The zero wind tunnel option for serious cyclists

Andre Jute

Yo, Joseph, as I promised, I have published an article showing how a
cyclist can discover his power output and Cd with no tools except his
bike and a road, yet with a very high degree of accuracy. See
http://members.lycos.co.uk/fiultra/...parameters.html

HTH.

Andre Jute
http://members.lycos.co.uk/fiultra/...%20CYCLING.html

Robert Chung

On May 9, 3:47 pm, Andre Jute <fiult...@yahoo.com> wrote:

> with a very high degree of accuracy.

Hmmm. I suppose that depends on how one interprets "very high."

joseph.santaniello@gmail.com

On May 10, 12:47*am, Andre Jute <fiult...@yahoo.com> wrote:
> Yo, Joseph, as I promised, I have published an article showing how a
> cyclist can discover his power output and Cd with no tools except his
> bike and a road, yet with a very high degree of accuracy. Seehttp://members.lycos.co.uk/fiultra/BICYCLE%20TECH%20--%20basic%20cycl...
>
> HTH.
>
> Andre Jute
> *http://members.lycos.co.uk/fiultra/...%20CYCLING.html

Cyclist power is highly irregular. Chis Hoy powering to a world record
standing start kilometer puts out way more power than he could out
training on some long hill climb. He probably doesn't care what his
sustainable aerobic power is, likewise Leonardo Piepoli probably
doesn't care what his stanidng start power is. Muscle strength,
gearing, and a whole bunch of other factors make an acceleration test
for cyclists problematic.

Perhaps a more suitable way would be to use a hill of known slope and
coast down from a standing start, and measure elapsed time and if
possible speed at the end of the course.

That way you get to use the nice and consistent gravitational force
instead of the variable pedal power.

I have a constant slope hill with a clear 300m or so that would be
good for such a test. I just don't know what to do with the info I
could gather there.

Joseph

graham

<joseph.santaniello@gmail.com> wrote in message
news:16bcfb68-d67e-40bf-a5b3-10900cad2060@m73g2000hsh.googlegroups.com...
[Snip]

Perhaps a more suitable way would be to use a hill of known slope and
coast down from a standing start, and measure elapsed time and if
possible speed at the end of the course.

That way you get to use the nice and consistent gravitational force
instead of the variable pedal power.

I have a constant slope hill with a clear 300m or so that would be
good for such a test. I just don't know what to do with the info I
could gather there.

Hi Joseph,

If you really want to try this and accept the inaccuracies in your knowledge
of the slope and other inputs then I would recommend you try using the
formula below. All it does is balance the forces between those of gravity
and both wind and rolling resistance to estimate your CdA. In order to get
the best approximation you need to reach terminal velocity on the run down
the slope, i.e. you reach your maximum steady speed. The best way to do this
is to do several runs whereby your pedal up to as close to the maximum speed
you reached on your previous run before hitting the slope as this will give
you the best chance at achieving a steady terminal velocity.

CdA = (9.8 x kg x (gradient - Crr)) / (0.5 x air density x speed squared)

where:
kg is the weigth in kilogrammes of you and your bike
gradient is the fractional gradient of the slope
Crr is rolling resistance plus if you like a very small addition for hub
bearing resistance
speed is in m/s (sorry about the SI units)

To take an example from a local hill where I tried this on the drops

kg = 90 gradient = 0.1(10%) speed = 21m/s(47mph) air density = 1.23kg/m
cubed.

CdA = (9.8 x 90 x (0.1-0.006)) / (0.5 x 1.23 x 21 x 21)

CdA = 0.31

Whilst the result looks to be in the right ball park it all hinges on how
accurate the 10% figure is for the gradient of the hill. I took an average
from a digital map. Have fun and let us know your results.

