FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 


Pit building ratio calculator
Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9  Next
 
Post new topic   Reply to topic    The Smoke Ring Forum Index -> Cookers Stickys
View previous topic :: View next topic  
Author Message
Tom C
BBQ Super Pro


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

PostPosted: Wed Sep 09 09 12:58 pm    Post subject: Reply with quote

Hi darylcincy,
Thanks! I'm glad to hear that the calculator is working out for you.

Here is what I would do to figure the length you need:

In the calculator, once you enter the size of your firebox look to the left of the blue cells underneath in the chimney section where it says "Exhaust chimney volume needed". You should see a volume in cubic inches.

Example: In the calculator for a circular firebox I put a firebox size of 24"x24". The calculator shows that the chimney volume needs to be 542.59 cubic inches. If you take the size pipe you mentioned 4"x5" and multiply the two, you get 4"x5"=20 sq. in. If you divide the total volume needed of 542.95 cubic inches by the 20 sq.in. You get the following:

542.59"/20"=27.15"

So the length of 4"x5" pipe you would need is 27.15 inches.

That's the long answer!

The short answer is to round off the size of your pipe. So that your 4"x5" pipe is rounded to 4.5". In the tests that I did the calculator give me a longer length than actually need which is better than being too short! In the above example, you would end up with about 7" more than you need or 34.13". I actually did this on my own smoker with a 4"x6" pipe rounded to 5". I guess it comes down to how accurate you want to be.

Tom
_________________
Homemade offset smoker 24"x48"
Charbroil CB900 grill
Back to top
View user's profile Send private message
paulhayes



Joined: 15 Aug 2009
Posts: 17

PostPosted: Mon Sep 14 09 1:02 pm    Post subject: Reply with quote

Tom C.

Just to let you know my cooker went to the furnance last week and they had some mechanical trouble and were set back until tomorrow on getting it heated treated I should have it bsck Tueday night and will begin getting everything marked off anf ready for the plasma work, I will be going to Built Wright Trailers tomorrow and giving im my measurements for the trailer so that he can get that ready to go. Hopefully I will be smokin' by mid-October or before and some pictures will be up for viewing


Thanks Paul Hayes
Back to top
View user's profile Send private message
Tom C
BBQ Super Pro


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

PostPosted: Tue Sep 15 09 1:59 am    Post subject: Reply with quote

That's great Paul! That will be a nice cooking rig for you. Good luck.
_________________
Homemade offset smoker 24"x48"
Charbroil CB900 grill
Back to top
View user's profile Send private message
paulhayes



Joined: 15 Aug 2009
Posts: 17

PostPosted: Mon Oct 05 09 2:39 pm    Post subject: Reply with quote

Tom,

Boy it seems like forever since I have been able to get on here! Well I have my firebox ready and we will be adding it to the main cooker this week hopefully. We had some set backs with things going on and not being able to work on it. I have a question or two I have decided on a reverse flow design I was wanting to use pans for the plate that runs from the firebox to the opposite end that way they can be removed and cleaned and they will also serve and dripping pans, Does the flue need to be semicircle or can it be a flat sheet like the bottom of the pans that I am wanting to use? also howfar from theend should I stop the pans so that the heat and smoke can return to the stack? By the way the pans will be 3/16" thick with 2" sides all the way around them so that liquids and drippings will not overflow there will be 3 of them so that they will be easy to remove and handle. I would like to look inside of a Lang cooker but no one has pictures of the inside without the racks. Also how far below the cooking racks should the plate or pans be? Thanks alot for any information you can give!
Back to top
View user's profile Send private message
Tom C
BBQ Super Pro


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

PostPosted: Mon Oct 05 09 3:01 pm    Post subject: Reply with quote

Hi Paul,

I'm not sure I'm following you on the flue question. I think you are asking about the opening between the firebox and the cooking section. If I'm correct, it can be any shape I guess as long as it is large enough for draft.

