Originally Posted by Slamnasty' date='Feb 12 2005, 11:34 AM

They likely get the counter-rotation of the green trilobe by starting each trilobe offset a few degrees of rotation from the other.

Whereas the yellow trilobe's position starts with its respective piston wheels on one side of a lobe peak, the green trilobe's position starts with its respective piston wheels on the opposite side of that same respective lobe peak. Therefore it's using the horizontal force of the pistons to produce two rotational forces when coupled with the shape of the trilobes.

This dual, simultaneous coutner-rotation likely keeps the forces pushing and pulling the pistons even.