Moment of Inertia - armature

[bernardg]

Hello All,

We make 3.0" DC motors... and for some blower applications, we mount the wheels to the shaft and assemble the motor-wheel into blower housings.
Because of the tight clearance that we maintain between the wheel and the housing... even when the motor shaft flexes a little due to the armature imbalance, the wheels start to hit the housing and damages it.

Our customer wanted us to find the moment of interia of the armature. (Not the moment of interia of the armature while it is running in the motor... but just the armature as is). How would I do that?

Your input would very much be appreciated.

Thanks,
Bernie

 

[tygerdawg]

The formulas for mass moment of inertia "primitives" such as cylinders can be found in Machinery's Handbook, any Dynamics or Engineering Mechanics textbook, etc. You can measure the dimensions of the armature and weigh it, then calculate the mass moment of inertia within a few percent error. Be sure to mind your units and axes of rotation.

To get a more accurate estimate, you may want to disassemble into consituent components and measure/weigh each, then calculate the inertia and sum them.

Or, if the armature is designed in modern CAD programs, you can probably assign mass properties values to the constituent components and let the CAD program calculate it for you.

TygerDawg

 

[GregLocock]

You can find the polar moment of inertia of a component by using a trifilar pendulum.



Cheers

Greg Locock

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