag0JaT9Umt9jrN5AMORWlT7oDA-IaWQy2ue2/s320/Untitled.png" width="233" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Bearing diagram. Solid lines are outer diameter (outer races), dashed lines are inner races, r<br />
ed lines are approximations of ball contact forces and directions</td></tr>
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The face-to-face configuration has more compliance against rolling moments, which makes it more forgiving with misalignment (4x less sensitive to roll than the back-to-back configuration). Assuming maximum race deflection of these ball bearings is 15<span style="background-color: white; color: #222222;"><span style="font-family: inherit;">μm under nominal max load of 3300N, linear stiffness should be $</span></span><span style="text-align: center;">2.2 \cdot 10^6 \frac{N}{m}$, making</span><br />
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$K_(moment) = \frac{K_(linear) L^2}{4} = 3.1\cdot10^4 \frac{N}{m}$</div>
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So that's neat. The next component in the stack is a steel washer. This item was supposed to prevent the ball of resin from gooping up the bearings below, but when the ballnut plunged into the resin it brought up this guy with it.<br />
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Next up was reattaching the shaft. The end of the ballscrew had a really fine thread, which got slightly damaged by me pressing the shaft back on. I used a knife to gently nudge the threads back in place, so I could reattach the nut. There's also a washer on the front end of this assembly that protects the inner races of the bearings from resin goop.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjyla8vVW1fiLqkFBsFt2pJq7yX9U1ZhPiNAJWhbdNDIp9Zotpg__4BmrXTdzWGTn09tHKWUiG_RofmuebPuJatRS9CPY4cnDJnu5X-MzzqlzUo5zrzdjX6cy5Wu2jRQFbY5UnakkND_s9H/s1600/20170425_013729.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjyla8vVW1fiLqkFBsFt2pJq7yX9U1ZhPiNAJWhbdNDIp9Zotpg__4BmrXTdzWGTn09tHKWUiG_RofmuebPuJatRS9CPY4cnDJnu5X-MzzqlzUo5zrzdjX6cy5Wu2jRQFbY5UnakkND_s9H/s320/20170425_013729.jpg" width="320" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxQNuNuiQYgJn6_SaqGnu7aDpZRkws5WoLXfT84Y_0by6X5hkF4DMR77Yx2SACWSMWs12wAUgzHUKpDTaGr365yXVajPX74tEAO1phbjY686bJSvNcTbjgm8uZOih67FSCtfa96PbBPm9b/s1600/20170425_020415.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxQNuNuiQYgJn6_SaqGnu7aDpZRkws5WoLXfT84Y_0by6X5hkF4DMR77Yx2SACWSMWs12wAUgzHUKpDTaGr365yXVajPX74tEAO1phbjY686bJSvNcTbjgm8uZOih67FSCtfa96PbBPm9b/s320/20170425_020415.jpg" width="240" /></a></div>
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I replaced the resin goop ball with a blob of lithium grease. Probably this was unnecessary.<br />
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Next up was re-assembly hell. Luckily for me, this ballnut uses an external ball-return-plate. Otherwise I doubt I would have been able to repair this item (or maybe I would've come up with the better idea of dunking the whole assembly in acetone first).<br />
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There were originally 50 balls, 2.3mm diameter. Unfortunately I lost one in the repacking process :(<br />
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Repacking the balls involved picking them up with tweezers, packing them in the channel, then feeding the shaft such that the balls were evenly spaced. I did this five times in the process of hardware debugging.<br />
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Next up was lubrication. Chain oil was too clingy, Tap-magic too light, but machine oil worked fine.<br />
Never again! But, the ballscrew lives! And now I feel justified using this reuse ballscrew in the desk.<br />
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This is what the balls are doing on the inside.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCnWZRIdFWG56FQxgDKxH3lsVFqO4mrl7MBqzBavskt3qgjkdd2VBAdJ9UvRZSbdsABi_pnLVI-xaFUC9Oc4Tyk_PS5UbY-cCEQA85Ae1ce55oBb0x4kwKf2w2SSl37usE0_HUBVyQpfOC/s1600/Untitled1.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="298" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCnWZRIdFWG56FQxgDKxH3lsVFqO4mrl7MBqzBavskt3qgjkdd2VBAdJ9UvRZSbdsABi_pnLVI-xaFUC9Oc4Tyk_PS5UbY-cCEQA85Ae1ce55oBb0x4kwKf2w2SSl37usE0_HUBVyQpfOC/s400/Untitled1.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Modified from <a href="http://www.barnesballscrew.com/how-a-ball-screw-works/" target="_blank">barnesballscrew.com</a></td></tr>
</tbody></table>
We can take a guess at load capacity of the ballnut knowing how many there are (too many!) and their diameters. First, taking a look at contact pressure.<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRMpH6HBy4su876t9JeBf1FJXhtkaYr9l6QdbKviVioDiZdzuxVyfr2zae9un5YKLcKWva08wxpibuIBUhnuGLQR4vEnL2oxNeFO_qRy55CsvfK2EBrtJmYmDOX7mcUlBfepQrmU9oVAet/s1600/Untitled2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="168" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRMpH6HBy4su876t9JeBf1FJXhtkaYr9l6QdbKviVioDiZdzuxVyfr2zae9un5YKLcKWva08wxpibuIBUhnuGLQR4vEnL2oxNeFO_qRy55CsvfK2EBrtJmYmDOX7mcUlBfepQrmU9oVAet/s320/Untitled2.png" width="320" /></a></div>
<br />
Maximum contact pressure can be approximated with<br />
<div style="text-align: center;">
$P_(max) = \frac{P_(load)}{\frac{\pi}{2}r}$,</div>
<div style="text-align: left;">
where we need to take care to not exceed the Brinell hardness... that's how bearings fail! Assuming the bearings are 52100 bearing steel, hardness should be ~200 BHN. </div>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPTfKHzeXFt244p9var923cgigFGqgeCC4rLz0pN73TA2GcmMV17huVskGg6QZkCztO5W95GgAicPcmIhU7BwZ5ijbb5vYOqt3rcaeMkStQ7h2-9s1sNNyJgZFVIL_VFYppFd3RK65Xs-C/s1600/Capture5.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="207" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjPTfKHzeXFt244p9var923cgigFGqgeCC4rLz0pN73TA2GcmMV17huVskGg6QZkCztO5W95GgAicPcmIhU7BwZ5ijbb5vYOqt3rcaeMkStQ7h2-9s1sNNyJgZFVIL_VFYppFd3RK65Xs-C/s320/Capture5.JPG" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">(wikipedia)</td></tr>
</tbody></table>
So for these balls, $P_(max)$ < 11.2 N per ball, for a total load capacity of 550N, or 123lbs. That means no attempting to stand on the ballnut by itself.</div>
Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com2tag:blogger.com,1999:blog-5736103898080682832.post-82454687428919531092017-04-17T22:51:00.002-04:002017-04-17T22:51:38.766-04:00[2.70] Cardboard Concept Desk<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3e1w8V_DMCwWYvw76ChAwK2h-e1TPPiRj4xjd2O4kl7gV2hnZ4wyYh2miBiihiV81vsYVR1VzbSA8canVqMgCwhs_h4_I1aSGMjR0BBOZb-3fZO4qt8wpIWtCBt41bVh0i-uL1B6zih3x/s1600/20170416_002611.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3e1w8V_DMCwWYvw76ChAwK2h-e1TPPiRj4xjd2O4kl7gV2hnZ4wyYh2miBiihiV81vsYVR1VzbSA8canVqMgCwhs_h4_I1aSGMjR0BBOZb-3fZO4qt8wpIWtCBt41bVh0i-uL1B6zih3x/s640/20170416_002611.jpg" width="640" /></a></div>
<div>
<br /></div>
<div>
<br /></div>
Modeling a concept desk out of cardboard, just as a quick stupid-check before designing components in detail.<br />
<div style="text-align: center;">
<br />
<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/213466833?portrait=0" webkitallowfullscreen="" width="640"></iframe><br />
<br />
<div style="text-align: left;">
The goal here was to see what this desk idea would look and feel like, without worrying about geometrical tolerances. I also played around with adding trusses to the interior of the desk (and added a drawer!)</div>
<div style="text-align: left;">
<br /></div>
<div style="text-align: left;">
Construction was all hot-glued corrugated cardboard, with the exception of the <a href="http://www.avamakesthings.com/search/label/linear%20axis">simple linear axis</a> which makes a final reappearance here. So, the vertical column was assumed to have substantially higher stiffness than the rest of the cardboard desk.</div>
<div style="text-align: left;">
<br /></div>
<div style="text-align: left;">
Adding more thickness (box drawer) to the desk significantly helped improve moment of inertia and reduce deflections, but I don't think the interior trusses contributed much. I think future desk might scrap the truss idea in favor of having just clean box walls.</div>
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEF9JDvZQVJia3E2Ln8u2NCmN6MUmUE2Au0JSUO0BM9XVrSlLPAO-rRulHjUpr7YIXlWj9vbraa4meWxns000j_ccMRxzQUwJ6dnPd9lKPsZWNxyjsOZz_0eR71_5UG8T942Q9BP4lfogm/s1600/20170416_002746.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiEF9JDvZQVJia3E2Ln8u2NCmN6MUmUE2Au0JSUO0BM9XVrSlLPAO-rRulHjUpr7YIXlWj9vbraa4meWxns000j_ccMRxzQUwJ6dnPd9lKPsZWNxyjsOZz_0eR71_5UG8T942Q9BP4lfogm/s640/20170416_002746.jpg" width="640" /></a></div>
<br />
Derp-cardboard desk's only attachment to the carriage was via hot-glued foamcore, and clearly future desk will need a more load-bearing attachment system. Surprisingly, hotglue held the desk and 200g of motor components just fine.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBvOC9mdsT9GI82Aa56F7TogujrBQXHsD0lZBea_9YLUjI2Gf_7192PsMVozHDCPogq4UYkGb_WI9dY3iwrfmNOAUutqYIA-CeDvzenZLu_UIZ7T3so35RxbuoqwyVbn4YfCrZm5gbZuDm/s1600/20170416_002800.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgBvOC9mdsT9GI82Aa56F7TogujrBQXHsD0lZBea_9YLUjI2Gf_7192PsMVozHDCPogq4UYkGb_WI9dY3iwrfmNOAUutqYIA-CeDvzenZLu_UIZ7T3so35RxbuoqwyVbn4YfCrZm5gbZuDm/s640/20170416_002800.jpg" width="640" /></a></div>
<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
Real desk will also likely be a wall-mounted desk, for simplicity.Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-16997902526882105792017-03-30T18:47:00.004-04:002020-08-27T19:53:47.473-04:00[2.70] Linear Axis v2<div class="separator" style="clear: both; text-align: left;">
Finally hooked everything up and ran the tests! </div>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: left;">
<b>TL;DR</b>: This linear axis system has position error of 0.44mm, with only 3.5<span style="background-color: white; color: #222222;"><span style="font-family: inherit;">μm error resulting from backlash. It falls within the desired error budget of 0.5mm, at least in the no-load condition.</span></span></div>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi50Ve_XVTpGX4ezDl5NFD6TfMSgMV0oDVCWSW-LWGzFDgaltobdqet-KJFV-uTqD-ZWvdo_COGcWAx80JOYyH9XNklSithxsO9DlmWK3c20efaqaKJIEBvRFl_8ccVLmWfA-0Gqv9jSzhU/s1600/20170324_145700.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi50Ve_XVTpGX4ezDl5NFD6TfMSgMV0oDVCWSW-LWGzFDgaltobdqet-KJFV-uTqD-ZWvdo_COGcWAx80JOYyH9XNklSithxsO9DlmWK3c20efaqaKJIEBvRFl_8ccVLmWfA-0Gqv9jSzhU/s640/20170324_145700.jpg" width="640" /></a></div>
<br />
So this is what the setup looks like - I have my linear stage on a desk, and the laser shines on a piece of paper far (4.5m) away. I took three tests:<br />
<br />
<ol>
<li>Command the stepper motor to move 5000 counts forwards and backwards, and find out what distance this is (turning off the power supply between each jump)</li>
<ul>
<li>testing ability to reliably move a set distance</li>
<li>measure open-loop error when turning on the system</li>
</ul>
<li>Command the stepper to jump (each 5000 counts) forwards 4 times, then to jump backwards 4 times (leaving power supply on)</li>
<ul>
<li>testing ability to return to a position</li>
</ul>
<li>Command the stepper to bounce between two positions (bouncing </li>
<ul>
<li>measure cumulative backlash error</li>
</ul>
</ol>
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwrl4-ZoyTSDmSEX2URyqAtKXPxZUpXkk0Rhla8EuB7zrxY3uoDfbNCrKnt-bJXs67qOkfdraLT3asT_AX0oYPSY8gcVsO8EzlWMQTxB1zJ0doI2DQld94uyHHQO9xMXpHmFp3hbR-ARSk/s1600/diagram.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwrl4-ZoyTSDmSEX2URyqAtKXPxZUpXkk0Rhla8EuB7zrxY3uoDfbNCrKnt-bJXs67qOkfdraLT3asT_AX0oYPSY8gcVsO8EzlWMQTxB1zJ0doI2DQld94uyHHQO9xMXpHmFp3hbR-ARSk/s640/diagram.png" width="640" /></a></div>
<div class="separator" style="clear: both; text-align: left;">
</div>
<ul>
<li>Distance from "zero" point of rail to wall "L"= 449cm</li>
<li>Travel distance of the linear axis "x" is defined differently every test</li>
<li>"Radius" of the most sensitive part of the carriage "r" = 20mm</li>
<li><span face="" style="background-color: white; color: #222222;">α</span><b style="background-color: white; color: #222222; font-family: "sbl biblit", "sbl greek", "dejavu sans", "dejavu serif", freeserif, freesans, athena, "gentium plus", gentium, "palatino linotype", "arial unicode ms", "lucida sans unicode", "lucida grande", code2000, sans-serif; font-size: 14px;"> </b> and δ are resulting angular and distance errors projected onto the wall, from which we can measure machine error "err" of this linear axis</li>
</ul>
<div style="text-align: center;">
<span style="font-size: large;">$\alpha = \frac{\delta}{L} $</span></div>
<div style="text-align: center;">
and</div>
<div>
<div style="text-align: center;">
<span style="font-size: large;">$err = \frac{\delta x}{L+ x} $</span></div>
<br />
Where for the purposes of my experiments, I assume all projected error comes from distance errors, even though some constant portion of it comes from angular error instead. (My analyses farther down ignore angular errors)<br />
<br />
