[Plugin] Center of Gravity

[TIG]

CofG.PNG

Copyright 2010 (c) TIG
[Parts Based on TIG's 'Volume.rb' tools & some ideas from
Alexander Schreyer's 'GetCentroid.rb']
All Rights Reserved.
THIS SOFTWARE IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES,INCLUDING,WITHOUT LIMITATION,THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.

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CofGravity.rb
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Center of Gravity and Related Properties Tools

Usage:

'Find C of G'

This works out a 3D Shape's Center of Gravity and other properties...
Select one 'Group*' or 'Group* of Groups*' [*or 'Component Instance']
= the 'Shape'.
From the Plugins sub-menu 'C of G...' run 'Find C of G'.
[There will be error messages if it's not a suitable selection]
It asks for the Shape's 'Density' and its Units, available
units are = kg/m3, tonnes/m3, g/cm3, tons/yd3, lbs/ft3.
The defaults are 1000 and kg/m3 [the density of water].
So for example, you'd enter 2323, kg/m3 for Sandstone.
The entered Density and its Units are remembered for that Model and
thereafter they are used for the dialog until they are changed.
It also asks for the Shape's 'ID' - the default is taken from the
selected Shape's 'name' - e.g. 'Beam3' - you can enter anything
you wish as an alternative. If it's an unnamed Group its default is
'Group'. If it's a component and the instance also has a name the
definition and instance names are combined - e.g. 'Beam3:Granite'
It processes the Shape [this might take a while - please be patient...]
It adds an overlaid element, named after the 'ID'; it also has a
description added.
This element displays the Shape's ID, Volume, Density and Weight.
It also indicates the Center of Gravity [CofG] & the 6 Axial
Suspension Points [SP].
To see the CofG use Xray mode as it's often placed 'internally'.
Do not edit the contents of a C of G element if it might be used later
in 'Composite' processes.
If parts have different densities then you should group them
separately and process them in turn - you can work out the
'Composite C of G' later...

'Composite C of G'

This works out the 'Composite C of G' of two or more already processed
'C of G' elements.
It is important that they remain in their original relationships and
alignments - moving them will return inaccurate results.
Note that these must have been made with the same units of density -
e.g. all in 'kg/m3': although the densities themselves may vary.
Select two or more premade 'C of G' elements.
From the Plugins sub-menu 'C of G...' run 'Composite C of G'.
[There will be error messages if they're not suitable selections]
It processes the selected C of Gs and then adds an overlaid element:
named 'CompoCofG' - its description includes the names of those
C of Gs that have been made composite.
This displays the Combined Shapes' 'Composite Weight', it also
indicates the Combined Center of Gravity [CofG] & the 6 Combined
Axial Suspension Points [cSP].
You can reuse a 'CompoCofG' in subsequent 'Composite C of G'
processes to find another combined C of G etc...

Note:
The C of G element has a special component placed at its 'C of G' -
called 'CofG'. Do not move, edit or delete it, as it might be used in
subsequent 'Composite C of G' processes.

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Donations:
Are welcome [by PayPal], please use 'TIGdonations.htm' in the
../Plugins/TIGtools/ folder.

Version:
1.0 20100303 First Release.
1.1 20100303 Accuracy improved. CompoCofG Description improved.
1.2 20100307 FR lingvo added by Pilou.
1.3 20100308 Missing require deB... added.
1.4 20100308 'calculate' becomes 'do_calculation'.
1.5 20100310 'composite' becomes 'do_composite'
Reworked to suit all Macs as well as PC.
ES lingvo added by Oxer.

[TIG]

Here's a Composite C of G, made from the three stone detailing pieces assembled - useful if they are of differing density materials and to be fixed together off site and then handled/lifted on site...
[Original CofG's hidden for clarity]

CompoCofG.PNG

[TIG]

Here's v1.1 viewtopic.php?p=229401#p229401
Accuracy improved.***
CompoCofG description improved.

***The shape is now sampled at 0.5% of its height.
So if it's 1000mm high that is at 5mm c/c* - this should pick up most fine detail ins and outs in its section.
Ins and outs in plan are picked up anyway.
If you do have a weird shape that's say 'combed' in the vertical at very close centers* then you could turn the shape on its side to get an even more accurate CofG... BUT 99% of the time the default analysis will be sufficient - within a 'mm' or so - considering the variability of natural materials' densities I'd say that "sufficient is fit"...

[MALAISE]

Interesting plugin, as far as I can use it in SketchyPhysics.

Thx TIG

MALAISE

[TIG]

It was actually made after a request by someone making historical stonework detailing. They needed to find the top Suspension-Point to add a lifting-eye so the delicate pieces can be lifted squarely and simply and bedded in place...
For that you need the Center of Gravity which gives you six axial SP's...

[Dave R]

Very nice TIG. I didn't know I needed this plugin until now. Thanks.

[alexschreyer]

Thanks, TIG, for expanding into the third dimension. This is a great plugin.

Cheers, Alex

[honoluludesktop]

Wow, SU as a structural engineering engine?

[utiler]

Very nice TIG. I didn't know I needed this plugin until now. Thanks.

Like Dave, I didn't think i needed this until now.... Looks neat TIG!!

[mitcorb]

This item could be very handy. Thank you.

[jonorman]

I am out off words. This is a plugin I`ve been waiting but thought never would come.. I`m so greatfull

[Pilou]

Damned another very cool tool for ingeniery

[watkins]

A few useful sites giving densities of building materials etc.

http://www.simetric.co.uk/si_materials.htm

http://www.civl.port.ac.uk/britishsteel ... rials.html

http://hypertextbook.com/facts/2000/ShirleyLam.shtml

http://www.rfcafe.com/references/genera ... erials.htm

[watkins]

Forgot to say that TIG's volume calculator (+ density) and CofG calculator give you the complete story when reviewing loads.

[DSG2k]

Vista and SketchUp 7.1.6860 . . .

Unzip of CoG plugin zip in the plugins folder resulted in a lot of overwrite requests (I just got your Manifold, too). I overwrote the older deBabelizer with the newer one.

Now on load a "Load Errors" window pops up, saying:

Error Loading File CofGravity.rb
undefined method `deBabelizer' for main:Object

And the plugin does not appear in the Plugin menu.

I don't know Ruby so I didn't actually poke at anything in the code, nor did I see anything obvious to me.

Just FYI.