Abstract: A linear motion power cylinder utilizing a rotor with radially movable impeller vanes rotatably mounted within a cylinder having an eccentric bore, the chamber created between the rotor and cylinder being accessible by two ports, with one port located adjacent to each end of the cylinder. Fluid pressure within the chamber imparts a force on the impeller vanes which in turn drives the rotor. The rotation of the rotor is transferred through a system of planetary gears to a power screw which passes through the center of the rotor. This rotary motion is translated into linear motion by a threaded cylinder rod threadedly engaged with the power screw. The cylinder rod may be moved reciprocally in and out of the linear motion power cylinder increments by reversing the direction of the fluid flow into the cylinder chamber.