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Pit building ratio calculator
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Tom C
BBQ Super Pro


Joined: 21 Jul 2007
Posts: 1851
Location: N. California

PostPosted: Thu Sep 18 08 2:12 pm    Post subject: Pit building ratio calculator Reply with quote

When I started my first smoker build last fall I was fortunate to find the Smoke Ring. There were many members here that gave me the information that I as a newbie needed to build a smoker that actually worked. Very Happy

Probably the most important post I found here was Alien BBQ's pit ratios.

During the build I created a spreadsheet that helped me check and
recheck my ratios as needed.

With Mike�s blessings I made this sheet available at first by e-mail and now via download to anyone that has a need to check their ratios on their build. I think the sheets will help answer some of the questions I see pop up now and again when people are having a hard time with the ratios.

UPDATE 4-2011
Now in a web page version!!
Fellow Ring memeber feldon30 has come up with a web version of the calculator! I think it is a very clear and simple version that anyone can use. EXCEL NOT REQUIRED! Thanks Morgan!

http://www.feldoncentral.com/bbqcalculator.html


If your feeling nostalgic or just want a excel spread sheet version of the calculator, you can still follow the links below to my sheets or the one created by dodis.

Excel Spread Sheet Versions (Calculator 2.0)
Because people were having problems with the original calculator, I have made two new sheets that I hope will clear up some of confusion. Please give me some feedback for the new sheets.
Follow this link to the new sheets.
http://webpages.charter.net/tomchism/BBQ%20CALC%20Forms/BBQ%20Smoker%20Calculators.htm

Another option is to check out this new version of the calculator created by Smoke Ring member "dodis" (Mike).
Mike has a great working knowledge of Excel and came up this version that allows the user to make choices about the smoker design and proceed through the form accordingly.
Take a look and let Mike know what you think.

http://webpages.charter.net/tomchism/Dodis%20Calculator/

Yet another tool! This one lets you calculate the area of a firebox to cooker opening that is round on the bottom and flat on the top like we see on many round cook chambers with square fire boxes. It's an Excel spreadsheet created by fellow member "Catman". Thanks Doug!
http://webpages.charter.net/tomchism/additional%20calc%20sheet/Copy%20of%20Firebox%20opening%20-%20curved_Simple-1.xlsx

For thoes without excel, you can now try this:
Follow this link http://www.openoffice.org/ and down load Open Office.org. It's free!
Once you have it downloaded and installed, you will be able to open and use excel files!
Then follow the link below to downlaod the calculator files.
http://webpages.charter.net/tomchism/New%20calc%20files/
Save the files on your computer where you can find them and then open them with Open Office.

It's a little work to get it all set up and going but hey, it's all free!

Good luck on your build!

Tom C
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Homemade offset smoker 24"x48"
Charbroil CB900 grill


Last edited by Tom C on Thu Feb 16 12 12:44 pm; edited 8 times in total
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HillbillySmoker
BBQ Pro


Joined: 25 May 2008
Posts: 913
Location: SW Missouri

PostPosted: Thu Sep 18 08 5:39 pm    Post subject: Reply with quote

Thanks Tom, another post that they need to sticky. they need more than one moderator here.
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BBQMAN
BBQ Super All Star


Joined: 13 Jun 2005
Posts: 15432
Location: Florida

PostPosted: Thu Sep 18 08 5:49 pm    Post subject: Reply with quote

HillbillySmoker wrote:
Thanks Tom, another post that they need to sticky. they need more than one moderator here.


If you send the request directly to SoEzzy, he will make it happen if appropriate! Wink

Unlike some of us, he doesn't have the time to read every post! Laughing
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"I Turned A Hobby Into A Business".
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HillbillySmoker
BBQ Pro


Joined: 25 May 2008
Posts: 913
Location: SW Missouri

PostPosted: Thu Sep 18 08 5:52 pm    Post subject: Reply with quote

Just curious, does the website belong to SoEzzy or is he just the moderator?
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BBQMAN
BBQ Super All Star


Joined: 13 Jun 2005
Posts: 15432
Location: Florida

PostPosted: Thu Sep 18 08 6:00 pm    Post subject: Reply with quote

Garry Howard owns the site, SoEzzy is the moderator.