((For the results of these experiments, skip to the end))</div>
<div>
<br /></div>
<div>
Linear Axis v2 accomplishes two things. First, it has an actuator (nema17 stepper motor + 1/4-20 threaded rod), which allows me to send distance commands. Second, it has an anti-backlash device so switching directions accumulates less error.</div>
<div>
<br /></div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjq7loxnBkSYA5U2vx2KnZF4ZQ3gcxZJM1kDryJUgwzAnq0xTrRPncicFGGKp0OZ_YTybWZqAse192jGOfniGvaWUTPmEYShUCLqA5zcuHuSuC0zkBcRApCZzW1hZwzGUKrcBtae4WKpVh6/s1600/20170327_161543.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="224" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjq7loxnBkSYA5U2vx2KnZF4ZQ3gcxZJM1kDryJUgwzAnq0xTrRPncicFGGKp0OZ_YTybWZqAse192jGOfniGvaWUTPmEYShUCLqA5zcuHuSuC0zkBcRApCZzW1hZwzGUKrcBtae4WKpVh6/s320/20170327_161543.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Me planning out components for this actuator (ended up buying a flexible coupling instead of making one)</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjU_1MhVm0jN_BqBQD7ZSXzRwB3tpArpFQmkczs7amrP9cBZUPoKkyocAyowYz0GmVF63bbt8j6H4TeZe7GorQMvxuWmDN3u5ar5ygHlwLOHpatNkQGq_l-zkTosIVdDgjqS6sK3QLwKReL/s1600/20170327_161549.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjU_1MhVm0jN_BqBQD7ZSXzRwB3tpArpFQmkczs7amrP9cBZUPoKkyocAyowYz0GmVF63bbt8j6H4TeZe7GorQMvxuWmDN3u5ar5ygHlwLOHpatNkQGq_l-zkTosIVdDgjqS6sK3QLwKReL/s400/20170327_161549.jpg" width="360" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Some machining notes</td></tr>
</tbody></table>
<div>
This version2 reuses most of the parts from v1, with some modifications. I replaced one of the steel rails with a 1/4"-20 threaded rod, and added some bushings to the bearing blocks to accommodate the new diameter. I also made a plywood stand to put all the things on so I could use the linear axis without needing an empty optical table.</div>
<div>
<br /></div>
<div>
The big new thing here is the carriage for this threaded rod. Its anti-backlash system uses two adjustable-offset nuts for its preload. The threads of one of the nuts will always* be contacting the threads of the rod when traveling in either direction.</div>
<div>
<br /></div>
<div>
(* not actually always; since these are hand-tightened there will be some amount of user error here) </div>
<br />
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7C-N6HZFv-qN62gRsw0gQ1mQZBbKmXZDrpGkGrUenWS1-xf-L_wsZbbECZsK1dlNdII-EQbL1ITLMb3hpoAA3BDr4xei5PX0Sb-rUvcZjnZWOTee_SIPfOugpGadUV4LsaTSL8PpheNL5/s1600/20170324_150135.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7C-N6HZFv-qN62gRsw0gQ1mQZBbKmXZDrpGkGrUenWS1-xf-L_wsZbbECZsK1dlNdII-EQbL1ITLMb3hpoAA3BDr4xei5PX0Sb-rUvcZjnZWOTee_SIPfOugpGadUV4LsaTSL8PpheNL5/s400/20170324_150135.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Carriage and modified bearing block</td></tr>
</tbody></table>
The fixed part of the carriage consists of a milled aluminum block with a tapped hole on one side and an oversized-slot on the other. The HDPE wedge and its brass threaded-insert floats within the slot and gets pushed outwards by one of the adjustment screws (the other one keeps the wedge centered)<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvMcHpShtwxSEO1E-YLVidBYJEYERrOu-P9pqGejcX20ikhC4iYP9b0c5CX7DkXOZvWhTmz95DHpXjzOMaT96bDxU3IWTifoj5zuUm0jYcZzUjQrOcEFlDyZrFXOPw7fN2ngu0zEK0tNEt/s1600/20170324_150405.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvMcHpShtwxSEO1E-YLVidBYJEYERrOu-P9pqGejcX20ikhC4iYP9b0c5CX7DkXOZvWhTmz95DHpXjzOMaT96bDxU3IWTifoj5zuUm0jYcZzUjQrOcEFlDyZrFXOPw7fN2ngu0zEK0tNEt/s400/20170324_150405.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Carriage!</td></tr>
</tbody></table>
<br />
<div>
I chose to replace one of the rails with this actuator, which has some advantages and disadvantages compared to having two rails with the actuator in the center.</div>
<div>
<br /></div>
<div>
<b>Two Rails, with Actuator acting as Rail</b></div>
<div>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqySmpYyUqxvB6k0KbgLJWKl1nW45gTWJBqY3e-chGFvYZnKXkU6kkdWMYbVRva0NncpQeql9uZm_YXsMf1TflaRRmTYPUtsYCPaR0asqtEvkUjcXTHPwo-H1ZUxmJ9l0wwzYo3y7c_erm/s1600/drawing1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="384" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqySmpYyUqxvB6k0KbgLJWKl1nW45gTWJBqY3e-chGFvYZnKXkU6kkdWMYbVRva0NncpQeql9uZm_YXsMf1TflaRRmTYPUtsYCPaR0asqtEvkUjcXTHPwo-H1ZUxmJ9l0wwzYo3y7c_erm/s640/drawing1.jpg" width="640" /></a></div>
<br />
Advantages:</div>
<div>
<ul>
<li>Much easier to build with the preexisting parts</li>
<li>Don't have to worry about overconstraint from the two other rails</li>
</ul>
<div>
Disadvantages:</div>
</div>
<div>
<ul>
<li>Sensitive to threaded-rod imperfections, especially in roll</li>
<li>Actuator will always apply a moment, which magnifies error</li>
</ul>
</div>
<div>
<b><br /></b></div>
<div>
<b>Two Rails + Actuator in Center</b><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJr2WfHG835IJ4IrrVFVJc4aN9H8cvmTFc6ejuWfERSm5Ax5i_zxtKuHd5kd9Cz2bRl4aLC5vsxkaGWoXHrGLRxwgSDQqfA6mQupYlaAIBPxhEnmd1IV3lx1iai_6dlo-y5JfbyYmg_Z2b/s1600/drawing2.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="384" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJr2WfHG835IJ4IrrVFVJc4aN9H8cvmTFc6ejuWfERSm5Ax5i_zxtKuHd5kd9Cz2bRl4aLC5vsxkaGWoXHrGLRxwgSDQqfA6mQupYlaAIBPxhEnmd1IV3lx1iai_6dlo-y5JfbyYmg_Z2b/s640/drawing2.jpg" width="640" /></a></div>
<b><br /></b></div>
<div>
<div>
Advantages:</div>
<div>
<ul>
<li><a href="http://www.avamakesthings.com/p/270_15.html" target="_blank">A more fundamentally-kinematically precise solution</a> (we did a board problem on this)</li>
<li>Can use parts with larger manufacturing tolerances and still achieve good performance</li>
</ul>
<div>
Disadvantages:</div>
</div>
<div>
<ul>
<li>Have to take care to add compliance to avoid binding from overconstraint</li>
<li>Not as easy to modify v1 rail to accomplish vs. the other method</li>
</ul>
<div>
Now for experiments! I used a standard nema17 stepper and an Arduino microcontroller, so nothing fancy. </div>
</div>
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(A stepper motor is a brushless DC motor that divides a full rotation into an equal number of steps, so they will precisely rotate a fixed rotor angle without needing feedback. They usually do this by having tooth-shaped electromagnets and a gear-shaped rotor.)</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjizzuMS5a5HU8Za1pptmE0DYWkJnYEUKaigrUM9OWdWcsqnMHXD5JedoRhyphenhyphenW5DWhgmRVrzAwQxm-zn4u8YDhHk-JqxueuBAQtsAeO-0x8qgzG14zNR280uPQuajD6r5olGcZmh-QvVEnDi/s1600/20170328_112456.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" height="468" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjizzuMS5a5HU8Za1pptmE0DYWkJnYEUKaigrUM9OWdWcsqnMHXD5JedoRhyphenhyphenW5DWhgmRVrzAwQxm-zn4u8YDhHk-JqxueuBAQtsAeO-0x8qgzG14zNR280uPQuajD6r5olGcZmh-QvVEnDi/s640/20170328_112456.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Did I bring my 2.70 work and my calipers on a plane to Sweden? Yes, yes I did.</td></tr>
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<div>
<b>Results!</b><br />
<b>Experiment 1 - Turn on power to the system, command a set distance, turn power off</b></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0x0TUbwGAxVkBA-XIiiWwa4KIZt2k4v6YVJn-nvh53QIdAaf2106qAu1QvG3xb_iOAZfYbJ3jtvWDC76TQeNPQ6a4akqAzX1B4DNQM9S0frpQJjWqEn-njjnXKODjhJF1m3CqK2hDuAAv/s1600/diagram1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="80" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh0x0TUbwGAxVkBA-XIiiWwa4KIZt2k4v6YVJn-nvh53QIdAaf2106qAu1QvG3xb_iOAZfYbJ3jtvWDC76TQeNPQ6a4akqAzX1B4DNQM9S0frpQJjWqEn-njjnXKODjhJF1m3CqK2hDuAAv/s320/diagram1.png" width="320" /></a></div>
The carriage started at position 2.2cm. I programmed it to move 5000 stepper counts, then turned the power on and let the program run. Once the carriage stopped (5.3cm), I turned the power off. </div>
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I flipped the direction and did this again, for a total of three trials (2 forwards, 1 backwards)</div>
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Looking at a ruler next to the moving carriage, it seems like the machine consistently moves 3.1cm per 5000-count jump. Looking at the laser deviations, we can get a better error resolution. The standard deviation for the three jumps was 1.54mm and the magnification for this experiment was 120.7. So, for this experiment the machine moves 3.1cm with an error of 12.8<span face="" style="background-color: white; color: #222222;">μ</span>m - pretty consistent commutation by the motor.<br />
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The Arduino is a generalist microcontroller, and when first powered on it briefly supplies 5V to all its logic pins. This slightly energizes the stepper motor on startup and causes additional error between what should be identical (or within 1.5mm on paper) landing points. This error was an average of 15.7<span face="" style="background-color: white; color: #222222;">μ</span>m, of which approx. 3<span face="" style="background-color: white; color: #222222;">μ</span>m should be start-up error.</div>
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<b>Experiment 2 - Motor moves forwards, with pauses to measure distance traveled. Turn off power and restart. Then motor moves back to the starting point, again with pauses.</b><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJ6sTRkWLZIuZ4wf5UhXBAhmzTXsYOqN_d1MS_eyYddOdGMUmoe5Mtc1eH4K4LD9IXejJfR1h0D9T7AkbheYF8wSOcg-kNArk5IMsz4bW8KhW2dWlJ1S2jYi3zuGdV9xXVeQPXwgw0wxo2/s1600/diagram3.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="108" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiJ6sTRkWLZIuZ4wf5UhXBAhmzTXsYOqN_d1MS_eyYddOdGMUmoe5Mtc1eH4K4LD9IXejJfR1h0D9T7AkbheYF8wSOcg-kNArk5IMsz4bW8KhW2dWlJ1S2jYi3zuGdV9xXVeQPXwgw0wxo2/s320/diagram3.png" width="320" /></a></div>
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The carriage started at position 13.5cm. It moved four times, each time 5000-counts (nom. 3.1cm) and ended at position 2.2cm. This distance seemed a bit short, being an average 2.825cm instead of the expected distance. The system was turned off and reprogrammed to move backwards four times, again 5000-counts but ended at position 14.7cm - giving an average jump-distance of 3.125cm.<br />
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This is exciting. From Experiment1, we determined that turning the system on gives ~3<span face="" style="background-color: white; color: #222222;">μ</span>m error, and movement will have an average error of 13<span face="" style="background-color: white; color: #222222;">μ</span>m per jump. This machine error projected on the wall should give us an expected average jump error of 1.65mm. Experiment2's average jump-distance is off from our expected 3.1cm by 0.25mm and falls within the expected amount of error.<br />
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Experiment2 also allows me to measure average error of returning to a position. This ended up being 0.44mm error for my travel range of ~12cm, which is within my original desired error budget (500<span face="" style="background-color: white; color: #222222;">μ</span>m) for this machine. Woo!<br />
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While the carriage was moving, the laser dot moved back and forth on the page. This is partially due to vibrations transmitted by the motor, partially from contact vibrations between the carriage nut and the threaded rod, and partially from the laser pointer only being taped onto the carriage bed. The tip of the laser pointer displaces 0.115mm from these vibrations. </div>
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<b>Experiment 3 - Motor travels back and forth between two points, with pauses for recording position</b><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjn5Qsefcw_iMGy8Ddvk2zdGvUTQUcgrD1RUT6WxF7fo8HK1zmxsP6sfdgRrwCYR-i-2m4VL6B-8qxzhBOBDAeno0Roqs1vYe_qaqYi9lj4wzZ-Z-nXaESTEJkuNEDGBZJx6JV6lx3QLbmc/s1600/diagram2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="102" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjn5Qsefcw_iMGy8Ddvk2zdGvUTQUcgrD1RUT6WxF7fo8HK1zmxsP6sfdgRrwCYR-i-2m4VL6B-8qxzhBOBDAeno0Roqs1vYe_qaqYi9lj4wzZ-Z-nXaESTEJkuNEDGBZJx6JV6lx3QLbmc/s320/diagram2.png" width="320" /></a></div>
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The carriage started at position 6.6cm. Moving forwards and backwards 5000-counts, it consistently landed at positions 6.6cm and 3.4cm (5 trials) so traveled 3.2cm distances, not 3.1cm. So that's odd given the results of the other two experiments, but at least it's repeatable here.<br />
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Position error for this experiment was an average of 3.4<span face="" style="background-color: white; color: #222222;">μ</span>m, which means my machine is pretty good at rejecting backlash. While the carriage was moving, the tip of the laser wobbles 38<span face="" style="background-color: white; color: #222222;">μ</span>m (I did a better job clamping down the base platform for this experiment)</div>
