Calculations

How to Select the Right Air Motor

1. Determine the required:

   Torque          [ft lb]

   rotation speed  [RPM]

   Power  [HP]

   If one of the 3 parameters isn’t available,,, calculate it:

   HP = T x RPM / 5252

   T = HP x 5252 / RPM

   RPM = HP x 5252 / T

2. Determine the available airline pressure. (If unknown, calculate with 90 psi)
3. Does the motor need to start under load or not?
   

   Examples of applications starting under load: hoist, winch and conveyor belt.

   Examples of applications starting with no load: fans, pumps and mixers.

   Starting under load: calculate with the minimal starting torque to insure sufficient torque at start-up

4. Select a gearbox if necessary

   Example:

   Required drive torque: 150 ft lb

   Available torque air motor: 10 ft lb

   Efficiency of gearbox:

         Spur gears: 90 – 95%

         Worm gears: 10 – 60%

   Reduction is: 150/(10 x 0.9) = 16.7:1 ratio

(ref. air motor resource)