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Load Inertia - Mass Moment of Inertia Question

by mselak500
Tags: inertia, load, mass, moment
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Nov12-08, 10:17 AM
P: 9
I'm looking for some help to verify a calcualtion that was made by a previous employee.

The calcualtion was for load inetria (reflected to the motor). The motor will be driving (3) rollers at a gear ratio of 3.5:1 (motor turns 3.5 revolutions for every 1 revolution of the rolls).

I have a program that caluclates the mass moment of inertia for the rolls, and was able to verify this calucations with formulas that I found on the internet. The total inertia for all (3) rolls is 67,155 lbm-in^2. I converted this to 19.65 kg-m^2. If I divide this by the gear ratio of 3.5, I come up with 5.6 kg-m^2.

The previous employee came up with 2.4 kg-m^2.

Can someone help to tell me what I'm doing wrong.


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Nov17-08, 11:31 AM
P: 2
Take a look below to see if any of these equations are useful. The reflected inertia is the (load inertia) / (gearing ratio^2).

I came up with 1.604 kg-m^2. Let me know if you want me to run it through my simulator. Note: I didn't include the gearing inertia - should be minor if you're using a belt system.
Nov17-08, 01:01 PM
P: 9
I'm assuming the 50% saftey factor. Thanks much your all the help.

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