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<b>Bonus Analysis - Angle of linear axis machine relative to the wall</b></div>
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From Experiment3, we see that the the entire linear axis system is not quite square* with the laser paper (if it were square, there would be no systematic difference between the front measurements and the rear measurements). If we assume this discrepancy is entirely due to angular** error relative to the wall, we can get an estimate of what that angle is.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKNR6eIekl3ZXCyx9YLHIO_7rxs3Fbp4YxGg_JSVTEH_M9OcTWV0a8WbEMPLBuNs9sMMTWyEOLyC2YV2RyJHIHuJTOqw4B2DVKqea56hhgqlCMv4K95TUlBTgWKZroxbSRZ1sf1Gv_BHAS/s1600/diagram4.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="285" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKNR6eIekl3ZXCyx9YLHIO_7rxs3Fbp4YxGg_JSVTEH_M9OcTWV0a8WbEMPLBuNs9sMMTWyEOLyC2YV2RyJHIHuJTOqw4B2DVKqea56hhgqlCMv4K95TUlBTgWKZroxbSRZ1sf1Gv_BHAS/s320/diagram4.png" width="320" /></a></div>
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<div style="text-align: center;">
<span style="font-size: large;">$\theta = tan^{-1}(\frac{\Delta }{x}) = 0.28^\circ$</span></div>
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$\Delta$ is the distance between the average front and back points (3.4cm and 6.6cm, resp.) multiplied by Experiment3's magnification factor. This angular error seems around right for lining things up using the floor tiles.<br />
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*I know that the laser pointer itself is not colinear with the axis-direction-of-travel... but I'm just combining this angular error with the main one and calling the whole thing "machine error"<br />
**I'm also assuming my system didn't move between/during experiments, which probably isn't true.<br />
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Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0tag:blogger.com,1999:blog-5736103898080682832.post-89025781019667716132017-02-27T16:04:00.002-05:002017-02-27T16:24:00.266-05:00[2.70] Simple Linear Axis<div class="separator" style="clear: both; text-align: left;">
For this assignment, we were told to go forth and create a linear motion axis built from scrap and then measure its precision. I had some leftover 8mm steel rod from what used to be 3D-printer materials, so I decided to make a small linear rail out of that. These rods were only 30cm long and rather thin for desk material, so I'm treating this one more like a scale model. I can use this to see what I can improve for the real thing.</div>
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With round straight steel rod as my rails, I have two main concerns to address:</div>
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<li>Fabricate rail holders to maximize parallelism of the rods</li>
<li>Make a carriage to achieve best slidey-ness/load capacity with least effort/wobbliness</li>
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The rail holder objective is fairly straightforward, but the carriage requires some thought. Generally the more constrained you make a slider, the less load capacity it gets (before you get friction problems)</div>
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I decided to see how far I could get with a circular-bore carriage (slider on one rail has cylindrical bores, and the other rail just has a flat.) Fundamental failure modes of this design will be angular wobbliness in the xy-plane (parallel to the base, but would move a laser beam side to side), since a slip-fit circular bore inherently will allow side-side play. However, such a design would prevent the carriage from lifting off the rail and I could later reduce angular errors with a preloading mechanism. Also, this design is really easy to machine.</div>
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Below is some scratchwork:</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9MSkawQMtTlmo98RpSHVkatdvFIdJWIvVPvipgsVwutjltxkqhyU1zp_aZ6290Gr70iqbd9e4A6SOQDir544Wh94mVqaXhzvghfAnMXIBpikYbTph1FpRyRIkws3bZ_J9aDlQHBZhQzHt/s1600/20170224_061504.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg9MSkawQMtTlmo98RpSHVkatdvFIdJWIvVPvipgsVwutjltxkqhyU1zp_aZ6290Gr70iqbd9e4A6SOQDir544Wh94mVqaXhzvghfAnMXIBpikYbTph1FpRyRIkws3bZ_J9aDlQHBZhQzHt/s640/20170224_061504.jpg" width="480" /></a></div>
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So if I have an 8mm rod, and I have a clearance bore of 21/64" (closest common machine tool size, equal to 8.335mm), what's the best error I can theoretically achieve? More fun scratchwork below:</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqB2FoDDdrUEy4nOKF43j4DnXkJBpspT1WUQb9qtJwuZj2IIDXLLGbXLL2nyd1fELXdvoLCAf88tf7I8m8rIeq39PZcV1MgaVLIvscl4SiZTo3wDn5IMs2JgF5u-Nz_2-24ZRtnAjCEMjO/s1600/20170227_032653.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhqB2FoDDdrUEy4nOKF43j4DnXkJBpspT1WUQb9qtJwuZj2IIDXLLGbXLL2nyd1fELXdvoLCAf88tf7I8m8rIeq39PZcV1MgaVLIvscl4SiZTo3wDn5IMs2JgF5u-Nz_2-24ZRtnAjCEMjO/s640/20170227_032653.jpg" width="408" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">I can expect between 0.2° and 0.6° angular error assuming my carriage connection is actually rigid</td></tr>
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I needed to predict what sort of errors I would see from this device; for that I used another <a href="https://drive.google.com/file/d/0BzbyrnvMpW2hVWRrSlE2RFlHSlk/view?usp=sharing" target="_blank">Slocum spreadsheet.</a> This error apprortionment spreadsheet explores allowable errors for all the components in a machine based on total error the engineer wants to achieve and how precise the engineer can expect to get each individual part. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQ3Xpe-IHO542vQVjaRLPSCNtpC6wE2sCT9a8oTmM3A5fw5BmjG7dOlcRiA89qm08E7PnjS9gq6fjjhh_FANmKsoMIfLfDv3PqoE9o29JA-xMCFGhgJWuvb56asEit0zuss4kSq4DKIfJT/s1600/Capture.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="328" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhQ3Xpe-IHO542vQVjaRLPSCNtpC6wE2sCT9a8oTmM3A5fw5BmjG7dOlcRiA89qm08E7PnjS9gq6fjjhh_FANmKsoMIfLfDv3PqoE9o29JA-xMCFGhgJWuvb56asEit0zuss4kSq4DKIfJT/s640/Capture.JPG" width="640" /></a></div>
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The logic here is that I can easily acquire a decent actuator and build a decent structure through clever machining processes, but my sliding axis idea is going to rely on flawed delrin bearings and a really derpily-mounted and honestly not well-collimated laser "sensor". So I expect the most error to come from these items. The goal is to achieve 0.5mm precision (arbitrarily lofty goal) despite these items - for that to happen, my linear axis needs to have 0.33mm precision (angular precision 0.09deg) before considering load. (I'm moving things on this axis too slowly to care about thermal or process errors.) Welp, here goes.</div>
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I machined a block of delrin to create the four rail holders and the circular-bore carriage sliders. All the critical features of the rail holders (height, bore, and mounting bolt holes) were machined first, subsequently the block was bandsawed into four pieces. The slider pieces were also matched by machining everything before splitting, to improve relative precision of the components during assembly.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEieybMItLSJWfj1jgH0R4qJw71TC0MY7rg6_e7FhNimztdIjsq68ziLVnZi-dEE5YDqefaGLZ625yTZarxFsFOJSc_usGaxF1MxQYk4OKm4v1mFhqeSKA7q7b-AljoABk6oeZHEVZd31KbD/s1600/1.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="220" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEieybMItLSJWfj1jgH0R4qJw71TC0MY7rg6_e7FhNimztdIjsq68ziLVnZi-dEE5YDqefaGLZ625yTZarxFsFOJSc_usGaxF1MxQYk4OKm4v1mFhqeSKA7q7b-AljoABk6oeZHEVZd31KbD/s400/1.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Bottom faces of rail holders and slider (left) and top faces (right)</td></tr>
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Rail holders were bored with a 5/16" reamer to get a press-fit with the 8mm rod. Slider bore used a 11/32" reamer to get a slip fit. I ended up with a rail assembly that moved very smoothly under no load, and remained decent even when I pressed harder on it.<br />
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<iframe allowfullscreen="" frameborder="0" height="1138" mozallowfullscreen="" src="https://player.vimeo.com/video/205740566?title=0&portrait=0" webkitallowfullscreen="" width="640"></iframe><br />
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After assembling the more constrained rail, I measured the distance from the top of the rod to the slider - 1.42mm, and found a scrap piece of acrylic for the flat that reasonably matched that height. I then bolted my simple linear rail assembly to my lab's optical table, then attached a piece of sheet metal with VHB tape to test it.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSChpORaisBJ8Pqb1eObhddCNquKR50-upSOWq443KUOBnSkEjLffC6WMOhpUhTVYMCX5YEF_hT8FcCs5BiBuPz9Gz2QVgzbQKrnZPrky4Y6vy8ViYeKfoRzb1Dfea55uNdTPuJXsk9-le/s1600/20170223_180528.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSChpORaisBJ8Pqb1eObhddCNquKR50-upSOWq443KUOBnSkEjLffC6WMOhpUhTVYMCX5YEF_hT8FcCs5BiBuPz9Gz2QVgzbQKrnZPrky4Y6vy8ViYeKfoRzb1Dfea55uNdTPuJXsk9-le/s640/20170223_180528.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Simple Linear Axis with all the components</td></tr>
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Attaching components with tape isn't the most rigid way to make a machine, but I'll soon have to modify the carriage to add an actuator. I therefore decided to go with an attachment method that would be easy to remove, since I don't yet know what modifications I'll add to the final carriage.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrQyh2LLgL-36PgLV_ajLRDWsfLP844OnrZH2cbJRAKFwweLn0OWbjoOKHEeOXHMZMPTl7yzwteqrehTiQw5oDGt0z2LilcqnfoOxcB-zdzxhkS9f8MdhpvBliLNyzLmJEw2RbB4Xw0C9b/s1600/20170227_150937.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhrQyh2LLgL-36PgLV_ajLRDWsfLP844OnrZH2cbJRAKFwweLn0OWbjoOKHEeOXHMZMPTl7yzwteqrehTiQw5oDGt0z2LilcqnfoOxcB-zdzxhkS9f8MdhpvBliLNyzLmJEw2RbB4Xw0C9b/s640/20170227_150937.jpg" width="640" /></a></div>
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For testing, I taped a laser pointer to the carriage and pointed it at a cabinet 20ft (6.12m) away. My carriage is 75mm long and wide, so using Abbe error principles<br />
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$ \tan(\alpha) = \frac{\delta}{L} = \frac{g}{length of carriage} $ </div>
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and</div>
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$\alpha = \arctan(\frac{\delta}{L})$</div>
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where if I want my bearing error to be max 0.159mm (error apportionment), I want my angular error to be </div>
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$\frac{0.159mm \times gap}{l} = 0.02deg$</div>
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and therefore max $\delta$ = 2.167 mm (repeatability at same location)</div>
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and max $\delta$ = 3.36mm (moving the carriage the full length of the 214mm-long rail)</div>
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<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/205741209?title=0&portrait=0" webkitallowfullscreen="" width="640"></iframe><br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJhyC3wMy2fjxc5PZBrkp-bfmc-PZ8yHMuOb8Rzene3W_PKvcO8XeaZz6sxCzfmysLuvvCbrx2C9f63uiLewjI5oE_lMdmGJ3sosF6-3K7FidN6J6xIiN77IcsoP50ei2upMwsGxe584a5/s1600/20170223_182203.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJhyC3wMy2fjxc5PZBrkp-bfmc-PZ8yHMuOb8Rzene3W_PKvcO8XeaZz6sxCzfmysLuvvCbrx2C9f63uiLewjI5oE_lMdmGJ3sosF6-3K7FidN6J6xIiN77IcsoP50ei2upMwsGxe584a5/s400/20170223_182203.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Laser target. The white paper is so I can draw on it, and the black tape spot is for the camera's benefit.</td></tr>
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The following video is from me trying to square up the assembly relative to the target by eye. I slid the carriage back and forth along the length of the rail and rotated the linear axis until the laser stopped wobbling side to side. This calibration was very handwavey, so it's difficult to properly measure the precision of the device itself versus how angled the entire assembly was.<br />
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<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/205741728?title=0&portrait=0" webkitallowfullscreen="" width="640"></iframe><br />
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Once I rotated the optical table to a reasonable target-width (video below), I was ready to start properly measure my linear axis.<br />
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<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/205835566?title=0&portrait=0" webkitallowfullscreen="" width="640"></iframe><br />
