Formula Ford Fuel Tank Modification

I made this fuel tank in aluminium for the local Further Education College when they started a Motorsports course. One of the first cars they purchased for race and testing was a formula ford with 1600cc engine.

The race car itself had been stripped down and various improvements made to it to improve all aspects of the car by students and lecturers .

Original tank with new sender flange hole cut in

The fuel tank itself was originally made with fuel pickup  fuel filler neck and breather and foam filled, no facility had been required for a sender unit. Upon strip and rebuild it was decided this year that they wanted to upgrade the tank to include a fuel level sender.

Sender unit & machined flange

A new sender unit was sourced and a new alloy flange to mount the sender was machined and collected with the tank for mods and fitting.

Now with a tank that has been foam filled to prevent fuel slosh is not as easy to modify as a tank with baffles. Typically you can never get all of the foam out of the tank. As this foam has been soaked in fuel it is very difficult to prevent ignition of the fuel vapours when electric arc welding.

CAUTION !!  – DO NOT TRY THIS AT HOME

So to modify this tank I needed to mark and hole saw the new aperture for the new fuel sender mounting flange, upside down to any swarf falls out and not into the tank. I cannot just start welding – I had to fill the tank with an inert gas (argon) to remove all the oxygen in the tank.

Filling with argon gas

Argon – an “inert” gas

Argon gas is an inert gas (non-reactive) and is also heavier than air. I f we completely fill the tank with argon gas – even if there is still tank foam and fuel vapours in it the fuel vapours will not explode. I would not recommend anyone try this at home as it can be dangerous and I have seen a tank “blow” and send the welder across the workshop (he was lucky not to be hurt) and the tank ended up ripped apart due to the explosion when the fuel vapours ignited.

Fuel tank foam clearly visible through new hole

 I could not remove all of the foam and hence filling the tank with argon. I prefer to completely empty the tank, wask it out / steam clean it inside and then fill with argon before welding new fittings to a used tank.

Having had experience of welding aluminium tanks that have been used I know that I can get away with filling foam filled ones with argon before attempting welding of new fittings etc.

tacked up sender flange

See above the sender flange in position tacked up and level in the tank, note also the argon gas is still being fed into the tank by the black hose. Please also note that the bottom hose stub (fuel take off stub) has been taped up to prevent heavier argon gas escaping from the bottom of the tank.

New Flange welded in position

New flange welded into position, once this has cooled down its ready for blanking off and pressure testing again just to make sure that there are no pinholes in the weld and potential leaks.

If it is leak free then we need to fit the sender and squash the foam blocks and push back into the tank through the filler neck.

Fit the sender 1st and then push foam back in thro filler neck

AGAIN I NEED TO REITERATE – PLEASE DO NOT ATTEMPT THIS AT HOME !!

Hopefully the college will be happy – and now they can see how much fuel is in the car without using a stick.

Hope the students take care of it and plumb back in neatly 🙂

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BMW MINI Alloy Race Tank Fabrication

I was asked to manufacture a 5 gallon tank for a customer building a BMW Mini race car, after discussions about size fittings baffling etc a fag packet sketch was produced in order to make the job.

I started with 1.5mm thick NS4 Aluminium sheet, plastic coated 1 side. Once dimensions were worked out I decided to complete as 2 pressed panels. Panels were marked out using tape measure, engineers square and fine tipped marker pen.

Once marked out the sheet was cut using a hydraulic guillotine for speed and accuracy, de-burring panels before proceeding reduces chance of cutting yourself whilst working with the sheet. Fold lines were marked on the panels but, before folding the strengthening swage lines needed to be put in – this I completed using a standard manual swaging machine, after which folding the 2 panels on a Box Pan Folder was completed. Results as shown –

 

Main body complete and ready for assembly, however I need to add filler hole, fuel pick up, return and breather hole, this will be completed in due course with a drill, hole saw and drill bits before tacking up.

Splash pan was manufactured again using 1.5mm NS4 aluminium and again marked out from sheet cut out using a guillotine and bench knife before pressing on the trusty box pan folder to the correct degree for the corners to meet up.

Once formed up to a square splash pan with a flat base I used a hole saw of 41mm diameter to cut a hole in the centre of the base for the filler neck to welds into. The filler neck was tig welded from the back of the into the base of the splash pan during welding the pan corners up, After welding the main body a drain stub was welded to the splash pan to drain away any spillage during topping the tank up.

Before assembling the tank, I used an electric hand drill to cut all holes in the tank body as required, this then means we can ensure a totally clean tank inside as we do not want swarf or aluminium dust inside the tank once complete for obvious reasons.

 

Tank foam was added to fill the tank to reduce fuel slosh before the 2 halves of the tank were assembled. Some adjustment was needed using clamps and small wedges to ensure that a neat outside corner joint was tacked up all round the edges to be joined by welding. If the set up is accurate a neater stronger weld can be produced and even penetration can be achieved, thus reducing chance of leaks or fractures. A good joint set up is also critical for speed of welding and aesthetics – e.g. weld will be a more even corner fillet if joint is tacked up correctly. So its worth spending a little for time and effort to get this part of the job right.

You will notice that I have already added fittings before set up of main tank body again to reduce chance of tank contamination.  

Using a coin tor score plastic coating reduces chance of scratching panel when removing plastic around areas that have to be welded. Aim is to leave as much plastic coating on the tank during manufacture to reduce scratch marks. Once complete it can all be removed.

 

Safety is a must when welding, you may have noticed in some images I have a fire extinguisher to hand should anything untoward happen, I wear TIG gloves and work overalls (fire retardant are best) and a quality air fed (& filtered welding helmet).

TIG welding produces a quality weld (dependant on welder skill, set up, gas flow, torch angle, torch aim etc), I aim for a nice even regular ripple effect and whilst welding tanks with outside corners a nice small “teardrop” effect in the bottom of the root, which tells me I am achieving a nice even bead of penetration – essential to ensure you get a strong, leak free joint.

Picture of completed tank, ready for pressure testing, which I do using a battery powered pneumatic pump, connected to one of the pipe stubs whilst blanking off the rest. Once under pressure ( a couple of bar is sufficient) the welded seams are brushed with soapy water whilst I look for a steady stream of small bubbles indicating a pin prick of a hole in the weld. As with all tank caps, aluminium or stainless steel it is a good idea to put a small amount of copper grease on the threads which helps prevent thread “pick up”.

Hope that this post may of been some help to you or at least an insight into building a race tank in aluminium.

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