Temperature variations..

Discussion in 'Reverse Flow' started by inkjunkie, May 16, 2016.

  1. inkjunkie

    inkjunkie Master of the Pit

    Been struggling with fire/temperature control. With the help from a member on another forum we got it figured out...at least the end to end deal. Previously my firebox end would read 325*, middle would read 265* the far end 250*. I likened the FB being so high because the FB is pushed into the CC. About a third of the FB. And yes the dials are calibrated. We got it so that all 3 of them are within 5*...add a small split at 250*, temperature will peak at 275*. Add a split at 255* and it will jump to 325*. Add a large split and,it will either sky rocket to 375* or smoke like an old small block Chevy on a cold winter morning.
    Got curious...clamped a ThermoWorks probe on the cooking grate. In front of one of the recently calibrated thermometer. The tip of the thermometer is about an inch above the grate. Thermoworks read 298*....dial read 265*. This "normal"?
     
  2. joe black

    joe black Master of the Pit OTBS Member

    Not normal to me. I would check all of the therms and probes in boiling water at the same time. Do you have a convection plate in the CC? Other than that, I'm scratching my head.
     
  3. inkjunkie

    inkjunkie Master of the Pit

    All thermometers checked...it is a reverse flow...
     
  4. joe black

    joe black Master of the Pit OTBS Member

    Now, I'm really scratching my head. I tried, sorry.
     
  5. adam a

    adam a Newbie

    Last edited: May 17, 2016
  6. inkjunkie

    inkjunkie Master of the Pit

    Used the calculator from this site. Have spoken with Paul Shirley about the calculators...while he didn't come right out and say it he made mention of using an online calculator.....from what I know he is not a member here so he must be using Feldons. The guy that helped me from the other site suggested that when I build,my next one that I use Feldons...I ran my numbers for the next one on both Daves calculator and Feldons, if I remember right Feldons called for more air intake...hmm....
     
  7. smokejumper

    smokejumper Smoking Fanatic

    Yes, it is normal. It is not uncommon for the mounted dial therms to read lower than a probe in the center of the grate. Both are reading correctly. The probe is what you want to use most often. The door therms are a back up in case the probes fail for whatever reason. As long as  you know the temp difference between the two, you can estimate center grate temps based on door therm temps.
     
    Last edited: May 21, 2016
  8. inkjunkie

    inkjunkie Master of the Pit

    Thanks You Sir...
     
  9. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Ink, evening....  I'm sorry you posted that...  You are wrong....  dead wrong....  

    Smoker Calculator reasoning
    The concept for the changes is below.... Alien and his associates, did an amazing job putting the original calculator together... 100% of my numbers are based on his original numbers... small changes were made for the improvements due to design changes in smokers.....
    The original measurements were taken from SFB smokers with tuning plates I do believe.... The advent of the RF smoker did not make any changes to the calculator... Now the exhaust has to travel twice as far as before, and the original FB/CC opening restricted the air flow from the FB, causing the FB to over heat... Some would get up to 450 deg and higher while the CC wouldn't get over 250.... And then there is the increased friction from the steel.... When using natural draft, any restriction/friction is very detrimental to the flow....
    So, on a whim, the FB/CC opening was enlarged, the area under the RF plate was increased and the area at the end of the RF plate was increased... all by 50%.... That solved ALL the problems.... fuel consumption was reduced.... folks were happy....
    I personally experienced members improvements and fuel usage by the letters/PMs they wrote me on their improvements...... One additional modification was suggested.... members here, tested a second air inlet to the FB.... directly across from the FB/CC opening... That was a significant improvement of some/most smokers.... If the FB was too hot, it could be cooled by opening the upper air inlet.... Also, the fire had a separate air inlet to adjust it's heat output.... It should be installed at or below the wood fire grate....
    All of this has been tested and proven by members building smoker on this forum.... The only place you will find using these numbers... or it used to be... I'm sure many builders are now using these ideas for their builds.... this process has been going for at least 2 years....

    Volume in cubic inches X 0.001 = FB air inlets in square inches...   57,750 cu. in FB needs 57.8 sq. in FB air inlets..

