Short/Fat 120 Gallon Build

Discussion in 'Reverse Flow' started by woodyg, Nov 27, 2015.

  1. woodyg

    woodyg Smoke Blower

    Hello again!
    I finally found a tank that I was looking for. It's a 120 gallon vertical. 30" Dia.

    I've been doing a LOT of reading on similar (and some not) builds. Thinking and re-thinking ideas.

    I was hoping someone could double check my numbers and answer a few questions I have before I start cutting?

    On the right of that pic is my FB/CC opening. I went with 3/16 thick but that's only a guess at this point. I have yet to even drill a hole in it. If I'm thinking correctly, the inside of my FB would need to be 24.458" wide? If I made my firebox 24.458w x 20h x 20d, this would give me 9795.2 cu in.

    I have a piece of 6-5/16" ID x 39"L pipe. Is this too big? To get my volume correct it would leave me with a 19-1/2" height. I'd like to use it if I can, it's 304 ss. I thought it would look good all polished up!

    What is ideal distance between RF plate and bottom grate? With a short/fat tank like this it would give me about 8"ish

    One last thing for now, it gets pretty cold up here in MN. I'm planning on insulating the FB. 1/4" seems to be the norm but would I gain anything by going to 3/8"? 1" insul enough?

    Please bear with me. I already know this will not be a quick build with work/kids sports etc. Plus the more builds I read about, the more ideas I get!

    Thank you for any and all help guys! I will try to keep this project going so you don't get bored with it. Thank you!
  2. woodyg

    woodyg Smoke Blower

    After looking at my 1st post, it looks like some of my numbers might be hard to read on the pic.

    CC 27,720
    FB/CC 110.88
    Under RF 110.88
    End of RF 110.88
    FB 9147.6
    FB air inlets 27.72
    ESV 609.84

    FB/CC opening has a rad of 14.813
    24.458 width x 6.454 height

    Hope this helps. Thanks
  3. woodyg

    woodyg Smoke Blower

    Well it looks like my FB plans are going to change a bit. I picked up this welding table

    Some people would look at it and say "hey a free welding table" I thought "hey a free firebox! And legs too!"

    So it looks like my FB will be 1/2". A little overkill but the price was right...
  4. pork2go

    pork2go Fire Starter

    Looking good woodyg, you can't beat free. I am working on a tank just like yours. I look forward to your progress. Not too many 100gal builds on the Internet
  5. woodyg

    woodyg Smoke Blower

    Well I was able to sneak out the last couple of nights and get some work done. First I marked where I wanted my cuts to be.

    I wasn't sure how the plasma cutter would do. I've never cut 1/2" with it.

    I turned it up all the way and cranked up the air pressure. Looks like 1/2" is about the max I'd want to do with it. VERY slow going but worked well. Clamped on a straight edge and ready to cut.

    A friend at work asked how they worked compared to a torch? I showed him this.

  6. woodyg

    woodyg Smoke Blower

    My usual 9yr old helper hasn't been feeling well the last few days so I didn't get much help. Hard to get action shots by yourself but I did get one with the cuts done

  7. pork2go

    pork2go Fire Starter

    Looks like your making great progress woody, I wish I was that far along, I'm having plasma cutter issues. Keep the photos coming
  8. woodyg

    woodyg Smoke Blower

    I got a little bit done on the FB this weekend. I thought it would be easier to make a square box if I squared up my plates. So I threw them on the Bridgeport and milled the edges square

    That's as far as I got but I did end up with a nice square box

  9. woodyg

    woodyg Smoke Blower

    I do have a question I was hoping someone could answer.

    My FB/CC opening is 110.88 w/ a width of 24.458 height of 6.454 and a radius of 14.813
    Somewhere I read under my RF plate should be 1.5 times the area of the opening. That gives me an area of 166.32 and a width of 26.9 and height of 8.606

    My question is should the top of my FB be cut in the 6.454 height and reverse plate put in at the 8.606 height with a gap of roughly 2-1/8"? Or should I mount the FB at 8.606 and come straight off there w/ the RF plate? I'm leaning towards the 2-1/8" air gap to eliminate the hot spot on top of the FB

    I know it's a lot of numbers to throw out there but I was hoping someone could help me? Thank you!
  10. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

  11. woodyg

    woodyg Smoke Blower

    Good morning Dave. I was hoping you would comment. I am sure there are many more along with myself that appreciate the time that was spent putting that together. Thank you! I can't tell you how many times I've read it and re-read it.

