Power Profiling -- good stuff
Mark Fennell
Profiling" at www.cyclingpeaks.com containing an Excel table of W/kg
for different duration efforts and a range of performance levels going
from world champions down to untrained athletes. IMHO, this is really
good stuff for anyone who wants to be at all analytical or objective
about his/her training and performance. That said, I have a number of
questions and comments for Andy or any other of the power gurus and
advocates. (Warning: this may turn out to be a long post so either
move on now, or go read his article if you haven't already.)
First, it seems like the way you bracketed the groups is natural, and
in my admittedly subjective experience and observation, the overlap is
reasonable. By that I mean, for example, the "lower half" of the cat
1's is comparable to the "upper half" of the 2's, etc., at least to
first order. I'm curious how confident you are in the values in the
table between "World Champ" and "Untrained". I ask for two reasons.
For one, my own profile doesn't fit the way I would expect. And
second, the values in the table progress linearly (as you move through
ability levels) and the brackets cover a constant, wide range. As we
all know, assume a relationship is linear if we don't have enough data
or insights that say it should be otherwise!
In particular, I'm wondering if you might be a little bit low with the
"5 min" and "20 min" W/kg values, at least in the Div. III pro through
cat 3 range, and perhaps a little high for the "5 s" and "1 min"
values. For example, I am pretty confident that the best cat 1
climbers can put out more than 5.19 W/kg over a 20-minute effort.
My own profile, at age 42, is as follows:
Duration: W/kg:
----------------------
20 minute: 4.7
5 minute: 5.1
1 minute: 8.1
5 second: 13-15
My values were about 10% higher when I last raced seriously, about 12
years ago. I did win a couple of P12 road races then, but I was
certainly not at the level that the table indicates for the 20-minute
level. OTOH, I'm pretty sure I could sprint better than the average
cat 4, which is where the table puts me for the 5-second test.
BTW, please don't think I'm nit-picking the article and the table. I
think the information is great and really useful. I just think you
might like hearing about some other data points!
Another question or two...
It would be fascinating to see some real profiles for a variety of
ability levels and specialties (and all-arounders). Does anyone have
some profiles they can share? My profile shows decent lactate
tolerance and VO2Max but pretty weak short-term power. I'm curious, is
there really anyone that is well-trained and has a flat profile?
Also, W/kg is clearly a good indicator of climbing performance. But
for time trialing, it isn't that strongly related is it? In my case,
my 20-minute W/kg suggest I should be in the cat 1-2 range which I
think is reasonable for climbing, but, trust me, it's way off for time
trialing. In your experience, should someone be able to work on their
aero position, etc. so that their climbing and tt'ing are comparable,
at least relative to other riders in the same category? In other
words, is body mass a good indicator for the aerodynamic drag one
should be able to achieve? I wouldn't think so, but the power-profile
article and table sort of suggest that one's climbing and tt'ing can
be similarly categorized based on mass alone.
Anyway, thanks again for sharing your great information and insights.
Mark Fennell
Tom Kunich
between poewr output and some other measurement such as TT speed.
"Mark Fennell" <marco_f...@yahoo.com> wrote in message
news:705a928b.0308...@posting.google.com...
warren
Kunich <tku...@earthlink.net> wrote:
> It would seem a bit more useful if there was some sort of correlation
> between poewr output and some other measurement such as TT speed.
But TT speed has only two variables (other than wind, road surface,
hills), power output for the time period, and aerodynamic drag. Aero
drag should be closely related to rider weight/size so if you know
weight and power somebody like Andy could reasonably calculate your TT
time and shoe size.
-WG
Robert Chung
Not quite. The "A" part of CdA varies roughly with the 2/3 power of mass,
but the "Cd" part doesn't. Because of the way these things scale, W/kg is
a good indicator of climbing ability, but total W is a good indicator of
TT ability.
gwhite
Mark Fennell wrote:
>
> ... IMHO, this is really good stuff for anyone
> who wants to be at all analytical or objective
> about his/her training and performance....
Finally. A thread where Chang will have nothing to contribute.
Kurgan Gringioni
> ability levels and specialties (and all-arounders). Does anyone have
> some profiles they can share? My profile shows decent lactate
> tolerance and VO2Max but pretty weak short-term power. I'm curious, is
> there really anyone that is well-trained and has a flat profile?
>
> Also, W/kg is clearly a good indicator of climbing performance. But
> for time trialing, it isn't that strongly related is it?
>In my case,
> my 20-minute W/kg suggest I should be in the cat 1-2 range which I
> think is reasonable for climbing, but, trust me, it's way off for time
> trialing. In your experience, should someone be able to work on their
> aero position, etc. so that their climbing and tt'ing are comparable,
> at least relative to other riders in the same category?
If you work on your aero position, you should be able to get much better
than riders in your category.
The reason is that getting more aero is not easy to quantify, unless one has
access to a wind tunnel. People will spend $5 per gram shaving weight off
their bike, yet not spend any time at all improving their time trial
position, where the relative benefits are much higher.
IIRC, if the drag coefficient for riding on the hoods is 100, then getting
in the drops is ~80% of that, getting a full aero setup is ~65-70%, etc.
Riders like Colby Pearce or Chris Boardman could get down to ~50% or lower.
The proportional savings are far greater than shaving a pound or two off
your bike, especially when one considers that the weight of the rider must
be factored into the proportional savings of the system as a whole.
>In other
> words, is body mass a good indicator for the aerodynamic drag one
> should be able to achieve? I wouldn't think so,
You are correct, body mass is not a good indicator.
>but the power-profile
> article and table sort of suggest that one's climbing and tt'ing can
> be similarly categorized based on mass alone.
That may be true if one generalizes, but in specific cases (like Boardman or
Pearce) it is not true. My last year racing, I went ahead and worked on the
TT position after ignoring it for 10 years. I was still pretty crappy at it,
but I could tell the value it had by taking it out on group rides. It's
pretty amazing what a difference it makes. If I were to ever race again, I'd
spend a lot of time trying to get more aero with a normal road setup.
I don't know if you watched the pro1/2 Socal races after your races (I'm
assuming you're master), but notice how Paolinetti was always forearms on
the handlebar in breakaways, even through turns? He had that figured out.
warren
So what else is new?
-WG
gwhite
Nada. Stick a fork in me, I'm done.
Jeff Jones
> "5 min" and "20 min" W/kg values, at least in the Div. III pro through
> cat 3 range, and perhaps a little high for the "5 s" and "1 min"
> values. For example, I am pretty confident that the best cat 1
> climbers can put out more than 5.19 W/kg over a 20-minute effort.
>
about 5 "vertical squares" below that of my 20 min value. But I always knew
I couldn't sprint :-). Wish it wasn't so critical.
