What exactly are Hydraulic Motors?
Hydraulic motors are rotary actuators that convert hydraulic, or liquid energy into mechanical power. They function in tandem with a hydraulic pump, which converts mechanical power into fluid, or hydraulic power. Hydraulic motors supply the force and offer the motion to go an external load.
Three common types of hydraulic motors are utilized most often today-gear, vane and piston motors-with a number of styles available among them. In addition, other varieties exist that are much less commonly used, which includes gerotor or gerolor (orbital or roller star) motors.
Hydraulic motors could be either set- or variable-displacement, and operate either bi-directionally or uni-directionally. Fixed-displacement motors drive a load at a continuous speed while a continuous input flow is offered. Variable-displacement motors can offer varying flow rates by changing the displacement. Fixed-displacement motors provide continuous torque; variable-displacement designs provide variable torque and speed.
Torque, or 
the turning and twisting effort of the force of the engine, is usually expressed in in.-lb or ft-lb (Nm). Three different types of torque exist. Breakaway torque is generally used to define the minimal torque required to begin a motor with no load. This torque is based on the inner friction in the engine and describes the initial “breakaway” push required to begin the engine. Running torque generates enough torque to keep the motor or motor and load running. Beginning torque is the minimal torque required to start a engine under load and is certainly a mixture of energy required to overcome the pressure of the strain and internal engine friction. The ratio of actual torque to theoretical torque gives you the mechanical effectiveness of a hydraulic engine.
Defining a hydraulic motor’s internal volume is done simply by looking at its displacement, hence the oil volume that is introduced in to the motor during a single output shaft revolution, in either in.3/rev or cc/rev, is the motor’s volume. This is often calculated by adding the volumes of the motor chambers or by rotating the motor’s shaft one switch and collecting the essential oil manually, then measuring it.