A Novelty Desktop Toy. A basic single planetary gear with a piston attached. The ratio is 1:2 allowing for a point on the gear tooth to travel the length of the shell diameter in a linear motion. I've connected a shaft piston to this point using a cut length of paper clip. It probably could be redesigned better. But works fine at the moment :) Enjoy I gave my Printed version away, and didn't take any pics. Ill post some next time I print it again. 5/06/2013 Vertices fixed ! Also Shortened the crankshaft so that it does not protrude as much. Updated files Files housing.stl and PlanetaryGearAndPiston-ALL-Parts.stl Instructions At the moment there's nothing to connect the end of the con-rod to the gear. I melted a bent piece of Paper clip to the end so that it protruded down into the hole in the gear tooth (after It was assembled!) and it worked very well but its not ideal. I also replaced the 5mm printed shaft between the piston and con-rod with 2x course counter sunk Computer case screws.