Help with crushed rear top cab edge

[SkinnyG]

Can someone with experience give me tips on how to go about repairing this?

Problem: Metal recycling crane magnet hit the cab

I can finish the repair, I just need to know how best to pull the metal back.

Tools I think I need that I have in my possession:

- Stud gun and slide hammer
- Shrinking disk
- Basic hammer/dolly kit
- Oxy-Acetylene torch
- MIG welder



Thanks.

My hat's off to you guys - I hate doing bodywork.

[mongocanfly]

Just adding your other post...in case you get answers there as well..
http://67-72chevytrucks.com/vboard/s...01#post8895401

[tinydb84]

It sucks that it is the roof and you cant work the underside.

Let me preface by staying I'm not a body guy but Ive done a few areas where I only had access to one side. Its definitely doable especially since you have the right tools.

Id focus using the stud gun along the edge of the roof using a dolly nearby. Once that bodyline is in place work the deepest areas of the dent to bring them up while holding the dolly on the nearest high spots. Come over the area with a shrinking disc. Id probably leave the area a bit low and filler the rest rather than try to make it perfect.

[StingRay]

There are glue on tab systems that are very effective for pulling and also spotting systems that can be applied over and over very quickly. Pretty spendy for a hobbyist but they are so effective that it might be worth farming that part of the repair out. Watch Blue collar Kyle on Facebook and it will open your eyes to modern collision repair.

[hugger6933]

I have been rebuilding wrecks since the late 80's. That dent is more like a Walmart door ding. I joke and shouldn't I know this is a sore spot so to speak. I would grind back the area weld some straps into the deepest part of the dent small spot welds or real short stich welds down a plate[ I make each weld plate to conform to the dent] Then attach your pulling device[ Come-a-long comes to mind it works very well] I also many times used one of the arms of my 4 post car lift hooked to a pull plate to pull upwards on a dent, I also have an overhead puller attachment for one of the towers to my frame machine but I know everyone doesnt have those in their shop
Anyway if you can get a plate on there and get something to pull upwards with and go SLOW and easy tapping down the pushed up ridges if any and the side s that are pushed out it will work fine

[franken]

The pdf isn't very good, but it's worth the price. There are a ton of bodywork vids out there but lots are crap. Ones showing shrinking disk use are usually pretty good though.
https://drive.google.com/file/d/0B7w...pPRWloc28/view
Keep in mind that the top of the roof on the two sides don't need much work, in fact the top left side should go back where it belongs as the nasty creases are worked up. It looks like there's a bit of a crease on the top right that probably won't go back w/o some help. It looks like about 1/3 of the way from the right dent is a bit of damage on the arc.
If you read the file in the link it'll say to start with the last bit damaged and work back to the first. In this case I think you'll need to put some studs in the original fold of the roof, apply a good bit of force pulling up, and work the nasty folds at the very back. I'd probably try some hammer, then shrinking disk on the rearmost folds and repeat.
Pretty much repeating what hugger said...

[SkinnyG]

Oh, excellent book; I have some reading ahead of me.

[SkinnyG]

I was able to find a new copy of "Metal Bumping" (4th Ed) locally. Excellent, thank you.

The recycler's will cut me a cheque. They've been very good about it.

Do I place pull tabs like this:



Or like this:



And do I shape the bottom to the valley and tack it where it touches (and then presumably cut the tacks as the parts of the valley come home), or just use a narrower tab and tack it only at one point?

I had fabricated a lever system to try and pull the end up with a metal washer or tab welded where I need it:



But then hugger6933 suggested using a hoist, which I have, so I devised this apparatus:







I really appreciate the input. It still scares me, but less so.

[SkinnyG]

Blue Collar Kyle has amazing videos.

[LS short box]

I had a truck roof repaired by a local a body shop with dents some what like yours. They used a cherry picker in the box to put upward pressure on the dents. They welded pieces of metal to the roof.

[SkinnyG]

The hoist didn't work as well as I had hoped - there is a lot of flex in the arms.

