Avaice request: Welding sequence to keep a piece square

[psacustomcreations]

I am going to add an arm to a heavy duty weight rack. The arm is going hold a punching bag that weighs about 40 pounds. I am trying to match the original rack. The main beam will be made from 1/4" thick 3" square tube. The plate is 3/8"x 3" flat bar. The diagonal is 2-1/2"x1/4" square tube. I have a Miller Passport 211 MIG, Dynasty 200DX, and 6010 stick available but I haven't used stick in several years. I have the Bessey corner clamps and welding table.

Weight rack



The new arm is in black in this pic




What sequence would you suggest? The number 3 of the sides is obviously in the back. Thanks in advance for the suggestions.

[neuralsnafu]

First question I will ask, is this power rack bolted to the floor?

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[greenbuggy]

If you're really worried about distortion, I wouldn't be looking for a "sequence" as much as I'd be inclined to tack it all over the place, double check that you're still square and do final join up by skipping around with <1" long welding beads, and then welding up the gaps in between. If you concentrate too much heat in a small area you can take a square junction and pull it out of square.

[davec]

First question I will ask, is this power rack bolted to the floor?

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Precisely. Looks like it has potential to tip over...Lotta weight to hang out 3.5' And I kinda doubt weld distortion will matter much for this, as long as it doesn't go crazy. Does the bag need to hang +/- 1/4"? Seems like you may be overthinking weld distortion, and underthinking about basic stability, but you did not give enough info to be sure on the latter point. You could just bolt it, too.

[psacustomcreations]

First question I will ask, is this power rack bolted to the floor?

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It is not bolted to the floor but here is a pic of the whole rack. The new arm will be on the front left of the rack and parallel to the pull up bar. If 42 inches is too long or too much of a lever, it can be shortened to 36 inches. The user can also add more weights to the rear racks if needed.

[Iain P]

Here's a video where Jody (welding tips and tricks) goes over distortion in some common welding situations. The square tube part starts at 6:00.

[Jimmy_pop]

First.

I'd have 6 bolt bolts total holding arm to main frame. Two top, middle, bottom. 2 holes side by side. A single hole bolt pattern down the center will act like a pivot.

Also, I'd tac the arm together and bolt it to a mock 3x3" baseplate. Weld the A'S and C'c while it is bolted down.

Weld all the A'S and C'S as you wish, they really are not going to pull much. I personally would not weld them all the way out. That is alot of heat. I would do symmetrically spaced 1" long welds in 4 or 6 spots around each 3x3 joint.

I would not weld B2 and especially not weld B4 at all. B4 will fold the arm over for sure. Just do an inch long Weld on B1 and that's it. The radius on 1/4" material butted up against the flat wall of the 3x3" tube at B1 will be a perfect and naturally prepped joint for doing a small weld and all you need. Don't weld B4.

I do agree with Dave about not being too concerned with Weld distortion. It's not going to be too much anyway plus the bag is going to pull the arm down anyway. From a design standpoint, why not add 1 or 3" of rise to the arm?

[Jimmy_pop]

Could you just bolt an 84" long piece of 3x3-1/4" to the very top of the rack (with 42' extending out) and not weld anything?

[psacustomcreations]

Iain P. I have watched quite a few of Jody's videos and was familiar with the technique for square tube. Adding the diagonal was where I am not sure.
Jimmy Pop. I looked at running a piece of square tube all the way across the tube but the uprights stick up 2 inches above the horizontal cross member. I can add material yt? O take up the difference.
I was also debating running another diagonal from front to back to lessen the chance for forward to back movement but the other cross member do not line up.
I will try to attach a pic from my phone but dont know if it will work


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[MetalMan23]

This is the sequence I would use; I'd tack it on each tubing corner, checking for square after each tack, then I would weld the horizontal joints, alternating direction of travel, then the vertical joints, alternating sides to keep the heat somewhat even.

[BD1]

Could you just bolt an 84" long piece of 3x3-1/4" to the very top of the rack (with 42' extending out) and not weld anything?

This above ^^^^^^. Me too, I would get the length required for the extension overhang and fasten to the existing top. You could weld flatstock to the sides of new top piece with holes to through underneath the existing top. I think it would look much cleaner and like a manufactured add on accessory.

[CEP]

It’s going to move, that’s a fact of life. Square tubing is very reactive to heat! It’s just a matter of what kind of tolerances you can live with.
Here are a few heat shrink techniques I use post weld to bring back into shape.

[outdoort]

First.

I'd have 6 bolt bolts total holding arm to main frame. Two top, middle, bottom. 2 holes side by side. A single hole bolt pattern down the center will act like a pivot.

Also, I'd tac the arm together and bolt it to a mock 3x3" baseplate. Weld the A'S and C'c while it is bolted down.

Weld all the A'S and C'S as you wish, they really are not going to pull much. I personally would not weld them all the way out. That is alot of heat. I would do symmetrically spaced 1" long welds in 4 or 6 spots around each 3x3 joint.

I would not weld B2 and especially not weld B4 at all. B4 will fold the arm over for sure. Just do an inch long Weld on B1 and that's it. The radius on 1/4" material butted up against the flat wall of the 3x3" tube at B1 will be a perfect and naturally prepped joint for doing a small weld and all you need. Don't weld B4.

I do agree with Dave about not being too concerned with Weld distortion. It's not going to be too much anyway plus the bag is going to pull the arm down anyway. From a design standpoint, why not add 1 or 3" of rise to the arm?

Thats interesting because I would have welded the whole thing out just jumping around. Not welding b4 and b2? Wouldn't it not seal and/or look okay? Even after paint? What if this was an outdoor application and it needed to be completely sealed? You would weld the whole thing then, right?

[Sharon Needles]

Thats interesting because I would have welded the whole thing out just jumping around. Not welding b4 and b2? Wouldn't it not seal and/or look okay? Even after paint? What if this was an outdoor application and it needed to be completely sealed? You would weld the whole thing then, right?

Welding b4 will cause shrinkage on that side of the arm that sticks out, causing it to nose dive towards the ground. You can weld it if you backbend it before welding.