Newbie saying hello and welding a fuel tank...

[triumph5ta]

Hi, I will soon be the proud owner of a Clarke 130en Mig welder. I do mostly motorcycle restoration so my use of the equipment would be occasional and pretty light. Although I am sure as I get better at it I will use it more, fabricating odds and sods.

Now for the fuel tank bit.
The fuel tank in question is from an old Triumph 750 and has not held fuel for at least 30 years. During that time it has no petrol cap on it and has been flushed out with water many times as part of the process to get loose rust out of it. What im trying to say is there is not a trace of fuel vapour in it.
The problem is that it has a few pin holes in the bottom.
I was thinking of simply building a blob of weld over each pinhole to fill it then grinding it flat... does that sound ok? Its really sound apart from the pinholes.

 

[Coo]

Would you not be better of using a sealant to sosh round the inside...

that way you wont miss any pinholes..

 

[brightspark]

Hi, I will soon be the proud owner of a Clarke 130en Mig welder. I do mostly motorcycle restoration so my use of the equipment would be occasional and pretty light. Although I am sure as I get better at it I will use it more, fabricating odds and sods.

Now for the fuel tank bit.
The fuel tank in question is from an old Triumph 750 and has not held fuel for at least 30 years. During that time it has no petrol cap on it and has been flushed out with water many times as part of the process to get loose rust out of it. What im trying to say is there is not a trace of fuel vapour in it.
The problem is that it has a few pin holes in the bottom.
I was thinking of simply building a blob of weld over each pinhole to fill it then grinding it flat... does that sound ok? Its really sound apart from the pinholes.

u could clean it up well and silver solder it or braze them .a few options

 

[triumph5ta]

Would you not be better of using a sealant to sosh round the inside...

that way you wont miss any pinholes..

Yeah, I will probably do that too, more to stop it from rusting again, I just want to make a more permanent repair if you know what I mean.

 

[pedrobedro]

Stick it on the car exhaust pipe and start the car then weld it. We welded a nut to a DT125 tank to pull a dent out the other day and it was o.k.

 

[BillJ]

You'll almost certainly find that the metal is extremely thin around those pin-holes if they are due to rust. The pin-holes are just where the thickness is reduced to nothing. If you try to weld them you will find your blob burns through. It would be much better to cut the metal out around the pinholes so you are left with thicker metal to weld to, then make a patch and weld it in. Butt-welding is a bit harder than just lap-welding a patch on top but if you're worried about how it looks a butt-welded patch will be flush and can therefore be made invisible from the outside.

If appearance is not so important, you could simply weld patches over the top of the holes.

Once you have been welding for a while and folks get to know about it, expect to be offered jobs to "just quickly weld..." ratty old exhausts by people who don't understand that if there's a tiny hole, there's a large amount of rust around it that can't be welded to

 

[triumph5ta]

You'll almost certainly find that the metal is extremely thin around those pin-holes if they are due to rust. The pin-holes are just where the thickness is reduced to nothing. If you try to weld them you will find your blob burns through. It would be much better to cut the metal out around the pinholes so you are left with thicker metal to weld to, then make a patch and weld it in. Butt-welding is a bit harder than just lap-welding a patch on top but if you're worried about how it looks a butt-welded patch will be flush and can therefore be made invisible from the outside.

If appearance is not so important, you could simply weld patches over the top of the holes.

Once you have been welding for a while and folks get to know about it, expect to be offered jobs to "just quickly weld..." ratty old exhausts by people who don't understand that if there's a tiny hole, there's a large amount of rust around it that can't be welded to

Thanks, all good sound advice.

 

[wavestarved]

Once you're done sorting the holes out use some "Petseal" to seal the inside of the tank and stabilise any last bits of rust. I used some on a GPZ900 tank that was knacked; worked a treat.
Post some pics of the Triumph too please, very interested.