Fixing "Plip Plops"

I started this thread so we can discuss OA welding and techniques and not clog up this members thread on choosing a welding system
http://www.jalopyjournal.com/forum/showthread.php?t=358870

In discussing the benefits of OA (oxy-acetylene) systems I made mention of "Plip Plops". Member Slide had always referred to this as "oil canning" either or any words you use we are referring to the problem of a long panel having a spot that is "loose" and if you push it from the outside it plips inward and stays there and if you push from the inside it plops back out. If you play with it you can sometimes hear the metal making a plip and a plop and that is where my name came from long ago.

The problem is caused by the panel being welded with OA and the heat has "buckled" the panel a bit and we need to get rid of the PP.

My method has been around for years and is still in use today it demonstrates one of the not very often thought of uses for OA systems.

We need to physically shrink the buckled metal to release the tension somehow. You could go back and cut out some welds but that wastes time and money and there is another way.. notice I didn't say an easier way but it is quicker than cutting out welds and starting over.

The first thing you need is two people one bodyman/torch operator and one "helper". The next thing you need is access to the back of the problem area. And a semi- pointed metal tool like a closed panel hook.

When every body is ready and the helper has been given his marching orders and has his pointed metal "thing" in his sweaty hands we can begin.

The bodyman fires up a "Rosebud" tip (just an OA accessory for heating metal) and the team locates the center of the "hole" in the pp when you push in on it.

The helper starts to apply pressure to the center of the pp like he is trying to push the tool through it causing the pp to bulge outward.

The bodyman starts to heat the pp so an area of about a 3" circle gets red hot (now you can see why the helper needs a tool long enough to keep his hands away from the hot meal). The helper should find it easier to push the metal outward and this results in a section of the center of the pp to start to stretch outward like Pinocchio's nose and it keeps getting longer and longer.

The bodyman ***ists the helper by tapping NOT banging with a bodyhammer around the point of the helpers tool trying to bring the nose to a point.

When the nose is sticking out about 2-3 inches you can now stop for a minute and CAREFULLY check to see if the pp is still there or the metal is now stiff and doesn't "give" in the pp area. Use a hammer head or something metal to push on the former pp and if it is gone you are half way there.

If the pp is still there but "Smaller" you need to move either direction forward or backward from the nose about 3-4 inches away and do it again making another nose and usually two noses is enough to remove the most stubborn pp.

Now that the metal has been stretched out into a silly looking nose we need to get rid of the excess metal and we are NOT going to cut it out.

You need one of those body hammers with the waffle pattern on the surface of the hammer (shrink hammer to you technical guys), and a flat dolly (a hunk of metal that bodymen use) to go behind the nose.

Since we are going to heat up the nose again make sure your helper has something that won't burn to hold the dolly against the inside of the nose and the dolly is big enough to cover the hole that the nose left in the inside of the panel.

Then the bodyman heats up the nose to red hot and try to keep the heat on the nose not the surrounding 3"s like before and starting hitting to nose..... this is important....... sideways NOT like you were trying to drive a nail.

The helper keeps gentle pressure with the dolly but not pushing too hard outward to keep the hot metal from being pushed backward but trying to keep the dolly parallel to the rest of the panel.

Use glancing blows up, down, and all around, so the teeth of the hammer grip and slide the hot metal into the surrounding area not inward. What you are doing is shrinking the metal back into place not beating down the nose straight inward.

Once you have the nose back flat with the rest of the panel and it has s****e marks from the hammer stop for a second and CAREFULLY see if the pp is gone hopefully it is. Do this with all the noses you had built and your pp should be gonzo.

Now just let it cool normally or if there is still a little "loosness" you can try putting a wet shop towel right on the hot metal but beware this MAY cause problems of it's own.

Then it's a few swipes with a metal file to check for high and low spots and normal bodywork filling and preparing.

Don't forget to prepare and paint the inside of the panel if it is visible from the outside.

So this is an "Old timers" way of removing PPs and shrinking metal if anyone has another method or question or comments please feel free to join in the discussion.


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Thanks for the info, claymore.

I have to say I have never heard of doing it this way, but there's often more than one way to do things. I may try this next time I run into an oil-canned/plip-plop area. I might ought to practice first on something that doesn't matter, though!

