The BSA A7-A10 Forum
Technical (Descriptive Topic Titles - Stay on Topic) => Frame => Topic started by: Stephen Foster on 03.10. 2022 15:31
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Hello , Im in the process of restoring the fuel tank (Balloon type) on My 1939 BSA WM20 ..the bottom edge all round is rottedaway so Im forming a new bottom and intend removing around 2-3" all around the rotten edge,butt welding new metal but am concerned about heat distortion around the top edge ? would Anyone have any suggestions for this please ? I am an experienced welder & have MIG , TIG or Oxy Acetylene but am undecided which to use ? Thank You in advance , Steve .
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I’m an inexperienced welder but TIG is usually best for thin sheet.
I’ve seen an experienced panel beater/tank guy remove a tank bottom using a coarse sanding disk on the (little) weld at the bottom of the sides, do the necessary repairs eg dent removal, then TIG the bottom back in. He rarely gets a leak, and has to go over the TIG weld again.
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Thank You,
Ive done that ..removed and made a new bottom .
The bottom seam will be fine its the seam 2" higher up the tank wall Im concerned about .
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its the seam 2" higher up the tank wall Im concerned about .
So would I be - can't see how that could be done without distortion. I believe the trick is short bursts of MIG, though whether that ends up leak-proof is anyone's guess.....
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I'm no welding expert, but is it worth considering Brazing? obviously much lower temperatures are involved, -I've done plenty of repairs brazing, though obviously it's different to a complete reconstruction. Didn't they used to solder tanks back in the day?
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Hello , Im in the process of restoring the fuel tank (Balloon type) on My 1939 BSA WM20 ..the bottom edge all round is rottedaway so Im forming a new bottom and intend removing around 2-3" all around the rotten edge,butt welding new metal but am concerned about heat distortion around the top edge ? would Anyone have any suggestions for this please ? I am an experienced welder & have MIG , TIG or Oxy Acetylene but am undecided which to use ? Thank You in advance , Steve .
think I would put the cap on the tank fill the tank with ice cubes through the bottom then tig your patch in ....should keep the heat local ....when I weld thin body panels I tack weld opposite ends and eventually join the tack welds
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I'm no welding expert, but is it worth considering Brazing? obviously much lower temperatures are involved, -I've done plenty of repairs brazing, though obviously it's different to a complete reconstruction. Didn't they used to solder tanks back in the day?
BSA stopped soldering tanks when they went from flat tanks to saddle tanks around 1920.
Most soldered tanks had a bottom that was like a cup that the top of the tank sat in then the solder was run around the edges
The thick pin liniing hides the joint between the top & bottom,
Notrun used to scollop the upturned sides to get more surface area for the solder
Both joint faces were tinned then they were pressed together & oven baked to get the solder to join
If you look closely at the bottom os an unmolested BSA tank you will see the bottom is rolled over like a tin can lid
If they were tern plate then again oven baking will make a seal
Latter tanks with exposed ends were a rolling resistance weld
These tanks are the ones that rust out along the welds
I am fairly sire that M20 tanks were braized edge on
This would have been a war time idea to save on steel
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Taken quite a few bases off over the years for various reasons by grinding bottom weld, and then gas welded them back. But tank sides is a different kettle of fish.
Here's what I'd do (as I have done when repairing car doors / wings).
Form an overlap on existing edge (the tool required is called a joggler - bit like the tool used to set handsaw teeth). That stiffens and greatly reduces warping. The new metal then overlaps the old by around 1/2", with the overlap unseen inside. Spot weld the join and finish off with lead or filler. Lead would be best here from a leakage point of view. Personally, I've always found spot-welding (with a proper spot-welder) unreliable when joining old & new metal. It either doesn't bond or burns a hole, so here's my remedy: drill 1/4" holes in one side (in this case the new metal) at 1" intervals and use these to braze the join together (it's what they used to do to strengthen rally car bodyshells). Perhaps a little panel-beating then finish off with lead.
Good luck.
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This is off to a slight tangent, hope nobody minds...
I've been fabricating a small brass part (steam cylinder) for an O gauge clockwork Robilt model loco. It's all pretty thin wall brass, and while it's pretty good, it's not perfect.
In the old days we used to use solder 'Tinman's solder' I think we called it, to flow and work like a filler. But what flux did we use?
