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Old 07-14-2022, 09:01 PM
David Ward David Ward is offline
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Default 8 feet of low crown welding help

Hi all,
Iím replacing the lower half of a 1960 Cadillac qtr panel and need advice on the steps involved. First off, the lower part is made in three sections, front qtr, wheel well, and rear qtr. all panels are built with 19 gauge steel. The plan is to use a Victor J-28 with a 0 tip. Would it be best to weld and planish the three lower sections together, then fit this whole piece to the car, and tack and weld? Or do each panel independently then do my vertical welds last? Access to the back side is about 95% since the inner panels are removed.
Thanks for any ideas,
Dave
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Old 07-15-2022, 08:20 AM
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Kerry Pinkerton Kerry Pinkerton is offline
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I'd do them one at a time. Even a tiny alignment error will be magnified over 8 feet.
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Old 07-15-2022, 10:58 AM
David Ward David Ward is offline
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It sure would! That makes a lot of sense.
Im just trying to walk through the process in my head before welding starts.
Thanks for the advice.
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Old 07-15-2022, 01:27 PM
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Iíve found that one straight weld is normally easier to contend with than multiple perpendicular welds. IF you can accurately locate the three panels, IF, and then accurately join the two vertical seams, it may be easier to planish out the distortion there while the panel is off the car. Then have one continuous horizontal weld to deal with, which should be up high enough to be in your 95% access area.
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Old 07-15-2022, 01:57 PM
crystallographic crystallographic is offline
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Quote:
Originally Posted by MP&C View Post
Iíve found that one straight weld is normally easier to contend with than multiple perpendicular welds. IF you can accurately locate the three panels, IF, and then accurately join the two vertical seams, it may be easier to planish out the distortion there while the panel is off the car. Then have one continuous horizontal weld to deal with, which should be up high enough to be in your 95% access area.
I agree 100%.

Also - I do not mind welding "square corners" on aluminum bodies.
Steel sheet, on the other hand, is not pleasant when welding square corners.
Like Robert so accurately says, do the three lowers into one, and weld that whole nice piece onto the upper.

(Get the 3 lowers to line up, scribe 'em to each other, trim and dress edges for NICE fits - tack first to middle, hammer tacks out, skip weld and hammer each when warm and then weld and hammer each remaining skips, doing that seam, fully, and hammered smooth.
Then on to last, joined to middle, same way.
Make all 3 nice into one long nice.
Then - hang that long one in place, fit, scribe, trim, finesse the edges, ...
Tack Where You Can and hammer a few tacks at a time....until whole length is tacked and hammered smooth.
And etc - avoiding the giant pitfall of "accumulating errors" ...
Slow/careful is fast enuf.
Good Luck!!
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Old 07-15-2022, 06:34 PM
David Ward David Ward is offline
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Thanks Robert and Kent,
The square corners are what Iíve been trying to reconcile, mostly. This is good food for thought.
I ďcouldĒ tack everything on, then weld and planish the verticals, then weld the long seam last. But somehow though, I could see that twisting the tacks causing nightmares. It would probably be ok if I was using a MIG.
I like the idea of working it off the car though, so Iíll most likely go that route.
Thanks for the help, Iíll post pictures when Iím into it,
David
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Old 07-16-2022, 10:42 AM
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Yet another potential method (from a MIG user who does not hesitate to use square corners) would be to fit then weld / planish / grind, joining the two shortest sections first ( probably middle and front) but not attaching them yet. Just making them one piece.

Then fit the rear piece. At that point, you'll have a better idea where your comfort zone is and can decide which is the lesser evil- making it all one off the car or having one vertical joint to do on-car.

If initial fit up indicated joining the rear section to the middle first instead is best, go with that. Or, if the wheel opening section is more than mildly inaccurate, attaching the front and rear pieces to it then cutting over the wheel for a two piece part which meets there could be considered if helpful.

I believe that the option of joining only two sections off the car allows a balance of best "catch and correct" room / time and degree of difficulty / technical correctness and flexibility once the repair is underway. The decision whether to join all three pieces before attaching can be made after perfecting the first two is all I am really saying.

I did a 60 Biscayne and full length lower quarters were available. I did a 67 Impala and those join over the wheel. Three pieces sucks. Just maybe not as bad if you join two first and go from there.
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Old 07-16-2022, 01:12 PM
crystallographic crystallographic is offline
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Originally Posted by drivejunk View Post
Yet another potential method (from a MIG user who does not hesitate to use square corners) would be to fit then weld / planish / grind, joining the two shortest sections first ( probably middle and front) but not attaching them yet. Just making them one piece.

Then fit the rear piece. At that point, you'll have a better idea where your comfort zone is and can decide which is the lesser evil- making it all one off the car or having one vertical joint to do on-car.

If initial fit up indicated joining the rear section to the middle first instead is best, go with that. Or, if the wheel opening section is more than mildly inaccurate, attaching the front and rear pieces to it then cutting over the wheel for a two piece part which meets there could be considered if helpful.

I believe that the option of joining only two sections off the car allows a balance of best "catch and correct" room / time and degree of difficulty / technical correctness and flexibility once the repair is underway. The decision whether to join all three pieces before attaching can be made after perfecting the first two is all I am really saying.

I did a 60 Biscayne and full length lower quarters were available. I did a 67 Impala and those join over the wheel. Three pieces sucks. Just maybe not as bad if you join two first and go from there.
B ... b ... bu ... buut .... his welding method is already chosen (Not Mig)
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Old 07-16-2022, 01:56 PM
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Its the joining two sections then deciding about the third which was my input.
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Old 07-16-2022, 05:12 PM
David Ward David Ward is offline
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Thanks Drivejunk,
Good idea, too. The center section is 24Ē long, so your idea would work well. Put two together and fit it up. Iím sure that would happen anyway to see where I was in relation to the third section. As far as MIG welding, Iím not opposed to it, itís just I donít like how hard the weld is for planishing. Iíve seen a guy tack with mig, then weld with gas. Iíve never tried it, but I might try it on a test piece.
Glad I have those light weight hoses for a long weldÖ.
Dave
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