So a while back when I first saw Bronc76's design, I thought it was fantastic. I'm sitting around home on medical leave without much to do, so I gleaned as much info as I could find in this thread, took some measurements of my own 55 gallon drum awaiting conversion into a UDS, did a little math with the various online smoker spreadsheets, then plugged it all into Google's free CAD software package called SketchUp, and here's what I came up with:
I took a few liberties with Bronc's original design, but did my best to come up with an actual usable model that I could someday fabricate from, or at least use as a starting point. I checked all airflow measurements against multiple calculators online so I imagine this should be a workable design. (Feel free to speak up if you notice anything amiss!)
Let's start with the firebox. I used Bronc's original dimensions, 18" x 18" x 20".
The calculators suggest 19.44 sq in of intake vents to feed the fire. I went with four 2" x 3" openings, or a max of 24 sq. in. if wide open.
In the shot below, I removed the firebox door so it was easier to see the feed from firebox to cooking chamber. Calculators suggest 51.84 sq. in. I went with a 5" x 10.5" opening, or 52.5 sq. in. There's another just like it on the opposite side for the left hand drum.
Looking into the right drum through the firebox opening:
More on the way...