Graham.

joseph.santaniello@gmail.com

On May 10, 10:59*am, "graham" <h2gt2g42-n...@yahoo.co.uk> wrote:
> <joseph.santanie...@gmail.com> wrote in message
>
> news:16bcfb68-d67e-40bf-a5b3-10900cad2060@m73g2000hsh.googlegroups.com...
> [Snip]
>
> Perhaps a more suitable way would be to use a hill of known slope and
> coast down from a standing start, and measure elapsed time and if
> possible speed at the end of the course.
>
> That way you get to use the nice and consistent gravitational force
> instead of the variable pedal power.
>
> I have a constant slope hill with a clear 300m or so that would be
> good for such a test. I just don't know what to do with the info I
> could gather there.
>
> Hi Joseph,
>
> If you really want to try this and accept the inaccuracies in your knowledge
> of the slope and other inputs then I would recommend you try using the
> formula below. All it does is balance the forces between those of gravity
> and both wind and rolling resistance to estimate your CdA. In order to get
> the best approximation you need to reach terminal velocity on the run down
> the slope, i.e. you reach your maximum steady speed. The best way to do this
> is to do several runs whereby your pedal up to as close to the maximum speed
> you reached on your previous run before hitting the slope as this will give
> you the best chance at achieving a steady terminal velocity.
>
> CdA = (9.8 x kg x (gradient - Crr)) / (0.5 x air density x speed squared)
>
> where:
> kg is the weigth in kilogrammes of you and your bike
> gradient is the fractional gradient of the slope
> Crr is rolling resistance plus if you like a very small addition for hub
> bearing resistance
> speed is in m/s (sorry about the SI units)
>
> To take an example from a local hill where I tried this on the drops
>
> kg = 90 gradient = 0.1(10%) * speed = 21m/s(47mph) air density =1.23kg/m
> cubed.
>
> CdA = (9.8 x 90 x (0.1-0.006)) / (0.5 x 1.23 x 21 x 21)
>
> CdA = 0.31
>
> Whilst the result looks to be in the right ball park it all hinges on how
> accurate the 10% figure is for the gradient of the hill. I took an average
> from a digital map. Have fun and let us know your results.
>
> Graham.

That is perfect. I am unfortunately grounded for the weekend, so I
won't be able to test until later next week.

What type of gradient? Is that distance travelled over rise?

Joseph

graham

<joseph.santaniello@gmail.com> wrote in message
news:5c686d31-9c75-49dc-9bbb-6fa6d2a8025f@b1g2000hsg.googlegroups.com...
On May 10, 10:59 am, "graham" <h2gt2g42-n...@yahoo.co.uk> wrote:
> <joseph.santanie...@gmail.com> wrote in message
>
> news:16bcfb68-d67e-40bf-a5b3-10900cad2060@m73g2000hsh.googlegroups.com...
> [Snip]
> If you really want to try this and accept the inaccuracies in your
> knowledge
> of the slope and other inputs then I would recommend you try using the
> formula below. All it does is balance the forces between those of gravity
> and both wind and rolling resistance to estimate your CdA. In order to get
> the best approximation you need to reach terminal velocity on the run down
> the slope, i.e. you reach your maximum steady speed. The best way to do
> this
> is to do several runs whereby your pedal up to as close to the maximum
> speed
> you reached on your previous run before hitting the slope as this will
> give
> you the best chance at achieving a steady terminal velocity.
>
> CdA = (9.8 x kg x (gradient - Crr)) / (0.5 x air density x speed squared)
>
> where:
> kg is the weigth in kilogrammes of you and your bike
> gradient is the fractional gradient of the slope
> Crr is rolling resistance plus if you like a very small addition for hub
> bearing resistance
> speed is in m/s (sorry about the SI units)
>
> To take an example from a local hill where I tried this on the drops
>
> kg = 90 gradient = 0.1(10%) speed = 21m/s(47mph) air density = 1.23kg/m
> cubed.
>
> CdA = (9.8 x 90 x (0.1-0.006)) / (0.5 x 1.23 x 21 x 21)
>
> CdA = 0.31
>
> Whilst the result looks to be in the right ball park it all hinges on how
> accurate the 10% figure is for the gradient of the hill. I took an average
> from a digital map. Have fun and let us know your results.
>
> Graham.

That is perfect. I am unfortunately grounded for the weekend, so I
won't be able to test until later next week.

What type of gradient? Is that distance travelled over rise?

For the above formula you want rise over horizontal distance travelled. For
modest road gradients the error is very small if you use rise over distance
travelled.

Graham.

