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Temperature swings on my home build.

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12ring

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I built this smoker and based all my numbers off a pit build calculator.

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It works great for the most part but I do have some temperature difference across the grate. I added tuning plates to try and remedy the problem but either it isn’t helping or my spacing is off.

I’ve been up since 3:00am. I’m smoking two prime briskets right now for my buddies daughters graduation from nursing school. I’m trying to average 275° but I’m struggling. When I add a split the temperature raises of course but the stack side gets about 50° hotter than the fire box side. When the woods burns up and I only have coals, the temperature across will get with in + or - 5° of each other.

My question is why is there a 50° (hotter on the stack side) difference when a split ignites but when it burns to coals the temperature is almost the same across?

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I’ve cooked some really good stuff on it but it does drive me a little crazy that I have the temperature difference across.

Here’s a few cooks.

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If heat is building up on the stack side after you add a split, it almost sounds like it isnt exhausting fast enough and heat is pooling up on that end. Im no expert but its the only thing that would make sense to me.
 
That makes some sense to me, the splits are probably throwing off a greater amount of heat then the coals/embers. If adjustments to the exhaust are out of the question, perhaps utilizing a burn barrel and only using the coals/embers in the pit will save some headache?
 
Are you running the exhaust wide open? if not I would do that and try to control the temp with inlet air
 
Exhaust was going to be my guess as well. Something is drawing all of the heat toward that end and that seems like the logical answer. Perhaps it is drawing too well and before the heat can actually dissipate on the firebox end, it is being forcefully drawn too quickly to the exhaust end. That is a very nice build, by the way.
 
ronbrad62 said:
Exhaust was going to be my guess as well. Something is drawing all of the heat toward that end and that seems like the logical answer. Perhaps it is drawing too well and before the heat can actually dissipate on the firebox end, it is being forcefully drawn too quickly to the exhaust end. That is a very nice build, by the way.
Click to expand...




I should have mentioned the exhaust. It’s definitely not drawing weak. It draws really really good. Yes I was running it wide open at first but then closed it off a little. I was thinking it was drawing to forcefully and dragging all the heat across to quickly. I’m starting to think it’s the adjustment of the tuning plates along with the draw.

Right now I let the last split burn down and temps across we’re exactly the same. I added a split and I’m at 20° different. I can live with 20° no problem but 30°-50° will make me crazy.


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That is a clean looking build. I would agree with the others about playing with the draft/draw. That beer can is in the way so I can't see whether the vent pipe is enters the cooker above the cooking grate, or below the cooking grate. This alone can have an effect on how the heat and smoke moves across the cooking chamber.
 
So there we have it. Too much exhaust or not enough. Beautiful cooker! Fiddle with the exhaust until you get it dialed in. If you can't get where you want then maybe more or less intake. Maybe an angled baffle plate that forces heat down under the grate a little will help. I've never been a fan of tuning plates.

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thirdeye said:
That is a clean looking build. I would agree with the others about playing with the draft/draw. That beer can is in the way so I can't see whether the vent pipe is enters the cooker above the cooking grate, or below the cooking grate. This alone can have an effect on how the heat and smoke moves across the cooking chamber.
Click to expand...



Here you can see I have the exhaust closed off some but it still drawing hard.

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Here is the exhaust pipe where it enters the cook chamber.

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Here’s the briskets after 4 hours.

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pjtexas1 said:
So there we have it. Too much exhaust or not enough. Beautiful cooker! Fiddle with the exhaust until you get it dialed in. If you can't get where you want then maybe more or less intake. Maybe an angled baffle plate that forces heat down under the grate a little will help. I've never been a fan of tuning plates.

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Click to expand...



Thanks for the compliments on the cooker. I’m proud of it.

I do have a angled baffle plate right now. Next time I open it up I’ll try to take a picture of the plates and baffle unless the briskets are in the way.


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I've never been a fan of tuning plates. In my old offset, all they would ever do is just move the hotspot around and/or weaken the draw. What prompted you to use tuning plates in the first place? Was there a significant hotspot at the firebox end? With any traditional flow HOS, you might be forced to accept having a hotspot somewhere (eg next to the firebox).
 
sthamm said:
I've never been a fan of tuning plates. In my old offset, all they would ever do is just move the hotspot around and/or weaken the draw. What prompted you to use tuning plates in the first place? Was there a significant hotspot at the firebox end? With any traditional flow HOS, you might be forced to accept having a hotspot somewhere (eg next to the firebox).
Click to expand...

I was 50° or so hotter on the firebox side and people told me to try tuning plates.
 
There was a thread on here not long ago about some high school kids (in Texas, I think) that built a smoker in metal shop class and added some find to the timing plates to force the heat and smoke upward and kind of mix it up in the cook chamber. If you can build a smoker like that, you can certainly add a couple of find and see if that helps.
 
This Texas Smokemaster was the only traditional offset I ever owned that ran nearly dead even side to side. I never thought to take pics of the inside. See if you can zoom in and see the angled baffle plate and the 2 plates that run the entire length of the cook chamber that is full of identical size holes. It also has my favorite intake design. Slotted holes below the fire grate. That is the one cooker I regret selling. I miss it like 16Adams missed his sob. [emoji23]
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Maybe your splits are too big? Try adding smaller splits more frequent? Tuning plates are a Band Aid for poor design. Not saying yours is poor design, it seems fine. I'd ditch the tuning plates though and just deal with the 50* firebox hot spot. Use it to your advantage and put a big water pan or something on that end. Tuning plates kill your draft and convection and turn it into a smokey oven. A 50* hot spot on the firebox end would not bother me.
 
Here’s one of the briskets from yesterday. It was good and everyone liked it but I’ve done better. I needed another hour or so but I was pressed for time because the party was about to start.

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Here’s a picture of how I had the tuning plates set up. The first one out of the fire box is slightly angled.

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Here’s a look at it from the inside of the fire box.

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Here’s my intake. You can see it’s below the fire grate.

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I feel like the design is correct. It might be user error and I just need to dial it in better wether it’s intake adjustment, exhaust, split size. Who knows. It’s fun figuring it out though.

I caught a ton of fish in Alaska last week so I really need to figure it out so I can nail the salmon on it.

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