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  • A good idea?

    Reading the thread about adjustable length cranks, cranks with two or more pedal sockets, and so on, I was suddenly struck by an idea. Ouch.

    Having multiple holes along the length of a crank would weaken it, but it could be strengthened or widened to compensate for this. The real problem, therefore, would be when riding on the shortest setting. The extra bit of crank thus exposed would keep clipping your ankle bone and possibly snagging your shoe lace.

    But... What if instead of cranks you had discs? A square or splined socket in the middle, then a disc of radius, say, 190 mm with a smooth edge. Now imagine 3 (or more) pairs of holes at different radii, each pair diagonally opposed. The disc needn't be too heavy, but could be locally reinforced near the pedal sockets.

    Being a disc, even on the 'shortest' crank setting, there would be no protruding crank clipping your ankle bone at specific moments in the pedal revolution, and there would be nothing to snag your shoe laces. Just a smooth surface with four (or 6?) unused holes in it which would present no hazard, or could be blanked with a simple threaded plug.

    The advantage would be that a rider with, say, a 26 inch wheel could have pedal positions equivalent to, say, 130, 150 and 170 mm, giving him or her the option of cruising at high speed along the flat, a bit more leverage for hillier sections, and extra leverage for down hill runs.

    The advantage from a manufacturing point of view is that a careful engineer with reasonable home workshop equipment could make these. At the simplest level, a stainless or aluminium alloy disc could have the socket end of a normal crank glued/welded into palce, and the threaded sockets could be simply welded to the back. On the outside it would look pretty (smooth disc) even if on the inside it looked a bit rough and ready.

    Mr. Harper, in particular, is this a daft idea, or does it have some merit?
    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

  • #2
    Kind of like splitting an ultimate wheel and putting a frame and seat in the middle, eh?
    Will

    Comment


    • #3
      I think it would work. I don't think a disc is necessary, it would constitute alot of unused material. You really just need a crank that is twice as wide as usual made from aluminum plate (much lighter than steel) and fully radiused. The disc would be more likely to prevent banging the sides of the leg on the crank as it slowly rides up the leg on the pedal stroke. The disc is just as likely to snag shoestrings at the pedal connection, though. The tricky part is broaching the taper or the spline.
      -Greg Harper

      Nipples...do you ever have enough?

      Change is good. Bills are better.

      Comment


      • #4
        2 things:

        1) Shoelace snagging. This hasn't happened to me for years because I now tie them in a double double bow. However, I imagine that having a (potentially) 150 mm crank but with the pedal set at 120 mm would leave 30 mm of sticky out bit which would be just the thickness to slip into a loose loop of shoelace. With the disc idea, there would be no such projection. Wrapping the shoelace around the pedal shaft itself could happen with any arrangement of crank, disc etc. so the disc idea makes no difference to that bit. So, all in all, I think it reduces the snagging shoelaces problem compared to the older idea of cranks with 2 or 3 holes.

        2) Wasted materials. There are two possible approaches:
        1) Make a pair of cranks drilled for 3 pedal positions, then add a thin (possibly perspex) disc to reduce the snagging and ankle knocking effect when the short position holes are used. This idea could use exisiting castings as I believe tandem cranks are available with multiple drillings. (Reference elsewhere on this forum.) The disc would be similar to the spoke protectors which were once fashionable for keeping derailleur gear mechanisms out of the spokes.
        2) Use a metal disc which is strong enough to contribute to the rigidity of the 'crank'. As much of the force on the crank is rotational, surely a disc has maximum possible strength against rotational forces. Yes, it might warp because the force isn't perfectly aligned with the disc because it is applied through the projecting pedal, but a strengthened rim, or radial bracing could be used to eliminate warping.

        On reflection, the cheaper and simplest option has to be the first: a beefier crank with 2 or possibly 3 holes, and a protective disc of some light (and decorative?) material to prevent ankle knocking and shoelace snagging.

        Clearly it could be done, and clearly, to some extent, it would 'work'. The question is how *well* would it work?

        The total weight of the assembly would be marginally more than for a pair of 175 mm steel cranks, even though the rider would be pedaling on 120 mm cranks sometimes. However, look at the weight of 3 ring chainsets on bicycles - not a big problem.

        Swapping the pedals would take a few minutes but could be incorporated into the ride's plan. (Ride there on shorts, transfer to mediums for the trails, longs for the really steep bits, and back to shorts for the ride home = 3 changes, coinciding with a drinks break, a sandwich break and a chocolate break.)
        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

        Comment


        • #5
          RE: A good idea?

