I need a little insight with my UDS

[arcticcanoe]

Hi guys.
Last summer I built 2 UDS smokers, yeah I only need one but I was bored and it's just as easy to build 2 at once. Both are basically the same they both start with three 3/4" intakes around the backs and 2" chimneys. What differs them is one has both a 3/4 and 1" air intake stack with ball valves towards the front. And the second only has one 1" intake stack. For the most part both like to stay around 250F, and don't like the lower temperatures. I would like to smoke around 225F but I have to fight to stay that low.
So I'm chasing the temps all night until early morning when the dew sets in and the outside temps drop and I'm fighting to stay alive this is usually half way through the cook. So the sweet spot is around 250F I guess I could live with that but the dying out at 4:30-5am sucks. So again I got bored over the winter and built a PID with a fan to babysit through the night. Today I finally did a test smoke of a small sirloin roast no big deal. I set the PID to 225F and set the auto tune, up she rose to 280F and it took 2hrs to drop back to 225F, fan kicks in and slowly back up to 250F then creeps up to 265F over the next 4hrs. All the intakes are closed the fan housing I built has a flapper to limit the natural draw of air.
I know this is content heavy but the more info I give you the better help you all can give me.
My question is with the natural draft out the chimney can air still draw down to stoke the coal ( by the way I'm using kingfords lump) and I run the 2" chimney full open and rely on the intake for control.

 

[zippy12]

what is your fuel source? KBB works best for me to even out temps.. Lump tended to burn like crazy...

Is the seal tight on your lid? My uds will pull air from the top when I use my dome lid...

 

[arcticcanoe]

I use lump. I know it can burn a little erratic but I like the taste/smell. Up here in Canada the Kingfords we get is in a blue bag. Out of the brand's I've tried Kingfords usually has the biggest hunks. When I built them I cleaned out the rubber gaskets and from what I can tell the friction fit of the lid is very tight. You even have to bang the lid on and pry the lid off. Using my dome lid doesn't make no difference. The Masterbuilt domes are a perfect fit for my drums.

 

[zippy12]

My bet is on that lump. Webber makes a bricket do a non cook burn and see how it goes.

One more thing is the amount of grease hitting the coals can cause temp spikes. UDS gets hot and melts fat onto the coals.

 

[daveomak]

May I suggest a fiber gasket on the lid... It doesn't take much air to fuel the fire... The fire should go out when the air intakes are closed... (theoretically)... and maybe some clamps on the lid...
something like this to hold the lid tight....

 

[1215]

What Dave said. We have a guy on our comp team with an expensive brand name drum and when we are done with a cook we/he can close the dampers and the fire goes out.


Also, not sure what type of damper (flap) you built into your fan intake contraption but you'd be surprised at how much a fire can draw. Maybe the damper flap isn't enough?


I'm building a UDS right now and the way I'm going to have it built is basically a clone but with a lot of modifications. My goal is temp control and fuel management (I want rock solid temps for long cooks). The way I'm approaching my drum is that without a fan, I want to manually adjust my dampers and I want the drum to sit at temp and HOLD TEMPS for hours. I'm going to have a manual damper (ball valve type contraption) BETWEEN the fan and the fire. This way I can manually set the valve/damper, not have to worry about a drafty fan contraption --and the fan only kicks on if something starts to die out and/or drop below temps.


Only other suggestion I can make is you said you built a "PID". Not exactly sure what that means but sounds like a simple relay --temp drops below a number, fan kicks on until temp rises above that temp. Similar to a coolant temp sensor for a radiator in a car. The thing you have to remember with that is that you may get down to 220 degrees, then the fan kicks on but it could take 3-5 minutes until the heat hits the cook grates/food. But in that time you've now been stoking the fire for 3-5 minutes so when the heat kicks on it'll come bigtime. I ordered a couple Raspberry Pi's and a bunch of temp sensors on Amazon (will arrive tomorrow). Not sure how sophisticated your setup is... Eventually I'm going to attach automated servo motors for the dampers as well. I'm going to be playing with (tweaking Python code) to log temps over the whole cook so I can graph the temp curves. Meaning if temp drops by greater than X over Y period of time then kick the fan on for Z amount of time. Not "if temp falls below X temp turn on fan until temp rises above X temp". Same with heat. I'll need to be careful about a clean burning fire and clean combustion (for flavor/taste) but if temps spike then open exhaust to dump heat and close intake.


Hope that helps and that all made sense...

 

[arcticcanoe]

What Dave said. We have a guy on our comp team with an expensive brand name drum and when we are done with a cook we/he can close the dampers and the fire goes out.


Also, not sure what type of damper (flap) you built into your fan intake contraption but you'd be surprised at how much a fire can draw. Maybe the damper flap isn't enough?


I'm building a UDS right now and the way I'm going to have it built is basically a clone but with a lot of modifications. My goal is temp control and fuel management (I want rock solid temps for long cooks). The way I'm approaching my drum is that without a fan, I want to manually adjust my dampers and I want the drum to sit at temp and HOLD TEMPS for hours. I'm going to have a manual damper (ball valve type contraption) BETWEEN the fan and the fire. This way I can manually set the valve/damper, not have to worry about a drafty fan contraption --and the fan only kicks on if something starts to die out and/or drop below temps.


