Re: Winter Riding

Quoted message said:

My best winter riding was a few years ago but remains unforgettable:

http://www.trentobike.org/Countries/Switzerland/Tour_Reports/Ice_Prin...

Reading through it has made me curious.
What is the maximum speed a rider can sustain aganinst air resistance?
What is it for a car of average cross section?

Sergio
Pisa

Sergio Servadio said:

Quoted message said:

My best winter riding was a few years ago but remains unforgettable:

http://www.trentobike.org/Countries/Switzerland/Tour_Reports/Ice_Princess_1963/

Quoted message said:

Reading through it has made me curious. What is the maximum speed a
rider can sustain against air resistance? What is it for a car of
average cross section?

I didn't have a speedometer but my guess is about 15kmh if it is cold
and clean ice as it was on the Zurich lake. As ice warms it becomes
slipperier, but then the Bodensee had a rougher surface from melted
and re-frozen snow.

Jobst Brandt

Sergio Servadio said:

Quoted message said:

My best winter riding was a few years ago but remains unforgettable:

http://www.trentobike.org/Countries/Switzerland/Tour_Reports/Ice_Princess_1963/

Quoted message said:

Reading through it has made me curious. What is the maximum speed a
rider can sustain against air resistance? What is it for a car of
average cross section?

I didn't have a speedometer but my guess is about 15kmh if it is cold
and clean ice as it was on the Zurich lake. As ice warms it becomes
slipperier, but then the Bodensee had a rougher surface from melted
and re-frozen snow.

Jobst Brandt

Quoted message said:

I didn't have a speedometer but my guess is about 15kmh

Jobst,
thanks for answering though I meant something different: not on
ice, but on dry asphalt.
Anyhow, I think I had read some 20 km/h limit on your report and I was
doubting that could be correct: too high to my experience, too. A 15km/
h limit sounds a lot more reasonable.

So, the question really is the following.
What would be the maximum speed with respect to air a rider could
sustain (provided he had enough power, which he certainly does not
have)?

Sergio
Pisa

In article <4ddc2335-efe1-4afc-b876-2a81b5728f80
@s48g2000hss.googlegroups.com>, [email hidden] says...

Quoted message said:

Quoted message said:

My best winter riding was a few years ago but remains unforgettable:

http://www.trentobike.org/Countries/Switzerland/Tour_Reports/Ice_Prin...

Reading through it has made me curious.
What is the maximum speed a rider can sustain aganinst air resistance?

What is the rider's maximum sustained power output? How long is
"sustained"? Lance Armstrong has been tested to have been able to
sustain over 400 watts for 40 minutes or so, which is sufficient for
over 30 mph on an aero time trial bike. I can put out 400W for around
15 seconds; does that count as "sustained"?

--
Remove the ns_ from if replying by e-mail (but keep posts in the
newsgroups if possible).

David Kerber ns_dkerber@ns_ids.net said:

What is the rider's maximum sustained power output? How long is
"sustained"?

I guess I got wrong wording for that.
Here I go again.

To go fast at a steady pace you must overcome the air resistance, and
to put out enough power.
Given your weight and the (limited) coefficient of friction at the
tire/pavement contact area, there is an unavoidable maximum
'propelling force' that can be delivered, with no reference to the
rider's strength.
That force (in fact power output) must be provided at a steady pace to
keep at maximum speed with respect to the air.

So, for an average rider and with an average coefficient of friction,
how fast with respect to air can one fare?

Sergio
Pisa

Sergio Servadio said:

Quoted message said:

What is the rider's maximum sustained power output? How long is
"sustained"?

Quoted message said:

I guess I got wrong wording for that. Here I go again.

Quoted message said:

To go fast at a steady pace you must overcome the air resistance,
and to put out enough power.

Since the subject is riding on frozen lakes, I assume you mean riding
on ice. The Hour record for dry land has been set by many riders
under various rules, so that is not what is under discussion.

Riding on ice is an aerodynamic and traction problem in which for a
given temperature, tire inflation pressure and smoothness of ice,
limits a rider to around 15kmh. With smooth and warm ice, close to
zero degrees, traction is at a minimum and small tires highly inflated
make that worse.

In my ride, I used ~25mm cross section tubular tires at about 90psi
inflation. Although the Zurich lake was smoother than the Bodensee,
it was probably ten degrees colder as I started from ZH where the
ice was glassy smooth.

Quoted message said:

Given your weight and the (limited) coefficient of friction at the
tire/pavement contact area, there is an unavoidable maximum
'propelling force' that can be delivered, with no reference to the
rider's strength.

I don't know how pavement got into this but TT's on pavement are well
documented and should leave no doubt about speed.

Quoted message said:

That force (in fact power output) must be provided at a steady pace
to keep at maximum speed with respect to the air.

Not to worry, because wind drag goes as the square of velocity,
average smooth pedaling has little effect unless an effort is made to
ride with an irregular stroke. This is easy because the speed is so
low it requires little effort. Besides, riding frozen lakes is a
scenic adventure, not a race. So why is this an issue?