Actually, the mod was a fairly recent addition.

Garry is a lot more lenient than a lot of forums, one of the things that makes this site so great.

On some forums if you post a link to another site etc. it is censored.

Unless it's a serious infraction, we are (usually) left to ourselves.

This site had grown A LOT over the years, and IMHO is THE best place to go for non-biased BBQ opinions!
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Awning Guy
BBQ Pro


Joined: 23 Aug 2008
Posts: 760
Location: Riverside Ca.

PostPosted: Mon Sep 22 08 6:55 am    Post subject: Reply with quote

Tom, Thanks for taking the time to do all that work. I'm glad I had this info, what I had planned myself would have turned into a "300lb thing" rusting next to the shed.
I will be updating my build soon, Life is living me at the moment.
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Tom C
BBQ Super Pro


Joined: 21 Jul 2007
Posts: 1851
Location: N. California

PostPosted: Mon Sep 22 08 11:30 am    Post subject: Reply with quote

Your welcome Awning Guy. Im happy to be able to help. These calculations are a good guide but some builders have shown that you can play with the numbers some and still get a good operating pit.

For people like me that had no idea on where to start, Alien BBQ's ratios made a world of difference.

Like BBQ Man said, this site is about the best site going for information and we are allowed a lot of freedom. Even with that, I still asked both Alien BBQ and SoEzzy for permission before creating the links.
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Charbroil CB900 grill
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HillbillySmoker
BBQ Pro


Joined: 25 May 2008
Posts: 913
Location: SW Missouri

PostPosted: Mon Sep 22 08 11:45 am    Post subject: Reply with quote

Tom C wrote:
Your welcome Awning Guy. Im happy to be able to help. These calculations are a good guide but some builders have shown that you can play with the numbers some and still get a good operating pit.

For people like me that had no idea on where to start, Alien BBQ's ratios made a world of difference.

Like BBQ Man said, this site is about the best site going for information and we are allowed a lot of freedom. Even with that, I still asked both Alien BBQ and SoEzzy for permission before creating the links.


I agree, thanks Tom, Alien, Gary and SoEzzy. takes a special person to spend their free time to do things like this to help others. i would moderate if they would let me Cool
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hogleg64
Newbie


Joined: 31 Aug 2006
Posts: 29
Location: southern illinois

PostPosted: Sat Oct 04 08 7:53 pm    Post subject: Reply with quote

thanks for the info,I'm not sure what I need to download to use it,but I'm sure it will come in handy before we start cutting and chopping.
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jackh
Newbie


Joined: 20 Oct 2008
Posts: 47

PostPosted: Tue Oct 21 08 10:16 am    Post subject: Reply with quote

im a newbie to pit building. im about to start a tailgating pit build this week and im glad that ive found this site too

what is the calculator for?
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dinger
Newbie


Joined: 13 Jan 2009
Posts: 85

PostPosted: Tue Jan 13 09 6:18 am    Post subject: smoker sizing Reply with quote

Hey Mr I am going to build my own smoker and the cooking area is 20 inch diameter by 44 inches long. What will be my fire box size its inlet and outlet size and the chimney diameter and length I tried the calculator and couldnt get it to work. My Bad
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Tom C
BBQ Super Pro


Joined: 21 Jul 2007
Posts: 1851
Location: N. California

PostPosted: Tue Jan 13 09 8:17 am    Post subject: Reply with quote

dinger,

The opening sizes are calculated based on firebox size.

The rule of thumb is that a firebox should be about 1/3 the size of the cooking section.

If you were to use a square firebox you could use 17"x17"x17".
Based on that size, you would need the following:

Air inlet to the firebox area of 14.74 sq. in.

Firebox to cooking chamber opening of 39.30 sq. in.

