275 gallon RF Flame Smoker Completed

Discussion in 'Reverse Flow' started by cisweld, Jun 20, 2014.

  1. cisweld

    cisweld Fire Starter

    Howdy all,

    Getting ready to start this build here. The tank is 275 gallon fuel oil tank that is in great shape. This will be mounted on an Harbor Freight Trailer.

    I have been renting pig roasters in the past for catering gigs and I don't like them..IE: Roasters and not smokers. I want to smoke my pigs low and slow. Most of the pigs I do are up around 180 - 200lb er's. My bottom rack will be built to handle this weight. Other racks will be built to handle brisket , and shoulders.

    I have found the calculator for all the dimensions based on my CC size.

    I am looking for imput from the guys who have been doing this awhile and have built their rigs for the "I wish I had done this that way " or "added this to it".

    I like learning from others mistakes or their wish lists. I hope to gets lots of suggestions off the bat before I start making cuts in the tank. Please feel free to post drawings or pics of your ideas. They are very welcome here. I will start off with a pic of the tank.

    Tank dimensions: 60.5" Wide     44" Tall    27" deep

    Tank orientation: Upright (44" tall)

    5 racks

    RF with FB at one end.

    Hope this is enough to get some ideas going here.

    Thanks for all the help in this...
    Last edited: Jul 25, 2014
  2. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

  3. cisweld

    cisweld Fire Starter

    Thanks for that link DaveOmak... Great resource there...
  4. cisweld

    cisweld Fire Starter

    Ok, After lurking through some of the previous builds here, I discovered that there is more than one calculator to use and depending which one you use, have different dimensions.

    Need a pole on which calculator is best and will work with the above mentioned design. I also would like to know the names and links to those calculators... Feldon is the one I went off of... Hurd it was a little tight on the specs...

    Thanks all...
  5. radioguy

    radioguy Smoking Fanatic

    Use feldons with the tweaks recommended here. Dave also has a good one worked out. Those oil tanks are a bit thin and tend to warp. Plan it all out on paper first....don't be in a hurry to cut your doors. Cut and weld firebox first...this will keep doors from warping too much.

  6. cisweld

    cisweld Fire Starter

    Thanks RG for that info on the doors. I will definitely use that advise.  As far as tweaks, What tweaks should I be on the look out for over and above the Feldons Numbers?
  7. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Tweaks.... enlarge the FB/CC opening and area under the RF plate... Using Feldon's, set the calculator so FB is 100% of recommended... then add 50% more to those numbers..... Then make the FB as big as you want... Feldon's calculations are base on the size of the FB which is not a good idea, IMO.... it's the CC that should govern the size of stuff....
    Then the FB should have 2 sets of air inlets... 1 for adjusting the air to the fire for HEAT... 2 for adjusting the air flow through the smoker....

    If you put the charging door on the front of the FB, then the end will have plenty of room to properly position the air inlets....

    Last edited: Jun 20, 2014
  8. cisweld

    cisweld Fire Starter

    Thanks Dave, That makes perfect sense to me... Making these changes sends me back to the drawing board to refigure where things will lie. So basically I am starting with the FB/CC measurement and working everything from there. This will in effect give me my dimension for the RF and then my Grates. The FB seems very straight forward with the air inlet to feed the fire and to feed the CC.  thanks again for the tweak updates...
  9. lendecatural

    lendecatural Smoking Fanatic

    It will also give you the width of the firebox so it matches up to the cook chamber. http://www.1728.org/circsect.htm Use the radius of the bottom of your tank and fiddle with the ED height until you get the target Segment Area number in the lower box. The ED segment height will give you how far up from the bottom of the tank to make your horizontal cut in the tank, and AB will be the width of your RF plate and firebox.
    Last edited: Jun 20, 2014
  10. cisweld

    cisweld Fire Starter

    Thanks Len... I get to cheat a little hear as I have the smoker drawn to scale in CAD... So this will not be as hard for me to fiddle with. TY
  11. cisweld

    cisweld Fire Starter

    Ok, So I went back to the calculator and entered in my new numbers....  Link to BBQ Pit Calculator

    This is what I got. My recommended CC/FB is 22.72 half moon or 202.75 sq in. I add 50% to that to get 304 sq in for the tweak. and my half moon should end up at 28" diameter.

    Let me know if I stumbled here!!!
    Last edited: Jun 20, 2014
  12. jrbuilder

    jrbuilder Newbie

    Had a thought what if you used the fuel oil drum as just the food chamber and then a 55 gal drum on the side as a fire box
  13. cisweld

    cisweld Fire Starter

    I will be building the FB out of .25" steel so that it can handle the heat and it will also double as a grill when not being used as a smoker. The CC will be all meat (The oil tank).

  14. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    You might go back and re-do the numbers..... your FB is 117%.... make it 100 and use those numbers then the FB can be as big as you want... then ad 50% to the FB/CC opening and 50% to the area under the RF plate....
  15. cisweld

    cisweld Fire Starter

    IC Dave... I needed to be very accurate on that as it will put me way to big... Ok... The only Thing I have not seen as of yet is do I run the baffle at the height of the top of the half moon, or is there a dimension I need to hold above it?

    Would I then go off of my numbers for FB at 100% for the chimney? Or off the actual size I end up with for the final size of the FB

    Last edited: Jun 20, 2014
  16. cisweld

    cisweld Fire Starter

    Rough draft done for the build... all suggestions are welcome...

    Last edited: Jun 20, 2014
  17. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Like you have in the drawing above..... The air flow inlets might be a little higher.... more directly into the FB/CC opening.....
    Looks good to me..
  18. cisweld

    cisweld Fire Starter

    Thanks Dave... Yes, I will bring them up to be directly across from the Opening then... I actually had them there in the first place and thought maybe I want to feed the top of the fire a bit... but that is what the bottom inlets are for... Looks like I am good to go then. I will post pics of the build as I go... Thanks again...
  19. lendecatural

    lendecatural Smoking Fanatic

    To get your other questions answered, the cross section area under the RF plate needs to be a minimum of the opening area of the FB to CC or 150% of the area Feldon's requires for a firebox set at 100%, all three areas should be that minimum, FB to CC, cross section area under the RF plate, and area of opening at the end of the RF plate to the cooking area of the CC. Some guys mount the RF plate a little higher than the FB/CC opening required and then run an additional baffle plate into the cook chamber for a foot or two, an inch or so will make a good heat brake. This will keep the RF plate from taking too much direct heat from the firebox and make the temperatures more even in the cook chamber. Keep us posted as you make progress! 
  20. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    One way to make a heat shield...... click on pic to enlarge.....


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