In article
<
[email protected]>,
Scott <
[email protected]> wrote:
> On Jan 29, 4:14 pm, John Forrest Tomlinson <[email protected]>
> wrote:
> > On Tue, 29 Jan 2008 07:27:09 -0800 (PST), Scott
> >
> > <[email protected]> wrote:
> > > If they had screaming tailwinds, yes. But, if they
> > >were doing 43+ in a tailwind, it wouldn't have blown the field apart.
> >
> > Racing in strong tailswinds are brutal - much more condusive to fields
> > exploding than still air or headwinds
>
> Why do you conclude that?
Either because he's done it, or because he has a brain. Since it's JT, I
suspect the right answer is both.
Tailwinds reduce the advantage of a peloton versus a solo rider, and
confound the peloton in subtler ways. The lead riders are effectively
"sheltered" from the benefits of the tailwind, thus making the relative
efforts of the lead rider and the pack even more disparate than usual.
The effect is that a rider who jumps off the front of the pack can do so
with less effort than usual, while the rider who stays at the lead of
the pack has to put out more (relative) effort than usual.
There's also some daffy bunching-up effects, since the guys at the very
back of the pack are doing even less work than usual, and getting popped
off the back of the pack is slightly less consequential than usual, and
less likely since the ramp-up in drag is less than usual.
It may be easier to understand by examining the effect of a headwind:
the higher wind-speed means that the draft is more effective
(paceline/peloton drafting advantage rises rapidly with increasing
cyclist speeds, and a headwind effectively increases the "airspeed," to
borrow a flying term). The peloton compensates with shorter pulls at the
front (or, alternatively, the lead riders are just burning more matches;
either way, spending time in the lead is especially costly), and the
cost of trying an escape is higher, because the power-increase required
to solo off is greater.
I punched in some numbers into this (admittedly crude) calculator:
http://www.exploratorium.edu/cycling/aerodynamics1.html
Start with a 150 pound cyclist (obviously a rouleur type) and 0 slope.
25 mph, 0 wind, 184 Watts required
27 mph, 0 wind, 258 Watts required.
Now, some wind:
24 mph, 10 mph wind, 462 Watts required. Wow.
26 mph, 10 mph wind, 548 Watts required.
And of course, you probably can still get to 24 mph in a heavy headwind,
because the guys at the front take short (hard) pulls, and rest in the
pack, where the draft largely shelters you from the headwind. In other
words, your at-the-front efforts are very high, but you still have
nearly the same (minimal) power needs while you're resting in the draft.
So the pack doesn't slow down a lot, but more people contribute to the
work, or you might get a little less rest, but it feels great.
Humans are good at sprint-rest cycles like this. Lots of pro riders can
do 1-minute 500-Watt efforts every ten minutes for hours at a time. But
Willett notes that 376 Watts for an hour is good enough for a gold-medal
Olympic TT.
Compare to a solo attacker in a headwind, who must take on a
all of the burden of this sprint-level effort, and doesn't get to rest.
In other words, they're doing that solo TT. So let's go straight out and
assume that they're putting out 376 Watts. In a 10 mph headwind, that
equates to a solo speed of about 21-22 mph.
Any guesses as to how good a 10-man paceline would have to be to
maintain 23 mph (~37 km/h) in a 10 mph headwind? I don't have a
calculator for it, but this sounds like a Cat 3 effort. And they could
catch David Millar trying to solo away from them.
Okay, so the Cat 3's are clearly doping, (cf Millar Line), and even
TT-specialist Millar probably has enough sprint (or at least 10-minute
power) to take the victory, but a serious solo effort will never work in
these conditions.
So that's for a head wind. A tail wind has roughly the opposite effect.
--
Ryan Cousineau
[email protected] http://www.wiredcola.com/
"My scenarios may give the impression I could be an excellent crook.
Not true - I am a talented lawyer." - Sandy in rec.bicycles.racing
