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UDS Air inlet size?

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    UDS Air inlet size?

    Advice wanted.
    Hi folks recently completed my first UDS....had my first cook today and I just could not generate sufficient heat. (My brisket was salvaged in the electric oven).

    My UDS currently has 4x 3/4” inlets elbow to ball valve. (see photo - two outlets out of view).
    Do I need to make these outlets bigger?
    Shake Drum during cook to remove ash?
    Small spurts from blower helped?

    Regards,
    Attached Files

    #2
    Welcome to The Pit. Sorry, but I can't help.

    Comment


      #3
      If you look at Gateway and Royall smokers, the air inlets are larger in diameter than yours. They also have a smooth large-radius elbow to reduce turbulence and a sliding flap type of closure that offers no resistance to air flow when fully open. The Hunsaker dispenses with the tube entirely and uses a sliding gate at the bottom of the smoker for the air inlet.

      Your 3/4" pipe is going to have more friction loss and turbulence in the pipe due to the small diameter and the short elbow. If the ball valve does not have a full port opening (meaning the opening in the ball is the same diameter as the pipe diameter), that will further increase the friction loss when the valve is full open. These will increase the pressure drop in through the inlet pipes and slow the air flow through the smoker.

      Gateway, Royall, and Hunsaker smokers also have a short chimney coming off the lid. I gather your UDS is just venting through the bung. A chimney will increase the velocity of the exhaust gases and that will help to pull air through the smoker compared to no chimney.

      I'm not a UDS maker, so take my comments with a big grain of salt. Just noting some of the differences I can see that would affect the natural draft of air through the smoker.

      Shaking to reduce the ash and blowing into the inlets may cause ash to flow up through your smoker. Not sure that's something I'd want to do while smoking food -- might be best to solve the airflow problem without resorting to things like this.

      https://www.gatewaydrumsmokers.com/c...gallon-smokers
      https://www.hunsakersmokers.com/coll...-vortex-smoker
      https://www.royallsmokers.com/wood-s...rum-smoker.htm
      Last edited by IowaGirl; July 7, 2019, 06:32 PM.

      Comment


      • gdsim1
        gdsim1 commented
        Editing a comment
        Boom! 🎤

      #4
      IowaGirl makes excellent points. The problem I see is airflow. Here is a chimney that you can attach to the top with a damper. https://www.sausagemaker.com/Square-...-p/19-1213.htm Just get some stove caulk and caulk around it. If that does not work you will need to increase the size of your in take. Also how does the air flow over the coals? Since the exhaust is over the intake is there a baffle to direct air over the coals?

      Good luck.
      Last edited by mountainsmoker; July 7, 2019, 12:35 PM.

      Comment


        #5
        I’m with the others, and think your 3/4 inch intakes are too small. Even wide open, that is only 1.77 sq inches of total air intake. If the ball valves are not a full 3/4 inch opening, it is even less. That’s no airflow at all in my opinion. Even going to 4 1 inch intakes would take the total intake to 3.14 sq inches.

        A Gateway drum, or intakes from udsparts.com, are 1.5” diameter. Two of those allows 3.53 sq inches of air intake. I would suggest swapping your 0.75 inch intakes for 1 inch, or plug 2 up and add 2 1.5 inch intakes.

        Comment


          #6
          Thanks for the feedback folks!!! Damn internet instructions!

          Anyways my project for next weekend sorted. Shame I’ve already got a bunch of drill holes through the drum. Should have consulted here prior to lift off.

          I’ll work on increasing the 4x inlet size to inch



          May the smoke be with you

          Comment


          • Aussie_Pitstop
            Aussie_Pitstop commented
            Editing a comment
            Finally got it done. Well over budget and well past deadline. Added 2x 1.5” taps on. Gets piping hot. Looking for using it next weekend.

            Thanks for the advice folks

          #7
          I really think increasing the size of the inlets will help a lot. Kudos to jfmorris for digging up the dimensions!

          I'd also give some thought to adding a short chimney to increase the draft. That will help too. And if you get or make a chimney with a cap, that will keep rain out of your smoker. I gar-ron-tee that will also come in handy one of these rainy days.

          Comment


            #8
            Based on this, I think 2 inch pipe can thread into the bung hole...

            Comment


            • Jerod Broussard
              Jerod Broussard commented
              Editing a comment
              Huhuhuhe he said bung hole

            #9
            Finally got it done. Well over budget and well past deadline. Added 2x 1.5” taps on. Gets piping hot. Looking for using it next weekend.

            Thanks for the advice folks
            Attached Files

            Comment


              #10
              Lookin good!

              Comment


                #11
                If you still have trouble, try these



                They are what i used on my UDS

                udsparts.com is a great place to look when building or modifying smokers

                Comment


                • Aussie_Pitstop
                  Aussie_Pitstop commented
                  Editing a comment
                  This would have been much easier and cheaper.....had some taps lying about thankfully, buying taps etc new is incredibly expensive here in oz

                #12
                Second time round I could do it for half the price I reckon.

                Did my first cook on Sunday.....ribs turned out to absolute perfection. Over the moon
                Attached Files

                Comment

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