Author Topic: fixing tank dent? (Read 2005 times)

chase2034 · « **on:** August 27, 2011, 11:50:50 PM »

I have a couple very minor dents in my 73 cb750 tank. My neighbor says he knows a guy who can repair the dent by shooting pressurized air up in the tank to "pop" out he dents. Of course with the petcock off and no fuel in the tank.

Anyone heard of this? Does it work?

dhall57 · « **Reply #1 on:** August 28, 2011, 12:15:29 AM »

hit the search name 3rd from the left and fined out more info about this before you do anything. I have a golf ball size dent in my 750K6 tank, but the rest of the tank is in such good shape Im hesitant to try to do anything. I.ve heard you can ruin a good tank by doing what your talking about. To much air pressure and and your tank is junk.

trueblue · « **Reply #2 on:** August 28, 2011, 04:21:02 AM »

It can be done, I have watched my old man do it to a few tanks over the years, but too much pressure and the bottom spreads apart and you might as well throw it away, it takes suprisingly little pressure to achieve the result, but it only works if the metal hasn't been kinked and is a smooth dint.

70CB750 · « **Reply #3 on:** August 28, 2011, 05:15:15 AM »

I have one or two in my tank too, I was planning to take it to a friend's body shop. There is a way to pull dents consisting of welding a piece of wire on the dent and yanking it with sliding hammer. That takes care of the majority and than you just use the car body mud and sand it over.

Kevin400F · « **Reply #4 on:** August 28, 2011, 06:08:15 AM »

There are dent-puller gizmos where you glue a plastic shoe with a threaded stud to the middle of the dent with "hot glue" that doesn't damage the paint, then you use a "bridge" that spans the area and pull against the dent using a twist-knob on the threaded stud. Look up "Ding King" on the web. If there isn't a crease at the base of the dent, this method often works.

Kevin

octagon · « **Reply #5 on:** August 28, 2011, 01:08:38 PM »

what about dry ice? there are some videos on youtube showing chilling the metal to cause shrinkage which makes the dent come out. has anybody actually tried it?

lrutt · « **Reply #6 on:** August 28, 2011, 01:14:29 PM »

Do NOT use the air trick. You will be sorry. Speaking from experience here.

I had a 70 Triumph I was restoring with original paint on the tank but a real nasty dent from the broken steering lock. I found a local 'dent wizard' guy who had done some bike tanks. He worked it out for $100 and saved the orignal paint. You can't not tell where that dent was at all. Absolutely amazing. it was big, deepn and well defined from the fork tube hitting it. It was oposite side of the tank opening and forward and down. He did it all through the gas cap opening, made a special tool and just worked it out.

Raef · « **Reply #7 on:** August 28, 2011, 01:42:23 PM »

i wouldn't do it with air pressure, it pushes against everything equal and the weekest spot moves and it probably wont be the dent.

KingCustomCycles.com · « **Reply #8 on:** August 28, 2011, 04:01:53 PM »

So how exactly does air pressure render a tank useless? I have put 100 psi in them and sealed it off with no damage. I was attempting to remove a dent that, of course, did not come out with the air and the aid of a suction cup plunger. A slide hammer and soldering the holes closed worked great.

Kevin400F · « **Reply #9 on:** August 28, 2011, 04:11:50 PM »

Come on now, King......100psi? Really?

Are you willing to do it again to your favorite tank, with video posted up on here?

Kevin

Raef · « **Reply #10 on:** August 28, 2011, 04:17:45 PM »

I have no reason to disbelieve the king but I have built and repaired many tanks. I pressure test with air and most start to swell like a balloon around 30psi and many loose there religion around 40-45.

I use around 10-15 to check for leaks

Gordon · « **Reply #11 on:** August 28, 2011, 05:51:37 PM »

Just because the regulator is set to 100 psi doesn't mean that's how much is going into the object at the other end of the hose.

KingCustomCycles.com · « **Reply #12 on:** August 28, 2011, 06:40:28 PM »

I will ask again, how does it damage the tank, exactly? I see them flex, I see them bounce back, I see nothing permanent. BTW 100 psi on the guage at the compressor is about 97 psi at the spray nozzle.

Raef · « **Reply #13 on:** August 28, 2011, 07:12:01 PM »

My concern would be for one safety more so than intergity of the tank. I have split a tank with air, one could loose their hearing or their sight in the split of a seam.

