The Typical Pneumatic Motor

The pneumatic motor is an actuator that converts compressed air flow into rotary motion. It is used in applications where low force rotary output is needed. Examples include pneumatic drills, mixing motors, and small winches.

Below is a picture of a typical pneumatic motor:

Pneumatic motors operate by using air pressure to create a turning force called "torque" at the motor shaft. Once the resisting torque of the load at the motor shaft is overcome, the shaft starts to rotate. Any additional air pressure needed to start the rotation beyond that determines the speed (rpm) of the motor.

Below is how an air motor is typically put together:

Parker Hannifin Corporation. (1980). Industrial Pneumatic Technology. Parker Hannifin Corp. DOI: 1557690154

Unidirectional and Bidirectional

Most pneumatic motors are made to turn in only one direction. These are called unidirectional. Pneumatic motors that rotate in either direction are also available and are called bidirectional.

Below are the schematic symbols for air motors:

Parker Hannifin Corporation. (1980). Industrial Pneumatic Technology. Parker Hannifin Corp. DOI: 1557690154

The triangles that are inside the circles are hollow. This indicates that the medium that is flowing is gas. Also, they are pointed inward, indicating that the air flows into the motor. One triangle indicates unidirectional; two triangles indicate bidirectional.

A unidirectional motor can create a considerable amount of noise when the air is exhausted from the exhaust port. To reduce the noise, mufflers, sometimes called silencers, are placed in the exhaust port to reduce the noise levels. Below is a diagram of an air motor with an exhaust muffler.

Parker Hannifin Corporation. (1980). Industrial Pneumatic Technology. Parker Hannifin Corp. DOI: 1557690154

Here is the schematic symbol for a muffler:

Parker Hannifin Corporation. (1980). Industrial Pneumatic Technology. Parker Hannifin Corp. DOI: 1557690154

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