Moment of Intertia for changing COG

[r00bin]

Hi all,

I've got a 3d object modeled in Pro/Engineer with a tail. The tail can change position to some angle theta with respect to the ground.

I have created a closed form solution to determine the location of the center of gravity at any angle theta.

The problem is with the moment of inertia. From Pro/Engineer, I can numerically determine the moment of inertia about the vertical axis at the center of gravity.

Is there anyway to express the moment of inertia about the vertical axis as a function of the center of gravity location?

Thanks!

 

[Curl]

Yes. The inertia of the body (without tail) is fixed. Then all you need to do is find out the inertia of the tail about the vertical axis as a function of angle. You can easily relate the angle to the change in CG.

Won't be a trivial calculation unless the tail is some sort of elementary shape.