The tank can be fixed, eyes and ears, not so much

Raef · « **Reply #14 on:** August 28, 2011, 07:25:06 PM »

If it takes roughly 8 sq ft of metal to build a tank and you put 100 psi in said tank there is over 115,000 lb's pushing on the surface of that tank, trying to destroy the tank and kill you.

I don't trust a 30 year old tank, do you

chase2034 · « **Reply #15 on:** August 28, 2011, 07:35:21 PM »

im still debating what to do. ill try the ice method first just for the hell of it. ill post any results in the upcoming weeks.

splitt · « **Reply #16 on:** August 28, 2011, 08:02:16 PM »

I have seen damaged tanks from the pressurized air method. I've also seen thicker tanks come through unscathed. The dents were still there afterward though. Dry ice may work on thin metal tanks on a flat area or on singular bends. If the dent is on a thicker tank, or on a compound bend, they will probably need to be pulled out. Or, just use body filler and repaint it.

Gordon · « **Reply #17 on:** August 28, 2011, 10:04:26 PM »

Quote from: KingCustomCycles.com on August 28, 2011, 06:40:28 PM

I will ask again, how does it damage the tank, exactly? I see them flex, I see them bounce back, I see nothing permanent. BTW 100 psi on the guage at the compressor is about 97 psi at the spray nozzle.

I think the main concern would be for tanks with a good finish that needed to remain unharmed. Inflating a tank can cause it to spread outwards from the middle, like lifting your arms from your side. This could hurt the paint at the main flex points. It could also split a seam at any weaker points.

I'm not talking about the pressure differential from the tank to the end of the hose. If I have my compressor regulator set at 80 psi when I go to inflate my tires, it doesn't automatically inflate them to 80 psi. It would, though, if I had the compressor turned on and left the hose attached until it reached equilibrium. Is that what you're doing with the tanks you've pressurized to 100 psi?

Retro Rocket · « **Reply #18 on:** August 28, 2011, 10:19:59 PM »

Quote

It could also split a seam at any weaker points.

Exactly

I have seen the end result of compressed air in a tank and it blew the seams apart and also stretched the metal, making the repair more costly. I know a few guys over the years that repaired tanks and NONE of them recommended compressed air, actually quite the opposite. I think if you knew exactly how much air was needed , had the tank all strapped up and supported then i would possibly try it.
I have also heard of the heat and dry ice method but never actually seen it done, you would have to be careful that you didn't shrink or expand it too much or it could make the repair worse. I have seen heat used to "try" and fix a truck door and the end result was a crease from one corner to the other. What ever method you attempt, make sure you research it well. King, 100psi would completely screw a tank, feel how hard a tyre is with 40 psi in it.

ronnie · « **Reply #19 on:** August 29, 2011, 12:17:47 AM »

Try this little trick...

Well I tried to post a link but apparently I can post external links. So go to Google and search for "repair a dent with canned air wimp(dot)com"

Kong · « **Reply #20 on:** August 29, 2011, 06:10:44 AM »

I've done the air in the tank trick a couple of times and never had a problem with it, but you have to be very very careful not to blow too much in - and it doesn't take much. I did blow the bottom out of a Honda Rebel tank doing it once, but a couple of good bangs with a hammer down inside the tunnel beat it back to where it was supposed to be.

You can't use the air trick on many dents, for instance of one has a crease or covers an area with two perpendicular curve lines. However from the sound of the original post these dent's aren't real deep. There's a better way than air to do most of them. What body shops do is weld studs onto the dented surface and then pull the dent(s) out with them. Once the dent is pulled you just hit the studs with a grinder and clean them right off - nothing to it. Problem is you probably don't have a stud-welder. So take the tank down to the local body shop and ask them to stick a couple of studs on it for you. They shouldn't charge you more than a couple of bucks a stud. Oh, and just like you have to take it easy with the air if you try it, you also have to take it easy on pulling the dent out with the studs. Start on the outside and work your way around and toward the center - remember in all body work tap, tap, tap, tap, tap not BANG! BANG! BANG!

octagon · « **Reply #21 on:** August 29, 2011, 06:27:06 AM »

those guys in the wimp.com video sound so surprised and thrilled when the dent comes out that you can't help thinking it doesn't work most of the time.

ronnie · « **Reply #22 on:** August 31, 2011, 03:06:40 AM »

Yea, I have always wanted to try it, but I don't have anything to do it to haha.. It's worth a shot before you try and pressurize your tank. I haven't done that either.

News:

Author Topic: fixing tank dent? (Read 2005 times)

KingCustomCycles.com

KingCustomCycles.com