Without a doubt one of the biggest challenges of the project has been the fuel tank. From deciding the material to the fuel pump, fuel level sensor, how to make it so it’s strong, there were many a bottle of beer consumed whilst pondering the best route forwards.
On thing that was apparent was that the fuel tank was not going to be very big. In order to maximise fuel volume, I wanted to make the fuel tank fit as closely to the inside of the bodywork as possible. To do this, I employed the bodywork mould which I lined with roughly 8mm of clay to create an offset surface that would represent the fuel tank’s outer surface. With 2 other bulkheads installed into the mould to represent the front and underside of the tank, I calculated roughly the volume, mixed up the appropriate amount of 2-part PU expanding foam and poured it into a hole I drilled in the mould.
With the back part of the mould removed, the starting point for my fuel tank is revealed.
Having achieved a rough foam volume, this then had to be refined to fit inside the seat frame. I had originally wanted to make the fuel tank double up as the seat frame, to both reduce weight and maximise fuel volume, but after deciding to make the fuel tank in a suitable epoxy resin which is fuel and ethanol proof, a separate steel frame was required. The final arrangement is seen below. The purple cylinder is the bracket holding the external fuel pump, which just fits in the available space. Almost as if it was planned in advance…
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The fuel filler goes through the airbox and out the back of it, before joining to the tank.
So having taken a mould off my dummy foam tank, the two halves were laid up using the special fuel proof epoxy resin. This being my first attempt at vacuum bagging, I had several issues, including resin not permeating the glass matt fully – I used a technique where the glass matt was spray glued into place dry, and then the resin pushed in through the fibres afterwards. The high viscosity of the resin didn’t help, and I ended up with several dry spots that had to be wet out after demoulding… but hey, it’s a learning process!
Fuel filler neck with a brilliant closing flap robbed from a discarded ford fuel tank
Foam inserted to stop fuel sloshing about.
This is not the end of the fuel tank story… unfortunately to get the bike TUEV approved for use on the road, the tank would have to undergo an exhaustive testing. So ultimately the tank would be replicated in aluminium. More on that later.
Oh, and the fuel volume you ask? A massive 5 litres! Hmm…
