Re: Simple cylinder shaped gas tanks...
Here are three views of a juice can size. The small line is a sight gauge and works pretty well. Upper fitting is for a vent as the gas cap seals things up so there would be a vacuum otherwise. Filler tube is a 3/4 copper plumbing fitting and th cap is a brass hose fitting. Inside the cap is a rubber sealing ring. Under that I place a leather seal so that it does not leak at all. The hose fittings are not barbed so require a little more attention for a tight hose fitting. Zip ties work well and on the gas outlet a hose clamp is a good idea. There is no fuel shutoff at the tank since it is just a section of copper tube soldered in place, so I use an inline brass shutoff further down the gas line. Works fine. Last photo shows an earlier version of the tank with the filler tube on the end instead of centered and it is not covered in leather. If you were not going to use a leather covering the fuel outlet could be a regular shutoff/barbed fitting soldered in place. With leather you have to consider how to fit the leather over things. It is still possible to do if you make the stitch line intersect the fuel outlet. I found that I prefer having the shutoff close to the carburetor rather than reaching under the tank... matter of personal preference. I can't find any photos on this machine of a tank being made. If you're interested I'll see what I can find on discs or make one and take photos as I go.
If you want one, but don't want to make it PM me and I'll make one for you.
Someday when I grow up I will probably lose interest in toys with wheels, but until then...