Firebox questions

[D . Jur]

Some video...
https://youtu.be/0BUcHMnvQjw

[Big T]

I have a few questions. Did you build a rack to keep your fire off of the bottom of your fire box? How are you controlling the air into the fire box? Do you have any type of damper on the exhaust stack? I watched your video but I couldn't tell how you were running the pit, just your temps which didn't look too bad to me.

[D . Jur]

Yes, I have it all.

As for the rack ... I tried to make a grate, but I did not like the fact that the coal bed practically does not form and the temperature in FB changes more sharply.
So I flexed a sheet of metal in an attempt to recreate a round bottom.

This sheet is lying on a square tube. I'm working on this for now.

[Dirtytires]

Your fire absolutely needs a rack to burn properly. It is important for air to get to the fire as well as ash to fall thru so as not to clog the fire. Sitting on a solid surface will not allow it to burn efficiently. If you had a problem with the coals falling thru and not forming a coal bed then the gaps in your grate were too big. Many of us use a simple box made of expanded metal and it works great. It will nicely keep the coals on top and still allow airflow and ash to get thru. Another nice trick is to form it into a loose 'V' shape so the logs all stay together.

I am able to simply toss 2 small splits in my firebox every 45-55 min and it will run at a constant temp. I don't have to knock down my ash, arrange coals or do any other fire adjustments for even a long 12 hour cook. Just open the door, toss in the logs and close the door. I suspect you have a lot more work to do and if you have your firebox open 4 times an hour for 5-10 min each time, your fire never has a chance to stabilize and is just burning wide open, like a campfire, and not being controlled by the airflow.

[D . Jur]

To be honest, the photo is bad,
a log of smoldering, but usually lights up instantly ...
Is there a fundamental difference in running on a 500 gal smoker, when the FB has a flat bottom and charcoal pastel is formed in the basket using an intake window, or a round bottom when it is built right on the floor using an open door?

[D . Jur]

Your fire absolutely needs a rack to burn properly. It is important for air to get to the fire as well as ash to fall thru so as not to clog the fire. Sitting on a solid surface will not allow it to burn efficiently. If you had a problem with the coals falling thru and not forming a coal bed then the gaps in your grate were too big. Many of us use a simple box made of expanded metal and it works great. It will nicely keep the coals on top and still allow airflow and ash to get thru. Another nice trick is to form it into a loose 'V' shape so the logs all stay together.

Thanks for the tip, I'll try to overlay one grid on top of another.

Guys, what about the first shelf from the stack and the temperature on it? Should it be lower than everyone else, or is something not working correctly?

[Dirtytires]

On a traditional offset, it is typical for the cook chamber to be hottest next to the firebox and then have temps decrease as you move towards the chimney.

[dacolson]

This is a standard offset, right? On a standard/traditional offset he grate directly next to the stack will usually be the hottest. It's the choke point for all the heat and smoke before it enters the stack. When you close the damper in your stack, it causes back pressure the drives the temps up across the rest of the grates. If your grate by the stack is cooler, I would wonder if your stack is choked off too much? I just finished my latest standard offset and have been doing a lot of cooking on it. Stack damper adjustments and fire placement in the FB influence heat dispersion on the pit a lot. I've found on my 130 gallon pit that a fire closer to the door in the FB and keeping my stack damper closed about 3/4 keeps my temps the most even across the grates. Fire size matters a lot too. Still learning a lot about how the pit runs though.

[D . Jur]

This is a standard offset, right? On a standard/traditional offset he grate directly next to the stack will usually be the hottest. It's the choke point for all the heat and smoke before it enters the stack. When you close the damper in your stack, it causes back pressure the drives the temps up across the rest of the grates. If your grate by the stack is cooler, I would wonder if your stack is choked off too much? I just finished my latest standard offset and have been doing a lot of cooking on it. Stack damper adjustments and fire placement in the FB influence heat dispersion on the pit a lot. I've found on my 130 gallon pit that a fire closer to the door in the FB and keeping my stack damper closed about 3/4 keeps my temps the most even across the grates. Fire size matters a lot too. Still learning a lot about how the pit runs though.

Yes, this is standard offset, that's right.
I've been cooking on it for almost a year now, the meat turns out to be excellent, but I'm tired of constantly dancing with the rotation of meat on the shelves ... that's why I started a rework.
I also keep the fire almost at the door itself, but the damper in the stack is always 100% open. Tomorrow I'll try to cover it by 3/4 and watch, thanks.

[dacolson]

Every pit is different for sure. It’s surprising the heat is lower at the stack with it wide open. Mine is hatter at the stack with it open. I’m no pro though. I’d try running it for 30 mins at different damper settings. Just to see how yours performs.

