Roasting coffee is a hobby, that is fun, and rewarding. The drum is all Stainless Steel. The stirring vanes are tall, 2 are straight, and 2 are angled. The angled vanes move the drum coffee back and forth in the drum, this aids in the mixing, and the size of the vanes act as paddles to move the hot air in the same manner as a hot air roaster, combining conduction and convection heating ( this benefit is realized when you have a motor that will spin the drum 20 rpms or more) with a 6 rpm motor then roasting is mainly done by conduction.
I made it to run on a standard rotisserie set up, 5/16" sq rod, and a 6 rpm motor.
I removed the fire diffuser that came with grill, and replaced it with a piece of 12 guage sheet metal. This not only diffuses the flame, but conducts a good deal of heat. The drum sits in the motor drive on one end and rides in the solid bearing that came with the rotisserie in a bracket on the other end. I have roasted 1/2 to 4 pounds of coffee with it. It makes a great coffee roaster. I also found out it does a good job roasting peanuts too. Peanuts roast at a lower temp. then coffee. I roast mind at 350 degrees.
When roastin 1 to 2 lb of coffee, I preheat the grill to 450 load a cold drum and leave the setting alone. the heat drops to 400 and builds back up to 450 in about 6 min. first crack happens at 11 to 13 min. and 2nd happens at 13 to 15 min.
For 3 to 4 lb loads I preheat the grill to 500 degrees, load a cold drum, and leave the settings alone, the heat will climb back to 500 degress in about 6 min. First crack at 14 to 16 min and second crack at 16 to 18 min. I am very happy with this drum and find it produces quaility coffee.