120 Gallon Offset Build (PICS)

Discussion in 'Side Fire Box' started by smokealilsmoke, May 7, 2016.

  1. Hi Everyone,

    So I've embarked on building my first offset smoker. I've had a 30" MES for a few years but have decided to try my hand on an upgrade. I found a 120 gallon vertical propane tank (pictured) as well as a 24"x24"x3/8 piece of pipe (pictured) on CL. I've currently got the propane tank soaking with soap and water. I plan on building this as a true offset. I may put tuning plates in later but would like to try w/out at first.
    I've been putting #'s into Feldons. I've seen the one Mr. Omak has as well but not sure if required to use it being it is not a RF. If I should use it anyhow, let me know. I will post my #'s fron Feldons as well as what I came up with from the circle calculator. I'm sure there are holes in them that you guys will find. I'm not really a good math guy so any help is greatly appreciated. Thank you.
    Last edited: May 8, 2016
  2. Here is the link to my Feldon calc Dimensions. My dimensions are not spot on being the ends are rounded. Not sure if thats a huge issue or not.
    Link to BBQ Pit Calculator

  3. Not sure if I'm reading this right but is it saying that my football opening should be 5.3125/5 5/16" wide? I am prop way off but that is why I'm here so those much more versed in this can help steer me in the right direction. Be gentle!! Thanks again.
  4. Smoke Smoke ( i have crs can remember the rest of your screen name to get down)  For your cc you need a minimum of 110.88 SQ.inches of fb to cc opening, For ME i've found it easier to use the Chord ab and Segment height ed Prompt in the calculater till I get 1/2 of my SQ Inches needed, then Double the Height to get my footbal shape, It lets me decide how wide I want the football by putting in the width I would like the football, then play with the height till I get the Sq in I need, The Segment it gives me for 1/2 the square inches plus the same segment above it is a football of the total Sq IN needed.

  5. SmokinHawg thanks for the reply! What did I have messed up in my initial calculations in the Feldon calculation that gave me a fb to cc opening of 83.29 vice 110.88? I trust you, I just like to know where I messed up so I can right myself.
    I did the new circle calc like I thought u explained it. So it's telling me I need a football that is 10.3125 long by 6" high (segment height doubled). Would that be correct? Thank you again for the help!

  6. Ok that previous circle calc I did is incorrect I believe. I did it for the total area not 1/2 then double it for my football shape. 7 1/8 x 4" for my football shape. I think this one is online with what you were talking about SmokinHawg. Let me know if I'm on the right track. Thanks again!
  7. Smoke, Using Feldons Calculator you needed 74.4 square inches of fb to cc opening, which was a half moon 13.76 wide by 6.34 tall to = 74.4, Feldon's seems more set up for SQ> or Rect  Fireboxes, Using Daves calculator on this site you need a fb to cc opening of  110 square inches, feldon's uses the fb as it's base for calculations, and Daves used the cc to calculate the figures needed, it is at the top of the Reverse Flow build section,and is much more accutate.
  8. Smoke, A football, 18.75 by 9 is 113 sq inches.allowing for the thickness of your pipe. You can make a cardboard pattern off the end of your piece of pipe to help make the cut in your CC.

    Last edited: May 8, 2016
  9. SmokinHawg, your the man! Thanks again for the help and I'll post pics as I make progress!
  10. Well I've made a little progress. I got the firebox opening cut. Big thanks to SmokinHawg for the help with the measurements! I also got the firebox door cut out, strapped and hinged. Not gonna lie, I wasn't 100% sure it was gonna open as smoothly as it did once I got everything in place but it worked out great. Gonna move on to building the stand next. Thanks for looking!
  11. So when making the cut on my cook chamber I want to cut at 12 o'clock and 3 o'clock. I've seen on some threads that people do a +1" past 3 o'clock. I guess to make room for the bottom tray? Am I on the right track? Is that something I should do or just do the 12 and 3? Thanks
  12. Got the stand built.

    Thanks to smokin SmokinHawg for the idea if making a template of the inside of my smoker for deciding where to make my door cuts. I decided to go with three racks 5" apart.

    Got the door cut and strap on.

    Got the FB opening cutout on the CC and got the fire box in there.

    Got it welded up. I still need to brace the FB up on the stand but she's tacked in place.
  13. Lookin good Smoke, Nice matchup between the fbox and cc, Won't be long now till you're cookin!!


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