View Full Version : Motorcycle tank dent
01-20-2005, 05:47 PM
I've got a picture of this in the gallery...somewhere. This is a Fatbob Harley gas tank the seller said, "Has a little dent. Won't take nuthin' to fix it." Still worth the money, but I have to fix it.
This side tank will be a false tank and only house some electrics, so I will be cutting the back out anyway. Any suggestions on pounding it out? All I know to do is pound a while and tap a while, until it smooths out. Bondo the rest.
Anybody got comments? Besides calling me a "Sucker".
01-20-2005, 06:02 PM
This is Steves tank.
01-20-2005, 06:06 PM
OOH OHH I know. You get one of those 'pops a dent' things that you see on TV right??? :lol: :lol: :lol: :lol:
Sorry, the commercial came on TV just as red the post and I coudn't resist, PLUS IF YOU ORDER NOW, you get the free paint scratch eraser!
01-20-2005, 06:53 PM
Just do it like the really high end bike builders like orange county choppers and put an inch thick layer of bondo on it.
01-20-2005, 07:09 PM
Thanks to Nortonscustom, Kerry has a cruel side, and maybe Kustomizingkid is on to the answer.
So...pound and tap, bondo?
01-20-2005, 07:13 PM
Don't feel bad, at least you knew what you where getting. Tip: never buy tanks in primer :!: . I bought swap meet fat bobs once that looked good, they were primered. I inspected best I could through the filler hole, didn't see anything.... We'll guess what, bondo and dents everywhere. Worse yet, 17 holes drilled for a screw type dent puller that did little to remove the dents. Then they brazed up the holes :!:
After some expected ribbing from my buddies, I was going to chuck the tanks into the dumpster. I changed my mind. I cut the inside off and repaired that tank...lots of metalwork, could of bought about six sets of new tanks if I was paid for the time I spent.
But I wasn't letting it beat me :twisted: :twisted: . Those tanks have been on my FLH for 14 years now. Time to change the color :) .
That tank's not that bad, should be easy to fix seeing how you plan to cut the inside off anyway. Lots of info on Metalmeet on knocking out dents. Looks like someone tried to work that dent through the filler hole. That's possible also, but you need to be carefull not to wreck the filler neck.
There were some recent posts regarding cutting and welding on tanks that had gas in them, (may be others), that maybe you should read. Don't know how to post the link, theyr'e under the forum: "Custom sheetmetal work for motorcycles"; topic: "Gas tank strech tutorial?".
01-20-2005, 07:20 PM
Thanks Ernie. I'll head that way. I figure I can knock most of it out and bondo really won't be a big deal, but, the experience could be good. Need to learn something new.
01-20-2005, 09:48 PM
Silver smiths use something called a snarling iron to remove dents.
and I quote:
Snarling: The embossing from underneath or inside an object with a long-armed steel tool, with one end placed in a vise. Snarling is accomplished by placing a form over the snarling iron's tip (which may be any shape) and tapping the back end of the arm which is secured in the vise. The vertical vibration that results gives a "kick," raising a bump on the outside of the object. This technique is usually used in conjunction with chasing.
basically it is a dolly welded or mounted on the end of a stiff springy support.
The dolly is positioned behind the dent. Pressure applied and the springy support arm is struck with a hammer causing it to "Snarl" against the inside of the object. It ain't fast, but then taking stuff apart and putting it back together is often slower.
01-21-2005, 09:33 AM
Gene is on to the fix here.
I've used a similar method to fix some boxed rocker panels.
Grind and polish a high crown dome on a piece of 1" bar and attach it to another fairly heavy bar at right angles. You will probably have to bend your support bar several places so you can maneuver it all around the area just behind and inside the dent crease. With the dolly as support, work the dent creases with a slapper and the dent will move out. When you are done your going to have some stretched metal that you can take care of with a shrinking disk.
Take some picks as you go and let us see how you make out.