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It's possible to back-calculate the estimated angle of the assembly relative to the target based on the overall drift of the laser across all the trials, but I definitely won't conduct enough trials to properly statistics-away this particular source of error. Instead, I'll probably find a better calibration method for the next iteration of this linear axis once the actuator is attached.<br />
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Anyway, during testing I discovered that my clearance-bore + flat method did indeed have noticeable side-side error and worse than I calculated - 9.81mm, which was a 0.09deg angular error for repeatability testing. A lot of this is due to my setup itself not being squared up - angular error at the front was only 0.04deg of error compared to 0.14deg at the rear.<br />
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Traveling from back to front multiple times, I accrued an overall angular error of 0.23degrees. Womp. My estimation from looking at repeatability of the fronts and backs is that 0.05deg of that was due to the the table itself.<br />
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Given these results, I tried squaring up the optical table a bit better and put a 500g weight on the carriage to look at effects of adding a load. This time, my fronts and backs had more similar displacements - both errors were 0.1deg. However, sliding back and forth got an error of 0.5deg - twice as much as when I tried this with minimal loading, and 5x what my error spreadsheet budgeted for.<br />
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I suppose this is what I get for attaching my carriage to my bearings using compliant foam tape and attaching my laser with ducttape, and I'll find out how much better I can get when I add an actuator and reattach everything with more thought.<br />
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However, the real experimental error matched up with my scratchwork predictions, despite having a bore gap 0.2mm larger than intended (using 11/32" reamer instead of a 21/64"). So probably I shouldn't expect to achieve anything significantly better even with an actuator.Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com1tag:blogger.com,1999:blog-5736103898080682832.post-53214230579204951962017-02-24T05:51:00.000-05:002017-02-27T10:07:17.851-05:00[2.70] Kinematic Coupling Round 2 (plus bonus annealing fun!)Last time I made a kinematic coupling for a Slocum class, the result was a <a href="http://www.avamakesthings.com/search/label/kc-pen">tiny magnetic coupling for a pen.</a> Well, time to make another 6-contact-point mechanism to constrain 6 degrees of freedom!<br />
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This time, I'm revisiting some material science fun - material properties of tempered and annealed aluminum. <a href="http://www.avamakesthings.com/2015/12/carabiners.html">Last time I did this</a>, I took 7075-O aluminum and heat treated it to approximately T6 temper. This time, I'm starting with a block of 6061-T6 and seeing how far I can anneal it.<br />
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I filled in two estimation spreadsheets for the kinematic coupling. This one assumes the grooved half is made of 6061-T6, and the second one assumes the grooved half was softened to T0. In both cases, I'm using pine spheres for the ball half.<br />
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For this spreadsheet, I assume that there's a 20N preload pressing the halves together but at an imperfect angle (5deg, so modeling a weight slightly cantilevered off the center). I also assume that I will be measuring Abbe-error at a distance of 10ft.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFRpmmPruquT_sx-yX16NNbfrqMmVcjx3NhuYsOOAQ_ewUP8bymhDCLzJ3e0I6e1tAxbQvL4p5pOccBbe6LmKx-K-b4w0u_wHE2rVl0UJtd0VbrYiTOe8uW3VWn9ViZY6gTP0SVnUQ9-Yv/s1600/kc1.JPG" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="596" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFRpmmPruquT_sx-yX16NNbfrqMmVcjx3NhuYsOOAQ_ewUP8bymhDCLzJ3e0I6e1tAxbQvL4p5pOccBbe6LmKx-K-b4w0u_wHE2rVl0UJtd0VbrYiTOe8uW3VWn9ViZY6gTP0SVnUQ9-Yv/s640/kc1.JPG" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">pine balls on 6061-T6 grooves<br />
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<tr><td class="tr-caption" style="text-align: center;">pine balls on 6061-O grooves</td></tr>
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<span style="font-size: small;">An interesting observation that emerges from these two spreadsheets is that annealing the aluminum is expected to yield no difference in kinematic coupling errors. Of course, that does make sense, since pine has a both a substantially lower yield strength and lower stiffness than even soft aluminum.</span></div>
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<span style="font-size: small;">I ran the spreadsheet again, using ball values for steel, and found that actually my problem is that the yield strength differences between T6 temper and T0 are too small to see much difference in error... and given that 6061 will have the same elastic modulus at any hardness, I'm not really sure what I expected in the first place. Anyway, moving on.</span></div>
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<span style="font-size: small;">This KC used a much less involved method of construction than the previous one. I grabbed leftover wooden drawer knobs and drilled 1/4"-diameter blind holes to accept steel dowel pins. Then, I drew a circle on some scrap aluminum (this isn't the one that will be baked) and marked and punched locations spaced 120 degrees apart. These punched spots were drilled through with a 1/4" bit and again with a 19/32" reamer (I couldn't find a 1/4" one!)</span></div>
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<span style="font-size: small;">19/32" holes ended up being too much of a slip fit, so I shimmed the dowels with some tape. </span></div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgl0Q3VUkKTZWSXf8UkIs3IpJ_LB0NuY5whjnlmZd_GVPZ6LMAA_Vn1-xh9SzyzrESt66aGAaIgjLJy-CRc6I25jz1tWed0oNgJpouqrtMDNO76jn9T0K03IReQzHyokELBccwgi6n3fIxZ/s1600/20170222_023017.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgl0Q3VUkKTZWSXf8UkIs3IpJ_LB0NuY5whjnlmZd_GVPZ6LMAA_Vn1-xh9SzyzrESt66aGAaIgjLJy-CRc6I25jz1tWed0oNgJpouqrtMDNO76jn9T0K03IReQzHyokELBccwgi6n3fIxZ/s640/20170222_023017.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Completed upper half of the KC</td></tr>
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The lower half of the coupling was made of a 1/4" chunk of 6061-T6, and used the same method as KinematicCouplingPen to form the grooves - indexing head for 120 deg rotation, preliminary cuts used a flat endmill followed by a chamfered bit (this one was a bit big for a countersink). I also drilled some 5/8" clearance holes for attachment to future tensile-tester fasteners.<br />
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Tensile testing ended up not happening, for reasons I'll get into later in the post :)<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCE9TYllgyAQtxUyzIURhIKKGC8xSaNBR8sPi1tFwT8tyxbKRowXW-iFK9yz8AhZetQiCMXabhv5p9WWo0QySCPCVmil2Ql_hvUblK5hfPrcPUJIgNx1NVnYEATAVkh8yt8X_k1K_rJUL6/s1600/20170223_113718.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhCE9TYllgyAQtxUyzIURhIKKGC8xSaNBR8sPi1tFwT8tyxbKRowXW-iFK9yz8AhZetQiCMXabhv5p9WWo0QySCPCVmil2Ql_hvUblK5hfPrcPUJIgNx1NVnYEATAVkh8yt8X_k1K_rJUL6/s640/20170223_113718.jpg" width="640" /></a></div>
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A note on machining - this go around I learned from my previous mistakes and locked the spindle when machining the grooves, instead using the much more rigid knee to control z-axis height.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj9LbdXqE8jcoAnaizUKQiN3EUJLXM_qB5DHbrtrRfyLKQDr4w16FkGIbWTSx3P-JMNg_1YVzrfngJ4EA5rDAT5zMEiJPAXpoGANfe914b8rkQGmk1ncBBIjWjYGC0ufpthy4mAXf1HBtWw/s1600/20170223_113823.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj9LbdXqE8jcoAnaizUKQiN3EUJLXM_qB5DHbrtrRfyLKQDr4w16FkGIbWTSx3P-JMNg_1YVzrfngJ4EA5rDAT5zMEiJPAXpoGANfe914b8rkQGmk1ncBBIjWjYGC0ufpthy4mAXf1HBtWw/s640/20170223_113823.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Completed kinematic coupling</td></tr>
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For testing, I relied on good old Abbe Error. Magnify your errors by projecting them really far away!<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEio5BTqB4ESKZyGdcAgeMbkznQa5ibwkAp5dJoVfQj4TFgyxuko_BAy0PC98RVTpMchLFztBDlquzwPB7hHoryMhnxWxJuyCUz9kADnHzu19q_RyHAYA0CSksBC8pBg0pR2IXgZ8EMLwJeu/s1600/abbe.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="182" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEio5BTqB4ESKZyGdcAgeMbkznQa5ibwkAp5dJoVfQj4TFgyxuko_BAy0PC98RVTpMchLFztBDlquzwPB7hHoryMhnxWxJuyCUz9kADnHzu19q_RyHAYA0CSksBC8pBg0pR2IXgZ8EMLwJeu/s320/abbe.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Abbe Error diagram from last time</td></tr>
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This KC has coupling radius "r" = 19.6mm, and my projection distance was 6.33m.<br />
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$d = \frac{rD} {L} = \frac{D} {322.96}$<br />
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$\frac{d}{D} = 3.096 \times 10^{-3} $</div>
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For these repeatability experiments, a projected deviation of 1mm indicates a coupling error of 3 microns. The experiment consisted of taking the KC top off and setting it down again, then marking the new location of the laser dot. I repeated this process 10 times.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7XkH4sYfho1PZVDyNoP7JrPUpSdmfZxypqbiqQ5KJvGgHmOGFVBuIyIZ4pEGsE-OPLWv0gAqFO6fE4SGqMCvH1cPrsiClZssUc6OVZR5X_urXgUc_zpThu6Hjwy1KPgT-g0b5YsmkSpai/s1600/20170223_145437.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7XkH4sYfho1PZVDyNoP7JrPUpSdmfZxypqbiqQ5KJvGgHmOGFVBuIyIZ4pEGsE-OPLWv0gAqFO6fE4SGqMCvH1cPrsiClZssUc6OVZR5X_urXgUc_zpThu6Hjwy1KPgT-g0b5YsmkSpai/s640/20170223_145437.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">KC was clamped to the table and a laser strapped to the upper half pointed at a paper on the wall</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmmQtHISWwxvFTA-iiIM2O1SgfrDAPac-ZowEdLAmF_PwcX0kKt4jzybLAvl8myMIr6BUxi5SE_Z0_-A8VUOit57IhAZCb74-sypgmgsNFeXDbIsZvawZcNpjpFmHJBhNFMmRgfT0pTnW3/s1600/20170224_040146.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmmQtHISWwxvFTA-iiIM2O1SgfrDAPac-ZowEdLAmF_PwcX0kKt4jzybLAvl8myMIr6BUxi5SE_Z0_-A8VUOit57IhAZCb74-sypgmgsNFeXDbIsZvawZcNpjpFmHJBhNFMmRgfT0pTnW3/s400/20170224_040146.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Actual piece of paper taped to the wall</td></tr>
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So how did I do? For the just-laser-pointer trial (self-weight provides a 2N preload), my max radius across the entire spread was 6.06mm. Maximum distance between consecutive trials was 8.64mm, and maximum distance from the origin (laser location before I started the repeatability test) was 12.3mm in the negative x direction.<br />
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I added some weight on the center of the KC and tried this experiment again with a 10N preload. Here, max spread radius was 5.50mm, max distance between consecutive trials was 8.48mm, and maximum distance from the origin happened from origin to location1 was 10.99mm<br />
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An interesting observation for both cases was that the origin itself - before I started messing around with the KC - is on the extreme edge of the spread (the origin location is marked with a sunburst pattern). I wonder whether the KC settles to a new favored position over time, versus when I quickly pick it up and set it down during the experiment.<br />
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Translating these results to errors in the coupling, I get this:<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKZRxM-7FTjugLmAjwst3A-XL4zCoRe_ZcYccm1JpiyImBnwU7_MVG1okILG7BBkYYB_oRenCyn1pLaogagphEJ71mIc5m-EEx7KL-mxCnSFmP1pIi7Yki3QIC06aBSEU509Ngcstk3diz/s1600/20170224_045241.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="281" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKZRxM-7FTjugLmAjwst3A-XL4zCoRe_ZcYccm1JpiyImBnwU7_MVG1okILG7BBkYYB_oRenCyn1pLaogagphEJ71mIc5m-EEx7KL-mxCnSFmP1pIi7Yki3QIC06aBSEU509Ngcstk3diz/s400/20170224_045241.jpg" width="400" /></a></div>
So this kinematic coupling is repeatable to approximately 15 microns. This happens to be 5x worse than the first one I made, but definitely took less than 1/5 the time to make.<br />
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Going back to the kinematic coupling spreadsheet and updating values to better reflect real life, I found that I should expect a displacement error of 12.7 microns (10N preload, where the added 8 N was assumed to be 1deg off center, because nothing's perfect). Pretty close to real life!<br />
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Alright alright, what happened to the material science part?<br />
