Input: the blue shaft with a cone disk.
Output: the yellow shaft with a cone disk.
The orange spherical caps idly rotate on their axles and are forced toward the cone disks by red springs.
The green shafts carrying the caps axles can rotate in fixed bearings.
The orange screw has two thread portions of opposite hands.
Turn the screw to change contact position between the disks and the spherical caps for various output velocities.
Using two caps instead of one reduces shaft bending forces.