This double compound elbow engine was designed and built by Joe “Speedy” Sciarratta. Plans for this engine have been around for a while, and it’s a fun one to watch in motion, but Joe Sciarratta took the basic plans one step further in this version. The basic engine has only five moving parts. Three pairs of pistons (each pair 90° between the two) move in holes in a round valve cylinder to drive the flywheel. As each piston goes up and down in the valve cylinder, it moves in and out of the flywheel. With this particular engine, the exhaust from the first engine drives the second valve cylinder in the opposite direction to run the other flywheel at a slower speed when air pressure is supplied to the first engine. Watch a video of the engine running below.