Jeff
Ewoud Dronkert
>It would be fascinating to see some real profiles for a variety of
>ability levels and specialties (and all-arounders).
Check the rowing world, they've been doing it for years. They do tests
on the Concept2 rowing machine, and, ideally, the power output should
be distributed thus:
Test Hwt men Lwt women
10" 123% 118%
1' 115% 112%
2 km 100% 100%
6 km 93% 95%
1 h ? 90%
(The numbers for Lwt men and hwt women are in between these. For hwt
men, 2k takes about 6' and 6k about 19'30". Lwt women 7'15" and
23'00". "Heavyweight" really means "open class"; typically those men
are 1m95 and 90 kg. Lightweight women cannot weigh more than 59 kg and
are around 1m70.)
In rowing, the goal is always to deliver a maximum performance on 2
km, that's why that score is a reference at 100%. If some of your
percentages fall behind, you should spend (extra) time training that
particular zone. Ultimately, that will benefit the 2k score.
Andy Coggan
news:3f41987d$0$1147$626a...@news.free.fr...
Except that Heil et al. have concluded that Cd also varies inversely with
weight (with an exponent of -0.45). The overall result is then as Warren
indicates, i.e., even though mass per se has little effect on the power
requirement to travel at a fixed velocity on a completely flat road, W/kg is
still likely to be a better predictor of TT performance than W alone.
Andy Coggan
Andy Coggan
> Profiling" at www.cyclingpeaks.com containing an Excel table of W/kg
> for different duration efforts and a range of performance levels going
> from world champions down to untrained athletes. IMHO, this is really
> good stuff for anyone who wants to be at all analytical or objective
> about his/her training and performance. That said, I have a number of
> questions and comments for Andy or any other of the power gurus and
> advocates. (Warning: this may turn out to be a long post so either
> move on now, or go read his article if you haven't already.)
>
> First, it seems like the way you bracketed the groups is natural, and
> in my admittedly subjective experience and observation, the overlap is
> reasonable. By that I mean, for example, the "lower half" of the cat
> 1's is comparable to the "upper half" of the 2's, etc., at least to
> first order. I'm curious how confident you are in the values in the
> table between "World Champ" and "Untrained". I ask for two reasons.
> For one, my own profile doesn't fit the way I would expect. And
> second, the values in the table progress linearly (as you move through
> ability levels) and the brackets cover a constant, wide range. As we
> all know, assume a relationship is linear if we don't have enough data
> or insights that say it should be otherwise!
As the accompanying article indicates, I fixed the upper and lower ends of
each range based on known power outputs of world champions/world record
holders and untrained individuals, respectively. The values in between were
spread equally (i.e., linear relationship assumed), simply because at
present there's not enough data to justify doing otherwise. Remember, the
purpose of the tables is to compare relative ability across different
exercise durations reflecting different physiological characteristics, not
to attempt to assign or describe riders of different categories (strip the
category guidelines from the tables, and they would be just as useful). This
is why I didn't assume a normal distribution and spread the values that
way - that might (or might not - no one at present has the data to say for
sure) better reflect reality, but has the disadvantage of squeezing
everything together toward the middle, making anyone who isn't well above or
well below average appear to be an "all rounder".
> In particular, I'm wondering if you might be a little bit low with the
> "5 min" and "20 min" W/kg values, at least in the Div. III pro through
> cat 3 range, and perhaps a little high for the "5 s" and "1 min"
> values. For example, I am pretty confident that the best cat 1
> climbers can put out more than 5.19 W/kg over a 20-minute effort.
>
> My own profile, at age 42, is as follows:
>
> Duration: W/kg:
> ----------------------
> 20 minute: 4.7
> 5 minute: 5.1
> 1 minute: 8.1
> 5 second: 13-15
>
> My values were about 10% higher when I last raced seriously, about 12
> years ago. I did win a couple of P12 road races then, but I was
> certainly not at the level that the table indicates for the 20-minute
> level. OTOH, I'm pretty sure I could sprint better than the average
> cat 4, which is where the table puts me for the 5-second test.
Better than the average cat 4 *match sprinter*, as that notion implies for
somebody with that relative ability to compared to, e.g., Sean Eadie? Again,
as described in the accompanying article, by basing things on the
performance of specialists (match sprinters for 5 s), the scales tend to be
skewed from a road racers perspective. To state it another way: compared to
a true sprinter, most people racing on the road *do* have relatively low
neuromuscular power. However, I don't think one really can or should try to
develop discipline-specific tables. First, too many people cross over to
different disciplines, thus making it difficult to develop valid standards,
esp. since the only point proposing discipline-specific tables would be to
improve the category guidelines - which aren't the point of the tables in
the first place. Second, discipline-specific tables would deviate from the
logic that was used to develop the tables in the first place.
> BTW, please don't think I'm nit-picking the article and the table. I
> think the information is great and really useful. I just think you
> might like hearing about some other data points!
>
> Another question or two...
>
> It would be fascinating to see some real profiles for a variety of
> ability levels and specialties (and all-arounders). Does anyone have
> some profiles they can share? My profile shows decent lactate
> tolerance and VO2Max but pretty weak short-term power. I'm curious, is
> there really anyone that is well-trained and has a flat profile?
>
> Also, W/kg is clearly a good indicator of climbing performance. But
> for time trialing, it isn't that strongly related is it? In my case,
> my 20-minute W/kg suggest I should be in the cat 1-2 range which I
> think is reasonable for climbing, but, trust me, it's way off for time
> trialing. In your experience, should someone be able to work on their
> aero position, etc. so that their climbing and tt'ing are comparable,
> at least relative to other riders in the same category? In other
> words, is body mass a good indicator for the aerodynamic drag one
> should be able to achieve? I wouldn't think so, but the power-profile
> article and table sort of suggest that one's climbing and tt'ing can
> be similarly categorized based on mass alone.
This has been addressed in other posts...I'll only add the reminder (once
again) that the point of the tables is to help evaluate somebody's relative
strengths and weaknesses, not predict their performance.
> Anyway, thanks again for sharing your great information and insights.
You're welcome.
BTW, there is a ~700 member mailing list at
www.topica.com/lists/wattage/read devoted to discussion of training with
power meters, etc....based on the interest you've expressed here, you might
want to give it a read.
Andy Coggan
Robert Chung
> "Robert Chung" <inv...@nospam.com> wrote
>> Not quite. The "A" part of CdA varies roughly with the 2/3 power of
>> mass, but the "Cd" part doesn't. Because of the way these things
>> scale, W/kg is a good indicator of climbing ability, but total W is a
>> good indicator of TT ability.
>
> Except that Heil et al. have concluded that Cd also varies inversely
> with weight (with an exponent of -0.45). The overall result is then as
> Warren indicates, i.e., even though mass per se has little effect on
> the power requirement to travel at a fixed velocity on a completely
> flat road, W/kg is still likely to be a better predictor of TT
> performance than W alone.
