Here is how I made mine:
The most expensive part was the blower. It cost me around $50.00 (got it from Graingers, part # 4C443 100CFM blower). I used an old gas BBQ grill as the base. I cut out 3 sides, cut a square out of the remaining side so the 2" dia. gas pipe could sit there ( it stabilized the pipe very well). I went to a metal junk yard an bought an 8" diamater piece of pipe that was 19" long and had them cut a 2/12" hole in the center of it. I used 2" Koawool to line it after I sealed it with Satanite. Once the Koawool was inside of the chamber I made a thin paste with satanite and coated it several times alowing it to dry in between. I cut a hole in the Satanite where the pipe would come into the chamber. I used an end cap (gas) to go inside the chamber. I drilled holes in it (used a .25 drill) to mix the propane and air (approx. 40 give or take). For the above blower I used a reostat(? spell) to adjust the air flow going into the chamber (100CFM is way too much air). I used the existing gas regulator from the BBQ grill and drilled a hole into the elbow just above the bend. See below for details on the blower and pipe assembly. I went to Eagle and bought a plumbing fixture ( I think it is some kind of floor plate) that had a 2" diameter threaded hole. I bought 3 very small C clamps and clamped it to the blower, threaded the gas pipe assembly to it, used wood to brace it up on the grill along with plumbers tape and it works great. I can regulate both the air flow and the gas mixture and it heats hot enough to weld.
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Blower/pipe assembly:
My BBQ grill has a table in front of the side I left on. The end cap sits just inside of the chamber, connected to a 12" X 2" diamater threaded black gas pipe. The 12" pipe connects to a 2" dia. black gas elbow (the one with the gas regulator) which in turn connects to another 12" X 2" dia. black gas pipe. That piece connects to another elbow which connects to a 2" long piece of black gas pipe which is threaded into the floor plate that is connected to the blower. The blower sits under the table protion of my grill to keep it out of harms way. The blower assembly from start to finish looks like square minus one side (sort of like a C made out of straight lines).
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Parts:
1 - 4C443 100CFM blower
1- Old gas BBQ grill (not table top model)
1 - Reostat
1- 8" dia. by 19" long 1/2" thick steel pipe
1- Gas regulator (from BBQ grill)
2- Black pipe (gas) 2" dia. elbows
1- Black pipe end cap (gas)
2- 12" long X 2" dia. threaded on both ends black pipe (gas)
1- Plumbing floor plate 2" dia. threaded hole in it
3- Very small C clamps
12- 1 1/2" thick fire brick (I could not get the bigger ones at time, I also left room for the brick to sit on the bottom of the BBQ grill). I used plumbers tape and stove bolts to secure it and tighten it down with.
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Total cost was about $100.00
The blower, reostat, and black gas pipe cost the most.
BTW I use the 20lb propane tanks and have never had one freeze up on me.
You could also check out this link (http://www.dfoggknives.com/forge.htm) and go to Don Fogg's site as he has great plans for a gas forge. In fact, when I build my next one it will be similar in design to his. I like the vertical aspect of his.
Hope this helps out.
Ravenclaw
