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Welcome to our newest member, SmokyOkie
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  1. #1
    Join Date
    Jan 2010
    Location
    Philadelphia, PA
    Posts
    85

    Default Reverse flow build

    Hello everyone I am new to this forum and this is my 2nd post

    For about the last 3 months I have been researching building a Reverse Flow and have recently started my build.

    Here is what I got so far;

    20 Diameter, 54 Long
    80 gallon tank = 6,160 Cubic inches smoking chamber

    Stack Design:
    Exhaust Chimney Volume
    324 cubic inches needed. Need 4 pipe at 26 (2"of the pipe will extend down below the top).
    • Pipe size 4" x 28" (26" above smoke chamber and 2" below).
    • mount on the same side as firebox

    Drip tray (Thermal Mass)

    • The plate is 1/4" thick steel and about 4" below the grate level welded to the top of the inlet of firebox extending to 4" from the other end of the tank
    • plate should have a slight bend and about a 1/2" pitch the full length to channel liquid away from the firebox and out through the drain.
    • cap the end
    • cut hole in plate and bottom of smoke chamber, weld pipe to plate and extend pipe through to the bottom of tank and install ball valve for draining.
    • weld a piece of mesh in place so nothing will fall below the plate bottom of the smoker


    Firebox design
    Firebox plate steel
    18 High x 18 wide x 20 deep = 6,480 Cubic inches. 6160 is the minimum for the 1/3rd rule of thumb slightly larger than needed but its better to be bigger than smaller.
    Firebox air inlet opening, under coals
    need 4, 2.5 circular holes underneath the coals for the inlet
    Firebox to cook chamber opening
    The firebox hole into the smoke chamber needs to be 12 x 4-1/2
    • " plate steel
    • Air Intake 2-1/2' holes spaced very 2-1/2"
    • Sliding damper 2-1/2" holes every 2-1/2"
    • air inlets are all below the "wood level"
    • air inlets 3 on side of box 2 in the rear of box
    • door on the front of box
    • Thermal plate mounted level with firebox
    • Slide out ash grate with handle 4" from bottom or Basket

    Grease Drain and trap:
    • 1" ball valve looking to get a bigger ball valve

    Grate
    • Expanded steel 9 trade size
    • Midway at the 10 mark

    Counterweight

    • Cable, weight and pulley, will use pipe that can be weighted to adjust.



    I have asked a lot of these same questions on other forums.

    1)The thermal mass plate, does this need to drop on an angle on the firebox and if so how much of a drop for 54"?
    2) If the plate drops downward gradually from the firebox will that hinder the flow of heat and smoke or is this based on draft from the stack?

    We finished the hinges and finished cutting the door





    we started the flat steel around the door and will finish that this week.

    Advice and opinions please
    Thanks
    SQWIB

  2. #2
    Join Date
    Oct 2008
    Location
    Ruskin, FL
    Posts
    6,290

    Default

    That looks like a Sullaire Compressor tank....
    Sounds like you have a nice gameplan and start to your stickburner.
    ~Brian~
    BBQ Jones comp team
    KCBS Member
    KCBS CBJ

  3. #3
    Join Date
    Jan 2010
    Location
    Philadelphia, PA
    Posts
    85

    Default

    Its a Speedaire and the tank is about 5 or 6 years old.I was a little surprised of the condition, I thought the bottom would have been in much worse shape, although I am a bit surprised of the location of the rust on the upper left of the tank, but it's pretty superficial.
    The only thing that worries me about this build is the 20" diameter. I'm afraid 4" from cooking grate to thermal plates are too close, but I have heard of others going as close as 2".

