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Old 11-14-2006, 08:48 AM
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subzali subzali is offline
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Default welding question

So for senior design we are going to be tensioning some wires between two poles. The poles are going to be 3" pipe and will be anchored on the bottom. At 5' and 8' above the ground we are going to have horizontal members welded to the vertical tube. These horizontal members are going to be about 1' long on each side of the vertical tube and we will be pulling on the ends of these. We were thinking of using a 3" pipe on each side, welded to the vertical piece, to create these horizontal members. Will the welds hold a 400+ pound load about 1' away?

Alternatively, what are some other designs that might work better? What if we used a smaller pipe dia.? Would it still hold?
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Old 11-14-2006, 11:01 AM
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well the standard answer for this is "depends"

given proper prep, joint fitment and design, as well as good penetration, the weld will have a strength of 60, 70, or even 80kpsi, depending on the filler used, so a 400# constant load should not be a problem.

However, remember if you are using pipe, schd 40 stands for 40kpsi, and schd80 stands for 80kpsi.

Can you provide a drawing for what you are doing? The point of failure is most likely to be in the shape or design of the side piece. If merely a linear "pull" on the cable to the side piece to the post, the main area of stress will be the attachment point on the side piece.

remember, fabrication, as well as all actions in life depends on the following:
cleanliness, lubrication, and penetration

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Old 11-15-2006, 09:30 AM
leiniesred leiniesred is offline
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I think you'll be fine. I bet I've hung 400 pounds on a 3 inch tree branch.
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Old 11-15-2006, 11:52 AM
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Or 4K on 1/16" sheet metal in your gas tank!!!
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Old 11-15-2006, 01:20 PM
leiniesred leiniesred is offline
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Default Mr. Bad idea..

Well, Chili, I can't remember anyone accusing me of doing things the "right way."
I don't think my tank is much (more) bent than it is in this image:
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Old 11-15-2006, 09:04 PM
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Matt,
Pay attention to the maximum bending stress at the base anchor location. Assuming you are pulling with 400 x 2 at the 8 ft. level, you are looking at 6400 ft.-lbs. of overturning moment. You need to check the crippling stress of schedules 40 or 80 pipe. If the welded joints are done properly I don't think you will have a problem there.
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Old 11-15-2006, 09:29 PM
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Quote:
Originally Posted by Deerskin
Matt,
Pay attention to the maximum bending stress at the base anchor location. Assuming you are pulling with 400 x 2 at the 8 ft. level, you are looking at 6400 ft.-lbs. of overturning moment. You need to check the crippling stress of schedules 40 or 80 pipe. If the welded joints are done properly I don't think you will have a problem there.
dude - you GAVE it to him.... I was trying to hint at that and see if he got it...

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Old 11-15-2006, 09:34 PM
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Quote:
Originally Posted by green machine
dude - you GAVE it to him.... I was trying to hint at that and see if he got it...
I didn't get the hint

But we already looked at that, that was first

Time to , -style!
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