Feb 10, 2015

Top Plate, Nutstrips, and Caster Parts

Ripstik: slowly and steadily coming together! 

The shiny blue shim steel I'm using for the top plates (aesthetic purposes) is really thin (0.03"), so it was sandwiched between sacrificial plywood and 1/8" 6061 aluminum to make sure it didn't warp while waterjetting, 

In addition to that, I'm milling angles on my tube cutouts so that they properly attach to the bent chassis.

The top plates will attach to the chassis with nutstrips, pieces of 0.5" square extrusion with 1/4-20 tapped holes every inch. Marking and powertapping all these holes took a while.

 Here I'm testing a quick caster-lock idea. A caster consists of an upper half and a lower half, with a common pivot shaft (1). If I have a slab that can slide through slots in both halves, I can lock and unlock the caster.

Once convinced that my lock idea would pan out, I proceeded to make all the parts.
Milling the angle blocks to 21.5°. These blocks connect the caster assemblies to the chassis.
kingpin/bearing assembly

freshly-waterjetted caster parts

Feb 3, 2015

TIG Welding Aluminum (poop welds)

I needed to fix cracks in my ripstik chassis caused by the bending brake. The front portion, in particular, really needed fixing. A well-intentioned friend found it cooling down in the oven, decided I probably kept it in the oven for a reason, and left it in while baking cookies at 350°F. (This is close to the tempering temperature for 2024) My metal ended up heat-hardening and even after another stint in the oven still ended up with massive cracks.

Some panels even had full blown tears on the edges. I definitely didn't want to rest any weight on cracked panels, so I asked the Media Lab shop guys for advice. They pointed me to the TIG welder, taught me how it works, and told me to practice on scrap.

It took me three days of practicing and a bunch of scrap metal before I felt ready to try the real thing. I've never welded before, so starting out on TIG and aluminum was especially difficult. Luckily for me I had plenty of practice material.


Judging the distance I needed to keep between the torch and my workpiece was pretty hard. I crashed a few times, which meant I had to stop and regrind the tungsten shaft.


Once I was confident with my abilities on the scrapped interior shells, I started fixing cracks on the real thing. The result was not pretty, but it was effective.

photo cred: Melody Liu

+ me at the welding table!