Stump Clone not hot enough

TravisT · Posted: Dec 24 2007 Post subject: Stump Clone not hot enough

I've been lurking the forums and have come across some similar threads but looking for some advice. I just finished building a stump clone, and I'm test firing it before christmas (which I plan to load it up and see what it can do).

I've had problems getting the temperature high enough and steady. I filled it with kingston charcoal yesterday afternoon after adding a full chimney of red hot coals. I used a hair drier to get the temps up and ensure the heat wasn't backflowing. I had it cranked wide open and the temps got up to right around 350. I throttled back on the valve and got the temps to 225�. The valve was about 1/2 open. I let it run all night, and this morning the temps were real low, and I still had unburned charcoal in the chute. There was no bridge, and there was still charcoal burning on the grate. I cleaned the ash (about 1/2 full) and closed the door back.

I did notice that there was a good bit of moisture on the top door (inside), and I'm wondering if it may just be moisture in the charcoal. The charcoal is only a week old and stayed in the garage until used. No signs of being wet or anything, but one thing I did notice is a bunch of the briquettes would separate down the middle. I don't remember ever seeing this before. I have two bags of lump from academy, and I'm going to try and find more today.

What do you guys think? Thanks for the help,

Travis

Big Mike · Posted: Dec 24 2007 Post subject:

I've got a GF 223 and I know if I left my valve 1/2 open with the smoker empty, my temps would hit 500. I use lump instead of briquettes, but that shouldn't make that much of a difference.

What was the temp in the morning and was that on the door therm or a remote therm on a rack.

As for the moisture on the inside of the chute lid. That is normal. Since the chute is sealed, moisture from the combustion collects on the underside of the lid.
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mds2 · Posted: Dec 24 2007 Post subject:

How large is your ball valve?
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TravisT · Posted: Dec 24 2007 Post subject:

It was probably in the 40's or 50's this morning, and got up to around 60 or so today. The ball valve is a 1-1/2 inch. I have 4 bags of natural lump for my Christmas cook, and I hope things work out better.

Currently, I don't have a thermometer on the door. I couldn't find one long enough locally, so I've been using a remote tru-temp (that I seem to have broken already). I also need to finish welding the outside skin on the big door, as well as stuffing some insulation in between.

How much moisture is "normal" on the top door? A little while ago I had the valve wide open and the temp was HIGH. Since my tru-temp is broken I couldn't tell exactly but the temp coming out of the stack was around 450-475, so it was cooking. Not sure why I can't get a steady temp unless it's fuel related.

Coz · Posted: Dec 24 2007 Post subject:

I think you will find that with the lump and the door ins.and skin it will run better.I ran my clone today and it was around 10 degrees here and windy as all get out.I had to run the ball valve open a lot further than usual but other then that and the fact I forgot to cover her after last weeks cook and had to thaw ice of the door its been fine.

Big Mike · Posted: Dec 24 2007 Post subject:

You will get quite a bit of moisture.

How often do you try and adjust the ball valve to regulate your temp. With a Stumps you only need to make small adjustments and once you make an adjustment it will take a little bit to see the effect because it is such a low air flow smoker.

Also, I found that if I let the temp come up slowly instead of rushing it, the temp settles in better and I don't have to mess with the ball valve as much. So when I light mine I open the ball valve all of the way then I let it come up to about 250. This normally takes about an hour or so depending on the weather. Once I reach 250, I close the ball valve down to where it is only open about 1/2 inch and let the temp settle in. Then I will make small adjustments as necessary to get it to stay around 250. Once it is stabilized I put my meat on and let the temp stabilize again. Then I make a small adjustment to keep my cooking temp at about 230.

By taking the temp to 250 initially that allows me to recover faster to my actual cooking temp when I put my meat in.
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Coz · Posted: Dec 24 2007 Post subject:

What Mike said is very good practice.It is very hard to wait out those little adjustments but it works well when you do.I used to use the hair dryer trick but gave it up and just started allowing myself more time to get up to temp.

TravisT · Posted: Dec 24 2007 Post subject:

So how long does it typically take you to get up to a stable temp? And then after getting meat on, how long before it stables out again? Do you typically have to tinker a bunch once you get it tuned, or will it pretty much coast for the rest of the cook once you get it dialed in?

