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Detailed Introduction on Piston Motor

By Emma | Published on Dec 10,2015

Brief introduction

Piston motors are applied to drive mobile and construction equipment, winches, ship-cranes, and all kinds of heavy-duty equipment for offshore and onshore operations.

Piston motors combine high speeds with large displacement volumes at higher operating pressures. If your operation asks for a significant amount of power, a piston motor is your best option. Whether your heavy-duty installation needs high torques or high speeds determines the choice of either a radial piston or axial piston motor.

Multi-stroke piston motors increase displacement substantially because each piston carries out multiple strokes per revolution of the shaft. Hence, a hydraulic multi-stroke piston motor produces high operating torques.


The piston motor can be divided into two main categories: axial piston motor and radial piston motor. We will detailedly introduce them to you.

1. Axial Piston Motor

Similar to piston pumps, axial piston motors work with a bent axis design or swash plate principle. The fixed displacement type works as a hydraulic motor, and the variable displacement type most often functions as a hydraulic pump. Fixed displacement motors may be used in both open and closed loop circuits.

In the bent axis design, pistons move up and down within the cylinder block bores. This motion is converted into rotary movement via the piston ball joint at the drive flange. In the swash plate design, pistons move up and down within the cylinder block and turn it, which then turns the drive shaft via the connected cotter pin.

Typical parameters of axial piston motors:

Displacement volume: 10 to 1,000 cc (multi-stroke up to 1,500 cc)

Maximum pressure: up to 450 bar

Speed range: 500 to 11,000 rpm

Maximum torque: up to 10,750 Nm

2. Radial Piston Motor

Radial piston motors are used in caterpillar drives of dragline excavators, cranes, winches and ground drilling equipment. Radial piston motors are capable of producing high torques at very low speeds, down to half a revolution per minute. Therefore, radial piston motors are also referred to as Low Speed High Torque (LSHT) motors.

The pistons (or plungers) of a radial piston motor form a star-like shape and are perpendicularly connected to the shaft. The rectilinear motion of the pistons is transformed into a rotating movement by the eccentric shaft.

Typical parameters of radial piston motors:

Displacement volume: 10 to 8,500 cc

Maximum pressure: up to 300 bar (multi-stroke up to 450 bar)

Range of speeds: 0.5 to 2,000 rpm

Maximum torque: up to 32,000 Nm (multi-stroke up to 45,000 Nm)

Working Principle

To help readers simply and visually understand the working principles of the piston motor, we select a video below. This video can detailedly describe how piston motors work.

Video: https://www.youtube.com/watch?v=1FpT9Z4at-w


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