A real smoker is made of heavy steel and uses real wood. It ought to have two chambers. A firebox for the fire and another chamber that will provide for low temperatures and long smoke times.
I agree. I have an old pressure vessel that I got from a job site. It is 8' tall 24" diameter. We built a fire box on the side. The vessel itself is 7/8" thick and once you get it heated up we can hold the temperature the same for over 24 hours with just minor adjustments. The only problem is it is so heavy out tractor wouldn't even pick it up with the bucket so we have to inch it up a couple inches at a time and when we got it stood up that is where it stayed.