Moment of inertia - system of bodies

[Christopher Karras]

Hello,

I have a question concerning moment of inertia (kg*m^2) of a system of bodies. As seen in the picture attached, I am dealing with a crank/con rod mechanism that operates by applying a moment via. motor about the crank centerline (crank is on top in this application). The crank moves vertically while the long con rod just pivots. The range of motion is just 0 to 180 degrees.

What I need to do is calculate the moment of inertia of the system with respect to the crank centerline throughout the range of motion of the system. I am using NX9 with limited license capability, so hopefully I am able to do it. I already have the assembly constrained in the assembly such that I just have to adjust an angle constraint and the whole assembly moves accordingly. I am having a hard time because I don't know how to find the inertia with respect to the constraints + gravity/orientation

Thoughts?
Thank you

 

[BubbaK]

First of all, gravity doesn't affect moments of inertia, does it (if I remember my high-school physics correctly).

Generally, I think NX will report moments relative to the WCS axes. So, set the WCS to have its Z-axis along the centerline of your crank, and NX should give you the answer you want.