Next up on the Low Temperature Differential Stirling Engine was the displacer block, which was made of foam. Before I could cut the foam, however, I needed a foam cutter! I found plans from Make Magazine in the Five-Minute Foam Factory article and adapted them to build my own specialty foam cutter.
In this project I reused a variable DC transformer (AKA speed controller) from an old train set, but you can find one here.
First, I measured out the distances I would need to cut, estimated some tolerances, and layed out the arm on some scrap plywood (everything here was a little loose).
Next I cut the arm out with a sabre saw.
I drilled a hole in the bolt and a hole through the plywood so that the bolt could slide through it.
I made a base out of one large rectangular piece and two slats. The base has a rectangular hole in the side so that the arm can fit into it.
I screwed the arm to the base and pushed the bolt through the top hole. I inserted a brass brad in the base and threaded nichrome wire from the brad to the bolt hole and tensioned it with a spring.
To make sure the brad didn’t come out, I bent the nichrome wire around a washer. Next, I hooked the transformer up to each side of the wire and was able to easily cut foam!
Cutting a cylinder on the verticle cutter:
I made a variant of this foam cutter with two bolts (for height adjustment) and a tensioning block in order to make a horizontal wire cutter to plane blocks.
Planing the cylinder to the proper height with the horizontal cutter:
