Need someone to help determine centroid... Many thanks in advance!

[dude]

I have been here before regarding help with this type of question and I hope someone can help.

 

I have shape in 3D and I can give you the End View (Front if you want) and the Side view.

 

In both views it is a trapezoid. I am looking for the Cy (vertical) component specifically.

 

The drawing should be attached.

 

Thank you for any help you can give me.

[ReMark]

Create a 3D solid from your profiles then run the MASSPROP command on it. I think centroid is one of the outputs you'll get. If not there are any number of custom lisp routines that will find the centroid.

[dude]

I have Mac LT. I don't think I can do any of that. I am 2D only.

[ReMark]

Sorry about that. Maybe someone here can do it for you and report back the results.

[BlackBox]

I have Mac LT. I don't think I can do any of that. I am 2D only.

 

FWIW - As a student (the OP looks like a homework problem), you can access full AutoCAD for free.

[hmsilva]

Try to open this dwg, the centroid is a point...

 

Henrique

Solid_Centroid.dwg

[dude]

Thanks hmsilva. I can open it in LT 2012 for Mac but it took some drawing to get 22.1157" for the Z (vertical component). Dimensioning in three dimensions does not work on my LT.

 

Also guys, I get this every time I post but I am not working on homework.

 

Thanks again everyone! You all always come through! Now I have to figure out how to arrive at this on paper for this type of shape. I was close but not exact and that is just unacceptable.

[dude]

I found a formula on Wolfram's site. Finally.

 

 

When I do the math I get 21.98". My shape doesn't exactly fit the parameters but it is dang close and will do just fine!

 

Can someone double check the above DWG file and make sure my 22.1157". Just making sure my 2D backwards measuring is correct.

 

Many thanks again!

 

Linke to Wolfram's site. http://mathworld.wolfram.com/PyramidalFrustum.html

 

I understand this is not a right Pyramidal Frustrum but it close. I would have suspected it to be so far apart. I had estimated 21.857" my self from the side view.

Edited June 9, 2013 by dude
Added Wolfram Link

[BlackBox]

Also guys, I get this every time I post but I am not working on homework.

 

Fair enough... Just thought I'd throw it out there.

[dude]

Fair enough... Just thought I'd throw it out there.

 

No worries. I get that a lot. I just happen to like solving complicated problems that are useless in nature. Since every in here draws in 3D, it allows me to get a numerical check.

[hmsilva]

Thanks hmsilva. I can open it in LT 2012 for Mac but it took some drawing to get 22.1157" for the Z (vertical component). Dimensioning in three dimensions does not work on my LT.

...

 

dude,

I do not use "LT", but "LT" don't have the "ID" command?

 

...

Can someone double check the above DWG file and make sure my 22.1157". Just making sure my 2D backwards measuring is correct.

...

 

dude,

I built the 3d object with the dimensions you attached, and the centroid was not calculated by me,

I wrote a routine to extract the object "Centroid" property (as you can see in the attached image),

and "entmake" a point object at those coordinates.

Attached is also a dwg with some dimensions and some coordinates, I hope that helps.

 

Henrique

Solid_Centroid_1.dwg

Edited June 9, 2013 by hmsilva

[neophoible]

Looks like the formulae at Wolfram don't exactly apply, probably because the slope is inward on all four sides.

 

BTW, MASSPROP yielded:

 

---------------- SOLIDS ----------------

 

Mass: 11016.0000

Volume: 11016.0000

Bounding box: X: 0.0000 -- 5.0000

Y: 0.0000 -- 64.0000

Z: 0.0000 -- 51.0000

Centroid: X: 2.5000

Y: 32.0000

Z: 22.1157

Moments of inertia: X: 22420878.4000

Y: 7722758.3000

Z: 14862241.5000

Products of inertia: XY: 881280.0000

YZ: 7796064.0000

ZX: 609067.5000

Radii of gyration: X: 45.1143

Y: 26.4773

Z: 36.7308

Principal moments and X-Y-Z directions about centroid:

I: 5752502.8306 along [1.0000 0.0000 0.0000]

J: 2265916.7306 along [0.0000 1.0000 0.0000]

K: 3513007.5000 along [0.0000 0.0000 1.0000]

[dude]

You all have given me a lot to study to create a model for this.

 

Thank you to everyone!