Chimney length based on the use of 5" dia. pipe is 35.20", or 55.0" for 4" dia. pipe.
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Charbroil CB900 grill
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dinger
Newbie


Joined: 13 Jan 2009
Posts: 85

PostPosted: Tue Jan 13 09 8:47 am    Post subject: Sizing Reply with quote

Okay now the size of my smoker is going to be 20 inch dia by 44 inches long the cubic volume is 13816 cub inch. the volume of my fire box will be 1/3 of that which is roughly 18 inch dia by 20 in volume of roughly 5000 cubic inches. the fire box Air Inlet Opening circular is 12.72 Volume 127 sq in. what does this mean. And the Fire Box to Cooking Chamber Opening is Circular 40.69 Volume of 1299.71 what does this mean. Im sooo confused Heeeeelppppp Sad Sad
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Tom C
BBQ Super Pro


Joined: 21 Jul 2007
Posts: 1851
Location: N. California

PostPosted: Tue Jan 13 09 11:27 am    Post subject: Reply with quote

This might help clear it up. I guess it can be confusing.


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dinger
Newbie


Joined: 13 Jan 2009
Posts: 85

PostPosted: Wed Jan 14 09 7:20 am    Post subject: smoker Reply with quote

Okay gentleman iam the rookie in the crowd so here goes. Which is the better fire box round or square. Would it be better to have a 7 and a 1/4 inch whole into the cooking chamber or a rectangular 14x3 and how do you damper 4 fire box inlet holes 2 1/16 cant this be just one whole. lets get these basic questions out of the way because i have soooo many. Thanks
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dinger
Newbie


Joined: 13 Jan 2009
Posts: 85

PostPosted: Wed Jan 14 09 7:48 am    Post subject: Dingers smoker Reply with quote

Just another quick question i am going to build the cooking chamber out of 14 gauge metal. Should the fire box be made out of heavier say 3/16 . and do you damper both the fire box intake opening and the cooking chamber intake opening.
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Tom C
BBQ Super Pro


Joined: 21 Jul 2007
Posts: 1851
Location: N. California

PostPosted: Wed Jan 14 09 8:43 am    Post subject: Reply with quote

What ever configuration on the openings that fits well in the smoker. That's why I made up the calc sheets whenI made my smoker, so I could re-work the dimesions of the openings to fit but insure the sq. in. was still correct.

As far as round or square firebox goes, it's a matter of preference or what you have on hand.

Preference again on dampers for the inlet to the cooking chamber. On the firebox inlet I was talking about three holes at 2 1/6" for the firebox mentioned. One way to do it would be like this:
http://www.tejassmokers.com/images/Spring_Handle_on_Firebox_Door.jpg

Make your firebox as heavy as you can to hold the heat better.
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dinger
Newbie


Joined: 13 Jan 2009
Posts: 85

PostPosted: Wed Jan 14 09 10:23 am    Post subject: smoker sizing Reply with quote

Thanks Tom C.I am just trying to get everything straight in my head and then to pen and paper . Where on a 29 inch dia cooking chamber would i start my bottom grill. Should i place my chimney stack slightly bellow this grill off the end and to be 20 inches of stack. [from the chart]. Now to keep even heat in the chamber i should have tuning plates right ? now how high in the cooking chamber should these be placed. Thanks for all of your info.
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Tom C
BBQ Super Pro


Joined: 21 Jul 2007
Posts: 1851
Location: N. California

PostPosted: Wed Jan 14 09 11:40 am    Post subject: Reply with quote

dinger,

Your getting to the areas where you can do things any number of ways. I would place the grill near middle in the cooking section to maximize the size of yout cooking surface.

Yes, I would lower teh chimney to the grate level or aeven a little lower if you place it off the side. Tuning plates will help even out the temps. across the cooking section. In my smoker the plates sit about 6 inches below the grate or grill.
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vinny



Joined: 20 Mar 2009
Posts: 8
Location: Connecticut

PostPosted: Fri Mar 27 09 10:39 pm    Post subject: Reply with quote

I've been looking for information to start to build a USD. I went back to the top and found it. In the forum go to COOKER then LESONS LEARNED IN PIT BUILDING. I found just about all I needed to get going,pictures diagrams and dimensions. great help thanks to the ring members. Now to get a drum.
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