I don't have any experience with reverse flow but I'm sure someone here can tell you how much room to leave at the end you need for air and smoke head back to the smoke stack. As for how far below the cooking rack should the plates be, Mine are six inches. I think that is about average.

Good luck attaching the firebox! Post pictures if you can.
_________________
Homemade offset smoker 24"x48"
Charbroil CB900 grill
Back to top
View user's profile Send private message
k.a.m.
BBQ Mega Star


Joined: 12 Dec 2007
Posts: 25938
Location: Southeast Texas.

PostPosted: Mon Oct 05 09 7:15 pm    Post subject: Reply with quote

Paul, I am like Tom a little confused on your flue question but as Tom said as long as enough draft can come through and your pans seal up against it then you should be good to go. Most reverse flow designs have at least a 6'' gap at the end where the heat/smoke turn back and 6'' below your grates.
_________________
Always remember slow and steady wins the race.

Hybrid Cooker
Back to top
View user's profile Send private message
paulhayes



Joined: 15 Aug 2009
Posts: 17

PostPosted: Mon Oct 05 09 11:45 pm    Post subject: Reply with quote

Thanks very much, I was actually wanting to know if the flue or plate that keeps the heat down until it reverses and heads back, would that be ok being the bottom of the pans which is flat some I have seen look as if they took a round pipe and cut it in half and welded in the bottom to transfer the heat to the other end, but I did not see any drip pans in this particular cooker. Being that the bottom of the cooker is round and the heat transfer tube is half round when placed in the bottom of the cooker it made a round transition tube for the heat. Once again the info that you guys have given me is very useful thanks
Back to top
View user's profile Send private message
bbqbear3



Joined: 07 Jan 2010
Posts: 3

PostPosted: Thu Jan 07 10 4:59 am    Post subject: Re: Pit building ratio calculator Reply with quote

Posted: Wed Jan 06 6 50 Post subject: Re: BBBBBBBBBAAAAAARRRRRRBBBBBBBBBQQQQQQQ!!! from Oklahoma

--------------------------------------------------------------------------------

I'm a new member, but looking forward to advise on smoking, and sharing war stories. I've been smoking for six years, and am building a larger smoker. I have a 500 gallon propane tank I want to convert to smoker. Wondering how large my fire box should be. The propane tank is 36" Diameter by 8' long.
Back to top
View user's profile Send private message
Tom C
BBQ Super Pro


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

PostPosted: Thu Jan 07 10 8:55 am    Post subject: Reply with quote

Hello bbqbear3 and welcome to the Ring!

The rule of thumb for a firebox size is 1/3 the volume of the cooking chamber. Based on the tank size of 500 gal., the volume of your tank is 115500 cubic inches. 1/3 of that would be 38500 cubic inches. If you went with a round firebox with a pipe that is 36" in dia., you will need it to be about 38" long. If you want to use a square or rectangular firebox, you can use any dimensions you want as long as when you multiply the three dimensions they equal at least 38500 cubic inches.
One example would be 33H x 36W x 32.45L = 38550.6cubic inches.

Good luck on your build!
_________________
Homemade offset smoker 24"x48"
Charbroil CB900 grill
Back to top
View user's profile Send private message
paulhayes



Joined: 15 Aug 2009
Posts: 17

PostPosted: Fri Jan 08 10 4:31 pm    Post subject: Re: Pit building ratio calculator Reply with quote

bbqbear3 wrote:
Posted: Wed Jan 06 6 50 Post subject: Re: BBBBBBBBBAAAAAARRRRRRBBBBBBBBBQQQQQQQ!!! from Oklahoma

--------------------------------------------------------------------------------

I'm a new member, but looking forward to advise on smoking, and sharing war stories. I've been smoking for six years, and am building a larger smoker. I have a 500 gallon propane tank I want to convert to smoker. Wondering how large my fire box should be. The propane tank is 36" Diameter by 8' long.



