Thursday, May 25, 2017

aluminum cota 348 fuel tank

I'm slowly getting my Montesa 348 back together so Noah and I can ride in the woods. I was going to start working on the fiberglass fuel tank that I previously had sealed, but it's in rough condition and honestly I don't really like how the final fiberglass looks if I can't nail the original gel coat look and color to the original. I decided that now that I have a bit more metalshaping skill then when I first built the 348 that I should maybe try to make an aluminum fuel tank. 

I happened to have a large sheet of 3003 aluminum so the night before last Noah helped me pull some paper templates from the original tank and then I set about cutting some panels yesterday that I could shape and then weld together.  The forms are pretty simple so they didn't require much shaping. I used a simple homemade dolly, that my Dad had made years ago, to shape the top panel. I wound up using my gas welding flux and gas torch to tack the tank together at school and then I finished by TIG welding. I still have some hammer and dolly work to do, but I got a decent seam that I could file down and shape a bit. In these photos I had yet to TIG weld the other side of the tank, but I worked before dinner and got the other side closed up and filed down. I can begin work on the seat pan area and then I'll do all the final shaping and smoothing before I weld in the tunnel. 

The tunnel will be tricky as the original tank was small, but maximized the usable space around the engine since a trails bike is all about lightweight, thinness and economy of space. The fiberglass was perfect for that reason as it could be an irregular shape very easily. I'll figure something out though. I'm already thinking that I won't extend the seat like the currently stock version as I may want a flatter style seat to allow the rider to squat down into the seat area a bit lower similar to the style of modern trails bikes. I can always make another version of the tank if I decide to go completely stock. I'll see though once things start to come together.

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