conjunction to change the direction of motion of the first piston 7 a and the piston 7 b it will be obvious that the stroke length can be altered to suit the characteristics required by the equipment the motor is to power similarly a number of motors could be arranged in gangs to provide power in small diameter settings while particularly well suited to be deployed downhole in a well to power a reciprocating pump with a pump chamber at either or both ends of the motor it is apparent that the motor may be used in other settings to power other equipment power fluids can be any one or more of a variety of suitable fluids including for example liquids or gases of suitable compressibility to transfer fluid flow at pressures and volumes sufficient to power the motor in operation remotely from the pressurized fluid 39 s source additionally the invention provides that the working chambers of the pistons and cylinders of the motor may always be kept at higher pressures than the motor 39 s environment thus isolating the motor 39 s moving parts within an environment provided by the power fluid which can be significantly cleaner and qualitatively controlled than the motor 39 s external environment seals if any between the moving components of the motor are similarly operative in a controlled environment with higher pressure on the same side of each seal between the motor and its environment the motor 39 s side during all strokes with any leakage essentially flushing the seals 39 path of motion it is to be noted that alterations to the diameter of the connecting rod the exposed surface areas of the sleeve and spool and the hydraulically active surface areas of the various position and balancing pistons and.