Roller racing quantified

[carlfogel@comcast.net]

http://www.dailymail.co.uk/sciencetech/article-1232743/How-cyclists-does-power-hairdryer-The-answers-18-family-discovered-unique-TV-experiment.html

[Norman]

On Dec 3, 8:03*pm, wrote:
> http://www.dailymail.co.uk/sciencetech/article-1232743/How-cyclists-d...

A seriously powerful hair dryer is about 1800W, so
those cyclists were either only able to generate abt
100W each, or the conversion methods used were
terrifically inefficient.

It's a good thing our primitive ancestors didn't think
the only way to heat water was by rubbing their legs
together vigorously.

[pm]

On Dec 3, 6:21*pm, Norman > wrote:
> On Dec 3, 8:03*pm, wrote:
>
> >http://www.dailymail.co.uk/sciencetech/article-1232743/How-cyclists-d...
>
> A seriously powerful hair dryer is about 1800W, so
> those cyclists were either only able to generate abt
> 100W each, or the conversion methods used were
> terrifically inefficient.
>
> It's a good thing our primitive ancestors didn't think
> the only way to heat water was by rubbing their legs
> together vigorously.

it's pretty well known that a person on a stationary bicycle will not
produce nearly as much power as a person on a motile bike, as on a
stationary bike there's no wind to keep the body cooled within
operating temperature.

OTOH, I liked this video:

http://s168.photobucket.com/albums/u200/Vankoff/?action=view&current=GeneratorRunning.flv
source:
http://www.candlepowerforums.com/vb/showthread.php?p=3177070

Starting a flourescent tube and keeping it lit seems like it would
take a bit of skill.

[bjw@mambo.ucolick.org]

On Dec 3, 7:21*pm, Norman > wrote:
> On Dec 3, 8:03*pm, wrote:
>
> >http://www.dailymail.co.uk/sciencetech/article-1232743/How-cyclists-d...
>
> A seriously powerful hair dryer is about 1800W, so
> those cyclists were either only able to generate abt
> 100W each, or the conversion methods used were
> terrifically inefficient.
>
> It's a good thing our primitive ancestors didn't think
> the only way to heat water was by rubbing their legs
> together vigorously.

Generators and small dynamos aren't 100% efficient.
Maybe better than 50% though. I don't know any details
of how the generation was done.

I once calculated that during my relatively strenuous
commute (at the time, it gained 800 ft elevation), I
produced only enough power to run my toaster twice.
It is sobering.

Ben

[Chalo]

John Dacey wrote:
>
> On the other hand, this guy might singelhandedly provide enough juice
> for an arc welder:http://www.youtube.com/watch?v=sVbwngNoHm0

I know you didn't actually mean that, but can't help noting
something: That guy isn't making any power at all. He's expending a
tremendous amount of energy to spin up to that speed, but all that
energy is used reciprocating his legs, spinning bearings, rolling
tires, and entraining a certain amount of air around the wheels and
rollers. There is no load on the rollers and thus no work output.

Thus the video is a great illustration of why a needlessly high
cadence is a bad idea. You do a lot of work just maintaining the high
cadence instead of getting down the road.

Chalo

[z]

Chalo wrote:
> John Dacey wrote:
>> On the other hand, this guy might singelhandedly provide enough juice
>> for an arc welder:http://www.youtube.com/watch?v=sVbwngNoHm0
>
> I know you didn't actually mean that, but can't help noting
> something: That guy isn't making any power at all. He's expending a
> tremendous amount of energy to spin up to that speed, but all that
> energy is used reciprocating his legs, spinning bearings, rolling
> tires, and entraining a certain amount of air around the wheels and
> rollers. There is no load on the rollers and thus no work output.
>
> Thus the video is a great illustration of why a needlessly high
> cadence is a bad idea. You do a lot of work just maintaining the high
> cadence instead of getting down the road.
>
> Chalo

Stop applying everyone else to your own narrow range of circumstances.

[dustoyevsky@mac.com]

On Dec 4, 2:28*am, Chalo > wrote:
> John Dacey wrote:
>
> > On the other hand, this guy might singelhandedly provide enough juice
> > for an arc welder:http://www.youtube.com/watch?v=sVbwngNoHm0
>
> I know you didn't actually mean that, but can't help noting
> something: *That guy isn't making any power at all. *He's expending a
> tremendous amount of energy to spin up to that speed, but all that
> energy is used reciprocating his legs, spinning bearings, rolling
> tires, and entraining a certain amount of air around the wheels and
> rollers. *There is no load on the rollers and thus no work output.
>
> Thus the video is a great illustration of why a needlessly high
> cadence is a bad idea. *You do a lot of work just maintaining the high
> cadence instead of getting down the road.

Jeeze, Chalo, hop on a road bike on rollers and give us an hour at 100
rpm in a 58x12 and tell us you're not working.

That looks like a Spin Class at a Keirin school. They get on down the
road in fair order when it's time to do so.
Just sayin', that silly spinning is going on for a reason (or reasons)
I have some understanding of through practice,

There are those who "disagree" and they are free to do as they wish
with little-to-no comment from me, no problem.
--D-y

[Chalo]

dustoyevsky wrote:
>
> Chalo wrote:
> >
> > John Dacey wrote:
> > >
> > > On the other hand, this guy might singelhandedly provide enough juice
> > > for an arc welder:http://www.youtube.com/watch?v=sVbwngNoHm0
> >
> > [...] Thus the video is a great illustration of why a needlessly high
> > cadence is a bad idea. You do a lot of work just maintaining the high
> > cadence instead of getting down the road.
>
> Jeeze, Chalo, hop on a road bike on rollers and give us an hour at 100
> rpm in a 58x12 and tell us you're not working.

