All hydraulic motors convert hydraulic energy into mechanical energy. This is done via a rotating shaft which uses flow and hydraulic pressure to create rotation and torque.


There are some design features which are common to all types of hydraulic motor. These are:


1. A mechanical connection between output shaft and surface area;

2. A driving surface area that is subject to pressure differential;

3. A method of timing the porting of pressure fluid to pressure surface.


The maximum performance of a hydraulic motor in terms of flow, torque, output and speed will depend on the following factors:


1. How efficiently the output shaft and pressured surface are linked;

2. The amount of force the motor’s pressure surfaces can withstand;

3. Its leakage characteristics.


Hydraulic Motor Displacement

The motor displacement refers to the volume of fluid needed to turn the output shaft a single revolution. Motor displacement is measured in inches or centimetres cubed.

Both fixed and variable displacement motors are available. The fixed variety provides constant torque, while the variable variety can provide both varied speed and torque.


Applications of Hydraulic Motors

Hydraulic motors are used to power many items, including cranes, winches, roll mills, agitator drives, mixed drives and excavators.


Hydraulic Motor Types

There are three main types of hydraulic motor. These are the piston, gear and vane. Each main motor type has one or more sub-types.

The power output of all hydraulic motors is directly proportional to motor speed. Power is determined by the motor’s pressure drop and flow.


Piston Motors

The piston motor combines high speed with high operating pressure and large volume displacement. Applications requiring a large amount of power are most suited to the hydraulic piston motor. The axial piston motor uses a swash place or bent axis design, and is available in fixed and variable types. The fixed displacement type works as a hydraulic motor, where the variable variety works most often as a hydraulic pump.

Piston motors can displace liquid from 10 to 1,000 cc, and operate at a maximum pressure of 450 bar. Speeds can reach 11, 000 rpm, whilst maximum torque can reach over 10,000 Nm.


Gear Motors

The gear motor is available in two sub-types, which are the gear and epicyclic gear. The former operates at high speed, while the latter operates at slower speeds. Gear motors are low in size and weight, but offer high pressure in a wide range of speeds at low cost. They are also of durable design and can handle a wide range of viscosities.

Gear motors can reach a maximum torque of up to 400 Nm, with displacement volume from 3 to 100cc. Their maximum pressure can reach 250 bar, with speeds ranging from 500 to 4,000 rpm. The epicyclic variety itself comes in two types, which are Cardan shaft or central shaft.


Vane Motors

Vane motors offer high torque at low speeds, as well as low noise levels. They also feature low flow pulsation and are very suitable for vertical installations. Their simple design offers easy serviceability.

Only when the vanes of the rotor are pressed against the inside of motor housing can a vane motor operate correctly. Leaf or spiral springs usually ensure the vanes are pressed against the housing, but rods can also be used to accomplish this. The fact that most rotors in vane motors are hollow is what allows them to be easily mounted onto spline shafts. Vane motors can offer up to 650 Nm of torque, with maximum pressure reaching up to 230 bar. They also have displacement volume of up to 214 cc.


Let Us Help You..

Choosing a supplier with a substantial inventory of hydraulic motors is favourable. It is also a benefit to have a supplier that has the knowledge to take a wide variety of system requirements into account, this is where BSCL step in. Give us a call on 01922 646 716 or email us at