Only other suggestion I can make is you said you built a "PID". Not exactly sure what that means but sounds like a simple relay --temp drops below a number, fan kicks on until temp rises above that temp. Similar to a coolant temp sensor for a radiator in a car. The thing you have to remember with that is that you may get down to 220 degrees, then the fan kicks on but it could take 3-5 minutes until the heat hits the cook grates/food. But in that time you've now been stoking the fire for 3-5 minutes so when the heat kicks on it'll come bigtime. I ordered a couple Raspberry Pi's and a bunch of temp sensors on Amazon (will arrive tomorrow). Not sure how sophisticated your setup is... Eventually I'm going to attach automated servo motors for the dampers as well. I'm going to be playing with (tweaking Python code) to log temps over the whole cook so I can graph the temp curves. Meaning if temp drops by greater than X over Y period of time then kick the fan on for Z amount of time. Not "if temp falls below X temp turn on fan until temp rises above X temp". Same with heat. I'll need to be careful about a clean burning fire and clean combustion (for flavor/taste) but if temps spike then open exhaust to dump heat and close intake.


Hope that helps and that all made sense...

My lid it tight so no air can come in that way. I even went as far as to cut a slot in a fridge magnet to seal around the small hole for the probe wires. If I close all the vents and chimney the fire dies out like it should. I also get around 20hrs to a basket of lump at around 250F. But if i try to cook around 225F it wants to die and I'm chasing the temps. That is why I built the controller (PID) . If your not familiar with the concept of PID controller, it is not a simple on/off temp controller. In the simplest of terms they can self learn when to turn on and off so they dont over shoot a temperature. Then they can also be setup manually. Because the UDS is so stable and slow to respond to temperature changes the autotune function times out before it drops temp. PID's are mostly use with electric burners, I built mine to also handle an1800 watt element just in case. I also was looking at the HeaterMeter/raspberry pie controllers. As for the damper in my fan it maybe has a 32nd" around the flapper. I might could put an 90 on the nose so the flap lies flat. But in reality there has to be 30 gallons of reserve oxygen in that drum when everything is shut down.

 

[arcticcanoe]

May I suggest a fiber gasket on the lid... It doesn't take much air to fuel the fire... The fire should go out when the air intakes are closed... (theoretically)... and maybe some clamps on the lid...
something like this to hold the lid tight....

Hi Dave.
The lid is super tight. I was planning to form a gasket from high heat silicon and once I do that the lid wont fit as tight and I'll need clamps. For now I have to bang the lid on. I have used the barrel ring clamp, it doesn't make much difference.

 

[arcticcanoe]

My bet is on that lump. Webber makes a bricket do a non cook burn and see how it goes.

One more thing is the amount of grease hitting the coals can cause temp spikes. UDS gets hot and melts fat onto the coals.

Thanks for the insight Zippy. I'll try the brickets I've heard there more stable, and I don't really get any huge temperature spikes. I also haven't used a heat defuser or water pan.

 

[daveomak]

ECTO1 has had great success with his UDS.... Maybe there's something in his videos that will shine a light on something...

https://www.smokingmeatforums.com/threads/uds-builds-by-ecto1.247697/

 

[daveomak]

I noticed ECTO used 1/2" ball valves.... that may have something to do with chasing temps...

 

[red farr]

...why do want to cook @ 225˚ ? .....
Red

 

[daveomak]

Why not cook at 225 or 200.... below the boiling point of water....
I have cooked meats at 138, 145... etc. in my sous vide machine..

 

[arcticcanoe]

...why do want to cook @ 225˚ ? .....
Red

Red
I'm a patient man. lol For the most part I like cooking at 225F just in case I get a spike in temp. That way my fudge factor is really 225F to 250F and not creeping to 280+F.
I do this for the fun and the challenge, and especially the payoff.
There are only two true pleasures in life, and one of them is food.

 

[hardcookin]

I liked using Stumps charcoal in my UDS.
As mentioned, I would check for air leaks.

 

[Bummed]

275 is the sweet spot for my UDS, I can maintain 250 by starting with 1/4 chimney of charcoal but it really wants to creep up to 275 and it gets locked in there with only one 3/4" valve open. It was hard to get away from 225 low and slow but I'm loving this higher temp smoking. I did a 8lb butt a couple days ago and it took 7 hours. Temp stayed at 290 and I let it roll, since it was done earlier than I anticipated I wrapped it and put it in a cooler for 2 hours. It pulled apart so easily and was tender, juicy and a nice smoke ring to boot.

 

[1215]

...why do want to cook @ 225˚ ? .....
Red

I'm building a crazy UDS specifically for temp and fuel management. If you can "set it and forget it" (or have fun/party/drink... or simply sleep at a bbq comp), why not throw some meat on, check on it every few hours while you do house/yard work and enjoy at dinnertime? Isn't "low and slow" the goal? Hot & fast is for the comp guys?