Flow problems with my custom build smoker

Discussion in 'Smoker Builds' started by metaldoctor21, Sep 27, 2013.

  1. metaldoctor21

    metaldoctor21 Fire Starter

    I built this smoker and it seems like I am trapping all my heat at the firebox. My cooking chamber is 36" long and 16" diameter 1/4" wall pipe.

    My fire box is 18"x18"x18" 1/4" thick steel.

    My exhaust is 4" pipe 24" long. It comes out the end similar to a jambo pit. It has a 5.5"x5.5" square cut in it and a pocket welded to the side that the pipe bolts to. The bottom of that hole is 6.5" from the bottom and the top of the hole is at 12" from the bottom of the cooking chamber and it's center in the pit. My cooking grate is 1.5" up from the bottom of the hole.

    The intake vent is a 5" circle. The center of the hole is 6.5" from the bottom of the fire box and in the center of my charcoal grate. That leave 4" under the charcoal grate to the bottom of the fire box. The hole is center on the end in the door.
    The fire box to cooking chamber hole is 5"x10". The bottom of the hole is 6" from the charcoal grate and the top of the hole is 1" below my cooking grate.

    If anyone has any suggestions or sees anything wrong with my design I would appreciate the help. I am new to smoking and to this forum. I will try to get pictures posted. Thank you.
     
  2. metaldoctor21

    metaldoctor21 Fire Starter

    Fire Box Side
     
    Last edited: Sep 29, 2013
  3. metaldoctor21

    metaldoctor21 Fire Starter

    Front Side
     
    Last edited: Sep 29, 2013
  4. metaldoctor21

    metaldoctor21 Fire Starter

    Exhaust Side
     
    Last edited: Sep 29, 2013
  5. bkleinsmid

    bkleinsmid Smoking Fanatic

    [​IMG]

    Whats up Doc?.........sorry, I had to do it.....

    That is a great looking build. My 1st thought would be that the exhaust is too small in diameter. Have you run the calculations on the sizes yet?

    Brad
     
  6. metaldoctor21

    metaldoctor21 Fire Starter

    I did run the calculations and everything is what it's supposed to be. Another thing I noticed is that when I put charcoal in the cooking chamber to use it for direct heat the coals will go out. I have the charcoal on a tray about 1.5" from the bottom so air can flow under them, but they won't stay lit. That is another reason why I am assuming it is a flow problem.
     
  7. sqwib

    sqwib Smoking Guru OTBS Member

    That is a beauty.

    Hey can you do me  favor and temporarily raise your grate above the intake and try again, I would love to see if that helps.

    Everything else looks good, I would prefer the stack outlet at the top of the tank but thats just me.

    Hey Ribwizzard, think you can help us out here?
     
  8. sqwib

    sqwib Smoking Guru OTBS Member

    I'm curious to see if a flow beneath the fire would improve the draft, If I was a betting man I would say moving the grate above the inlet and allow air to come in underneath the heat source will help with the drafting.
     
  9. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Doc, morning...... VERY NICE smoker........  I like it.....  Where did you get those dimensions from....  did you take them from another Jambo smoker ??     Using the Feldon's calc, your FB is 241% of recommended which should not pose a problem...  FB air inlet is large...   I would plug the top half and try it...     Also, the configuration of the smoker, I don't see any way charcoal will stay lit under the food grate....   Does Jambo say their smokers will work with charcoal under the food grate ??  And I can't remember for sure but, I think Jambo FB/CC opening is above the food grate.... and the exhaust is below the food grate.....  I could be mixing that up with another smoker...   getting too old to remember it all....

    In the link, is what I came up with for a SFB smoker, which is similar in design to yours....  

    Link to BBQ Pit Calculator

    We will work with you to get this thing working.....   Dave



     
    Last edited: Sep 27, 2013
  10. metaldoctor21

    metaldoctor21 Fire Starter

    I have tried moving it up 1.5" from where it was at in the photo and that didn't seem to change anything. I will try to move it all the way above the inlet this weekend and see if that changes anything.
     
  11. metaldoctor21

    metaldoctor21 Fire Starter

    You are correct on the jambo configuration. I was just trying to give an idea on how my exhaust was because I didn't have any pictures posted at that time. I just came up with the dimensions for the pit as I was building it. I had a family friend who was my smoker expert helping me, but he past away due to cancer before I was able to finish my pit in the spring. I built my fire box bigger, so I could store more charcoal in their for a longer burn time. Do you think the size of the fire box is effecting anything? Also what do you mean by their is no way charcoal will stay lit in the fire box with my configuration?
     
  12. sqwib

    sqwib Smoking Guru OTBS Member

    One more question, did you ever see any smoke come out of the inlet hole?
     
  13. metaldoctor21

    metaldoctor21 Fire Starter

    I have some more photos I will try and post this evening. I am trying to post them from my phone and am having a problem getting them to load. Will moving the stack up or up and a couple inches from the end have an effect on anything?
     
  14. metaldoctor21

    metaldoctor21 Fire Starter

    Yes smoke does come out the inlet hole. Also when I open the firebox door smoke will flow right out of the fire box.
     
  15. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    There are many designs for smokers......   What style was your original thought....  It seems to be a mix of different designed smokers....  

    I notice you have no tuning plates, which would be appropriate for that smoker...   Then the stack "plenum" would be placed above the cooking grate...  

    If you wanted a Reverse Flow, the stack would be placed above the firebox, just above the cooking grate....  

    A Jambo, the fire enters the cooking chamber above the cooking grate and the exhaust is below the cooking grate...  

    Dave
     
    Last edited: Sep 27, 2013
  16. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    It's no big deal....  I often think one thing and type something totally different...  If that's what you did.... we must be related...  [​IMG]
     
  17. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    I did run the calculations and everything is what it's supposed to be.

    One last question..... what calculator did you use......    Dave
     
  18. metaldoctor21

    metaldoctor21 Fire Starter

    It is kind of a mixture of different things I have looked at. The friend who was helping me was from Colorado and I am from Illinois. I decided one day I want to learn to start smoking things and I knew I could build it, but designing it was my weak point. I built it without physically ever seeing a smoker. Where I live smoking isn't very big, so try to go to cook offs and snoop around wasn't an option. My friend was giving me some pointers over the phone. He had been in several cook offs, so he was my best bet for info. What would have to be different for charcoal to stay lit under the cooking grate? Just curious. Trying to learn everything I can. I really appreciate the help I am getting so far. Thanks everyone.
     
  19. metaldoctor21

    metaldoctor21 Fire Starter

    Feldon
     
  20. metaldoctor21

    metaldoctor21 Fire Starter

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