Finding the Perfect Fit: Determining Displacement for Hydraulic Motors

To determine the right displacement for your hydraulic motor, you’ll need a few application details—mainly the torque requirement and the operating pressure. Use the steps below to estimate a suitable displacement and then confirm against manufacturer specifications.

1) Understand displacement

Displacement refers to the volume of hydraulic fluid displaced by the motor in one complete revolution. It’s typically expressed in cubic centimetres (cc) or cubic inches (in³).

What displacement affects

Higher displacement motors generally produce more torque at lower speeds, while lower displacement motors are better suited to higher speeds (assuming the same pressure and flow).

2) Gather the required parameters

Torque (T): Determine the torque required for your application (Nm or lb-ft).
Operating pressure (P): Identify the maximum operating pressure of your hydraulic system (bar or psi).

3) Use the formula

The relationship between torque, pressure, and displacement can be expressed using a standard torque equation. In your notes:

T = Torque (in Nm)
P = Pressure (in bar) × 100,000 (to convert to pascals)
D = Displacement (in m³/rev) or (in cc/rev)

Rearranging the formula to solve for displacement gives you:

Finding the Perfect Fit: Determining Displacement for Hydraulic Motors — Displacement can be calculated from required torque and available system pressure.

Unit tip

Keep units consistent (Nm + bar, or convert to SI units) before calculating. If you’re unsure, ask for help converting units so the result is accurate.

4) Calculate displacement

Plug the values for torque and pressure into the formula to find the required displacement.

5) Consider motor speed

Consider the speed at which the motor will operate. Higher displacement motors can deliver more torque at lower speeds, while lower displacement motors are better suited for higher speeds.

6) Check manufacturer specifications

Review technical specifications provided by motor manufacturers to ensure the selected displacement aligns with your application requirements.

7) Consult with experts

If you are unsure, consulting with hydraulic system experts or manufacturers can help you select the right displacement based on your specific application needs.

Flowfit: a one-stop shop for hydraulic motors

Our selection of hydraulic gear motors is designed to deliver high-quality models tailored to your requirements. With reliable performance and consistent build quality, you can trust that any motor you buy from us will meet—or even surpass—your expectations.

Contact us today to speak with one of our hydraulic specialists and explore your options. You can also shop for hydraulic motors directly through our website.