I'm a non-engineer with a weight/strength question for angle iron. Under the hood of my car, I need to add angle iron to support an additional piece of hardware. This will consist of two parallel pieces of angle iron, spanning about 3 feet and holding around 80 pounds.
Angle Iron Size
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Posted by: wjdennis ®

01/10/2006, 11:32:34
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I'm a non-engineer with a weight/strength question for angle iron. Under the hood of my car, I need to add angle iron to support an additional piece of hardware. This will consist of two parallel pieces of angle iron, spanning about 3 feet and holding around 80 pounds. I haven't had much luck understanding the beam deflection calculator. Can someone give me a recommendation of what size angle iron to use? For example, 1 x 1 x 1/8, etc.

Thanks.

Bill Dennis








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Re: Angle Iron Size
Re: Angle Iron Size -- wjdennis Post Reply Top of thread Forum
Posted by: zekeman ®

01/11/2006, 11:45:42
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Provide a sketch or giive a better description of the load and the support structure so that you can get the help you.







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Re: Angle Iron Size
Re: Re: Angle Iron Size -- zekeman Post Reply Top of thread Forum
Posted by: wjdennis ®

01/11/2006, 13:05:35
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Here's a top view, looking down on the engine compartment.
NOTE: In the diagram, the width should be 4.5 inches, not 9 inches. Sorry.

 

AngleIronDiagram.JPG (19.4 KB)  





Modified by wjdennis at Wed, Jan 11, 2006, 14:26:38


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Re: Angle Iron Size
Re: Re: Angle Iron Size -- wjdennis Post Reply Top of thread Forum
Posted by: zekeman ®

01/11/2006, 16:07:20
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For a span of 36 inches and assuming 40 lbs on each of the beams conservatively placed at the center, I get an angle iron of 1x1x3/16, which will give a stess of about 9000 psi which would yield a substantial safety factor. If you want to use 1x1x1/8, it would also be safe, yielding stresses of about 12000psi.
I personally would go with the larger one.
The deflection at the middle is
FL^3/EI=40*36^3/(48*29000000*.03)= .04 inches







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Re: Angle Iron Size
Re: Re: Angle Iron Size -- zekeman Post Reply Top of thread Forum
Posted by: ChrisMEngr ®

01/11/2006, 20:16:52
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Is space a problem at all? Is there room for 2x2 angle? I have not crunched the numbers but if zekeman says 1x1x3/16 would work then it probably will with no problem and I would feel comfortable.

I am also curious if you are welding it or bolting it in place? With larger angle, it shouldn’t be a problem but it can affect different’ stresses coming into play.

If you aren't worried about the weight of the angle, I would go larger. 2x2x1/4 will cost a little more but for two 36" spans it wont be a whole lot more. Basically, the larger angle you get, the larger the safety factor you get. There are times where over designing something can be a bad thing. Weight and cost can be a negative thing. In this case, by bumping up the size; weight and cost aren't going to raise all that much. Especially for two 36" sections. And you get a large safety factor.

In my opinion, I would go for the bigger stuff if there was room.








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