So, given: a heavily dented tank, dents with a tricky profile in tricky places. Task: to align it to “as it was”, but not to overtighten the thin metal. Method: soldering the probe and pulling with a reverse hammer.
Below the cut I post a description of the method with a photo report of the work done. The author is not me, but I just combed the report and posted it (he doesn’t mind). You can send him an invite to BP :)
Go…
We drain the gasoline, unscrew the gas valve, the cap and blow the tank with air.
We clean the dent and a little around it with a circular metal brush (the kind you use on a drill).
This can also be done with abrasive (sandpaper), the result in any case will be something like this:
... and tin the soldering points of the nut on the tank with soldering acid. You can also tin the entire area of the dent if it is small, as in this case.
Due to the lack of special tools and devices for tin work, I made a homemade reverse hammer (made in 10 minutes from an M6 bolt, an electrode with a diameter of 4 mm and a weight mounted on it, weighing about 200-300 grams).
The trick is making the right choice soldering places. I started pulling out dents from the edges.
Naturally, having tinned the surface of the nut to be soldered, we solder it in the right place. I did not use a simple nut, but one with an increased area that will be soldered (essentially a piece of a 12 hexagon with an M6 thread).
To prevent the nut from moving from the selected location when soldering, I used an M6 pin approximately 120 mm long.
Solder it. We wait until the solder hardens. By the way, I used solder of an unknown brand, but it is refractory. It won't melt with a regular soldering iron. Actually, we screw the reverse hammer to the soldered nut and begin, holding the weight, to tap out the dent. The number and force of impacts depends on the depth of the dent. When the metal returns to its original shape, the nut simply comes off with the blow of a reverse hammer. That is, unlike welding, it is impossible to tighten the metal.
The elongated surface can be straightened with an ordinary hammer, preferably through a wooden block. It turned out very well. The solder is simply removed from the metal using the same brush attachment on the drill. A thin layer of putty will smooth out the micro-dimples left on the metal. I think for larger dents you will need to use a larger diameter nut.
In the end it turned out like this:
Does your motorcycle tank have a dent? It’s okay, it happens, because only those who don’t drive don’t fall. But now the gas tank needs repairs, and the service center will charge a lot of rustling pieces of paper for straightening and painting... But you can do everything yourself if your hands grow from the right place, and at the same time they are no more crooked than the face of the alcoholic Petrovich from next door entrance on Monday morning. You can fix a dent on the tank yourself! First you need to determine the extent of the damage. If the dent on the gas tank is small, and the tank itself is painted without any tricks like stickers under the varnish or airbrushing, then you can get by with local editing and painting. If the damage is serious, you will have to paint the entire tank. In the second case, everything is clear, but what to do in the first?
First, you need to estimate the surface area that will be subject to deformation during the process of straightening the dent, and carefully clean it from paint coating. There’s probably no need to explain to anyone how to remove paint from a gas tank. Having finished this, you need to straighten the dent. A reverse hammer is ideal for these purposes - a special device for straightening such dents. It is unlikely that it was lying around in your garage purely by chance, but you can buy it or borrow it from friends. But we are not looking for easy ways! Or, suppose we don’t have a reverse hammer, there’s no one to borrow it from, and the lack of extra finances doesn’t allow us to buy it. Then there is another way, but we will need a soldering iron, soldering acid, solder and braided steel cable. Intriguing start, huh? So, you need to strip about five centimeters on one side of the cable, unravel it and tin it. The dent on the tank must also be tinning. Having finished with this, take the cable and firmly solder its unbraided elements to the place on the motorcycle tank that needs to be straightened. Then we begin to use moderately brute force - we pull the cable, if necessary we jerk it, but only carefully, then the cable will not come off from the solder point. This way you will gradually draw out the dent in the gas tank enough so that it can be hidden during the painting process. Only if you still use a reverse hammer, and not this whole Kama Sutra with a cable and a soldering iron, do not overdo it.
Having finished editing, remove the remaining solder from the gas tank (if you used a cable circuit), clean the surface, level, prime and prepare for painting. That's it, you can paint, after, of course, carefully covering with masking tape all those parts of the motorcycle that should not be accidentally painted.
There are a great many ways to remove dents on a tank. Someone advises burying the tank in the sand, pouring a little gasoline into it and bringing a fire to the filler neck: the gasoline will explode and straighten out the dent. Someone pours peas into a tank, fills it with water and leaves it until the peas swell and press out a dent. Someone fits a ball camera under the dent and pumps it until it pushes out the dent. More advanced repairmen correct dents with a reverse hammer.
Today we will take the easier route and try to remove a dent using a compressor: this method is accessible to almost anyone, fast and quite effective.
As a visual aid, we will present a tank from a regular Alpha. For some reason, almost all Alfas have a tank that crumples on top for some reason.
There are also a series of dents on the sides
We seal the filler neck as much as possible. The fastest option is to put a piece of rubber on the neck, put a board on top and crush it with a clamp.
When we pump pressure into the tank, it will begin to deform and to prevent the halves of the tank from moving apart, we tie the halves of the tank together with a rope
Insert a blow gun into the hole in the fuel valve and pump air into the tank
