[JesseK]

This isn't a suggestion, this is simply how we did it. In hindsight, we probably should have asked for better techniques to aid us in perfection. We decided to bend things for prototyping on the spot, and it worked out so well that we've used the same techniques to do the final product.

For this year, we've bent 3 radii: 20", 13", and 3.5" and none with any typical bending equipment. For the 40" bend we used 1" square tubing, and even though the final product isn't perfect it still works well since it's a low-load/stress piece.

First, we used a 2" sheet of wood at least 40" x 20", a bunch of clamps, and some muscle. Using a pencil/marker tied to one end of a string, we measured out 20" to create a radius. We put the 20" mark of the string down on a point of our 2" sheet and marked out our semi-circle. We used a bandsaw to cut out the semi-circle.

What you do from here depends on whether or not you have a blow torch. The torch is used to heat the metal while it's bent in order to let it settle to its new shape when quenched (cooled). This keeps it from springing out back to a greater radius when the clamps are removed. If you do not have a blow torch, you'll need some extra clamps & time and also to cut another ~38" semi circle from inside your 40" one. You will clamp the metal to the wood to create your bend and let it sit clamped long enough to settle.

We then clamped a scrap piece of wood directly to the right of the semi-circle, about 1 1/4" from it. This gave us something to leverage off of as we bent the tubing around the wood template. We bent the metal around the wood template, gently clamped everything in place, and used the blow torch to heat the metal as evenly as we could. We then used wet cloths to cool the metal, then threw it out in the snow for a few minutes to completely cool it. Now it's as rigid as if we had welded it.

Make sure you have one person designated with a fire extinguisher and that everyone has gloves/eyewear. It took 6 students and 1 mentor about 45 minutes to fully bend three 20" radii pieces.