Cd varies inversely with mass? Hmmm, I didn't know that. Anyway, if A
varies (roughly) with m^.67 and Cd varies (roughly) with m^(-.45), then
CdA would vary roughly with m^(.2). A 25% difference in mass gives a 2%
difference in CdA?
Robert Chung
Goddammit, I hit the wrong key. Anyway, my calculation was off but the
point should still be the same: A 25% difference in mass gives a 5%
difference in CdA?
warren
<inv...@nospam.com> wrote:
> I wrote:
> > Andy Coggan wrote:
> >> "Robert Chung" <inv...@nospam.com> wrote
> >>> Not quite. The "A" part of CdA varies roughly with the 2/3 power of
> >>> mass, but the "Cd" part doesn't. Because of the way these things
> >>> scale, W/kg is a good indicator of climbing ability, but total W is a
> >>> good indicator of TT ability.
> >>
> >> Except that Heil et al. have concluded that Cd also varies inversely
> >> with weight (with an exponent of -0.45). The overall result is then as
> >> Warren indicates, i.e., even though mass per se has little effect on
> >> the power requirement to travel at a fixed velocity on a completely
> >> flat road, W/kg is still likely to be a better predictor of TT
> >> performance than W alone.
I cheated by recalling an article in VeloNews from years back about two
guys who claimed they could predict TT times based on the riders'
wattage output and their aero drag. Whatever happened to those guys?
> > Cd varies inversely with mass? Hmmm, I didn't know that. Anyway, if A
> > varies (roughly) with m^.67 and Cd varies (roughly) with m^(-.45), then
> > CdA would vary roughly with m^(.2). A 25% difference in mass gives a 2%
> > difference in CdA?
>
> Goddammit, I hit the wrong key. Anyway, my calculation was off but the
> point should still be the same: A 25% difference in mass gives a 5%
> difference in CdA?
At Analytic Cycling he uses "effective frontal area" measured in square
meters for aero drag. I'm curious if you can calculate reasonably well
this based on rider height and weight. He says typical values are .4 to
.7 m2. Last night I did a little test on a perfectly flat road, 26.5
mph, 1 minute, back and forth once each. There was a very slight wind
and my efa numbers according to his calculations were .75 and .90
(tailwind and headwind).
-WG
Robert Chung
>
> I cheated by recalling an article in VeloNews from years back about two
> guys who claimed they could predict TT times based on the riders'
> wattage output and their aero drag. Whatever happened to those guys?
I agree, you can do a good job predicting TT times based on wattage and
aero drag; but what you wrote upthread was that if you know wattage and
*weight* someone could predict TT times. Someone could -- I just think the
prediction wouldn't be as good as wattage and aero drag.
> At Analytic Cycling he uses "effective frontal area" measured in square
> meters for aero drag. I'm curious if you can calculate reasonably well
> this based on rider height and weight. He says typical values are .4 to
> .7 m2. Last night I did a little test on a perfectly flat road, 26.5
> mph, 1 minute, back and forth once each. There was a very slight wind
> and my efa numbers according to his calculations were .75 and .90
> (tailwind and headwind).
Estimating CdA from open air field tests is kinda difficult, though Allen
Lim claims to be able to do it. I'm skeptical, though of course I'm not
privy to his data. I went through a little exercise on the wattage list a
few months ago with a guy who had some power data and was trying to
estimate CdA from it. Even though the data were moderately clean the
coefficient of variation was kinda high. Andy has done some stuff on
trying to calculate CdA from a rider in a velodrome (I *think* it might
have been an outdoor velodrome rather than an indoor one).
Mark Fennell
>
> As the accompanying article indicates, I fixed the upper and lower ends of
> each range based on known power outputs of world champions/world record
> holders and untrained individuals, respectively. The values in between were
> spread equally (i.e., linear relationship assumed), simply because at
> present there's not enough data to justify doing otherwise. Remember, the
> purpose of the tables is to compare relative ability across different
> exercise durations reflecting different physiological characteristics, not
> to attempt to assign or describe riders of different categories (strip the
> category guidelines from the tables, and they would be just as useful). This
> is why I didn't assume a normal distribution and spread the values that
> way - that might (or might not - no one at present has the data to say for
> sure) better reflect reality, but has the disadvantage of squeezing
> everything together toward the middle, making anyone who isn't well above or
> well below average appear to be an "all rounder".
>
Fair enough! But it would still be extremely useful to see some actual
profiles for a variety of types of riders. Otherwise one doesn't
really know how alarmed (or satisfied) to be with a "/" profile or a
"\" or a "^". Or, how much slope matters? Also, I assume the Untrained
subjects represented characteristics of the general population and
were not in any way predisposed to the 5-second or 20-minute
abilities. I wonder what percentage of people have the genetics (or
whatever) to excel at the 5-second versus the 20-minute performance,
if trained. It seems to me, **in theory**, that would impact whether
or not the columns are linear.
<snip>
>
> BTW, there is a ~700 member mailing list at
> www.topica.com/lists/wattage/read devoted to discussion of training with
> power meters, etc....based on the interest you've expressed here, you might
> want to give it a read.
make it ~701. My apologies if this has all been discussed many times
before. I just subscribed to the wattage list this morning and will
lurk there awhile before asking anymore (tedious) questions! :)
Mark Fennell
Mark Fennell
>
> If you work on your aero position, you should be able to get much better
> than riders in your category.
>
> The reason is that getting more aero is not easy to quantify, unless one has
> access to a wind tunnel. People will spend $5 per gram shaving weight off
> their bike, yet not spend any time at all improving their time trial
> position, where the relative benefits are much higher.
>
I agree with this concept, but I'll never tt anywhere close to guys
like Thurlow Rogers or Eric Sternlict in SoCal. I'd be pleased to add
a mph or two though.
>
> I don't know if you watched the pro1/2 Socal races after your races (I'm
> assuming you're master), but notice how Paolinetti was always forearms on
> the handlebar in breakaways, even through turns? He had that figured out.
In fact I was on Jamie's team in 1997 and had the pleasure of watching
(from the comfort of the peloton) him win the Manhattan Beach GP in a
break. You are right; he slices through the air really well.
Mark Fennell
Andy Coggan
I suppose we could put up some examples on the website.
> Also, I assume the Untrained
> subjects represented characteristics of the general population and
> were not in any way predisposed to the 5-second or 20-minute
> abilities.
No reason to think that the values are skewed in any way.
> I wonder what percentage of people have the genetics (or
> whatever) to excel at the 5-second versus the 20-minute performance,
> if trained. It seems to me, **in theory**, that would impact whether
> or not the columns are linear.
