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Hydraulic Motor Essentials

Understanding the basics of your hydraulic motor is absolutely essential when it comes to making the most of your hydraulic system. As one of the most important parts of your entire system, getting to grips with your hydraulic motor is the key to understanding your entire hydraulic system.

Hydraulic motors all share the same operation principles, so as soon as you understand one, you’ll understand how they all work. The first step to knowing how your hydraulics work is learning what they all have in common.

The Common Features Of All Hydraulic Motors

All kinds of motors for hydraulic systems have the same features. These include:

· A driving surface area, which is subject to pressure differentials.

· A way of timing the porting of pressure fluid to the surface through continuous rotation.

  • A mechanical connection between the surface area
  • An output shaft.

The variations of these basic components are what enable different motors to offer different levels of service. Just some of the features that different sized parts of the motor can affect include the pressure, flow, torque output, service life, speed and the overall efficiency of the hydraulic motor itself.

Essential Terms To Understand About Your Hydraulic Motor

There are a variety of different terms that you will need to understand if you’re ever going to know how your hydraulic motor works. Some of them are quite simple, whereas others can seem complex at first.

  • Motor-Displacement – This term refers to the volume of fluid that is required to turn the hydraulic motor’s output shaft. Commonly, this variable is measured in cm3 or in.3 per revolution. The displacement of these motors may be either fixed or variable.

    With fixed-displacement motors, you’ll be able to make the most of constant torque. In these models, speed is varied by controlling the amount of fluid that flows into the hydraulic motor itself.

    Variable displacement motors provides variable torque as well as aped. The input flow and pressure is kept constant and the torque speed ratio can be varied to meet the varying load requirements.
  • Torque Output – This metric is measured in inch-pounds or foot-pounds. As a function of system pressure and motor displacement, the ratings for these components are usually given for a specific pressure drop across the entire hydraulic motor. The torque is measured with the assumption that there is no mechanical loss.
  • Running Torque – This term can refer to either the load of the motor or the motor itself. When it refers to a specific load, it indicates the torque necessary to keep the load turning. When it refers to the hydraulic motor, running torque indicates the actual torque a motor can develop to keep a load on the move.

    This metric considers a hydraulic motor’s inefficiency and is a percentage of the theoretical torque. This typically comes out at around 90% of the theoretical number.
  • Starting Torque – This refers to the capacity of a hydraulic motor to start a load. Simply, it indicates how much torque will be required to start a load turning using the motor.
  • Torque Ripple – This is the difference between the minimum and maximum torque that is delivered at a given pressure during one revolution of the motor.
  • Mechanical Efficiency – This means the ratio of actual torque delivered as compared to theoretical torque.
  • Motor Speed – The motor speed is a function of motor displacement and the volume of fluid delivered to the hydraulic motor. It is also worth understanding the maximum and minimum motor speed for your component.

    As you can probably guess, the maximum is the highest speed at which the motor can sustain itself for a limited time. It’s worth noting that this metric can change depending on the inlet pressure. The minimum is the slowest, continuous and uninterrupted rotational speed that the motor shaft can provide.
  • Slippage – This is the leakage of hydraulic fluid through the motor. It could also mean the fluid that passes through the motor itself without actually performing any work.

For High-Powered, Durable Hydraulic Motors, Shop With Flowfit Today

At Flowfit, we are dedicated to providing only the highest-quality components for your hydraulic system. So long as you understand the various terms and metrics of your hydraulic motor, you’ll be able to find the perfect model for your system’s requirements.

For more information, don’t hesitate to get in touch with our team of hydraulic experts today on 01584 876 033. You can also reach us via our email at and we’ll get back to you as soon as we can.

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