  4. #4
    Join Date
    Oct 2009
    Location
    St Catharines, Ontario, Canada
    Posts
    730

    Default

    SQWIB, I wish you all the best on your build. It's a big undertaking, building a Reverse Flow System. I build one a while back.

    http://www.theqjoint.com/forum/showthread.php?t=4266

    Good air intake and good draw from the stack is the key...
    KCBS CBJ
    ZEEK




  5. #5
    Join Date
    Jan 2010
    Location
    Philadelphia, PA
    Posts
    85

    Default

    Quote Originally Posted by Zeeker View Post
    SQWIB, I wish you all the best on your build. It's a big undertaking, building a Reverse Flow System. I build one a while back.

    http://www.theqjoint.com/forum/showthread.php?t=4266

    Good air intake and good draw from the stack is the key...
    Zeek that is a thing of beauty

  6. #6
    Join Date
    Jan 2008
    Location
    South of Peculiar, MO
    Posts
    6,737

    Default

    Rich, your firebox size looks good to me. Most folks want to build it too large and it uses excess fuel, loses a lot of heat. I made mine 16" X 16" X 21". Does a great job.
    I'd go with 1/2" plate for the firebox though. After a good bit of use 1/4" will give way to the heat and acids produced by wood ash, especially if it gets any water inside. I had a fab shop shear the plate to size for me. It weighs more than my pickup.
    My tank was a 114 gal. propane tank.







    Last edited by peculiarmike; 01-11-2010 at 06:47 PM.
    "If you can't smell smoke it ain't a barbeque joint" peculiarmike

    TQJ Plankowner

    "Life's tough.....It's even tougher if you're stupid."
    - John Wayne

  7. #7
    Join Date
    Jan 2009
    Location
    mid kansas
    Posts
    269

    Default

    keep us posted on the build please
    i really like yours peculiarmike
    Terry here
    christene is here
    watt burners galore
    horizonal oven in thought process (trash now fire pit)
    SS R.F in process

  8. #8
    SmokyOkie Guest

    Default

    I can't give you any more input than you have already collected.

    I will comment though,ie if I understand the question, that a slight fall from the hot side to the cool side should not cause any air/heat flow difficulties.

    As to the distance from the heat plate to the grate, somebody here can surely measure their Lang and give you an answer to that.

    Ask Capt Dan. He'll measure his for you, if he doesn't already know.
    Last edited by SmokyOkie; 01-20-2010 at 03:34 PM.

  9. #9
    Join Date
    Jun 2009
    Location
    Charlotte NC
    Posts
    516

    Default

    i was looking at a buddies lang a couple weeks ago.. and it sits only a couple inches below the grate... for what thats worth...
    "BoB" a leaky Offset Stickburner
    Backwoods G2 Party and G2 Chubby
    UDS

  10. #10
    Join Date
    Nov 2008
    Location
    Jenison, Michigan, United States
    Posts
    769

    Default

    Quote Originally Posted by SQWIB View Post



    Grease Drain and trap:
    • 1" ball valve looking to get a bigger ball valve
    Advice and opinions please
    Thanks
    SQWIB
    Menards has 2" valves for about $35. You will not be happy with the one inch. I used the 1" and had to cut it out and replace with 2". The one ich was always plugged and really messy!

    Your 4" spacing for the thermo mass is about right. In my humble opinon the Lang 2" is too close.

    Quote Originally Posted by SQWIB View Post
    I have asked a lot of these same questions on other forums.

    1)The thermal mass plate, does this need to drop on an angle on the firebox and if so how much of a drop for 54"?
    2) If the plate drops downward gradually from the firebox will that hinder the flow of heat and smoke or is this based on draft from the stack?
    SQWIB
    This needs to drop at about a 1/4" per foot or at a 2% slope. Do not slope it back towards the firebox. That would be a fire hazard. Take a look at this post. I shows a good design and great craftsmanship! Note that he uses a piece of angle to get the slope away from the fire box and also slopes from front and rear to the middle as well.

    http://www.theqjoint.com/forum/showthread.php?t=1459

    It is true that it will trap some additional heat. The 1/4" plate thermo mass will absorb this additional heat and create the radiant heat exchange. This something that you want! The minor reduction in flow will be negligible. If you are concerned about draw extend the stack a couple of inches higher. You can cut some of the excess stack off as part of the tuning process. Also part of the tuning process is placing small vents in the thermo mass along the edge at the tank wall. It does not interfer with the grease draining an will get you the uniform temps through out. This tuning process is purely trial and error. It does take a while but the finished product is ever so sweet.

    Looks like a great project. Keep up the good work!

    Keep us posted and good luck!
    Jerry.Hickory Grove BBQ
    20" x 72" Gravity Feed by Wasson
    Member GLBBQA http://www.glbbqa.com/
    Member KCBS and Certified Judge

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