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Firebox Position

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    Firebox Position

    Hi Guru's, coming at you from Oz and I need some input on a stick burner design, if you could indulge me with your experience?
    I have been getting acquainted with a COS for the last 18 months and I have destroyed some perfectly innocent pieces of meat as I have been learning the craft.
    I am at the point where I can now produce some reasonably edible food off the little sucker but it's just too small.
    It's time to go [email protected] out and build one, as I can't afford to buy what I am looking for.

    I was discussing the design with an Engineer friend and he suggested putting the firebox in the middle, underneath with outlets into the cook chamber on two sides.
    The idea is that it halves the size of the openings and means the firebox can sit lower in the cook chamber, therefore maximising the space. I am thinking of an 'RF' plate over the firebox with gaps at each end, and the chimney in the middle.

    After spending some time dredging the forums here I have seen this sort of thing only hinted at.
    Has anyone had any experience along these lines?
    Really appreciate any input on this, I have a 22" x 33" air tank and a mig in the shed ready to go!!
    Thanks in advance

    #2
    Although I have cooked on stickburners fer many decades, I have never built one one (yet)

    Yer idea sounds very plausible...

    This site might be of some assistance, in finalizin yer design/build...

    Comment


      #3
      Henrik Ahumadora are two gents you’ll most definitely want to chat with.

      Comment


        #4
        Hmm, depending on the design, you might get temp drops in either end of the food chamber. Could you provide us with a basic sketch of what you are building? As for the issue your engineer friend is trying to solve, is it really a problem?

        and ignore the Felton calculator, it is not correct.

        Comment


          #5
          The first pit I ever built (2011) was designed the same way. I had to drag the tank through the middle of my house in Buenos Aires to get it in the back yard. A friend owns it now and I cooked on it last year. 600+ pits later I have grown a bit.
          Draw a sketch and post pics of what you have to start with. Good thing is you just need a grinder and welder to build it. The pit I built works great. Only problem was a hot spot near where the stack exit is.

          Comment


            #6
            Thanks for the feedback guys, I have attached a very simple artist's impression of what I am thinking.
            Initially I thought of the chimney mounted central at the top, but I suspect it would be better being lower towards the back but still central.

            To a noob like me, this design would seem to help with maximising space as well as heating more evenly. But then why haven't I seen more smokers of this style around and I suspect it's for some reason I am not aware of right now, hence my initial question.

            Henrik I am intrigued by you saying the Felton calculator is wrong. I compared it to the tool at Smokerbuilder and found they both came up with similar numbers. Can you direct me to what you feel is a more accurate calculator please?

            Welcome any more feedback, good or bad, before I commit with the grinder
            Attached Files

            Comment


              #7
              Stu. A 22x33" is a pretty small pit. You can build it like you pic and as long as the openings are large enough it will work. Having just one door with chimney in the middle will create a hotspot. Also don't mount the stack directly above the meat or it will drip crap all over the food. Maybe easier to do a standard offset. Before you cut into it I will do you a drawing of how to cut the doors.
              Feldons calculator numbers were constructed from combing about 6 different pits calculations. Hardly scientific when are you planning on putting it together?

              Comment


                #8
                Originally posted by Ahumadora View Post
                Stu. A 22x33" is a pretty small pit. You can build it like you pic and as long as the openings are large enough it will work. Having just one door with chimney in the middle will create a hotspot. Also don't mount the stack directly above the meat or it will drip crap all over the food. Maybe easier to do a standard offset. Before you cut into it I will do you a drawing of how to cut the doors.
                Feldons calculator numbers were constructed from combing about 6 different pits calculations. Hardly scientific when are you planning on putting it together?
                Haha, yeah I know it's about the size of a spare wheel of some of the rigs I see on here, but compared to the 12" x 24" Ebay COS that I'm learning on, it's a nice step up. I'm not planning on doing whole hogs, just want something big enough to do a reasonable sized brisket or put more than two racks of baby backs on. Did a 2 1/2kg leg of lamb yesterday on the COS and it came out pretty good, family liked it, but I was having to roll it over every hour so it would cook evenly.
                You are starting to talk me into just going with normal RF design, but that why I asked the question here. I had not even considered the chimney dripping onto the food, you make a very good point, clearly you have done this a lot
                A drawing of the doors would be very much appreciated if you could find time to do a quick sketch for me. I'm not planning on doing any cutting for a month or two. I've got to pour the concrete slab at the back of the shed for it first

                Is cutting the door like the sketch below an option, or is it best to leave the end shells intact?
                I was thinking of doing this and using flat bar top and bottom, around the inside, with tape for the seal.
                Really appreciate your time mate

                Attached Files

                Comment


                  #9
                  Just a few words on why Feldon's calculator is wrong. As Ahumadora says, it's an extrapolation of several cookers, done by someone who hasn't built one. Trying to put together a pit calculator is admirable, but the basic problem is that the input data is wrong. For the most basic case, it is assumed that the firebox should be 1/3 of the food chamber. For an average backyard pit (like the one Aaron Franklin builds commercially, or the LSG 20x36) it is correct in that it is a good choice. However, that fact is then used as a rule to determine that if you build a bigger pit, then the firebox should grow accordingly, relative to the food chamber. That is wrong. Just do the calculations for a bigger pit (like Aaron Franklin's 1000 gallon pits). The calculator tells you to build a monstrous fire box, which doesn't make sense. The same size error shows up when you try to calculate a smaller than normal pit. It will recommend you to build a fire box where you can't actually fit a normal size split.

                  The second big issue is that it is assumed (incorrectly) that the volume of the smoke stack is related to food chamber and firebox size. Anyone with knowledge in thermodynamics and draught calculations knows it isn't so simple.

                  Let us know of your plans and we'll help you along the way.

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