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Thread: HM on Offset OK Joe

  1. #1
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    HM on Offset OK Joe

    Hey there,

    Been reading these forums for a while getting advice... but this is my first post.

    So i did a test run with my reverse flow oklahoma joe with the HM and I believe an adapt-a-damper. The test run ran great... constant temp @ 225 for 5 hours, barely used any charcoal (i normally was going through a whole bag on a smoker without the HM). Well, based off of that success i decided to pop in 2 briskets.

    https://imgur.com/a/CW3h93f

    This did not go as smoothly. It only ever got up to about 200, the fan never shut off and the damper never closed, and after about 4 hours, i had to go open the lid on the fire box every 45 minutes or so in order to get more air in. Still had plenty of charcoal... just wasn't getting the right airflow. I think part of it was the fact i did an empty smoke vs a smoke with basically 40 lbs of cold meat cooling down the inside...

    This leads me to believe I will need a much larger CFM fan. Well... Where can I find a damper system that would support my current setup? I would like to keep using the fan that pushes into a pipe and or pipe system underneath my smoker box.... just with a WAAAY stronger fan, preferably 45+ CFM.

    Any thoughts?

    Thanks everyone in advance!

  2. #2
    TVWBB Guru Steve_M's Avatar
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    From the pic you posted, the diameter of the pipe between the damper and the fire box looks like it should be increased substantially. I'd be surprised if that unit needed anything larger than 10 CFM.

  3. #3
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    Hmm. Right now it is a half inch steel pipe, I could go up to a full inch but the flange I hooked it to might get kinda weird connecting it up. I could also probably shorten from an 8 inch pipe to a 4 or 6 inch pipe, as the only part that had gotten hot on it was the inch IMMEDIATELY sticking off of the firebox.

    The wife wants me to throw on some briskets in a couple weeks, hence why I'm scrambling for suggestions!

  4. #4
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    I used an HM on a Brinkmann clone of that same smoker for a couple of years. While that was a vast improvement over no ATC, it was still decidedly below what I wanted.

    1) Seal up EVERYTHING on it that you possibly can. I'll bet you're loosing a lot of airflow out through the ash drawer.
    2) I used a bathroom vanity drain tailpiece (12", you can go as short as 4") fed from Tom's barrel damper, with a dog bowl over the firebox inlet.
    3) I built a charcoal basket to run the Minion method. 6-8 lbs. of natural lump would get me about 4 hours, maybe.
    4) Baffle plates to vent the firebox more centered than right at the firebox. Best I could do was about a 50 degree drop across the chamber.
    5) Pit thermocouple got clipped to the thermometer stem.

    A lot of it depended on ambient weather, primarily if the wind was blowing. That'd pull more heat out anything IMO.

    I finally gave up on it when I discovered how badly it was rusting out between the firebox & cook chamber.

  5. #5
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    If your damper door is removable, then make a new door and go to an electrical supply or your local Lowe`s or Home Depot or Ace and get a small piece of 1" emt conduit and a couple of compression fittings. Drill hole in your new plate you can make from scape steel or a piece you can get from Lowe`s or HD. Drill hole to match treaded end of emt connector and secure with lock-ring. Seal new adapter with high temp RTV from auto parts store to maker airtight seal. You might also need some metal duct seal tape to enlarge the end of the conduit that will fit in end of Adapt-A-Damper. Use enough tape to make tight fit. I have used this before and if you a good 6" from heat source you will not have any issues. This should work and get you the maximum flow from the damper.

  6. #6
    TVWBB Honor Circle Bryan Mayland's Avatar
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    I think Steve hit the nail on the head with his observation. The adapt-a-damper is designed to be used with 1" pipe which I'd say is the lowest you want to go. I've done a lot of experimenting with 1.25" pipe as well and I think it works more efficiently but not enough to justify they extra cost of the fittings. The little fan working against the 0.5" pipe is probably just a little too restrictive to work on a big smoker. You might be able to fudge it by opening the firebox a little to let it naturally draw in a little extra air, but I think the best solution is to widen the input to 1". You can actually just get a 1" NPT nipple for $2 to mate the two, although you'll probably need to widen your intake into the smoker to use it. The difference in airflow will be pretty dramatic, especially since the lower restriction means it will draw more air on its own through the damper and the fan won't need to run as much.
    I'm that HeaterMeter guy what ruins everybody's free time.

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