An epicyclic traction drive transmission, including a carrier 7 having a central axis, a sun shaft 9 rotationally mounted within carrier 7 and positioned in the central axis, a plurality of planet rollers 4 mounted on carrier 7 and arranged to rotate on respective angularly equidistant axles 5, and rotationally engage the sun shaft 9, and an outer ring 1. A wedge roller 2,3 associated with each planet roller 4 is free to translate relative to carrier 7; and engages outer ring 1 and respective planetary roller 4 with a frictional or traction coefficient , and the wedge roller 2,3 defining a wedging angle , such that tan /2 is less than . In one form there are two wedge rollers 2,3 for each planet roller, allowing for a wedging action in either direction of rotation.

An epicyclic traction drive transmission, including a carrier 7 having a central axis, a sun shaft 9 rotationally mounted within carrier 7 and positioned in the central axis, a plurality of planet rollers 4 mounted on carrier 7 and arranged to rotate on respective angularly equidistant axles 5, and rotationally engage the sun shaft 9, and an outer ring 1. A wedge roller 2,3 associated with each planet roller 4 is free to translate relative to carrier 7; and engages outer ring 1 and respective planetary roller 4 with a frictional or traction coefficient , and the wedge roller 2,3 defining a wedging angle , such that tan /2 is less than . In one form there are two wedge rollers 2,3 for each planet roller, allowing for a wedging action in either direction of rotation.

A motion producing device comprising an output member with a contact surface and a reference member. An actuator member is attached to the reference member, the actuator member having a traction surface and comprising actuator zones, each actuator zone being energizable to move a corresponding portion of the traction surface to change a contact state of the traction surface with the contact surface depending on an energized state of the actuator zone. An energy source is operatively coupled to the actuator zones for sequentially changing the energized state of the actuator zones. The actuator member provides a torque transmission path between the reference member and the output member.

A motion producing device comprising an output member with a contact surface and a reference member. An actuator member is attached to the reference member, the actuator member having a traction surface and comprising actuator zones, each actuator zone being energizable to move a corresponding portion of the traction surface to change a contact state of the traction surface with the contact surface depending on an energized state of the actuator zone. An energy source is operatively coupled to the actuator zones for sequentially changing the energized state of the actuator zones. The actuator member provides a torque transmission path between the reference member and the output member.