I'm working on a project involving analyzing the motion of a reciprocating saw. This saw converts rotational motion from an electric motor to linear motion by means of a slider crank mechanism. The power transmission goes from motor and attached driving gear, to crank, to connecting rod, to slider (which acts as a blade clamp). The crank has non-uniform geometry. It has extrusions on one half and two holes on the other. My immediate assumption was that the geometry was intended to create an offset center of gravity. This would result in a varying moment of inertia when driving the crank with the motor. When the center of gravity is closer to the motor, it is easier to rotate. When it is further from the motor, it is harder to rotate. This essentially means the crank acts as a fast return mechanism that causing the cutting phase to accelerate faster than the extension phase. Here's my question: are non-uniform holes (and extrusions in this case) in gears intended to offset the center of gravity? I assume uniform holes are just made to lighten the gear and allow for better cooling. I haven't been able to dig up any information on the purpose of gears with non-uniform geometry. It would be great if anyone on the forums could confirm my hunch. I've attached an image of crank solid model.