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I used some 1/2" pipe (I got it at Lowe's; I think it's typically used for gas?) to build a simple frame for a heavy bag, essentially an inverted U (about 6.5' high, 5' wide), attached to wooden feet, which are weighted by sand bags. It was fine for a day, but I have two problems; The first is fairly simple - the vibration caused the fittings to separate. The second and more serious problem is the pipe is bending just slightly - enough that I expect it wont last more than a month or two. While I know now I should have used stronger materials, I don't want to replace the entire thing. I'd like to know the absolute cheapest way to secure the fittings (Liquid weld?) and to reinforce the pipe itself. I was thinking I could probably fill it with something, but I don't know what - Would cement work?

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    It might help to know exactly what type of pipe and fittings you're working with.
    – Tester101
    Commented May 6, 2015 at 12:11
  • Lowe's lists the pipe as LDR 1/2-in 150-PSI Black Iron Pipe and LDR 1.5-in Black Iron Fittings. I don't have the exact lengths I used handy, But I'm fairly certain I used a 5' piece for the horizontal, and the vertical pieces are 5' connected to a 18"
    – Patrick
    Commented May 6, 2015 at 12:23
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    Are you using threaded fittings? If so, a little pipe dope on the threads before tightening, will allow you to tighten them down just a bit more. Are both the horizontal and vertical pipes bending, or just the horizontal pipe?
    – Tester101
    Commented May 6, 2015 at 13:59
  • They are threaded. Actually it's just the vertical pipe bending visibly. Not a lot, maybe 5 - 10 degrees
    – Patrick
    Commented May 6, 2015 at 14:04
  • Without seeing the setup, it is hard to understand the problems. First of all, things like this are using suspended from an overhead support, not freestanding on the ground. If this is a technical bag you talking about, it will not be secure with just a few sandbags on it. Commented May 6, 2015 at 14:22

3 Answers 3

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Find a pipe with a diameter that allows your existing pipe to fit inside. Then cut is just shorter than your horizontal pipe, and put it over the horizontal pipe.

The top bar will not bend as much, and the side bars will not bend as much. It may last a lot longer than you expect as-is, but this will reinforce it where it's needed most.

This piping isn't meant to be used structurally. Once you get a large enough diameter pipe, it'll work, but the fittings will perpetually be a problem because you are applying significant sudden and repeated forces to the frame. You will eventually need to add set screws or something similar to the joints. Drilling a hole and using self-threading metal screws might be sufficient.

Once that's done, though, 1/2" just isn't going to cut it. For the loads you are applying, 1" might be enough, but you should consider going even larger for a 5 foot span of pipe. Keep in mind you're not just supporting 70 pounds, but all the force you add to it when you practice, which can be several hundred pounds.

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Replace just the top piece that the weight is actually hanging off of. You can use 3/4" or 1" pipe for that, and then connect it to the 1/2" pipes of the sides with appropriate fittings.

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  • Is that going to help the vertical pieces ? Seems like they have the most stress.
    – Patrick
    Commented May 6, 2015 at 13:40
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    Are they bowing out from the weight? If not, then leave them. The pipes are going to be stronger along their length than perpendicular to it.
    – iLikeDirt
    Commented May 6, 2015 at 13:41
  • They are. I apologize, I should have been more specific.
    – Patrick
    Commented May 6, 2015 at 13:45
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    Just replace everything and do it right this time. Chalk it up to a lesson learned. You can't be out more than $30, right? I mean, it's just cheap black iron pipe.
    – iLikeDirt
    Commented May 6, 2015 at 14:41
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    Cement won't do a thing for you, other than ruin the potential resale value of your 1/2" pipe and fittings on craigslist. Either buy 1" pipe, or find a welder to weld the frame up out of tube or square tube stock in a decent size.
    – Ecnerwal
    Commented May 6, 2015 at 14:58
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Assuming the pipes are threaded into fittings, to prevent the fittings from loosening, you can use red loctite on threads before assembly.

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