Over the past several days I've done multiple test burns using various settings, varying loads of fuel and what not. Hopefully my results will help those who presently use UDS and for those yet to come.
-55 Gallon Drum DOT Approved, thicker gauge steel
-18 inch weber charcoal grate with 17 inch diameter expanded metal, 8 inches tall fire basket, standing 4" off the bottom of the drum
-Kingsford Original Charcoal
-Wally World brand chimney starter
-Two 3/4 x 2" intakes, One 1" intake hole with a magnet for adjustable coverage
-Initial fuel load equaling roughly two layers in basket when spread out
What I have concluded over the past several days are the following:
-For long, consistent burns at low temperatures the following process with the magnet final setting to cover 1/2 of the intake will produce a settled temp around 230, I used 12 coals ashed over:
Where I suffered was in constant consistency due to the diameter of my fire basket based on my initial fuel load. To compensate for this as well as eliminating a majority of the hot spots from the charcoal being placed ideally in the center of the basket, take the 12 pieces of ashed over charcoal and place them in various locations within the basket. This will ALSO ensure that your more of your fuel is burned evenly top to bottom in the process instead of all of your starter fuel burning straight down to the bottom and the outer fuel not getting ignited. It will ALSO resolve the issue of having to occasionally shake the basket to jumble the fuel around to continue consistent burning as well as knocking any built up ash off the fuel. When the fuel was placed in the middle, yes the burn was good, for a period of time but as it burned through to the bottom, i lost heat, slowly over a greater period of time, but none of my outer fuel ignited. Again, another reason for spreading out your hot starter fuel.
Start time = 6:50pm when the temp stayed between 225-230 for 5 minutes of monitoring
Two hours into the test, the temp had dropped slowly but significantly enough to 217 (at this point magnet intake moved to full open). Three hours into the test the temp sat at 210 (at this point one intake cap removed and magnet intake moved to half), Three and a half hours (I got anxious) temp was just below 200. At this point the lid was removed, basket was shook, and fuel was stirred and redistributed and slightly stacked. Recapped one intake and set magnet intake at 3/4 open, lid replaced. Temps climbed back to 266 and settled down around the 250 mark briefly and then continued to drop Within 45 minutes of 250 reading temp had dropped significantly back under 200 and continue to fall which I contribute to the remaining unburned fuel being too spread out to be ignited to continue to maintain desired cooking temps.
Either more fuel to further fill the basket to near capacity and placing starter fuel spread out over the surface or use a smaller basket that holds the same capacity of initial load in a more confined area with the same amount of starter fuel will produce ideal to near optimum cooking conditions with magnet intake set at covering just over half for extended cooking periods. I hope this will help those who continue to desire to use their UDS and those who have not yet had the enjoyment of cooking on one but someday will.
*NOTE* This test did NOT include any wood.