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UDS temp trouble- Needing some help!

SmokinLogs

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My UDS is close to being done. It’s close enough that i have cooked on it twice, and the Q did come out delicious. The main thing needing finished is the charcoal basket, but I’d like to get it operating a little better before I do the finishing touches. Currently I’m getting temps up to 200-205.

The base of the charcoal basket is an industrial air filter lid, 16 inches diameter with about 3 inch high sides, steel. I have the bottom cut out with a piece of perforated stainless steel inserted. I also have eight 1 inch holes cut on the sides. Soon I will be adding more of the perforated stainless to the sides (planning for 12 inches deep, maybe a little more)so I can load it up for long smokes.

I have three 3/4 inch air inlets centered three inches above the bottom of the drum, fed by stainless 3/4 inch nipples, 90 degree bends, with 6 inch risers. The ball valves are full port valves.

My ash pan has 2 inch sides on it, and the charcoal basket has 3 inch legs, so there is a about an inch or so gap between the sides of the pan and basket which is right where the air inlets are pointing.

For my exhaust I’m using the 2 inch port on the lid with a 6 inch riser. Attempting for more heat I removed the 1 inch cap that came on the lid as well. I was able to get my temps to hang around the 225-250 range by cracking the lid on one side and holding it open a little by wedging a screwdriver there, but that is still with all three ball valves wide open.

Most people tend to have no problems maintaining temps with one 3/4 inch ball valve, which tells me my issue is probably air related. Idk if the perforated stainless might be restricting airflow to the coal too much, but I’ve seen some of the charcoal baskets the you can buy pre made or in kits that have solid metal sides and are slotted only at the bottom to let ash drop, so that makes me lean away from the perforated metal being a problem. Maybe I need to cut the sides of the ash pan down to one inch (I doubt this is the problem), but I’m just trying to brainstorm anything affecting my airflow.

Both times i cooked I have used kingsford original. The first time I started the fire by lighting about 6-7 briquettes in the chimney. That seemed to take forever for the rest to light enough to come up to temp, so the second time I used a couple starter cubes. I thought maybe starting with more lit briquettes might help, but I tried keeping the lid cracked quite a bit which got my temp up over 300, and I could see a lot of coals were fired up, then I put the lid back on, but it still just slowly dropped the temps down around 200. So, I don’t know what to try from this point. I know this is throwing a lot of information out there, but any ideas or words of wisdom would be appreciated!

I don’t have any pictures of the charcoal basket right now. I will take some soon. This looks similar to the base I started with, and I have eight 1 inch holes on the sides with the bottom cut out and perforated stainless in its place.
93D66554-FA37-4739-AF62-90945F59BAC4.jpeg


This is what the perforated stainless steel sheet looks like. It’s about 1/8 inch thick with about 3/8 inch holes. When I take some pictures of the actual basket I will update on all the measurements. I’m hoping for some insight from the UDS guru’s on here. Thanks in advance!
EB4E8EAE-2BC0-4014-8A5A-CCD5647D90C9.jpeg
 

fivetricks

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Hmm. Best I can give you is a comparison. Here's my UDS basket. I run 3 valves and I have problems keeping temps down if anything.

20181001_175311.jpg


No Ash pan or other airflow restrictions underneath.
 

daveomak

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May I suggest your exhaust hole is not big enough... The very good solution is to drill 6-8 3/4" holes, about 2" below top of the sides of the drum for even air/exhaust flow, using a step drill... and plug the bungs on the lid... They can be plugged depending on wind direction... It's important to have room for exhaust gasses or you will not get enough inlet air flow... I would start there before I did any mods to the fuel site...
 

trailmonkey

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Your exhaust is plenty big for temps well over 400 degrees. I use 2" bung holes on mine and if it starts raining I screw a 6" nipple in with a 90 degree and I still draft strong. I have had mine over 500 before easily. Get your coals glowing red and then when you dump them in the basket and then leave the lid off for 10 minutes.

