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  #31  
Old 02-03-2010, 08:51 PM
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I believe since you're at the edge of the sheet, it will "allow" more shrinkage as there is not material on either side of the weld.
Clear as mud?
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  #32  
Old 02-03-2010, 09:20 PM
TheRodDoc TheRodDoc is offline
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your problem came from poor alignment of all the parts.

This is sometimes very hard to get everything shaped right to get it tacked together.

you have to get both the back part of the roof and front part of roof aligned before the strip is cut. The front and back must sit aligned without the filler strip. use your straight edge or a strip of sheet metal laying flat to check in spots all along the gap from one side to the other. get them fitting just right then cut the filler strip and shape to lay over the gap. on inside mark it for cutting. Then cut and tack in carefully.

Doing it this way everything should end up pretty straight except for the normal stretching of the weld area.
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  #33  
Old 02-04-2010, 10:54 AM
John Buchtenkirch John Buchtenkirch is offline
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Don't want to beat a dead horse here but a question is nagging me. The shrinkage occured only on the radius'd edges, as in my photos, the cenetr of the roof etcetc is fine. What is going on here that i need to be aware of in the future and what preventive steps should i be making. In short, i welded 4 feet without shrinkage and when i came to the curve where the roof wrapped down to the door i had problems, does the curve get tougher or direct the hot metal/shrinkage or focus it somehow? Thanks oj
I would say to consider yourself very lucky , most guys doing that job would end up with multiple oil-can problems on the flat part of the roof. Where you have your problems is relatively easy to correct because the high crown helps to stiffen things up even if the area isn’t absolutely perfect. One reason you could have more shrinkage in the radius area is you’re possibly filling gaps with larger welding rod which required more heat than the welding you did on the flat part of the roof. I’m not a big fan of filling gaps with welding rod, I will spend the extra time to fit my patches to near perfection so hopefully my welds are very consistent which should give me consistent shrinkage on the entire seam.

Pugsy is also correct, you will get more shrinkage right at the edge but it should also hammer / stretch back to shape very easily there too. When I looked at your first photos the entire filled area of the radius looked sunken so I’m with Richard, I have to wonder how well the filler strip flowed with your roof before you started the welding ?

If you can’t get those radius areas to your satisfaction you could always cut them out just outside the welds, shape new patches & weld them in. Or you can just keep hammering and stretching, you do seem to be gaining on it . Have you tried the directional hammering / stretching I had suggested earlier ? ~ John Buchtenkirch


P.S. I will just add that back in the days of hammer welding body men had to learn how to hammer out & level welds. With today’s technology & methods those skills have somewhat faded but here is an example of where they are needed. I’m happy the new technology has come along but the old ways still carry some weight with me. I guess I’m semi old school if that makes any sense.

Last edited by John Buchtenkirch; 02-04-2010 at 10:57 AM.
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  #34  
Old 02-04-2010, 05:35 PM
ojh ojh is offline
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I think Richard is right. When i welded the filler there were no gaps, i tig weld and the backside is a rusty mess so the fit had to be perfect. When i cut the roof it lost all its shape, nothing held it together as Richard surmised. Guess i should have made a frame of some sort to hold the roof.
Either way, i'm having a ball moving metal around and developing my hammer and dolly skills. I don't work on it as much as i should, but i have the passenger door hung now and am working on the windshield header/A pillars then onto the drivers' side. Couldn't have gotten this far without your help and support, thanks oj
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  #35  
Old 02-04-2010, 07:11 PM
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Originally Posted by ojh View Post
I think Richard is right. When i welded the filler there were no gaps, i tig weld and the backside is a rusty mess so the fit had to be perfect. When i cut the roof it lost all its shape, nothing held it together as Richard surmised. Guess i should have made a frame of some sort to hold the roof.
Either way, i'm having a ball moving metal around and developing my hammer and dolly skills. I don't work on it as much as i should, but i have the passenger door hung now and am working on the windshield header/A pillars then onto the drivers' side. Couldn't have gotten this far without your help and support, thanks oj
I see. You should have used the ol hold the floppy roof flaps from floppin trick eh.

I'll remember this when I chop my top.
Always happy to learn from others troubles.
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  #36  
Old 02-04-2010, 10:02 PM
John Buchtenkirch John Buchtenkirch is offline
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Originally Posted by ojh View Post
I think Richard is right. When i welded the filler there were no gaps, i tig weld and the backside is a rusty mess so the fit had to be perfect. When i cut the roof it lost all its shape, nothing held it together as Richard surmised. Guess i should have made a frame of some sort to hold the roof.
Either way, i'm having a ball moving metal around and developing my hammer and dolly skills. I don't work on it as much as i should, but i have the passenger door hung now and am working on the windshield header/A pillars then onto the drivers' side. Couldn't have gotten this far without your help and support, thanks oj
OJ, now that you mentioned that you tig welded that roof I have a new theory, your weld bead was so proud in your first photo I thought / assumed you had mig welded it. I think you need to practice fusion welding on some scrap pieces and just add as little rod as possible. You have a bead built up there like your tig welding heavier plate. Big beads need a lot of heat which means a lot of shrinkage and when they cool they make the weld sink , that is pretty much what you have in the first photo. Now the only mystery now is why is the flat part of the roof OK ???


