SOB lookin for some help

[SmokingOhioButcher]

For a 20"x 60" x3/8" pipe I came up with volume in cubic inches of 18849.00 and a volume in gallons of 82.
Does this sound right? How do I find out what size fire box to build? I plan on using 2 baffle plates to diffuse the hot spot directly above the firebox opening. 1/4" steel for the firebox should be enough...right? Thanks for any help.
SOB

[Pete Mazz]

Enter the sizes in the PitCalc here:

http://www.smokerbuilder.com/pitcalc/

Use internal dimensions. Shoot for ~105% firebox (FB). It'll tell you what sized throat area to use, although with a center feed it may not be as critical. You may also want to consider adding a shadow plate between the FB throat and baffle plate (BP) to spread out the heat transfer to the center of the BP.

[forty_creek]

My bad I forgot this was a center feed build. Sorry SOB


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[SmokingOhioButcher]

Does this look right?
SOB center feed

Cook Chamber Size

Diameter 20 in.

Length 60 in.

Volume(in³) 18,849.56 in³



Firebox Size

Length 20 in.

Width 20 in.

Height 30 in.

Actual Volume (in³) 12,000.00 in³

Recomended Volume(in³) 6,283.19 in³

% Recomended Size 190.99%



Chimney Size

Chimney Diameter 4.5 in.

Rec. Chimney Volume 600 in³

Rec. Chimney Length 37.7447511205 in.




Air Intake

Length 3 in.

Width 2 in.

Intake Area (in²) 36.00 in²

Count 6.00




Throat Size

Throat Area (in²) 96 in.

[Pete Mazz]

FB is way too big. 18" x 18" x 20" gets you ~103%. When the FB size is adjusted the intakes can be 2 - 2" x 5". The throat also reduces to 52". Chimney to 21".

[SmokingOhioButcher]

Any reason the FB cant be taller than recommended? I like the idea, like a drum smoker, of the fire being farther away from the BP. will it hurt if the FB is bigger than 105%?

[Puff]

Up a bit early huh? From everything I have read, the deviation from that sweet spot in FB size causes difficult fire management and that passes through to the tank and either too hot, so you damp it down and it produces heavy white smoke instead of the magical thin blue smoke and a host of issues that usually require retro fitting of size to restore it back to the correct ratio.

The formula of success and ease of stabil use lies in those numbers, on one of my smaller 9o gallon smokers, I did adjust the numbers to allow a taller FB to allow me to raise the inside grate off of the floor a few inches so the dampers line up below the fire.but, they remain at 104%

My 2cents

[Rodcrafter]

One thing to throw a wrench into the whole process. The calc doesn't really apply to vertical cookers it's for offset smokers. The thing about vertical is the fire/charcoal generating the heat either has to be smaller or another way to prevent all the heat entering the cc. Otherwise it would be way too hot.


Making memories.

[SmokingOhioButcher]

Ahhhhh... the sweet spot! makes perfect sense. and the fact that a smaller fire should be used makes sense since it is techniqly a vertical smoker. Thanks for the info. Frank ....Do you have any wise info for me before I go ahead with measurements? Tom?

[SmokingOhioButcher]

??????????Is there a calculator out there for center feeds?

[Frank_Cox]

The same calculator used for offsets is fine also for center feed smokers. The only thing you do differently as you figure whatever you want for your baffle plate divide that in half and split it up between both sides.

[SmokingOhioButcher]

Do I just leave the top of the fire box open or still put a top in it and cut a damper in the top to open and close?