Subject: Help in mechanical design

From: [email-masked] (Dion Hollenbeck)
Date: Fri, 28 Jun 1996 17:29:20 GMT

Here is a Stainless Steel stand I want to build.  I would like to make
it out of square tubing, maybe 3/4".  The square tubing will be easier
to cut and weld than round.  The two sides of the stand will each hold
a container weighing approximately 150 lbs.  The two sides of the
stand will share a common center set of legs.  On the bottom of each
leg will be a leveler foot.

Side View

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End View

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Top View

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Approximate dimenions are 24" high, 36" wide and 20" deep.

My question is, how do I calculate what tubing size including wall
thickness will be appropriate and will hold the weight it is destined
to take plus an adequate safety margin?

I know the compressive load on a single 2x4 is close to a ton, but I
have no idea of how to calculate this for metal.

thanks,
dion

-- 
Dion Hollenbeck (619)597-7080x164                 Email: [email-masked]
Sr. Software Engineer - Vigra Div. of Visicom Labs  San Diego, California

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From: T Lipton <[email-masked]>
Date: 29 Jun 1996 01:46:10 GMT

> to take plus an adequate safety margin?

  Their are many considerations is the analysis of a frame frame. 
The stand you have described in your post would easily support the load,
but in my opinion would be a little wobbly with three hundred pounds on it.
For your money go with the largest section size. If I was asked to design a similair stand
I would not even consider anything less than one and a half inches square for the tube. 
You can go with a light wall thickness like .06 and be okay. The compressive and bending loads on the stand
pale in comparison to the stability issue.
  The cost diffrence in the material is not bad to get a sturdy stand.

       Goood luck  TML

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From: Charles Lamont <[email-masked]>
Date: Wed, 3 Jul 1996 21:53:47 +0100

T Lipton writes
>> it out of square tubing, maybe 3/4".

>The stand you have described in your post would easily support the load,

agreed
>but in my opinion would be a little wobbly with three hundred pounds on it.

agreed

>If I was asked to design a similair stand I would not even consider
>anything less than one and a half inches square for the tube. 

hmm, for simplicity of construction, yes, but if I were designing for
minimum weight and maximum stiffness, then I would consider either small
section tube with cross bracing to triangulate it, or a sheet metal box. 

-- 
Charles