 

Yea it's not too hard and it took longer to write the post than it would to actually do it. The thing that takes a little practice is using the shrink hammer not like a hammer but just brushing the nose sideways and back and forth so the metal flows back into the panel and the pp doesn't come back.

If you have some time please let us know how you go about getting rid of the oil can.

 

Man that post is hard to take seriously with you using PP to describe an oil canning panel. every time I start reading it I can't stop laughing. Guess I just have a dirty mind.

 

Well I guess I could have called it a flopper and had you roflmao.

 

Before we get too much into this topic, I think you have this method incorrectly used, for repairing sheet metal. I know this method works on heavy steel plate, but it is not the right way to fix 19-20 ga sheet metal.
You don't need a rosebud torch to correct thin steel. You can actually correct the problem AS you weld, or finish a seam, and then correct it. Doing it as you weld is physically harder to learn, but easier for a beginner, as the warp shouldn't get too far out of control.
A 3 in. area heated on a piece of sheet metal is really going to do some serious harm!
And the method to correct a warped welded panel is really "unshrinking" the metal on the seam, you are actually stretching a seam that is shrunken by the heat/cool of the weld. If you don't believe it, you can see it, by doing a "cold" hammer on dolly stretch of a welded seam on sheet metal, and fix a warp.
I hate to be so critical, but I would hate, even more, that beginners get the wrong impression of how to fix a warp in sheet metal after welding. Again, good method for thick sheet ( though I think it works in a different manner, or for a different problem there), but not thin!

 

Can't say one way or the other but I taught myself to shrink panels with OA and compressed air (and some hammer and dolly work). Working with small shrinks around and into a stretched area until it's tight. Like I said, I taught myself and it could be wrong.

Pete

 

Chopolds your opinion is your opinion but I and the rest of the crew in a factory dealership bodyshop have used this method many many times on customers cars and it works just fine with no drawbacks or serious harm on regular thickness replacement panels and door skins from the factory.

I have never worked on thicker panels so I can't comment on that aspect.

For your "as you weld theory" we are discussing this phenomenon that happens in the MIDDLE of a long panel NOT at the sight of the welding or seam or what ever you want to call it but in the center of a large panel.

This phenomenon occurs from welding the complete perimeter of a long panel and the warping occurs when the welding is done and the panel cools off.

If it occurred while welding then it would be a simple matter to stop welding and release the tension then start welding again and we wouldn't be discussing this problem but unfortunately it doesn't reveal itself until the welding is complete and the panel cools off.

As to the choice of welding tip you could use a normal tip and do the same thing BUT it takes much longer because once you get one area hot it cools off when you make the heated spot bigger. Using a rosebud lets you heat a larger area quicker and that saves valuable shop time. Why do you consider using a rosebud a problem?

Please feel free to enlighten the rest of us with your method of fixing plip plops in the middle of a long panel.

 

I can't speak for chopolds, but the way my Dad taught me (and I've seen it done elsewhere) is more like what striper talks about.

Here's the method as I've been doing it (and I'm no expert):

1. Use a small nozzle on your welding torch (like a #0 or #00 for a Victor 100 series)
2. Adjust flame to where it's got a very slight feather.
3. Heat a small dot at the center of the area that needs shrinking. (Deciding the spot to shrink requires as much skill as anything I've ever done!) Just get the spot to where it starts to glow red. Many times this spot will pull it self up-or-down in a little pucker since it's expanding as it gets hot.
4. As soon as you pull the torch away, quickly grab your hammer & dolly. In most cases, you'll want a dolly with little-to-zero crown (like the flat side of a heel or toe dolly). Put the dolly behind the hot spot, and hammer around the cir***ference of the hot spot. You can also try to sort of brush the hammer towards the center of the hot spot as you make lots of glancing blows. You're basically trying to sort of smush all the metal molecules back toward one another.

One thing to keep in mind is that when the heated steel cools back off, is that it will contract past the point of it's original size, even without the hammering process. In other words, the end result will be smaller than the original size. This is the basic premise of how shrinking discs work.

This process is kind of slow, but it does work... and one person can do it (though it's much easier if you have one guy on the torch and another ready with hammer/dolly). And when you're learning, going slow isn't such a bad thing!

