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

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

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

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