# torque calculation

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#### SmittyMcSmith

##### Guest
I'm trying to calculate the torque of my model so i can correctly spec a motor to rotate it. As we all know, t=Ia where 't' is torque, 'I' is moment of inertia, and 'a' is the angular acceleration.

The mass is going inside a torque motor... think of the motor as a donut and the mass as a munchkin spinning in the middle, however the mass is not symmetric.

Center of mass: ( millimeters )
X = 0.1283
Y = 3.6911
Z = 0.4753

I have centered the model such that it will rotate at the output coordinate system about the Y axis like it would in real life.

Moments of inertia: ( grams * square millimeters )
Taken at the center of mass and aligned with the output coordinate system.
Lxx = 9009.2180 Lxy = 116.3216 Lxz = -179.7757
Lyx = 116.3216 Lyy = 9102.2187 Lyz = 86.0433
Lzx = -179.7757 Lzy = 86.0433 Lzz = 10804.8404

What values do I use to calculate the torque?! What is their naming convention for their variables?!

NOTE: The velocity is going to be 120 RPM, but I haven't yet figured out the actual acceleration.

#### gwinslow

##### New member
Use the center of mass if it's only for the rotating part.
Quick math puts your CG ~.483 off axis, so now you have mass & radius