firebox

[RodgeA]

Hi I'm getting ready to start my first smoker build and don't know what size I need to cut my firebox to cook chamber opening the propane tank I will be using is 42 inches long with a 14 inch diameter and I want my firebox to be 15 by 15 square any info I can get will be a big help.

[Clover Ridge Smokers]

You need to run your build through the pic calculator. It will give you the throat opening you need.

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

[Rodcrafter]

[RodgeA]

It says I need an opening of 27.00 square inches but what size would I need to cut the tank to get that size?

[Rodcrafter]

http://www.handymath.com/cgi-bin/arc18.cgi?submit=Entry

This should help

[Puff]

I hate to say this...how the heck do you work the numbers into that circle calculator thing? I was looking for the size of the throat for the 80 gallon tank I have.. I know the area of the throat I need but not how to figure out the 1/2 circle dimensions.

Since I could not figure out the circle calc, I built the gravity feed instead! Problem is, that one will be finished shortly

[Pete Mazz]

Since you know the radius of the tank and the area of the opening, set both of those to sq.inches along with the width and height. Input the radius and area and click calculate. The height will be the measurement from the bottom of the tank and the width will be the horizontal length across that height.

[Clover Ridge Smokers]

I like this online calculator even better. Scroll down the page and you and enter your radius and segment height and it will do the calculation for you.
http://www.mathopenref.com/segmentareaht.html

[RodgeA]

Hi guys thanks for the help I have my tank marked out and ready to cut but before I do it would be great if someone could check my calculations for me I have 3 1/4 height and 11 13/16 width for my half moon opening seems small to me here is a pic of the tank.

[Puff]

DO NOT go by me but it seems small to me also. If I plug these numbers into a " circle calculator ". I get everything but 27

[Clover Ridge Smokers]

The half moon throat opening is on the FB, not the tank. The opening on the tank needs to be just large enough so the throat opening is inside the tank. Hope that helps

[Clover Ridge Smokers]

To be honest an easier way to do it is to make your FB throat opening either a trapezoid or rectangle. Then cut the opening in your take to accommodate. Here is a link to a trapezoid calculator. http://www.mathopenref.com/trapezoidarea.html

[Clover Ridge Smokers]

Have you considered purchasing a set of plans for your build? It takes all the guess work out of your build and trying to calculate everything yourself.

[RodgeA]

I used http://www.feldoncentral.com/bbqcalculator.html to get my figures from keeps telling me 27 square inch hole.

[Puff]

Is there any reason you want 15x15 FB? Or would another size work? When I run those numbers it's telling me your FB is way too big. It should be more like 15x10 or any number combo to make its cubic volume lower

[Puff]

THIS SEEMS TO WORK :
It gives you 2 intakes on FB, one for each side, a stack almost tall enough to keep smoke out of your eyes and a more efficient FB size....let someone else confirm this however

Diameter Length Volume (in³)
Cook Chamber Size 14 in. 42 in. 6,465.40 in³

Length Width Height Actual Volume (in³) Recomended Volume (in³) % Recomended Size
Firebox Size 15 in. 10 in. 15 in. 2,250.00 in³ 2,155.13 in³ 104.40%

Chimney Diameter Rec. Chimney Volume Rec. Chimney Length
Chimney Size 2.5 in. 112.5 in³ 22.9299363057 in.

Length Width Intake Area (in²) Count
Air Intake 5 in. 1.75 in. 6.75 in² 0.77

Throat Area (in²)
Throat Size 18 in.

[RodgeA]

The reason I wanted to make the fire box bigger is so I could put longer sticks of wood in it and woulden't have to cut them and people keep saying make the fire box bigger than it needs to be make room for the fire grate and so forth a bigger fire box shouldn't matter as you will be controlling the temp with the damper I should think.

[Pete Mazz]

Numbers look right, other than the FB size seems too large, according to the Pit Calc.

[The Czar]

Because of the small size of this pit....15 x 15 FB won't be too bad....with larger pits and more air it would in fact be harder to control ....smaller pits are usually easier to control....

[Puff]

So, you roll the dice looking for a seven, you wind up with an eight....Close enough? Numerically you are nearly 45% oversized. In many arenas, that's a big number to overshoot. THIS IS ONLY MY 2 CENTS..for what it's' worth. If it works, great

[Clover Ridge Smokers]

I have to agree with others. A FB at 145% is too big even for this size smoker. I personally wouldn't feel comfortable with anything over 120% on this size smoker

[RodgeA]

ok I've changed my firebox size to 15x12x12 im going to try and use 1/4 plate for the steel thickness if it doesn't cost too much.

[Puff]

Your risk of warping will drop by using the 1/4". My FB is 24x26x30 and the top would bow out from the heat. A strategically place support inside eliminated that....( thanks Frank)

[Hambone]

I hate to say this...how the heck do you work the numbers into that circle calculator thing? I was looking for the size of the throat for the 80 gallon tank I have.. I know the area of the throat I need but not how to figure out the 1/2 circle dimensions.

Since I could not figure out the circle calc, I built the gravity feed instead! Problem is, that one will be finished shortly

What you want to calculate is the area of a circle SEGMENT. Do a google search and you should be able to find an online calculator. You simple plug in the numbers for your radius and area that you need and you can get the length of the segment which is the hight of the throat.

Hope this helps.

Mike