[D . Jur]

I tried playing with the damper ... no effect, this shelf is still the coldest.
Those. when the averages (top and bottom) show 265f, the lower left barely reaches 220, and above it 250 ilm is also 265 ...
The firewood is the same, oak, dry, the size was specially chosen not large.
Tried it as before, just on a flat bottom, and on a rack, as Dirtytires advised.

Any thoughts what is wrong with this shelf?

[Brewmaster]

I think you might have better luck if you lower the stack exit down to the lower food grate level, this way the heat is forced down before it can exit. A plenum or collector will help with better draw and less of a hot spot there right at the smoke exit. After the mod you should find the upper grates running a bit hotter than the lower grates, but your temps should be a bit more even from side to side.

I tried playing with the damper ... no effect, this shelf is still the coldest.
Those. when the averages (top and bottom) show 265f, the lower left barely reaches 220, and above it 250 ilm is also 265 ...
The firewood is the same, oak, dry, the size was specially chosen not large.
Tried it as before, just on a flat bottom, and on a rack, as Dirtytires advised.

Any thoughts what is wrong with this shelf?

[hogaboomer]

Have you tested the thermometers to see if they all give the same reading? I don't trust a door thermometer at all. You need a digital thermometer with probes.

[D . Jur]

Have you tested the thermometers to see if they all give the same reading? I don't trust a door thermometer at all. You need a digital thermometer with probes.

Yes, I tested them with boiling water.
I will need to try digital with a probe.

[Dirtytires]

Actually, 220-265 is not a bad temp swing on a traditional offset. That may be just about the best your pit will do.

[D . Jur]

Actually, 220-265 is not a bad temp swing on a traditional offset. That may be just about the best your pit will do.

Sounds like a bad diagnosis for a patient ...

[D . Jur]

I think you might have better luck if you lower the stack exit down to the lower food grate level, this way the heat is forced down before it can exit. A plenum or collector will help with better draw and less of a hot spot there right at the smoke exit. After the mod you should find the upper grates running a bit hotter than the lower grates, but your temps should be a bit more even from side to side.

I tried playing with the damper ... no effect, this shelf is still the coldest.
Those. when the averages (top and bottom) show 265f, the lower left barely reaches 220, and above it 250 ilm is also 265 ...
The firewood is the same, oak, dry, the size was specially chosen not large.
Tried it as before, just on a flat bottom, and on a rack, as Dirtytires advised.

Any thoughts what is wrong with this shelf?

the grates are so located at the level of the exit to the stack.

But it looks like we need to make a collector and place it lower than it is done now.

[Devin&Bobbi]

Yup. Here you go.
The first two show how I built mine. The throat baffle is on the back of the firebox, inside the cook chamber. The third pick shows the throat baffle in front of the cook rack.






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Hi, I'm new here, my wife and I are building a 250 gallon offset with a round firebox. I really like the design of your baffle, would it work on a round firebox? Are there any pictures of one on a round firebox? If not do you have any recommendations for what to do with a round firebox? We were considering mounting the firebox a bit higher, where the throat opening is about half above and below the grate level. Kind of like a LoCo smoker. It's that a bad idea? Any advice would be great as the firebox is built and ready to be mounted. Thank you

[dacolson]

I’ll PM you so we don’t hijack D . Jur’s post.

[D . Jur]

Hello guys. Well i redo my stack to collector...

and fixed problem with coolest shelf, near the stack.
Look at this video.
https://youtube.com/shorts/2bqKyQvQ5c8?feature=share

[dacolson]

Love that collector! Awesome. Probably more work than you wanted to do but super glad for you that it's working well.

[Big T]

[Berriesbbq]

Hi all! This is my very first post here. Very much looking forward to getting to know all of you and learning from each and every one of you. I'm currently building my first Offset smoker! I'm using a 264 gallon tank as a cooking chamber. Here's a picture of the progress so far. I'm currently preparing the firebox. Using two old propane tanks for this. The FB will have a double wall and insulated. ID is 29.5 inches. The straight part measures 27.75 in. I calculated the additional square inches from the dome after the straight part. Together with the calculations, I made on the feldon calculator, my FB would be 1,5% too big. Here's my question: since it's my first build I don't know if 1,5% is sufficient? Do any of you have more experience with this?
Would rather make it a bit too big than too small (I can always cut a bit more off) Not seeing myself weld a piece back on
Thank you so much already for the replies!
Kr,
Bert

[Dirtytires]

Berriesbbq-

Welcome to the boards. I would suggest you start with a post in the introductions section so we know who you are and then post a separate thread with your question. Tagging questions on to someone else's thread will not get the attention you are looking for and is confusing for someone trying to follow a particular build or issue.

With that said, I'll wait to answer your new post so as not to hijack this discussion.....