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Taken quite a few bases off over the years for various reasons by grinding bottom weld, and then gas welded them back. But tank sides is a different kettle of fish.
Here's what I'd do (as I have done when repairing car doors / wings).
Form an overlap on existing edge (the tool required is called a joggler - bit like the tool used to set handsaw teeth). That stiffens and greatly reduces warping. The new metal then overlaps the old by around 1/2", with the overlap unseen inside. Spot weld the join and finish off with lead or filler. Lead would be best here from a leakage point of view. Personally, I've always found spot-welding (with a proper spot-welder) unreliable when joining old & new metal. It either doesn't bond or burns a hole, so here's my remedy: drill 1/4" holes in one side (in this case the new metal) at 1" intervals and use these to braze the join together (it's what they used to do to strengthen rally car bodyshells). Perhaps a little panel-beating then finish off with lead.
Good luck.
I had been considering using a joggler along the tank edge ..it would add stiffness I am sure .
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In reply to joolstacho, we use spirits of salts also called hydrochloric acid or muratic acid which is highly corrosive and needing thorough cleaning after soldering. Or, you could use a non corrosive resin flux if the item is easily tin able.
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I had been considering using a joggler along the tank edge ..it would add stiffness I am sure .
And a good joggler will have a reversible head and can be used to punch the 6mm holes too.
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Ta Reg. And I wouldn't mind seeing some pics of this tank repair job.
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But what flux did we use?
I seem to remember Baker's Fluid.
Seems it's still available!
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Been using Bakers for years - for soft soldering - wiring etc, but it doesn't seem to help for 'flowing' over a flat surface.
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borax works well for soldering as well
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In reply to joolstacho, we use spirits of salts also called hydrochloric acid or muratic acid which is highly corrosive and needing thorough cleaning after soldering. Or, you could use a non corrosive resin flux if the item is easily tin able.
Spirits of salt is Zinc Chloride not hydrochloric acid
Dad used to make his own by dropping old galvanised clouts that had been pulled out of timber into hydrochloric acid till it no longer bubbled
BAck then we knew how to be frugal
Bakers is basically ZnCl
To solder onto steel you need to use a nitrate flux
Usually a stuff called "Tinning Butter" "Panel Paste " or "Panel Butter "
This is because neither tin nor lead will take to raw steel
Then you need to use tinmans solder which is 40:60 or plumber solder which is 50:50.
Good tinmans solder will have around 0,5% Cu & 0.1% Fe
Soldering things like petrol tanks needs a slow solidifing solder which is very similar to lead wiping
Totally different to electrical soldering where you want the stuff to solidify the instant you take the iron off it
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The more I see of mig weld body repairs on old metal on TV, the more anguish I feel for the folks that buy the restored vehicle for several thousand ££££'s. In my experience MIG will only work well on new clean metal. Plug welding a new panel onto a joggled edge still carries the risk of distortion on unsupported original panels....a rear wheel arch for instance. Try and run even a short bead and the buckles still appear. So all these restorers use a join the dots method, hardly a recipe for a good strong cohesive fusion joint.
Brazing is better for a tank repair. Like soldering, the parent metal is not melted, but the filler material added at a lower temperature so less chance of distortion. A brazed joint is much stronger and durable than a soldered one, but as always distortion is your enemy, and success depends to a degree on the rigidity of the metal surrounding the repair. Soldering or brazing needs the parent metal to be clean, Bakers Fluid was the acid dip in a can, back in the day. You bought a can, did the job, and of course the next time it was needed the contents had turned brown or the stuff had eaten thro' the can. Nice to see it's still available, now packed in a modern single use plastic bottle.......Progress indeed.
Swarfy
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BSA54A10, of course you're right, I forgot the zinc part. We used to call it "killed spirits".
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The more I see of mig weld body repairs on old metal on TV, the more anguish I feel for the folks that buy the restored vehicle for several thousand ££££. In my experience MIG will only work well on new clean metal. Plug welding a new panel onto a joggled edge still carries the risk of distortion on unsupported original panels....a rear wheel arch for instance. Try and run even a short bead and the buckles still appear. So all these restorers use a join the dots method, hardly a recipe for a good strong cohesive joint.
As usual from Yourself..excellent points ..
