De-seaming Tanks

Has anyone out there ever tried to de-solder Indian tanks for repairs? I have a rather beaten up, but sound RH tank on my 741 that needs some pretty big dents taken out. Is it easy to de-solder the tank, more to the point, how hard are they to get back together again?

Happy Riding,

IR

Indian Runner,
It helps if you have had some experience with solder. Care must be taken during the disassembly process to avoid too much heat (warpage). Cleaning of the mating surfaces is critical. Tin the mating edges. Because of the proximity of the bulkhead between the gas and oil compartments you will need to use 2 or 3 solders with differing melting points. This of course to keeps leaks non existant.
In the end I ended up having it done by a professional !
JKE

If you're going to completely separate the tank (vice spot repairs) I'd suggest that you make a template out of plywood before disassembly to ensure the tank retains its shape during the solder process. This cut-out should fit snugly over the tank edge and will aid in aligning the mounting tabs. Disassembly can be accomplished by carefully using a torch, or better yet a high wattage soldering iron along with a compressed air jet to blow out the solder as it melts. Don’t try to heat all the seams simultaneously: spot melt and blow on alternating sides of the seam until it’s all done. Make sure you have welding gloves and eye protection because the molten lead will splatter.

Re-soldering the tanks takes patience and the right equipment. You'll need a large soldering iron(s)....not a soldering gun or torch! Soldering guns are designed for electrical application and don't put out nearly the heat necessary to do large soldering projects. Torches are designed to put out too much heat....fine for sweat soldering copper pipe or disassembling tanks but impossible to control or limit when re-soldering sheet metal: use a torch and you'll warp the tank and melt all the solder on either side of the flame.

I have several irons: 150, 300 and 500 watts: the two larger ones are practically antiques! I mean who leads tanks and fenders these days?! We tend to just slop on some bondo and go with it. Instead, I lead all dings, dents and welded/braised seams, sand them down, and they work beautifully: no cracking or peeling. The irons have to put out enough heat to get the tank seam and solder hot enough together to fuse or you'll get a cold joint that will leak. The iron’s heat is limited to only the large flat end in contact with the metal and the solder can be floated as you move the iron along the tank surface adjacent to the seam being soldered. .

I'd also suggest that you use lead free solid core solder: 95% Tin and 5% Antimony. It melts a bit higher than lead solder but is much harder and durable than lead. Cleanliness is absolutely important when soldering and any trace of carbon (old gas or oil will leave this behind) or dirt will prevent the solder from sticking. You'll also have to use an acid flux to tin the surface to ensure better adhesion when actually soldering the assembled tank.

To prevent warping, tack solder the tank all along the seam, alternating from one side to the other (kind of like torquing down head bolts) before you attempt to run a bead from one end to the other. You can further limit the heat beyond the seam by using a damp rag just off the seam to cool the rest of the tank. Pressure test it by blowing through petcock, with the non-vented oil cap in place, to pressurize the tank and then close the petcock: don't use a compressor or you'll balloon the tank! Use a detergent solution to check for air bubbles in the seams.

Using hard solder is a great way to do other repairs on tanks and fenders. I've saved tanks that were otherwise throw-aways, especially with corrosion or broken petcock mounts which can be repaired without taking the tanks a part as well as resectioning fenders; filling worn through chain guards; filling fender holes; etc.

Johnmcmd
'39 Chief
'46 Chief

Indian Runner,
I usually pick a reputable radiator shop and have them do mine. Be sure to have them tin the inside. Then they are protected fron rusting through in the future. Of course you can do it your self but since this type of work is 10% knoledge and 90% practice its probably cheaper to have someone who does it all the time do it.
Dusty

Thanks guys,

Yes I think you are right, I will get a rad shop to take a look at it!

IR

Johnmcmd your advice was spot on.
Made a jig out of 3/4 in ply, but found that cutting a snug fit was not a good idea with lots of dents as trying to get the damn thing over the tank was far too hard. (Also as I didnt know exactly how the things were constructed in the first place). I overcame the problem by cutting the plug 1/4 in oversize all around (still gave just enough material to drill fixing holes for the mounting brackets into the ply). I then made around 25 fingers that are either screwed down so as they can be easily removed to allow the tank to be removed or glued in place around the bottom of the tank...has worked a treat so far!
Deseamed my tanks today, took a bit of working out how they were constructed. Thought that the mounting plates were soldered on, and no amount of gental persuation and heat would move them (gas butane torch) so figured that it was either spot welded on or riverted, and didnt bother trying the other two. (and so they are!)
After a couple of hours of blasting away solder with my airgun and some gental levering under heat, the thing started to revel its secrets, and hey presto it was in 3 parts!
Metal condition better than I first thought, with only medium pitting to the petrol tank bottom only, no pin holes.
I am going to get the tank tinned before I reassemble them. I feel completely happy to solder the tanks back together again, its the tinning that will be a bit tricky dicky.
The one problem I do have is getting decent high wattage irons here in Blighty. There is a 300w model you can get, also I found a 500w model, but the tips look pretty small on the darn things!
I managed to find some really good industrial 500w irons with a good old size tip as used by roofers in the (Uwnited) states, but they are expensive with a capitol $$$!!
I am going to try some old solid copper soldering irons as used in the 30's. You know the type, you would heat them to operating temp then use the residual heat of the big lump of copper to solder with. I guess that this is what they may have used in the factory back in the 1920's/30's anyway? They certainly standard equipment duing the war for sheet metal soldering with the Army etc. I will try mine with my butane torch as it gives out around (I think?)1000 deg flame, about right.
Will let you know how the final result pans out, but so far it is very satisfying restoring something that plain looks UGLY!

Happy Riding,

IR

Glad to hear it's working for you! Soldering is one of those lost arts that takes a little time to learn but it's worth it. The old solid copper irons should work just fine: it's probably what they used originally anyway. Back in the day they used a gasoline blow torch (the pump up kind) to heat these irons. They had a "hook" on top and slot on the "barrel" to position the iron over the flame. You can do the same thing on a Coleman gasoline camp stove. They really put out heat and are a lot cheaper than bottled gas. You will need several "irons in the fire" to be able to switch between them as they cool off. The high wattage electric soldering iron tip is supposed to be rather small: about 3/4" to 1" in diameter. It will heat the tank metal sufficiently for you to walk the liquid solder along the seam: solder will follow the heat and you can re-run seams over again to ensure good adhesion.

Johnmcmd

Hi Johnmcmd,

I spotted and ordered a neat little bit of kit today. Its a gas nozzle soldering iron attachement for a gas butane bottle as favoured by the stained glass industry.
It appears to have a decent size copper tip, but what got my attention is that the thing is attached to a flame that is controlled by a lever that regulates the shutting off and on of the gas. So when the tip is up to temp, you simply release the lever and there is just a residual flame to reignite the gas flow when you activate the lever again to bring the tip back up to temp. This way you should be able to keep the tip regulated pretty easily to what temp you require without having to return it to a furnice or flame. Best of all it was very cheap, so if it dont work no big deal.

Happy Soldering!

IR