East Bay hardware hacker Tom Sepe refitted a 1967 Tote-Gote offroad motorcycle to run all-electric, then modded the chassis in steampunk finery, including gorgeous inlaid panels and a whistling steam-boiler hanging off the back-end. Be sure to catch the video!
When I was building it, I took a fire extinguisher tank. It all came down to aesthetics. I was looking at my drawings, figuring out where it would go. The steam boiler came from an aesthetic need, form before function. And the fire extinguisher fit what I wanted. So I cut a hole in the bottom of the tank, slipped a pipe in it, welded it on both sides. So that then I had a chamber with a through tube, which became the flame tube. It's not very efficient; there should be more coils in there. But on the other hand, if I crank it up really high, then you get flames shooting out the back of the bike. Which is cool.