Handrail bowed after welding
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    Default Handrail bowed after welding

    Here is my problem handrail bowed after welding top rail is 1x2x.120 wall rectangle mild steel and pickets are 1/2 solid cold rolled square tubing with 1.5 spacing , bottom rail 1/4 x 3 flat strap . I built it like this to match existing handrail on customers home any help would be great

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    That was bound to happen! To keep things reasonably straight, you need to fixture the rails on a welding table or make sure you weld top & bottom alternately, one picket at a time. Doing both is best. Since you used flat on the bottom and tube on the top, even those precautions aren't going to be perfect. If you welded all the pickets to either top or bottom at once, and have already added the other rail, it may be impossible to straighten. If you'll paint the railing you can heat the top rail directly over each picket to a medium red heat with an oxy-acetylene torch, and let cool. Use a welding tip and heat a pattern roughly the same as the weld where the picket is. At first it will bow the wrong way, but cooling will pull things back toward straight. (This assumes that the railing is crowned (convex) on the top.

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    Yes it's Bowing up the flat strap is laying flat behind the pickets to mount to a block wall could I use a chain at each end on top rail and a bottle jack in the center and Jack it up to bow the handrail the opposite direction to get it straight and how can I post a pic where is the attachment button ?20200117_174504.jpg
    Last edited by Fabkid33; 01-17-2020 at 09:43 PM. Reason: Pics

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    As Gordon pointed out, you can use heat to unbow the rail, just as heat bowed it. Basically, you use a torch to heat the rectangular tube to read heat in strips opposite each attached tube. Then hit the red hot portion with cold water. Folks use this technique to add bows to large sections (like 6x6 or 8x8 tubing) to provide arching bridge structures. Pick yourself up a copy of Tom Lipton's "Metalworking Sink or Swim". He goes over this technique.

    Check out this: YouTube

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    Place a heavy enough beam on the hollow site
    Then a ratchet strap around it and pull it straight
    At the end of the beam you plase some wood between beam and handrail to be able to overbent a bit

    Peter

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    Quote Originally Posted by Fabkid33 View Post
    Yes it's Bowing up the flat strap is laying flat behind the pickets to mount to a block wall could I use a chain at each end on top rail and a bottle jack in the center and Jack it up to bow the handrail the opposite direction to get it straight and how can I post a pic where is the attachment button ?20200117_174504.jpg
    Yes bottle jack and chain should do it. Just put something between the jack and the metal so it does not kink under the jack. Also a good idea to loosely clamp it to a table or something to keep it flat while jacking.
    If you can not do that you might try bolting it in place in the middle and jack up each end until it is straight and put those bolts in, but it is better to be straight before instal.

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    I suspect if you try to straighten by mechanical force, you'll end up with something worse than a nice even bow. The reason heat works so well is that the opposing force is applied very evenly, in the same places and to approximately the same degree as the force that caused the bow. It is much easier than you think, provided you have an O/A torch. A propane plumber's torch doesn't concentrate the heat enough to be predictable, not to mention being slow.

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    Do what Gordon suggested, but add in what bosleyjr suggested: "Then hit the red hot portion with cold water." A wet rag in a bucket of water works well. Its very controllable and you can tweak the straightening as you go.

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    The way to avoid this is to prewarp the handrail tube before welding. Put a hydraulic jack above the weld zone. Take a piece of very strong stock about two or three feet long and center it on the jack. Use straps or chains to fasten the ends of the strongback to the rail. Jack until the rail bows up about 1/4". Weld. Undo jack. Repeat. Learn.

    To fix, learn about flame bending. Not complicated, but you can f it up if you don't know what you're doing. Get a book. And BTW quenching with water isn't necessary and makes a BF mess. It's common in industry because it's fast and time is money, but you can cool with compressed air or just let it cool by itself and it will still work fine.

    They formed the legs of the Seattle Space Needle (huge beams bent in 2 dimensions) with flame bending.

    metalmagpie

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    Quote Originally Posted by metalmagpie View Post
    . . . quenching with water isn't necessary and makes a BF mess. It's common in industry because it's fast and time is money, but you can cool with compressed air or just let it cool by itself and it will still work fine. . .
    That's how I feel about it too. With nothing more than a #10 Victor rosebud and patience, I've straightened 8W I-beams with no trouble at all. Here's one more tip: Using air to cool, be patient. The steel needs to cool to where you can hold your hand on it before you'll know how effective your treatment was. If you think it isn't working and heat more/different areas, you'll over do it. On the bright side, thin wall tubing cools pretty fast.

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    If bowed down you can also displace metal in the bottom strap to straighten.
    A heavy bar set between pickets and a tap or two on bottom side with a hammer will do the trick.

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    Quote Originally Posted by Gordon Heaton View Post
    If you think it isn't working and heat more/different areas, you'll over do it.
    I echo that. First time I tried flame straightening square tube welded tee to square tube, I thought that, and did that and ended up with as much distortion away from centerline as I originally had from the weld pulling in, but in the opposite direction.

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    If you think that's bad, you should do stainless. That would have been in a pretzel.

    You can build yourself a H press with a 6x6, heavy duty straps, and a small bottle jack or porta power. Heat fixing is the simplest, but there is a learning curve.

    Next time, definitely clamp it down during welding and cooling.

    Sent from my SM-G960U using Tapatalk

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    As I understand it, it does pay to make up a jig to apply straightening pressure. Tom Lipton uses water, and I suspect that you get a quicker feedback if you cool with water, but the video I posted did not use water. And it's hard to argue with Gordon's experience:

    I've straightened 8W I-beams with no trouble at all.

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    I tried pulling it with bottle jack and chain and the middle flat strap really started to s shape on me making the pickets high and low so I broke out the oxy/acy torch and that worked somewhat with the flame straightING not perfect and couldn't really get it to shrink more in a few areas that I needed after 3 or 4 attempts .I left the pickets loose on the bottom flat strap there is a middle and bottom flat strap laying flat behind the pickets in that section the middle flat strap was already welded to the pickets so I flexed it with bottle jack until straight then welded the bottoms to the strap made it a little better overall I have about a 1/8 inch bow over 6 feet . The next section on the same handrail only has a bottom flat strap and I tacked the pickets to the top rail then welded them to the bottom strap then when I went to weld the pickets on the top rail I started on the ends and worked my way to the center welding all 3 sides and Cooling with ice water right after welding and only got about 1/16 of bow over 5 feet and part was just sitting on my sTeel stand overall it's getting better going to spend a few more hours on it tomorrow

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    Dont waste time with the water cooling. You need to tack all the pcs together and alternate welding the pickets in. I do a lot of custom picket railings and when they are all tacked in I weld 4 or 5 pickets on the top then then do 6 or 10 on the bottom, alternating until the end. weld top fillet and down right side then same on bottom rail. next set is top and down left side. then come back and do the missing sides, alternating in batches again. clean with wire brush and flip over to do last fillet on picket face, 1/2 from L to R and 1/2 R to L. this will not only help it stay straight but also keep it from racking.

    When you jacked it you should have clamped it down to keep it flat. To straighten that it might need to flex as much as 12" up to get it to spring back to flat. (depending on where you put the chains)

    Also if you clamp it down hard to a table and weld it out of sequence it will just spring when you unclamp it.

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