24" backyard smoker build. Some questions...

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45 acp

Original poster
Sep 3, 2013
I'm about to build a smoker and had a couple questions. Also if you have any tips/tricks, please share them. I will post pics of progress as I go.

It will be 24" x .300 wall pipe, 4 ft cooking chamber and 2 ft fire box. Single door on the chamber with 2 slide out racks. Fire box will also have a slide out rack for burgers or steaks when needed, and will have a warming area on top of the fire box. 

How big does the hole need to be between the firebox and cooking chamber? 

Also, when I weld the firebox to the cooking chamber, should the top of the fire box be about at the mid-line of the cooking chamber? Or should it be lower?

Thanks for any help. Im cutting the pipe and end plates today and will probably get started with the build next week. 
The opening between the firebox will be determined by volume. There are several bbq pit calculators out there that will help with that calculation. Also I know DaveOmak has alot of good advice on building smokers.

As for the fire box meeting the smoke chamber. I went below center line. I wanted my RF plate atleast 3 inches from the bottom of the first grate. But again once you know how big your opening between the chamber and FB needs to be then you can adjust the marry point of the 2.
FB volume is 21,700 cu. in. .....
FB/CC opening..... 87 sq. in.
RF plate 20.5" wide ... stop short of the end of the CC at the 6" mark for the length...
Top of the FB 6" above the bottom of the CC..... Connect the RF plate to the top of the FB..... I would insert the FB 6" or so into the CC... and plan on a heat shield with at least a 1/4" gap and extend it into the FB 12" or more....

...click on pics to enlarge......

The FB to CC opening should be 6" high and the outer edge the same as the circumference of the CC....
Draw a 24" circle... measure up 6" and draw a line across the circle at that 6" point... the smaller of the two segment is the FB/CC opening...

The fire box...... I would make it rectangular in shape.... Front to back, 24".... top to bottom 24".... From the CC to the end of the FB, 18".... That will be 50% of the CC and plenty of room for ashes and coals....

The exhaust stack 370 cu. in. ... 4" ID stack 30" above the CC for height and attached to the CC using a plenum..... 1/2 way between the grate and top of the CC or something like that....

With the stuff I sent you in the PM.... this should help...

We have many knowledgeable members that can help also..... Specific questions would help us get straight to the point... We are here.... Ask away....

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Sorry to hi jack your thread but I have a question. Going to help a friend build a rf smoker that is 24" diameter. The pipe is about 72" is that to long?
Thanks for the replies everyone. However, I am not building a reverse flow.....

Oh well, I think Dave answered my main question, which was how big to make the opening from Firebox to CC. 

Also, being that I work at a pipe yard, I am making the firebox out of round pipe. I've already got the pipe cut at 52" for the CC and 24" for the firebox. Im cutting out the end plates and welding them on today. Then I will prop it up in my shop and start the real fabrication. 

Thanks again. Feel free to give your opinions. I probably wont really get started until next week, so its not too late to make some changes if needed..
For a 52" CC, using a round FB.... make a football shaped FB/CC opening...

CC 23524 C. I.
FB/CC opening 94 C. I.
Using the circle calc. figure 47 C. I. for the segment area and turn that segment area upside down for the football shape...

4" seg. hgt. = 50" segment area... chord AB is 18"...... Soooooo... a football 18" long and 8" high will give you a 100 C. I. FB/CC opening... That will match up to the 2 pieces of pipe when butted together....
....click to enlarge ...
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Finally got started. I screwed up the first one by trying to go with a single door CC. The pipe "sprung" open on me slightly when I made the door cutout which wouldnt allow for a good tight fit on the door. So, I set that one aside and went and got a new piece of pipe. This one is 3/8 wall thickness. Gonna be a heavy SOB but it should retain heat extremely well. Been messing with it for about a week and its finally starting to resemble a pit. I changed my plans and now it has double doors on the CC. Im only able to work on it here and there so the progress is not going real fast, but I hope to have it close to done around next weekend. Heres a few pics. 

Made a little bit of progress. Got the racks framed and installed. Still need to finish the top racks. Started making the legs and frame for the wood rack but ran out of time. Wouldn't you know it, I bought 20' of 2 x 2 angle for the legs and wood rack and ended up 2" short of angle on my last leg...LOL. 

Got the main doors all strapped with flat bar. Im waiting till Im done working on the inside of the pit before I weld the hinges on and install the doors, but they are pretty much ready to go. Also got my adjustable baffle fabricated. You can see the round bar, which sticks out the back of the pit and will control the positioning of the baffle. I am also making some tuning plates to help even out the temps across the CC. 

I think I should have it done this week and then ready for sandblast and paint. Wont be long before I can fire it up and pile meat on. 

Looking great so far, perfect size in my opinion! Nice to have pipe like that too. That stuff sure seems to be hard to find not far from you. I might have to make a road trip!
Thanks for all the nice comments.

Got the doors on yesterday. I have a pretty good seal around the edges. Got the legs and wood rack tacked on as well. Probably wont get much done today 'cause its cold and raining outside and I need to catch up on other stuff anyways. Still hoping to have it done and painted by the end of the week.

45, morning....... I been looking and haven't seen any tuning plates.... And then I realized we haven't discussed them.....
Sooooo, here is where they go, in the event you haven't heard of them..... They move the heat down the CC toward the exhaust, the plates are usually 3-4" x 1/4" steel flat bar, there is a gap to allow some heat to rise to the food.... the plate nearest the FB is placed tight to the FB and then spaces between the plates increase... spaces probably begin at 1/4" or so nearest the FB .... Below is how they are placed...

...Tuning Plates Explained.....
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Thanks DaveOmak.

Yes, I am aware of the tuning plates and I will have them in my pit. I'll make some once the pit is complete. 
Now that's a nice looking pit.... must be nice to say... "Ahhhhh... I don't like that.. give me another piece of pipe and I'll start over" ... :biggrin:
Sorry for not updating on the progress. Been busy. The smoker has been completed and I have cooked on it a couple times. I am very happy with the way she cooks and holds temps with minimal effort. It will hold consistent temp for over an hour and then when it starts dropping I just throw a small log or two in there and it comes right back up and holds for another hour or so. Very little work and more time to visit with guests and drink beer.  

Heres a couple pics prior to taking it home, and also one during its first cook after seasoning.


So, I knew it would have a hotspot near the FB, and it does. It cooks about 30-45 degrees hotter near the FB. Not too bad. I was planning on having tuning plates in there but now Im wanting to put a flat plate with holes in it instead. I guess you would call it a convection plate of sorts? 

I have a 24" x 24" plate that is 1/8" thick. I will trim it to fit inside on the shelf that I made, and then plan on drilling smaller holes near the FB, with the holes gradually getting bigger as they get further away from the FB. Would this be ok? Do you anticipate any issues with this idea? Its the same idea as tuning plates without having a bunch of different plates. 

Also, I see on some illustrations with tuning plates, that the first tuning plate nearest the FB is angled upward. Is this necessary? Do I need to angle up the end of my convection plate nearest the FB? What is the point of the angled plate? I already have a baffle in the pit as you can see in the pics. 

I hope I am explaining this in a way yall can understand. Basically the main CC will have the convection plate under the grill nearest the FB in door #1. In door #2, or the door/grill furthest from the FB will not have a plate under it. The door/grill furthest from FB already cooks fine. I am only trying to control the direct heat under the grill nearest the FB. 
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