well u should use steel that is what it would have been made of , u can use about 18 or 16 gauge cold rolled steel , then make a buck out of high density flake board stacked to the thickness of the tank , prob will be 2 pieces thick depending on the tank thickness, then route edge of buck with round edge router bit , once this is done u can sand in more shape to the buck if needed ,once this is done u then want to anneal your metal with a preferably a rose bud tip torch , but what ever u have will do , heat the metal till it is more plyable then clamp on to your buck and hammer metal to the shape of the buck , of course this will have to be twice 1 for each side , but as shallow as a bicycle tank is should be able to use a single buck routed on both sides then weld your two sides together . if u want the tanks to actually hold fuel , u need to test for leaks after welding and of course have to add gas cap and bung for fuel outlet . u can take air compressor and pressurize the tank and sparay bottle a liite water with few drops of soap in it . leaks will bubble . then u can creme the tank it is two part , a metal etching step and creme sealant step or second step. or radiator shops can do it for u also . then skin coaT WITH BOND O . BODY WORK . hope this helps. u can see books on it at places like barnes and noble or whatever bookstore , do it yourself section , look for metal fabriacting books , names bob munroe , or ron covell , some of the best metal fabbers ever . and u can see a lot of different ideas and ways tanks can be built . MAKE IT REAL MAKE IT FROM STEEL.