The point is, I'd be doing the same amount of physical work (power
output) at 200 rpm, 100 rpm, or 50 rpm-- which is to say, nothing. In
any case, all the pedal power is spent on spinning, not propulsion (as
MV^2). But the power input is beyond proportional to rpm-- it takes a
lot more than twice as much input power to spin at 100 than to spin at
50, and a lot more than twice as much power to spin at 200 rather than
100.

My point is only that within certain limits, the most efficient rpm is
close to the lowest rpm that allows you to sustain a given speed.
That's what gives you the best ratio of power out to power in. That's
not the only measure of performance, surely, but it is what bikes are
for.

Chalo

[dustoyevsky@mac.com]

On Dec 5, 1:19*pm, Chalo > wrote:
> dustoyevsky wrote:
>
> > Chalo wrote:
>
> > > John Dacey wrote:
>
> > > > On the other hand, this guy might singelhandedly provide enough juice
> > > > for an arc welder:http://www.youtube.com/watch?v=sVbwngNoHm0
>
> > > [...] Thus the video is a great illustration of why a needlessly high
> > > cadence is a bad idea. *You do a lot of work just maintaining the high
> > > cadence instead of getting down the road.
>
> > Jeeze, Chalo, hop on a road bike on rollers and give us an hour at 100
> > rpm in a 58x12 and tell us you're not working.
>
> The point is, I'd be doing the same amount of physical work (power
> output) at 200 rpm, 100 rpm, or 50 rpm-- which is to say, nothing.

It's not "nothing", and it feels a lot different at different RPM's.

>*In
> any case, all the pedal power is spent on spinning, not propulsion (as
> MV^2). *But the power input is beyond proportional to rpm-- it takes a
> lot more than twice as much input power to spin at 100 than to spin at
> 50, and a lot more than twice as much power to spin at 200 rather than
> 100.

Judging by oxygen consumption, I'd say you're right.

> My point is only that within certain limits, the most efficient rpm is
> close to the lowest rpm that allows you to sustain a given speed.
> That's what gives you the best ratio of power out to power in. *That's
> not the only measure of performance, surely, but it is what bikes are
> for.

The conditioning work seen in that video clip changes that, in my
understanding.
Indeed, "we are not diesel engines".
--D-y

[bjw@mambo.ucolick.org]

On Dec 5, 12:19*pm, Chalo > wrote:
>
> The point is, I'd be doing the same amount of physical work (power
> output) at 200 rpm, 100 rpm, or 50 rpm-- which is to say, nothing. *In
> any case, all the pedal power is spent on spinning, not propulsion (as
> MV^2). *But the power input is beyond proportional to rpm-- it takes a
> lot more than twice as much input power to spin at 100 than to spin at
> 50, and a lot more than twice as much power to spin at 200 rather than
> 100.
>
> My point is only that within certain limits, the most efficient rpm is
> close to the lowest rpm that allows you to sustain a given speed.
> That's what gives you the best ratio of power out to power in. *That's
> not the only measure of performance, surely, but it is what bikes are
> for.
>

This has been discussed at length in r.b.racing and the
issue is that it all depends on what the meaning of the
word "efficiency" is. Search for posts by Andy Coggan with
"efficiency", for example

http://groups.google.com/group/rec.bicycles.racing/search?hl=en&group=rec.bicycles.racing&q=coggan+efficiency+fatigue&qt_g=Search+this+group

http://groups.google.com/group/rec.bicycles.racing/msg/214079218ccc7875?hl=en

There have been many lab experiments on this.

If you define "efficiency" as the ratio of power output to
oxygen uptake over modest time durations, then efficiency is
indeed higher at low cadences, and highest at cadences
that are significantly lower than the cadence self-selected
by average recreational cyclist test subjects. Which might
makes us wonder, why do we self-select for somewhat
higher cadence? (I mean 80-90 or so, not some crazy high
cadence that is of use to trackies and people who write
training articles for Bicycling!! magazine.)

*However*, the key is time duration. If the subjects are tested
to fatigue (at constant wattage IIRC), then they can pedal
significantly longer at higher cadences that are closer to
the self-selected range. At constant wattage, really low
cadences require higher pedal force per stroke, and this
leads to earlier muscle fatigue.

The bottom line is, as one rbr poster likes to tease us with,
"Cadence is a red herring." Understanding this oxygen usage
vs muscular fatigue tradeoff is useful, but fiddling with cadence,
either higher or lower, is not a magic key to riding faster longer.
Self-selected cadence in trained cyclists is reasonable, which
is sort of saying that the body knew what it was doing all along.

Ben

[dustoyevsky@mac.com]

On Dec 5, 11:42*pm, " >
wrote:
> *If the subjects are tested
> to fatigue (at constant wattage IIRC), then they can pedal
> significantly longer at higher cadences that are closer to
> the self-selected range.

Bingo. "Real world", as opposed to trying to prove a point through
"experiment" or citing experiment to prove a belief-- or prejudice.

> *At constant wattage, really low
> cadences require higher pedal force per stroke, and this
> leads to earlier muscle fatigue.

That's what it's all about, that "souplesse" thing, is going further/
faster for a "given effort".

> The bottom line is, as one rbr poster likes to tease us with,
> "Cadence is a red herring." *Understanding this oxygen usage
> vs muscular fatigue tradeoff is useful, but fiddling with cadence,
> either higher or lower, is not a magic key to riding faster longer.
> Self-selected cadence in trained cyclists is reasonable, which
> is sort of saying that the body knew what it was doing all along.

Spinning enables a higher self-selected cadence. The keirin riders in
the clip linked to are not "fiddling".
--D-y