Gear Drive Motor Mass Moment of Inertia Equation

Gear Drive Motor Mass Moment of Inertia Equation:

Use these equations and calculator to determine the Inertia of a gear drive system. For any change in rotation speed, the load inertia will reflect back through the gears to the motor.

Gear Drive System


Motor Speed


Motor Torque:

Reflected Load Inertia

Total Inertia realized at Motor:


Sm Motor Speed, rpm
Sl =   Load Speed, rpm
Nl =   Number teeth on load gear
Nm Number teeth on motor gear
N =   Gear Ratio
Tm Torque of Motor, lb-in
Tl Torque of Load, lb-in
e =  Efficiency
Jl  Load Inertia, lb-in.-sec2
Jm = Drive Motor Inertia, lb-in.-sec2
Jr = Reflected Load inertia, lb-in.-sec2
Jt = Total Inertia, lb-in.-sec2

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