Abstract: A variable angle wobble plate drive for varying piston displacement has constant velocity coupling from the wobble plate to the frame which permits all axis-dynamic balancing. The coupling uses an idler element rotating on a tilted axis portion of the shaft, and conical gear sets connecting the idler member to the machine frame and the idler member to the wobble plate. The sum of the acute angles from the tilted axis to the shaft, and to the driving axis, is made greater than the maximum driving angle thereby permitting low reaction torque on a driving angle control mechanism without reversal of control torque.