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  #31  
Old 07-26-2018, 06:14 PM
orwell84 orwell84 is offline
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Originally Posted by crystallographic View Post
Pinpoint shrinks are done with a sharp, hot (oxidizing) flame.
Point the torch flame straight down (90deg to panel) and with the inner cone a nickel's thickness away. Count one-two, and pull flame off and hit the metal with the flat-faced hammer. (Hold the hammer and torch with the same hand - the torch won't mind the bouncy ride, if the pressure is right.)
Back your work with a 2" thick block of wood, about a 4" X 4" face. This avoids stretching, and adds a romantic aroma to the shop.
Remember that the metal keeps shrinking until it is ALL the same ambient temp. I have measured for this, many times.
Hammer until the metal is only warm to the touch - then wipe with a wet rag - no hissing allowed, just steam.
Thank you, I have a great excuse now to get some oxy/acetylene tanks and pull my torches out of storage. So much you can do with them compared to MIG.
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  #32  
Old 07-27-2018, 02:30 PM
crystallographic crystallographic is offline
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Originally Posted by orwell84 View Post
Thank you, I have a great excuse now to get some oxy/acetylene tanks and pull my torches out of storage. So much you can do with them compared to MIG.

True, MIG does one thing pretty well at the low end: stick steel parts together.
But doing auto repairs, I think, requires a good variable-range heat source.
At least for making espresso, cooking sand dabs and warming tortillas, anyway.
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  #33  
Old 07-29-2018, 02:18 PM
orwell84 orwell84 is offline
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Still trying to sort out the patch. It is very hard to work compared to the rest of the panel. I tends to stay a low spot and when I stretch it out it gets lower unless I really stretch it out and pull it out with a stud. Then it is a high spot. I can shrink it back down, but as it gets closer the surrounding area starts to sink too. I have also tried to work the panel around it. Part of the problem is that it is hard to get a dolly behind it. I have considered putting a relief cut in it so I can shape it better to match the rest of the panel. My other option is to weld in a new patch after working the area around it as close to contour around it so the shape of the patch is a better fit to start with. The rest of the panel has been pretty easy and predictable to work.

Thanks for bearing with me.
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  #34  
Old 07-30-2018, 06:53 AM
Oldnek Oldnek is offline
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James!,

Just a thought, Have you tried to strip the whole door, to to see if there is any filler lurking under the paint. Could be possible that there is further repairs done and giving you grief in the target area.
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  #35  
Old 07-30-2018, 11:23 AM
orwell84 orwell84 is offline
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James!,

Just a thought, Have you tried to strip the whole door, to to see if there is any filler lurking under the paint. Could be possible that there is further repairs done and giving you grief in the target area.
Yes. Thank you. There isn’t any. I am in the process of welding in a new patch. I think the panel was not worked out enough when I welded it in “locking” the panel in the flatter shape. The patch may have been too small to stretch enough to raise the panel to the correct shape. The key to getting this panel into shape seems to start with getting the patch into contour first.

This is the last thing I’m going to try. If I’m still not getting anywhere it’s time for another door.
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  #36  
Old 08-04-2018, 01:05 PM
orwell84 orwell84 is offline
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primer door 2.jpgI was able to find a used door in good condition. Sometimes you have to move on and focusing on one thing too long can become an obstacle to making any progress.

I am still working at it from time to time. I put some primer on it to help find highs and lows. Basically the panel was very overshrunk to the point where it was hard to identify the original shape. Welding in a new patch showed me how much weld shrinkage is amplified in changing the shape of a crowned area as well as any type of shrinking on that kind of shape. I have also learned that shrinking is very quick and easy to do, compared to the time and effort it takes to stretch and raise a shrunken area.

So basically I have a lot of stretching left to do. Even some of the high spots in my photo are probably still below the original contour. I am just going to work at this once and awhile and use it as a learning experience. My plan is to raise the panel mostly using a Martin slapper I just bought, smoothing out the highs and lows as I get closer. I will probably end up having to do some very selective heat shrinking at some point, but only after I'm sure the remaining high spots are really high spots.

Thanks for reading
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Last edited by route56wingnut; 08-05-2018 at 09:10 AM.
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  #37  
Old 08-30-2018, 08:41 AM
orwell84 orwell84 is offline
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Iím happy to say that I eventually sorted out my door and got rid of the oil canning. I made a lot of errors in working on the door but I think it came down to misreading what the correct shape should be. I was tending to raise the crown too high and overstretching it, when it was actually a lower flatter shape. I had had it close a long time before but lacked the experience to realize it. I think that stepping away from it for awhile also helped. In some ways I was frustrated with myself because it took a ridiculous amount of time. But I think I learned a lot in just observing how the metal behaved and being able to make the metal do what I wanted it to do. I also learned to try things one at a time, to keep track of what I was doing and stop when it wasnít working or when tired or frustrated. Otherwise you end up trying random things in desperation, lose track of what youíve done and just make it worse. A dent can become as big as a barn door if you focus on it too long. Stepping away until you see it as a dent on a car door again really helps. I am glad I saved the door. Itís not great work from metal shaping standards but only required a thin layer of filler to finish. I am glad I tangled with this first. I have the nose of the bus to do next. Another low crown compound panel with stretched out holes from a spare tire mount right in the middle of it. I now know exactly what NOT to do.

Thanks again for all the great help and advice.
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  #38  
Old 08-30-2018, 11:30 AM
crystallographic crystallographic is offline
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Default A process for straightening a damaged steel panel

Quote:
Originally Posted by orwell84 View Post
Iím happy to say that I eventually sorted out my door and got rid of the oil canning. I made a lot of errors in working on the door but I think it came down to misreading what the correct shape should be. I was tending to raise the crown too high and overstretching it, when it was actually a lower flatter shape. I had had it close a long time before but lacked the experience to realize it. I think that stepping away from it for awhile also helped. In some ways I was frustrated with myself because it took a ridiculous amount of time. But I think I learned a lot in just observing how the metal behaved and being able to make the metal do what I wanted it to do. I also learned to try things one at a time, to keep track of what I was doing and stop when it wasnít working or when tired or frustrated. Otherwise you end up trying random things in desperation, lose track of what youíve done and just make it worse. A dent can become as big as a barn door if you focus on it too long. Stepping away until you see it as a dent on a car door again really helps. I am glad I saved the door. Itís not great work from metal shaping standards but only required a thin layer of filler to finish. I am glad I tangled with this first. I have the nose of the bus to do next. Another low crown compound panel with stretched out holes from a spare tire mount right in the middle of it. I now know exactly what NOT to do.

Thanks again for all the great help and advice.

Orwell,
I appreciate your personal review of this learning experience because it brings out the elements needed for success. A few quick thoughts:


Use a straightedge to determine the original undamaged shape/contour, and then keep that contour handy (paper/cardboard/metal/plastic pattern /profile) handy for reference during the job.


Use minimal heats for shrinking, taking the steel to blue/purple is often enough.


Resist the urge to hammer for more than 15 seconds before checking your shape. This keeps your work going in the right direction.


Relieve frustration by taking a walk or doing something else for a while/day/week.


Visualize what you think is the right process and then visualize what steps you are taking. Compare the two and see how you can improve.

Good job,
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