we've made them before out of old 56kg propane bottles, you need a flap in the top and bottom with a grate inbetween in the bottle, obviously a chimney on top and a resevoir thats a few feet away from the fire with a regulator tap and a good heavy duty tube, we had the tube going into the chimney just dripping on the fire with gravity, we had the bottle glowing red a few times lol