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 .
The fuel tank itself was originally made with fuel pickup fuel filler neck and breather and foam filled, no facility had been required for a sender unit.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.
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.
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.
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.
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 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.
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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