I've also had some success using a regular hardware store propane torch when I had run out of welding gas.

Claymore's technique does sound pretty aggressive, but there are times when you need a 10# sledge, and times when you need a small dinging hammer. Honestly, the thought of using a rosebud on 19-ga. steel scares me... so that's why I mentioned trying it (several times) on some s**** before I did something like this on something that mattered.

 

Again with the fear of the rosebud. What is it that you guys fear? Using any tip you can melt stuff if you don't know what you are doing but if you watch what you are doing and the color is OK the rosebud is just much faster and saves time (and money). Your method is doing the exact same thing and will work on small tight oil canning but for larger ones my way tightens the panel and then moves the excess into areas to releave the stress.

 

For your "as you weld theory" we are discussing this phenomenon that happens in the MIDDLE of a long panel NOT at the sight of the welding or seam or what ever you want to call it but in the center of a large panel.

This phenomenon occurs from welding the complete perimeter of a long panel and the warping occurs when the welding is done and the panel cools off.


This is where a lot of people have the misconception...the oil can DOES occur because of the weld seam! If you correct the displaced area at the weld seam, you correct the oil canning. This is not an opinion, I've studied this stuff, and practiced it, as well, for over 30 years. In the old days, they used to call it hammer welding. You weld a short seam, then take hammer and dolly to it....first to flatten the bead when it's hot....then you continue to hammer it as it cools, to slightly stretch the area, correcting the heat damage (warping) If done correctly, you need NO filler to have a perfect panel.
Torch shrinking does have it's place, as when a panel gets stretched during collision damage. Though almost all of the pros I know don't use, or recommend using, a "shrinking hammer", the one with the serrated face. Regular flat hammers, or *******s are my choice.
For a great explanation of this process, you can read Frank Sargent's book on "Metal Finishing", for an expanation that tells you the molecular things happening when you heat, hit or hammer metal.

 

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Sorry, gotta weigh in on this one...I used the heat and shrink method as described by Chopolds and Slide for many, (35?) years. I personaly wouldn't even THINK of going near an OILCANNED panel with a rosebud. Heating sheetmetal up that much, and in that large an area would be unnecessary if one applied three small shrinks at predetermined points on the oilcaning panel. Shrinking heated sheetmetal is an actual forced compression of the metal platelets, and first raising, with a pick, and then shrinking a 3" round area, heated red, would cause the metal to crystalize, and the application of a wet rag, or forced quenching, would add to this "crystaliztion", (not the correct technical term, but the only way I know how to describe it). It tempers the metal. (also, maybe the wrong term...) Run a metal file over metal shrink with a wet rag, and you'll dull your file. On the HSLA metal on newer cars, they do not-ever- recommend the application of heat to the middle of the panels, for any reason. You might get away with it on older cars with heavier sheetmetal. I would think if the panel was properly fitted and installed, with a mig welder at least, an oilcan wouldn't occur in the first place. I only dealt with them on collision damaged panels that were hammer and dolly worked into shape, and streched to the point of creating an OILCAN, and requiring "unstretching"...If you're going to use the "rosebud" method of shrinking, good luck to ya...

After reading more carefully. I now see this method was suggested to correct an OILCAN on a NEWLY installed panel! The shops owners I worked for would have had a freakin' HEART ATTACK if I'd gone after a newly installed quarter panel with a rosebud! Sorry, no way, install it properly and fit it properly in the first place, VIOLA, no OILCAN...

Anyway, I guess this just shows there's many ways to do things, and I don't know 'em all, but this is the first time I've heard of this method of correcting an OILCAN. Just one mans opinion...

LATER: AGAIN, AND I CAN'T STRESS THIS ENOUGH, THIS IS JUST MY OPINION. IF SOMETHING WORKS FOR YOU AND YOU GET GOOD RESULTS, THEN USE IT, WE ALL HAVE "OUR WAY" OF DOING THINGS...just didn't want anyone to think I was slamming this guy for doing what works for him...

 

I personally am having trouble visualizing 2-3 inches of heat deflection and then bringing it back with a shrinking hammer. I'd love to see a Utube video.

