Heat drops after 5 hours.

[gyfd107]

I'm new at this and am using a small UDS made from two ten gallon drums welded together. Before I started smoking with it I seasoned it by getting it up to 350-360 for about an hour and then took the temp to 225 just to see how well I could regulate it. It worked great and I shut it down after about 5-6 hours.
The first time I actually smoked a shoulder roast and it worked fine and help the temp right at 225 with very little adjustment but after about 5 hours the temp dropped to about 200 and I couldn't seem to get it back up even by opening more vents. After I shut it down I checked and there was still charcoal in the basket. I used the minion method so I don't have to open the smoker to add wood or charcoal. I'm wondering if the grease dripping on the coals is causing my problem and as the charcoal level gets low the grease is drowning out the charcoal?

Any suggestions would be appreciated. So far this the only problem and the roast still made some great pulled pork. The only thing is smoking is interfering with my golf. Can't do both at the same time.

 

[noboundaries]

I don't have a UDS but I've seen something similar in my WSM at about the same 5 hour point.  Early on I would carefully pack my fuel because that's what I read.  No longer.  Now load my fuel by dumping. 

Why the temp drop?  As lump and briquettes burn two things happen; they develop an insulating layer of ash plus they compact.  The ash happens more so with briquettes than lump, but both still ash over.  Both ash and compaction cut down on the airflow around the surface of the hot coals regardless of vent settings.  The insulating ash and the natural compaction of the fuel reduces the surface area of the fuel exposed to air that can burn.  

In my WSM when that happened I have a long set of tongs I used to "GENTLY" stir the burning fuel to knock the insulating ash off the fuel, instantly providing more surface area that can burn.  I could get another 90 minutes or so of steady temps without adding any more fuel before the temp starts dropping and it's time to stir again. 

The point is air feeds burning fuel, and it is the surface area of the fuel that must be exposed.  The main reason lump burns hotter than briquettes is due to more air space in the irregular shape of the fuel load, exposing more surface area.  I mostly use identical sized stamped briquettes though so to maximize the air space in the fuel I just dump them in haphazardly and bury wood chunks in the fuel, maximizing exposed surface area.   

I now have an air pump installed and that fire can burn for hours and hours without any stirring at all.  8.5 hours is the longest I've gone so far since installing the pump.  The pump provides just the right amount of air to keep the set chamber temp stable and the fuel burning efficiently.          

 

[gyfd107]

Thanks for the info. That seems to make sense. I try to shake the smoker every once in a while to try to knock the ash off and that probably helps till it burns down and then that is probably just compacting the briquettes that have gotten smaller as they burn. Right now i don't have an access door to the fuel. To add or stir the fuel I would have to take the lid off and remove the meat to get access to it. Maybe I'll consider that so i could get to it and add if needed without removing the lid.

 

[daveomak]

Thanks for the info. That seems to make sense. I try to shake the smoker every once in a while to try to knock the ash off and that probably helps till it burns down and then that is probably just compacting the briquettes that have gotten smaller as they burn. Right now i don't have an access door to the fuel. To add or stir the fuel I would have to take the lid off and remove the meat to get access to it. Maybe I'll consider that so i could get to it and add if needed without removing the lid.

GYFD, morning..... think about drilling a hole in the UDS and attaching a steel rod to the charcoal basket... then you can shake it from the outside... Might work OK.....

Dave