"William Wixon" wrote:

years ago i saw a website where a guy was making two stroke engine expansion
chambers by cutting out the shape in two sheets of sheet metal welding them
together at the edges and and inflating them using a pressure washer. it
seemed like a whole lot easier than working the sheet metal on a planishing
hammer. the parts came out SURPRISINGLY round and well formed.
surprisingly few wrinkles, etc. i couldn't find that webpage but here's a
guy doing the same thing on youtube....

http://www.youtube.com/watch?v=I_Z3AIFSd60


That was worth watching! Thanks.