Ron Ruff

On May 9, 4:47*pm, Andre Jute <fiult...@yahoo.com> wrote:
> Yo, Joseph, as I promised, I have published an article showing how a
> cyclist can discover his power output and Cd with no tools except his
> bike and a road, yet with a very high degree of accuracy.

Use terminal speed on a downhill to get CdA, and a climb to get power.
More accurate and simpler. The power part will always have a time
attached to it (ie 300 watts for 10 minutes).

Andre Jute

joseph.santaniello@gmail.com <joseph.santaniello@gmail.com> wrote:

> On May 10, 12:47*am, Andre Jute <fiult...@yahoo.com> wrote:
> > Yo, Joseph, as I promised, I have published an article showing how a
> > cyclist can discover his power output and Cd with no tools except his
> > bike and a road, yet with a very high degree of accuracy. See http://members.lycos.co.uk/fiultra/...%20basic%20cycl...
> >
> > HTH.
> >
> > Andre Jute
> > *http://members.lycos.co.uk/fiultra/...%20CYCLING.html
>
> Cyclist power is highly irregular. Chis Hoy powering to a world record
> standing start kilometer puts out way more power than he could out
> training on some long hill climb. He probably doesn't care what his
> sustainable aerobic power is, likewise Leonardo Piepoli probably
> doesn't care what his stanidng start power is. Muscle strength,
> gearing, and a whole bunch of other factors make an acceleration test
> for cyclists problematic.

The method I'm suggesting is exceedingly subtle, so it takes a while
to understand how it overcomes all these difficulties you raise. My
method uses repeated surplus traction measurements over your speed
range (that's those iterative acceleration readings) to measure very
closely your power *on the day*, and then, without any assumptions or
manufactured constants -- fudge factors, guesses, kludges --
approximates very closely all the other factors lumped together that
influences Cd (that's the coastdown tests) to determine your Cd.

This business of adjusting constants -- fudge factors, guestimates,
street myths, wishful thinking -- is important. Notice for instance
that I made -- it took me two days of hard thought to get there -- a
formula that entirely obviates the necessity for working with the
rolling resistance of some notional tire because I saw too wide a
range in the data you referred me to, and didn't trust the idea of a
lab test with a drum substituting for the road. Instead, I made my
formula include the actual tyres you use on the test, with a real
measurement, not a guesstimate, no matter how distinguished the
guesser. In fact, I made my formula work so that it can operate as a
check on the Cr guess!

But if you think my suggestion is too much work, then that's it;
someone else will take it up sooner or later and then we'll find out
who's right. All I can say is that my method has worked for a quarter-
century for special car builders who bought my book (they write to me
to tell me so) and before that, back into the nineteenth century, for
automobile engineers and before them railway engineers, whose methods
I adapted in the light of modern requirements and knowledge. (It isn't
like I invented anything weird: I just rearranged and reapplied widely
known physics to overcome practical difficulties in cyclist
measurements.)

> Perhaps a more suitable way would be to use a hill of known slope and
> coast down from a standing start, and measure elapsed time and if
> possible speed at the end of the course.

Sure, if that's what you want to do. It sounds a lot easier and
quicker than my method, but it only gets you one reading; even
averaging several runs gets you only one data-point (my suggestion
gets you averages on many data points -- you could for instance use
the data gathered for my method to calculate your optimum gearset). To
exclude the other factors from your reading of downhill speed to
arrive at Cd, you must then have instruments not available to you, or
make all kinds of assumptions about conditions and mechanical
reactions. My method, while more tedious, excludes these sources of
error.

> That way you get to use the nice and consistent gravitational force
> instead of the variable pedal power.

The second, coastdown part of my suggested test also uses
gravitational force. The iterative acceleration tests overcomes the
perceived problem of variable pedal power. You keep trying to solve
the problem with one big bang, by measuring top speed and trying to
deduce power from that; that is obviously a very fallible method. My
method argues that you exhibit maximum power on acceleration, and by
repeated tests over various ranges with results averaged, it will give
a more reliable final reading. What's more, my method separates the
distribution of the power between the resistances without making any
assumptions and without any fudge factors.

> I have a constant slope hill with a clear 300m or so that would be
> good for such a test. I just don't know what to do with the info I
> could gather there.