Well, the internet suggests that a good way to soften 6061-T6 is to coat your piece with a layer of sharpie or bar soap and then torch it with an acetylene torch until the soot burns off. If you let it air cool, it should be somewhere between T3 and T0.<br />
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So I did that, then remembered I had an evening lab class in the metallurgy lab and the forge would still be hot when we finish with classwork! This was convenient, because the kinematic coupling piece is rather thick and torching it would only superficially soften the outer faces.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEilwi7Ua3gFoHsyQRnrVujKwRa4pd5muXK7o1xfUv8UKzeLgVvKyShBGKHi0xMPbrSeHJTaD94Jx_cZynhrXIKoirLrzxzZ12utDe6vHnHTxQxgRKAr-at5qGPc-qUYP7ndhAe99iEAcvlE/s1600/20170223_214806.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEilwi7Ua3gFoHsyQRnrVujKwRa4pd5muXK7o1xfUv8UKzeLgVvKyShBGKHi0xMPbrSeHJTaD94Jx_cZynhrXIKoirLrzxzZ12utDe6vHnHTxQxgRKAr-at5qGPc-qUYP7ndhAe99iEAcvlE/s640/20170223_214806.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Ooh, fire</td></tr>
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Unfortunately aluminum is less forgiving than copper and is more difficult to judge temperature by eye. It also happens to be that aluminum's forging temperature is only approx. 300 or so degF lower than its melting temperature... which is to say I spent too much time taking pictures and accidentally let my workpiece partially melt.<br />
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If you create deep grooves in a block of aluminum, the thinner bits heat up faster. Womp womp.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSW3LqODKLw_MWyHTYAcBK4r5_7g6vppqJnIJ1U7HojCia1aG4PwX9yhK30GNtgksO6h_AIAopi2QB1l20CKaAdzCktBEex4VP8d6fPLC3w59-TZabF2rx50XL8hy6jzaqV79xAVDfdFFY/s1600/20170223_215527.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgSW3LqODKLw_MWyHTYAcBK4r5_7g6vppqJnIJ1U7HojCia1aG4PwX9yhK30GNtgksO6h_AIAopi2QB1l20CKaAdzCktBEex4VP8d6fPLC3w59-TZabF2rx50XL8hy6jzaqV79xAVDfdFFY/s400/20170223_215527.jpg" width="300" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">#hubris #stoptakingpictures #startpayingattention</td></tr>
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So no stiffness testing between kinematic couplings this time. Luckily for me, I already did the assignment part.</div>
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What else can you do with a melty piece of aluminum? Nominally it should be T0, but in this state it's difficult to stick in an Instron. </div>
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I decided to try a very handwavey version of the Rockwell/Brinell hardness test methodologies to finish off this fun experience. I got a 18-oz ballpeen hammer and a metal punch, and struck each material with vaguely the same amount of force. Then I measured the depth of the indentation.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjb5cx0cwOSBjfh2PNi1wZoBqPaY6ZBJsZbubQNwn755Zsr99L5OIYQuKerZZWEXWh0laSYExHso_g3vgmjz9etHwGm6R1CoL6_slAJSYRB9QkMLl1x_oUYbqQHs_Qhyy5vrXl8NuE6O-6h/s1600/20170223_221121_2.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjb5cx0cwOSBjfh2PNi1wZoBqPaY6ZBJsZbubQNwn755Zsr99L5OIYQuKerZZWEXWh0laSYExHso_g3vgmjz9etHwGm6R1CoL6_slAJSYRB9QkMLl1x_oUYbqQHs_Qhyy5vrXl8NuE6O-6h/s640/20170223_221121_2.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Indent on melty-aluminum vs indent on your standard 6061-T6</td></tr>
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Melty-aluminum's punch was 1.2mm deep, and T6's punch was 0.25mm deep. If we assume (dubious) that I actually used the same amount of force striking each piece, melty-aluminum is 4 or 5 times softer than 6061-T6.<br />
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6061-O aluminum has a Brinell hardness of 30, compared to T6's hardness of 95. Between like-materials and this close together on the scale, we can assume the hardnesses and scale values to be linear and say 6061-O is 3 times softer than 6061-T6. So my melty-aluminum is either at T0 or softer. I'm leaning 'softer', since it... melted. I guess this doesn't actually count as "annealed".<br />
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(Kinematic Coupling spreadsheet says I wouldn't have noticed a significant difference in error, anyway. Hrmph)</div>
Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com1tag:blogger.com,1999:blog-5736103898080682832.post-31968597952188284582017-02-18T01:40:00.002-05:002017-02-18T01:46:20.194-05:002016 EC Clubhouse Construction<div class="separator" style="clear: both; text-align: center;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYW27f0IksOENG1QamaL5R8c2VkMDwRVj3p40pt6ULqWH5e8TJrRhYNo5v6rajNG7b09fT030sSQt1GzCgfdfg2_0mitT6MVC5DnkwE8RQG6YGo77l3sFHqRw9vdVy_EHTbfry2xWubnFc/s1600/20160829_135040.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYW27f0IksOENG1QamaL5R8c2VkMDwRVj3p40pt6ULqWH5e8TJrRhYNo5v6rajNG7b09fT030sSQt1GzCgfdfg2_0mitT6MVC5DnkwE8RQG6YGo77l3sFHqRw9vdVy_EHTbfry2xWubnFc/s640/20160829_135040.jpg" width="640" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgYW27f0IksOENG1QamaL5R8c2VkMDwRVj3p40pt6ULqWH5e8TJrRhYNo5v6rajNG7b09fT030sSQt1GzCgfdfg2_0mitT6MVC5DnkwE8RQG6YGo77l3sFHqRw9vdVy_EHTbfry2xWubnFc/s1600/20160829_135040.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><br />
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A short post about the wooden clubhouse my buddy Elena (left) and I lead for this year's EC REX! (<a href="https://webyun.wordpress.com/" target="_blank">Elena's</a> in charge; I was first mate :P )<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixpUb0FkuHQeK-JW8opscyYEfpNGDMY_-hYLb_GDBstts6nXBs4JrILEMqsKaldlfR_Hrc2Gsc-48ev-qqdxwWjHL0LQ9vcaZLpBv9iflaF-xODb_R0GFr60zcWPUUEuYT2vtq1DEM-C-H/s1600/20160823_130308.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEixpUb0FkuHQeK-JW8opscyYEfpNGDMY_-hYLb_GDBstts6nXBs4JrILEMqsKaldlfR_Hrc2Gsc-48ev-qqdxwWjHL0LQ9vcaZLpBv9iflaF-xODb_R0GFr60zcWPUUEuYT2vtq1DEM-C-H/s400/20160823_130308.jpg" width="400" /></a><br />
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Our goal was to make a small (smol!) hangout space alongside the larger East Campus Fort, to which we connected our structure with a <a href="http://www.avamakesthings.com/2016/10/2016-ec-rope-bridge-construction.html">rope bridge!</a></div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi1IRTZtJDNJCfH9xgZdItlRlu0KWDyzA4RQzrq8VDa5oKIhazn_jDqaqv42yxL-b5hVqLKSLUq1JmHshTiRqCpab_nDkKsPWdaTKZST8qQuC0KdPJDM7yKjI39BDQpVvhC6vpMIgG7W_nR/s1600/20160828_232656.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi1IRTZtJDNJCfH9xgZdItlRlu0KWDyzA4RQzrq8VDa5oKIhazn_jDqaqv42yxL-b5hVqLKSLUq1JmHshTiRqCpab_nDkKsPWdaTKZST8qQuC0KdPJDM7yKjI39BDQpVvhC6vpMIgG7W_nR/s640/20160828_232656.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">hangout space getting love during the East Side Party kickoff event</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJ7tnrewXPnWNLOuO5gR8FGPGEpyA3m4H8PU4ahnCWfiwYIQeCCq3SV916tSu-LAPUszvHFCIT4JhBS0IdCitYBryoDROkHO1CNTio5MibbC5bk6Xj-K2E6k2taogEb78vHrjBdsYQW2DS/s1600/20160829_135429.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJ7tnrewXPnWNLOuO5gR8FGPGEpyA3m4H8PU4ahnCWfiwYIQeCCq3SV916tSu-LAPUszvHFCIT4JhBS0IdCitYBryoDROkHO1CNTio5MibbC5bk6Xj-K2E6k2taogEb78vHrjBdsYQW2DS/s640/20160829_135429.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Our structure (left), attached to the larger fort project (right)</td></tr>
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We (along with fort team!) submitted design drawings and structural calculations to a PE and architecture firm to get their stamps for the temporary structure, and also got stamps from Cambridge Fire Dept.</div>
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Construction started with digging holes and adding gravel for foundation cinderblocks. We spent a long time setting up a level surface that compensated for the uneven dirt ground. Even more time was spent moving the foundation locations around to avoid all the tree roots!</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkEE2cb0fuHMH1VxSxlhHBCSOlj1czxnfiks4Zjlbdo3gGPxzYgfHWH-x1rm8Ylnp9cYggTWAyE_wHEsOrO0ojpbcdv2FJsdAAQEnazzfV6bqHw-6qLTJA2QVJ0E8uLBPkXG3LGowtibva/s1600/20160822_001531.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkEE2cb0fuHMH1VxSxlhHBCSOlj1czxnfiks4Zjlbdo3gGPxzYgfHWH-x1rm8Ylnp9cYggTWAyE_wHEsOrO0ojpbcdv2FJsdAAQEnazzfV6bqHw-6qLTJA2QVJ0E8uLBPkXG3LGowtibva/s640/20160822_001531.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">This took a night, then half another day to fix my mistakes</td></tr>
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Our two person team had a more leisurely pace than the 8 person team leading the Fort build. Both teams ended up finishing within 10 days, perfectly on time for the party!<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVdW9b4AOwPxds3T64IIsIqWw3DGKYjsbPRUDbeQE7xyetmRfKf05r66s5_DFULo-1FDC6u7_WU6nOciSE500O7-VqfM8kyxcvFQfiIU8OFeeROsNHdKyHmmxkrAxqCAmpY0pX3WsQ3ThY/s1600/20160823_004909.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVdW9b4AOwPxds3T64IIsIqWw3DGKYjsbPRUDbeQE7xyetmRfKf05r66s5_DFULo-1FDC6u7_WU6nOciSE500O7-VqfM8kyxcvFQfiIU8OFeeROsNHdKyHmmxkrAxqCAmpY0pX3WsQ3ThY/s640/20160823_004909.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Put up the central tower by Day 2</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjv7mJUgFysms2hQ9xo9q70lYv6DkJGQ0R9CrAolzFGKvSQzmrg_nojlnNhMV8c95rKLGyr7zYbgQZhmFUSDPGCQE2nU0VPr3jIAxpVWRwps1bINqxYGAK-GCN6GF4wZ3meOdpkDJ7a-sAo/s1600/20160824_175724.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjv7mJUgFysms2hQ9xo9q70lYv6DkJGQ0R9CrAolzFGKvSQzmrg_nojlnNhMV8c95rKLGyr7zYbgQZhmFUSDPGCQE2nU0VPr3jIAxpVWRwps1bINqxYGAK-GCN6GF4wZ3meOdpkDJ7a-sAo/s640/20160824_175724.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Three towers up!</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirI-RxAmV_EpwLWIC7SlFZ6Lrd7kJnsa6_3n8lU8LlrE2ooM-zJraqaAIdlco52hXl8FO69x1Nxds8eK7UfrGbAd4AxMQFCKO8cFqOkT5MaW5yLJtTON9lc-U1qwp4NvRJqfNaAw0qVKUG/s1600/image-20160824_214707.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEirI-RxAmV_EpwLWIC7SlFZ6Lrd7kJnsa6_3n8lU8LlrE2ooM-zJraqaAIdlco52hXl8FO69x1Nxds8eK7UfrGbAd4AxMQFCKO8cFqOkT5MaW5yLJtTON9lc-U1qwp4NvRJqfNaAw0qVKUG/s640/image-20160824_214707.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">By the end of Day 3 we had floors on the entire second storey.</td></tr>
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<tr><td class="tr-caption" style="text-align: center;">Starting on the tower again</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjD0FM_zwz9saQcLpHX_Vu6t1a-GbzsA-foMIhbUOJFp8iZ0Z9ccRbvI23MV0Ql2xoiA6TIh4WPwuY1ORjCunH0zg_HMkhyAKPbqRmSndI48W6N3Qu_RYLMojPdxaOzozLGEBNxEs50ZnM/s1600/20160903_115921.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjD0FM_zwz9saQcLpHX_Vu6t1a-GbzsA-foMIhbUOJFp8iZ0Z9ccRbvI23MV0Ql2xoiA6TIh4WPwuY1ORjCunH0zg_HMkhyAKPbqRmSndI48W6N3Qu_RYLMojPdxaOzozLGEBNxEs50ZnM/s640/20160903_115921.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Adding joists to the third floor.</td></tr>
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Once the overall structure was completed, Elena and I split up the rest of the tasks. Elena added in the railings and I started working on the rope ladder.<br />
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The rope ladder was our access point for the second floor, and was attached to the spandrel via eyebolts and to the ground via anchors. The anchors get driven 2 feet into the ground, then a load pulling on the steel cable wedges the anchors at an angle.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWU8vYX5pJE_xzmyNCU3cpwKKcqc1Sk1XPQt5IP6A8AiIPuyPFIC1YB8z5slQUZlvWC00qOHM3v-6WbMIBw0-OiRC1AOkJyHjRV68oYNrnClO8zsZvChtTki3GZuEM-ixK7CI92Vm1MNqA/s1600/image-20160827_142245.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWU8vYX5pJE_xzmyNCU3cpwKKcqc1Sk1XPQt5IP6A8AiIPuyPFIC1YB8z5slQUZlvWC00qOHM3v-6WbMIBw0-OiRC1AOkJyHjRV68oYNrnClO8zsZvChtTki3GZuEM-ixK7CI92Vm1MNqA/s640/image-20160827_142245.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Had to soak the ground to drive in ground anchors. These will be impossible to move.</td></tr>
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Most of my time was spent working on rope ladders and <a href="http://www.avamakesthings.com/2016/10/2016-ec-rope-bridge-construction.html">bridges</a>, and by the time I finished Elena had completed the rest of the clubhouse around me! The REX Chairs ordered a bunch of beanbags to make the hangout space cozier.</div>
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<tr><td style="text-align: center;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhATWkUvfRY0Xdzsj8O5c2q290ReQ58OiNqA-mfkgBjIDfdZ6Dhm15Xv1Bp4ItJx_RqAJW1fH6uaKrZOsvMxGUYXJZOPxLCFq_3AdSmyK-HsE6mOyKfSPSAA9NT8fKdP1SwD-w0UiKtXCKV/s640/20160829_134912.jpg" style="margin-left: auto; margin-right: auto;" width="640" /></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Note how we don't actually touch the tree. Trees in the courtyard are historic and we aren't allowed to hurt them!</td></tr>
