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  1. psychophysicist on

    Bottom bracket cups have the same threading as freewheels, so you put a BB cup in as a thread extender. I’ve done this to set up a “retrodirect” where you pedal forwards in one ratio and backwards in another.

  2. JG-at-Prime on

    So that’s how these work. 

    I’ve seen these adapters on eBay for years and have never seen them mounted before. 

    It’s these things:
    https://www.ebay.com/itm/177659566093

    And some combination of freewheels: 
    https://www.ebay.com/itm/358616962390

    I think the requires a 7speed hub to do the conversion. 

    The application is to have one freewheel connected to the cranks and the other connected to an auxiliary power source like an engine or motor. 

  3. We just ignoring the fact that you are tightening the threads by hitting the teeth on the sprockets with a big metal bar? OK, cool…

  4. PlatlRadl-72 on

    But wouldn’t it make more sense to have too separate size freewheels?

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