Graham has already supplied a formula

We'll find out after you do the downhill test whether the Cd you
calculate predicts your maximum speed pedaling flat out along a flat
road, which is the point of having a Cd number. One thing is for sure:
if you merely want a cafe Cd closer to the 0.3 you dream of than the
c0.5 average (for 80 per cent of racing cyclists, say) that I suspect,
you're more likely to have your wish fulfilled with the downhill
shortcut than my method!

For those who want to look it up, we're referring to my article at:

http://members.lycos.co.uk/fiultra/...parameters.html

Good luck with the test.

Andre Jute
No such thing as a free lunch -- Hayek
Never ate lunch in my life -- Armstrong

Robert Chung

On May 10, 7:20 am, Andre Jute <fiult...@yahoo.com> wrote:

> The method I'm suggesting is exceedingly subtle, so it takes a while
> to understand how it overcomes all these difficulties you raise.

I'm more interested in your claim of "a very high degree of accuracy."
Would you kindly provide an example that shows either the accuracy or
precision of your exceedingly subtle method?

joseph.santaniello@gmail.com

On May 10, 4:20*pm, Andre Jute <fiult...@yahoo.com> wrote:
> joseph.santanie...@gmail.com <joseph.santanie...@gmail.com> wrote:
> > On May 10, 12:47*am, Andre Jute <fiult...@yahoo.com> wrote:
> > > Yo, Joseph, as I promised, I have published an article showing how a
> > > cyclist can discover his power output and Cd with no tools except his
> > > bike and a road, yet with a very high degree of accuracy. Seehttp://members.lycos.co.uk/fiultra/BICYCLE%20TECH%20--%20basic%20cycl...
>
> > > HTH.
>
> > > Andre Jute
> > > *http://members.lycos.co.uk/fiultra/...%20CYCLING.html
>
> > Cyclist power is highly irregular. Chis Hoy powering to a world record
> > standing start kilometer puts out way more power than he could out
> > training on some long hill climb. He probably doesn't care what his
> > sustainable aerobic power is, likewise Leonardo Piepoli probably
> > doesn't care what his stanidng start power is. Muscle strength,
> > gearing, and a whole bunch of other factors make an acceleration test
> > for cyclists problematic.
>
> The method I'm suggesting is exceedingly subtle, so it takes a while
> to understand how it overcomes all these difficulties you raise. My
> method uses repeated surplus traction measurements over your speed
> range (that's those iterative acceleration readings) to measure very
> closely your power *on the day*, and then, without any assumptions or
> manufactured constants -- fudge factors, guesses, kludges --
> approximates very closely all the other factors lumped together that
> influences Cd (that's the coastdown tests) to determine your Cd.
>
> This business of adjusting constants -- fudge factors, guestimates,
> street myths, wishful thinking -- is important. Notice for instance
> that I made -- it took me two days of hard thought to get there -- a
> formula that entirely obviates the necessity for working with the
> rolling resistance of some notional tire because I saw too wide a
> range in the data you referred me to, and didn't trust the idea of a
> lab test with a drum substituting for the road. Instead, I made my
> formula include the actual tyres you use on the test, with a real
> measurement, not a guesstimate, no matter how distinguished the
> guesser. In fact, I made my formula work so that it can operate as a
> check on the Cr guess!
>
> But if you think my suggestion is too much work, then that's it;
> someone else will take it up sooner or later and then we'll find out
> who's right. All I can say is that my method has worked for a quarter-
> century for special car builders who bought my book (they write to me
> to tell me so) and before that, back into the nineteenth century, for
> automobile engineers and before them railway engineers, whose methods
> I adapted in the light of modern requirements and knowledge. (It isn't
> like I invented anything weird: I just rearranged and reapplied widely
> known physics to overcome practical difficulties in cyclist
> measurements.)
>
> > Perhaps a more suitable way would be to use a hill of known slope and
> > coast down from a standing start, and measure elapsed time and if
> > possible speed at the end of the course.
>
> Sure, if that's what you want to do. It sounds a lot easier and
> quicker than my method, but it only gets you one reading; even
> averaging several runs gets you only one data-point (my suggestion
> gets you averages on many data points -- you could for instance use
> the data gathered for my method to calculate your optimum gearset). To
> exclude the other factors from your reading of downhill speed to
> arrive at Cd, you must then have instruments not available to you, or
> make all kinds of assumptions about conditions and mechanical
> reactions. My method, while more tedious, excludes these sources of
> error.
>
> > That way you get to use the nice and consistent gravitational force
> > instead of the variable pedal power.
>
> The second, coastdown part of my suggested test also uses
> gravitational force. The iterative acceleration tests overcomes the
> perceived problem of variable pedal power. You keep trying to solve
> the problem with one big bang, by measuring top speed and trying to
> deduce power from that; that is obviously a very fallible method. My
> method argues that you exhibit maximum power on acceleration, and by
> repeated tests over various ranges with results averaged, it will give
> a more reliable final reading. What's more, my method separates the
> distribution of the power between the resistances without making any
> assumptions and without any fudge factors.
>
> > I have a constant slope hill with a clear 300m or so that would be
> > good for such a test. I just don't know what to do with the info I
> > could gather there.
>
> Graham has already supplied a formula
>
> We'll find out after you do the downhill test whether the Cd you
> calculate predicts your maximum speed pedaling flat out along a flat
> road, which is the point of having a Cd number. One thing is for sure:
> if you merely want a cafe Cd closer to the 0.3 you dream of than the
> c0.5 average (for 80 per cent of racing cyclists, say) that I suspect,
> you're more likely to have your wish fulfilled with the downhill
> shortcut than my method!
>
> For those who want to look it up, we're referring to my article at:
>
> http://members.lycos.co.uk/fiultra/...%20basic%20cycl...
>
> Good luck with the test.
>
> Andre Jute
> No such thing as a free lunch -- Hayek
> Never ate lunch in my life -- Armstrong

