First RF Build. Excited!

Discussion in 'Reverse Flow' started by buda q, Oct 9, 2013.

  1. buda q

    buda q Smoke Blower

    Howdy, Folks. I am starting my first RF build. It's actually my first pit build at all. I've been using an old Brinkman for a number of years. I will be posting pics as I go. Here are a few pics and I have my first question. I am using a 24" x 5' cc, 5/16" steel. I am also going to use a 24"x24" round firebox. I've looked and looked on the site for my answer on the firebox, and have had no success. DAVE hope you're reading, you seem to know these things.

    The problem that I have is trying to get the right volume for the cc/fb opening. The calculator says that I need 87". I will be putting the rf plate 7 1/2" from the bottom. The center grate will be 4 1/2" above the rf plate. Most posts here have said to put the top of my firebox at the rf plate. My concern is that I will now have a football shaped opening, not the typical half moon openings that you see with the square fireboxes. I thought of perhaps moving the top of the fb up to the center of the cc, but I don't think that there should be that much gap at the top of my firebox above the cc/fb opening. I think it would restrict the heat flow and have a hotspot at the top of the fb. I've been doing my homework and am real comfortable with the other calculations.

    I don't know how to calculate what that "football" opening gives me for square inches. Any takers?

    And I've enjoyed watching the builds and have learned so much from you pro's. I appreciate any info that you may provide.

    We cut the pipe with an abrasive blade on a skill saw and it seemed to work good. Didn't want to drag the torches out. I plan on doing this with the doors as well. I saw the one build where the heat of the torches really warped the doors. It's just time, right??

    After cutting the two pieces, I realized that this is going to be a Big pit! I'm sure it will attract more friends.

    Keith








     
  2. buda q

    buda q Smoke Blower

    Well, I kinda went old school trying to answer my own question and I think I got it. I broke out the graph paper and went to scale on what I was trying to accomplish on the fb/cc opening size. What I came up with is moving the top of the fb 1" above the rf plate. That will give me about an inch or two more square inches than what the calculator says. I hope that the 1" gap over the fb/cc opening doesn't create flow problems, but I guess I could always add a deflector plate in the firebox if need be. If anyone can confirm I would greatly appreciate it! Thanks.
     
  3. lendecatural

    lendecatural Smoking Fanatic

    Greetings Buda Q,

    I may be wrong and I'm sure Dave will be along to set this right; however, the circle calculator he has on his signature line ( http://www.1728.org/circsect.htm ) will come very close to your numbers. If you list the segment height or ED, and the radius of 12" using 1/2 your RF plate height in your case of 3.75", I come up with 45 square inches for the sector area. This number is doubled for a total of 90 square inches. So you aren't above but even with the RF plate if it is at 7.5 inches. Think of it as the seam of a football in this case and the seam length is 17.4".

    You should be good to go.

    Len
     
  4. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Keith, evening....  Well, you are my guinea pig.....  here is a template I'm putting together to simplify the calculations for an RF build....   

    You are the first to see it...   

    See if it makes sense.....  let me know where I need to make the instructions easier to understand....   The circle calculator is used for the FB/CC area....   There is no way to simplify that thing...

    http://www.1728.org/circsect.htm

                             .........click on pic to enlarge..........


    Edit:  The numbers that are derived in the above calculations take into account the increased area

              under the RF plate and enlarge the FB/CC opening to equal that area....   

              I did that because of Ribwizzards suggestion to use the area under the RF plate as an extension

              of the FB....  With proper air intakes on the FB there should be a significant reduction of the hot  spot

              on the RF plate and top of the FB.... thus saving fuel and more even temps in the Cook Chamber.....
     
    Last edited: Oct 10, 2013
  5. pigbark

    pigbark Smoke Blower

    Interesting ...
     
  6. buda q

    buda q Smoke Blower

    Thanks a bunch, guys. That clears things up. And it ain't bad being the guinea pig, Dave....!
     
  7. chezey

    chezey Fire Starter

    I just finished mine. Its almost the same size as yours. 48" cc and 24"x24" fb. Here are a few pictures. Hope it helps. Still have a few minor things to finish on it. I have fired it a couple of times seems to work good . Just need to fine tune it now to get the temps closer between the racks.

