The final step in this merry dance was to attach the filler neck and tank supports in exactly the right places to fit the original mountings and have the filler neck pass precisely through the chassis outrigger I made in an earlier post. There is a fair bit of free space around the tank but it’s surprising how quickly a few millimetres here and there add up to components rubbing on things they shouldn’t touch.
The easiest way to replicate the layout of the original tank is to use it as a template, so I raided the scrap bin for bits of Dexian and odds and ends to make a jig. By bolting, clamping and welding together a ramshackled collection of scrap I was able to fix critical points in mid air and after removing the old tank, use those points to locate the new.
The jig allowed me to position the filler neck and align the mountings on the end plate, holding them in place while I spot welded the mounting bracket and silicon bronze welded the the filler neck. After adjusting for the movement caused by expansion and contraction I tacked the end plates into position in the skin with silicon bronze, then removed the tank from the jig to braze all the way around the joint. Reposition and repeat for the other end.
With the tank closed up the only remaining construction task was to fit the breather pipe. A piece of 15mm steel pipe which I bent to shape with my plumbing pipe bender, carefully positioned and brazed into the top of the tank. I then closed the sender unit hole with a roughly made blanking plate ready to seal the inside of the tank with a commercial tank sealing kit. Although there is obviously no rust inside my new tank it is important to protect the steel from the damaging effects of modern Bio-fuels. The first stage of the sealing process is to use Metal Ready to passivate the inside surfaces and filling the tank with this also proved that there are no pinholes in my joints. I bought a big enough kit to do the Spider tank too, so I’ll prepare that and seal them both at the same time…..But there is something else afoot right now!