Abstract: The present invention comprises a fluid pump motor unit and a controller unit which controls the output of the pump/motor irrespective of the speed of the power source driving the pump/motor unit.The pump/motor unit comprises a cylindrical housing within which there is arranged at least one rectangular expansible cylinder assembly mounted on a crankshaft in a radial pattern, the cylindrical assembly being pivotally mounted within the housing for movement about trunnions, the rectangularly adapted piston assembly within said housing being journaled on a crankshaft which crankshaft with respect to the centerline of the cylindrical housing has a rotation parallel to, but spaced from, the centerline of the housing. The pivotal oscillation of each cylinder assembly alternately opens a port for the inflow of a fluid and subsequently closes that port while simultaneously opening another port for the outward flow of the fluid under compression as the piston moves toward the top of the chambers.