 

I second that!! I'd like to see the finished panel after the waffle head hammer was done with it

 

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Yea that is a bit misleading what I should have said was continue until the oil can was gone however small a nose you need to build be it one inch or three. Three would be for an extreme case involving a collision damaged panel that needed a lot of work. But the technique would remain the same.

 

What ever method used to repair an oil can is going to require some finishing so what is the difference in hammers. Like I said use GLANCING blows which do not produce horror inducing deep marks on the panel. One is not attempting to pound panels with a shrink hammer you are just moving metal to where you want it. Any marring is usually filled using just a light skim coat which would have been necessary any method used.

 

Please someone enlighten us members why people are scared to use a shrinking hammer. Like what problems does it cause that are different from other metal working tools?

And for the "professionals never use one" quip I guess there are a mul***ude of "eager amateurs" out there because tool manufactures are still selling them and somebody has to be buying them if it's not the professionals.

 

I really don't mean to be insulting here...sometimes my "short and to the point" writing may look like that.
They sell LOTS of poorly made tools, or tools that are made to make a job easier, but not correctly. A shrinking hammer has to be included here. If you do some research....check out the books, videos, etc, by the premier metal working guys (like Ron COvell, Ron Fournier, Sargent, Craig Naff, Kent "the Tin Man", an others) you can see examples of shrinking without a special hammer. And some even come out and say that they are useless. They damage metal as much as they fix them.
You sound like you work in a regular collision shop, and use their methods. That's OK for what you are working on there, and a lot of guys use their methods here on the board, as well.
But there are some of us who are more into metalworking, and really strive to do better and better work on our old car. There are MUCH better methods of doing things that how they teach you at an sutobody course, or in a body shop. They do take specialized equipment, and take much longer to ger the right results, but on our own old cars, why not do it the best we can??????
I've been doing bodywork for over 30 years, I started in my driveway, and realized there was so much I didn't know. I went to work after school, at the shop I researched to be, the best custom shop around. I learned a vast amount there, but even at that, There were miles more to go! Bacj then bodyshops never even heard of MIG welders. John, my mentor, still worked in br***. When I bought a MIG to chop my Olds, he wouldn't go near it! It sat in the shop for a year, before I got the nerve to teach myself on it. Much better method, though.
Much later, TIGs are replacing MIGs, in higher end shops, but often I even go back to gas welding parts, if I think it will do a better job, or if I need the extra heat/hammer time to reshape the panel as I work it. Like putting together 2 different car's panels with different curvatures. Today, I use all 3 methods, depending on the application.
So when I tell you that welding a seam on a panel can "produce" an oil can...and the best method to get rid of the oil canning, is to correct it AT the seam, I'm not expressing an opinion, it's fact. If you've learned in a commercial setting, and you like what you do and want to do it better, you really should look into getting some metal finishing books, or videos. It will open up another world for you! There are a lot better methods of doing things, if you want to do them right!

 

I think that shrinking hammers-much like the various welding applications outlined by Chopolds- have their place. for example, areas where it would be hard/impossible to reach the backside, confined areas, or stuff that is heat sensitive due to placement.

 

Yeah, but in order to work as they are designed (gather and hold) loose/stretched metal, they must be backed up with a dolly/s**** and used "on-dolly". This "process" is known as "cold shrinking". It has little or no use in true metalfinishing, but has been used for ages by "puttyflingers" who never learned how to read and correct damaged sheetmetal, and never could master hot shrinking. This is one of the "blue chip" ***ets in a grocerie store parkinglot gypsy-bodyman's ****nal!

S****ey Devils C.C.
"Spending A Nation Into Generational Debt Is Not An Act Of Comp***ion!"

 

If the panel was perfect before installation and the only change made to the panel was it was welded on the car why would you think the problem was in the center and not around the welds?

Your proccess could be done with a gold plated hatchet and be just as screwed up.

My used car salesman buddy had a car came in with the door skin "plip-plopping" asked him how he was gonna fix it, He said" I'm gonna beat a kink in the center and fill it with bondo." Sounds about like what you described.

 

fair enough, I suppose. I get that You don't like 'em. personally, I prefer a slap file every day of the week. I have only ever used them on the inside of a hail damaged roof (shrinking hammer, that is), and it worked gangbusters.

but, as previously mentioned, several times over, I am not a painter. nor am I a "bodyman". the methods I personally use to get something flat and straight are sometimes straight outta frankenstiens playbook. and I can surely appreciate the skills of a talented bodyman.

