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UDS help please

post #1 of 27
Thread Starter 
Ok fellow UDS users, i've got a situation that I can't seem to overcome so i'm reaching out.

The setup:
55 gallon drum
Standard 2 inch Bung exhaust extended to 6 inches
Four 3/4 equidistant drilled holes with 1/2 x 6 inch black steel intakes
Three 1/2 end caps
One 1/2 ball valve

The Fuel:
Kingsford Original
Cowboy Lump

The Lighting:

Off brand Chimney Starter, started out counting specific number of coals or a specific weight of lump

The Basket:
Weber 18 inch charcoal grate with expanded metal in the form of a circle 8 inches tall, easily holds 10lbs of fuel, normally sits directly on the four intake pipes

The issue:

Starts good, strong, after about 2-3 hours temps start fluctuating bad, even after shaking the coals/lump, inconsistent for remainder of cook and needs tending often

Corrective Action thus far:

Went out and bought 3/8 x 5 bolts that have 1 inch of threads which after mounting to the bottom of the firebasket, raises it to 4.5 inches off the bottom and 2.5 inches off the intake pipes.

Ongoing Problem:

Can't for the life of me load the UDS with one type of fuel and start it with a chimney of the other fuel

Your comments, suggestions and thoughts are greatly appreciated. (My other smokers run fine, this build was at a specific request, trying to get it right before I release it for general use to the user that asked for it)
post #2 of 27
By fluctuating do you mean falling off or dropping then spiking back up?

Try using just a single type of fuel to minimize variation. I would also try using a different brand. Personally I use Royal Oak lump from Wally's

Most drums use 3/4" valves and nipples for air intake. Also it could be that your initial fire isn't big enough to maintain the proper burn rate and is choking out.

Just a few suggestions
post #3 of 27
First off most folks drill 1" holes and use 3/4" pipe. Second, I only used 1 1/2 nipples for intakes. No need for such long intakes. After replacing intakes use 3 1/2" bolts to raise the basket 3" off the bottom. Once you get the intakes taken care of I think you'll be ok.

BTW, how do you have the intakes connected to the drum?

I see no concern with mixing the fuel. Then again I see no real advantage either.
post #4 of 27
Thread Starter 
Ok, got the bolt issue taken care of, already raised it to about 4" off the bottom, guess I could drill out the holes and go up a size to the 3/4 x 2 intake nipples. The current intakes are currently screwed directly into the barrel from the inside out and held in place with locking nuts.

What do you mean, my initial fire isn't big enough to maintain the proper burn rate? Could you elaborate on that point? And yes, the temps keep falling off, sometimes slowly, sometimes quickly.

Your suggestions are heard well, please keep any others coming.
post #5 of 27
How much charcoal are you using in the starter to get things going? I use around 15 bricks for start up. Ya have to make sure they are nice and ashed over before dumping them on the basket.
post #6 of 27
I usually use a chimney full of lit lump to start my fires. Some use a weed burner (the type that looks like a cane and uses small bottles of fuel) but think of it as starting with a match size fire vs. a softball size fire. Just wondering if your fluctuation is coming from a small start on your coals and it is gasping to maintain temps.

Most likely cause is air flow through your fire though. First call on my part would be to increase the intake size and shorten the intake piping. Longer intake pipes will affect your airflow within the drum.
post #7 of 27
Thread Starter 
Normally, when I use Kingsford, I am pretty specific and count out 12-15 briquettes. When I use lump I measure out about 7ozs. I normally add the starter fuel when it's about half way ashed over.
post #8 of 27

Answered your PM, and these guys are giving you good advice as well.

One way or another, we'll get it straigtened out.biggrin.gif

post #9 of 27
You must let the charcoal get a good ash over before putting in the basket. I think the major thing you have here is an air flow problem.
post #10 of 27
Thread Starter 
DDave, thanks for the pm response, yes, i've gotten some good guidance here too, i'm going to go with the consensus and swap out the long intake pipes for short ones.

I remeasured the height of the basket with the new legs attached to it, it has 4" of clearance now.

I saw the idea from a user on another forum site that had the same setup as far as the intakes, but i'm now thinking they incorporated the 3/4 x 6 vs the 1/2 x 6 pipe to make it work. Gonna skip that idea and go back to the KISS method.

Do you all allow your UDS to come up to desired temp before loading or do you all load and go and regulate temp as it rises?
post #11 of 27
I load a full basket and add the lit coals to the middle.