As far as putting bracing in to hold things in place being a solution --- forget it. What you have to do is tack everything together and sight over your panels (from many different directions) and make sure your panels flow correctly. Lightly grind the tops off your tacks and then you can run your hand over the panels to also check for flow. You want to make corrections in your panels before you weld them in , not after welding.


Finally, I have suggested you use and asked you if you have used a directional type hammer on that sunken area without response. If you don’t understand what kind of hammer I’m talking about I can post some photos. I wouldn’t hit the metal in the rain gutter area with a radial stretching hammer, you could easily lengthen it causing yourself more problems . ~ John Buchtenkirch
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  #37  
Old 02-05-2010, 05:04 AM
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Originally Posted by John Buchtenkirch View Post


Finally, I have suggested you use and asked you if you have used a directional type hammer on that sunken area without response. If you don’t understand what kind of hammer I’m talking about I can post some photos. I wouldn’t hit the metal in the rain gutter area with a radial stretching hammer, you could easily lengthen it causing yourself more problems . ~ John Buchtenkirch
I'm curious as to a directional type hammer.
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  #38  
Old 02-05-2010, 10:03 AM
John Buchtenkirch John Buchtenkirch is offline
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Originally Posted by 123pugsy View Post
I'm curious as to a directional type hammer.
All the hammer faces in the photos are directional stretching but some would be too aggressive for that roof job. Any hammer face that stretches in mostly one direction could be called directional. I personally wouldn’t use a doomed faced hammer that stretches radially on that roof, if you stretch the skin lengthwise in the rain gutter area you’re just creating more problems . ~ John Buchtenkirch

>!1dir1.JPG

!1dir2.jpg>
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  #39  
Old 02-05-2010, 11:31 AM
TheRodDoc TheRodDoc is offline
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There is no such thing as a directional stretch hammer. Those in your pictures are not for that.

Randy and I have both already pr oven that on MetalMeet already. You will have to go there and do a search to find all the posts about that if you want. There was great discussion about this subject.

No matter what shaped hammer face you use no matter if it is square, round, oval, egg shaped, hex shaped or what ever the same amount of stretch is had by hammering the same area with each.

lets say you use one of the barrel shaped faces you show. make a row of hits along a weld area about 6 inches long. you would do the same thing as if you used a smaller barrel shaped hammer face going the other way in the same area.

just like the English wheel tracking in one track over and over again like some here use to pre stretch for a bead roller bead. the whole area that you rolled will rise up from the surface. stretching equally both ways. With your theory it would only get longer. But that's not so.

If you were to hit the sheet metal with out a dollie behing it with the barrel shaped face you showed you would leave a stretched dent the same as if you would have used a round face except that the ends of the barrel shaped hammer would leave sharp dents at only two sides of the dent. but the stretch would be from all directions.

In order to raise a area inside the outer edges of sheet metal the metal has to be stretched in all directions. No matter how or what you hit it with.

hammertracks.jpg
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Last edited by TheRodDoc; 02-05-2010 at 11:35 AM.
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  #40  
Old 02-05-2010, 12:24 PM
John Buchtenkirch John Buchtenkirch is offline
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Quote:
Originally Posted by TheRodDoc View Post
There is no such thing as a directional stretch hammer. Those in your pictures are not for that.

Randy and I have both already pr oven that on MetalMeet already. You will have to go there and do a search to find all the posts about that if you want. There was great discussion about this subject.

No matter what shaped hammer face you use no matter if it is square, round, oval, egg shaped, hex shaped or what ever the same amount of stretch is had by hammering the same area with each.

lets say you use one of the barrel shaped faces you show. make a row of hits along a weld area about 6 inches long. you would do the same thing as if you used a smaller barrel shaped hammer face going the other way in the same area.

just like the English wheel tracking in one track over and over again like some here use to pre stretch for a bead roller bead. the whole area that you rolled will rise up from the surface. stretching equally both ways. With your theory it would only get longer. But that's not so.

If you were to hit the sheet metal with out a dollie behing it with the barrel shaped face you showed you would leave a stretched dent the same as if you would have used a round face except that the ends of the barrel shaped hammer would leave sharp dents at only two sides of the dent. but the stretch would be from all directions.

In order to raise a area inside the outer edges of sheet metal the metal has to be stretched in all directions. No matter how or what you hit it with.

Attachment 2577
Wow, I don’t even know how you could say that ? When I put directional dies (hit point is long and thin) in my Pettingell hammer and run them on a flange or an edge of a panel it will grow / expand / stretch in one direction so fast it’s almost hard to control. All the hammers shown in the photos will do the same at a much slower and more controllable pace. I have a high regard for your opinion --- are we talking about 2 different things here ? ~ John Buchtenkirch
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