It seems to me that if you assume that there's a big enough population base
fighting it out to be "top dog" in each speciality, then that assures that
the scales will align properly (the most important part). As I indicated
before, logically one would expect that each scale should *not* be linear
(thus addressing your point about the extremes), but instead be normally
distributed. I could, for example, have assumed that world champion/world
record performance is, say, 5 SDs above the mean, and the lowest level of
the untrained 5 SDs below, or something like that - however, that doesn't
alter the comparison across scales, and has the disadvantage of crowding
together all values in the middle.
To reiterate: the category guidelines accompanying the scales are just rough
approximations, i.e., most riders of a certain category can generate the
specified power for the specified duration - however, that doesn't mean that
all can, nor does it mean that just because you can generate a certain
amount of power that you should be a certain category (although it does
indicate that you have that potential).
One more caveat: from a theoretical perspective, the values should really be
W/kg^0.67, not W/kg...however, I think that such allometric scaling might be
a little beyond the average person's grasp, at least w/o extensive
explanation.
Andy Coggan
Andy Coggan
You're the one that said A varies with mass^0.67, not me (remember that
we're talking about frontal area of a rider in the aero position, not simple
body surface area. Be that as it may, Heil concluded that Cd must vary with
mass^-0.45 because of experimental observations that CdA varies with
mass^0.33 (or thereabouts). Depending on what other variables were entered
into the multiple regression, A in their study varied with mass^0.408 to
mass^0.762....meaning that Cd had to be inversely related to mass to get the
coefficient for mass related to CdA down around one-third.
Andy Coggan
Kurgan Gringioni
> "Kurgan Gringioni" <kgringioni.rem...@hotmail.com> wrote in
message news:<NFh0b.4015$Nc.26...@news1.news.adelphia.net>...
> >
> > If you work on your aero position, you should be able to get much better
> > than riders in your category.
> >
> > The reason is that getting more aero is not easy to quantify, unless one
has
> > access to a wind tunnel. People will spend $5 per gram shaving weight
off
> > their bike, yet not spend any time at all improving their time trial
> > position, where the relative benefits are much higher.
> >
>
> I agree with this concept, but I'll never tt anywhere close to guys
> like Thurlow Rogers or Eric Sternlict in SoCal. I'd be pleased to add
> a mph or two though.
All it takes, like anything else in cycling, is work. Stretching, a lot of
it, so that your lower back and hamstrings are long enough to make power in
the low position. One day/week of interval training in the position. Gradual
upgrading of the tt bike on all 1st order components (ones which break the
wind). And constant tweaking of the position, timing differences on a long
straight windless descent (coasting down, poor man's wind tunnel).
> > I don't know if you watched the pro1/2 Socal races after your races (I'm
> > assuming you're master), but notice how Paolinetti was always forearms
on
> > the handlebar in breakaways, even through turns? He had that figured
out.
>
> In fact I was on Jamie's team in 1997 and had the pleasure of watching
> (from the comfort of the peloton) him win the Manhattan Beach GP in a
> break. You are right; he slices through the air really well.
Damn, you were on that team? Email me in private if you wish, I've got an
apocryphal thing to relate from that year.
The reason I thought you were a Master is because of the Longo Visalia story
you related.
Andy Coggan
news:190820030823419787%war...@usvhremove.com...
> In article <3f4219d1$0$16160$626a...@news.free.fr>, Robert Chung
> <inv...@nospam.com> wrote:
>
> > I wrote:
> > > Andy Coggan wrote:
> > >> "Robert Chung" <inv...@nospam.com> wrote
> > >>> Not quite. The "A" part of CdA varies roughly with the 2/3 power of
> > >>> mass, but the "Cd" part doesn't. Because of the way these things
> > >>> scale, W/kg is a good indicator of climbing ability, but total W is
a
> > >>> good indicator of TT ability.
> > >>
> > >> Except that Heil et al. have concluded that Cd also varies inversely
> > >> with weight (with an exponent of -0.45). The overall result is then
as
> > >> Warren indicates, i.e., even though mass per se has little effect on
> > >> the power requirement to travel at a fixed velocity on a completely
> > >> flat road, W/kg is still likely to be a better predictor of TT
> > >> performance than W alone.
>
> I cheated by recalling an article in VeloNews from years back about two
> guys who claimed they could predict TT times based on the riders'
> wattage output and their aero drag. Whatever happened to those guys?
Maybe these guys? www.pkracing.com (I hope that URL is correct.)
In any case, prediction of TT times from power and aero drag can be done
with tremendous accuracy...as long as you also know the course profile and
wind speed/direction accurately enough.
> > > Cd varies inversely with mass? Hmmm, I didn't know that. Anyway, if A
> > > varies (roughly) with m^.67 and Cd varies (roughly) with m^(-.45),
then
> > > CdA would vary roughly with m^(.2). A 25% difference in mass gives a
2%
> > > difference in CdA?
> >
> > Goddammit, I hit the wrong key. Anyway, my calculation was off but the
> > point should still be the same: A 25% difference in mass gives a 5%
> > difference in CdA?
>
> At Analytic Cycling he uses "effective frontal area" measured in square
> meters for aero drag. I'm curious if you can calculate reasonably well
> this based on rider height and weight. He says typical values are .4 to
> .7 m2.
FWIW, that's A, not CdA...the numbers are in the right ballpark, maybe a
little low. OTOH, the default value for Cd that Tom uses (i.e., 0.5) is too
low, so the product (i.e., 0.25 m^2) is in the right ballpark.
> Last night I did a little test on a perfectly flat road, 26.5
> mph, 1 minute, back and forth once each. There was a very slight wind
> and my efa numbers according to his calculations were .75 and .90
> (tailwind and headwind).
You *really* need to subscribe to the wattage list...
Bottom line: while *very careful* field testing can yield fairly precise
numbers for CdA (i.e., coefficient of variation of ~2%), it still really
isn't good enough to be of much use (e.g., for choosing equipment, or even
optimizing position). That's why I'm going back to the wind tunnel this
winter...anybody want to join me?
Andy Coggan
Andy Coggan
> Estimating CdA from open air field tests is kinda difficult, though Allen
> Lim claims to be able to do it. I'm skeptical, though of course I'm not
> privy to his data.
He presented some data in an abstract at the American College of Sports
Medicine meetings in early June. As predicted on the wattage list, despite
using a rather unique venue (i.e., a large aircraft hangar) the precision
wasn't as good as what you can achieve in a wind tunnel, and in fact was no
better than what I found in my experiments (see below)
> I went through a little exercise on the wattage list a
> few months ago with a guy who had some power data and was trying to
> estimate CdA from it. Even though the data were moderately clean the
> coefficient of variation was kinda high. Andy has done some stuff on
> trying to calculate CdA from a rider in a velodrome (I *think* it might
> have been an outdoor velodrome rather than an indoor one).
