Moment Units-Force To Turn

[KLineDesign]

I was tasked with finding the value required to turn something. I selected materials for all of the components in question and found the moment of inertia. The axis this will be spinning on is Z, now I just need to know which value is the value I am looking for. Is it 'Iz' or 'Ixy' (or something else), and are the units indeed:

Moment; PoundForceInch; lbf-in; pound force-inches

...If I had selected lb-in as my units?

It seems like the Mass Moment of Inertia is really what I am after, and I can find the units exist for it, but how do I force NX7.5 to show me THIS value?

Not to often I have do anything beyond finding the center of mass (in this realm), so go easy on the terminology.

Thanks,
KLINE

 

[cowski]

If your WCS is set up so the Z axis is the axis of rotation, you are looking for 'Moments of Inertia (WCS)'. Izc will be the last number in the list. The moment of inertia has units mass*length^2.

This number by itself won't tell you how much force you need to turn something. F=ma; to find the force you will need to know what angular acceleration you want (ignoring friction).

 

[cowski]

Oops, F=ma is the linear equation. I should have used the rotational equation T=I*alpha (Torque = Inertia * rotational acceleration).

 

[KLineDesign]

Thanks cowski, I believe this gets me where I need to be. Could you breakdown the 'measures' in NX a bit more for me though? It doesn't seem real straight-forward correlating to the units (with First Moment and Moments).

I kind of think the Moments of Inertia listed in the information window are indeed Mass Moments of Inerita with the Unit Name PoundMassInchSquared (Display Name: lbm-in^2) as you specified. Is this correct? It would be nice if they read 'Mass' somewhere in the name.

I believe this is the only number I must specify. Thanks again.

Regards,
KLINE