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Maya was super excellent and knotted the rope ladder together, then tensioned it up. In planning phase I miscalculated how angled I wanted the rope ladder to be; I set the horizontal distance too far and the structure ended up being more saggy ideal. We helped make climbing easier by adding a wooden handhold/step, as well as reinforcing the OSB shear wall to accommodate people stepping on it. Up above on the second floor, we screwed in 2x4 hand-holds onto the floor to help people exit/enter the ladder.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimGWlQjDyG8b0Gg0aZ_C0CKyxILxMnWrVafNy9U9OcEMF2mLAcbcK5S7UJG2rjBiFxiAkhSMArJ72swEUC_jDY7AGmzoARnfW6uvEgAH9foI_kb3ZGBIUnxWbpD4uuAX7VN-7ZT_VUtBKD/s1600/20160829_135440.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimGWlQjDyG8b0Gg0aZ_C0CKyxILxMnWrVafNy9U9OcEMF2mLAcbcK5S7UJG2rjBiFxiAkhSMArJ72swEUC_jDY7AGmzoARnfW6uvEgAH9foI_kb3ZGBIUnxWbpD4uuAX7VN-7ZT_VUtBKD/s640/20160829_135440.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Art thanking our sponsors! East Campus and Clubhouse team are really happy we had such talented artists joining in</td></tr>
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Elena and I saw the sponsor art, got super excited, and immediately asked the REX chairs if they would ask people to make the rest of our shear walls pretty. The chairs sent out a call for artists to the 100+ mailing list of people helping with construction and REX events, and we got the most beautiful art decorating the OSB shear walls.<br />
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<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.comtag:blogger.com,1999:blog-5736103898080682832.post-50083147072616368492017-02-15T22:28:00.001-05:002017-02-16T03:23:48.145-05:00[2.70] Planar Exact-Constraint Exploration (plus bonus photoelasticity!)I was watching this youtube video about visualizing stress concentrations in acrylic using polarized light, and I thought it would be really neat if I could see how each of the constraints hold load in my exact constraint (EC) system.<br />
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What's going on in the video is a technique called photoelasticity, which is helpful for visualizing stress strain analysis for complicated geometry or loading conditions (or both!). Acrylic (and many other transparent materials) exhibit birefringence under stress, where the magnitude of the refractive indices throughout the material correspond to the magnitude of stresses at each point.<br />
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I hope to play with two items of MechE science with this EC - I can experiment with different constraint configurations by moving the dowels around, and I can observe the relative stresses on the dowels imposed by the load.<br />
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Exact constraint is the principle of only using as many constraints as there are available degrees of freedom. An object on a plane has three - two translations and one rotation - so the goal here is to achieve only three points of contact. Using exact constraint lets you avoid having your parts bind or behave in unpredictable ways.<br />
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My EC is the simplest version you could make - pins in holes. I wanted something configurable, so I set up a acrylic-lasercut grid of 5/16" holes to accommodate wooden dowels. The smaller holes on each side are for mounting the EC to a standard hacksaw frame.<br />
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<tr><td class="tr-caption" style="text-align: center;">Pins in holes</td></tr>
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The standard hacksaw makes a convenient experimental fixture for applying tension; I just have to attach my EC to the blade. The dullest hacksaw blade on the workbench got shortened (cannibalized with a hacksaw!) and two additional holes.</div>
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<tr><td class="tr-caption" style="text-align: center;">Saw blade taped onto table with VHB</td></tr>
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The hacksaw then got shoved into a plastic u-channel thing I had in my room and the entire assembly was clamped to my desk. I elevated the assembly on a pair of V-blocks to get a better angle from my laptop screen.<br />
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I borrowed a camera polarizing filter from a friend, and now we're ready for some science!<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjoJwYG9YPX5ej4JMnbuq1LB-s711dRYfycEtPyy2cFY4TYihwAEr_84-e1U0BHYiVpmSo5xXmdU5m58Y8MDrhsAFJCMU4iqxZpowXZfFFs2K7P2Q4J3mH_4xTkCVM9LT7zHrEpFlJ3q7v1/s1600/20170215_193303.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjoJwYG9YPX5ej4JMnbuq1LB-s711dRYfycEtPyy2cFY4TYihwAEr_84-e1U0BHYiVpmSo5xXmdU5m58Y8MDrhsAFJCMU4iqxZpowXZfFFs2K7P2Q4J3mH_4xTkCVM9LT7zHrEpFlJ3q7v1/s640/20170215_193303.jpg" width="640" /></a></div>
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<tr><td style="text-align: center;"><a href="https://media.giphy.com/media/hNY7d5R2c6naE/giphy.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="360" src="https://media.giphy.com/media/hNY7d5R2c6naE/giphy.gif" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Spinning the polarizing filters makes patterns visible!</td></tr>
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I tensioned up the hacksaw and observed the birefringence patterns of just the grid plate. There are a few cool things here:</div>
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<ul>
<li>You can immediately tell which screw got clamped down with a lock nut vs. the regular hex nut</li>
<li>There are some nicks at the bottom of the acrylic plate that I didn't notice before</li>
<li>You can see all the defects in the lasercut holes. Maybe there was some uneven melting?</li>
<li>Since the regularly-spaced holes break up the neutral axis, you see some stress fields deflecting diagonally. At the same time, you get a cross-shaped pattern of dark spots between each hole which was not what I expected (I thought you'd get something more like magnetic-field-line-shapes)</li>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFE8lADeQJfKTYpnS0skAjGqD7ZC6xUnTq95vX_22mAHC4M4ZCI4RuvqWowc_IuPF7lT5ZAxWKUTdM6clOf_JdD_UkN9pyTHKKU6xoDOjuPTlvEfUnnlhtkn5vpRqFiShDcK-QPhnAS7fC/s1600/20170215_192237.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgFE8lADeQJfKTYpnS0skAjGqD7ZC6xUnTq95vX_22mAHC4M4ZCI4RuvqWowc_IuPF7lT5ZAxWKUTdM6clOf_JdD_UkN9pyTHKKU6xoDOjuPTlvEfUnnlhtkn5vpRqFiShDcK-QPhnAS7fC/s640/20170215_192237.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Woah</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJTX68p6JKyXnY52TgLEzbWB5z4QR38jtPXCBbUKo0JQb5F7vD9berjwiYpC5Vazxoj6-swUF1k-ltPkn2CnE1Nr7yAgVvTBeqbGSa_qcCio5Tckr8y93_VHEmetNz8pCtDcKHQIi-aGPc/s1600/ecplatedxf1.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhJTX68p6JKyXnY52TgLEzbWB5z4QR38jtPXCBbUKo0JQb5F7vD9berjwiYpC5Vazxoj6-swUF1k-ltPkn2CnE1Nr7yAgVvTBeqbGSa_qcCio5Tckr8y93_VHEmetNz8pCtDcKHQIi-aGPc/s400/ecplatedxf1.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">How I thought stress patterns would go</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjU8R7-nJ1LYnT5jnKQd0eekJjLFsb3sdeFp-wF27a9gMQOIKhH60dPKEVhh9gSFIf08OugNOtpX7efI0m1oxYYZm-Mr_iK1D20DAlfgGwsuoVhjcxxL84_glRoXGZ9BE47bgD-pk6tYjL8/s1600/ecplatedxf2.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjU8R7-nJ1LYnT5jnKQd0eekJjLFsb3sdeFp-wF27a9gMQOIKhH60dPKEVhh9gSFIf08OugNOtpX7efI0m1oxYYZm-Mr_iK1D20DAlfgGwsuoVhjcxxL84_glRoXGZ9BE47bgD-pk6tYjL8/s400/ecplatedxf2.png" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">How stress patterns appear to go</td></tr>
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I'll probably revisit this idea after I read up on math :P<br />
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Back to the actual assignment - Exact constraint! Here it holds a pair of pliers with one pin on the bottom and two above, where it takes advantage of moment to hold things in place.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMRP1FOHEiHubh54WssgBtuRpGon1ythqIQvtpejb9zBBDd-YhyphenhyphenLCGcbdUj0XIl3MIITOS0ch1ufDlIWClUHqRYlUEsuqrbzTCQ0vaYJ75wtvYlDCMH9laKGwP_DDv-T2-qftLewp858Vj/s1600/20170215_194253.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMRP1FOHEiHubh54WssgBtuRpGon1ythqIQvtpejb9zBBDd-YhyphenhyphenLCGcbdUj0XIl3MIITOS0ch1ufDlIWClUHqRYlUEsuqrbzTCQ0vaYJ75wtvYlDCMH9laKGwP_DDv-T2-qftLewp858Vj/s640/20170215_194253.jpg" width="640" /></a></div>
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It supports this random item from my desk using two pins on the bottom and one constraining the side.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-UgKSrvdayZisb02vLk4i62ew3Mo92Ckf_5PAGWea-WOM0PE4ch854SXYmb7dyB8AU-4yNJpOv_GYo3cdz4ZlBCRf_bTx1pA8D05nu14CO9CR0TaM4I9ykjOS0KM9Ync36hwIdT5Km2Ww/s1600/20170215_190040.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh-UgKSrvdayZisb02vLk4i62ew3Mo92Ckf_5PAGWea-WOM0PE4ch854SXYmb7dyB8AU-4yNJpOv_GYo3cdz4ZlBCRf_bTx1pA8D05nu14CO9CR0TaM4I9ykjOS0KM9Ync36hwIdT5Km2Ww/s640/20170215_190040.jpg" width="640" /></a></div>
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Cool birefringence patterns when I put force on the bottom two pins holding random-item-from-desk.<br />
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<a href="https://media.giphy.com/media/EdsWYrn6rfAnC/giphy.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="https://media.giphy.com/media/EdsWYrn6rfAnC/giphy.gif" width="640" /></a></div>
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Also cool patterns happen when I exert a moment on the entire plate!</div>
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<a href="https://media.giphy.com/media/oRXphUF8W9c52/giphy.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="360" src="https://media.giphy.com/media/oRXphUF8W9c52/giphy.gif" width="640" /></a></div>
<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com2tag:blogger.com,1999:blog-5736103898080682832.post-26496334327205796572017-02-13T18:45:00.001-05:002017-10-22T21:44:36.522-04:00Prosthesis-Climbing-Shoe Prototypes<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQOBo44L_JKEif5xEoUuUaXHthEsh90VppunsunfYwV8T7V4kc5RPRkIVJlc5pKrTftgHBdVLaka6LOWhGW_9dmjtoF-fIBKTbIRuWS5fPUU5tLyxgQEyoZJIjQ7noVGGjMtClN_llAIf5/s1600/Capture.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="340" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgQOBo44L_JKEif5xEoUuUaXHthEsh90VppunsunfYwV8T7V4kc5RPRkIVJlc5pKrTftgHBdVLaka6LOWhGW_9dmjtoF-fIBKTbIRuWS5fPUU5tLyxgQEyoZJIjQ7noVGGjMtClN_llAIf5/s640/Capture.JPG" width="640" /></a></div>
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Background:</h3>
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My January-independent-term project was making proof-of-concept climbing and hiking shoe attachments for prostheses! Specifically, one of those below-knee carbon fiber prostheses for athletes.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRksACB2q4IyRsDUOyEuqSrnTkG0Ofy1DT9XTRBvA3MKRzO2YRGuMz87yh3cjjD6EP3Ue-amsLfnZ6P9vOag4O463ADoXFe0HuR-Qr6JSMfC7zeGQpgWcRecOxAwizpDUVM-pH9-PXkIdD/s1600/image-20170203_232456.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRksACB2q4IyRsDUOyEuqSrnTkG0Ofy1DT9XTRBvA3MKRzO2YRGuMz87yh3cjjD6EP3Ue-amsLfnZ6P9vOag4O463ADoXFe0HuR-Qr6JSMfC7zeGQpgWcRecOxAwizpDUVM-pH9-PXkIdD/s320/image-20170203_232456.jpg" width="180" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">This kind of foot</td></tr>
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They're typically used for running, generally on a track. Most attempts to make these suitable for other athletic activities (hiking, climbing, etc) require permanent modifications to the leg or try to fit the foot to standard shoes. Ossur + Nike have a removable-sole one that works as a high-performance trail runner, but theirs requires a proprietary fastening system that wouldn't work on generic blade-feet.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSGCUs_TpSRkiFCwcc2NRdj1F97wc6Dvb2ETCSQva_aLpn5Vc6wXXQ4QCMgvcqCMA1WP4bNDznEevXM53ROjY7K_CBT_8HF1Xx8KQHaLiYpisT32kDx-6Q_Gopjn_p9gq5OwR7Lu2d2Chv/s1600/Capture1.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiSGCUs_TpSRkiFCwcc2NRdj1F97wc6Dvb2ETCSQva_aLpn5Vc6wXXQ4QCMgvcqCMA1WP4bNDznEevXM53ROjY7K_CBT_8HF1Xx8KQHaLiYpisT32kDx-6Q_Gopjn_p9gq5OwR7Lu2d2Chv/s320/Capture1.JPG" width="288" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><a href="https://www.ossur.com/prosthetic-solutions/products/sport-solutions/flex-run">Ossur's Flex-Run w/ Nike Sole</a></td></tr>
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Plenty of climbing-specific prostheses exist on the market. These range from <a href="http://www.trsprosthetics.com/product/climbing/">ones mimicking biological footprints</a> to <a href="http://www.mountainoandp.com/adkfoot/">highly-specialized points</a>. There are also a bunch of proof-of-concept ones: <a href="http://www.dailymail.co.uk/news/article-2181527/Who-Says-I-Cant-climber-scales-200ft-cliff-despite-having-legs--false-limbs-falling-halfway-up.html">climbers' own custom creations</a> and <a href="http://www.jamesdysonaward.org/projects/klippa-prosthetic-leg-rock-climbers/">student research projects</a> (mine's going to be another silly student research project.)</div>
