Algodoo

Controls:
R Arrow - Forward
L Arrow - Reverse
Down Arrow - Brake

As you start the drive wheel (one on right), the clutch will begin to let out and as it catches, the output wheel (bottom) will begin to spin. When you let up on the drive wheel, the clutch pulls back in and the output wheel spins freely to a stop while the drive wheel is not moving. Also, under a certain limit (haven`t taken the time to find it) of rpm`s, the drive wheel will spin freely while the output wheel doesn`t move.