Help With Measurements

Discussion in 'Reverse Flow' started by goatlockersmoke, May 1, 2015.

  1. Hello All, 

    I am looking to build a couple reverse flow smokers and have been studying and trying to come up with my measurements for my smoker and need to see if they are correct.  I am running into some issues with the proper size of the RF Plate and the area at the end of it.  So here is what I have:

    3/8th inch thick steel pipe 43.25 inches long (might cut off the .25 to level out the pipe) with a inside diameter of 29.25 inches and radius of 14.625

    Volume of Cooker: 29.25 x 29.25 x 0.7854 x 43.25 =    29, 062.2175

    FB/CC Opening, Area Under RF Plate, Area at the End of RF Plate  are all the same at 29,062.2175 x 0.004 =    116.2488

    Minimum Volume of FB:  29,062.2175 x 0.33 = 9,590.526   I was thinking somewhere along the lines of 22 H x 22 W x 24 Long (accommodate ash draw)

    FB Air inlets: 29,062.2157 x 0.001 = 29.0622 

    Exhaust Stack Volume: 29,062.2157 x 0.017 = 494.0574

    Stack: 18 x .7854 x 6 x 6 = 508.9392   so stack will be 18 x 6

    So this is where i start running into problems...

    I plugged in my numbers as directed using the Radius (14.625) & Segment Height ED 2.25 inches to achieve get my 116.2488 cubic Volume inches required for my FB/CC opening volume. This also gives me an AB Cord of only 15.588, which as i understand it has to be the minimum width of my FB.

    So then i went into the calculator and tried to determine my FB/CC opening size using the Partial Round and a Segment Height ED (2.25 inches) and the AB Cord of 15.88 Inches it gives me a calculation of 24.3 sq inches, which i know is wrong.  In order to get close to the FB/CC Opening / Circle Calculator Sector Area openings of 116.2488 and 120.22 respectively I would need to be closer to a Segment Height ED of 7 and a length of 24 or 24.25 to get either 115.1 or 116.2 volume inches.

    From my readings and understanding there was no way to determine the RF Plate length...Cord AB should be the width but that would mean i could only go about 7.25 inches long and i know that cannot be right.  And, i do not know how to determine how much space is needed at the end of the RF Plate either so i am stuck.

    I ran into similar issues when working out the math for the 500 Gallon Tank i bought to make a smoker with too...the tank is 116 inches long and 36 inches in diameter.  By the time i got the AB Cord and Segment Height ED measurement it seemed to tell me the RF Plate had to be at 16.75 inches, which is almost half way up the tank, which is not good...i thought i might be able to get three cook racks on a 36 inch diameter tank.  So i think i am missing something.

    So any help would be really appreciated.  Thank you in advance.

    Best Regards, 
    Last edited: May 1, 2015
  2. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Using the circle calculator......

    14.6" radius..(OD)... 6.75" Segment Height...(ED).... Chord AB 24.6"..(RF width)... Segment Area 117 sq. in..(Green area in picture)..

    Volume of the Cook Chamber.... Use the Inside Diameter of the tank...

    Diameter X Diameter X 0.7854 X Length = Volume in cubic inches

    Volume in cubic inches X 0.004 = FB/CC opening in square inches

    Volume in cubic inches X 0.004 = Area under the RF plate in square inches

    [B] Volume in cubic inches X 0.004 = Area required at the end of the RF plate in square inches or longer[/B]

    Volume in cubic inches X 0.33 = minimum volume of the Fire Box

    The length of the RF plate is..... The area measurement at the end of the RF plate, to the FB....... (If the area at the end of the RF plate is the Segment Height ED or taller..)

    You may have noticed this [email protected] comes easy to me.... If I missed something, let me know and I'll crunch more stuff....

  3. Dave, 

    Thank you, i think my lazy eye got the best of me since i was looking at the sector area for my numbers rather than the segment area.  So if i have this correct now, the width of my RF plate would be 24.6 (might go with 24.5 for ease) and the length should be 36.6 inches (43.25 - 6.75 Segment Height ED).  Is that correct?  

    Now my other question is, what is the best way to determine the right inlet sizes on the FB?  I know the the Volume in Cubic Inches can be shared but should emphasis be placed more on one or the other or should they be even?  This is my first build so i am not the best fabricator so i am trying to keep the inlet hole design fairly simple.  I am also considering a insulated FB since i am in the Pacific North West where is is cold and raining a lot so i am sure that will cause some challenges for me as well....but all part of the adventure eh?

    Again, thank for for verifying my info...cant believe i over looked something simple like that.  Take care.
  4. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    It is just as easy to cut a piece of metal 24.6" as 24.5"...

    Approx. 20 / 80..... upper / lower.....

    Volume in cubic inches X 0.001 = FB air inlets in square inches...
    Last edited: May 1, 2015

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