Firebox question?

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jason3856
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Firebox question?

Postby jason3856 » Thu Mar 30, 2017 7:08 am

Could someone please give me some advice on what size my firebox should be? I am using a 6'x36"x3/8th pipe. All advice is greatly appreciated.
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Re: Firebox question?

Postby OldUsedParts » Thu Mar 30, 2017 7:45 am

Welcome to the Forum, Jason - - - just hang on because I'm sure your question will be answered shortly by one of our many "Gurus of Q" - - :tup: :salut:
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Re: Firebox question?

Postby TX1911 » Thu Mar 30, 2017 8:33 am

Welcome to the forum! Check out Feldon's pit calculator. It's smarter than I!

http://www.feldoncentral.com/bbqcalculator.html
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Re: Firebox question?

Postby jason3856 » Thu Mar 30, 2017 9:58 am

Thanks for the quick answers. That calculator really helped me out. Is there a formula or calculator for door size dimension?
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Re: Firebox question?

Postby GRailsback » Thu Mar 30, 2017 12:10 pm

I believe there is an email link at the bottom of the page that goes to a guy here on the forum that is extremely knowledgable on the pit building process. You can either email him, or I am sure he will see your post and reply at some point.
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Re: Firebox question?

Postby TX1911 » Thu Mar 30, 2017 12:47 pm

Scroll halfway down and look for:

Firebox Air Inlet Opening
Enter the size of the firebox air inlet (intake) from the outside.
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Re: Firebox question?

Postby k.a.m. » Thu Mar 30, 2017 2:02 pm

jason3856 wrote:Thanks for the quick answers. That calculator really helped me out. Is there a formula or calculator for door size dimension?

Welcome to the forum Jason. Are you talking about your cooking chamber door or firebox door?
Always remember slow and steady wins the race.

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Re: Firebox question?

Postby jason3856 » Thu Mar 30, 2017 2:14 pm

Well I guess I can knock out 2 birds with one stone by asking for both cooking chamber and firebox door if all possible.
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Re: Firebox question?

Postby k.a.m. » Thu Mar 30, 2017 9:04 pm

jason3856 wrote:Well I guess I can knock out 2 birds with one stone by asking for both cooking chamber and firebox door if all possible.

On a 72" x 36" chamber I would go with two doors roughly 32.5" wide. Cutting 1" from the caps and leaving a 5.5" center bar. Top cut would be about 7" down from 12:00 and 1" below 3:00.
What size firebox are you running?
Always remember slow and steady wins the race.

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Re: Firebox question?

Postby jason3856 » Fri Mar 31, 2017 6:54 am

According to the calculator its looks like my firebox will be 26"x36"x26". That puts me at 24336.00 cubic inch. Recommended is calling for 24416.64. Do you think that is my best bet?

I am also going to add a slower cooker to this pit as well. Do I need to calculate that in the size of firebox as well? What would be my best size for smoker?

Once again thank you so much for your advice it is greatly appreciated.
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Re: Firebox question?

Postby k.a.m. » Fri Mar 31, 2017 8:33 am

Your firebox is too small in my opinion.
This is the numbers I would try to run with.
Link to BBQ Pit Calculator

For the firebox door you have options on what you would like. Look at the builds in my signature and see if these would be something you would like. You can have the door facing your chamber door side and put the intakes on the end. i like this option when I can use it.
Always remember slow and steady wins the race.

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Re: Firebox question?

Postby Mgdwj » Sun Apr 02, 2017 11:16 am

K a m what should the target firebox differential be at? I know it is recommended to have a slightly larger firebox then what is calculated but, slightly is pretty general.
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Re: Firebox question?

Postby k.a.m. » Sun Apr 02, 2017 2:35 pm

I like to go 10% to 15% larger. Basically if you plug in the perfect 100% and start enlarging the firebox watch your exhaust height when it starts to change you're altering the recommended 1/3 rule draft. Too much and you completely change the way the cooker performs. I am not saying this is a bad thing it is just something I do not do.
Always remember slow and steady wins the race.

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Re: Firebox question?

Postby Mgdwj » Mon Apr 03, 2017 9:26 pm

k.a.m. wrote:I like to go 10% to 15% larger. Basically if you plug in the perfect 100% and start enlarging the firebox watch your exhaust height when it starts to change you're altering the recommended 1/3 rule draft. Too much and you completely change the way the cooker performs. I am not saying this is a bad thing it is just something I do not do.



I had planded on going about 20% larger firebox. To much? I also plan on a vertical warmbox.
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Re: Firebox question?

Postby k.a.m. » Tue Apr 04, 2017 5:45 am

jason3856 wrote:According to the calculator its looks like my firebox will be 26"x36"x26". That puts me at 24336.00 cubic inch. Recommended is calling for 24416.64. Do you think that is my best bet?

I am also going to add a slower cooker to this pit as well. Do I need to calculate that in the size of firebox as well? What would be my best size for smoker?

I consider vertical chambers at the end of a cooker just an extension of the exhaust just figure the horizontal chamber and make the exhaust on the vertical large enough in diameter and about 12" tall.
Always remember slow and steady wins the race.

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My Hybrid cooker.
Competition trailer #2.

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