[cmccuist]

Stumps gravity feed smokers are very popular, but expensive. They have a chute that you put your charcoal and wood into. As the charcoal and wood burn in the bottom, they are replaced with the gravity feed. Insulated and temp controlled if you add the fan/temp controller device. Very nice units.

I have a conventional horizontal, offset fire box, 1/2" thick plate smoker that I modified to make more efficient.

Fire bricks in the bottom of the fire box and smoker sections to hold in the heat. Wrapped the whole smoker section with mineral wool and stainless. I welded in a 4" X 3' length of square tubing as a gravity feed for the charcoal, so I don't have to add it every hour. It's very efficient and smokes ribs, butts, and briskets like a pro.