I started this “model” intending to make something else. Hopefully the other device will be made, but I’m not ready to talk about it yet, so be sure to check back or subscribe to my RSS feed.
Part of I was trying to come up with was something that would push four “arms” out one at a time, however, this has been done many many times as a radial engine. Most were used in aircraft, especially those in the WWII era. In an actual radial engine, the number of pistons are actually odd, so a four-cylinder wouldn’t generally be seen. Also, it’d be the pistons providing the power to a central crankshaft, not the crank (through a small air-freshener motor) providing the power to the pistons.
Either way, it came out as a neat contraption. I used an arcade-style button to turn power on and off and the gears were cut with my CNC router out of 1/4 inch MDF. The base and “pistons” are also made of MDF. The squares on the sides that restrict the “piston” motion are made out of 2″ x 2″ polycarbonate that I happened to have from another project. The slots in the polycarbonate are at 1/4 inch increments to allow for the spacing of the shafts. They’re bolted down with 6-32 machine screws.
When I first tried to start this thing, I had it fastened vertically, and the little motor couldn’t overcome gravity to make the middle gear spin all the way around. It worked much better in a horizontal orientation.
I thought the arcade-button made a nice addition, and one was just laying around, so why not? They’re easy to install using a 1 1/8 inch spade bit! Also, that motor was taken from an air freshener – a great source of parts!
Edit: I’ve made an improved version of this device that can be seen here. No air fresheners were harmed for the other radial engine model.