Volume centroid used when scalling?
Volume centroid used when scalling?
(OP)
Hi,
I have a solid body (of a material of uniform density, for example steel), and I want to scale it by 2 times. As a center of scaling, I have always been using volume centroid, as its the same one as the center of the mass. Here is the preview of the body and its volume centroid:

"VC" - Volume Centroid
My colleague is now suggesting that I should rather take the volume centroid of the box that covers the mentioned body:

"BVC" - Box Volume Centroid
Here is the difference between objects once 2x scaling is applied:

"ScaledVC" (light red colored) is the 2x scaled object with VC(Volume Centroid) taken as the center of scaling.
"ScaledBVC" (blue edges colored) is the 2x scaled object with BVC(Box Volume Centroid) taken as the center of scaling
Both volume's of the scaled bodies are the same, but they do not have the same position.
Which one is correct?
Thank you.
I have a solid body (of a material of uniform density, for example steel), and I want to scale it by 2 times. As a center of scaling, I have always been using volume centroid, as its the same one as the center of the mass. Here is the preview of the body and its volume centroid:
"VC" - Volume Centroid
My colleague is now suggesting that I should rather take the volume centroid of the box that covers the mentioned body:
"BVC" - Box Volume Centroid
Here is the difference between objects once 2x scaling is applied:
"ScaledVC" (light red colored) is the 2x scaled object with VC(Volume Centroid) taken as the center of scaling.
"ScaledBVC" (blue edges colored) is the 2x scaled object with BVC(Box Volume Centroid) taken as the center of scaling
Both volume's of the scaled bodies are the same, but they do not have the same position.
Which one is correct?
Thank you.






RE: Volume centroid used when scalling?
Here are the there photos that should have appeared up:
http://files.engineering.com/getfile.aspx?folder=6...
http://files.engineering.com/getfile.aspx?folder=0...
http://files.engineering.com/getfile.aspx?folder=1...
RE: Volume centroid used when scalling?
RE: Volume centroid used when scalling?
RE: Volume centroid used when scalling?
RE: Volume centroid used when scalling?
if the centroid of the scaled volume is critical it should be defined.
another day in paradise, or is paradise one day closer ?
RE: Volume centroid used when scalling?
I am not sure I understood you.
By scaling a volume its support surface underneath moves also.
RE: Volume centroid used when scalling?
another day in paradise, or is paradise one day closer ?
RE: Volume centroid used when scalling?
Yes, when scaling this body, the center of the scaling should remain fixed. The problem is that up until now I have been using volume centroid as the center of the scaling.
Now, it looks like volume centroid of the box that covers this body could be used too.
RE: Volume centroid used when scalling?
The size of the solid will still be changed appropriately (ie the scale factor) however depending on where you scale from the objects location in space will change accordingly.
RE: Volume centroid used when scalling?
The BVC is an arbitrary choice. You could just as easily use any point on or off the object as origin. Then the x, y and z dimensions to each point on the scaled object would be precisely 2 times the x, y and z dimensions to the same point on the original object.
BA
RE: Volume centroid used when scalling?