Aug 27, 2017

2015 EC Rollercoaster Construction

Boston Globe article with photo of rollercoaster and headline "Why yes, that IS a roller coaster on MIT's campus"

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!)

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 2015 rollercoaster! (only two years delayed........)

three students digging with shovels
Digging holes for a cinderblock/pier block foundation

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?

"We're cool people! Build cool things with us!"

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.

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, sometimes they're mildly different. 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.

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)

spreadsheet calculations for allowable yield and bending stress
Some examples of the structural calculations
dimensioned engineering drawing of roller coaster
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.

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!

vertical posts and ground-floor spandrel beams installed

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. 

The 2014 and 2015 towers were attached to the fort. The 2017 coaster tower is separate.

non-dimensioned engineering drawings of main two storey tower

person on a ladder fastening bolts through vertical posts while another person stabilizes the ladder
Starting to install 3rd floor spandrels

towers with timber guardrails, one railing 21" above floor height and one 42" above floor height per OSHA guidelines
First things to go up on every floor are temporary safety railings.

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.

engineering drawing with dimensions and parts list
A representative frame's construction sheet

engineering drawing with planned distance to each main track support
Locations of each frame

students connecting main structural supports
Frame Assembly

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.

students driving screws with hand drills
Putting track sections on the vertical drop.

dimensioned engineering drawing with parts list and requested quantity to build
Instruction sheet for a track section
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.

engineering drawing with estimated vertical heights of track supports
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.

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"
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"

Adding vertical supports to the track units. 

image of the roller coaster cart after an unmanned trial run

And that's the coaster! There's a good construction timelapse video of the fort and rollercoaster below.

(video credit: Banti Gheneti)

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!)

I didn't have any pictures of it from REX, but I did take some afterwards when it was in storage.

wooden cart minus bucket seat

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).

close up view of wheels encased in a thick plastic film

The cart clears the steep track curvature by having a bent frame, ~10deg total.

closeup view of aluminum plate joining two angled pieces of wood

So what made this rollercoaster different from the previous year's? Not much, except for the vertical drop. How vertical is vertical?
safety sign showing a truck falling off a cliff with caption UNDEFINED GRADE
Art credit: Emily Tencate

screenshot of list of angles of descent for current steepest wooden rollercoasters
We set out to beat this record and make a true vertical drop. And we did!

angle measurement of 90.3 degrees from the horizontal, slightly steeper than a vertical drop
Technically beat a world record! (Steepest Drop, Wooden Rollercoaster)
We reached out to Guiness world records, but they didn't make it over in time for deconstruction. Oh well.