    [​IMG]

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  8. Can't wait to see the build in progress
     
  9. Mine's made out of the same material as yours, pretty much. Before you get too far look into having that epoxy blasted off. It won't burn well, and will take somewhat longer than forever to grind off...it sort of melts and moves around. It's a great size to work with though!
     
  10. pigbark

    pigbark Smoke Blower

    Chezey, how much room between racks on that one you built? its nice man, good build..
     
  11. chezey

    chezey Fire Starter

    PigBark thank you. From the bottom to center is 4" and from center to top is 3". I can gain an inch by turning the center or bottom upside down or remove any one of them for larger cuts of meat if I need to. I just added all three to use the available space if I need it.
     
  12. buda q

    buda q Smoke Blower

    Sorry for the delay in responding. It is actually raining in Texas!! Not good for work or for pit building, as my welding area is small, outside, and has limited cover. I did want to thank:

    Chezy: thanks for the pics. Looks awesome and makes me jealous that mine is not finished. I want to have a door to load with like the cooking chamber doors, but also want to have a door on the end with vents to be able to clean out the ashes with. I'm trying to research as many layouts as I can. How do you remove the ashes? What a nice smoker.

    Doodle: thank you for the info on blasting off the paint/epoxy!! It is quite thick and I was wondering how to remove it. I have torches and also a propane torch that I use to start fires with, but it seems like that would take a long time. And grinding??? heck no! I will get it blasted. What kind of place did you take yours, a paint shop, metal shop?

    Gary S: you hang with me. Everything will be posted in detail once we really get going. Looks like I need to get that green stuff off though.

    Dave: you just sit in that chair and watch the fun...haha.

    Thanks again for the input, folks.

    Question: I've seen some people just spot weld the 1" trim on the doors. I would think that a full weld is recommended?
     
  13. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

    Question: I've seen some people just spot weld the 1" trim on the doors. I would think that a full weld is recommended?

    Notch the door with a grinder every couple inches.....  spot weld from the inside.....   a full weld will warp the door....  be sure the door has about a 1/8" gap so the spot welds don't hang the door...     A clean door trim looks so much better than welds....  check out some of the builds....  Check Ribwizzards builds.... he shows how to notch and weld the door trim...
     
    Last edited: Oct 14, 2013
  14. buda q

    buda q Smoke Blower

    Thanks, Dave! As a newbie, do I just search WR's name to find his builds?
     
  15. buda q

    buda q Smoke Blower

    RW that is
     
  16. daveomak

    daveomak Smoking Guru OTBS Member SMF Premier Member

  17. chezey

    chezey Fire Starter

    Buda Q thank you. I have a fire grate from a fireplace that I made fit inside. It has legs on it and I take it out to clean the ashes. I just use a tin coffe can to scoop the ashes. Can't be hot and not the ideal way but it works. I just didnt want to cut a door in it right now, I can change it later if I want to.
    The fire box was on another smoker I built and was round. I made it flat this time so I didnt have to put a baffle plate to run it under the rf plate. The top of the fire box is welded to the rf plate. Seems to work good for me but will find out more with cooking and testing.
    Another reason I made it flat is because I may insulate the fb in the future. It gets very hot and don't want the grand kids getting burned. May be hard to insulate since its round but I think it will help save on fuel.
    If you have questions ask.....I'll help with anything I can.
     
  18. Doodle: thank you for the info on blasting off the paint/epoxy!! It is quite thick and I was wondering how to remove it. I have torches and also a propane torch that I use to start fires with, but it seems like that would take a long time. And grinding??? heck no! I will get it blasted. What kind of place did you take yours, a paint shop, metal shop?


    [/quote]Found a commercial sandblaster. Even he was griping about how long it took. Good to know pipelines are well protected, though.
     
  19. bob1961

    bob1961 Smoking Fanatic

    how does using that circler saw with cut off wheels in it ??....I was thinking on doing that....
     
  20. chezey

    chezey Fire Starter

    I used a 4 1/2" grinder with a very thin 6" cutting wheel to cut the door in mine. It works good if you don't apply much pressure. To much pressure wears out the blades very fast. I think I used 4 or 5 at about $3 each. Not to expensive.

    This is dangerous because you have to remove the guard to fit the blade on the grinder.
     

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