Ceramic balls for bearings?

E Willson wrote:
According to Werehatrack "It's not difficult to remain motionless in
that circumstance" [a 60 mph headwind]

Just to pick a nit here, how would a bike be able to remain motionless?
Isn't forward motion necessary (ie wheels rotating) to raise the
necessary gyroscopic force to hold the bike upright?

It isn't gyroscopic force that keeps you upright. It's dynamically
steering (and re-steering) your center of mass back underneath yourself.
Verified (back in the 60's IIRC) by mounting counter-rotating wheel(s)
next to the front wheel so that gyroscopic force is cancelled out.

But that's not really the point of your post, so...

....did Werehatrack say anything about not putting a foot down?
(Half-smiley here)

Mark

In article .com,
says...

Question #2; If a rider at any speed, is riding into a 60 mph head
wind, why isn't he going backwards?
On a windy day, I once saw the Goodyear blimp flying backwards relative
to the ground.

Are you riding in a hurricane? If you actually experienced a 60mph
headwind you'd have a tough time going forward...

Not really, you just gear down and grind, like climbing an endless
hill, and poke along, trying to avoid debris. Been there, done it,
wouldn't do it again by choice.

--
is Joshua Putnam
http://www.phred.org/~josh/
Updated Bicycle Touring Books List:
http://www.phred.org/~josh/bike/tourbooks.html

Francesco Devittori wrote:
Jasper Janssen wrote:
In another bike group someone appears to want to buy ceramic bearing
balls. WTF? Why on earth?

Jasper

Zipp makes an uberexpensive version of some of their wheels with ceramic
ball bearings.
You can distinguish them on some pro bikes because they have white
stickers instead of red.

The $2800 Campagnolo Ultra Hyperon carbon clincher wheels use ceramic
ball bearings too.

http://www.coloradocyclist.com/commo...335&TextMode=0

On Sun, 30 Oct 2005 18:01:02 -0800, Mark Janeba
wrote:

E Willson wrote:
According to Werehatrack "It's not difficult to remain motionless in
that circumstance" [a 60 mph headwind]

Just to pick a nit here, how would a bike be able to remain motionless?
Isn't forward motion necessary (ie wheels rotating) to raise the
necessary gyroscopic force to hold the bike upright?

It isn't gyroscopic force that keeps you upright. It's dynamically
steering (and re-steering) your center of mass back underneath yourself.
Verified (back in the 60's IIRC) by mounting counter-rotating wheel(s)
next to the front wheel so that gyroscopic force is cancelled out.

But that's not really the point of your post, so...

...did Werehatrack say anything about not putting a foot down?
(Half-smiley here)

Nope. Not a word. I should know. And yes, that *was* the
implication. Bikes are on the ground. There's traction. Airspeed is
just a drag factor, not an intial motion vector.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
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Ed Willson writes:

According to Werehatrack "It's not difficult to remain motionless in
that circumstance"

Just to pick a nit here, how would a bike be able to remain
motionless? Isn't forward motion necessary (ie wheels rotating) to
raise the necessary gyroscopic force to hold the bike upright?

Two points. 60MPH winds are turbulent and unless riding on an
expansive plane, where wind direction might be relatively constant, a
rider would get blown over sideways instantly. Besides that, forward
speed is required to balance the bicycle, and there would be none in
such a wind. Gyroscopic forces have nothing to do with keeping a
bicycle upright other than steering it when riding no-hands.

http://www.sheldonbrown.com/brandt/gyro.html

Jobst Brandt

Werehatrack wrote:
On 29 Oct 2005 15:26:04 -0700, "john" wrote:

Question #2; If a rider at any speed, is riding into a 60 mph head
wind, why isn't he going backwards?

In the face of a 60mph headwind, if he's moving at all, he's doing
pretty well. It's not difficult to remain motionless in that
circumstance, but progress upwind would be very tiring and very slow,
involving the use of a very low gear. Bikes interact with the air and
the ground; even when the air is moving fast, the ground isn't. By
choosing a low enough gear ratio, forward progress is still possible.

If the wind is applying more backward force than the rider can supply
forward force, the bike goes backwards. The rider's legs would get
pushed backwards in turn, with more force than (s)he could apply to the
pedals.

In practical terms the rider would get blown off the bike long before
this happened, and if you were to get blown backwards a quick
application of brakes should be all that was required to remain
motionless up to the limits of tyre traction. By the time the wind
gets that strong, you're not in Kansas any more :-)

E Willson wrote:
According to Werehatrack "It's not difficult to remain motionless in
that circumstance"

Just to pick a nit here, how would a bike be able to remain motionless?

