I have a drive belt which transmits torque between two perpendicular shafts. I'd like to model it in a way such that I can use the "Path Length" measurement to make ordering to length easier. As it stands, I have two semi-circles connected with lines and a circle sweeping the path. The are points in the center of each semi-circle to allow for coincident mating to the axis of the shaft in assemblies.

How can I make the path smooth in order to use Path Length?

Seems like a great time to use equations to me.