Announcement

Collapse
No announcement yet.

Why am I not faster with shorter cranks? (Oh no, not crank length again...)

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #16
    Well, maybe my thoughts about unicyclist size are way off. I, too, have a 36" inseam; so, it may be possible for me to go 110s or even 100s on a 36". Maybe I should open up to the idea. Thanks.

    Comment


    • #17
      I have done a lot of crank swapping on a lot of wheels over the years and my general preferences have slowly been getting shorter.

      My first unicycle had a trials wheel and 150mm cranks. I tried a friends who had 140s and they felt too small and I had less control.

      Now 135/137 is one of my favourite sizes for technical MUni on a 26. I don't know when that happened. I actually thought I was riding a set I drilled to 145mm until I broke one crank and compared it to a KH that was marked. The cranks I was using were drilled to 135mm. 145 or 150 used to be my favourite length for MUni and before that I was 160 all the way. 170s always felt a bit long.

      I can still go plenty fast with the longer cranks but find it easier and less tiring with the shorter cranks.
      Last edited by saskatchewanian; 2012-01-07, 07:02 AM.
      My friends, love is better than anger. Hope is better than fear. Optimism is better than despair. So let us be loving, hopeful and optimistic. And we’ll change the world. - Jack Layton

      Comment


      • #18
        Originally posted by saskatchewanian View Post
        I have done a lot of crank swapping on a lot of wheels over the years and my general preferences have slowly been getting shorter.

        I can still go plenty fast with the longer cranks but find it easier and less tiring with the shorter cranks.
        I agree.

        I keep going to shorter cranks. I really only notice the difference after I have lots of time on the shorter length and go back to a longer length. The first few rides "seem" slow on the long cranks. When I attack a steep climb I normally just power up on short cranks but the long cranks bog me down into a slower cadence. (I've been told strength and endurace gained from traing are crank length specific until adapted with new training.)

        If I time short rides for comparison it works out close to the same. If the rides are several hours long then it's more fatiguing for me as crank length increases.

        A little off subject but I've found that longer cranks (150 or longer) contribute to my knees going bad on long endurance rides. When I did my 200+ mile day I ended up switching from 150 to 125 at 120 miles and wishing I had 110 on the KH 36 Schlumpf.

        Doing 29 muni now I normally would not use anything longer than 137 unless it's just all mud. 29 on road I really like 89s. I can climb 16% on the 89s. 20% for short distances.

        JM
        You cannot teach a man anything, you can only help him find it within himself....



        ...

        Comment


        • #19
          Originally posted by Twente Muni View Post
          @ mbalmer: you say you ride 16 km/h maximum. On your guni and 36er also ?
          Do you have them just for the comfort of slower pedaling instead of speed ?

          I can't outrun a UPD if I go faster. I also don't like to spin fast. On a bicycle I ride in a higher gear to spin at a more relaxed pace, though I'll go much faster than on a unicycle.

          Comment


          • #20
            Spin rate and wheel size determine speed.

            Why aren't you going faster with shorter cranks? Because you didn't increase your wheel size or spin rate.

            If you can spin faster, that's one way to go faster, though I have not found shorter cranks increase my spin rate so much as smooth out my spin and make for more comfort while riding.

            There is a limit to how short you can go and still maintain enough torque for climbing and control when maneuvering.

            Like Eric, my cranks have gotten shorter over time, but I still find a 29 x 2.4/150 is a good combo for XC and a 26 x 2.4/150 is a good combo for tech muni. I could certainly ride a 135/140 on both my munis, esp on the 26, but they don't climb as well and they lose something when I need to maneuver around obstacles when going slow.

            I tried my son's Oregon with 170's, it'd been a while since I rode a long crank, and it was akward. I found that the muni wanted to sway side to side requiring more corrections, but the power was amazing and I could ride slower up hills.

            Maybe you don't need more speed so much as you need harder terrain? I find that easy trails are easy, so I naturally want to go faster but I can only go so fast, so by riding harder trails the terrain dictates my speed and lime Mbalmer I only want to go as fast as I can safely dismount (UPD).

            FYI, me thinks you are suffering from MTB Syndrome

            You could always buy my 26Guni.
            Last edited by Nurse Ben; 2012-01-09, 02:33 PM.
            I dream of hamsters and elderberries

            Comment


            • #21
              Originally posted by Nurse Ben View Post
              Spin rate and wheel size determine speed.

              FYI, me thinks you are suffering from MTB Syndrome

              You could always buy my 26Guni.
              Yes I still have MTB syndrome, I'm unicycling only for 2 years now. MTB very rarely now. Should have started unicycling way earlier, so much more fun.

