Quoted:There was a how-to with videos for making one out of pvc pipe also.
worked well.
Quoted:I made one like 5 years ago and posted a how-to in team
ETA Pic
http://img824.imageshack.us/img824/682/flamey.jpgIt's pretty simple with off the shelf parts, all you really need is a 5 gallon metal tank, a backpack frame, some compressed argon (or other gas that's non-flammable), a welding regulator, a blow torch with extended reach nozzle, and a trip to Home Depot for some pipe and fittings
Using PVC scares the shit out of me... I've seen the same video, kid used PVC tubing in a giant "0" to hold denatured alcohol and pressurizes it.
I would never use PVC as a pressure vessel for gasoline, I know people make spud guns using it, but we tried making a small PVC tank at first and tested it with water and compressed air and at about 80-90 PSI it failed and blew apart! Also, the kid taps threads into the PVC pipe for ports, which is also a great failure point waiting to happen.
Use a metal tank rated for those pressures or don't do it at all.