How to Calculate Load Inertia

By Matthew Weeks
Load inertia of a mechanical system is a function of the weight of the load and the radius of the cylinder.
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In mechanical engineering terms, knowing how to calculate the load inertia of a mechanical system is very important. It is a measurement of the resistance of the load being moved to acceleration or deceleration, and is therefore used to determine the requirements of the motor that will provide the necessary torque to drive the system. Fortunately, if you measure the weight of the load being moved and the outer radius of the cylinder being used to move it, you can easily calculate load inertia.

Weigh the load being moved on your scale. As an example, assume a weight of 10 lbs.

Measure the outer radius of the cylinder being used to move the load with your tape measure. The radius will be equal to one-half of its diameter. Be sure that you measure in inches. For the above example, assume a radius of 5 inches.

Square the value of the radius of the cylinder. For the above example, 5 * 5 = 25.

Multiply your result from Step 3 by the weight measured in Step 1. For the above example, 25 * 10 = 250.

Divide your result from Step 4 by the gravitational constant of 386 inches/second-squared to get the load inertia of your system. For the above example, 250/386 = a load inertia of 0.648 lb-in.-seconds^2.

About the Author

Matthew Weeks has been a public policy and technology writer since 2003. He has been published on Men's News Daily and Free Republic. Weeks holds a bachelor's degree in political science from the College of New Jersey and a master's degree in public policy from Rutgers.