I built a smoker out of a 60 gallon air compressor tank. I had originally designed it with the fire in the bottom on a grate with the air intake on the bottom left hand side. This system has not worked all that good, so I would like to put a firebox at the location where the air vent is now. I am looking at using a steel pipe about 12 to 16 inches in diameter and about 24 inches long. Any one know of plans for a firebox?