    Link to BBQ Pit Calculator

    Feldon's uses the FB for it's calculations...  Dave's uses the CC for it's  calculations...  

    Shirley Fabrications has had some problems, over the years, with some of their  smokers not flowing air and smoke too well.....  It was documented on here...  
     
  10. inkjunkie

    inkjunkie Master of the Pit

    Maybe I am just a moron....you said...."Volume in cubic inches X 0.001 = FB air inlets in square inches... 57,750 cu. in FB needs 57.8 sq. in FB air inlets"....using a firebox sized 19×17×15 my calculator on my phone came up with 4845. Plugging in this number to the line I quoted from your post...4845×.001=4.845. Feldons came up with...Link to BBQ Pit Calculator
    In case the link didn't work Feldons came up with 14.54....when I went to school 14.54 cubic inches (Feldons number) is bigger than the number the other calculator came up with, which was 4.845 cubic inches.
    Shirley produces how many smokers a year? To produce a problematic one or two....well it is laughable to say that they have had problems over the years...granted...I have only been here a short while...and spend very little time here but don't remember seeing any mention of a bump smoker from Shirley.

    Expected nothing less than an argument. As to the fellow that helped me suggesting I use Feldons for my next one...at least he HELPED me figure out what was going on with my RF. Kevin didn't cop an attitude with me, nor did he fail to explain things to me so that I understood them...Hell, he even gave me his number...
     
  11. smokejumper

    smokejumper Smoking Fanatic

    This is a case of comparing apples to oranges.

    Dave's calculator bases all the numbers on the CC volume. It is the CC volume x .001 that gives the the FB air inlet sizes.

    Feldon's uses the FB volume x .003 to calculate the FB Air inlet size, however since the Feldon's FB is based on the CC size x .33, the end result is the same.

    This is not a precise science, and many successful RF smokers (including my own) have been made using Feldon's.

    The only true difference between the two calculator is the 50% increase in the FB-CC opening in Dave's calculator. While I consider this change benign, I do not consider it essential. I have seen no evidence that RF smokers were excluded in the development of Feldon's calculator. That appears to be an assumption. 

    Look at the information that is out there, and decide for yourself, but nobody should be insisting that there is only one right way to build a smoker (RF or otherwise).

    Inkjunkie is not dead wrong... he related his experience and the information he received from other sources. He may be mistaken on air inlets, but that is not the issue.

    As for Kevin, he will never consider any new ideas, and that is a shame. As an example he will always recommend a half-moon FB/CC opening, and not consider one that follows the contour of the CC. The only reason for this is that he has a handbook for half-moons, and does not want to use a section calculator even though it could buy you extra space for your racks.
     
  12. inkjunkie

    inkjunkie Master of the Pit

    Apples to oranges? Huh? They are both Reverse Flow calculators, are they not? How they come up with the numbers is 100% irrelevant. Firebox size is firebox size. FB-CC port size is FB-CC size. Intake size is intake size. Must be a "FOD"....
     
  13. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Feldon's uses the FB for all it's calculations....   My calculator uses the CC for it's calculations...    And my calculator improves air flow by increasing the restrictive pinch points in the smoker... thus better air flow...   decreased FB temps and improved fuel consumption.... 
     
  14. inkjunkie

    inkjunkie Master of the Pit

    Shirley must be building some really chappy smokers...he is booked put to January....you?
     
  15. smokejumper

    smokejumper Smoking Fanatic

    However it now appears that you are not interested in how the calculators work, nor in admitting your mistake.

    You are only interested in defending your position and taking cheap shots at forum members who if you are being honest are only trying to help.
     
  16. c farmer

    c farmer Smoking Guru Staff Member Moderator OTBS Member SMF Premier Member

    Easy guys. Keep this civil.
     
  17. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    C Farmer, evening....   It's time you looked at what inkjunkie is posting....    SmokeJumper is correct in what he noted about IJ...   IJ made some mistakes and doesn't want to find out why or where, just bad mouth others....
     

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