Projects Need advice from the metal doctors

I'm building a replacement 1938 Holmes wrecker bed for my 1938 Ford COE. The bed side is 12ga 36" x 90". I plug welded a 3/16 x 3/4 bar along the top outer edge. Then welded a 3 x 5/16 bar on top. Now I have huge amounts of extra metal trapped in the panel.

Anyone have advice on how to fix this.

Here is the right bed side. I have 4 large tucks circled. I still need to cut the wheel well out, and add a wheel tub on the white line. The other white line is the floor line. A 1" x 1" angle will be plug welded there.





Here you can see the trapped metal.




And what the wrecker bed side should look like if fabricated correctly.





And the beginning of the job.



Please note that the large bluing along the end of the plate is not from welding. The material came this way from the mill.

 

Not sure what you mean by Trapped metal. I think you mean the buckles or waves. These are caused by shrinkage in your plug welds if the panel was flat prior to your welding. Personally I'd drill out the welds in that aria and release the tension and try again. I would have never plug welded that to start with. That would be a job for the Spot Welder around here.
The Wizzard

 

It looks like you made the top angle from the two strap pieces. If it were me, I would remove the angle parts, straighten the side panel (if possible) or replace it, then weld the angle parts together first and finally stitch weld them (short 1" welds spaced every 4" apart) to the side panel from underneath with the heat focused into the top part of the angle.

It's going to be cool, keep at it.

 

I would like to know how to straighten the sheet metal without cutting it up or starting over. There has to be a technique to fix this. Maybe with heat, maybe with a hammer?

 

You are going to have to use a big hammer to dolly out 12Gauge.

Welds pull and shrink as well as heat, you reverse the shrink by hammer

 

2 methods, 1 is to tap fairly hard directly on the plug weld, 2nd is to heat the highs, then quench to shrink, do not let it get red though

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Your right there is as Scott Best mentioned. However, If you've never done this before and you think it's a mess now. Do Not practice on the panel you want to save. It will only get worse. I do this stuff a lot. 12 gauge is tough stuff. I'm not sure I'd try hot shrinking it for you. Those buckles are there from stress. Best advice is to relieve the Stress, without heat.
The Wizzard

 

I think it will get better just by cutting the wheel wells out but don't take it to your line.
What doesn't come out from the removal should be much easier to work out.
You might have to trim the bottom so its flat again.
The bottom ( without weld) should be the original size and the top ( with weld) is actually smaller than original size.

 

I straighten tubes, beams, channels, and angles everyday. Just never straightened thin plate before. Thin to me is 12ga. I'm hoping it will be easier to straighten with the wheel wells cut out like 31Vicky said. Thanks for the advice everyone.

 

Fair enough, being you know how metal reacts to heat you should be able to do this. Were it me and I decided to use heat I'd have my 6" grinder wit a 36 grit on it real close. Heat the high spot to medieum red. Hit the highest point while hot with the disc them hammer in a circle around that spot pushing the metal to the center. Cool down is with a Air Hose not water. Again if your not used to doing this stuff maybe take a piece of scrap and try it once or twice. You'll probably get the hang of it right off.
The Wizzard

 

Ok, so on a beam you heat the high side, yes.
As the heat goes into the beam, the beam walks towards the heat,yes.
As it cools the beam walks away from the heat but further than where it started from, yes. Because it walks further it moves closer to being straight, yes.

Think of your bed side as the web of the beam- you heated the top- it walked up toward the heat- it cooled and walked down further than back to being straight.

 

I recently straightened some 3/16 plate for a jeep body armor that had places welded on it. it took a big hammer and lots of sweat to relive the stress from welding, but it did work.

 

I hope you expectations of fixed are not really high, you have a flat panel, no crown anywhere and a heap of shrink locked under the 3/4 flat bar, getting any stretch below that flatbar will be very hard to do, shrinking will only make matters worse as it will transfer into the flatbar and then you will have a bow possibly in both direction. the solution for this is to carefully cut the 12g off from the cap, repair cap or remake, work the panel damage out.
if the cap is drilled and threaded you can bolt from behind, grind off the excess and finish with a small weld, also allows the great option for rust proofing under the cap.
Are the wheel openings just cut, flanged or added too?

 

The wheel wells will be cut out and then a tub welded around. No flange, just a 90 degree welded corner going around the arch. Will the two welded radii cancel each other out? Will it get much worse?

I really see no way to remove the 3/16 x 3/4 bar from the 12ga. It is plug welded every 2 inches. I have a 100 invisible welded to cut loose.

 

No it will not "cancel" each other and it will get worse. Every time you weld you draw( stress ) the metal. the only way I have removed this stress is to hammer the weld (removes stress). The hammering reverses the drawing (shrinking) of the metal buy stretching ( stress relieving ) the weld.

 

zip wheel or plasma cutter, your only going to lose an inch of the 12 g, remake the top as a unit.
The wheel opening should be no problem, parts must fit correctly and be carefully tacked (I would start at the top of the arch as 12oclock then 11 and 1 etc, when in place tack between each tack alternating and not getting to hot, continue until all tacks are 1/4'' apart then weld an inch at 9oc them 3oc and 12, alternate is the key, I do tons of this stuff in 16g and never needed a filler, just go slow.

 

Good thought about the wheel well cutouts relieving some of the stress. With them cut out, the bad area will be small so maybe instead of shrinking the high spot, you can stretch the low spot?

 

Cutting out the wheel tub really lessened the peaks and valleys. I think I can work these small waves out with heat, hammer and dolly, and damp sponge.