How to calculate polar moment of inertia using Inventor 2014

[matiscafe]

Hello,

I have a problem with calculating polar moment of inertia of a cranshaft with cooperating parts (which  I've already assembled in Inventor). Moment should be calculated to axis of rotation of crankshaf and I have no idea how to do that altough I search a lot through the internet for information.

Maybe someone could give a hand and help me?

[johnsonshiue]

Hi! I think you are looking for a geometric attribute of an area not a volume. First, you need a 2D Sketch with profiles. Then edit the sketch -> Inspect -> Region Properties -> pick a desirable profile region.

Thanks!

[cadman777]

No, I think he wants the same thing I want:

Polar moment of inertia ("Jm", not "J", and definately not "I", in Machinery Handbook).

Will you please tell me which "Inertial Properties" on the "Physical" tab is the Polar Moment of Inertia I need to use in calculating torque and horsepower for a rotating assembly?

There are:

1. "Principle Moments" on the "Principle" button, and

2. "Mass Moments" on the "Global" button, and

3. "Mass Moments" on the "Center of Gravity" button.

Where in the help or otherwise can I find a simple but comprehensive explanation of what these are?

Or maybe you can tell me?

Also, what command in Inventor can I use to find the Radius of Gyration of this assembly?

Thanx ...

PS: I use Rhino for this, but it's VERY labor intensive to convert to it due to how it interprets the STEP file, and it is NOT "bi-directionally associative".

[an00p]

What he said is right. 

The polar moment of inertia is basically moment of inertia of a particular area. It will be shown in the region properties..

For that you have to take the section view of the particular area of which you have to calculate the Polar Moment of Inertia. Then take the region properties.