Franklin said:
Now this is more like it. My thanks for the great effort. It gives an extensive range of wattages.
Yes, although I think those with CdA>0.2m^2 are the most likely.
Franklin said:
I assume you used weights from the official TdF medical check?
No, I used Flecha's mass as recorded in his power meter file.
Evans I used a web search for that, happy to have his verified in another matter - I have assumed 7.0kg less than Flecha.
What matters is not so much the absolute power/mass/aero drag values, but the differences required to ride 4:13 faster.
Franklin said:
How did you find out the CdA of Flecha?
That would take quite some time to explain. I used the method of Virtual Elevation modeling using Flecha's power meter file to that equate against an actual elevation profile.
Certain pairs of Crr & CdA will generate an elevation profile based on power & speed data that closely matches the actual elevation profile:
I won't go into detail here as to how it works. Where the virtual and actual elevations deviate means that there variations in things like wind, or localised changes in CdA (such as sitting up or standing when climbing) etc, but it's mostly wind.
In that sense the VE model takes into account localised variations. Sometimes there are small discontinuities due to braking.
I then use the same Virtual Elevation model to determine what it would take to ride that course under those same conditions. This is done by segmenting the course into small chunks of variable distance and gradient, and applying the rider's actual power data for those same segments to compare theoretical ride time to actual.
I then make any minor adjustments to assumptions to tweak it accordingly to match actual ride time. From then on it's a matter of comparing what it takes to go faster or slower by the set amount (in this case 4:13) by adjusting any of the variables I so please (power, mass, Crr ,CdA, air density, wind, drivetrain efficiency). By putting in Cadel's mass, we can then hold that constant, and hence change power to show different W/kg and hence calculate the CdA or W/m^2 required to ride that 4:13 faster.
For a fixed mass and ride time, if W/kg goes up, it means the rider is less aerodynamic. I am quantifying by how much for that specific course.
Franklin said:
I'm amused you come with a range of CdA's and extremes you encountered as this only shows that it differs between individuals. This is just one of the reasons why I dismiss mr. Coggan's insinuations.
Well IMO, the CdAs required to ride 4:13 faster (or in case of Martin 4:20) suggest to me that Andy's initial swag wasn't that far out. If I had to make my best estimate, I'd say more likely 5.9-6.0W/kg.
6.2W/kg still provides a totally plausible CdA value for Evans (and his set up) compared to Flecha.
Franklin said:
1. It does not answer the "was the weather exactly the same" as the wind speed varied from 8 to 22 kmh and there was some rain reported.
2. The efficiency questions of Flecha's riding
3. I'd say the 8 kg for a full TT kit is pretty optimistic.
1. No, although looking at the weather history on that page, it didn't appear to change all that much and the differences are reduced a bit because of the loop nature of the course. Point to point courses are more problematic in that respect.
2. Well that's an interesting question. It just so happens that the modeling I use was actual designed to measure "pacing efficiency", but it has other uses like what I'm doing here. So I ran Flecha's file through the pacing model.
I came up with a pacing score of 0.989 (I have a discussion paper I wrote which explains all this), but basically that ranks Flecha's ride as excellent pacing. World best pacing scores are 0.992-0.995.
1.0 is theoretical perfect pacing (doesn't happen).
It means that if Flecha had paced at world best standard, he could have saved about another 15 seconds for the same physiological effort. This is a measure of dosing out his effort slightly differently on that course under those exact same conditions. It isn't a measure of technical effectiveness.
So better pacing I'd suggest could only account for
at most 15 of the 253 seconds difference between Flecha and Evans.
3. Perhaps, but I have applied the same assumption to both riders.
On that course, if Flecha's equipment was say 1kg heavier than Evans', that would account for about a 9 second difference in the calculations, or about 2 watts.
Franklin said:
Which brands did they use, as in TT's often rebadged speciality gear is used. I'm wondering about the aerodynamics/weight between a Pinarello versus a BMC (Walser?) bike.
I discussed the weight differences above. This aero difference isn't all that relevant, since this is accounted for by the calculation of the W/m^2 required to go faster. That's the point, to ride faster, Evans (and Martin) had to be more aerodynamic.
If Evans had Flecha's aerodynamics (which he doesn't), then he'd require (on this course) around 6.9W/kg to ride as fast as he did. Evans is lighter and smaller, and so naturally has a lower CdA. The rest of the improvement is naturally being more aero shaped, better bike position and possiblly equipment.
Franklin said:
A few percent (points) make a difference if added with the other questions.
Of course, this is an academic exercise, however I am making relative comparisons, rather than being concerned with the absolute numbers.
Franklin said:
Considering over 6.0 watt per kg is seen as suspicious.
Is it?
Franklin said:
Had Mr. Coggan said: "The wattage per KG could be anywhere between Lemond's and Lance, so I would use caution seeing any changes" it would have been a lot less controversial.
Saying in the clinic in this exact topic ''not much seems to have changed since LA's day'' is something different. The context is quite clear. Considering mr. Coggan's stance on Lance I'm not surprised he leans towards the "not much changed" side.
This is what I saw. Dr Coggan said nothing about Lemond or Lance or their day. I think some are reading things that just ain't there.
acoggan said:
Flecha's TT = ~400 W/~74 kg = ~5.4 W/kg.
All else being equal, he would have had to sustain ~460 W (~6.2 W/kg) to challenge for the win in the TT.
acoggan said:
Hmmm...thinking about it a bit, that certainly suggests that things haven't changed all that much.