Making a stainless steel or aluminium fuel tank

[Nick Jackson]

My Triumph 2.5PI saloon could benefit from a new fuel tank. I was wondering about making one in either stainless steel or aluminium for either weight-saving and/or rust prevention reasons.

Can I MIG weld aluminium or stainless steel? I have a Portamig 185.

Thanks
Nick

 

[aametalmaster]

You sure can. It might be tough getting a gas tight seal but i don't know how good you weld and fit...Bob

 

[hotrodder]

Stainless is more expensive but a lot tougher than ally which needs a bit more thought* to how it's mounted etc from a fatigue POV. If you go to http://www.mig-welding.co.uk/mig.htm ally and stainless are covered, the later under 'welding different steels'. As said getting air tight welds is probably the toughest bit if using MIG on typical material thicknesses (1 - 1.5mm steel/stainless and 2mm ally) used for fuel tanks

Material specific issues... stainless is far more prone to distortion than mild steel and it's corrosion resistance can be messed up somewhat with the wrong gases/techniques (both touched on in the above link). Ally really should have some shape put in it IMO... strength/stiffness through geometry and all that as a flat sided box doesn't have much structure to it- flanged joints are much better than outside corners, bead rolling flat panels to stiffen 'em up etc


* Mounting tabs/brackets are a common one... even with a baffled tank the weight of fuel sloshing about can result in mounts cracking. Make the brackets thicker and they can end up tearing out of the tank instead. Adding doublers (locally increasing thickness) spreads the loads, using thicker material is another way but materials bill obviously goes up and it's tricker to fold etc. Using straps can be a more elegant way but obviously all depends where the tank is sited, it's shape etc

 

[TechnicAl]

Like Hotrodder is (almost) saying.............forget Aluminium

 

[piman]

Hello Nich,

there's a lot more to a petrol tank than just the tank, there are internal baffles to think about and the internal swirl pot on the P.I.'s tank?

I'd hunt around for a second hand tank if I were you? Do be aware the P.I. tank is different to the carburettor car's tank.

Alec

 

[Nick Jackson]

Mmm, obviously not as straightforward as I thought then. Aluminium doesn't sound feasible and stainless steel doesn't really offer much gain over a properly treated/painted mild steel tank.

piman - with your knowledge of swirl pots I assume you're not unrelated to the piman on the Club Triumph forum? I knew of the swirl pots but not having seen one I wasn't sure how difficult it would be to re-create one.


Thanks all

 

[langy]

If you have access to a good tig welder you can easily make a tank in Ally or stainless, swirl pot not to hard to make either. It all depends on your abilities

 

[hotrodder]

As Langy said swirl pots are pretty simple things... in tank types are just a baffled fuel pick up that traps fuel by the pick up i.e. fuel can get into it easily but can't escape, necessary with FI as there's no float bowls. Googling 'in tank swirl pot' will show the various ways it's done. The 'Pro Alloy' website shows another way that works with one way valves... a bit overkill IMO for a baffled tank but makes more sense if foam filling instead

As Piman said there's a bit more to a fuel tank than just a box that won't leak for example...



Swirl pot is already hidden by baffles, the two open pipes are the pick up and return (both feed into the pot)

 

[Nick Jackson]

Thanks for that. It's a bit complicated for me as I'm still at the novice stage at the moment.