Repairing a locomotive roof

admin

Hi guys, I'm involved with a heritage railway where I live and recently took on the task of replacing some rusted out sections in the cab roof and side of one of our locomotives. I cut and replaced the bits on the cab side no worries but when it came to replace part of the curved cab roof I ran into trouble. The material was 1.6mm (16 gauge) and I thought "that's thin enough, I'll be able pull it round the curve", which I did, and it looked alright all tacked up. But when I welded it up it went to poo, and it pulled and "sucked in" between the internal ribs in the roof, and looks like poo. Looking back I should've got the patch for the roof slightly rolled, but I was too stupid.My question is, what would be the best way to "pop" the hollows out? Big fcken hammer? I dont really want to use heat because of the conduit and wood fibre panel interior lining, but if that's the only option I guess I could completely strip the interior.Now for the pictures.BeforeTacked up (does kinda look warped here, but not as bad)FinishedShown quite clearly hereRegards, Match> Cigweld WeldSkill 170 inverter
Reply:Don't think I would sweat that...that's my opinion thoSent from my DROID RAZR using Tapatalk
Reply:Can you get at it from the inside?Could you heat it up a bit and try banging it out from the inside?Dragon D-150 Arc WelderHobart Handler 175 Set up with 100% CO²WT-60 Plasma Arc Panasonic TIG Star YC-300TWX-2 Panasonic YX-0092UW Water Cooler for the TIG
Reply:Either use a hammer and dolly, or cut it back out, roll a new piece, just use a brake and put a few light bends in it. Then, when re welding skip around a lot more, make very short welds, and make sure that it cools down between welds.
Reply:if it's only stitched in you might want to cut the tacks and get a new pannel rolled up, as you'll be hard pressed to get a good curve in it once its welded. Or you could go with the "she'll be right" method of spot weld it all up keeping the heat low and put some paint and maybe some bog over it?
Reply:When I am welding sheetmetal, I always try to start in the middle and work to the ends.  If you tack the ends and the middle, you metal has no place to expand to but outward.
Reply:What you are experiencing is the shrinkage of the metal at the weld points.  When welding sheet metal an experience old school body man will weld the tack and then immediately use a hammer and dolly to to stretch the metal back by planishing the weld down.  We refer to it as crushing the weld.  Metal shrinks when heated and cooled.  If you try to use heat to straighten it the problem will only become worse because in effect you will just be doing what is called "hot shrinking".  BOG?  Come now, no real metal man will ever resort to bondo for a simple job such as this.  "Steel is real!  Plastic and paints looks like what it ain't"No real harm done yet, but you have created more work for yourself by letting the welds shrink.  I would probably start with a heel dolly (or one that closely assumes the profile of the desired shape) and a somewhat heavy "bumping" hammer (16 oz.) and start stretching the low spots in the middle of the divots.16 ga. is gonna take a bit of work but it can be straightened.  Should you decide to cut it out and go back to the beginning I would suggest you recreate the high crown brake line to match the others in the top.  It appears that the top panel was not rolled, but rather a series of sharp bends that approximate the curvature of the supporting structure.  I also would suggest you make your incision and welds in the brake line as the a high crown allows you a bit more structural strength and allows you to hide the repair easier (hammer, dollie, shrink and file).  As stated, weld a little , hammer a little, move on to a different spot and repeat.RogerOld, Tired, and GRUMPYSalesman will call, Batteries not included, Assembly is required, and FREE ADVICE IS WORTH EXACTLY WHAT YOU PAY FOR IT!Dial Arc 250HFThunderbolt 225 AC/DCAssorted A/O torches
Reply:I was also thinking the original looked bumped in a brake vs rolled.Roger if I understand the process you describe correctly, he needs access to the back to support the work with a dolly while he works the welds correct? I think he's trying to avoid taking the interior down if possible.My guess is the easiest way will be to take what you put on off and redo it vs taking down the inside, but then I don't do a ton of sheet metal work..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by DSWI was also thinking the original looked bumped in a brake vs rolled.Roger if I understand the process you describe correctly, he needs access to the back to support the work with a dolly while he works the welds correct? I think he's trying to avoid taking the interior down if possible.My guess is the easiest way will be to take what you put on off and redo it vs taking down the inside, but then I don't do a ton of sheet metal work.
Reply:Hi guys, thanks for the replies. Part of the interior panelling has been removed as it was installed in sections. The reason I wanted to avoid heat was the fire issue with this old stuff which is 1960's vintage, and being that old it also tends to crumble when you disturb it!I'll try what Rog02 has suggested before I take the plunge and cut it out. I'm really disappointed with myself on this project.Andrew.Regards, Match> Cigweld WeldSkill 170 inverter