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Thread: Stick welding a steel rack out of scrap pipe

  1. #26
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    Re: Stick welding a steel rack out of scrap pipe

    The lower part of every arm is in compression.

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  3. #27
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by arcflash View Post
    The lower part of every arm is in compression.
    Yep, I have quite a few of the same style racks at the shops and a few I have done for other people... haven't had one fail yet but the ones with smaller vertical pipes do have some sway to em' if you bum p into them with the forklift

  4. #28
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by Munkul View Post
    in tension, hollow section has nearly the same strength as the same diameter solid section. It's basic college engineering.

    in practice, you're nearly always better off going for a larger size hollow section, than a smaller size solid.

    Oscar, good use of nasty old pipe
    I think you are misquoting or you are only talking about half of the picture. Near the ends of a pipe it does not have the structural strength of the center of the pipe. If he put end caps on the bottom it would help, but still not the same thing. At the ends pipe will just distort and collapse like sheet metal. That is why I suggested a gusset at the bottom. It is not the loading of the material or storing that will collapse it. It is when something gets hooked while backing up with a forklift and all the weight and pressure instantly transfers to the bottom ninety degree joint. I have seen such things happen in real life. It just tears like paper.

    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

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  6. #29
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by Munkul View Post
    in tension, hollow section has nearly the same strength as the same diameter solid section. It's basic college engineering.

    in practice, you're nearly always better off going for a larger size hollow section, than a smaller size solid.

    Oscar, good use of nasty old pipe
    I have built both solid and hollow round and square tube projects and solid hands down is much stronger than tube, even larger tube of the same material, no matter what colleges say. Sure tube is nicer to cut and work with, but it just does not have the same strength or rigidity not even close. It will be the bottom joint that fails on that project for sure, if it fails. What will happen to the vertical at the bottom is that it will just distort and fail because there is no force holding it round at the end.

    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

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  8. #30
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by ronsii View Post
    Yep, I have quite a few of the same style racks at the shops and a few I have done for other people... haven't had one fail yet but the ones with smaller vertical pipes do have some sway to em' if you bum p into them with the forklift
    It does help to add some tabs and lag them to the wall. I built one like that once from used 2-1/2" boiler tube. Man that took some cleaning work.

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  10. #31
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by arcflash View Post
    The lower part of every arm is in compression.
    Except for the bottom one, and if someone were to wrestle with some metal at the top and pull on the entire rack, near the end of the vertical at the bottom there is very little structural support like there is in the center of a pipe, the vertical will just depress and deform at the bottom. I have done a lot of pipework, and a ninety-degree joint is not a very strong joint on a pipe, to begin with. I have had to break off pipes I put in the wrong spot and I am sure the vertical deforms because I have to remake it all over again. But a 90 degree joint at the end of a verticle is even worse.

    Sincerely,

    William McCormick
    If I wasn't so.....crazy, I wouldn't try to act normal, and you would be afraid.

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  12. #32
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by 12V71 View Post
    It does help to add some tabs and lag them to the wall. I built one like that once from used 2-1/2" boiler tube. Man that took some cleaning work.
    Tabs or some sort of restraints are always a great idea most of the racks I have are freestanding without a wall near them... or at least anything that would work to support them... also the majority of my racks are hand load only!!!... for now but I can see how I would be tempted to use a machine in the future

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  14. #33
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by William McCormick View Post
    I think you are misquoting or you are only talking about half of the picture. Near the ends of a pipe it does not have the structural strength of the center of the pipe. If he put end caps on the bottom it would help, but still not the same thing. At the ends pipe will just distort and collapse like sheet metal. That is why I suggested a gusset at the bottom. It is not the loading of the material or storing that will collapse it. It is when something gets hooked while backing up with a forklift and all the weight and pressure instantly transfers to the bottom ninety degree joint. I have seen such things happen in real life. It just tears like paper.

    Sincerely,

    William McCormick
    Sorry William, you're right, my bad. pipe needs capping in order to avoid collapsing on the pressure point, and therefore losing it's sectional strength.

    You could say that about any section... once it twists or buckles, you've lost the strength... the reason why lifting beam I section is braced.

    I'd have put some gussets in at the joints as well, but that's me... the rack is fine for light sections, and as long as Oscar is happy with what he built the rack for, then it's all good.

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  16. #34
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by William McCormick View Post
    I have built both solid and hollow round and square tube projects and solid hands down is much stronger than tube, even larger tube of the same material, no matter what colleges say. Sure tube is nicer to cut and work with, but it just does not have the same strength or rigidity not even close. It will be the bottom joint that fails on that project for sure, if it fails. What will happen to the vertical at the bottom is that it will just distort and fail because there is no force holding it round at the end.

    Sincerely,

    William McCormick
    Solid is more forgiving of overstressing, since it doesn't crumple like tube... but it's very wasteful, for the marginal strength increase. You're hardly going to build a rack out of 2.5" solid round bar, are you. It would cost a fortune!

    I do agree, if it fails anywhere it will likely be the bottom joint like you say. A couple of plate gussets would go a long way to spreading that stress and reducing the likelihood of crumpling.

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  18. #35
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    Re: Stick welding a steel rack out of scrap pipe

    In larger sections the weight of solid material can give a false sense of additional strength and actually be quite a bit weaker than a hollow section.

  19. #36
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    Re: Stick welding a steel rack out of scrap pipe

    Quote Originally Posted by Welder Dave View Post
    In larger sections the weight of solid material can give a false sense of additional strength and actually be quite a bit weaker than a hollow section.
    ...of the same mass.

    equal outer diameters and material yield strength - the solid bar is still stronger.

    The best way it was explained to me (and this is dredging the memory banks!) is if you take a solid rod and drill out the centre for it to lose half of it's mass, it doesn't lose half of its strength, because the outer elements are doing most of the work (highest stressed points while the centre remains relatively stress-free)

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  21. #37
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    Re: Stick welding a steel rack out of scrap pipe

    I can't fit a forklift into my garage. And I'm not an idiot to be wrestling with the material. No project of mine has such urgency. All of this is for fun. All of it. So I take my super sweet time for everything
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