Topic: Popping Out Dents by Freezing Tank

[trism18]

Someone told me (from personal experience) that you can pop the dents out of a gas tank by filling with water and freezing it.  It sounds somewhat feasible but I have my doubts.  Has anyone done this or know that it works?  Of course I would not cap the tank during freezing, and I plan to thoroughly clean the tank afterwards... (I purchased an extra tank to try my hand at painting and restoration.)  Thanks for the input.

[stanghater]

never heard of that, i have heard of using dry ice on a hot ass day to pop dents out

[mrblasty]

I think the freezing method may blow out the seams or any thin spots that may be hidden under the paint job, If you were to try it the filler hole would need to be capped really tight to contain the expansion.
I do auto body work and the dry ice and heated tank idea sounds a bit more feasible due to the properties of formed sheet metal.
When sheet metal is dented it stretches at and around the dent, when dent is popped out it leaves a little bit of a blister above its original surface plane. The raised area then needs to be shrunk usually this is accomplished by a technique called heat shrinking.
I have never tried the dry ice trick but in theory sounds better.   Good luck

[Bob Wessner]

I think the freezing method may blow out the seams or any thin spots that may be hidden under the paint job,

I've never heard of anyone doing this, but I have to agree with this statement. How could the ice differentiate between the dent and the rest of the tank? Seems it would exert the same pressure all over the interior surface.

[Raul CB750K1]

Back when I was a kid, when we went out in the field we used to carry our water reservoirs. The better ones was made out of aluminium and covered with felt. By wetting the felt it created some kind of barrier and the water inside the reservoir was cool. Then came the isothermic containers and aluminium reservoir fell into oblivion.

Well, it was just too easy to drop the container and put a dent on it. Surprisingly, the inside was coated -something like POR15  -, I guess to avoid the contact of the liquid with aluminium. An old wive tale was to freeze it up to pop out the dent. I had to try it once, but it was a few days labour. The first freezing only pops out a little the dent, so you have to wait until the ice melts and start over again. The The dent went out, but the whole reservoir inflated like an air bubble. It couldn't stand on a flat surface anymore. The felt cover didn't fit anymore, and the inside coating peeled off. The upside was that the capacity slightly increased...

Raul


P.S. I also read once about something similar but with compressed air -seriously, I heard about it-.

In my opinion the best solution is something like the Ducati Monster: a gas tank with a cover over it. If you drop the bike you just replace the cover. I guess Ducati spares are expensive, but you can always make cheap aftermarkets parts..

[KB02]

In my opinion the best solution is something like the Ducati Monster: a gas tank with a cover over it. If you drop the bike you just replace the cover. I guess Ducati spares are expensive, but you can always make cheap aftermarkets parts..

Yes, Ducati tanks are expensive. When my monster met the pavement and caused almost $3000 damage, the tank ALONE cost $1100. Thanks God for insurance.

As for the filling-the-tank-with-Water trick: I think I'd avoid it.

[Geeto67]

When I worked in a radiator shop we used to once in a while get gas tanks in from the ferrari dealer down the road. It seems that when you block the gast tank vent in an 80's tesstarossa, the fuel pump is so powerful that the suction it creates actually crushes the tank. Whenever we got in one of these aluminum beautiies we would plug both ends, hook it up to a compressor and slowly pressurize the tank until it popped back into shape. Most of the time the tank was 90% back to its original shape and functional.

I tired this with a cb450 gas tank once and it worked on the shallow concave dents but not on any creases. It also managed to spread the tank apart by several inches. Some careful bending and the tank tunnel shape was back to normal and the tank itself looked pretty good. I suspect the ice trick works the same way by exerting force from the inside out evenly over the surface. I think for it to work the dent has to want to return to its original shape, meaning there needs to be some tension pulling the dent out from the other side. Personally if you own a compressor, the air trick works better (because you then test it for leaks by submerging it in a tank of water like your bathtub). 

The best success I have had was by ratcheting the tank together with tie down straps so it doesn't distort at the mounts, pressurizing the tank so it has some inside surface tension, and then using a paintless dent repair on the dent. Still only pulls out shallow non crease dents but hey it works.

[Raul CB750K1]

When I worked in a radiator shop we used to once in a while get gas tanks in from the ferrari dealer down the road. It seems that when you block the gast tank vent in an 80's tesstarossa, the fuel pump is so powerful that the suction it creates actually crushes the tank. Whenever we got in one of these aluminum beautiies we would plug both ends, hook it up to a compressor and slowly pressurize the tank until it popped back into shape. Most of the time the tank was 90% back to its original shape and functional.
 

That makes sense. If vacuum created the distortion, air pressure can put it back into shape. But when it comes to a dent caused by a fall it's another thing.

You can also try "The ding king". If you want to know what it is just see TV infommercials late at night. You can buy one along with a vegetable chopper, a magic cutter and of course the ab-exerciser!!!!!

Raul

[Raul CB750K1]

Learn from Chrometank, you just need to put a dent on the opposite side to regain symmetry.


By the way, it's been a while since Chrometank doesn't post. Seems things are back to normal in Loveville...

 
Raul