I have no doubt your method works, and I expect I will use some parts
to check the Crr values. I think the hill roll down will work well
because it uses a constant force of gravity working on the constant
mass of the rider/bike instead of the variable force avialable form
the rider.

Joseph

Tim McNamara

In article
<209d576e-56fd-4ed0-a177-6f33ff5bfad3@x19g2000prg.googlegroups.com>,
Andre Jute <fiultra1@yahoo.com> wrote:

> Yo, Joseph, as I promised, I have published an article showing how a
> cyclist can discover his power output and Cd with no tools except his
> bike and a road, yet with a very high degree of accuracy. See
> http://members.lycos.co.uk/fiultra/...20cycling%20par
> ameters.html
>
> HTH.

Not so much in terms of "publishing." You've posted a Web page is all;
that's different than publishing in the scientific sense of the word.
There's no peer review of your article, for example. This leads to some
potential confounds. Your assumptions regarding rolling resistance, for
example, are not tenable. You neglect other factors like barometric
pressure, wind speed and direction, road surface quality (retreating to
the unquantifiable "reasonably smooth road"), etc. Your only citation
is self-referential to a book you purportedly wrote. Then at the end
you totally defeat your article by saying it doesn't matter much anyway!

It's this fundamental lack of rigor in your thinking including faulty
logic, self-contradictions, etc. that undermine you every time you post
something about bicycles. You're just another Usenet blowhard.

Polymath? Please. You must have read too much John Brunner as a youth.

graham

"Andre Jute" <fiultra1@yahoo.com> wrote in message
news:85d965f3-356f-453a-a264-0308b7b2414f@k1g2000prb.googlegroups.com...
joseph.santaniello@gmail.com <joseph.santaniello@gmail.com> wrote:


Graham has already supplied a formula

We'll find out after you do the downhill test whether the Cd you
calculate predicts your maximum speed pedaling flat out along a flat
road, which is the point of having a Cd number. One thing is for sure:
if you merely want a cafe Cd closer to the 0.3 you dream of than the
c0.5 average (for 80 per cent of racing cyclists, say) that I suspect,
you're more likely to have your wish fulfilled with the downhill
shortcut than my method!

