Feldon numbers for 60 gallon RF

Discussion in 'Reverse Flow' started by socalcooker, May 8, 2016.

  1. socalcooker

    socalcooker Meat Mopper

    Link to BBQ Pit Calculator

    Please check my numbers. It's a 60 gallon propane tank. I can get actual measurements tomorrow morning. This will be a reverse flow. Thank you in advance.

  2. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

  3. socalcooker

    socalcooker Meat Mopper

    So I've got 13860 for cc x .044 = 55.44 for the cc to fb opening and under RF plate and at the end of RF plate. Minimum fb size would be 4573.8 the size I plan on using for fb is 5832. Is that to big 18x18 seems like a reasonable size and I won't need small splits of wood. I'll be using primarily oak and what I have now it in the 16-18 inch range, so I'd like to stick with that size fb. Thanks for the help Dave.
  4. socalcooker

    socalcooker Meat Mopper

    Another question I have enough 3/8 plate to do the firebox. Is that overkill? It seems like it to me but it's free, that's why I'd like to use it. I have a piece of 1/4 I planned on using for the RF plate.

  5. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Oversized FB is fine....   3/8 plate is really good for the FB build....   
  6. aussiq

    aussiq Smoke Blower

    Hmmmm i used 5/8 for my firebox so i wouldnt worry about overkill.. just how your going to lift it. Theres no such thing as overkill when its free. I dont no what your back ground is but think about how your going to weld it. If you put your plates corner to corner then you will have to do a large weld to fill the corner out. I choose to do a 1/4 inch weld prep bevel on my fb.
  7. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    If you read the tutorial I posted in post #2, it will explain the pitfalls in Feldon's calculator....
  8. socalcooker

    socalcooker Meat Mopper

    I've been thinking about the weld joint. I don't normally weld stuff that thick, and I really dislike doing multi pass welds. Not sure whether I'm gonna use MIG or stick yet either. I might not do corner to corner and bevel them so I can do a single pass. I don't think I need 100% pentetration it's not going to be under any stress.

  9. aussiq

    aussiq Smoke Blower

    You could also overlap your joints. By say sitting the top and bottom plate in a little bit. And you should be able to do a single pass just pick up the bottom edge of the plate and wash the weld up to the top edge. You should have very minimal undercut doing it this way if any you can just dress with the grinder and this will still give you the rounded edge look on your fb. Or otherwise like we mention do the bevel. You can leave the weld or if its a bit messy grind it flush then once painted it will look seamless. If you can replicate the joint out of scrap then you can weld it both ways and see which look you perfer. If you check out my build i went with the bevel because it was less welding and i wanted square edges
  10. socalcooker

    socalcooker Meat Mopper

    That's what I was thinking. Overlapping them but flush and bevel the joint. I should probably cut the pieces first lol.
  11. socalcooker

    socalcooker Meat Mopper

    Ok so I think I've got all my numbers right. CC and FB sizes were mentioned above. For my FB to CC opening I need 55.14, I decided to go with a trapezoid opening because I can't figure out the circle calculator. So the opening size I got from an online calculator is 4.375 height,17.732 top length, 8.718 bottom length, plus a 1 inch dam. I plan on using two 3x3 inlets on the FB and a smaller upper inlet that I haven't decided the size yet. My understanding is that the opening at the end of the RF plate is the same 55.14 I'm using for the FB to CC. Correct? I haven't decided what I'm using for the chimney yet, I have tubing in 4, 5, and 6 inch so I'll see what looks best with my CC. Does the plenum need to be any specific size or just what looks reasonable. Sorry for the long winded post, I just want to make sure I've got everything correct before I start cutting.

    Thanks, Kyle
  12. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    What is the diameter and length of your CC....   Inches please....

    Cook Chamber Volume...

    Volume in cubic inches X 0.022 0.017 = Exhaust Stack Volume in cubic inches, above the CC.... (ESV) .. (The increase in volume ~30% shows a dramatic improvement in equalized temperatures across the cooking surface... edit 6/19/15 )

    Exhaust Calculation..

    ESV in cubic inches_____________________________ ... = Stack Length in inches (36" +/-)
    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..

    O U T P U T *** O U T P U T *** O U T P U T *** O U T P U T *** O U T P U T ***

  13. socalcooker

    socalcooker Meat Mopper

    20 diameter and 48 long including domed ends.

  14. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    20x20x.7854x48=15,000 cu. in.

    15,000 cu. in.      x 0.004 = 60 sq. in.

                                x 0.33 = 5,000 cu. in.  FB

                                x  0.001 = 15 sq. in. FB air inlets...

    15,000 x 0.022 = 330 cu. in. exhaust stack

    330 / .7854 x 4 x 4 = (26" stack) make it approx. 35" tall above the CC...

    Using the circle calculator, the green area is the cut out for the FB/CC opening....

    Chord AB is the width of the RF plate...

    Segment Height ED is how tall the green area is..  5"...

    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...

    Enter a guess for the Segment Height ED... I'd start with 6.0

    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.....
    Last edited: Jun 13, 2016
  15. socalcooker

    socalcooker Meat Mopper

    So if I'm understanding this correctly I need to change my air inlets a little. And my FB to CC opening should be 17.321 wide and 5 inches tall? But my FB is still good. Thanks for the help Dave I'm terrible with anything to do with math always have been.

  16. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Everything you have should be fine...   You can adjust them if you want....     The FB / CC opening is the green area...   The RF plate width is AB.....   ED is 5"....   

  17. socalcooker

    socalcooker Meat Mopper

    Awesome thank Dave.

  18. aussiq

    aussiq Smoke Blower

    Iam keen to see this bad boy. Cant wait
  19. socalcooker

    socalcooker Meat Mopper

    I'm anxious for it too, if people would stop having me build stuff. I do fabrication like a side job and I've been swamped lately. No time to work on my stuff.


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