Best way to find center of mass?

[tjallen29]

Hello all,


I am trying to find the best (most reliable) way to determine the center of mass of an object and need to be able to dimention to it. I'm afraid I haven't had any experience in this realm but hopefully someone here can give me a hand!


Thanks!

 

[anand_m_s]

Please follow the steps given below:


1. Start an Ananlysis feature and run a Model

 

[yimu]

Hello everyone


What's CG?

 

[sanjeevkar1]

yimu


CG is short form to sat Center Of Gravity


now lets start with answering the real question.





in part mode. click Analysis>Model analysis. you will get following window








you can see the Center of Gravity values in terms of X, Y, Z coordinates.


im my case it is


X = 0.00


Y = -7.20


Z = 2.4 e 2


make a new coordinate with the values you got. and now you cancalculate the distants from defalut coordinates to the calculated coordinate.

 

[csusie]

if you have BMX you can make this an analysis feature and
also create a datum point at center of gravity, it is one
of the options in the analysis tool. If you do not have
BMX then instead of doing a quick check you can make it a
saved analysis and then relate a newly create point
(offset from default x,y,z) to the saved analysis values.
You would do that by writing 3 relations something like:

d1=cog_x:fid_117
d3=cog_y:fid_117
d2=cog_z:fid_117

Look in the help menu for exact syntax for creating a
relation to analysis values.

 

[Indusign]

Just use "calculate model properties"
select "assembly mass properties"
add a coordinate system in the assy, put relations on its dimensions as shown
$D257:1=PRO_MP_COGX
$D259:1=PRO_MP_COGY
$D258:1=PRO_MP_COGZ

place a datum point on that coordinate system, so you can attach a COG symbol on it in a drawing

All this can be done in the foundation of ProE (WF2)

 

[sanjeevkar1]

thanks a lot for the relation driven COG, Indusign.


but i have a problem calculating it. (may be i am missing something somewhere)

when i do <assembly mass properties> check i see some values of X, Y, Z COG. (as in figure 1). but when i go to properties and check the reported properties i see all the values as zero ( as in figure 2)


and due to this reason the COG coordinate that i am driving thru relation is coming on the default coordinate system. (as all the values are 0)





FIGURE 1





figure2





PLEASE HELP

 

[Knut Fiskergård]

Not sure there are any differences in how the progam is set up, but here is my suggestions. to get a value in the mp_pro param, you must tick them of. In WF3 I go to analysis/model/mass properties. from the quick/saved/feature options I select feature an go to the feature tab.





In the feature tab/parameter, scroll to find the COG's and tick off and save. Now the &mp_pro_cogx/y/z should work.





or if you can pic a datum, youll get the cog right in the drawing.





Hope this helps

 

[megaladon]

and the final easiest way to do it is analysis/model/ mass properties change it to feature and click feature tab and check mark create cog. make sure this is your last feature in the model tree and you'll always have the correct cog

 

[csusie]

Megaladon,

Depending on what version you are running I believe this
may be limited to people that have BMX.

 

[Knut Fiskergård]

Think your'e right csusie


The pictures I added are taken with a "standard" version, but if I start with a flex3c license I'm allowed to mark the csys and point option for COG.

 

[sanjeevkar1]

i am using WF2 ( yes still using WILDFIRE 2) and i am not getting <FEATURE> tab on Model Analysis window (as Knut has shown in previous post)

 

[mardeb]

and the final easiest way to do it is analysis/model/ mass properties change it to feature and click feature tab and check mark create cog. make sure this is your last feature in the model tree and you'll always have the correct cog

To get the feature to always be the last feature, right click on the analysis feature in the model tree and choose "Move to Footer". This will create a footer at the bottom of the model tree that is always the last thing to regenerate.

 

[kdem]

i am using WF2 ( yes still using WILDFIRE 2) and i am not getting <FEATURE> tab on Model Analysis window (as Knut has shown in previous post)

On the Model Analysis dialog box in WF2 there is an Add Feature button at the bottom that becomes selectable after you compute the Model Mass Poperties. An analysis feature shows up in the model tree. Edit the definition and the COG's are located under Result Datums. You canget the parameters under Result Params. To see the parameters select Tools>Parameters and select datum csys or point. There is also the analysis feature on the tool bar or Insert>Model Datum>Analysis.
Edited by: kdem

 

[sanjeevkar1]

thanks Kdem