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RE: Off topic, Moment of Inertia

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Actually, in Autocad (I checked this with Autocad 2000 ADT2) the Principle
moment of inertia is extracted which is not dependent on the location of the
object - which means that you don't need to move the object if your only
goal is to find Moment of Inertia.

BTW, thanks to those asking the question. I thought that this feature was
unique to the S8 add-on in R14 and earlier and had no idea it was a standard
tool with all versions of Autocad. Old dogs can learn new tricks. Thanks
again for knowledge.

Dennis S. Wish, PE

-----Original Message-----
From: Peter McCormack [mailto:pmac(--nospam--at)]
Sent: Thursday, February 10, 2000 11:04 AM
To: seaint(--nospam--at)
Subject: Re: Off topic, Moment of Inertia

The method I have used with reasonable results is as follows:

1. Center the shape about the origin (0,0,0) for a rectangle, circle
etc, the centroid will be at 0,0,0
2. Convert the shape to a region.(Using the pulldown menu : Draw-
3. then use the Mass properties function

I hope this helps.

Peter McCormack

Send reply to:  	seaint(--nospam--at)
From:           	"Fountain Conner" <fconner(--nospam--at)>
To:             	<seaint(--nospam--at)>
Subject:        	Off topic, Moment of Inertia
Date sent:      	Thu, 10 Feb 2000 12:45:05 -0600

> Does anyone have an ACAD Lisp routine that will reliably calculate the
> moment of inertia of a shape once it's drawn?
> I tried one, but it wasn't too accurate -- even on a simple rectanguar
> section.  Build-up sections were worse.
> Thank you,
> Fountain E. Conner, P.E.
> 1724 Beaver Pond Rd.
> Gulf Breeze, Fl. 32561
>    Phone 850-932-5547
>    Fax      850-934-1916