Thanks, this is very timely. I was called yesterday to come look at a Honda tank a friend is fixing. He wants to see if I can knock some dents out of it. I haven't seen it yet, (tonight I will), and will decide if I can take on the project. In my gallery, there are a couple pics of a 1926 Douglas motorcycle that he wants me to fix also, but I don't really want to at my experience level. The Honda, I might try, for obvious reasons. Can you guys tell me what material to make the bar out of? i.e. "springy" material I've been thinking of making this type of dolly to reach inside the filler neck, but the idea of this springy thing sounds interesting. John v.o.
01-21-2005, 12:57 PM
oil well pull rod might be a good candidate if you can find some scrap yard handling it up there.
I am told that it is usually something like a 1080 steel. I use it to make tools. It is water hardening.
01-21-2005, 01:18 PM
What about those stud welders that you you a dent puller on? Welds a copper plated stud to the metal and your dent puller grabs the stud.
Jeff that's what I was going to recommend..... I have one and they work out great for dings like that! To bad I'm not in Texas or I'd offer to let you use the thing Steve.
01-21-2005, 03:00 PM
Before using the stud welder, you should consider that the tank has contained gas :!: It MIGHT explode if you weld on it :shock:
Looking at the position of the dent, I would use a bent pick tool through the filler hole
If you want to use the dent puller, I think it would be a better idea to tin solder washers to the dent, USING A SOLDERING BIT, NOT A TORCH.
Attach a small hook to your dent puller and pull the dent, using the holes in the washers.
I guess I'm taking for granted the obvious..... flushing out the tank first.
Was under the impression that people on this forum were a little smarter than that and it really did not have to be explained in detail......My bad.
01-21-2005, 03:42 PM
Sorry if I offended you. Certainly didn't mean to :!:
Just had this thread on my mind :D
Welding on gas tanks!
What would you use to flush the tank :?: Water won't do the trick :!:
01-21-2005, 05:20 PM
A few years ago I had a buddy that had just got his tins back from the paint shop. In his rush to unwrap the tanks to show his wife he dropped one half on the corner of his deck.
After bending a rod everyway I could think of to go thru filler neck I was still unable to do much with the dent. So I ended up drilling a 9/16" hole in the back side of the tank directly across from the dent. Then turned a piece of plastic with a slight radius on one side and a 1/2" pocket on the other that was just small enough to fit thru the filler neck. I then stuck a 1/2" rod thru the hole and spent the next hour trying to get the rod stuck into the hole I'd drilled in the plastic slug. While I was doing that my buddy cut out a dish in a chunk of 4"X4" with the profile of the fat bob. I then slowly worked the dent out by hammering on the rod while the tank sat on the 4X4. After it was all said and done there was surprisingly little damage to the paint and where the hole was welded shut will never be seen.
I'm sure there's plenty of better ways to go about it but that got the job done.
01-21-2005, 05:30 PM
hey guys, why not try a stud gun that the body men use, no hole to fill. gary
01-21-2005, 07:05 PM
01-21-2005, 10:26 PM
Safety is probably the best thing to never take for granted, although we do it every day. Case in point the time I was leaving for a ride and everyone was waiting and I discovered a broken muffler mount. In my hurry, I rubbed the area with some sandpaper, taped the muffler and pulled the trigger on the mig. A resounding explosion resulted when the fumes in the battery hose exploded......I was just lucky that the battery didn't explode.
Was I smarter that that?....I thought so.........guess not..........john
Thanks, Gene, I have access to mountains of "oil well pull rod", which is, I assume, what we call sucker road here. Hooks onto the head of a pumpjack, many links go downhole and hook onto the downhole pump. I'll try some of this. What do you mean by water hardening? I made a slapper last week from a leaf spring, after I finished bending it, walked out of the garage, -38* Celsius, and stuck it in a snowbank to keep the hardening in it. Shows you how much I know about steel and its properties. Walked back into the garage, dropped it on the garage floor, and it broke right in the middle of one of the bends. Should I have doused it in oil, instead of a snow drift? Does that keep it hard? Anyways, I made another, and let it air cool, and have been using it that way. John
01-22-2005, 12:35 PM
I've used the stud gun on tanks a few times, drain the tank and flush with water and a touch of Dawn several times, let air dry a day or two, and when you use the gun heat just enough to hold the stud, not red hot. Work from the outside in and don't try to get all of the damage out at once, work it slowly. I know that HF and Eastwood sell the guns, maybe even JC Whitney? Also when removing the studs baby the grinder as not to thin the steel much. Cutting the tank would work well, but one pinhole in the weld and you have a leak.
