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Roasting drum speed control?

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  • Roasting drum speed control?

    If you guys used a custom built drum roaster.

    You would know that theres an electric motor attached to a drum.

    The problem is i need to control the electric motor voltage without affecting the heating coil and fan voltages.

    Anyone care to help me out, to have almost control freak like mods to this machines

  • #2
    Mate you need to be clear when asking for advice otherwise we cant help.

    Are you trying to achieve variable speed during be able to vary the speed of the motor/drum at will during the roast, OR are you just trying to change the speed of the drum period. If so, that can be done with gearing / pulleys / belts.

    If you are trying to vary the speed of the drum at will during roasting, do you have the right type of electric motor that will withstand that kind of control? It is not as simple as varying input voltage..... And of course this all falls under the classification of "its only money" long as the cost of the mod can be justified.

    Additionally, if you vary the speed of the drum during roasting, what are you going to do with the heating and air speed (if you have a machine that can vary air speed), because to just vary the drum speed without being able to account for the others may well be detrimental to the roast process...

    This all falls under the objective of ***what are you trying to achieve?***.

    Suggest you talk to an electrical engineer and / or electrical fitter, with a thorough explanation of what your current roasting plant set up is, because these questions cannot be answered simply without knowledge what your set up is like. You may also need to speak to a roasting plant engineer.

    Hope that helps.


    • #3
      Good answer TOK, I've been pondering that one for a day or little info.
      Is the motor AC or DC? Installing constantly variable speed, two speed drive or as TOK said, just changing the drum speed permanently
      require different actions from changing the frequency (AC), armature voltage (DC) or gearing (either).

      Read TOK's reply carefully; especially the bits about the effect of change to drum speed on air speed and heat dynamic parameters
      and the the suggestion of talking to a qualified technician.


      • #4
        I'd imagine that with varying the drum speed 'on the go', it will also affect the critical mass of beans that can be accommodated in a particular batch at a particular rotational speed. Lots of variables to consider...



        • #5
          Indeed Mal Indeed


          • #6
            Thanks for pointing out the gears/belts parts,

            I'm trying to figure out how to install these and regulate speed.

            I'm also trying to discover how changes in speed affects roasting.


            • #7

              About your question on "what are you trying to achieve"

              I want to get some knowledge of how drum speed affects roasting.


              • #8
                Hi there. Ok you are trying to find the optimim drum speed for your roaster, after which the speed will remain 'static" ie not modulate throughout a batch roast.

                For simple drum batch roasters that are in the main roasting by conduction of heat. Roughly speaking: When drum speed is too slow, the outside of the bean burn on the drum while the inside of the bean is still under roasted. I.E. uneven roast. Break open single beans and look at the "section" through the bean. The outside will be dark and the inside will be significantly lighter. Certain characteristics will result in the cup.

                Drum spinning too fast = beans not in contact enough with the side of the drum, therefore not enough conduction of heat, again uneven roast through the bean but different effect to above.

                The right drum speed will be a compromise where the roast inside the bean will be more even and may I say, will result in beans that should give a smoother cup than either of the above.

                After that, I am afraid you will have to work it out for yourself if you have a custom built roaster...

                Hope that helps, and have fun working it out


                • #9


                  Probably if i manage to adjust the drum speed........

                  I'll dial it in by looking at the results and slowly adjusting till my batch comes out right....... ;D


                  • #10
                    Use a Micro drive to control an AC motor turning the drum through a reduction gear . Full on the fly speed control at your fingertips. A lot of other options available on most of the micro drives on the market as well which can come in handy.

                    Java "Gothot got it!" phile
                    Toys! I must have new toys!!!