              So Ben, don't you like to Guni? Can you tell me why, I highly appreciate your opinion. Last week I have read the entire Schlumpf general discussion thread, because the idea of a Guni looks very good to me. a few things are holding me back.
              1) price, € 1200, hub only. I would need a wheel, a KH frame and seatpost.
              2) Reliability, should be better at the moment. I will wait how long Terry's hub will last.
              3) Slop, is it annoying? I used to do miles long wheelies on my fixed gear MTB, but I hating the slop in the chain.
              4) The Hub puts a torque on the frame in high gear, on the bearing holder. Do you feel that while riding?
              5) I want to be a better unicyclist before I reward myself with a Schlumph hub.
              6) The anger of my beloved wife
              7) bla bla bla
              36" KH Muni, 2.25" Racing Ralph, 137/165 Moments
              29" Qu-ax MUni, 2.4" Racing Ralph, 145mm quax alu
              24" Qu-ax MUni, 3.0" Gazza, 145 Qu-ax alu.
              26" KH Guni, 2.25" Rocket Ron, zero, T bar

              Comment


              • #22
                Hr, somehow i recognize those thoughts. Been looking at the Schlumpf hub for some while too.

                Greetings

                Byc
                Wichtig ist nur:
                "Beim Auffallen nicht Umfallen,
                beim Umfallen nicht Auffallen."

                Qu-Ax Luxus 20"
                Qu-Ax Luxus 24"
                Qu-Ax/Nimbus 26" Muni
                KH 36" Muni

                Comment


                • #23
                  Originally posted by Byc View Post
                  Hr, somehow i recognize those thoughts. Been looking at the Schlumpf hub for some while too.

                  Greetings

                  Byc
                  Now I have two speeds, to bad they are divided over two unicycles. A 24x3.0 and a 29x2.4. Now have to decide before my ride: do I want to go technical and slow, or do or want to go faster on easier terrain.

                  It would be so nice to combine two speeds in one unicycle.
                  Or I could ride one uni, and strap the other one on my back

                  And back to topic: If shorter cranks don't give me much more speed, a Schlumph hub will. (If I don't get scared over 20 km/h)

                  Or maybe a 36er would be a nice challenge for offroad rides.
                  Like ben said: If your RPM does not get higher, then the wheelsize must be bigger.
                  36" KH Muni, 2.25" Racing Ralph, 137/165 Moments
                  29" Qu-ax MUni, 2.4" Racing Ralph, 145mm quax alu
                  24" Qu-ax MUni, 3.0" Gazza, 145 Qu-ax alu.
                  26" KH Guni, 2.25" Rocket Ron, zero, T bar

                  Comment


                  • #24
                    So Ben, don't you like to Guni? Can you tell me why, I highly appreciate your opinion. Last week I have read the entire Schlumpf general discussion thread, because the idea of a Guni looks very good to me. a few things are holding me back.
                    1) price, € 1200, hub only. I would need a wheel, a KH frame and seatpost.

                    Cost is high, but not relative to an equivallent high end bike, not to mention you are getting a swiss watch of the biking world with a five year warranty.

                    2) Reliability, should be better at the moment. I will wait how long Terry's hub will last.

                    I don't think this is a big problem anymore, fewer failures reported lately.

                    3) Slop, is it annoying? I used to do miles long wheelies on my fixed gear MTB, but I hating the slop in the chain.

                    Slop is not noticeable to me and I'm the original "princess and the pea"

                    4) The Hub puts a torque on the frame in high gear, on the bearing holder. Do you feel that while riding?

                    No, the torque does not affect the frame or bearing holder.

                    5) I want to be a better unicyclist before I reward myself with a Schlumph hub.

                    Yeah, but do you feel the same about all sports, i.e beat your self down with the equipment?

                    6) The anger of my beloved wife

                    Unconditional love and lots of "honey do's"

                    7) bla bla bla
                    Okay, so if you have read all the guni posts, you probably know that I'm not a huge guni fan. Granted, it is an amazing piece of engineering and it is the only way to gear up a uni, BUT it has a singular downfall:

                    The 50% step is too tall.

                    I find that riding a guni off road is a bear in high gear. I don't know about a 24 or 29, but on my 26guni the high gear is really only usable for smooth terrain and even then it is hard to ride. Know this: Riding a geared up guni is much, much harder than riding an equivallent big wheel.

                    Is it a reward? Hmmm, hard to say, I guess if you have the cash and already own a range of unis, including a 36er, then sure it's part of a complete uni quiver, but for me it is the least ridden uni I own.

                    I think the benefit of a guni is very terrain specific, so where I live (Appalachia) the terrain is very up and down, rarely level, and very rooty and rocky, so I have very little "space" for high gear use. In contrast, Napalm lives where it is very level and relatively smooth (Australia), so he gets a lot of high gear use.

                    If you like to ride trails on a 36er and wish it were more agile, then a 26 guni would probably work well for you. If you can't ride a 36er on the trails you enjoy, then you probably won't get much use from a guni.

                    Try riding the 29er more with short cranks and work up your spin rate, maybe add a handle and try a different tire. I find that I can go plenty fast on my 29er unless it's on a road in which case it is slow like a unicycle
                    Last edited by Nurse Ben; 2012-01-09, 09:48 PM.
                    I dream of hamsters and elderberries

                    Comment


                    • #25
                      It's hard to judge Guni riding based on opinion. I am like Ben and am not comfortable in high gear off road. I like the Guni on the road. I can climb steep hills in low gears and descend/cruise around in high gear. BUT, there are plenty of people who like bombing down some trail in high gear . It depends on the type of rider you are.

