I have a shape that I'd like to calculate the polar moment of inertia for:
the diameter is 600mm; the hexagon in the middle sides are 70mm each; the holes around the hexagon are 130mm from the center of the disk and they are 16mm.
$$ \frac{\pi D^4}{32} - \frac{5\sqrt3}{8}s^4$$
How can I remove the 5 holes from the calculation? Is that even something that's done?
[EDIT] The disk is 30mm thickness. The mass of the disk is 66.5Kg
The mass of the small holes is total 0.3Kg
The hexagon mass is 3Kg
weight without holes is 66Kg
mass with the circular cutouts is 66.5-0.3 = 66.2kg mass with the hexagon cutout is 66.5-3 = 63.5Kg mass with all the cutouts is 63.3Kg
Which percent change in weight would help calculate the polar moment of inertia for this shape?