Abstract: A device for translating linear reciprocal motion to rotational motion includes a reciprocating linearly moving piston with a central slot. The aperture has a set of recessed annular gears opposite each other which engage corresponding gear teeth on a cog located on a crankshaft that rotates inside the piston. Connecting braces on the crankshaft imparts an offset on the crankshaft and a corresponding lateral force on the cog, keeping the cog engaged with the recessed annular gear which imparts a rotational force upon the crankshaft.