max moment on tower Smile
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Posted by: ericeb3 ®

02/15/2006, 15:25:45
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I am making a wind powered generator and I need to know how strong of metal pipe I need to hold this up. I know how much of a moment will be on the tower but I havent goten into calculating what the maxium force can be on a pipe before it starts to bend. I was wondering if there are table somewhere where it could tell me how much moment a size of pipe will take before it starts to bend?

Thanks for any help.








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Re: max moment on tower
Re: max moment on tower -- ericeb3 Post Reply Top of thread Forum
Posted by: ChrisMEngr ®

02/15/2006, 19:31:44
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What is your moment?







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Re: max moment on tower
Re: Re: max moment on tower -- ChrisMEngr Post Reply Top of thread Forum
Posted by: ericeb3 ®

02/18/2006, 17:55:24
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The book i have says that there will be a force of 250kg per square meter on the tower. So 250*9.8= 2450N. I will have an exposed area of 1.16 meters square. My tower will be 9.14m tall. So 1.16*2450*9.14= 25975 N/M. But then adding in a safty facter of 2 gives 25975*2= 51951 N/M.

If you could include how you got your calculation it would be helpfull. I am familiar with things like stress, strain, Modulus of elasticy, yield strenght so if you can tell me the formulas that you used so that I can see how it is calculated it would be helpfull.

Thanks for the Help.








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Re: max moment on tower
Re: Re: max moment on tower -- ericeb3 Post Reply Top of thread Forum
Posted by: ChrisMEngr ®

02/18/2006, 19:08:57
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When it comes to seeing what kind of moment a pipe, tube, angle, or other structural shape can withstand, you will need the following equation:

(stress)=(My)/I

where

M is your moment
y is the distance from the neutral axis of bending to the furthest point on the cross section sometimes it is refered to as c
I is your moment of inertia

just a quick note, your seciont modulus S is S=I/y

There are catalogues that have all pipe sizes availabe and will give the section modulus for each size.

If you know what material you are using then you should be able to find its yield strength. You do not want your structure to fail so you never want the material to undergo a stress more than its yield stress. You already know your moment so the above equation will look like

[(yield stress)/M]=y/I

or

[(yield stress)/M]=1/S

find the section mudulus that will satisfy your loads and you will have found your pipe size. If you dont find any books or catalogues that have section moduli for different pipe, then you have a little more algebra to take care of solving for I but nothing impossible.

I hopes this helped. If not, tell me what part you dont understand and I will try to clarify it. You can also do a search on the web, there are TONS of example problems worked out for situations like yours. Search for moment calculations, section modulus, pipe moment calculation, etc.. I am positive you can find something.








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