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Load Inertia - Mass Moment of Inertia Question

  1. Nov 12, 2008 #1
    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.


  2. jcsd
  3. Nov 17, 2008 #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.

    http://www.danahermotion.com/website/com/eng/download/document/sizinggearheads.pdf [Broken]
    Last edited by a moderator: May 3, 2017
  4. Nov 17, 2008 #3
    I'm assuming the 50% saftey factor. Thanks much your all the help.
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