Flywheel & Displacer
The flywheel (shown upside down) provides momentum to bring the engine through the full cycle. The attached foam displacer moves air back and forth between the hot and cold chamber sections. The flywheel is made of 1/8" thick 6061 aluminum. The short tab counterbalances the foam. The flywheel has six spokes of which two are hidden by the foam. The three pie shaped sections of the flywheel hidden by foam are filled with foam. This prevents the outer foam sheets from flexing which would reduce compression. The foam was cut with a hot wire to 1/8" sheets and then scissor cut. The center hub is brass and press fits to the flywheel. (Not shown is the latest variation which screws to the flywheel with 3 screws.) The ends of the brass hub slip fit to ball bearings. The thin crank shaft is 1/16" music wire (steel) press fit into the brass. Hidden on the other side of the flywheel are two pieces of tape for precision balance. Alternatives: the flywheel could be a solid disk of thinner and lighter material however it must be flat to avoid wobble.