Make a circle and center hinge it then put two(or however many you like) symmetrically
on the edge of the circle and center hinge them
then make a spring from the top diagonally to the by the side
of the circle then set the dampening to -0.1 for a simple one.

     The balance between the negative spring dampening and the outer balls density controls
the speed, torque and power.

Here an example of a use for it http://www.phunland.com/phunbox/details/19593

Last edited by Gryphen (2009-05-22 00:54:05)