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This project started from a conversation with Hugh Herr that went something along these lines: Say I wanted to go climbing. Right now I have to carry a set of normal walking legs, then I need a set for the approach - that's a good hike, and then I have climbing legs. I'd also have to carry all the wrenches and stuff to remove them. That's a lot of weight and used-up space.</div>
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A set of attachments that could all fit on the same prosthesis - like shoes - would be more compact (and also probably cheaper!) Even more ideal would be a set of attachments that required minimal tools to put on and remove.</div>
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Like the <a href="http://www.avamakesthings.com/search/label/motorized%20ripstik" target="_blank">ripstik project</a>, this one also got funding by ProjX (The branch of TechX student group that funds projects) to get started over January, demoed in early February, and will probably become another ongoing, intermittently-worked-on item in my life.</div>
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<h3 style="clear: both; text-align: left;">
Design:</h3>
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I wanted to see how well a sock-like climbing attachment would perform using high-friction sticky rubber. Ideally, this attachment would be easy to put on and take off when in an unloaded state but stay put when loaded and in use. The attachment should also have a mechanism preventing it from flying out when the leg is swinging freely.<br />
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The project originally considered three concepts: a hiking "approach" shoe, a specialized climbing shoe, and ice crampons. In the interest of time, I decided to focus on the climbing/hiking shoes and cut out the crampon-shoe for this January project. A working friction-mechanism on a climbing shoe is highly likely to work well on the other attachments. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0L1NIzeT1j9I6tBlCZ39Qu2ZGNBH3h0LAkxP13QktuhBJL57k9OE9ILt9yOKd7mHW6iLCfUH7ZnRYzio4p-MsPLE3_7wxUSJD9tcwjx0T2U_dEQaLf4qrHD03xMHg7yRHhnGzU3gzuxgP/s1600/20170209_141546.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj0L1NIzeT1j9I6tBlCZ39Qu2ZGNBH3h0LAkxP13QktuhBJL57k9OE9ILt9yOKd7mHW6iLCfUH7ZnRYzio4p-MsPLE3_7wxUSJD9tcwjx0T2U_dEQaLf4qrHD03xMHg7yRHhnGzU3gzuxgP/s640/20170209_141546.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">First set of drawings pitching the project to funding</td></tr>
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I briefly entertained the idea of using cams clamps or other locking mechanisms as my fallback for keeping the shoes attached to a swinging foot, but I wanted to see how the attachments performed without these additional features first.<br />
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Instead, I decided to try including an elastic rubber strap that hooks onto the back of the prosthesis and applies elastic pressure (while hopefully maintaining enough static friction to not just roll down the slope.) This elastic strap ended up being entirely useless, but now I know.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7r0pHRacXefpUCs61zrWZtmsJbaFJuK6tffnMKzuN5fOq8u8hq742JSjVP2nqBP0RLNYKnyjdZaWvbbDOxWB50gbgvXHwJzx8LIVYcE7lq5gGHP7x_JYwzcesmiEitUS21ND0c0DBIQ5I/s1600/20170209_141626.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7r0pHRacXefpUCs61zrWZtmsJbaFJuK6tffnMKzuN5fOq8u8hq742JSjVP2nqBP0RLNYKnyjdZaWvbbDOxWB50gbgvXHwJzx8LIVYcE7lq5gGHP7x_JYwzcesmiEitUS21ND0c0DBIQ5I/s400/20170209_141626.jpg" width="322" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Considering how retaining strap would work</td></tr>
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<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5Mq_01xBSvmFBEgHOvZHN71N-aQZokemelyRnUnbrqIe6btMV2MCQ3eZinC846TN0U4T7nMbf6S-jc-F5qqnoITHygjpw90NI94rJs7sWfzic88nR80zRrIqJf_sN9HNVN9IlXh7Zku8k/s1600/20170209_141648.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="334" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5Mq_01xBSvmFBEgHOvZHN71N-aQZokemelyRnUnbrqIe6btMV2MCQ3eZinC846TN0U4T7nMbf6S-jc-F5qqnoITHygjpw90NI94rJs7sWfzic88nR80zRrIqJf_sN9HNVN9IlXh7Zku8k/s640/20170209_141648.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Deciding what types of rubber to use where</td></tr>
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I bought a durometer sample rubber pack to figure out what stiffnesses of polyurethane rubbers corresponded to the properties I wanted. My super-sticky, highly compliant rubber "sock" was made from 70Oo polyurethane, reinforced by strips of 40A rubber. I also bought 60A rubber hoping to use it as an abrasion-resistant toecap, but that rubber ended up not working well at all with my adhesives.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCf56_ItfDYAf6moAKUA4VviwLoG8y-_cmadsPKqH6ZDMJQJmFM20TEcW6VHTNqqIV8eFrYvsL0qbbVayNyrGhxbmNQTLw9zdduo68_qqrZHDj8aBrbxjaA-MbdGNX62xMmyVxG3qiSmJR/s1600/20170209_141643.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="232" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCf56_ItfDYAf6moAKUA4VviwLoG8y-_cmadsPKqH6ZDMJQJmFM20TEcW6VHTNqqIV8eFrYvsL0qbbVayNyrGhxbmNQTLw9zdduo68_qqrZHDj8aBrbxjaA-MbdGNX62xMmyVxG3qiSmJR/s640/20170209_141643.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Concept design on a climbing foot with rubber types chosen</td></tr>
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Climbing rubber came from Five-Ten's stealth-C4 resole kits. I had originally contacted resellers of all sorts of climbing shoe brands asking for rubber sheet samples - turns out my concept of a "small sheet" was 1 sq. ft. and theirs was 40 sq. ft.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_BJmxP8FM_VL0RPRuD2tHkw00dsKUF-fBrga4eDGPoiZQ8b-zSJR8S6WhGNdfHVzXsdRZsZ0Y2IbxAVtKAEhQ2KL4raUBPn4S-vpH0Job4MpBjHCH3njSH9g4TiVZLC4QdprKqPN_zTsf/s1600/image-20170118_172705.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_BJmxP8FM_VL0RPRuD2tHkw00dsKUF-fBrga4eDGPoiZQ8b-zSJR8S6WhGNdfHVzXsdRZsZ0Y2IbxAVtKAEhQ2KL4raUBPn4S-vpH0Job4MpBjHCH3njSH9g4TiVZLC4QdprKqPN_zTsf/s320/image-20170118_172705.jpg" width="180" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">This is plenty.</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi3PCa37yXQbH-tI0LMbDzSf_Bnn1n3BNdWOfoiDPcJqR5fQwGHyjZv9DV21i_SfK_rizb3Y1_wWpbpEQq4Vch0lSoJhz8npDZlYWp-Ds_4JpRfz64A3dooQbRp-Z08OxJ6jevWcL5sv1_d/s1600/20170209_141704.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi3PCa37yXQbH-tI0LMbDzSf_Bnn1n3BNdWOfoiDPcJqR5fQwGHyjZv9DV21i_SfK_rizb3Y1_wWpbpEQq4Vch0lSoJhz8npDZlYWp-Ds_4JpRfz64A3dooQbRp-Z08OxJ6jevWcL5sv1_d/s640/20170209_141704.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Design sketches after playing with rubber samples</td></tr>
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I had the pleasure of talking to Laura Shumaker about her experiences at <a href="https://www.sftclimbing.com/" target="_blank">SFT Climbing</a> (she maintains <a href="https://www.sftclimbing.com/blogs/design" target="_blank">the most amazing design blog for SFT</a>, which also has some manufacturing and testing insights.) She helped confirm my assumptions about the material properties of the special-climbing rubber, and suggested some adhesive brands that worked nicely with both fabrics and rubbers.<br />
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<h3>
Construction:</h3>
<div>
(In which Ava takes her non-existent knowledge of clothing design or footwear fabrication and tries to make shoes)</div>
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<div>
For this iteration, everything was just hand cut. Figuring out lasercutter parameters for the various rubber types is a job for next time.<br />
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I thought that if I punched the corners first, the rubber would be less inclined to tear. This probably would have worked better had I used a larger-diameter punch, or at least a hollow punch meant for soft things and not metals. The rubber tore at the corners anyway, but I fixed that by sanding larger-diameter inside corners with a dremel.</div>
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I went ahead and made two shoe soles using the same sock pattern. For the hiking shoe, I did a bit of reading about how real people design tread patterns to improve multi-directional grip and let water/mud optimally escape to aid traction, then promptly ignored all of that and just cut out rectangles. This rubber was a stiff but still high-traction mystery sheet. </div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvPLIgiVJKkV-cgYOYsm4J8xIbrMEq760QraMGrIacsdEzZJoYRgYgKHwECVg_3QW7pUlqiUCY2xjnA7p2W2hzDkvk1NNx81Z6zsAjhc68XKbFt6DjifxgEQM9JN_mXVXxhyphenhyphenCvNBGcOyDS/s1600/img04.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhvPLIgiVJKkV-cgYOYsm4J8xIbrMEq760QraMGrIacsdEzZJoYRgYgKHwECVg_3QW7pUlqiUCY2xjnA7p2W2hzDkvk1NNx81Z6zsAjhc68XKbFt6DjifxgEQM9JN_mXVXxhyphenhyphenCvNBGcOyDS/s400/img04.jpg" width="400" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhHKCnHK7FajwKsKffP007EY6JMh0oCL4rVixmsuaLHjmGjkECNYYbA5ZsNhF4fOJEXkMImiw8pcWZy9SvzI1aqFmaucQ25JB_3UeJ_NnT6p0HDaAZY2PeMjK4aiV-Ew2N0SgC6qXKSXM3y/s1600/img03.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhHKCnHK7FajwKsKffP007EY6JMh0oCL4rVixmsuaLHjmGjkECNYYbA5ZsNhF4fOJEXkMImiw8pcWZy9SvzI1aqFmaucQ25JB_3UeJ_NnT6p0HDaAZY2PeMjK4aiV-Ew2N0SgC6qXKSXM3y/s320/img03.jpg" width="180" /></a></div>
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Mystery-rubber sole + treads got glued to the flat sock-rubber pattern. I got a frying pan and random billets to use as a clamp.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4t5vrJ1jOvQFety_wIaizRNF993eeF3eyR3NRyoRC6eGcEQj4Lmr5lIsX_h8X65vGWruxSeVf7C3Z9TzRSd4d_tReVTir7h9-Q9LI-dW2YpFzNEkc3BlfhqkR-ik5_iIRTCEYAsOVEa_K/s1600/image-20170202_221858.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh4t5vrJ1jOvQFety_wIaizRNF993eeF3eyR3NRyoRC6eGcEQj4Lmr5lIsX_h8X65vGWruxSeVf7C3Z9TzRSd4d_tReVTir7h9-Q9LI-dW2YpFzNEkc3BlfhqkR-ik5_iIRTCEYAsOVEa_K/s400/image-20170202_221858.jpg" width="225" /></a></div>
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Grinding, folding, and gluing the rubber sock pattern was a long exercise in trial and error. I quickly realized I should've built up the sock using several layers of thinner rubber instead of attempting to form it from a single piece. Trying to curl the rubber into a toebox and not have the joins peel apart the adhesive did not work super well, even after reinforcement with fabric (random pants fabric I had) and grinding channels along the bend edges. </div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhy554Op4eGserhbyQvdqTHI5iE8rKGNV5Z9aq9ubB12w9lhRDBjQ_xjvdoKSYLxvYNo-nGVnVlY2qEEPsy7hfHhS3Cq7E8cEflYZwvBf8I_mwMuVIN13UUeg7hbRuEa_yu9t7o7taTTwPe/s1600/20170202_032006.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="360" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhy554Op4eGserhbyQvdqTHI5iE8rKGNV5Z9aq9ubB12w9lhRDBjQ_xjvdoKSYLxvYNo-nGVnVlY2qEEPsy7hfHhS3Cq7E8cEflYZwvBf8I_mwMuVIN13UUeg7hbRuEa_yu9t7o7taTTwPe/s640/20170202_032006.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Marking out where I wanted the shoe upper to end and the approximate location of retaining strap</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWzG_htBHHZZLT3LVrPAaBpRiZeRrm6f9Z9RnNpM5jDrgE9EnIPF2aGP8iABI2mM-GbnYHwG79Cv0eoIV8rfzzQFkHITyMdYzCId27voNRYjY0u_saCpPWH2QOFW57ZKF9uNJNHX658Hf5/s1600/image-20170203_233118.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="358" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWzG_htBHHZZLT3LVrPAaBpRiZeRrm6f9Z9RnNpM5jDrgE9EnIPF2aGP8iABI2mM-GbnYHwG79Cv0eoIV8rfzzQFkHITyMdYzCId27voNRYjY0u_saCpPWH2QOFW57ZKF9uNJNHX658Hf5/s640/image-20170203_233118.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Rubber dust got everywhere. Everywhere.</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiL46CbCGNrayqOHe8zuj9AnefHFfnUE_CoNdJgbdTOnr2Xn7yyzxG6GU1PGwJryeG8g7Xj0nORZl6TLJ_BEFB7FTdr0GAPpdCbRMr1wZlaiJ-k06r2bhWjK-kcHLswO7nT6437KNwE4Pph/s1600/20170202_220142.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="358" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiL46CbCGNrayqOHe8zuj9AnefHFfnUE_CoNdJgbdTOnr2Xn7yyzxG6GU1PGwJryeG8g7Xj0nORZl6TLJ_BEFB7FTdr0GAPpdCbRMr1wZlaiJ-k06r2bhWjK-kcHLswO7nT6437KNwE4Pph/s640/20170202_220142.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Bending and gluing toebox</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhd252PH_QXK2mpXpNL0ZskGOo8U5I6tYuTkskmJnCdCEx9-8N6fIdGLurAB_-pDvMYIWWQWYWjyXZ6OHHfHf-4L16XoGo_45-_NCcs9LBAtVHkZluaO3w3e1bjvHgps8g-MYXISdMP79os/s1600/image-20170202_224128.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhd252PH_QXK2mpXpNL0ZskGOo8U5I6tYuTkskmJnCdCEx9-8N6fIdGLurAB_-pDvMYIWWQWYWjyXZ6OHHfHf-4L16XoGo_45-_NCcs9LBAtVHkZluaO3w3e1bjvHgps8g-MYXISdMP79os/s640/image-20170202_224128.jpg" width="358" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">toooo many clamps, and yet often not enough clamps</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJFtgvkaHbDJWswxV17Dht1Uv6EgbCMH5EVidRrG5erfku1SkP7gzdzbU3oU5Y22wfizN3UUY60pdfmoUxqzEreQjSqYLCZoEYDUvl7nTy7QFYdp_V67C83gB6-WeeQ-fBBKUpm2hFvGB6/s1600/img05_1.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="360" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJFtgvkaHbDJWswxV17Dht1Uv6EgbCMH5EVidRrG5erfku1SkP7gzdzbU3oU5Y22wfizN3UUY60pdfmoUxqzEreQjSqYLCZoEYDUvl7nTy7QFYdp_V67C83gB6-WeeQ-fBBKUpm2hFvGB6/s640/img05_1.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Started using pcord to compress everything while the glue dried</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjxy6uRYpNYiT_i4SzYjNYFHmbRO2vZ9pp9pH1snS53hCRk8RKzZlvao9ia_mR3IHYTTVT6FAw7cVnFvF7aFOiZrEnbwcwYVxQdMPQz9v5J1Ci-f_l9eHi8SQaeZxi8zZLz9fjExbRsHOW/s1600/img07.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="480" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjjxy6uRYpNYiT_i4SzYjNYFHmbRO2vZ9pp9pH1snS53hCRk8RKzZlvao9ia_mR3IHYTTVT6FAw7cVnFvF7aFOiZrEnbwcwYVxQdMPQz9v5J1Ci-f_l9eHi8SQaeZxi8zZLz9fjExbRsHOW/s640/img07.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Some creative uses of string-clamps and real-clamps</td></tr>
