Warped tube. Whats the best way to straighten?

[agent4573]

The tube is 1.5"x 0.120 wall thickness. It bent nicely around the mounting points after they cooled. Would the best way to straigten these out be to lay a bead on the opposite side then grind it off once it cools, or would a torch work better?

[Rambozo]

Hard to see what's what in your picture. It sorta looks like the center longitudinal tubes are too long for a straight line. Heat straightening is usually done with a torch. I find it to be more of an art than science, and I'm no artist. However, I've seen some amazing results from heat straightening, and typically you end up with less stress in the finished part, than bending, so it stays straight. Another thing is that there are mount tabs have a full circle hole, not just a tube notch, so they can be welded all around.

The tube is 1.5"x 0.120 wall thickness. It bent nicely around the mounting points after they cooled. Would the best way to straigten these out be to lay a bead on the opposite side then grind it off once it cools, or would a torch work better?

[performance]

Tubing is hard to straighten without flat spotting one side. It looks like the weld heated the tubing and bowed it? Likely the deviation in the tubing started well before the central area. A straight edge will tell for sure, if you can get it on the inside. You'll have to start where it begins warping and not in the center. If this is a frame or something, the best you might be able to do is get a high lift jack or a come-along and pull it back together and weld some braces/gussets in place to hold it in position. Be careful about deformation or cracking. Once you pull things into line, and secure it, a rosebud can release some of the stress at the point where the bend begins. Likely it is quite spread out over a large area.

[agent4573]

Hard to see what's what in your picture. It sorta looks like the center longitudinal tubes are too long for a straight line. Heat straightening is usually done with a torch. I find it to be more of an art than science, and I'm no artist. However, I've seen some amazing results from heat straightening, and typically you end up with less stress in the finished part, than bending, so it stays straight. Another thing is that there are mount tabs have a full circle hole, not just a tube notch, so they can be welded all around.

The frame was built off of the main horizontal tube in the picture and was perfectly straight before I welded in the tabs. THe two vertical side tubes and the center two vertical tubes were welded in first and everything was square before I welded in the tabs. The part of the bar the outside mounts are on also bent and they aren't being contrained at all. I can fix those though as eventually I'm going to be putting in gussets and can pull them into place before welding. Its the center of the bar I just want to get back to straight. I wasn't sure of the process for heat straightening, but I'll ask my friend with a torch setup to let me use it for a while and try to get these back in place.

[Rambozo]

The frame was built off of the main horizontal tube in the picture and was perfectly straight before I welded in the tabs. THe two vertical side tubes and the center two vertical tubes were welded in first and everything was square before I welded in the tabs. The part of the bar the outside mounts are on also bent and they aren't being contrained at all. I can fix those though as eventually I'm going to be putting in gussets and can pull them into place before welding. Its the center of the bar I just want to get back to straight. I wasn't sure of the process for heat straightening, but I'll ask my friend with a torch setup to let me use it for a while and try to get these back in place.

Here are the basics. Although this deals mainly with I beams, you can see how you would apply the same type of heat patterns to tubing.

http://www.fhwa.dot.gov/bridge/steel/02.cfm

[sticks]

Hard to see what's what in your picture. It sorta looks like the center longitudinal tubes are too long for a straight line. ...

I'd have to agree here. Did the other ends separate from the top (according to the picture)? Did you put a good tack welds on all the pieces before you did your final welding?

Another quick and dirty option would be to take a chain and hook to your two outside corners (bottom of pic) and put a jack with a sturdy piece of box tubing or a 4x4 against the center of the bow (that will spread the load out about 1/3 of the total length of the bowed piece) and try to press it back into position. You will have to over bend it a touch then relax it. Check for straight, rinse and repeat as needed. I've found that once you put the slight over bend in it, to either give it a little heat or a firm smack with a hammer to "shock" it and keep it in position. Bear in mind that this is a trick I learned in the field when equipment and options are limited, and you do what you can with what you have available.