Yep, it's called a track stand and is a trick I overuse to a tremendous
degree at any traffic light, while talking to pedestrians, or indeed
when I'm sat on the bike and bored. In the case of a strong headwind,
you turn the bars to one side, pedal forward a bit, let the wind push
you back a bit, and use those two forces to rock back and forth in the
same manner as a tightrope walker. In the absence of a headwind you
can use a slight slope to roll you backwards for the same effect.

Google for "track stand" if that's as clear as mud...

Isn't forward motion necessary (ie wheels rotating) to raise the
necessary gyroscopic force to hold the bike upright?

It's necessary to have any steerage way to be able to correct for
wobbles, but gyro forces aren't the effect you're looking for.

Marvin Meredith writes:

Question #2; If a rider at any speed, is riding into a 60 mph head
wind, why isn't he going backwards?

In the face of a 60mph headwind, if he's moving at all, he's doing
pretty well. It's not difficult to remain motionless in that
circumstance, but progress upwind would be very tiring and very
slow, involving the use of a very low gear. Bikes interact with
the air and the ground; even when the air is moving fast, the
ground isn't. By choosing a low enough gear ratio, forward
progress is still possible.

If the wind is applying more backward force than the rider can
supply forward force, the bike goes backwards. The rider's legs
would get pushed backwards in turn, with more force than (s)he could
apply to the pedals.

In practical terms the rider would get blown off the bike long
before this happened, and if you were to get blown backwards a quick
application of brakes should be all that was required to remain
motionless up to the limits of tyre traction. By the time the wind
gets that strong, you're not in Kansas any more :-)

I have had the experience while riding up the canyon at 8000ft next to
the wall on Tioga Pass, as 100mph gusts (according to the weather
bureau) hit us in the face. The bicycle instantly goes backwards and
to keep from falling, we jumped off the back of the bicycle, legs
spread and brakes applied. We could not move until the gust subsided.
Fortunately these came infrequently but were so strong that my friend
could not open the door to a pickup truck that offered him a ride.
You can't ride a bicycle in such winds. Tire traction is not an
issue. Cars do not skid and go backwards... but they drive slowly.

Jobst Brandt

In article ,
wrote:

Ed Willson writes:

According to Werehatrack "It's not difficult to remain motionless in
that circumstance"

Just to pick a nit here, how would a bike be able to remain
motionless? Isn't forward motion necessary (ie wheels rotating) to
raise the necessary gyroscopic force to hold the bike upright?

Two points. 60MPH winds are turbulent and unless riding on an
expansive plane, where wind direction might be relatively constant, a
rider would get blown over sideways instantly. Besides that, forward
speed is required to balance the bicycle, and there would be none in
such a wind. Gyroscopic forces have nothing to do with keeping a
bicycle upright other than steering it when riding no-hands.

Yes, I have seen on television motion pictures taken of a
man in a wind tunnel. He is wearing protective gear, and
is tethered to a post. The wind speed is increased by
increments.

At 40 mph he has no difficulty remaining upright.

At 60 mph he must keep his feet wide in a martial arts
stance, and lean into the wind. He remains upright. Strong
eddies noticeably drive him in all directions.

At 80 mph he cannot remain upright. Try as he might, he
cannot keep eddies from catching him broadside, and
driving him over his balance point before he can readjust
his stance.

This is in an air stream free of turbulence except for
turbulence induced by the subject.

--
Michael Press
The rest of the world.

On Mon, 31 Oct 2005 21:43:23 GMT, Michael Press wrote:

Yes, I have seen on television motion pictures taken of a
man in a wind tunnel. He is wearing protective gear, and
is tethered to a post. The wind speed is increased by
increments.

At 40 mph he has no difficulty remaining upright.

At 60 mph he must keep his feet wide in a martial arts
stance, and lean into the wind. He remains upright. Strong
eddies noticeably drive him in all directions.

At 80 mph he cannot remain upright. Try as he might, he
cannot keep eddies from catching him broadside, and
driving him over his balance point before he can readjust
his stance.

This is in an air stream free of turbulence except for
turbulence induced by the subject.

This matches reasonably well (but not perfectly) with my own
experiences during hurricanes and bad squalls; at 60mph, the wind
effects required using quite a bit of care in order to move around,
but absent a strong gust, it was controllable and manageable. At
somewhere around 75 to 90 (hard to say precisely what the windspeed
was at my location) it became very difficult to deal with, and at 100
it was clear that there was no way that a human would remain erect
unless tethered.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.