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8242Re: Sturmey classic AW explanatory video (Was: Sturmey S3X)

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  • Dan Burkhart
    Mar 1, 2013
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      There are no gears that have fewer parts whirring around as these hubs are all constant mesh. The only gear not rotating at any given time while a hub is in use is whatever sun gear is coupled to the axle .
      The power path through those gears can have an impact on efficiency however.

      --- In Geared_hub_bikes@yahoogroups.com, "Andrew Curl" <methuselah@...> wrote:
      >
      > Well, I am an engineer, and if I understand your question correctly, it depends on which gear you spend the most time in. I was once a speed freak, so I configured my gearing so I spent most of my time in 3rd gear on a four speed hub. This meant that fewer of the internal parts were whirring around, which in turn meant less wastage in terms of my energy, spinning gears unnecessarily; also if the bits in the hub weren't working against each other, logically they'd wear out less quickly as well.
      >
      > As I understand things, the new generation of SA hubs (my specialty) are better than they used to be, (in terms of dimensional correctness, ergo, efficiency) so the question is more of mechanical drag as opposed to longevity. "Overdrive" as I understand it means that each tooth of each gear takes a higher torque loading, "underdrive" means that each tooth will meet each other tooth more often, 'cos more gears are spinning around. I cannot see that there's really much in it. That said, I did wear out pivot pins, but I never stripped any gear teeth.
      >
      > -Andrew UK
      >
      >
      > ----- Original Message -----
      > From: Tom Hart
      > To: Geared_hub_bikes@yahoogroups.com
      > Sent: Friday, March 01, 2013 2:58 PM
      > Subject: [Geared_hub_bikes] Re: Sturmey classic AW explanatory video (Was: Sturmey S3X)
      >
      >
      >
      > Dan, great video.
      >
      > In engineering terms, is there any benefit, or disadvantage, from
      > overdrive vs underdrive?
      >
      > Tom.
      >
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