an input shaft, the input shaft comprising an engine-engaging first input shaft end, a shaft-engaging second input shaft end, a rotation transmissive portion, and an input axis of rotation, the rotation transmissive portion extending intermediate the first and second input shaft ends for transferring engine-originated rotational motion to the transmission assembly via the first input shaft end;

a cylinder arm assembly, the cylinder arm assembly comprising an input arm end and an output arm end, the input arm end each being geared to the rotation transmissive portion, the rotation transmissive portion thereby enabling rotational movement of the cylinder arm assembly;

an output shaft assembly, the output shaft assembly comprising an output shaft and an annular member, the output shaft comprising a shaft-engaging first output shaft end, a shaft-engaging second output shaft end, a rotation receptive portion, and an output axis of rotation, the rotation receptive portion extending intermediate the first and second output shaft ends, the annular member comprising an inner diameter, an outer diameter, and a plurality of rod-receiving tunnels extending intermediate the inner and outer diameter, the annular member receiving the rotation receptive portion at the inner diameter and being fixedly attached thereto, the rod-receiving tunnels being parallel to the output axis of rotation, the first output shaft end being rotatively mated with the second input shaft end, the output and input axes of rotation being coaxial, the input and output shafts being independently rotatable, the rod-receiving tunnels being rotatable about the output axis of rotation; and

a rod-translation system, the rod-translation system comprising a plurality of rods, a plurality of thrust bearings, and fixed rod-translating means, the rods being received in the rod-receiving tunnels and each comprising an arm-engaging first rod end and a bearing-engaging second rod end, the second rod ends being cooperatively associated with the bearing means, the rod-translating means for selectively translating the bearing means and rods intermediate an arm-engaged position and an arm-disengaged position, the first rod ends engaging the output arm end when in the arm-engaged position for imparting rotational movement from the output arm end to the output shaft by way of the annular member, the bearing means enabling rotational movement of the output shaft relative to the rod-translating means, the transmission assembly thus for transmitting rotational movement from the input shaft to the output shaft.