The lever thingie I made worked fairly well, though the attachment evolved.

I also made a slide hammer to pull the metal tabs a bit by hand. Pic to follow.

After about 6 hours (of butt-kicking) I had this:



I can tell that I am progressing, but very very slowly. I could not get the edge where I wanted it to be, I'm within about 3/32 to 1/8" - good enough for kitty hair in my world. Still not falling love with collision repair.

[mongocanfly]

You'll get it...a repair like this is made even harder because of no access to the backside..

[tinydb84]

1/8'' is totally appropriate for filler. Any high spots or oil canning? You can run the shrinking disc over those areas and it might get you even closer.

[Richard2112]

WTH is a "shrinking disc"?

[mongocanfly]

Shrinking disc is a metal disc that goes on a side grinder...
It will shrink stretched metal..
It works by heating up the surface and then you rapidly cool it causing it to shrink..

https://m.youtube.com/watch?v=rt07pLebQwQ

[Richard2112]

Originally Posted by mongocanfly

Shrinking disc is a metal disc that goes on a side grinder...
It will shrink stretched metal..
It works by heating up the surface and then you rapidly cool it causing it to shrink..

https://m.youtube.com/watch?v=rt07pLebQwQ

Thank you. Having never done body work, I've never heard of anything like that. Didn't know it was possible.

Edit: That video was cool. Some skill there.

[SkinnyG]

Follow-up.

I had a friend who does autobody for a living come over and give me some tips. Turns out I've been going about this all wrong, and made quite a lot more work for myself. It's "better" now, but I'll share what I've learned (also for my own reference):

1. Dent removal is in reverse of the dent acquisition - "the first part in is the last part out."
2. The hoist wasn't as useful as I'd hoped.
3. I found the MIG-welded pull tabs a problem - the MIG beads lack of maleability was an issue. I suppose I could have TIG'd the tabs, but I was afraid of putting too much heat in the skin.
4. Using a stud gun to try and "crown" the panel was horrific - it created way more work. Maybe good for pulling a crease, but not for "fine adjustment" at freakin' all.
5. Use a Heat Gun to pull up low spots, cooling with compressed air.
6. Use Shrinking on only the high points, keeping the shrinking disc as flat as possible (this requires modification to my angle grinder to do so), cool with air, not water.
7. Shrinking with a torch is pretty aggressive on a roof skin, and can cause problems if you're not careful.
8. Shrinking with a propane torch can be an issue since it heats up so slowly, you may end up with a larger area than you want
9. The aim to balance all the highs and lows so that the tension in the panel is uniform/neutralized. Defects in the panel affect the whole panel.
10. High crown panels are much more forgiving than low crown or no crown panels.
11. The Heat Gun can help "tighten" the panel so it isn't so floppy.
12. If you come to your wits end, you can apply "Flutter Foam" between the two panels to put some rigidity back into the roof skin.

There might be more, I'll try and add to it later if I remember more.

I'm actually really exhausted from concentrating so intensely on what he showed me. I needed to write this all down, and then let it all stew inside my head for a day.

[SkinnyG]

Spend another day with the shrinking disc and the heat gun. The heat gun trick is freaking magic. I was able to really tighten the roof skin nicely, though I did venture a bit outside the repair area.

Today ended with a couple coats of etching primer, and tomorrow some filler.

[mongocanfly]

good deal..
when i was trying to repair my doors , i was warned about not using a torch...they say you can actually make it worse in a hurry if your not careful
all i used was the shrinking disc...and cooling with a wet rag or air..

[Richard2112]

Originally Posted by SkinnyG

Follow-up.

