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Reverse K-drive |
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Balor
Visitor (new) Joined: 25 January 2017 Status: Offline Points: 154 |
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Yea, that is exactly what I've meant by the way. Reversed rotation K-drive should be like an 'oval ring on steroids' and oval rings shine at higher cadences. Gears also a bit more efficient than chains - provided you keep them adequately lubricated (somehow)... preferably made from self-lubricating material. Maybe in a few years I might have a prototype 3D printed from some allow to test my theory :) Progress marches on... Short cranks do feel nice and comfortable to me. How short are they? It took me a while to adapt to 140mm ones (I am nearly 6' tall though). Anyone tried adapting to even shorter ones? 12? 10? 6? :)
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Balor
Visitor (new) Joined: 25 January 2017 Status: Offline Points: 154 |
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Btw... a thought regarding short cranks. The less your legs are bent during POWER phase the the more glutes are emphasized and less - quads. The gluteus maximus moment arm for hip extension indicates that it is a key hip extensor in the sagittal plane, and decreases with increasing hip flexion angle. The gluteus maximus is therefore most effective when the hip is near full extension, implying that exercises that produce peak contractions at this point will be most beneficial for its development. Ok, google, what variables shift your 'leg angle' to more open during power stroke? BB height, seat recline and CRANK LENGTH. Hm hm hm. It also explains why bridging works, btw!
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RoyMacdonald
BHPC Member Joined: 09 March 2007 Location: Rye East Sussex Status: Offline Points: 960 |
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Ian Sims of Greenspeed tested a range found that at shorter than 110 mm power loss started to occur. I used to be 5' 8" but now I'm 5' 5" however my legs are the same length they were 25 years ago because I've never had to adjust my seat position. Makes me more aero though. So it's leg length thats the determing factor for comfort I think. I have bikes with lengths of 140 and 150 and 190. The K-drive has a 185 mm effective length crank. Miles designed the K-drive to be as flat as possible to get it to fit inside the fairing. Aerodynamics is everything. I just wish it felt more comfortable to use for me. (That's why I only did 50k on it) I never had any mechanical issues with the K-drive in that time. I replaced the chains on it occasionally. Start of every race season I think. I did have to fit new bearings in the Sturmey Archer hub as they started to fail. Maybe they did not design them to do 70mph. Roy
Edited by RoyMacdonald - 19 January 2019 at 12:04am |
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Balor
Visitor (new) Joined: 25 January 2017 Status: Offline Points: 154 |
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Found Kingsbury homepage... things are even more interesting!
http://www.kingcycle.co.uk/page11.htm As for 'reverse K-drive', it seems that I was wrong and simply reversing rotation of secondary cranks will result in complex 'looping' motions, not merely reversed oval. :( Oh well.
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