Correct: I used data collected at Alkek and Trexlertown. Coefficient of
variation for repeated 2 km trials was ~2%...about the same as Lim reported,
and still not good enough to be particularly helpful.
More recently, I've conducted three days of testing using Lim's approach of
mulitple speed trials to separate CdA and Crr...despite doing the testing
very early in the morning on very flat roads, precision was again only about
2%. One impressive finding from these experiments was how little wind it
takes to really skew the results - for example, on a day so calm that a tiny
piece of dry leaf dropped from overhead falls to the ground less than 1 foot
from vertical, there are still significant differences in estimated CdA
depending on whether you are headed "upwind" or "downwind". Similary, trials
conducted less than a full minute after a vehicle passes down the road at
~30 mph also produce abnormally high or low values, depending on whether the
trial was in the same direction or the opposite direction in which the
vehicle passed.
Andy Coggan
Robert Chung
> "Robert Chung" <inv...@nospam.com> wrote in message
> news:3f421264$0$16143$626a...@news.free.fr...
>>
>> CdA would vary roughly with m^(.2). A 25% difference in mass
>
> Heil concluded that Cd
> must vary with mass^-0.45 because of experimental observations that CdA
> varies with mass^0.33 (or thereabouts).
So if CdA varies with m^0.33, then a 25% difference in mass gives a 7.5%
difference in CdA?
Andy Coggan
I know that's a rhetorical question, but the answer is yes: all else (e.g.,
height, position) being equal, a 25% increase in mass theoretically results
in only a 7.5% difference in CdA. I believe that makes sense if you think
about it...for example, if I gained 37.5 lbs I'd be a true masters fattie,
but I wouldn't be *that* much wider or higher (assuming I could still get
down on the aerobars w/ a big belly in the way).
Andy Coggan
Mark Fennell
<snip>
>
> > > I don't know if you watched the pro1/2 Socal races after your races (I'm
> > > assuming you're master), but notice how Paolinetti was always forearms
> on
> > > the handlebar in breakaways, even through turns? He had that figured
> out.
> >
> > In fact I was on Jamie's team in 1997 and had the pleasure of watching
> > (from the comfort of the peloton) him win the Manhattan Beach GP in a
> > break. You are right; he slices through the air really well.
>
>
> Damn, you were on that team? Email me in private if you wish, I've got an
> apocryphal thing to relate from that year.
>
Thanks, but no thanks (and no offense intended). I have one lasting
memory of that team and year that I will take to my grave. On July 6th
1997, in a matter of moments, I went from an endorphin- and
adrenalin-fueled euphoria at being in the (potentially) winning break
over a high-quality field, to an immediate emotional devestation and
shock when the race was stopped and I was told that a teammate had
died of injuries suffered in a crash earlier in the race. I really
don't need to learn anything more about that year, especially if it is
negative.
> The reason I thought you were a Master is because of the Longo Visalia story
> you related.
You are correct; I do race Masters now, almost exclusively.
Mark
Robert Chung
> "Robert Chung" <inv...@nospam.com> wrote in message
> news:3f42454d$0$259$626a...@news.free.fr...
>
>> Estimating CdA from open air field tests is kinda difficult, though
>> Allen Lim claims to be able to do it. I'm skeptical, though of course
>> I'm not privy to his data.
>
> He presented some data in an abstract at the American College of Sports
> Medicine meetings in early June. As predicted on the wattage list,
> despite using a rather unique venue (i.e., a large aircraft hangar) the
> precision wasn't as good as what you can achieve in a wind tunnel, and
> in fact was no better than what I found in my experiments (see below)
I know I shouldn't do this, but I can't help it. In case Warren thinks
Andy is exaggerating Allen Lim's claim about wind tunnels, the exact quote
is, "it's our belief that the aerodynamic and rolling resistance values we
calculate in the real world using the Power Tap are more accurate than a
wind tunnel."
You can find that quote about three-quarters of the way down this bike.com
article:
http://www.bike.com/template.asp?date=2%2F13%2F2003&lsectionnumber=5
warren
<inv...@nospam.com> wrote:
> Andy Coggan wrote:
> > "Robert Chung" <inv...@nospam.com> wrote in message
> > news:3f42454d$0$259$626a...@news.free.fr...
> >
> >> Estimating CdA from open air field tests is kinda difficult, though
> >> Allen Lim claims to be able to do it. I'm skeptical, though of course
> >> I'm not privy to his data.
> >
> > He presented some data in an abstract at the American College of Sports
> > Medicine meetings in early June. As predicted on the wattage list,
> > despite using a rather unique venue (i.e., a large aircraft hangar) the
> > precision wasn't as good as what you can achieve in a wind tunnel, and
> > in fact was no better than what I found in my experiments (see below)
>
> I know I shouldn't do this, but I can't help it. In case Warren thinks
> Andy is exaggerating Allen Lim's claim about wind tunnels,
No I don't think that. My experience yesterday with a wind of maybe
2-3mph showed a range of about .75m2 to .9m2 so I can't see how one
could achieve +/- 2% accuracy with "no" wind.
> the exact quote
> is, "it's our belief that the aerodynamic and rolling resistance values we
> calculate in the real world using the Power Tap are more accurate than a
> wind tunnel."
Hard to believe somebody would even say that-especially when they're
relying on a PT.
-WG
warren
Coggan <aco...@earthlink.net> wrote:
> "warren" <war...@usvhremove.com> wrote in message
> news:190820030823419787%war...@usvhremove.com...
> > I cheated by recalling an article in VeloNews from years back about two
> > guys who claimed they could predict TT times based on the riders'
> > wattage output and their aero drag. Whatever happened to those guys?
>
> Maybe these guys? www.pkracing.com (I hope that URL is correct.)
Actually I remembered it as being you and Jim Martin. Guess not.
> > Last night I did a little test on a perfectly flat road, 26.5
> > mph, 1 minute, back and forth once each. There was a very slight wind
> > and my efa numbers according to his calculations were .75 and .90
> > (tailwind and headwind).
>
> You *really* need to subscribe to the wattage list...
I've been lurking off the Topica website but I have to wade through
alot of talk about hardware issues and time trialing-neither of which
interest me that much. There are some pearls there though.
>
> Bottom line: while *very careful* field testing can yield fairly precise
> numbers for CdA (i.e., coefficient of variation of ~2%), it still really
> isn't good enough to be of much use (e.g., for choosing equipment, or even
> optimizing position).
I was just trying to get a ballpark for my frontal area and to compare
my Polar power readings with his caluclations.
> That's why I'm going back to the wind tunnel this
> winter...anybody want to join me?
Curious, what does that cost?
