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NuVInci Hub - friction
We recently built a Redline MonoCog 29" bike up for my wife with a
NuVinci hub. Other than the hub being very heavy we have the following observations in the few weeks of use she has ridden it: 1. The shifting is very smooth and we have not been able to detect slippage as would be indicated by sudden unexpected forward movement of the pedals under load. 2. The unit is totally quiet. Both under load and shifting. We also have a Hebie Chainglider and the soft noise of this and the louder sound of tires contacting pavement are the only sounds heard. 3. There seems to be an inordinate amount of friction when coasting. At first I thought the wheel bearing assembly was either defective or too tight. There is no detectable catching as would be expected in bearing issues and the local shop confirmed that the the wheel bearings were both OK and not too tight. The 3rd observation leads me to believe that the friction is inherent in the device. How bad is it? Pretty bad. When we both start at the top of a hill in a city park with my wife on her NuVinci Redline and me on my steel framed Schwinn Cruiser replete with 35 p.s.i 2x2.125 tires and knee action suspension I am able to consistently out coast her both in acceleration and distance. Not only is the Schwinn inefficient but the combined frontal area of my bike and body is larger than my wife and her bike. Has anyone else actually had experience coasting on a NuVinci equipped bike? Larry |
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#2
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NuVInci Hub - friction
Larry Webber wrote:
The 3rd observation leads me to believe that the friction is inherent in the device. How bad is it? Pretty bad. When we both start at the top of a hill in a city park with my wife on her NuVinci Redline and me on my steel framed Schwinn Cruiser replete with 35 p.s.i 2x2.125 tires and knee action suspension I am able to consistently out coast her both in acceleration and distance. Not only is the Schwinn inefficient but the combined frontal area of my bike and body is larger than my wife and her bike. I outcoast my wife when I am on a slower bike simply because I weigh so much more than she does. Try messing around with a power and speed calculator to see if you can account for the difference. My favorite one at Kreuzotter.de is down at the moment, but http://analyticcycling.com/ is still running. If there are knobbies on that 29er, there's another factor. If the rear wheel will spin with any duration at all when lifted and set in motion by hand, then it's hard to imagine the hub is exerting as much drag as you suggest. If it immediately slows to a stop, you may be onto something. Chalo |
#3
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NuVInci Hub - friction
On Tue, 15 Jul 2008 02:02:04 -0700 (PDT), Chalo
wrote: Larry Webber wrote: The 3rd observation leads me to believe that the friction is inherent in the device. How bad is it? Pretty bad. When we both start at the top of a hill in a city park with my wife on her NuVinci Redline and me on my steel framed Schwinn Cruiser replete with 35 p.s.i 2x2.125 tires and knee action suspension I am able to consistently out coast her both in acceleration and distance. Not only is the Schwinn inefficient but the combined frontal area of my bike and body is larger than my wife and her bike. I outcoast my wife when I am on a slower bike simply because I weigh so much more than she does. Try messing around with a power and speed calculator to see if you can account for the difference. My favorite one at Kreuzotter.de is down at the moment, but http://analyticcycling.com/ is still running. If there are knobbies on that 29er, there's another factor. If the rear wheel will spin with any duration at all when lifted and set in motion by hand, then it's hard to imagine the hub is exerting as much drag as you suggest. If it immediately slows to a stop, you may be onto something. Chalo Dear Chalo, Yes, the Kreuzotter calculator keeps going off line: http://www.kreuzotter.de/english/espeed.htm Drat! The Analytic site has lots of interesting calculators: http://www.analyticcycling.com/ http://www.analyticcycling.com/ForcesSpeed_Page.html http://www.analyticcycling.com/ForcesPower_Page.html The Analytic site's drawbacks are the meter-per-second results and not enough decimals to satisfy those of us who enjoy _really_ theoretical differences. Usually I head for the Austin calculator, which comes in several versions and has more fields and decimals than the Analytic site's basic calculators: http://bikecalculator.com/ The three Austin side-by-side calculators that predict speed are nice, with mph-lbs, kmh-kg, and a pure numeric that lets you try things that the helpful defaults don't allow. http://bikecalculator.com/veloMetric.html http://bikecalculator.com/veloUS.html http://bikecalculator.com/veloMetricNum.html The two Austin side-by-side calculators that predict power can save time when you want to know how much speed will produce a given power. http://bikecalculator.com/wattsMetric.html http://bikecalculator.com/wattsUS.html The six-segment Austin calculators let you fool around more easily with up to six stages with different winds, powers, grades, and positions. http://bikecalculator.com/tripMetric.html http://bikecalculator.com/tripUS.html A few other bike speed and power calculators . . . The HPVA calculator produces some graphs, roughly similiar to Analytic Cycling's sprint calculators: http://www.recumbents.com/wisil/simul/HPV_Simul.asp http://sportech.online.fr/sptc_idx.p...=spen_esy.html Downloadable with C source code http://www.grennan.com/BikePower/ More details than you can believe about atmospheric conditions and wind angles, $$$ but you can try the downloadable demo: http://www.machinehead-software.co.u...alculator.html A downloadable XLS spreadsheet calculator: http://www.whitemountainwheels.com/SpeedPower.html Cheers, Carl Fogel |
#4
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NuVInci Hub - friction
On Tue, 15 Jul 2008 02:02:04 -0700, Chalo wrote:
Larry Webber wrote: The 3rd observation leads me to believe that the friction is inherent in the device. How bad is it? Pretty bad. When we both start at the top of a hill in a city park with my wife on her NuVinci Redline and me on my steel framed Schwinn Cruiser replete with 35 p.s.i 2x2.125 tires and knee action suspension I am able to consistently out coast her both in acceleration and distance. Not only is the Schwinn inefficient but the combined frontal area of my bike and body is larger than my wife and her bike. I outcoast my wife when I am on a slower bike simply because I weigh so much more than she does. Try messing around with a power and speed calculator to see if you can account for the difference. My favorite one at Kreuzotter.de is down at the moment, but http://analyticcycling.com/ is still running. If there are knobbies on that 29er, there's another factor. If the rear wheel will spin with any duration at all when lifted and set in motion by hand, then it's hard to imagine the hub is exerting as much drag as you suggest. If it immediately slows to a stop, you may be onto something. Chalo Chalo, The Schwinn's 26x2.125 knobbues run at 35 p.s.i and the 29er does not have knobbies; it is running Schwalbe Marathon tires. Ah - the free spinning wheel with no weight test which I did not mention. The result of this is pathetic. I put the 29er on my bike stand and spun the wheel. It spins for approximately 5 seconds or so and stops as though the brake is lightly applied (it is not dragging though - confirmed by both my LBS and myself). This is what originally made me think wheel bearings except that I could detect no noise anywhere nor did rotating the tire elicit any noticeable roughness or other feeling that I associate with bad or overly tight wheel bearings. Overly tight bearings often feel "notchy" (is that a word?) to me. These don't. Thanks for the thoughtful response. Larry |
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