For ice racing studded fat tires on bicycles and motorcycles are
standard and bring the event back to the power limit.

Quoted message said:

So, for an average rider and with an average coefficient of
friction, how fast with respect to air can one fare?

"Coefficient of friction" where and under what conditions? As I
mentioned above, there are several parameters that affect traction.
Power is not one a consideration, speed being so low. Riding smoothly
is the principal concern and how to apply the REAR brake is another.

Jobst Brandt

Assuming a coefficient of static friction of around 0.6, and a
air-resistance coefficient of 0.172 for a rider and clothing and bicycle
weighing a total of about 80kg (175lb), and assuming 70% of the weight is
supported by the rear wheel, I get a
maximum speed around 156 km/hr (97 mph).

To achieve that speed, the power output by the (robotic?) bicyclist is
around 15000 Watts. (If heavy weights were attached to the bike near the
rear wheel, the maximum (robotic) speed would be higher.)

On dry asphalt on flat ground, static friction is not a significant limiter
to _human_ cycling speed (as Jobst implied).

Wet asphalt and climbing a very steep hill could be different.
One one stage of the "Tour de Trump" race in New York many years ago the
story I heard was that several of the European riders lost traction in a
rain-storm on a steep climb (Platte Clove Road) in the Catskill mountains.
Once they were off their bikes in the midst of the climb, they couldn't get
enough static friction to re-start, so they had to walk up the hill until
they reached a gentler section.

Ken

Sergio Servadio said:

...
So, the question really is the following.
What would be the maximum speed with respect to air a rider could
sustain (provided he had enough power, which he certainly does not
have)?

At least 130.36 kph (81.00 mph) - of course this include rolling
resistance. See the bicycle at
<http://www.varnahandcycles.com/gallery/varna_diablo_01.jpg>.

The fastest speed for a wheel driven vehicle is 737.788 kph (458.440
mph): <http://www.simonlewis.com/Don-Vesco-Turbinator.html>.

On a brushed finish concrete surface, which would provide higher
traction than a salt flat, higher speeds should be possible before air
resistance exceeds traction, assuming a long enough course (which does
not exist at this time).

--
Tom Sherman - Holstein-Friesland Bovinia
POST FREE OR DIE!

Ken Roberts said:

Assuming a coefficient of static friction of around 0.6, and a
air-resistance coefficient of 0.172 for a rider and clothing and bicycle
weighing a total of about 80kg (175lb), and assuming 70% of the weight is
supported by the rear wheel, I get a
maximum speed around 156 km/hr (97 mph)....

Is the Cd of 0.172 realistic? I have seen values quoted from Cd=0.4 for
an upright TT cyclist to Cd=0.9 for a rider on a upright "city" bike.

The calculated Cd for the Varna Diablo [1] is in the range of about 0.06
to 0.08.

[1] <http://www.varnahandcycles.com/gallery/varna_diablo_01.jpg>.

--
Tom Sherman - Holstein-Friesland Bovinia
POST FREE OR DIE!

Ken Roberts said:

Assuming a coefficient of static friction of around 0.6, and a
air-resistance coefficient of 0.172 for a rider and clothing and
bicycle weighing a total of about 80kg (175lb), and assuming 70% of
the weight is supported by the rear wheel, I get a maximum speed
around 156 km/hr (97 mph).

Quoted message said:

To achieve that speed, the power output by the (robotic?) bicyclist
is around 15000 Watts. (If heavy weights were attached to the bike
near the rear wheel, the maximum (robotic) speed would be higher.)

Quoted message said:

On dry asphalt on flat ground, static friction is not a significant
limiter to _human_ cycling speed (as Jobst implied).

Quoted message said:

Wet asphalt and climbing a very steep hill could be different. One
one stage of the "Tour de Trump" race in New York many years ago the
story I heard was that several of the European riders lost traction
in a rain-storm on a steep climb (Platte Clove Road) in the Catskill
mountains. Once they were off their bikes in the midst of the
climb, they couldn't get enough static friction to re-start, so they
had to walk up the hill until they reached a gentler section.

Even wet pavement doesn't stop a rider from riding up Filbert Street
SF with a 31.5% grade (17.5°) can be ridden in the rain, and it is not
modern asphalt, but rather hand troweled glossy concrete. That's
the same as cornering on a road with a lean angle of 17.5° traction.

Jobst Brandt

On 28 Dic, 03:00, "Ken Roberts" <[email hidden]>

Quoted message said:

Assuming a coefficient of static friction of around 0.6, and a
air-resistance coefficient of 0.172 for a rider and clothing and bicycle
weighing a total of about 80kg (175lb), and assuming 70% of the weight is
supported by the rear wheel, I get a
maximum speed around 156 km/hr (97 mph).

To achieve that speed, the power output by the (robotic?) bicyclist is
around 15000 Watts.

Thanks, that is what I meant.
By the way, between riding on ice and riding on perfectly clean
asphalt there is, of course, a rich continuum of intermediate degrees.
Never experienced a muddy mountain road?

Sergio
Pisa