I am experiences in using MIG , TIG , Oxy acetylene & MMA having worked in the Nuclear industry ..its the distortion aspect Im concerned about .
Im inclined to butt weld the sides with TIG ,stitching in small runs whilst gently dollying the distortion as I work My way along the seam ..Ive even considered temporarily tacking a strong back to the existing tank sides whilst I complete the weld bead..removing this upon completion ..although Im worried this may introduce additional stresses into the tank material ?
Will prepare test plates later to set parameters ,technique , etc .
Thank You "Swarfcut" and all contributors for your collective insights .
Brazing is better for a tank repair. Like soldering, the parent metal is not melted, but the filler material added at a lower temperature. and so less chance of distortion. A brazed joint is much stronger and durable than a soldered one, but as always, distortion is your enemy, and success depends to a degree on the rigidity of the metal surrounding the repair. Soldering or brazing needs the parent metal to be clean, Bakers Fluid was the acid dip in a can, back in the day. You bought a can, did the job, and of course the next time it was needed the contents had turned brown or the stuff had eaten thro' the can. Nice to see it's still available, now packed in a modern single use plastic bottle.......Progress indeed.
Swarfy
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The more I see of mig weld body repairs on old metal on TV, the more anguish I feel for the folks that buy the restored vehicle for several thousand ££££'s. In my experience MIG will only work well on new clean metal. Plug welding a new panel onto a joggled edge still carries the risk of distortion on unsupported original panels....a rear wheel arch for instance. Try and run even a short bead and the buckles still appear. So all these restorers use a join the dots method, hardly a recipe for a good strong cohesive fusion joint.
Brazing is better for a tank repair. Like soldering, the parent metal is not melted, but the filler material added at a lower temperature so less chance of distortion. A brazed joint is much stronger and durable than a soldered one, but as always distortion is your enemy, and success depends to a degree on the rigidity of the metal surrounding the repair. Soldering or brazing needs the parent metal to be clean, Bakers Fluid was the acid dip in a can, back in the day. You bought a can, did the job, and of course the next time it was needed the contents had turned brown or the stuff had eaten thro' the can. Nice to see it's still available, now packed in a modern single use plastic bottle.......Progress indeed.
Brazing is better for a tank repair. Like soldering, the parent metal is not melted, but the filler material added at a lower temperature so less chance of distortion. A brazed joint is much stronger and durable than a soldered one, but as always distortion is your enemy, and success depends to a degree on the rigidity of the metal surrounding the repair. Soldering or brazing needs the parent metal to be clean, Bakers Fluid was the acid dip in a can, back in the day. You bought a can, did the job, and of course the next time it was needed the contents had turned brown or the stuff had eaten thro' the can. Nice to see it's still available, now packed in a modern single use plastic bottle.......Progress indeed.
Braizing ( as in with brass or bronze filler rods ) is not good for fuel tanks as it has a very low fatigue linlit so is not suitable for for joints subjected to flexing.
Silver soldering ( using a nickle silver rod ) is substantially better for tanks.
This is why vintage & veteran bikes had braised frames with tubes held rigidly by the forged / cast lugs & soldered the tanks
Lead is very flexiable which is why quality cars were lead wiped rather than filled with epoxy to cover seams & joints .
It is also why plumbers used it on hot water tanks and external water tanks subject to expansion & contraction and guttering plus down here for joining bull node sheets of corri iron together ,
Do not mix this up with modern no lead silver solder which is a Sn-Ag alloy and not particularly good for anything other than circits
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Good information from Trevor. I always braze such joints but did ponder the alternative silver solder. Requires slightly lower temperature too, which is helpful. Also has a greater capillary action (in my experience).
Having thought about the job a little more, I'm convinced joining with a rebate (joggler created) and brazing / silver soldering through the drilled (or punched) holes is the way to go. There should be minimal distortion - if any.
Remember, braze / SS ONLY the holes - not the whole join. And do not go 'down the line' - do one hole then leave out several to do the next one (you don't want to build up heat in one location). To keep the join tight, use self-tapping screws through some of the holes into the metal behind. When all the other holes are done, remove screws and braze / SS those holes. Finally, seal join with solder to ensure join is leakproof.
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I have in my possession a bar of genuine ex telephone jointers soft solder. If it's realistic to send it we can talk about it.