Friction wheel 1 rotates about fixed axis A and contacts two rollers 2 of equal diameter which rotate about fixed axes B and C. Ring 3 is freely mounted on rollers 2. Rotation is transmitted from wheel 1 to ring 3 through rollers 2. The required normal force for transmitting a torque is developed by the weight of ring 3 which rests on the rollers.
$3369$SmF,3L$