                      Comment


                      • #26
                        It's hard to judge Guni riding based on opinion.
                        Yup, it really is something you should try before you buy, but then again some folks who bought one and didn't take to it initially, have come to like their guni over time.

                        I do like mine at times, but it's frustrating to me that it doesn't have more utility for my needs. It cost so much and gets ridden so little, seems wasteful.

                        If it doesn't sell, I'll hold onto it and plan to use it in the summers when I ride out West and for when we move West in 2014
                        Last edited by Nurse Ben; 2012-01-10, 02:23 AM.
                        I dream of hamsters and elderberries

                        Comment


                        • #27
                          I think that riding fast on short cranks can probably benefit from learning to coast--if you're into that kind of thing. If you can coast then you probably won't have much trouble with the lessened torque available for quick corrections.

                          I've never had trouble with short cranks. First time I tried short cranks(on a mid-size wheel), all I could think about was how awesome it felt to be able to sustain such high speeds. I already had a solid base in freestyle by that time, however.
                          Last edited by Heretical Rants; 2012-01-10, 08:30 AM.

                          Comment


                          • #28
                            Old but very interesting thread. When I try to pedal very fast on my 20er with 127mm cranks, even though theoretically the maximum cadence is the same for a given travelling speed, in practice there are other factors at play:

                            1. When pedalling, our quadriceps do most of the work by pushing down on the pedals. Due to the nature of physics, a near fully extended leg can push much harder than one that's bent at the knee at, say 90°, that's why we adjust our saddles so that the leg is almost fully stretched on the down stroke. Shorter cranks reduce the overall up-down range of motion of our legs which means our legs can remain closer to the near fully extended position throughout the entire crank turn. This translates to more efficiency.

                            2. If our legs were mass-less then crank length would be less of an issue. Unfortunately legs have quite a lot of mass and pedalling means the mass must move up and down. If one joule is the amount of energy expended when a force of one newton causes a displacement of one metre, a two metre displacement would require twice the energy. Longer cranks = longer greater displacement. Not only that, for a given cadence the legs will need to accelerate and decelerate more rapidly because they must swipe through the same angle in the same amount of time, which involves greater forces, again increasing the energy expenditure.

                            That's what I can remember from high school physics anyway.
                            Teliang 19" | KH 27.5"

                            Comment


                            • #29
                              I recently changed to 140mm cranks and always rode 150mm. I dont yet know about speed but on my 32" it feels more stable. The wheel doesnt sway so much. Mostle have to get used to mounting. Otherwise i should be able to go a little faster. Will try it this weekend

                              Comment


                              • #30
                                Originally posted by Scoox View Post
                                Old but very interesting thread. When I try to pedal very fast on my 20er with 127mm cranks, even though theoretically the maximum cadence is the same for a given travelling speed, in practice there are other factors at play:
                                It's not the "maximum cadence" for a travelling speed, it's the "cadence" that is the same, unless you are riding a freewheel. The "maximum cadence" which determines your maximum speed is determined by crank size.
                                Originally posted by Scoox View Post
                                1. When pedalling, our quadriceps do most of the work by pushing down on the pedals. Due to the nature of physics, a near fully extended leg can push much harder than one that's bent at the knee at, say 90°, that's why we adjust our saddles so that the leg is almost fully stretched on the down stroke. Shorter cranks reduce the overall up-down range of motion of our legs which means our legs can remain closer to the near fully extended position throughout the entire crank turn. This translates to more efficiency.
                                While it is true that we can exert the most amount of force with our legs close to extended (160ish°), staying close to that range doesn't automatically lead to more efficiency. Muscle efficiency depends largely on relative load (how much of the maximum force you are capable of exerting are you exerting), and the velocity it's shortening at, as far as I can tell. This may or may not lead to shorter cranks being more efficient in many cases, but I know way to little about our biomechanics to tell.
                                Originally posted by Scoox View Post
                                2. If our legs were mass-less then crank length would be less of an issue. Unfortunately legs have quite a lot of mass and pedalling means the mass must move up and down. If one joule is the amount of energy expended when a force of one newton causes a displacement of one metre, a two metre displacement would require twice the energy. Longer cranks = longer greater displacement. Not only that, for a given cadence the legs will need to accelerate and decelerate more rapidly because they must swipe through the [...][a larger] angle in the same amount of time, which [means greater speeds, that necessitate larger acceleration, which] involves greater forces, [] increasing the energy expenditure.
                                I grayed out the not so great part of your statement.. To accelerate a unicycle (or maintain a certain speed) we need a certain amount of energy, no matter which crank size. The shorter path and the extra force needed at the pedal with shorter cranks cancel each other out. The acceleration part is probably mostly accurate though, except your typo, and skipping a few steps of explanation.

                                Our max speed on a certain unicycle is limited by the speed a muscle can contract. Shorter cranks = more speed capability, with a downside of less control. It's that simple. The lack of gearing makes it impossible for us to really think about efficiency.
                                In the beginning the Universe was created. This has made a lot of people very angry and been widely regarded as a bad move. -Douglas Adams.

                                Comment

                                Working...
                                X