For the third annual Canstruction Madison event, I wanted to build a structure that moved.

The idea of a roller coaster was the right combination of engaging, fun, and in constant motion. I used Sketchup to figure out what the shape of the roller coaster would be.

The structure would be constructed mostly with canned food. The "trains" riding this rollercoaster would be cans, too.

The curves of the roller coaster track needed to be smooth, so the height of each can column needed to be precise. We got enough precision by using cans of two different heights: tuna shown as green on the bottom and normal shown as other colors. I wrote a script to calculate the ideal combination and quantities of cans for each column.

We were pretty confident we could build this, so we got started.

We decided to build the lift hill first which meant constructing a frame and connecting bike chain to a motor. Thankfully, Budget Bicycle Center donated the 18 feet of bike chain we needed.

At the bottom of the hill we attached a 12V DC motor to a sprocket fitted inside the bike chain. At the top of the hill the chain was fit around two pulleys.

We took some thick wire and used it to make a hook and welded it to the bike chain. We broke a lot of chain links getting this right.

When we stacked the cans next to the frame, the stacks were pretty unstable. The tuna cans at the bottom had a curvy top surface and the tall cans stacked on top weren't the right diameter for it. To give these cans a stable base, we cut cardboard circles that fit on top of the tuna cans to provide a flat surface.

We stacked mini cereal boxes end-to-end along both sides of the bike chain. The hook fit in between and was able to carry a full can up the hill.

We used clear acrylic corner bead on the inside corners of the boxes to provide a smooth surface for the lifting can.

At this point, we moved into the paint booth to get working on the rest of the track.

We added railings to the lift hill using the same corner material as before to keep the cans on track. We ended up needing to add railings to the entire track. We used cutters to remove chunks of the railing material to allow it to flex.

Two pieces of thick wire were used to shape the track. Every few inches we tied the wires together with a sandwich of window blind material and liberal amounts of hot glue. Some of those ties were used as anchor points for tall PVC towers that would be hidden between can columns. These towers provided most of the support for the first half of the track.

The cans under the track were stacked two-wide with a single coconut can centered itself on top. We used cardboard rings glued together to lock the two columns together with one can on top for stability. This meant each pair would sway and move together from the weight of the rolling can but not too much.

Many cans and cereal boxes later, the track was complete and connected into one loop. We turned on the motor and let some cans run the course a few times. It took some adjusting but the runs became more consistently good.

Now we started to work on the tunnel. We used a thick piece of wood as a shelf to hold the cans above the tunnel.

It took us a few weeks to get to this point. All of the cans, cereal boxes, and track were finally in place. We attached cardboard rings to the sides of the lift hill frame to keep those columns of cans from swaying too much.

The event takes place at a sports complex on the turf of two indoor soccer fields. Teams build on top of plywood for a flat base to build on. We brought our boards from the shop with markings to show where each can should go.

It was a stressful afternoon rebuilding the structure into a coaster that still worked. Some parts of the track didn't work the same as before. But many hands made light work, and we adjusted and taped, adjusted and taped, and taped some more.

The most hazardous can columns were put up last. These were the tall ones just after the lift hill. To cover up the frame and cardboard materials, we taped Kool-Aid packets along both sides of the track.

Some of the PVC supports were visible on the inside of the first two corners, so we conjured some faux trees to hide them. The battery and motor were hidden under the green cloth.

The coaster won the People's Choice award.

All of the food was donated to the food pantry, and the frame and track materials were repurposed.