I'm not sure if I made a mistake?

Discussion in 'Reverse Flow' started by ohdannyboy, Jun 8, 2013.

  1. ohdannyboy

    ohdannyboy Fire Starter

    Hello. This is my first build. i plan on making a reverse flow smoker. I used the feldon calculator to get the size of the firebox size correct. What I have is a 80 gallon tank. It measures 20" ID and around 65" long. 5/16" thick Tank. The FB is 1/4" thick, 20" deep 19" wide and 23" down but the bottom 5 inches are going to be used as the opening if the air vents and also a ash pan. I'm assuming the internal firebox height would be 18" then. The calculator says:
    FB specified 6840
    FB recommended 6160
    4" pipe @27.23" long
    Half moon opening 11.80"
    FB to CC 54.72 square
    I already cut the opening on the tank and should have waited. Here's where I doubt myself. I cut the opening 6" deep and 6"height for the firebox to sit in the CC. Did I take too much off?[​IMG]
     
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  3. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    DannyBoy, morning....    Is the cut width you made in the tank about 18 1/4" wide at the top part of the cut.... And you said it was 6" high... 

    If I understand correctly everything is fine...   

    What has been done to the firebox.... is it built.... how much is done... and on what sides....    Take pics of everything from all angles....   Then I will know where you are and how to help....   

    Dave
     
  4. ohdannyboy

    ohdannyboy Fire Starter

    Yes the cut is right about 18" across. Sorry I left that part out. I burned out the junk last night. I noticed after words that in the picture my friend was doing pull-ups from my patio!
     
  5. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Danny, morning..... Sorry it took so long.... Been busy....  

    OK, your smoker set up is perfect.... no worries....   

    Cut out a part circle for the FB to CC opening in the 19" side of the FB.....   I suggest inserting the FB into the cutout in the end of the CC.. Scribing the circumference of the CC onto the FB.....  The top of the FB is where the RF plate should be welded....  4 1/4" up from the bottom of the CC, draw a line parallel to the top of the FB... Inside that scribed line is the 49 sq in opening for heat/smoke flow....  If you are concerned about too much heat in the firebox end of the cooker, heat deflector plates can be installed in the FB and the first 6-12" of the RF plate.... attached is a drawing for easy install... I suggest bolting the heat shield so it "floats" and will reduce warping...  leave room at the edges of the heat shield... 1/4" or so...  1ea. 4" pie vent at the top, across from the FB / CC opening...  2 ea. 5" pie vents at or below the fire grate.... leave plenty of room below the fire grate for ash....  

    for the pie vents, scribe a 5 1/4" circle, X at 90 degs.. 1" intact center portion for bolting..  5 3/4 to 6" plate for the adjuster... cut out matching pie sections to the FB on the adjusting plate....  scribe before cutting...  either way, you want the holes in the FB "undersized" to the adjuster plate for a complete seal if possible...  Your FB being over sized to the calculator is not a problem...  I don't allow for it being over sized.... It will store more heat....  the CC and flow through it, is what is important....  Since it's 3 am, check my numbers...  

    Dave..... click on pictures to enlarge.....


    The heat shield.... something on this order will "insulate" the FB and help move the heat

    to the CC......

     
    Last edited: Jun 10, 2013
  6. ohdannyboy

    ohdannyboy Fire Starter

    Wow! Thank you Dave for al that information. I think the only difference I'd like would to change the lower vents to sliding vents. I'll put the pie vent up top. What is the top vent used for?
     
  7. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

  8. ohdannyboy

    ohdannyboy Fire Starter

     
  9. ohdannyboy

    ohdannyboy Fire Starter

     
  10. ohdannyboy

    ohdannyboy Fire Starter

     
  11. ohdannyboy

    ohdannyboy Fire Starter

    It's going to be a slow process but it will sure be worth the wait. Thanks to DaveOmak I feel more comfortable with the build. I know the FB is bigger than what I really need but I plan to hang a 1/4" plate from the top to allow for more even heat displacement and that should use up some of that extra space. I also left room below the fire box to allow for air vents coming from below to push up into the fire box. Hopefully it will be a clean burn. I will also include a vent above the fire grate to allow for heat adjustments. Below the air vents i cut a space to put in a ash pan. I'll make it out of 1/8" plate steel so it will last a while. Thanks for all your help and more pics of the build to come.
     
  12. so ms smoker

    so ms smoker Master of the Pit Group Lead OTBS Member

      it's looking good! Keep the pics coming!

      Mike
     
  13. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Looks good so far.....    [​IMG]......     Dave
     
  14. ohdannyboy

    ohdannyboy Fire Starter

    Thank you. I will keep you posted with my progress. Oh another question. I was planning on using 1/8" inch plate for the RF plate but after comparing to the Lang 48 which mine is similar in size, they use 1/4" plate for the RF. before I go welding in any plates, I'm guessing if I beef up the RF plate then I might have a more even temperure in my cook chamber. Would that be correct? I could easily get a used piece of 1/4" plate if it needs to be more stout.
     
  15. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Danny, morning...... Thermal mass is what makes for even temps... 1/4" would be great...  Have you thought about making a removable RF plate ??   A well fitting RF  plate only needs tack welding or sitting on a ledge of angle iron...
     
  16. Build is looking good so far. I'm still in.

    Happy smoken.

    David
     
  17. ohdannyboy

    ohdannyboy Fire Starter

    Ok. I'll beef up the RF plate to 1/4" then thanks for the advise. Progress will be slow due to long work hours. Today I basically mocked up the wheels and got side tracked by making a backing plate for a classic parking meter. I don't know where it came from cut a quarter got you an hour parking permit!
     
  18. ohdannyboy

    ohdannyboy Fire Starter

     
  19. ohdannyboy

    ohdannyboy Fire Starter

    I'm not yet to the point of putting in the RF plate. You mentioned something about a removable rf plate. I thought about this before I started the build. What would be the advantage to that? When I was getting the sketch together I gave it a second thought because I wanted to avoid grease running into the fire box and changing the temps and also the flavor of the meat.
     
  20. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Your firebox has a lip that will stop the grease and the drain should be left open for the grease to drain....   Removable RF plate, just for the heck of it...  cleaning under it.... changing the smoker if needs be..... putting in a gas burner in the future....   Basically to leave your options open.....  
     

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