 

Guys all well and good for the general bodywork contributions and advice BUT this isn't a general bodywork or mig tig vs OS, or working on old cars vs your own car thread.

It is a thread on one specific question that was asked in another thread and we moved the question to here to avoid spamming up the other members thread.

So if we can keep the posts in here to the question of removing Oil cans and leave the questions like "well it would be better to not have one in the first place" posts to another thread.

If someone would like to open a thread on any of the subjects brought up like doing it better in the first place, panel repair and replacement, OA vs tig mig etc (have a few of those already) fear of tools, putting down of tools and techniques you have never used, or any host of others I would be happy to join the discussions.

How about one like new guy vs old timer technique differences, like I said I'm an old timer and we didn't have some of the cool stuff that is around now like tig and mig and we worked to pay the bills using techniques that were available at the time like OA that is all we had (well maybe stick welders).

Now we get posts like must be some backyard hack and maybe a mud spe******t and I would never do that to my car... well no **** and WTF. Most of the negative stuff comes from not READING the thread and not figuring out what the post was intended for. It was started to answer another members question not start a **** fight of old timers vs new guys and new and old techniques.

Like anything else if you haven't tried it don't knock it, if you want to do it your way GREAT but if you want to knock something please do us the common courtesy of posting YOUR BETTER WAY using OA only not just posting flames.

There has been a couple of posts in other threads about "why are the old ways dying off" Or why can't the old guys p*** on the old techniques like leading, or using OA? Well this post is an example of why old guys just sit back and don't post they don't want the new guys to flame them with general posts about how the new ways are better with no specifics given.

 

As was mentioned, welding the perimeter has shrunk the edges which pulls on the panel creating problems inboard. Stretching the welds and smoothing the surface nearby should be all that is required to fix it.

Shrinking a panel that was straight before it was welded is only going to reduce the surface area further. Shrinking with a rosebud is overkill, but a lot of people use overkill techniques when shrinking. You do not need to distort the surface to shrink.

When shrinking is required, you do not need to heat to red hot, or blue hot. All you need to shrink is have the metal swell slightly, and quench. If you have applied enough heat the panel will steam when quenched. You can do this dozens of times in same spot if necessary without any damage to the metal.

Shrinking hammers are one of the many gimmick tools that have been promoted by tool sellers. Although they can accomplish a small amount of shrink, the cost is very high in surface damage. Friction shrinking, or torch shrinking both work far better and leave a perfectly un-marred surface.

Shrinking files are another "old-timer" tool that I would never use on a panel. There is no reason to mark the surface when there are other superior techniques.

Oilcans are usually caused by over-stretching, and uneven surface tension in a panel. I show a short oilcan repair in my youtube videos below. Not a cl***ic oilcan but the treatment is the same.

John www.ghiaspecialties.com

 

Thanks you, guys, for coming in to back me up! I hate to see misinfomation spread around.

 

John Kelly and chopolds are correct. I too have been in the "craft" for decades and the advice originally offered seems like a fast "fix" vs proper shrinking. I recently had to shrink an oilcan from the 1/4 panel on my bubbletop that was due to improper panel alignment (bought it like that). Like Mr. Kelly said not much heat reqired. I used a MAPP gas torch and watched the panel move just a bit and quenched. The reason was it's over the wheelwell and can't be accessed from behind. 2 shots at it and gone, but I was lucky there as it coulda been worse requiring a cut and re-weld.

Shrinking hammers...another "fix" similar to picking around a stretch. It works but it's ugly and requires fillers. I have one and seldom to never use it for what it's supposed to do.

I just got a shrinking disc a couple years ago after over 30yrs in the game and I find it to be a miracle worker at times.

 

Man I love posts like this to learn from. I am truly a beginner at metalworking, but I find it hard to learn. I have some books on the subject and have tried to read from different places on the net. It is just to hard for me to get it from words. I am just asking if sometimes there could be some videos. I have a lot of dents and dings on my car and I don't want anymore filler than I have to. I really would like to learn how to use OA torch as I just got one from my old tech. teacher.
Matt