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Thread: Roller mill differential speed

  1. #1
    Join Date
    Oct 2017
    Location
    Hamburg, Hamburg, Germany
    Posts
    10

    Roller mill differential speed

    Hi all,

    I am in the process of scoping out a malt mill, and one supplier is quoting a double roller mill where the rollers operate at different speeds, with ratio 1:1.5. The faster roller is rolling at 700 rpm, diameter 155mm.

    Everything I've ever learnt says that our goal during milling is to crush the grains, not grind them, with minimal ripping apart of the husks. It would seem to me that the differential speed rollers would create a shearing effect, thereby tearing the husks. This does not sound ideal, or am I missing something?

    I was wondering what the consensus is on roller mills: whether it is better to go for same-speed rollers vs. differential speed rollers?

    Best,
    Dieter

  2. #2
    Join Date
    Oct 2014
    Location
    Kent, WA
    Posts
    306
    Quote Originally Posted by dieterneck View Post
    Hi all,

    I am in the process of scoping out a malt mill, and one supplier is quoting a double roller mill where the rollers operate at different speeds, with ratio 1:1.5. The faster roller is rolling at 700 rpm, diameter 155mm.

    Everything I've ever learnt says that our goal during milling is to crush the grains, not grind them, with minimal ripping apart of the husks. It would seem to me that the differential speed rollers would create a shearing effect, thereby tearing the husks. This does not sound ideal, or am I missing something?

    I was wondering what the consensus is on roller mills: whether it is better to go for same-speed rollers vs. differential speed rollers?

    Best,
    Dieter
    No definitive answer for you, but I just recently noticed this on my Schmidling Maltmill...but the differential between the rollers is much smaller. There's just a 1 tooth difference between the drive gears. My theory is that it separates the husk from the kernal better, but isn't enough to shred the husk. OTOH, while 1:1.5 seems like a pretty big difference, it's not in the rollers for very long. I'm curious what the correct answer is.

    Regards,
    Mike

  3. #3
    Join Date
    Oct 2017
    Location
    Hamburg, Hamburg, Germany
    Posts
    10
    Thanks for the reply Mike. Interesting that you also have a differential roller mill, albeit with a much lower ratio.
    Have you noticed any big difference in how your grist looks compared to other breweries?

    I just find it strange that this topic is almost absent from ProBrewer - it makes me wonder how common differential speed rollers are. I may just ask to have equal speed rollers to be on the safe side.

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