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  • Effects of differing grinder speed

    I found this thread on HB very interesting... thought some on this board might too.

    Burr RPM affects grind particle size distribution significantly - Grinders • Home-Barista.com

    Cheers,
    Terence

  • #2
    It is interesting, but here are a few brief comments:

    1. That beautiful chart of particle distribution vs grind speed couldn't possibly be based on real data -- it is too perfect. Real data doesn't look like that. It's undoubtedly an "artist's representation" of what the original poster wanted the data to look like.

    2. My Robur has had a variable speed drive for years, and it acts in just the opposite manner as the theoretical grinder portrayed in the chart. in other words, the espresso flow rate is slower when my Robur's rpms are slower. I'm not saying the Korean chart is wrong, I'm just saying that things are more complex than they first might appear.

    3. As Jim Schulman correctly observes on home-barista, one has to readjust the grinder to get matching shots before one can conclude that a given grind speed is superior to another. Originally I had high hopes that my variable speed Robur was going to provide new levels of flavor precision, but I quickly found that the espresso ground at 300 rpm didn't taste much different from that ground at 500 rpm.

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    • #3
      Personally, I don't see that there would be much benefit in slowing down a big conical and I guess if you tried that with a planar grinder, you might start to choke it as the grinds would not be thrown out as effectively...

      Have you formed any judgements from your Robur Andy, apart from the instance you mention above?

      Mal.

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      • #4
        Originally posted by ASchecter View Post
        ... but I quickly found that the espresso ground at 300 rpm didn't taste much different from that ground at 500 rpm.
        Thanks... very useful.

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        • #5
          At a glance those graphs, as stylized as they are, seem to suggest that broadly speaking the speed makes little difference anyway.

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          • #6
            Originally posted by ASchecter View Post
            1. That beautiful chart of particle distribution vs grind speed couldn't possibly be based on real data -- it is too perfect. Real data doesn't look like that. It's undoubtedly an "artist's representation" of what the original poster wanted the data to look like.
            Could be, but it isn't necessarily true. I have seen plenty neat curves in far more variable systems than a coffee grinder. Mind you the lack of error bars is suspect, i.e. each speed was only performed and analysed once. That and the extremely even spacing on the log scale. Those poor Korean scientists have been lacking credibility ever since Dr Woo-suk lied about cloning!

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            • #7
              Originally posted by Dimal View Post
              Have you formed any judgements from your Robur Andy, apart from the instance you mention above?
              Well I like running it at reduced speed: it is much quieter and it is easier to get the proper number of grams when using a timed run time. It makes heavy-bodied shots that are very tasty when the coffee is good and the grind is dialed in.

              It feels like it will run forever; in home use, probably five or six lifetimes. Do you have any specific questions?

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              • #8
                Originally posted by kava View Post
                At a glance those graphs, as stylized as they are, seem to suggest that broadly speaking the speed makes little difference anyway.
                The curves show far fewer fines when grinding at slow speeds. That would probably be significant IF there were still fewer fines when the slow grind was tightened up to match the high speed curve flow rate. But that is a dubious "IF."

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                • #9
                  Originally posted by ASchecter View Post
                  Do you have any specific questions?
                  No mate...

                  Just interested in the extent of your experiments and any results you may have been able to quantify.

                  Thanks Andy,
                  Mal.

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