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Geared Unicycle Blog Post: three basic designs

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  • #31
    Originally posted by johnfoss View Post
    The amount of pull depends on the (vertical) offset between the wheel axle and pedal axle. The less offset, the less work involved. Like riding an artistic bike on the rear wheel, with one foot pedaling and the other on a rear foot peg. As you pull the handlebars up toward you, the amount of force required goes way down as the pedals get more above the axle. When you get it all the way up, it's not difficult at all.
    I think we do agree on this, minus the numbers. It would be easy to ride seated, riding standing would require pulling back on a handle... pulling how hard?

    It looks to me (by counting the chain links) that the Huni-Rex has the pedals offset about 4" . My seat base is about 24" up from the axle, so to offset my 180 lbs standing on the pedals, I would need 30 pounds of force pulling into the seatpost (4*180 == 24*30).

    But I'd be pulling mostly upward, toward my shoulder. Call it a 60 degree angle for easy math, and I have to pull with 2x the force - 60 lbs - to net 30 lbs back toward the seatpost.

    I think that's a lot, especially with one hand, and it's more than I would want to put into flexing a KH or other extension bar, but who knows. One thing riding unicycles teaches us is that people can get pretty good riding just about anything.

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    • #32
      Originally posted by Mikefule View Post
      Centre of rotation of the cranks behind the hub would require a very weird seating and riding position indeed.
      Unicycling: great for your thighs.

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      • #33
        It seems placing the pedals ahead or behind would only be an issue if the frame is kept straight. Pedals would be out of line from seat and ground contact. BUT if you bent or curved the frame slightly so all 3 were in line it should be fine. OR does that open another avenue of bad geometry?

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        • #34
          Fascinating article. I am still learning basic unicycling but love to at least read stuff like that!

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          • #35
            Originally posted by jona View Post
            It seems placing the pedals ahead or behind would only be an issue if the frame is kept straight. Pedals would be out of line from seat and ground contact. BUT if you bent or curved the frame slightly so all 3 were in line it should be fine. OR does that open another avenue of bad geometry?
            Think about that again...

            The relative positions of the seat, pedals and wheel are crucial. The shape of the frame that joins them is only relevant from the point of view of strength, rigidity and weight. You can't put the pedals in fromt of the wheel then curve the frame to put them in a different position, then say that there isn't a problem with them being in front of the wheel because you've just moved them to above the wheel!
            My first novel, Bridge of Otherwhere, Michael Wilkinson, on Kindle. A tale of subtle magic, mystery, friendship and love. Tinyurl.com/Bridge-of-Otherwhere For US$ page: TinyURL.com/OtherwhereBridge

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            • #36
              Another potential prob w/ the cranks forward or back of the axle is turning since your CoG would not be in line w/ the wheel.

              I considered this prob a while ago while considering full suspension designs (my idea is basically like the rear of a FS Treck bike).
              Last edited by skilewis74; 2012-12-14, 05:39 AM.
              Ride everywhere and never just ride anywhere. If you can ride where you are going within a hour, do it, and if you can do a trick 50-75% of the time do it along the way.- Bob Burnquist

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