Andre,

I have read your article and would not argue with most of it. I do however
find your statement above about wish fulfillment a little harsh. I have
conducted many of these tests in the past and after a good degree of
averaging I arrived at CdA figures as used in the formula I suggested to
Joseph of 0.51 riding with my hands on the hoods, 0.34 on the drops and 0.31
on my race bike on my tri bars (I am a veteran triathlete). Clearly when
doing such tests by far the biggest uncertainty is in determining the slope
of the hill which introduces considerable scatter in the results.

If , however, I plug the 0.31 number into a power calculation for my last
40km TT in 65 mins using the other data I gave in my example to Joseph
together with an overall drive train efficiency of 95% (obviously not needed
in a coast down calc) it has me putting out around 250W which does not seem
too bad for an old timer like me. If however I were to use your figure of
0.5 (assuming you mean the same as what Joseph and I mean by a CdA of 0.3
when you speak of a Cd of 0.5) that would put me closer to 350W for over a
hour which I think would be flattering indeed.

Graham.

Andre Jute

On May 10, 3:52*pm, "joseph.santanie...@gmail.com"
<joseph.santanie...@gmail.com> wrote:
> On May 10, 4:20*pm, Andre Jute <fiult...@yahoo.com> wrote:
>
>
>
> > joseph.santanie...@gmail.com <joseph.santanie...@gmail.com> wrote:
> > > On May 10, 12:47*am, Andre Jute <fiult...@yahoo.com> wrote:
> > > > Yo, Joseph, as I promised, I have published an article showing how a
> > > > cyclist can discover his power output and Cd with no tools except his
> > > > bike and a road, yet with a very high degree of accuracy. Seehttp://members.lycos.co.uk/fiultra/BICYCLE%20TECH%20--%20basic%20cycl...
>
> > > > HTH.
>
> > > > Andre Jute
> > > > *http://members.lycos.co.uk/fiultra/...%20CYCLING.html
>
> > > Cyclist power is highly irregular. Chis Hoy powering to a world record
> > > standing start kilometer puts out way more power than he could out
> > > training on some long hill climb. He probably doesn't care what his
> > > sustainable aerobic power is, likewise Leonardo Piepoli probably
> > > doesn't care what his stanidng start power is. Muscle strength,
> > > gearing, and a whole bunch of other factors make an acceleration test
> > > for cyclists problematic.
>
> > The method I'm suggesting is exceedingly subtle, so it takes a while
> > to understand how it overcomes all these difficulties you raise. My
> > method uses repeated surplus traction measurements over your speed
> > range (that's those iterative acceleration readings) to measure very
> > closely your power *on the day*, and then, without any assumptions or
> > manufactured constants -- fudge factors, guesses, kludges --
> > approximates very closely all the other factors lumped together that
> > influences Cd (that's the coastdown tests) to determine your Cd.
>
> > This business of adjusting constants -- fudge factors, guestimates,
> > street myths, wishful thinking -- is important. Notice for instance
> > that I made -- it took me two days of hard thought to get there -- a
> > formula that entirely obviates the necessity for working with the
> > rolling resistance of some notional tire because I saw too wide a
> > range in the data you referred me to, and didn't trust the idea of a
> > lab test with a drum substituting for the road. Instead, I made my
> > formula include the actual tyres you use on the test, with a real
> > measurement, not a guesstimate, no matter how distinguished the
> > guesser. In fact, I made my formula work so that it can operate as a
> > check on the Cr guess!
>
> > But if you think my suggestion is too much work, then that's it;
> > someone else will take it up sooner or later and then we'll find out
> > who's right. All I can say is that my method has worked for a quarter-
> > century for special car builders who bought my book (they write to me
> > to tell me so) and before that, back into the nineteenth century, for
> > automobile engineers and before them railway engineers, whose methods
> > I adapted in the light of modern requirements and knowledge. (It isn't
> > like I invented anything weird: I just rearranged and reapplied widely
> > known physics to overcome practical difficulties in cyclist
> > measurements.)
>
> > > Perhaps a more suitable way would be to use a hill of known slope and
> > > coast down from a standing start, and measure elapsed time and if
> > > possible speed at the end of the course.
>
> > Sure, if that's what you want to do. It sounds a lot easier and
> > quicker than my method, but it only gets you one reading; even
> > averaging several runs gets you only one data-point (my suggestion
> > gets you averages on many data points -- you could for instance use
> > the data gathered for my method to calculate your optimum gearset). To
> > exclude the other factors from your reading of downhill speed to
> > arrive at Cd, you must then have instruments not available to you, or
> > make all kinds of assumptions about conditions and mechanical
> > reactions. My method, while more tedious, excludes these sources of
> > error.
>
> > > That way you get to use the nice and consistent gravitational force
> > > instead of the variable pedal power.
>
> > The second, coastdown part of my suggested test also uses
> > gravitational force. The iterative acceleration tests overcomes the
> > perceived problem of variable pedal power. You keep trying to solve
> > the problem with one big bang, by measuring top speed and trying to
> > deduce power from that; that is obviously a very fallible method. My
> > method argues that you exhibit maximum power on acceleration, and by
> > repeated tests over various ranges with results averaged, it will give
> > a more reliable final reading. What's more, my method separates the
> > distribution of the power between the resistances without making any
> > assumptions and without any fudge factors.
>
> > > I have a constant slope hill with a clear 300m or so that would be
> > > good for such a test. I just don't know what to do with the info I
> > > could gather there.
>
> > Graham has already supplied a formula
>
> > We'll find out after you do the downhill test whether the Cd you
> > calculate predicts your maximum speed pedaling flat out along a flat
> > road, which is the point of having a Cd number. One thing is for sure:
> > if you merely want a cafe Cd closer to the 0.3 you dream of than the
> > c0.5 average (for 80 per cent of racing cyclists, say) that I suspect,
> > you're more likely to have your wish fulfilled with the downhill
> > shortcut than my method!
>
> > For those who want to look it up, we're referring to my article at:
>
> >http://members.lycos.co.uk/fiultra/...%20basic%20cycl...
>
> > Good luck with the test.
>
> > Andre Jute
> > No such thing as a free lunch -- Hayek
> > Never ate lunch in my life -- Armstrong
>
> I have no doubt your method works, and I expect I will use some parts
> to check the Crr values. I think the hill roll down will work well
> because it uses a constant force of gravity working on the constant
> mass of the rider/bike instead of the variable force avialable form
> the rider.
>
> Joseph