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<h3>
Testing:</h3>
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Did I start a project just to ensure I'd go to the gym more? Whooooo knows.</div>
<div>
I took the climbing foot to BKB-Somerville and played around on the bouldering wall.<br />
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First experiment was exploring toebox performance with the prosthesis on the wall. I picked some holds near the ground so I could apply weight by hand (I have two biological legs, so figuring out how to rigidly attach a prosthesis to myself was a no go)</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWGT3-NZe9NWyuX-3zfiztsjbORAmRVn6MY7yYegKnaqeHglWy8UWy-eee1ZhRcO0qVeiL4iWa302eaO3Pj6983WDI4zSZ4RV8HItDHWXjIqL4ETK1eNLNEDvLax3pjV6PGn2EgJY94jCy/s1600/img13.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjWGT3-NZe9NWyuX-3zfiztsjbORAmRVn6MY7yYegKnaqeHglWy8UWy-eee1ZhRcO0qVeiL4iWa302eaO3Pj6983WDI4zSZ4RV8HItDHWXjIqL4ETK1eNLNEDvLax3pjV6PGn2EgJY94jCy/s200/img13.jpg" width="150" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmbi1iRg58PhnbJx-blXw46eBOCvr7Ju33Hku1k9U5QMjqYBlH7p8svb8xFUr7KJSUCE77y6ncYfRS8UWDkf6Ay3MFhbwQKNDmHq_d7ziFdeGqAIPvXWyGiT2pfw-WVRS22axgia-03Kd2/s1600/img12.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgmbi1iRg58PhnbJx-blXw46eBOCvr7Ju33Hku1k9U5QMjqYBlH7p8svb8xFUr7KJSUCE77y6ncYfRS8UWDkf6Ay3MFhbwQKNDmHq_d7ziFdeGqAIPvXWyGiT2pfw-WVRS22axgia-03Kd2/s200/img12.jpg" width="150" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtGQBIeSH1-6dfYO78000qFByrx_8tkOWaXp6yHP_BXmsIE_HQLhcHW_lFaW3iO9qXDKU5etKdnXCPKpnuvlFiZJ9PPCYMPapR_a8j0q_2coYqEsCEv7Jnwl4m8vTOxkmgxlZ8WW0gxpgy/s1600/img11.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgtGQBIeSH1-6dfYO78000qFByrx_8tkOWaXp6yHP_BXmsIE_HQLhcHW_lFaW3iO9qXDKU5etKdnXCPKpnuvlFiZJ9PPCYMPapR_a8j0q_2coYqEsCEv7Jnwl4m8vTOxkmgxlZ8WW0gxpgy/s200/img11.jpg" width="150" /></a></div>
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The toe seems to grip well, despite having the side-rubber-wings peel up a bit. I didn't have a problem finding traction using the flat front or the corners of the shoe, but I expect this foot would have problems with cracks and narrow&vertical pockets. But overall this shoe reasonably performed all the footwork positions regular shoes do.<br />
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<a href="https://www.climbing.com/.image/c_fit,cs_srgb,w_620/MTM1MjQzNDcyNDkwNzc2NTg2/sloper.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="176" src="https://www.climbing.com/.image/c_fit,cs_srgb,w_620/MTM1MjQzNDcyNDkwNzc2NTg2/sloper.png" width="200" /></a><a href="https://www.climbing.com/.image/c_fit,cs_srgb,w_620/MTM1MjQzNDY5MjY5NjA0ODMw/pocket.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="176" src="https://www.climbing.com/.image/c_fit,cs_srgb,w_620/MTM1MjQzNDY5MjY5NjA0ODMw/pocket.png" width="200" /></a><a href="https://www.climbing.com/.image/c_fit,cs_srgb,w_620/MTM1MjQzNDcxNDE3MDIyOTQy/small-edge.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><img border="0" height="176" src="https://www.climbing.com/.image/c_fit,cs_srgb,w_620/MTM1MjQzNDcxNDE3MDIyOTQy/small-edge.png" width="200" /></div>
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<span style="font-size: x-small;">Common footwork technique examples</span></div>
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<span style="font-size: x-small;"><a href="http://www.climbing.com/skills/training-7-simple-drills-to-improve-footwork-and-technique/">Images from www.climbing.com</a></span></div>
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Second experiment was to try climbing with the shoe. For this bit I made a small HDPE form and lashed it to a flip flop.</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwUBzcIWTXXm67qhMYorlgMIPCALroe_x8hcfhFXWuR9Wljb10nUNamxBFH3DjBWgyIHxjUJnp3LTcHdu5emFuRvbxdu-SpwtSgK7Q-lOVjAjzRWpWzIOWROO2JXTGmQtwlJ8zPVarRLHd/s1600/img09.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjwUBzcIWTXXm67qhMYorlgMIPCALroe_x8hcfhFXWuR9Wljb10nUNamxBFH3DjBWgyIHxjUJnp3LTcHdu5emFuRvbxdu-SpwtSgK7Q-lOVjAjzRWpWzIOWROO2JXTGmQtwlJ8zPVarRLHd/s320/img09.jpg" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A really silly test setup</td></tr>
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This setup was far from ideal - neither the compliant flip flop nor the shape of the too-short plastic insert helped me put bodyweight at the toebox. In addition, my foot is wider than the prosthesis, so I couldn't properly utilize some of its nicer edging qualities.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhB2Qp1-8gdTyHYX8kOKlKPjOp2h6oxzOiNsZxX0-SO7tHMoIXOe6wumDG50vnvlpm_LhwNaq4_Q8ztdx_AupT-kv6RQoQz3DscU1FrDC8u3OEm0Gvtg1BohP7m8hU_8dUwk583FpVbMOJg/s1600/img20.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhB2Qp1-8gdTyHYX8kOKlKPjOp2h6oxzOiNsZxX0-SO7tHMoIXOe6wumDG50vnvlpm_LhwNaq4_Q8ztdx_AupT-kv6RQoQz3DscU1FrDC8u3OEm0Gvtg1BohP7m8hU_8dUwk583FpVbMOJg/s640/img20.jpg" width="480" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Climbing with floppy-foot - notice how far the toebox is able to bend with this setup</td></tr>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMuoFkcvXz_qPle46YsP2tGTxiTfj6MgLXKwsLWOCmkGzpM79rgCiOBv9l8JpN58GR47gSTYvR7S6U2Ves2UmK8PvWw-9JaG1xCOGmdkervPxkBxXEfYEHwyslPQszBkbhinw2FxZX1jAV/s1600/img21.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhMuoFkcvXz_qPle46YsP2tGTxiTfj6MgLXKwsLWOCmkGzpM79rgCiOBv9l8JpN58GR47gSTYvR7S6U2Ves2UmK8PvWw-9JaG1xCOGmdkervPxkBxXEfYEHwyslPQszBkbhinw2FxZX1jAV/s200/img21.jpg" width="150" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgt4xRuXVxMaY2Tj41mU-Pj1gim_5WFgQHc4gf9wN7vy5_RB67wthgFnFrn6xBn1pFaoPDBOwo6MPDIF6L5SoXZLnuAqKTHIUmGknRZw6NaEMzy3NHYzTJTbm22_f-2BT88VyZ-1v8CGk0/s1600/img19.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgt4xRuXVxMaY2Tj41mU-Pj1gim_5WFgQHc4gf9wN7vy5_RB67wthgFnFrn6xBn1pFaoPDBOwo6MPDIF6L5SoXZLnuAqKTHIUmGknRZw6NaEMzy3NHYzTJTbm22_f-2BT88VyZ-1v8CGk0/s320/img19.jpg" width="240" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFaw7fInwi9TAk81HTQ9GFdM-O69AturBNTTB6zA0aairLp7U7FnXm8xvYd6xWNdmt2CUR30Z_XKOJUWgp_zG58tNr_qTftJZtbwgmqc5OGk0tzWTvqs_6AmEpiRo94YSXUGNRUu21fr45/s1600/img22.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFaw7fInwi9TAk81HTQ9GFdM-O69AturBNTTB6zA0aairLp7U7FnXm8xvYd6xWNdmt2CUR30Z_XKOJUWgp_zG58tNr_qTftJZtbwgmqc5OGk0tzWTvqs_6AmEpiRo94YSXUGNRUu21fr45/s200/img22.jpg" width="150" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkSk3IDGbakSoZq56EkVckwrsDul0b1omZOu0X0TDkgBBARhmSEQ4h4hTgc0CcFhUeQCFCWYvAOm_cVT4lhilVKE2loIONZIjckMn5Eddu_QJ5ywXOmYWzgr_M-Xqv8GwmAz1mJjuaoebt/s1600/img23.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhkSk3IDGbakSoZq56EkVckwrsDul0b1omZOu0X0TDkgBBARhmSEQ4h4hTgc0CcFhUeQCFCWYvAOm_cVT4lhilVKE2loIONZIjckMn5Eddu_QJ5ywXOmYWzgr_M-Xqv8GwmAz1mJjuaoebt/s200/img23.jpg" width="150" /></a></div>
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In the test climb videos, you can see how I avoid using the toe on some smaller holds. I also pretend that my foot only consists of the surface covered by the shoe and deliberately test different foot positions, which results in some wonky moves. But the shoe didn't slip off the plastic, and it felt pretty good!</div>
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<iframe allowfullscreen="" frameborder="0" height="360" mozallowfullscreen="" src="https://player.vimeo.com/video/203732439" webkitallowfullscreen="" width="640"></iframe><br />
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I took the hiking shoe out on a sunny day, got some glamour shots of it with the prosthesis on some rocks (below), and then ran around on it with the flipflop. This field test highlighted how fragile this concept shoe was - I managed to destroy it after only a few minutes on relatively flat ground. Next time, I shouldn't rely on the sock inner rubber to make any structural bonds and should make a sewn-fabric skeleton instead.</div>
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The hiking sole worked as well as your average sneaker on dry ground, but the shoe became unusable before I could test it on anything muddy or wet.</div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX2Xbbzn9Dt4dB72xWK_VprvObfaWAoVTjbtJbejZEOfBO5Wncg0HHdlyT1jovDWbtJFU-ZDm-fN51JHfOKwHUeJIFRoCXhvT-mJfOXX1Rep3QWYfuitvJho07tjWPIeHNPdAODdz5jqbi/s1600/20170206_092958.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX2Xbbzn9Dt4dB72xWK_VprvObfaWAoVTjbtJbejZEOfBO5Wncg0HHdlyT1jovDWbtJFU-ZDm-fN51JHfOKwHUeJIFRoCXhvT-mJfOXX1Rep3QWYfuitvJho07tjWPIeHNPdAODdz5jqbi/s320/20170206_092958.jpg" width="240" /></a></div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKge8YUhwQsQP8yOurSGYdPBJYhaXT5oXyBykP9CTECmraPWZdFBl6-UqQlwI-ZILMQ6iOncCjDFGVBcIkDi9Q2pbUCk-owGz8i3Q66_yUQR_K0IyPJW2trdrLOoxu9QFwJnE0hiY14cXc/s1600/20170206_093009.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgKge8YUhwQsQP8yOurSGYdPBJYhaXT5oXyBykP9CTECmraPWZdFBl6-UqQlwI-ZILMQ6iOncCjDFGVBcIkDi9Q2pbUCk-owGz8i3Q66_yUQR_K0IyPJW2trdrLOoxu9QFwJnE0hiY14cXc/s320/20170206_093009.jpg" width="240" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">See the adhesive failing? Rubber is a tricky material</td></tr>
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<h3>
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"Conclusions and Future Stuff"</h3>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMjzxsZhyj_X0-_W5yKnaYhY0KeGtkkdCZbM8NymtYyDjoP5wxbrzAxedSDDAutTuq-8_j4V_tvVFL4j12SUHzDabq1Ngt-0lJmqjww8leTVsahcv6QdlzATumYpbhS4PFny4auA6NyPq_/s1600/20170206_132138.jpg" imageanchor="1" style="clear: left; float: left;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMjzxsZhyj_X0-_W5yKnaYhY0KeGtkkdCZbM8NymtYyDjoP5wxbrzAxedSDDAutTuq-8_j4V_tvVFL4j12SUHzDabq1Ngt-0lJmqjww8leTVsahcv6QdlzATumYpbhS4PFny4auA6NyPq_/s320/20170206_132138.jpg" width="320" /></a></div>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWk-p6ovd5RUz1E3TqbVRj__TV4O5LYBuouoYlX3UH-AkFNtnzTUqdo9L300_z0_d0rKVUf2AZ-ZRiF4sh9xfOIc6cXLgvjHQM0l9dNXV8hIMXX7TqF0Mt3d_cEpy-iwBy3IgkOUp8EUOX/s1600/20170207_231541.jpg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiWk-p6ovd5RUz1E3TqbVRj__TV4O5LYBuouoYlX3UH-AkFNtnzTUqdo9L300_z0_d0rKVUf2AZ-ZRiF4sh9xfOIc6cXLgvjHQM0l9dNXV8hIMXX7TqF0Mt3d_cEpy-iwBy3IgkOUp8EUOX/s320/20170207_231541.jpg" width="310" /></a><br />
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Techfair came and went - I shared tables with friends' startup company and showed demo videos of the feet. I'm excited to also show off this work to Hugh soon and see if he would test a more robust version of these shoes.</div>
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Conclusions - </div>
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<ul>
<li>While the soft rubber "sock" nicely achieved the objective of holding the shoe in place when pressure was applied, it was thicker than necessary and would have been better as several layers of thinner rubber bonded together.</li>
<li>The Renia Colle de Cologne adhesive worked well on both fabric and rubber, but was not magic. It only prevented peeling when the materials had large contact areas (not good for joining corners)</li>
<li>The retaining band did essentially nothing. Next iteration should use plastic clips or similar light-load solutions for countering shoe inertia when the foot swings in the air. Luckily, the sticky-rubber idea worked well for holding things in place under load, so I now know that the new retaining mechanism only needs to deal with the shoe's own weight.</li>
<li>I should form a pointed, rigid toecap for the next climbing shoe to make it more talon-like.</li>
<li>The next versions of these shoes should incorporate more rigid materials and less rubbers - nearly everything could have been improved with greater stiffness.</li>
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<li>I can climb 5.7 to 5.9 and V0 gym grades in flipflops, but it's terrible.</li>
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<br />Avahttp://www.blogger.com/profile/04980159405064233541noreply@blogger.com0