Start with all intakes open. When it hits 200F close all but two intakes, once it reaches 225 close all but one intake and adjust from there. I run 240F with one intake about half open. Of course you have to play with it to see what works best for you.
post #12 of 27
Thread Starter 
Do you have problems with surrounding fuel not catching? Or do you just re-shuffle it all before each use so it gets used at one point or another? Also, where do you place your wood chunks? Do you place them spaced around the basket or all together to one side so that the heat from the fire causes them to smolder in place?
post #13 of 27
I do take the old out and put them on top the new. I have pretty good luck with this method. The wood chunks, 3 or 4 fist size chunks, I put in different parts of the basket so they don't all catch at once.
post #14 of 27
Thread Starter 
Good to know, thanks!
post #15 of 27
I let mine warm up almost completely before I put the cook grate in. Seems to cut down on the deposits from the early yucky whitish smoke that would get on the grate. Then I put the grate on and let it warm another 20 minutes or so. Then I put the meat on and we're off to the races.

I don't have any problem with the surrounding fuel not catching. On the contrary, if I let it get too much air, it will ALL start burning. But that might be the Kingsford Comp. It is kind of light and airy and really wants to burn.

In fact I've gotten to the point where I'll load the charcoal basket about 1/2 to 2/3 full depending on what, I am smoking, dump 8 or 10 well lit, fully ashed briquettes (lit in a chimney starter) in the center, put the basket in the drum and put on one cap. When the thermo on the side of the drum hits 150°, I'll put on the second cap and adjust the valve to about 2/3 open. Then I leave it for awhile and it usually settles in at about 200° on the side thermo which for me is about 250° or so at the center. That's what works for me but each drum is a little different. Mine gets a little extra air I think because one of the caps won't thread on all the way. (Threads got a little messed up when a buddy of mine was tacking it in. icon_redface.gif )

I usually put 3 or 4 chunks against the outside of the basket. Seems to be close enough that the Kingsford Comp will make them smolder.

Hope this helps.

post #16 of 27
Thread Starter 
Ok, another question, but more generalized for everyone.

Has anyone tried the Minion method in reverse? Start with a full chimney of lit coals, put nearly complete ashed over coals into the basket in the middle and then load the rest with unlit fuel and wood?
post #17 of 27
I think some have tried, but it didn't work as well due to airflow problems.

If you are thinking of experimenting and have the time, take a look at this thread:


It is currently 254 pages long and some of it is repetitive but it contains lots and lots of great posts about the trials and tribulations of getting a UDS running just right and lots of modifications that people have tried.

I call it "Advanced UDS Theory". biggrin.gif

post #18 of 27
Thread Starter 
I'll assume since you didn't state it that during your warm up period that's all lid on time?

Ok, must have done something right. After a few more checks, i've come to the conclusion that it definitely is an intake issue as the smoker would not hold temps at all. To further validate what everyone has said, I went out at 11:30 last night and moved the entire fire basket from #4 UDS into #5 which hadn't even been fired yet. The significant difference between the two is #5 has three 3/4 intakes all with caps. I transferred the coals and left the lid off off until it hit 150 and put the lid back on and left the caps off until it hit 200 and capped two intakes leaving the third one uncapped and let it burn. I watched it until it seemed to want to settle around the 287-291 mark with one cap off. Unfortunately it rained during the night (even tho the weather didn't predict it) so I don't know how stable my temps were through out the night, however I think it worked out right because I went out this morning to check/cover everything and took the lid off to find that nearly the entire fuel supply was gone. Will probably put a ball valve on one intake and continue to test fire it some more. Final temp goal is to maintain 225-230 for max burn time.
post #19 of 27
Definitely!! The lid goes on right after the charcoal basket goes in. If I leave the lid off for any longer than is absolutely necessary, the temps will be totally out of control.

When I need to take the lid off to add meat, mop/spritz, or put a temp probe in the meat I shut down all the intakes for about 3 minutes. Then I lift the lid, do what I have to do really fast and put the lid back on.

If I have to do something that is going to take some time, like foiling, I'll take the meat out, or sometimes the whole rack and set it on a table then put the lid back on. After I've done what I need to do and the lid goes back on, I wait another 3 minutes then open the intakes to their previous settings.

post #20 of 27
Thread Starter 
Ok, day two, combining two different techniques i'm trying to establish positive temp control in UDS #5. Recap: 55Gal drum with three 3/4 intakes, two with caps and a magnet to cover the third. ALSO, loaded a specific amount of fuel, only made it two layers high in the firebox after completely cleaning out the barrel from last night's burn session. Started 12 individual pieces of charcoal and let them ash completely over. Poured them into the middle of the firebasket and immediately closed one intake, put the lid on and waited until the temp hit 200 and closed the second intake. Also placed the magnet to cover half of the third intake hole and the temp has stopped around the 224-226 range, time now 5:50pm local. Will track through the duration of the fuel.
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