Air motor or electric motor: speed, torque, air consumption

Otherwise an electric motor is usually the simplest choice, because an air motor needs a compressor that supplies all the air it uses.

Gast's air motors are vane motors. The compressed air pushes the vanes out from an eccentrically mounted rotor, and the rotor drives the shaft.

What an air motor does better

Gast states the following about its air motors:

• No electrical components, and therefore no electrical sparks
• Instant start, stop and reverse with little shock on the reversible RV models
• Variable speed
• Runs cool and can be mounted in any position
• Ambient temperature from +1 to +120 °C and relative humidity from 0 to 100%
• Mounting by hub, foot, face, NEMA C-flange or metric D
• Corrosion-resistant air motors are available in the NL22, NL32 and NL42 series

Potentially explosive atmospheres

Gast describes the motors as suitable for potentially explosive atmospheres. The data sheets state conformity with EN 13463-1 for non-electrical equipment, group II category 2 for gas and dust, with a surface temperature of 135 °C.

Note that the ambient temperature in potentially explosive atmospheres is given as +1 to +40 °C, compared with +1 to +120 °C otherwise. The classification of your area should be clarified before the motor is chosen.

The series: power, speed and torque

The oil-lubricated AM series ranges from 0.9 to 33.1 kg. Max. operating pressure is 7 bar, except for the 1UP at 5.6 bar. The figures are power, max. speed, max. torque and max. air consumption:

• 1AM — 0.30 kW, 10 000 rpm, 0.63 Nm, 34.83 m³/h
• 1UP — 0.33 kW, 6 000 rpm, 0.68 Nm, 45.87 m³/h
• 2AM — 0.95 hp (approx. 0.7 kW), 3 000 rpm, 3.1 Nm, 50.97 m³/h
• 4AM — 1.25 kW, 3 000 rpm, 6.33 Nm, 132.52 m³/h
• 6AM — 3.0 kW, 3 000 rpm, 13 Nm, 217.47 m³/h
• 8AM — 4.0 kW, 2 500 rpm, 20.91 Nm, 297.33 m³/h
• 16AM — 6.7 kW, 2 000 rpm, 42.04 Nm, 467.23 m³/h

Air consumption is the deciding factor

An air motor is only as good as the air it gets. Even the smallest, the 1AM, has a max. air consumption of 20.5 CFM. That is more than any of Gast's oil-free piston compressors (up to 11 cfm) or rocking piston compressors (up to 12 cfm) are rated to deliver.

The motor uses less air at lower speed and lower pressure, but plan for how it will actually be used. If it gets too little air or too low a pressure, both speed and torque drop.

Nor are air motors quiet. The stated sound level ranges from 76 dB(A) on the 2AM to 113 dB(A) on the 16AM.

Low speed and high torque: gear motor

The small air motors run fast but have little torque at the shaft: the 1AM gives 0.63 Nm. If such a motor is to drive a mixer, a conveyor belt or a winch, a gearbox is usually needed. Gast's gear motors are based on the 1AM, 1UP and 4AM, are available in right-angle and in-line versions, and the gear motor range goes up to 190 Nm. Selected models, with gear ratio, max. speed and max. torque:

• 1AM-GR11 — 15:1, 350 rpm, 8.14 Nm
• 1UP-GR11 — 15:1, 400 rpm, 10.74 Nm
• 4AM-RV-75-GR20 — 10:1, 300 rpm, 48 Nm
• 4AM-RV-75-GR25 — 15:1, 200 rpm, 72.3 Nm
• 4AM-70C-CB60 — 60:1, 50 rpm

When an electric motor is the right choice

If the motor runs steadily, in dry surroundings, with no spark hazard and without frequent starts and stops, an electric motor is usually the simplest choice. It only needs electricity. An air motor needs a compressed air system sized for it.

When you contact us

To suggest a motor, we need the following:

• What the motor will drive, and what speed and torque are needed at the shaft
• Whether it will run continuously or for short periods
• What pressure and how much air are available
• The environment: explosion hazard, temperature, moisture or corrosion
• Mounting and direction of rotation — clockwise, anticlockwise or reversible