Good luck, Phil Gilmore (rookie)
BTW: If you had bought a reproduction tank
you would have had to bondo all the
forming marks out of it. Nothing wrong
with old stuff.
01-22-2005, 12:44 PM
Hi John, I made a set of tucking tools the other day, did all the welding, bending,ect, then heated them bright cherry red with a rosebud then threw them in a pan fill with Rotella truck oil that I liberated from work. I agitated the pan until cool, they went from red to pitch black with some scale on them. Did I do it correctly, I don't know but when you strike them they ring. They seem to work well enough, so who knows.
01-22-2005, 12:46 PM
yeah in that it broke, I'd say that was oil hardening.
Actually when I go to the spring shop they have tanks of oil for quenching their springs, so I would guess that most if not all car springs are oil hardening.
As you noticed your slapper got brittle when you quenched it in cold cold water.
Springs are usually tempered back from brittle by reheating them to somewhere between 450 - 500 deg. farenheit something you can get out of the oven. Just volunteer to make the pizza and preheat the oven to 500 for 10-20 min.
The sucker rod is probably water hardening. I know mine is.
Thanks, Gene. I just finished 3 days off, and fixed the Honda tank for my friend. He dropped it off, and I stared at it for a long time, until he called to say, by the way, did I mention I stuck a propane torch into the fill and drain and rust holes for a while to make sure it wouldn't blow up in your face. Man, has he got guts. Actually, he steamed it out first. Anyway, I took your suggestion, and cut the end off a tire iron I bought to make a tucking tool out of. Rounded the end off slightly, to take all sharp edges off it, then tried it several ways in my vise. It seemed to work really good when I put it slightly diagonal, so there was only about an inch of the tire iron pinched in the vise jaws. Then fed the "dolly end" through the various rust holes and filler neck and knocked out a large dent, and a few small ones. I had about 6 or 8 inches on each side of the vise jaws, and when I hit the opposite end of the tire iron, it gave a fairly good reaction on the other end. You are right, it is a slow process, but it did work. Took me 9 hours to cut out the rust, make new patches, and knock out the dents and shrink down the high spots. (Man, am I ever falling in love with my shrinking disc) It still needs a very small amount of bondo in a couple areas, but my skills are improving. Thanks, guys. John V.O.
02-10-2005, 05:00 PM
i know it's not metal working,per say but a good trick for gas tanks dents on bikes is to fill with water and cap it off, put it in the freezer and let mother nature stretch it out for you..it'll do a lot of the big stuff with little more than finishing left.not glamorous but it works.
02-14-2005, 08:47 PM
I remove dents in motocross exhaust pipes by using pressure from a inert gas (nitrogen) and heating with a oxy/acet torch. By slowly heating the dented area I able to return a dent to its origional shape. Never tried to remove a dent in a gas tank but I'm sure it will work. You will need to seal the tank and be able to run the inert gas into the tank. But before you attempt I recommend you clean the tank by either taking it to a radiator shop and having it hot tank in their caustic bath or rinsing it out with muriatic acid. Eliminates the boom factor. I like to pressurize at about 60 psi seems to work for me. I like to hammer the outside of the dent with a good body hammer while heating the inside of the dent. Brings the low up and my high spots down. I work in concentric rings working from the outside to the inside. done many motocross pipes for my older brothers this way.
02-14-2005, 09:00 PM
Hi Frank, Welcome to MetalMeet. Thank you for your post. We like to hear from new people. If you get a chance, try going to this forum http://www.metalmeet.com/forum/viewtopic.php?t=750 and tell us a bit about yourself, projects, etc.
Thanks again for posting..........john
02-14-2005, 09:07 PM
Hello bohemond (insert name please), Welcome to MetalMeet. Two new members in a row on this tread.
Guys, sometime we are slow in welcoming you, but don't let that stop you. Check out the forums, the gallery, and ask questions. We are all here to learn from each other.
If you have a specific interest, do a search for it, you may find tons of info..................later............PS check out the above post and do an intro............john
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