Abstract: An axial mechanism for converting between linear reciprocating motion and rotary motion comprises a z-crank shaft, a wobble member rotationally mounted to the angled crank pin of the z-crank shaft, and one or more pistons with a connecting rod between each piston and a pivot joint to the wobble member. In one embodiment the connecting rods have sufficient inherent flexibility to accommodate sideways motion in a 360° orbit at the wobble member end of the connecting rod. In another embodiment there is a lubrication communication passage from within the wobble member to each of said pivot joints. In another embodiment each such pivot joint is fitted to the wobble member an integral unit. In another embodiment the z-crank shaft is supported for rotation by bearings all positioned to one side of the z-crank shaft, spaced along the output drive end of the z-crank shaft.