I had a friend who does autobody for a living come over and give me some tips. Turns out I've been going about this all wrong, and made quite a lot more work for myself. It's "better" now, but I'll share what I've learned (also for my own reference):

1. Dent removal is in reverse of the dent acquisition - "the first part in is the last part out."
2. The hoist wasn't as useful as I'd hoped.
3. I found the MIG-welded pull tabs a problem - the MIG beads lack of maleability was an issue. I suppose I could have TIG'd the tabs, but I was afraid of putting too much heat in the skin.
4. Using a stud gun to try and "crown" the panel was horrific - it created way more work. Maybe good for pulling a crease, but not for "fine adjustment" at freakin' all.
5. Use a Heat Gun to pull up low spots, cooling with compressed air.
6. Use Shrinking on only the high points, keeping the shrinking disc as flat as possible (this requires modification to my angle grinder to do so), cool with air, not water.
7. Shrinking with a torch is pretty aggressive on a roof skin, and can cause problems if you're not careful.
8. Shrinking with a propane torch can be an issue since it heats up so slowly, you may end up with a larger area than you want
9. The aim to balance all the highs and lows so that the tension in the panel is uniform/neutralized. Defects in the panel affect the whole panel.
10. High crown panels are much more forgiving than low crown or no crown panels.
11. The Heat Gun can help "tighten" the panel so it isn't so floppy.
12. If you come to your wits end, you can apply "Flutter Foam" between the two panels to put some rigidity back into the roof skin.

There might be more, I'll try and add to it later if I remember more.

I'm actually really exhausted from concentrating so intensely on what he showed me. I needed to write this all down, and then let it all stew inside my head for a day.

This thread is incredibly helpful. I'm working outdoors on my project and not sure how air movement might affect something like a shrinking disk application. Further I'm not an autobody tech by any stretch so simple repairs would take me an eternity as I walk on egg shells trying not to screw things up. That list you provided and valuable tips provided by others here have re-enforced something I was already aware of: I have neither the appropriate tools, environment or skill level to do a professional job. One small example: I have sanded some panels (my doors) and sprayed them with rattle can primer from the general auto supply store. It looks good or at least, vastly improved. But I haven't any idea of what limits there may ultimately be on the type of paint that will go on my truck, simply due to the type of primer I'm using. Rust-Oleum automotive primer probably isn't the best idea but when spraying outdoors (not having the appropriate environment/tools: compressor, line dryer etc), it seems spraying Rust-Oleum rattle can is at least better than rust. I could be mistaken about that too. I am finding out there is more that I didn't know, than I thought I didn't know.

[mongocanfly]

i did a good bit of my shrinking disc work outside...saw no affects on it....
when i worked a area with the disc , the metal gets hot, and you immediately hit that area with a wet rag or air...

[Richard2112]

Originally Posted by mongocanfly

i did a good bit of my shrinking disc work outside...saw no affects on it....
when i worked a area with the disc , the metal gets hot, and you immediately hit that area with a wet rag or air...

Thanks Greg...these are the types of things I wouldn't know unless someone told me as I have no experience. I can overhaul a differential, transmission and motor but sheet metal is alien to me. Fortunately, my truck doesn't have any major areas of metal creases or deflection (just the typical rocker panel rust) and body panel alignment issues. You've been quite helpful. I'm likely to ask a lot of dumb questions in the near future.

[Richard2112]

Originally Posted by SkinnyG

Spend another day with the shrinking disc and the heat gun. The heat gun trick is freaking magic. I was able to really tighten the roof skin nicely, though I did venture a bit outside the repair area.

Today ended with a couple coats of etching primer, and tomorrow some filler.

That looks like it's coming out well.

[SkinnyG]

I had a really tough time with actual back edge, because I MIG'd it, and MIG isn't malleable at all. I should have TIG'd the pull tabs. As a result I don't have a good shape there at all, and in trying to inexperiencedly fix it, things shrunk and there will be some kitty hair to re-shape it. Life is like that.

[SkinnyG]

While filler on the roof is curing, I had a case of the "whileiamintheres."

Bubbled rust coming through holes in the fender edge:







And honking big cracks in the back. 1/2" bondo here, hiding a garbage repair. Not my repair or my bondo, but I think I can knock it down to 1/4" thick if I go forward about 8" more:









There is a reason I painted this with Tremclad and a roller seven years ago....