Where to start with a RF build?

Discussion in 'Reverse Flow' started by inkjunkie, Jun 18, 2015.

  1. inkjunkie

    inkjunkie Master of the Pit

    Going to be using a 60 gallon compressor tank. Cut the base and the pump/motor plate. Was messing around in the garage today and made the hinges for the CC door.

    Could not get the 90* bent tight enough so I just cut and 4 pieces, bent the 2 that will be going on the door and welded them back together. Neighbor offered me use of his torch, forgot to grab it before he left for work. But with both tanks being empty and how Jim neglects things.....

    Planing on "borrowing" data and ideas from other 60 gallon builds from here and another site.

    Guessing that I start with tacking the CC hinges on prior to cutting the door. Cut the CC-FB next? Weld the RF plate in prior to building the FB? Does it matter, within reason in what order things are done?

    RF plate thickness....1/8" ok?

    Will be building a pair of wheels to mount off of the bottom of the firebox. Insulating the firebox. Still tossing around my goofy warmer idea. With it just being the 2 of us don't see a reason to build more than one cooking rack.

    So folks...help me out. Once I make some measurable progress I will start a build thread...
     
  2. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    How tight do the pins fit in the tubes.... When you weld to the tubes, they will shrink....
     
  3. inkjunkie

    inkjunkie Master of the Pit

    Not real tight, but will keep this in mind.

    Going to put the seam on the bottom, I think. FB will be on the left side. Wondering about CC door size placement...need to do some reading prior to cutting
     
  4. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    RW liked to start with the CC upside down..... cut the opening for the FB... weld the FB in place.... turn it over cut the door... cut out the opening of the FB/CC... Then the RF plate and drains... If you want, tack weld angle iron where the RF plate goes... set the RF plate in and tack weld or leave it free.... it ain't going anywhere... it can be in 1, 2 or 3 pieces... it's only diverting hot, smoky air... put handles on it for easy removal.... build supports to hold the racks for the meat... they can be set on the RF plate.... or bolted in place....

    Remember the more you weld, the more stuff twists and warps.... welding in supports, during the build process, can help eliminate twisting..
     
  5. inkjunkie

    inkjunkie Master of the Pit

    FB-CC cut....understand that if the port between the FB-CC is to small there may be a problem with the FB overheating and/or the CC not getting up to temperature. What if the port is to large? I used the calculator. Tank is about 20" in diameter. Assuming the tank is constructed of 1/8" steel that would put it at 19.75". Which would mean the radius is 9.875. Using 9.875 and 4.75 the calculator spit out 56.706 as the segment area. Daves calculator suggests that I need 55.44 for the port....will this work correctly?
     
  6. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Not a problem... If you are using 1/4" metal for the FB, don't forget to figure that in... So now the 4.75 tall cut out becomes 5.00" tall to allow for the metal thickness of the FB at 1/4"....
     
  7. inkjunkie

    inkjunkie Master of the Pit

    The fill plate...that covers the gap from the kerf of the grinder used to cut the CC door...should it go to the door or the tank itself?
     
  8. inkjunkie

    inkjunkie Master of the Pit

    Kinda goes without saying....welder broke....
     
  9. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    When in doubt, make stuff larger so it breathes better.....
     
  10. inkjunkie

    inkjunkie Master of the Pit

    The bottom of the RF plate is in line with the top of the FB-CC cut out, correct?
     
  11. inkjunkie

    inkjunkie Master of the Pit

    Just nuked one of the tubes to a piece of scrap metal....pins still pivot freely...
     
  12. Sure be looking forward to pictures. Like Dave said a little larger doesn't hurt. Check and recheck things as you go,

    Gary
     
  13. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Depending on smoker design, here are 2 alternate smoker FB installs.... One on the left has less flow resistance... because the FB is installed farther into the CC.... Both are good... Both may require a heat shield on the upper part of the FB and first part of the CC... If you install air inlets properly in the FB, there should be no need for a heat shield and temps should be even across the cooking grate... NEW DEAL... if the exhaust stack calls for a 6" exhaust 34" tall, use a 7" exhaust 34" tall... I am changing the smoker build tutorial to reflect that....
    tykenn28 had outstanding results enlarging the exhaust... read his results... for what it costs, the results are worth it.... that is if you want the best smoker you can build...... http://www.smokingmeatforums.com/t/187302/250-gallon-reverse-flow-first-build


    ... ...
     
  14. lendecatural

    lendecatural Smoking Fanatic

    1/8" is a little skinny for a RF plate. If possible, go thicker since you are depending on that metal mass to keep temperatures stable across the length of the plate. 1/4" would be better and 3/16 if you can't find that. Besides, 1/8" tends to warp like crazy when you try to weld it up...
     
  15. inkjunkie

    inkjunkie Master of the Pit

    How would one go about cutting the compressor tank to accomplish the one on the left? Would I still use the 4.75" (plus the .250" for the firebox)? How deep into the compressor tank would I cut?
    I have a 4'x10' sheet of .250" mild steel. The scrap yard in Spokane always has quite a bit of .250" remnants.
     
  16. lendecatural

    lendecatural Smoking Fanatic

    It is easier if you cut the tank past the dome where it turns back to the cylindrical section to inset the firebox. Then you measure up the height of the cut and draw a line around the dome at that height.You can cut a block of wood that height 1/4"and walk it around with a sharpie. If the floor is flat, you will get a square layout.

    Yes, go with the 1/4" plate, will be much better for heat transfer.
     
  17. inkjunkie

    inkjunkie Master of the Pit

    Me no comprehend....read it a few more times....with the tank on the floor, or in my case a steel desk, cut a 2Xwhatever to 4.75 plus the .250....place it against the edge of the dome and walk around the dome. This will give you the height of the FB-CC port. When cutting it out cut past where the dome is welded onto the cylindrical tank. Will go out and snap a picture of the area I am thinking....

    The top of the firebox is at the same height as the RF plate, correct?
     
    Last edited: Jun 20, 2015
  18. lendecatural

    lendecatural Smoking Fanatic

    Does your compressor tank have two domes and a cylinder section in the middle if you look at it from the side? If so, from the right end, go back to where the dome part turns into the cylinder part and make your vertical cut to 4.75 there, then draw a line around the right end of the dome at that height until you get back to where the dome turns back into a cylinder on the back side. As you look at it from the side when you finish the cuts, it will look like the notch in Dave's sketch. 

    You just need a chunk of 4x4 with some more wood on top until the height is the same you need the height of the cut to be, then just slide it around the tank and mark where it touches the dome end with a marker, I like Sharpie brand since it marks good. Does that make sense?
     
  19. inkjunkie

    inkjunkie Master of the Pit

    Tape is just for reference. So I would cut it on the bottom side of the tape? I like the idea of pushing the FB further into the CC but am concerned about this creating a hot spot...
     
  20. lendecatural

    lendecatural Smoking Fanatic

    If you do a search on "baffle plate" it can be a problem, but most guys build smokers that way. That would be a good use for some of that 1/8" material you have. The upper air vent in the firebox helps almost as much since it moves cooler air across faster. But, yes, it will be hotter there, for sure, how much depends on how well the smoker flows. Most guys declare victory if it is 5 degrees of difference across the grate.

    Yes, you would cut there if it is the right height, it's just harder to mark the same height around the dome, that's why I suggested using a block and a marker.
     
    Last edited: Jun 20, 2015

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