          > But... What if instead of cranks you had discs? A square or splined
          > socket in the middle, then a disc of radius, say, 190 mm with a smooth
          > edge.


          An interesting idea.

          > Mr. Harper, in particular, is this a daft idea, or does it have some
          > merit?


          I'm not Harper, but I think it's a daft idea, that has some merit.

          Fresh thinking is how new inventions are born. So, first we question the
          freshness. Most ideas in cycling were originally done 100 years ago or more.
          This includes clipless pedals, split seats, recumbents, etc. This one
          probably was also, but I don't recall seeing it. You know what it's similar
          to? Chain guards on regular bikes; the kind that are circular and attached
          to the largest chainring. Same idea, to keep your pants, shoelaces, etc.
          from getting snagged. But not to protect your ankles. Do people scrape their
          ankles on bikes?

          I used to scrape my ankles every now and then, in my early years of riding.
          I can't recall it happening to me in many years though. So I think there's a
          technique issue there.

          Logically, the first thing I would do to research this issue would be to
          make a set of cranks with three holes in them. Make the cranks nice and fat,
          with a rounded end. The fatness would compensate for the weakness caused by
          the holes, and might also make it less of a shock if it hits your ankle. The
          round end will make it less likely to snag a shoelace.

          Then make sure your shoelaces aren't dangling.

          Then ride this, and pass it around to lots of people. It might work fine. I
          think it will.

          But that would end the discussion on your idea. There's more. The reason for
          the huge disk is to protect your leg from the protruding crank. But now you
          have to worry about the edge of the disk. Assuming 190mm crank length,
          you're bringing the edge of the disk 380mm's up your leg with each pedal
          stroke. This might open up an equal or greater-sized can of worms.

          Plus, whatever material was used in the non-structural parts of the disk, it
          would have to be stiff enough to hold up to constant friction with your leg
          (if no friction, you don't need it in the first place). But the disk part
          could be plastic. So weight is not necessarily an issue. I just feel that it
          would look something like a dog or cat with one of those big cones on their
          head that the veterinarian gives them to keep from licking off medication or
          bandages or whatever.

          If made of metal, the disk could be used as a grinding plate. Better use
          steel then...

          But I don't think you need this giant disk. You are only trying to protect
          against the protruding end of the crank. So why not just a circle, centered
          around the innermost pedal hole, with radius to the end of the crank? Then
          you would have cranks that look like big lollipops. But there would be no
          shock of the crank end coming around, and way less material required.

          But I really think you should start out with a three-hole crank and see how
          you like it first. It might turn out to be just fine.

          Stay on top,
          John Foss, the Uni-Cyclone
          jfoss@unicycling.com
          www.unicycling.com <http://www.unicycling.com>



          "This unicycle is made all from lightweight materials. But it uses a lot of
          them." -- Cliff Cordy, describing the very heavy new prototype unicycle he
          brought on the Downieville Downhill

          Comment


          • #6
            Re: RE: A good idea?

            Originally posted by John Foss
            >
            But I really think you should start out with a three-hole crank and see how
            you like it first. It might turn out to be just fine.


            Hey, I'm a smartarse, not an engineer, a theoretician, not an artisan... However, I will gladly test them free of charge if anyone out there makes a set for me. :0)
            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

            Comment


            • #7
              Re: A good idea?

              In a message dated 6/19/02 9:43:13 PM Eastern Daylight Time,
              Mikefule.6iftn@timelimit.unicyclist.com writes:


              > Having multiple holes along the length of a crank would weaken it, but
              > it could be strengthened or widened to compensate for this. The real
              > problem, therefore, would be when riding on the shortest setting. The
              > extra bit of crank thus exposed would keep clipping your ankle bone and
              > possibly snagging your shoe lace.


              IT WOULD NOT CLIP YOUR ANKLES!!! Does the crank clip your ankles at the
              bottom of the pedal stroke? no, you have them out of the way for the entire
              pedal stroke because if you did not, you would have to move your ankles
              inward everytime the bottom of the pedal stroke came around! Think about
              what your saying sereously. Look at the actual pedal rotation as you are
              riding. The one and only problem besides strengh I can see is the
              possibility of snagging the cuffs of your jeans if you have baggy pants on.
              And only because the extended part might be short enough to slip inside as it
              comes up. But problebly not. I think you would have to try pretty damn hard
              to ever let it bother you during actual riding.

