Oh, and Please vote for me in the Keep Warm contest!
Also, as of 2013, I'm considering making a few of these and selling them in the UK if anyone would be interested? They will all be finished in ultra high temperature black paint like the one in the second image.
Step 1: Materials
-Gas Bottle (Large (47kg) or medium, but not the really small ones. The main image is a medium one.)
-A ~6 Inch Diameter Pipe 90 Degree Bend (I Used Lorry Exhaust)
-A length of ~6 Inch Diameter Pipe For Chimney (I Used Lorry Exhaust)
-Something For Handle, (I used two bolts welded together and a scrap piece of metal for latch)
-A Section Of Heavy Duty Hinge, Average Door Hinge Wont Be Strong Enough
-Box Section For Air Vent (~3 inch square for medium bottles, double for large bottles)
-Length Of Rod For Air Regulator (Optional, for damping fire down)
Step 2: Drain
Turn the bottle upside down, then wait for a lot more gas to come out.
Wait until gas stops coming out, then unscrew the valve from the bottle, which requires plenty of force, and probably a vice. A little more gas should come out.
Turn the right way up, then fill with water, using positive displacement to remove the last of the gas.
Leave the water in until you are ready to cut.
Bottle should now be gas free :)