    Maybe I am overthinking this or reading too many old posts? So the under the RF plate area should be the same as the FB/CC opening all the way across? Not 1.5 times the FB/CC opening? Not sure where I read that maybe I can go back and find it.

    If this is the case, would you lower your lowest grate below center to 5-6" above RF plate? I guess it was stuck in my head that the lowest grate would be on center. This would put it at about 8.1". Is this too far?
  12. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Morning.... Originally, the "1.5 times" came from the Feldon's Calculator when building a reverse flow smoker... Using that multiple, the "overheated" FB disappeared..... Adding the upper air inlets, to the FB, also helped and improved temperatures across the cooking surface, by moving heat/smoke through the smoker...

    Put in guides for the cooking grates so they are adjustable... I'd start at 4-6 inches above the RF plate... allow room for a pork butt and add another... you may like having 2 or more food grates...

    FB/CC opening, under the RF plate and at the end of the RF plate are the same... Provides good air/smoke/heat flow with little friction loss...
    Last edited: Dec 7, 2015
    ballsonagoose likes this.
  13. woodyg

    woodyg Smoke Blower

    Thanks for the clarification Dave. That was my original plan but I started 2nd guessing myself. Too much late night reading old posts? Over analyzing? Not sure. Thank you!
  14. woodyg

    woodyg Smoke Blower

    Well I thought I'd get a lot more done this weekend than I did. Once I ground a bevel on the edges and welded it all together it took up a better chunk of my weekend

    Rough estimate with welding both sides inside and out there's about 28 ft of welding. The hands and wrists aren't what they used to be!

    I thought I had a before pic with just the bevels before welding but I only have an after

  15. is2326

    is2326 Fire Starter

    Interested to see how yours turns out. I built mine with the same tank.
  16. woodyg

    woodyg Smoke Blower

    I took the night off from building last night to mix up some apple pie

    I did order up some steel this week to finish my FB. I got a bar of 1/2 x 3 for my "face frame". Sawed it to length and milled the ends to square everything up then tacked it together

    My plan is to have a 1" lip around the whole outside of the FB. This will give me space for the insulation.

    Because of the 1/2" thick FB and the 1" space on the outside I have a 1-1/2" lip on the inside. That will give me enough space for a decent seal on the door. The bottom one I did take down to 1-1/2" wide so it would be flush to the bottom of the FB. Thought it would be easier for ash removal

    Here is my door just sitting there for a visual. I'm rethinking my lower air inlets to rectangle. This way I don't need as much space between them. I don't want my slide to go beyond the side of the FB door when fully open

    The double line running across is my grate sitting 4" above FB floor. This should give me enough space for ash and not impede airflow. Is this enough?

    I see its best to put the uppers directly across from FB/CC opening. Heightwise do you center this to the opening/ top of opening/ or lowest part of opening?

    I assume the lower air intakes are best to be directly across FB/CC opening also? I've seen some builds with intakes on the sides of the FB. One on each side. Is this a better design?

    Anybody have any opinions on this? Thanks guys!
  17. pork2go

    pork2go Fire Starter

    Hey woody that firebox looks awsome!! I was reading a post that ribwizzard made about the upper opening not being directly Accross from the fb/cc opening but to have it a little lower. Of course I found that post after I had already cut my vents and my top vent is inline with my cc/FB opening. You might want to shoot him a pm to conferm. I think I'm just going to roll with mine sence it is already done
  18. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    WoodyG, morning.... If you get the upper air inlet too low, across from the fire grate as an example, both the upper air inlets and lower, will feed the fire air.... NOT GOOD..... you want the upper air inlets across from the FB/CC opening to remove heat from the FB and have them able to cool down/move air through the CC.... that will allow for even heating across the cooking surface...

    Your upper air inlets are positioned perfectly for controlling the heat in your smoker....

    You want the space between the air inlet to be a bit wider than the holes themselves... That will allow for complete closure of the air inlet....
    Last edited: Dec 20, 2015
  19. woodyg

    woodyg Smoke Blower

    Thanks for the input guys. I really appreciate it!
    Dave- this is why I was thinking of switching to rectangular lower intakes. Taller more than wider. I won't need as much space between them to be fully open or closed. Seems like more wasted space in a circle

    Here's a pic of the face frame welded on

    Sorry about the glare but this thing is a bear to move around! Anybody thinking about a 1/2" FB just realize it will be HEAVY. Thanks for looking and the input guys!
  20. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    I think..... that will NOT warp..... Thumbs Up

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