Alloy fuel tank

[jimson]

G'day viewers I'm thinking of making a fuel tank out of alloy.
 First question how thick should the alloy sheet be 
Second question how do I work out the fuel cap 
Thanks jimson.

[Lozza]

Your making it out of aluminium not forking alloy
Better question is exactly how will you make it? Start with a flat sheet and start slapping away?
Cap is simple machine one and a female spigot and weld it in.

[LWC82PE]

Heres an alloy tank fitting you could weld in. Just machine off the flange with holes.

http://www.acerbistore.it/product.aspx?ID=70&C=112&L=2

[vandy010]

G'day viewers I'm thinking of making a fuel tank out of alloy.

Tom finally sucumb to the pressure did he?
put him to work

[Ji Gantor]

Hi Jimson,
Lozza is right and I am probably the worst for writing it.
Aluminium or Ali is what I should write.
Anyway I have just measured my Maico 77 tank and it appears to be 3mm thick. I would say it is that thick because it has to be welded and the rough treatment tanks get.
Fatigue cracks on all fittings would also be reduced by increasing the thickness.

I hope this helps

Tight nuts

Ji

[GMC]

Your making it out of aluminium not forking [/i] alloy[/i]

I imagine he will be using Aluminium Alloy as pure Aluminium has poor qualities

2mm would be the way to go.
1.5mm will bend easily but will be hard to weld and polish.

I built a tank many years ago by buying an alloy () tank from the wreckers and cutting the filler neck out of it to weld into the tank I was building. As fate would have it few years later the tank I chopped up became desirable (YZ 125C)
Problem is most old tanks are now desirable so cheap damaged tanks are hard to come by.


They say that teenagers are often a bad investment so it's good if you can get a return for the money spent;D

[Slakewell]

I have before purchased a filler cap any model etc as long as you like it, Then with a thread gauge you work out the threads per inch and then machine that on the lathe, You can buy 2 inch BSP alum ends from blackwoods I have used these in oil tanks. Depending unpond your skills with the wooden malet I would use 2.5mm or 2mm sheet. 2.5 will let you sand off more mistakes. 3mm is harder to bend. a heat gun and just too hot to touch is reconmended before forming.

[Ji Gantor]

The Maico tank is a coffin shape which is more folded than curve formed.
I guess that is why they selected 3mm, ease of welding.
As Lozza said somewhere, see if you can purchase a sheet of aluminium alloy that is soft and designed for forming but make sure it can be welded as well.

Tight nuts

Ji

[Slakewell]

Silicon % makes it softer and are there 7 grades
Normal everyday alum sheet is 3000 series and 5% silicon
If you buy 30% silicon sheet it will form easier but it is harder to weld.

[Ji Gantor]

1200 series is pure aluminium for cooking utensils, has an A rating for forming and welding,
2011 series is for machining or turning on a lathe, has a C rating for forming and a D for welding,
5005series is for general purpose sheet metal work, has a A rating for forming and welding,
5052 series is for medium strength alloy with good ductility. Suitable for welding with high corrosion resistance particular for marine applications, has an A rating for forming and welding.

Most sheet aluminium alloy is 5005 series with a H34 temper,
Tread plate is a 5052 series with no temper.

Attached is an image of a tread plate bin I folded and welded for my workshop.
Prop plate is a 3003 series with a H22 temper and an A rating for forming and welding.
Most ute tool boxes are made from Prop or tread plate alloys.

Tight nuts

Ji

[firko]

I suppose it depends on what sort of tank you're making and what bike it's going on but another cap option is to use a 2'' Monza style flipper cap. You can get the real deal British or Italian versions for around $100 but I've also seen Chinese copies for around $30 or even less.
                                      
http://www.britcycle.com/products/622/62209001.htm
ttp://cgi.ebay.com/ebaymotors/Authentic-Monza-Gas-Flip-Petrol-Cap-2-Made-UK-/200478111258?cmd=ViewItem&pt=Motorcycles_

I made a Maico coffin tank out of 2mm softish Aluminium (not sure of the alloy content as it was a foreign order at work and I was restricted to whatever was on the sheet rack). Because the Maico tank is basically a slab sided box, the construction was pretty straightforward. I measure a stock tank and transferred the dimensions to a sheet of template paper (cardboard) and cut the whole upper section in one piece and then folded it to the same bends as the sample tank using a brake press. I then made the bottom section by hand rolling the section over a 2" piece of pipe. From here on it's hard to explain without photos but the use of small sheeties hammers and dollies and tacking it as you go using the TIG
pretty much makes it a job for the patient and skilled otherwise you'll end up with a horrible looking letter box candidate.
Below are a couple of random shots I took of Frank Stanboroughs Greeves/NSU tank while it was under construction. Franks done everything bby hand using pure Aluminium and oxy welding. He's an old school kind of bloke, our Frank! Note inbuilt baffles, something not really needed on an MXer but not a bad thing just the same. The third shot (below) is of the hand formed Tank he made for his NSU Sportmax road racer, once again all oxy welded.

[Lozza]

The easy way to do it is find some aluminium in annealed O condition, make a female MDF/plywood buck* then  fold/bend/lay cardboard over it to get an idea on what shapes the flat sheet will be cut into. Then you can beat or slap into the shapes and use clamps etc to hold it on. I have seen a repetition buck where copper,brass or steel or such bungs were inserted into the buck to make tack welding easier.
As firko said would be a job for the very patient, I would imagine 'coffin' style tanks to be far easier and the more compound curves the difficulty would rise exponentialy.  I would imagine first attempts would be pretty rough, I would be tempted to perfect the techniques with thin steel/aluminium 

* a buck is like a female 'skeleton' of the finished item, they look like airplane fuselage's before they are sheeted.

[jimson]

Thanks for the input so far. I was going to make a dummy tank out of wood that way I can shape the ALUMINIUM over it. Tom will do the welding. It will be up to me to get the shape right    jimson

[Lozza]

 
That would be ideal

[evo550]

Jimson,
You can get pre made filler throat and cap from boating supplies store.
They are a short peice of Al pipe with a thread turned down with a cast Al cap (Very similar to elsinore cap) even have breather hole.