-WG
Tom Kunich
then be pretty predictable given the DIFFERENCE in times and the wind
speed.
"Robert Chung" <inv...@nospam.com> wrote in message
news:3f42454d$0$259$626a...@news.free.fr...
Andy Coggan
> In article <3f429965$0$16525$626a...@news.free.fr>, Robert Chung
> <inv...@nospam.com> wrote:
>
> > Andy Coggan wrote:
> > > "Robert Chung" <inv...@nospam.com> wrote in message
> > > news:3f42454d$0$259$626a...@news.free.fr...
> > >
> > >> Estimating CdA from open air field tests is kinda difficult, though
> > >> Allen Lim claims to be able to do it. I'm skeptical, though of course
> > >> I'm not privy to his data.
> > >
> > > He presented some data in an abstract at the American College of
Sports
> > > Medicine meetings in early June. As predicted on the wattage list,
> > > despite using a rather unique venue (i.e., a large aircraft hangar)
the
> > > precision wasn't as good as what you can achieve in a wind tunnel, and
> > > in fact was no better than what I found in my experiments (see below)
> >
> > I know I shouldn't do this, but I can't help it. In case Warren thinks
> > Andy is exaggerating Allen Lim's claim about wind tunnels,
>
> No I don't think that. My experience yesterday with a wind of maybe
> 2-3mph showed a range of about .75m2 to .9m2 so I can't see how one
> could achieve +/- 2% accuracy with "no" wind.
A wind of 2-3 mph is actually quite significant in this context, as I tried
to relate. Be that as it may, your results may be better than you think.
With a reasonable sample size, the SD is usually about half the range, so
assuming that 0.75-0.90 m^2 reflects the limits, then you're already under
10%.
.
> > the exact quote
> > is, "it's our belief that the aerodynamic and rolling resistance values
we
> > calculate in the real world using the Power Tap are more accurate than a
> > wind tunnel."
>
> Hard to believe somebody would even say that-especially when they're
> relying on a PT.
If I had to trust the numbers from any power meter completely blindly, w/o
calibrating it myself, I'd pick a PowerTap over an SRM (esp. the Amateur) or
Polar. That's especially true in this context, since what you really want to
know if power delivered to the rear wheel/road, not the power the rider
actually produces.
Andy Coggan
Andy Coggan
> In article <nhu0b.124$Ej6...@newsread4.news.pas.earthlink.net>, Andy
> Coggan <aco...@earthlink.net> wrote:
>
> > "warren" <war...@usvhremove.com> wrote in message
> > news:190820030823419787%war...@usvhremove.com...
>
> > > I cheated by recalling an article in VeloNews from years back about
two
> > > guys who claimed they could predict TT times based on the riders'
> > > wattage output and their aero drag. Whatever happened to those guys?
> >
> > Maybe these guys? www.pkracing.com (I hope that URL is correct.)
>
> Actually I remembered it as being you and Jim Martin. Guess not.
Jim, John Cobb, Kevin McFadden (wind tunnel guru for GM), Doug Milliken
(race car suspension genius, HPV expert, and Moulton aficianado) and I
collaborated on a scientific study that was published in J. Appl. Biomech.
However, to the best of my knowledge that didn't result in a lay article in
VeloNews (unless perhaps Jim wrote one, and didn't mention it to me).
>
> > > Last night I did a little test on a perfectly flat road, 26.5
> > > mph, 1 minute, back and forth once each. There was a very slight wind
> > > and my efa numbers according to his calculations were .75 and .90
> > > (tailwind and headwind).
> >
> > You *really* need to subscribe to the wattage list...
>
> I've been lurking off the Topica website but I have to wade through
> alot of talk about hardware issues and time trialing-neither of which
> interest me that much. There are some pearls there though.
> >
> > Bottom line: while *very careful* field testing can yield fairly precise
> > numbers for CdA (i.e., coefficient of variation of ~2%), it still really
> > isn't good enough to be of much use (e.g., for choosing equipment, or
even
> > optimizing position).
> I was just trying to get a ballpark for my frontal area and to compare
> my Polar power readings with his caluclations.
Ack - Polar?? ;-)
> > That's why I'm going back to the wind tunnel this
> > winter...anybody want to join me?
> Curious, what does that cost?
Depends on who you are/who you know...but as I recently told somebody else,
you might end spending as much on travel, food, lodging as on actual tunnel
time.
Andy Coggan
Kurgan Gringioni
message news:<bdu0b.4220$Nc.28...@news1.news.adelphia.net>...
> >
>
> memory of that team and year that I will take to my grave.
<snip>
It's something to do with that, but not really negative. That was a bad day
and ya, none of us will forget it.
warren
Coggan <aco...@earthlink.net> wrote:
> "warren" <war...@usvhremove.com> wrote in message
>
> > I was just trying to get a ballpark for my frontal area and to compare
> > my Polar power readings with his caluclations.
>
> Ack - Polar?? ;-)
Hindsight? The numbers are within 5% of what was measured during the
lab tests and they seem to be consistent across a range and coincide
with calculations at analytic cycliing-assuming my frontal area
estimate is fairly close. I got the HRM first and when it was time to
add the power sensor the only reasonable option was to buy the Polar
power sensor. The best thing about that was buying it from Performance
Bike because after 13 months with it I'm now on my third power sensor
unit and Performance just asks me if I want a refund or a replacement.
After the next one I think it will be "refund please" so I can buy the
SRM.
-WG
Kraig Willett
thoughts of anyone other than myself (and that goes for anything you see me
write in any medium at anytime in the future or in the past) - if you can't
figure that one out, then, well, I reckon I can't be held responsible for
how you perceive my commentary.
I've done a bit on the whole cheap-ass aerodynamicist/garage science front.
I am not nearly as smart as Dr. Coggan, Dr. Chester Kyle, nor do I have the
cycling specific wind tunnel time of others in the bike related industry
(though, I have more than your average "joe"), but I think people can
objectively take a look at their position/frontal area for a small
investment of their time (yes, I realize that a wind tunnel is more than
likely the best way to definitively answer the "what position is best for
_me_?" question, but not everyone can afford/wants to go to Texas in the
winter, and the "right" methodology once you are there is still debatable!).
Field testing may be able to produce reliable results, but, IMHO, the time
investment necessary to produce a statiscally significant conclusion is
prohibitive for a large scale variable study - i.e, I can generate 100+
statistically significant datasets in a tunnel in one day - try doing that
with a field test...