Hey,

Great to have you I am currently in the middle of my 250 gal. smoker build A.K.A. "Hog Heaven" and it has been fun so far I have the trailer completed and some of the cooker it self, but ran into "not enough time" situations and could not finish before the cold weather set in here in Arkansas but Tom C. will lead you in the proper direction he and a couple others were a great help when I started putting my plans on paper.
Back to top
View user's profile Send private message
jefnmichele
Newbie


Joined: 26 Jan 2010
Posts: 41

PostPosted: Tue Jan 26 10 10:28 am    Post subject: The Excel File Reply with quote

Can I get this excel file? I am building a rather large smoke and this would be an incredible help.

Thanks

Jefnmichele@verizon.net

Got them, guess I didnt look hard enough
Back to top
View user's profile Send private message
day_trippr
BBQ Super Pro


Joined: 08 May 2009
Posts: 3206
Location: Stow, MA

PostPosted: Wed Jan 27 10 12:04 am    Post subject: Reply with quote

Just a suggestion, but the round and square firebox spreadsheets could easily be combined into one file by using the "sheet" feature in Excel...

Cheers
_________________
Save the planet: it's the only one with beer!
FrankennBrinkmann ECB
Char-Broil Commercial Gasser
Back to top
View user's profile Send private message
ryan cassidy
BBQ Fan


Joined: 26 Jan 2010
Posts: 150

PostPosted: Tue Feb 16 10 12:37 am    Post subject: Reply with quote

Quick question on the FireBox Air Opening Calc. I am using the 7.25" circular vents. These : http://www.kck.com/bbq_air_damper_smoker_pit_grill.html

What number do I put in there?

I believe I get the end result (sq inches) by taking PI X Radius squared. So in this case 3.14 X 2.5 Squared. Then divide it by two, since that vent only ever allows you to use 50% of the total area. The number I get here is the number that should be in F28 right?

Sorry for the confusion, Just trying to figure it out. I believe if I work to the number in F28 then I'm good (that what I did, just want to check).

Ohh one other question. Any issue with having too much chimney length? I should have roughly 28 inches. however, I have two 20" stacks for a total of 40 inches? Thoughts?

Cheers,
Ryan
Back to top
View user's profile Send private message
ryan cassidy
BBQ Fan


Joined: 26 Jan 2010
Posts: 150

PostPosted: Tue Feb 16 10 1:40 am    Post subject: Reply with quote

Actually... I think I figured it out. If you enter in the diameter you get the correct sq inches. So what I would do is measure the width (center to outside edge) of the opening then just do a Pi x R2 formula and then divide by two.

My numbers come out now, it makes sense.

Cheers,
Ryan
Back to top
View user's profile Send private message
Tom C
BBQ Super Pro


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

PostPosted: Mon Mar 08 10 12:37 pm    Post subject: Reply with quote

day_trippr wrote:
Just a suggestion, but the round and square firebox spreadsheets could easily be combined into one file by using the "sheet" feature in Excel...

Cheers


That's a good point! If I get a chance I will do that. Very Happy
_________________
Homemade offset smoker 24"x48"
Charbroil CB900 grill
Back to top
View user's profile Send private message
dodis
Newbie


Joined: 09 Mar 2010
Posts: 30

PostPosted: Wed Mar 10 10 11:58 am    Post subject: RE-revised Reply with quote

Tom C,

I'm sure you've seen the email by now of my latest "revision" to the old single page spreadsheet. I should be out in the shop building my smoker, but work seems to always get in the way.

Looking forward to your review, and hopefully seeing a link to the posting...

Mike "Dodis"


P.S. Heck of a first post... I should go hit the intro page...
Back to top
View user's profile Send private message
Tom C
BBQ Super Pro


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

PostPosted: Wed Mar 10 10 2:39 pm    Post subject: Reply with quote

Mike,

I just sent a pm with comments. You have a great working knowledge of Excel that shows in your revision!

