Used Hydraulic Motor for Construction Equipment

What is the difference between a hydraulic pump and motor?

Although their internal design may appear similar, pumps and motors serve opposite functions within the hydraulic circuit. The hydraulic pump, driven by the machine's combustion engine, draws oil from the reservoir to generate a pressurized fluid. Conversely, the motor receives this fluid to produce movement. In essence, the pump converts mechanical energy into hydraulic energy in the form of fluid flow, while the motor reverses the process to drive the motor shaft.

Hydraulic motor operation and schematic

Operation relies on the flow of pressurized fluid entering the motor chambers. This pressure exerts force on internal moving components—such as pistons, gears, or vanes—resulting in the rotation of the motor shaft.

For heavy machinery, axial piston motors are primarily used. In this setup, pistons are aligned with the output shaft and push against a swashplate. When pressurized oil enters the cylinder block, it forces the pistons against the plate, generating the required torque. This type of hydraulic motor is favored for its durability and ability to withstand high operating pressures, often up to 350 or 450 bars in modern machines.

How to choose your hydraulic motor?

The choice of motor primarily depends on the application (translation, rotation, or equipment) and your machine's hydraulic specifications. It is essential to match the original displacement to avoid upsetting the circuit. A poor pairing can cause overheating or premature wear of the main pump.

Slow or fast motor: displacement and torque

There are three main categories based on rotational speed and required torque:

• Fast motor: Often axial piston or gear types, these provide high speed but lower torque. They are ideal for fans or certain hydrostatic transmissions.
• Semi-fast motor: Generally orbital motors, offering an ideal compromise for auxiliary equipment.
• Slow motor: Motors like the Used Poclain Hydraulic Motor are designed to deliver high torque at very low speeds. They are essential for moving heavy tracked machines where traction force is prioritized over speed.

Coupling, mini excavator, bucket: what application?

Usage determines the technology to prioritize:

• Used travel motor: To ensure the movement of tracks or wheels. On a mini excavator hydraulic motor, these are often integrated into compact gearmotors.
• Hydraulic rotation motor: Used for turret rotation on excavators from 1.5 to 50 tons. You can find a Used Swing Motor compatible with brands such as Caterpillar, Case, or Doosan.
• Hydraulic bucket motor: For tipping systems or screw conveyors on trucks and trailers. In these cases, a gear motor is often sufficient and cost-effective.

What is the power of a hydraulic motor?

The power of a hydraulic motor (expressed in kW or horsepower) is the product of the flow it receives and the pressure difference between inlet and outlet. "Input power" refers to hydraulic flow power, while "output power" is the actual mechanical force available at the shaft.

For construction equipment, power can range from a few kilowatts for small rotary units up to over 350 kW for mining excavator transmissions. A key factor is the volumetric efficiency, measuring the motor’s effectiveness considering internal leaks necessary for lubrication. When replacing, ensure the motor can handle the maximum power supplied by your hydraulic system.

How to test a hydraulic motor?

Before returning to service, a used motor must be inspected. The main test is conducted on a hydraulic test bench to measure:

1. Drainage (internal leakage): Excessive drainage flow indicates worn distribution valves or pistons, leading to reduced efficiency.
2. Starting torque: Verifying the motor develops sufficient force at initial pressure.
3. External tightness: Checking shaft seals and joint surfaces.

At Codimatra, every used travel motor and used swing motor is rigorously inspected by our expert technicians to ensure a ready-to-use part capable of withstanding the demanding conditions of earthmoving and demolition.