Also, does the valve position change a huge amount depending on the amount of load? Tomorrow will be my first attempt at using lump, but I'm hoping it will burn a little better. We'll see I guess.
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Bedlam BBQ · Posted: Dec 24 2007 Post subject:

The lump will burn hotter than the briquettes you used previously, so that may help keep your pit up to temp.

What size is your exhaust and cook chamber?

On my clone, the cook chamber is 24" x 24" x 48". The chute is 5" x 5" with a 3" x 5" opening into the cook chamber. It would take about 2 hours to come up to 250. I've gotten that down to only 30 minutes with the use of a Stoker. After Christmas, I'll be removing the 5" x 5" chute and going with an 8" x 8" instead.

Also, before the Stoker, I would have to make slight adjustments to the ball valve during the entire cook -- I could not just set it and leave it there during. But now with the Stoker, I choke it down a little lower than I would have normally. This way the Stoker has to force the air through the ball valve to maintain the pit temp.
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Big Mike · Posted: Dec 25 2007 Post subject:

I usually allow myself 2 hours to get the temp up and settled in before I put on the meat. This gives the smoker time to warm up thoroughly. Once you put the meat on I would just keep an eye on the temp to see what it is doing. Then if you go over your cooking temp bump down the valve.

Once you get it set, it will hold fairly steady. You will have to keep an eye on it cause it will drift up or down some. Especially if the wind picks up, dies down or changes direction.

The valve will change some for a bigger load. It just depends on the type of meat and how much. For 12 butts and 2 packer briskets mine will have to be about 1/2 open to run at 230. Now as the meat warms up I may have to adjust that down some.
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TravisT · Posted: Dec 25 2007 Post subject:

My cook chamber is 22x24x40, the opening is about 2.5x6" and my chute is 6x8. Towards the bottom, the chute tapers out on 3 sides about an inch, so the surface area of the lit coals is about 8x8. I may make some changes to that, but I'm happy with the size of the chute I went with.

I have yet to insulate the bottom of the smoker (ran out of sheetmetal), so the ash box is un-insulated on three sides and the cook chamber is uninsulated on the bottom. I'm really thinking about getting a stoker, just due to the "set it and forget it" factor.

I put my brisket on about 1 hr ago, and my temps are staying right around 225. My valve is around 3/4 open right now, and I have a bucket over it to cut down on wind effect.

As for all that meat you mentioned with your valve half open, I'm not sure how your doing it, but that's what I've heard from most people. It seems that a typical setting for around 225 is somewhere between 1/8 and 1/4 open. Apparently something on my cooker needs to be tweaked because I'm way over that.
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TravisT · Posted: Dec 25 2007 Post subject:

Oh, I left out my exhaust size. I'm running a 4" stainless pipe about 12" long (left over diesel exhaust pipe). There isn't a baffle on the exhaust. I don't remember the stumps having one either. Is that correct?
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Big Mike · Posted: Dec 25 2007 Post subject:

No, no baffle on the exhaust.
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TravisT · Posted: Dec 26 2007 Post subject:

Well I have to say that my cook went very well - so did the meat. I think I will be making some changes to the pit before welding everything up completely. I put the brisket on yesterday afternoon at about 1:30, followed by the butt and shoulder at about 9:00. This morning I woke up and had almost ran out of lump, but caught it just in time. My temps had dropped down to 195. Added my 3rd bag of lump, along with 3 slabs of ribs, two whole chickens (halved), some ABT's and a pan of baked beans. At about 3-4pm everthing came off.

The brisket was at 200 when I moved it to a cooler to rest, the shoulder was at about 180. This was by far the best cook I have done to date. Everyone was pretty impressed. Everthing was so tender and juicy. The smoke ring was about 1/2" thick on everything. I used a little too much brown sugar in my rub, and the bark was a little dark, so I may scale back on that a little next time. Thanks for the help and suggestions. Merry Christmas.

TravisT
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Big Mike · Posted: Dec 26 2007 Post subject:

Glad to hear everything came out well.
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Harry Nutczak · Posted: Dec 27 2007 Post subject:

Add a stoker to that clone and you'll really love it,

My last cook I was dealing with temps in the single digits, My stumps was up to cooking temp in less then 20 minutes and stayed there until I shut the air intake down and capped the stack, 24 hours later it was still hovering at about 180 degrees, 48 hours later, it was still around 90 degrees inside the cook chamber.

And I agree that nothing happens all that fast with a stumps when adjustments are made, and it takes twice as long to get the temp back down if you overshoot it.
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