Mini Vertical Reverse Smoker Build Questions

Discussion in 'Reverse Flow' started by fendbass22, Mar 21, 2016.

  1. fendbass22

    fendbass22 Newbie

    Hello Gentlemen,

    I've been lurking for a while and thought I'd make a post as I am looking for some opinions as I have not smoked before. I was going to by a WSM but I do a ton of fabrication on the side and have a some 24" wide sheets of 3/16" left over and want to make a smoker with the remaining. I wanted it to be small since I have too much crap as it is and won't be feeding an army. I also plan to automate it as well (just the damper for now) with HVAC controls which is my day gig.

    Where the little dampers are will be an actuator on one side and transformer and controller on the other side on either side of the shaft. I have done all the math and I am right where it should be according to I have also made the depth 14" as a starting point if the scrap I have left allows me deeper, I will do that. Just getting things going first.

    Off to my questions:

    1.) My FB is in proportion to the CC. This will only leave a 5" x 13" x 14" charcoal basket after clearing the damper shaft and leaving room for ash. What kind of run time would you guess at 225F? Looking for opinions because the FB/CC ratio is right but I feel like my charcoal basket will be small for a 4100 cu in CC.

    2.) The math says I need a pretty good size opening for the exhaust but I don't want to mount on the outside because I want to use this year round. If it is inside of the cook chamber, anyone know if I can make the exhaust smaller in diameter since it will be warm the whole length if tube? May insulate and place outside as well. I have not decided.

    Plan is to insulate and finish over in 16ga. That's my reason for the indents in the bottom so it hides all the controls for a better look. There will be intake louvers in the 16 ga so it can run in the indents to the dampers.

    Thanks for your time and great forum.

  2. fendbass22

    fendbass22 Newbie

    Willing to hear any opinions. Even if they are harsh!
  3. smokejumper

    smokejumper Smoking Fanatic

    That is a pretty small smoker, and being fully insulated your burn rate should be pretty low. I think your charcoal basket may be big enough.

    You can always refuel mid-cook if it turns out to be too small. As for the exhaust, I would not recommend making it smaller, even if it is inside the cook chamber. You need the area for proper flow, and that area does not assume any particular temp difference between the smoke and the outside air.
  4. fendbass22

    fendbass22 Newbie

    Thanks for the feedback. When refueling do you just scatter a few in there or fire them up then put them in?
  5. smokejumper

    smokejumper Smoking Fanatic

    Ideally you would have a second coal basket that you can fill and light and just pull out the spent one and put in the fresh one.

    With just one coal basket, you should pull it out, shake off the ash, put in fresh charcoal and add in lit coals to get it started and put it back in the smoker.
  6. fendbass22

    fendbass22 Newbie

    Cool thanks.

    I did some measurements of my scrap and it looks like I can make the smoker deeper from 14" to 17" with what I have.
  7. fendbass22

    fendbass22 Newbie

    Some progress pictures. I thought the build would be going quicker but it's tough with a 5 week old at home...

    Was planning on using an HVAC controller but thought it would be more fun with an Arduino and touch screen running the damper.

  8. smokejumper

    smokejumper Smoking Fanatic

    Looks like the drawings. That is a good sign.
  9. fendbass22

    fendbass22 Newbie

    A few more from today. More progress next weekend maybe.

  10. fendbass22

    fendbass22 Newbie

    Anyone have any opinions on where to put the two sensors? Probes I have are only about 3" long. I was thinking one on each side, drilled through the back 1/3 the way from the bottom of the CC. So there would be a left and right sensor. Would top and bottom centered be better? Either way I am planning on having the option to average them or pick individually.
    Last edited: Apr 25, 2016
  11. smoking homer

    smoking homer Newbie

    I vote top and bottom as it will give some indication of how the heat is stratified in the chamber. I use a thermocouple wire that I wrap around the grate each

    time I cook.

    Good luck
  12. fendbass22

    fendbass22 Newbie

    Doors done-ish. I have 1" insulation but I haven't figured out how I am going to finish the outside. Used wood stove gasket rope and Rutland gasket cement.

    Trays are cut.

  13. fendbass22

    fendbass22 Newbie

    Put some temporary door hinges on to try it out. I don't want to finish the outside until I know how it works.

    Burned it off at around 400F.

    Stack pic.

    Today I went to do some testing and the wife has a ham bone with plenty of meat and fat left to season it up. I figured I would wash it out with soap and water then fire it up and it would dry up the inside before the ham bone. Big mistake. Only had it running about 260F (still tuning) and the steam/water did something weird to the wood stove rope and it was adhering to the box better than the cement to the door. Most if it just peeled right off. I was pretty angry, this was one of the days I could really dedicate some time getting her figured out. Oh well.

    Looked at my kitchen oven and here is what the gasket looks like. I bought two of these for $49 meant for my oven and I know what I'm getting dimensionally. The wife self cleans it 3-4 times a year which is super hot and it does just fine. Not sure how it will work on the firebox.

    Pictures of actuator setup. I had it on the shaft directly and it was way too hot. Used some of the insulation intended for the outside and made a linkage. It still gets pretty hot. I just don't want plastic fumes working their way in the intake. I will probably end up moving it on the back and running the rod in somehow. Still need to work this out.

    Also, during the burn off I noticed the thermistors weren't reading right and as I suspected they just won't work at these temps. I ordered thermocouples from adafruit and seem to be working great.


    Last edited: Jun 26, 2016
  14. fendbass22

    fendbass22 Newbie

    New gaskets work great.

    At the ends I just took about 6" piece of the gasket and folded in have to put about 3" in each end. Working great.

    As I suspected the thermistors would stop working as they weren't high temp rated. Adafruit sells thermocouple type-K breakout boards for Arduino so I now have two of those. Figuring it all out.

    Put it all in a 6" weather tight J-box.

    One of the setup screens. I still have some tweaking to do of the parameters. It's pretty tough because there is so much metal that to see a change in temp after moving the damper is takes a while. I will be insulating soon which should help getting it all dialed in.

    unclebubbas bbq likes this.
  15. Awesome build, looks really good. 
  16. fendbass22

    fendbass22 Newbie

    Hoping to get the 1x1" frame done then enclose it with diamond plate. See how it goes.
  17. Sweet

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