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Thread: Torque arms

  1. #1
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    Torque arms

    Why does a Rohloff have a torque arm when an Alfine doesn't?

  2. #2
    Another Retro Grouch
    Reputation: pursuiter's Avatar
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    An internal gear hub's planetary gears orbit the sun gear on the axle. An IGH's axle needs to be held tight so it doesn't rotate. The Rohloff and Bendix hubs use a torque arm, the Shimano, SRAM/Torpedo and Sturmey-Archer hubs use washers that fit into the dropout slots to prevent axle rotation.

  3. #3
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    Yes, I understand that there is a torque that needs to be restrained, what I don't understand is how the Alfine can 'get away' with just washers when Rohloff don't think this is satisfactory.

  4. #4
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    That's a good indication of the difference in maximum torque the hubs are capable of withstanding.

    If the bike has the Rohloff specific dropout, it can use the OEM 2 axle plate instead of a torque arm, but if you use that same axle plate on a typical light track end it will spread it quite easily.
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  5. #5
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    Rohloff has an OEM-1 torque arm that works similar to the Shimano/SRAM non-turn washers, only it's bigger and requires a longer dropout. It fits into a track mount perfectly, but has been known to pry apart the steel mount under load (unless it was specifically desiged to take that load). The Rohloff can impart a considerably larger torque to the frame, partly because of the gear range, and location of the direct drive gear (11). I suspect they tested the Shimano/SRAM/Strumy style non-turn washers, and found they were not sufficient for the job.

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