I have documented some of my experiences (yes, the following links are
"free" to view) with mathematical modelling, rider position/frontal area
determination and whatnot on my website.
of particular interest are the comparative frontal area results (where my
body measures did not change, but my frontal area certainly did!): - forgive
the wordwrap - its either this, or get flamed for using tinyurl.com - so
live with it...
http://www.biketechreview.com/projects/frontalarea/kw.htm
a comparison between me and someone "important":
http://www.biketechreview.com/projects/frontalarea/comparison.htm
My freakishness has even been tolerated by a certain professional cycling
team:
http://www.biketechreview.com/projects/frontalarea/animations.htm
and concurrently documented by velonews.com:
http://users.adelphia.net/~kwillett/images/vn.gif
an analysis of the fitchburg TT and what type of power pacing strategy could
be most appropriate:
http://www.biketechreview.com/projects/TTpacing/Fitchburg.htm
an analysis of the Redlands Rubidoux prologue TT and equipment selection
(the article titled:
6/5/2002 - Is Time-Trial Equipment Selection "Significant") on the page at:
http://www.biketechreview.com/projects/bikecomlinks.htm
I am still developing my methodology for determining frontal area, so for a
limited time (say, the first 5 people that email me offline) I would be
willing to document their frontal area for free if they agree to execute the
procedure according to a certain protocol and provide certain body
dimensions (heh, I wrote "body dimension").
Enjoy,
--
==================
Kraig Willett
www.biketechreview.com
==================
Benjamin Weiner
> > So if CdA varies with m^0.33, then a 25% difference in mass gives a 7.5%
> > difference in CdA?
> I know that's a rhetorical question, but the answer is yes: all else (e.g.,
> height, position) being equal, a 25% increase in mass theoretically results
> in only a 7.5% difference in CdA. I believe that makes sense if you think
> about it...for example, if I gained 37.5 lbs I'd be a true masters fattie,
> but I wouldn't be *that* much wider or higher (assuming I could still get
> down on the aerobars w/ a big belly in the way).
You guys probably know this, but you're talking about two
different relationships. One is a relation between CdA and
mass across a population (all riders, elites, fatties, whatever).
I assume this is what was measured in the article.
The other is the relation between CdA and mass for a given rider.
The two relations do not have to have the same log slope.
If the population is not representative there can be a strong
bias - for example suppose it was all fairly fit trained riders.
Then Coggan*1.0 would probably fall somewhere near the relation
(or below, given his low position) but Coggan*1.25 wouldn't
necessarily, esp. since there was nobody that belly-enhanced in the
sample population.
This is just like the early history of the 220-age HR "rule," BTW -
IIRC it was originally derived from a single relatively unusual
population, not a longitudinal study, and not intended for the
abuses to which it has been put.
-Ben
Gah! Selection effects!
Robert Chung
>
> You guys probably know this, but you're talking about two
> different relationships. One is a relation between CdA and
> mass across a population (all riders, elites, fatties, whatever).
> I assume this is what was measured in the article.
> The other is the relation between CdA and mass for a given rider.
Right, I hadn't forgotten that. This subthread started off because I think
that W is a slightly better predictor of TT times across riders, while
Andy thinks that W/kg is. The calculation above shows that CdA is
relatively inelastic wrt mass.
> This is just like the early history of the 220-age HR "rule," BTW -
> IIRC it was originally derived from a single relatively unusual
> population, not a longitudinal study, and not intended for the
> abuses to which it has been put.
>
> -Ben
> Gah! Selection effects!
http://www.google.com/groups?selm=3C0BE333.B09B8254%40aol.com
I love that story. A non-negligible proportion of my own research findings
have been made in airplanes while on the way to meetings.
Andy Coggan
news:3f430ee5$1...@news.ucsc.edu...
> Andy Coggan <aco...@earthlink.net> wrote:
> > "Robert Chung" <inv...@nospam.com> wrote in message
>
> > > So if CdA varies with m^0.33, then a 25% difference in mass gives a
7.5%
> > > difference in CdA?
>
> > I know that's a rhetorical question, but the answer is yes: all else
(e.g.,
> > height, position) being equal, a 25% increase in mass theoretically
results
> > in only a 7.5% difference in CdA. I believe that makes sense if you
think
> > about it...for example, if I gained 37.5 lbs I'd be a true masters
fattie,
> > but I wouldn't be *that* much wider or higher (assuming I could still
get
> > down on the aerobars w/ a big belly in the way).
>
> You guys probably know this, but you're talking about two
> different relationships.
Actually, we're not (see below).
> One is a relation between CdA and
> mass across a population (all riders, elites, fatties, whatever).
> I assume this is what was measured in the article.
> The other is the relation between CdA and mass for a given rider.
I believe (or at least assume) that Robert is talking about the same thing I
am, which is the relationship in a population. I only tossed in the comment
about what would happen in an individual case as an example for those
unfamiliar with allometric scaling.
Andy Coggan
Kurgan Gringioni
"Kraig Willett" <kdubent...@adelphia.net.remove> wrote in message
news:xWB0b.19795$Ad4.7...@news3.news.adelphia.net...
> FWIW, the contents of this post do not necessarily reflect the opinions or
> thoughts of anyone other than myself (and that goes for anything you see
me
> write in any medium at anytime in the future or in the past) - if you
can't
> figure that one out, then, well, I reckon I can't be held responsible for
> how you perceive my commentary.
>
> I've done a bit on the whole cheap-ass aerodynamicist/garage science
front.
> I am not nearly as smart as Dr. Coggan, Dr. Chester Kyle, nor do I have
the
> cycling specific wind tunnel time of others in the bike related industry
> (though, I have more than your average "joe"), but I think people can
> objectively take a look at their position/frontal area for a small
> investment of their time (yes, I realize that a wind tunnel is more than
> likely the best way to definitively answer the "what position is best for
> _me_?" question, but not everyone can afford/wants to go to Texas in the
> winter, and the "right" methodology once you are there is still
debatable!).
<snip>
It seems to me that the windless hill is still the best test although it
does have a whiff of Fredliness to it.
>I am still developing my methodology for determining frontal area, so for a
>limited time (say, the first 5 people that email me offline)
I'd be surprised if you got very many to reply. Aerodynamics is such a
non-tactile, nebulous concept that almost all racers ignore their position
once they get one that sort of feels acceptable.
It's sort of amazing to me that people don't pay attention to it. They'll
spend $1000 to lose 2 lbs. from their bike, but that's only ~1% gain vs. the
effects of gravity and less than that when one takes friction and wind
resistance into account.
On a flat TT course, OTOH, it's possible to make double digit gains, 10-20%.
Yet almost everyone ignores it.
How many other people in this country pay a lot of attention to aerodynamics
in the racing scene? You. John Cobb. who else?
Benjamin Weiner
> I'd be surprised if you got very many to reply. Aerodynamics is such a
> non-tactile, nebulous concept that almost all racers ignore their position
> once they get one that sort of feels acceptable.