              Comment


              • #8
                Anyone got the US$ to try these?

                http://www.davincitandems.com/3hole1.jpg
                http://tinyurl.com/fu1
                [Super Gucci 130/150/170]

                from:
                http://www.davincitandems.com/comp.html
                http://tinyurl.com/fu2

                they look sure look purdy!

                These guys make tandems, which means no spiders on right crank, yay! [unists don't like spiders]

                As we have just one wheel it seems prudent to reinvent it from time to time.


                richard.

                Comment


                • #9
                  Wow! Brilliant find, Richard! That looks just like what Mikefule was describing, no? Also, I agree with Trev that the crank wouldn't clip your ankles...

                  That da Vinci Designs site is a great example of what real R&D and problem-solving and finessing of existing technology can accomplish!
                  http://www.unicyclist.com/gallery/al...y_eye_ball.gif am the http://www.unicyclist.com/gallery/al...lbun00/aac.gif in the Ointment.

                  Comment


                  • #10
                    RE: A good idea?

                    >> But... What if instead of cranks you had discs? A square or splined
                    >> socket in the middle, then a disc of radius, say, 190 mm with a smooth
                    >> edge.


                    An image popped into my mind when I first read that.

                    Suppose the discs had no pedals on them, but were rimmed with rubber (like
                    wheelchair tires). You would propel the unicycle by walking on the edges of the
                    discs, similar to wheel-walking, but faster because of the smaller diameter of
                    the discs. Could this be possible? I imagine control would be difficult.

                    - Joe


                    Comment


                    • #11
                      Not a bad idea, Joe. How about this? Lace two rubber-edged wheels onto either side of the uni rim, but instead of small, crank-length diameters, make them nearly as large as your "main" rim, just like wheel-chair drive wheels. The idea would be to do wheel-walking with your hands. Maybe you could have free-spinning footpegs at the axle ends (like on an IW). A unicycle like this might be useable by someone without total use of their legs.
                      This is not a gag. (repeat) I'm not joking here, so relax, y'all. There are all those folks with racing wheelchairs, and I even saw an article a few years back about mountain wheelchairs/mountain bikes for wheelchair users. This might work for unicycles, too. Right now, the main problem I see is that a person who can't stand would need assistance with mounting and dismounting. Of course, a constantly bent-over position on a uni would be kind of a strain on the back, too.

                      OK. That's all. Back to the original idea of drive wheels instead of cranks and pedals.
                      http://www.unicyclist.com/gallery/al...y_eye_ball.gif am the http://www.unicyclist.com/gallery/al...lbun00/aac.gif in the Ointment.

                      Comment


                      • #12
                        Re: A good idea?

                        >Not a bad idea, Joe. How about this? Lace two rubber-edged wheels onto
                        >either side of the uni rim, but instead of small, crank-length
                        >diameters, make them nearly as large as your "main" rim, just like
                        >wheel-chair drive wheels. The idea would be to do wheel-walking with
                        >your hands. Maybe you could have free-spinning footpegs at the axle
                        >ends (like on an IW). A unicycle like this -might- be useable by
                        >someone without total use of their legs.
                        >*This is not a gag.* (repeat) *I'm not joking here, so relax, y'all.*
                        >There are all those folks with racing wheelchairs, and I even saw an
                        >article a few years back about mountain wheelchairs/mountain bikes for
                        >wheelchair users. This might work for unicycles, too. Right now, the
                        >main problem I see is that a person who can't stand would need
                        >assistance with mounting and dismounting. Of course, a constantly
                        >bent-over position on a uni would be kind of a strain on the back, too.
                        >


                        Thanks. Arm-powered unicycles for the disabled... This also is interesting.
                        Maybe the wheel could be chain-driven, as on a giraffe uni, with hand-cranks
                        built onto a frame extension in front of the rider, so the person could sit
                        upright and pedal with the arms. Now we're back to cranks and pedals again.
                        This works really well with hand-cranked recumbent trikes and such. Doing this
                        on a uni would be fearsomely difficult though, I think; the main point to
                        actually doing it would be just to prove that it could be done.

                        As for my mini-rim-walking-pedaling thing, I've decided that it would work, but
                        probably wouldn't be very practical. I'm a level-2 rider with no machining or
                        welding skills, so someone other than myself will have to try it!

                        - Joe


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