Originally Posted by Salsa
Here is a tip on sheet metal welding to minimize distortion.
Cut the metal .090-.120 inch or so long on each weld edge and bend it "out" 45 degrees. When you mate them together you get 2 edges to weld together. You might need rod to start it, but after you get started, try to not add weld. Just burn it down to the corner you want. You don't get much heat into the sheet of metal.
An alternative method is to round the corner "inward" about 1/4 - 1/2 inch from the weld to make a stiffened edge.
Charley Curnutt of Curnutt shock fame broke his collar bone in about 1970 and built a bike while he was recovering. A few months later I broke mine so I had to built a bike too. I built a sheet metal framed bike with the "tank" surrounding the engine including under the engine. I built a leading link front end.
I think I understand what you are talking about with bending the two pieces outwards and then burning the seam, makes sense. I'm making this tank from aluminum seems like that would put more heat in the metal due to the amps required to melt back the seam. Do you have any pics of what you are talking about because I'm a little fuzzy on it right now and I want to make sure we are talking the same thing.