There is also the question of how much precision you need for a
practical result. Graham tells in a concurrent post of impressive
empirical crosschecks on the downhill method. Good luck.

Andre Jute
http://members.lycos.co.uk/fiultra/...%20CYCLING.html

graham

"Andre Jute" <fiultra1@yahoo.com> wrote in message
news:3027e08b-58e2-4abc-85c3-0146e8d27116@i36g2000prf.googlegroups.com...
On May 10, 3:52 pm, "joseph.santanie...@gmail.com"
<joseph.santanie...@gmail.com> wrote:
> On May 10, 4:20 pm, Andre Jute <fiult...@yahoo.com> wrote:
> > joseph.santanie...@gmail.com <joseph.santanie...@gmail.com> wrote:
[Snip]

There is also the question of how much precision you need for a
practical result. Graham tells in a concurrent post of impressive
empirical crosschecks on the downhill method. Good luck.

Andre Jute

Andre,

I am not sure my results are all that impressive merely within the bounds of
what might reasonably be expected. I am sure we all realise the difficulties
of matching theory to reality when it comes to cycling on the open road but
I have found over the years of building a model of "me" both running and
cycling - never got anywhere with swimming!!! - I have managed by a process
of cross comparison and averaging to be able to get some reasonably
consistant results. This goes as far as average heart rates and times for
both cycling and running events or triathlon splits. I fully support your
approach of using a series of different test environments to emperically
derive the important variables but I also recognise there are large
uncertainty bands around any one off result. All my data has been collected
via my Garmin F301 over a period of several years. In an attempt to overcome
the Garmin's large error margin on altitute I have used a digital mapping
package to provide the altitude and hence gradient data for my modelling.

In Joseph's case then the down hill method whilst not delivering "precision"
will allow him to do comparative tests on his position on the bike or
possibly even between his wheel sets providing he does them on the same day
and can follow the same line down the hill. In short all I am saying is that
I agree with your basic premise that provided you understand the basic
physics and you do reasonably controlled tests the law of averages gets you
pretty close to the mark.

Graham.