Your problem is airflow from your intakes. 3/4 size will work but when you add 90s and extensions you restrict terribly. Most the guys you see maintaining temps with 3/4 intakes just have the valve straight out of the drum. With your setup you are probable choking it for air when your trying to get the fire "settled" in. Once your fire is settled in you might be ok. The problem is not your exhaust trust me but rather most likely what i said. I made a drum once using two 1" valves with 90s and a 10" extension and I had all kinds of issues. Once going it was fine but trying to get temp increases took all day. Fix your intakes either by eliminating the 90s and stacks, or by going to a 1 1/2"-2" stack. With your setup 3/4 is WAY too restrictive. I personally have been using sliding draft doors for a few years and you want to talk about flow? I can crank mine from 225 on up to 400 in as little as 15 minutes using only the 2" factory bung hole in the lid for exhaust.
 

SmokinLogs

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Hey guys, sorry it took so long to get back with everyone on the build, trial and error, and solutions. I wanted to wait until I got some pictures to show what all I did to fix my temp regulation and consistency problems.

Daveomak, I did what you suggested. I drilled eight 3/4 inch holes in my lid for the exhaust. This helped some with getting my temp up a little higher, but I still had problems keeping the temperature up if I wasn’t constantly messing with the basket or stoking it. Sometimes the fire would almost go out.

Trailmonkey, my airflow restriction wasn’t at my intakes, it was at the basket itself choking out the air to the coals and I believe not letting enough ash drop.

I’ve got great consistent temps these days. I will post some pictures of all my updates later.
 

daveomak

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I have read where one member attached a steel rod to the basket and it went through the UDS wall... He would periodically shake the basket to let ash fall to the bottom of the drum... Larger expanded metal and longer legs, may help the oxygen deprivation...
Glad you are making headway....
 

SmokinLogs

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I’m Daveomak, I went with eight 3/4 inch holes for the exhaust like you recommend. Makes a good draft and I like how it spreads the smoke/heat evenly around the cook chamber.
E69BAFF1-0F33-4F3D-8C09-EFEE46367B03.jpeg


This is my original charcoal basket that gave me all the problems. The perforated stainless steel at the bottom just wasn’t letting the ash drop enough, and choking out the air to the coals. If I wasn’t stoking it or giving it a good shake from time to time the fire would put itself out.
356F1B99-8AD8-4E8A-8F08-C3AE19977406.jpeg


Here is what I did to remedy the situation. I got trigger happy with the hole saw. I did 4 times the original amount of holes on the sides. I don’t think this was a huge problem but I figured the more air flow the better. I think what helped the most was taking the hole saw and cutting some bigger holes in the perforated bottom evenly spaced out. This gave better air flow and better ash dropping. I don’t know for sure but I am guessing the funny star design helps to hold on to the odd sized and partially burned pieces of charcoal so I get a good long burn. I haven’t found any unburnt coals in the ash pan after my cooks. I can smoke for 12-14 hours on this basket loaded up full. I am very happy with the turnout. Hopefully this helps the next guy with these types of issues. Thanks to all you that gave me the advice.
4ADF0EE1-D405-40F5-8F2F-AF023BF2A1B7.jpeg
855AF9A8-37D2-47EA-A266-AA12068F4282.jpeg
 

daveomak

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I like it.... thinking outside the box works well..... What is the "basket".... a converted "chicken frying" frying pan ???
 

SmokinLogs

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I like it.... thinking outside the box works well..... What is the "basket".... a converted "chicken frying" frying pan ???
It’s actually something I found in the scrap metal bin at work. It WAS a lid to an industrial size air filter housing, already sandblasted to bare steel. I think it serves a much better purpose in my smoker lol.
 

daveomak

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I used to go through the scrap bin at work weekly... You'd be amazed at the stuff I built out of scrap... OH!!! how I miss those days.....
 

SmokinLogs

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I used to go through the scrap bin at work weekly... You'd be amazed at the stuff I built out of scrap... OH!!! how I miss those days.....
Yeah daveomak, I try to set aside and bring home whatever might serve a good purpose to me often. I built almost my entire UDS with mostly scrap. I think I bought the grating and thermometer, that’s it. I may even build a second one with the extras. I just have to keep my eye out for another drum.
 

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