moment of inertia - assembly vs. part files

[Bill Metz]

Hi,

I am finding a few problems while using Inventor 4.0 when I am calculating
moments of inertia for parts in an assembly file. Inventor seems to handle
solving the total assembly moment of inertia but has problems calculating
individual part moments of inertia based on the assembly x,y,z axes. When
selecting one part in an assembly file and right clicking to the property
tab, Inventor solves for moment of inertia for the part as it resides in the
part file not in the assembly file. Any ideas on how I might calculate
individual part moments of inertia based on the assembly environment it is
placed?

Bill metz
bm...@shot.com

[Stefan Tondl]

make a derived part of the assy.
get only the part you want into the derived
then it should work (haven't tried it yet)

Stefan

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[Patrick Berry]

Inventor only seems to give Moment of Inertia about a part's centroid. If
you want to calculate that part's MI about another point you can use the
Parallel Axis Theorem:

I(x,y,z) = I(xc,yc,zc) + md^2

I(x,y,z) = the axis you are trying to solve for MI about
I(xc, yc,zc) = the parallel axis through the centroid which IV gives you
m = the mass of the object
d = normal distance between the centroid and the I(x,y,z)

Hope this helps,

Patrick Berry

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