Mass Properties

[FungShui]

Sorry for not introducing myself but I have a speech to give about the command "mass properties" for my engineering class, tomorrow. I am not entirely sure what the command does. I know it calculates the volume and area depending on 2-d or 3-d object, Moments of inertia,principal moments, etc. I want to know what are the practical and or engineering applications of this command.

I also have to do a demo using this command. I was thinking of using a camshaft as my demo and try talk about the attributes that "mass properties" calculates. Also if someone can send or tell me how to make a camshaft that would be great. Thanks in advance!


*edit*

Also how do you change the mass of the solid? Do you use materials in the render function. Sorry for being such a noob.

[CarlB]

As you may learn in your engineering class, the center of gravity, first moment of inertia, and second moment of inertia are properties of an object used in engineering calculations, for static and dynamic analyses. A use for MASSPROP would be to determine these properties for the cross-section of a structural member (beam, for example), to use in structural calculations (stress, strain, deflection, etc.) AutoCAD does not allow you to change the mass or density of an object for the MASSPROP command.

[vasqrainier]

how to regenerate the Bounding box, Moments of inertia, Product of inertia, Radii of gyration and Principal moments and X-Y directions about centroid?

in lisp code...

[ARKLisp]

Very very nice... try on your own! ...you'll get an answer sooner you can realize...

...concerning the demo:

1) you could use the following syntax:
(command "_MASSPROP" (ssget)"" "_Y" "c:\\file.mpr")

...then you could extract some infos from the file mpr through the autolisp functions "open" and "read-line",
...to read AREA value or else:

(setq file "c:\\file.mpr" )
(setq fi (open file "r"))
(read-line fi)
(read-line fi)
(read-line fi)
(setq value (read-line fi))
(close fi)
(alert value)
...


Bye!

ARK