Oh and welcome to the Ring!
_________________
Homemade offset smoker 24"x48"
Charbroil CB900 grill
Back to top
View user's profile Send private message
Wreckless
BBQ Super Pro


Joined: 15 May 2009
Posts: 2292
Location: New Braunfels, TX

PostPosted: Thu Mar 11 10 7:55 pm    Post subject: Re: RE-revised Reply with quote

dodis wrote:
Tom C,

I'm sure you've seen the email by now of my latest "revision" to the old single page spreadsheet. I should be out in the shop building my smoker, but work seems to always get in the way.

Looking forward to your review, and hopefully seeing a link to the posting...

Mike "Dodis"


P.S. Heck of a first post... I should go hit the intro page...

What a concept. Bringing something to the the table on your first post. Besides the skill in spreadsheet formulas, you scored one in the " How to make friends and influence people" Dept. as well. Nice Idea The spreadsheet worked fine for my trial run. Welcome to the Ring! Smile
_________________
Backyarder
Smoker Grill
Trailer Rig
Back to top
View user's profile Send private message
Arquero



Joined: 19 Feb 2006
Posts: 8

PostPosted: Thu Mar 25 10 6:56 am    Post subject: Reply with quote

Tom C wrote:

Example: In the calculator for a circular firebox I put a firebox size of 24"x24". The calculator shows that the chimney volume needs to be 542.59 cubic inches. If you take the size pipe you mentioned 4"x5" and multiply the two, you get 4"x5"=20 sq. in. If you divide the total volume needed of 542.95 cubic inches by the 20 sq.in. You get the following:

542.59"/20"=27.15"

So the length of 4"x5" pipe you would need is 27.15 inches.
Tom


First off, thanks for all of the help. I makes things much smoother for the rest of us when someone that has been through the process is willing to help out.
Now, I have a 24" (diameter) x 36" (length) grill and I'm adding a firebox to it. The box is a 24" X 24" square and if I entered everything correctly, it needs a chimney volume of 619.20 cubic inches. I'm adding on to the existing 4" x 4" exhaust so if I followed you example correctly, I need a 38.7" length of square tubing for the exhaust. The only problem I'm having is that everyone that comes by keeps telling me the stack it too tall. Would you please verify my numbers so I can just kick these people out of my backyard once and for all? Very Happy
Back to top
View user's profile Send private message
Tom C
BBQ Super Pro


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

PostPosted: Thu Mar 25 10 11:41 am    Post subject: Reply with quote

Hello Arquero,

Okay letís see if I have this right.
First, you have a cooking section that is 24" Dia. x 36" long. That comes out to 16,277.8 cubic inches for the cooking section. You need your firebox to be at least 1/3 of that or at least 5426 cubic inches.

Your firebox at 24" x 24" x 24" = 13,824 cubic inches. That is almost 3 times the volume you would need. If you have not built the firebox yet, I would consider that. You could save some $$ there.

If you already have the firebox listed above, then I calculate that the smoke stack needs to be 691.2 cubic inches. Using the pipe size you give, I get the following:

4"x4"=16 sq.in.
691.2"/16= 43.2" length
If you went with two stacks y9ou can cut that length in half.

Since that is different than what you came up with, you may need to refigure things. The openings for air intake to the firebox as well as the opening between the firebox to cooking section could be off as well.

I show you need the following:

Air intake opening: 41.47 sq. in. (example 4.75" x 8.75" = 41.56)

Firebox to cooker opening: 110.59 sq. in. (example 8.5" x 13" = 110.5)

I hope this helps. Again, if you haven't built the firebox yet, consider going smaller. It will save material for the box and the stack.

Good luck on the build

Tom!
_________________
Homemade offset smoker 24"x48"
Charbroil CB900 grill
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    The Smoke Ring Forum Index -> Cookers Stickys All times are GMT + 8 Hours
Goto page Previous  1, 2, 3, 4, 5, 6, 7, 8, 9  Next
Page 5 of 9

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2002 phpBB Group