transfer ring is compliantly tethered by suitable means to prevent it rotating but allowing it to oscillate about the inner output 3 increased leverage makes the force applied rise steeply when the pressure wheel 2 rotates and tries to force the contact point 5 with the intermediate ring 1 off a notional line 6 connecting the contact point and centres of the output wheel and the transfer ring causing the ring to oscillate and the output 3 to rotate output direction is contra to input the rotating pressure may be on the outside of the transfer ring pressing the transfer ring directly against the inner output wheel or may act on the inside of the transfer ring pressing outwards and forcing the opposite side of the transfer ring against the inner output wheel also the rotating pressure may consist of two or more pressure points on either side of the contact point between transfer ring and inner output wheel transfer of torque between the transfer ring and the output wheel may be by usual friction means or by positive means such as teeth or roller teeth the present invention is capable of being finely balanced because the input and the transfer ring move as one mass with unchanging weight distribution optional disconnection of output from input can be effected by moving the rotating pressure wheel or wheels away from the transfer ring allowing the transfer ring to disengage.