Air Motor Types

• Air motors are commonly used in applications requiring high- and low-power outputs. The motors provide a continuous rotary source of power coming from a compressed air system. These motors feature several advantages, including that they can be used in volatile atmospheres because they do not require electrical power. They also generate much less heat than electric motors. It is a popular belief that because of their toughness and versatility, air motors can be the perfect power source for industrial applications. The three most common types of air motors are vane, turbine and piston.

Vane Motors

• Vane motors are also rotary, using axial vanes fitted into slots running throughout the length of the motor. Depending on the type of vane motor, the vanes seal interior chambers through springs, cam action or air pressure. The pressure resulting from the compressed air in the chambers allows the vanes to rotate, turning the motor so the air moves from one chamber to another.

  These types of air motors are generally used in applications requiring low- to medium-power outputs such as portable power tools. They are available with three to 10 vanes, where increasing the number of vanes reduces the chances of internal leakage and blow-by. This makes the motor torque output reliable at lower speeds and uniform throughout the motor. At the same time, more vanes can increase the friction and cost of the motor.

Turbine Motors

• Turbine motors operate with a nozzle guiding air into a turbine wheel made from a rotor with curved blades. The rotor is set in motion when the air comes through the nuzzle and hits the blades. The amount of horsepower can easily be modified by limiting the air flow through the motor. Turbine motors are generally used in low-pressure, high-velocity tools like dental drills.

  Their efficiency is higher than other air motors as the sliding contact of parts does not cause internal friction, thus there is no need for constant use of lubricating oil. The absence of lubrication improves the performance of the turbine motors in cold weather. They also require little maintenance, are compact and light for the power-delivery capability.

Piston Motors

• Piston motors are commonly used in high-power machines requiring a high-starting torque. They are composed of two to six cylinders housing pistons arranged in either a radial or axial fashion, allowing air to move into the cylinders. Air pressure causes the pistons to slide outward, making the cylinders rotate. The end result creates the torque turning the motor.

  Motors with four or more cylinders result in smooth torque at a given operating speed as the power pulses overlap. Though they provide better torque, there is a greater chance that motors with two or more pistons undergo a power stroke at any time during a revolution. Despite all their advantages, piston motors have one significant limitation concerning their maintenance. They are internally oil lubricated, thus oil supplies must be constantly checked and replenished.