> It's sort of amazing to me that people don't pay attention to it. They'll
> spend $1000 to lose 2 lbs. from their bike, but that's only ~1% gain vs. the
> effects of gravity and less than that when one takes friction and wind
> resistance into account.
Even among physicists there is a tendency to stick to things that
are easily quantifiable - the desire to stick with an equation
that makes things easy to calculate, even if it's not really right.
So it doesn't really surprise me that Joe Bikeracer behaves the
same way - weights are all given in catalogs, but aero benefits
of position or equipment are harder to quantify.
Also, as you have alluded to, it's easier to do things that just
involve spending money, like shaving weight or getting more aero by
buying Zipps. Lots of people have Zipps, I dunno how many have
thought about their positioning. Trigeeks think about aero all the
time, but have they worked on their position beyond reading John Cobb
articles?
BTW, fluid dynamics is enough of a nonlinear pain in the ass that
most physicists are scared of it too.
> On a flat TT course, OTOH, it's possible to make double digit gains, 10-20%.
> Yet almost everyone ignores it.
> How many other people in this country pay a lot of attention to aerodynamics
> in the racing scene? You. John Cobb. who else?
OTOH, I'm not sure what Kraig is proposing to do. I'm not one to
talk, as I am too lazy to even put on my clip-on aerobars, because I
don't feel like redoing the bar tape (however I only do club TTs). My
major investment in this is doing crunches every morning so that I can
ride in the drops with comfort. I think it helps, but who knows.
Kurgan Gringioni
>
> BTW, fluid dynamics is enough of a nonlinear pain in the ass that
> most physicists are scared of it too.
As well they should be. I'm not talking about doing endless cascading
partial differential equations though. The real world Fred comparison test
on the windless hill is what I advocate.
In most cases, eyeballing will help. If a rider's torso is a big air scoop,
the fix is obvious.
> > On a flat TT course, OTOH, it's possible to make double digit gains,
10-20%.
> > Yet almost everyone ignores it.
>
> > How many other people in this country pay a lot of attention to
aerodynamics
> > in the racing scene? You. John Cobb. who else?
>
> OTOH, I'm not sure what Kraig is proposing to do. I'm not one to
> talk, as I am too lazy to even put on my clip-on aerobars, because I
> don't feel like redoing the bar tape (however I only do club TTs). My
> major investment in this is doing crunches every morning so that I can
> ride in the drops with comfort. I think it helps, but who knows.
That would help in the TT position too as long as you go through a full
range of motion.
From what I've seen, the ones who are able to get into extremely aero
positions have very good hamstring and lower back flexibility, which allows
them to get low with the flat back and still make power. If the hamstrings
and lower back are short, then the rider has to sit more upright, with the
obvious consequences with respect to the amount of air they're going to
catch.
Jim Martin
> (race car suspension genius, HPV expert, and Moulton aficianado) and I
> collaborated on a scientific study that was published in J. Appl. Biomech.
> However, to the best of my knowledge that didn't result in a lay article
in
> VeloNews (unless perhaps Jim wrote one, and didn't mention it to me).
Wasn't me.
---
Outgoing mail is certified Virus Free.
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.512 / Virus Database: 309 - Release Date: 8/19/2003
Kraig Willett
Zinn wrote a little sidebar in the 5 February, 1996 edition of VeloNews that
attributed a formula to you. I saved that VeloNews since it was one of the
rare occassions that tunnel data was published (thanks for that, BTW) -
there was a big fallout over that entry and VN story if I remember
correctly, right?
FWIW, I may have the little sidebar "summarized" here for a brief period of
time:
http://www.biketechreview.com/images/martin_method_lo.gif
Carl Sundquist
> positions have very good hamstring and lower back flexibility, which
allows
> them to get low with the flat back and still make power. If the hamstrings
> and lower back are short, then the rider has to sit more upright, with the
> obvious consequences with respect to the amount of air they're going to
> catch.
>
It also helps to develop a TT position where your hips are rotated forward.
This opens up clearance between your quads and chest so you can lower your
position a bit more. Takes a bit of time to callus your taint, though.
warren
Willett <kdubent...@adelphia.net.remove> wrote:
> Hi Jim,
>
> Zinn wrote a little sidebar in the 5 February, 1996 edition of VeloNews that
> attributed a formula to you. I saved that VeloNews since it was one of the
> rare occassions that tunnel data was published (thanks for that, BTW) -
> there was a big fallout over that entry and VN story if I remember
> correctly, right?
>
> FWIW, I may have the little sidebar "summarized" here for a brief period of
> time:
>
> http://www.biketechreview.com/images/martin_method_lo.gif
That's the one I was recalling. I also remember people questioning its
validity. What is this "power" idea?
-WG
Andy Coggan
If people questioned its validity, it may have been because Zinn got things
wrong. Specifically, the model that Jim developed (which is/was similar to
dozens of similar previous efforts...after all, the physics are relatively
straightforward and well understood) and we then validated did not ignore
friction as Zinn stated, but includes terms for wheel bearing friction and
chain drive losses. It also includes terms to account for changes in kinetic
and potential energy, as well the effects of wind. Zinn probably chose to
present the simplest case (i.e., constant speed on a flat road with no wind)
just because it was the simplest, which is understandable...but he did a
disservice to the truth to present things the way he did.
Andy Coggan
Kraig Willett
It was not my intention to have the author of the piece criticized. FWIW, I
thought that issue of VN was worth keeping for 7 years despite the limiting
assumptions made in the sidebar.
warren
Willett <kdubent...@adelphia.net.remove> wrote:
> FWIW, I've taken the summary down.
>
> It was not my intention to have the author of the piece criticized. FWIW, I
> thought that issue of VN was worth keeping for 7 years despite the limiting
> assumptions made in the sidebar.
I agree. I remembered this article because it was the first time I
recall seeing a way to predict TT times from data. It may not have been
perfect but the main point was interesting. I could be wrong but wasn't
this presented at the same time there was some discussion about how to
pick TTT members or something like that and using this kind of data
could allow that?
-WG
Kurgan Gringioni
"Carl Sundquist" <car...@cox-internet.com> wrote in message
news:vkavbcp...@corp.supernews.com...
Wouldn't that involve also getting the lower back and hamstring muscles
longer?
>Takes a bit of time to callus your taint, though.
??
Ewoud Dronkert
> "Carl Sundquist" <car...@cox-internet.com> wrote:
> >Takes a bit of time to callus your taint, though.
>
> ??
That you sit on your dick.
Howard Kveck
"Carl Sundquist" <car...@cox-internet.com> wrote:
> Takes a bit of time to callus your taint, though.
Hey, I bet there's probably a newsgroup or two over in the alt. section that
caters to this exclusively.
--
tanx,
Howard
"Better a lapdog for a slip of a girl than a ... git." Blackadder
remove YOUR SHOES to reply, ok?