That tank is 250 gallons.... 30 x 30 x 0.7854 x 82" (length adjusted for round ends) / 231 (cubic inches in one gallon) = ~ 250 gallons... Dave
Well, I bit the bullet and ordered the 1/4 plate for my builds. Notice I said "builds", as in 2. i picked up another 250 tank just like the 1st one. Using Dave's numbers above (except I used 29.50 x 29.50 x 82") here are my calculations. My plate should be here early this week but before I start cutting I want some of you guy's to check my numbers. If you have any questions about how I got them or any corrections PLEASE let me know. I'll be cutting for 2, so if I make a mistake it will be double.
Here they are,
Calculations for a standard design, reverse flow smoker..
Gallons X 231 = volume in cubic inches.... Sometimes the tag, in gallons, reflects a 20% air space for expansion....
Volume of the Cook Chamber.... Use the Inside Diameter of the tank... 29.50
Diameter X Diameter X 0.7854 X Length = Volume in cubic inches 56046.54
Volume in cubic inches X 0.004 = FB/CC opening in square inches 224.19
Volume in cubic inches X 0.004 = Area under the RF plate in square inches 224.19
Volume in cubic inches X 0.004 = Area required at the end of the RF plate in square inches 224.19
Volume in cubic inches X 0.33 = minimum volume of the Fire Box 18495.36 Plan for FB to be
27L X 30W X 27T. That should leave room under the grate for ash and coals.
The above areas are necessary for great air/heat/smoke flow.... using less may cause an overheated FB.... Narrow / Long CC may require an increase in those numbers due to increased surface area friction to volume... Wide/Fat Short CC may use smaller numbers due to reduced surface area friction to volume...
Volume in cubic inches X 0.001 = FB air inlets in square inches... 56.05 4-5@ 2X3 ea.side,
2@ 2X3 in door
Recommended upper and lower air inlets... Upper air inlet directly across from the FB/CC opening to facilitate moving heat from the FB to the CC, and insuring good air flow through the CC.. The lower air inlet should be situated at or below the fuel grate.... The two air inlets can share the designated square inches of opening....
Volume in cubic inches X 0.017 = Exhaust Stack Volume in cubic inches, above the CC.... (ESV) 952.79
Exhaust Calculation..
ESV in cubic inches_____________________________ ... = Stack Length in inches (36" +/-) 6"ID = 33.70
0.7854 X Stack Diameter X Stack Diameter
Adjust the diameter of the stack, until the proper length is achieved... be sure to measure the actual internal diameter of the pipe used..
this is for round stacks only..
This circle calculator is really cool... It does it all.... Just fill in the necessary blanks...
......click on this link......
http://www.1728.org/circsect.htm
For calculating the FB/CC opening.... You are calculating for the GREEN area... that will be the cut-out area in the FB that mates to the CC....
The green area is a segment. It is called a "Segment Area"... That area is the same as the FB/CC opening....
When you open the "Circle Calculator" link, Click on the "bullet" to the left of Radius & Segment Height ED....
Circle Calculator
Click on the 2 variables you know
......Radius and Central Angle...........................Radius & Chord AB
[X] Radius & Segment Height ED.....................Radius & Apothem OE
......................................................Radius & Arc AB
......Chord AB & Segment Height ED................Chord AB & Apothem OE
......Segment Height ED & Apothem OE...........Chord AB & Arc AB
You should have opened the circle calculator and a bunch of boxes will appear below..
and a box called [CALCULATE]..
Enter the radius in the box so marked.... If you tank is 24" OD, and has a 3/8" thick steel wall, the ID of the tank 23.25".... the radius is 11.625"..... these numbers need to be accurate if you want stuff to fit... ALSO, take into account the thickness of the FB steel when cutting out the tank... 14.75 R
Enter a guess for the Segment Height ED... I'd start with 6.0 10.72
Click on [CALCULATE]....
The other boxes will fill with numbers....
The [Segment Area] box is what you area going to compare with the FB/CC opening in square inches...
If the FB/CC opening number is smaller, change the number in the Segment Height ED box to 5.... continue changing that number until the [Segment Area] matches the FB/CC number.....224.36
Now look at the colored circles above.... Segment height ED is how tall the green area is and corresponds to the area to be cut out.....10.72
Also, [Chord AB] corresponds to the width of the RF plate...
NOTE... for ease in fitment, the FB should be at least as wide as the RF plate..28.38