56kh ITT

[hrotha]

With echelons, once you lose the wheel in front of you it doesn't really matter how much of a beast you are. Come on, this is cycling 101.

 

[LaFlorecita]

Re:

With echelons, once you lose the wheel in front of you it doesn't really matter how much of a beast you are. Come on, this is cycling 101.

You should check the youtube link posted in the Sagan thread

 

[hrotha]

ASO took down the link, but assuming it's the official race video of Sagan closing the gap to avoid Contador & co. being caught like Nibali, and not some amateur video of Sagan motorpacing later on ( ): well, yeah, there's a moment when being a beast makes closing the gap possible, but that's only if you happen to be right where the gap is being opened. That's presumably not what happened to Dennis.

 

[oldcrank]

Re: Re:

Yes but Olympics were in September in Sydney, not Adelaide in the summer. You can't assume conditions would have permitted the same time to be ridden.

... snip...

snip...

When you peruse the list of names, lots of roadie sprint type and track endurance guys there. It's never been a pure IP rider's event. In many years the chosen IP rider was not in the TP team.

yeah, you'd be able to tell me what time Bobridge's WR in del Monte in Adelaide in Jan works out at if I give u he air pressure and humidity and the temperature. what did he ride? 4'11" or 4'09" or something in that vicinity? what is the neutral condition?

yeah, we know Jan, Adels, del Monte, is sooooooopa fast

Actually Bobridge's WR (4:10.x) was set in Sydney at DGV in February 2011 and it was ridiculously hot. I know/recall because I was racing at the same championships.

And the young man whom this thread is about rode
a 4:13 that day, just before Jack took to the track.

 

[blackcat]

Re:

He is not the rider the top 3 TTers are(Martin, Cance, Domoulin). Those 3 are still in the top 5. He got lucky with his start perhaps with wind, heat

well, he almost won Dauphine two years back did not he? what has Dumoulin done?

 

[Tommy79]

Re:

ASO took down the link, but assuming it's the official race video of Sagan closing the gap to avoid Contador & co. being caught like Nibali, and not some amateur video of Sagan motorpacing later on ( ): well, yeah, there's a moment when being a beast makes closing the gap possible, but that's only if you happen to be right where the gap is being opened. That's presumably not what happened to Dennis.

Seem to remember Cav saying a couple of years ago he put out more power making the split than he did winning the final sprint.

 

[jmdirt]

Re: Re:

what does his performance, or lack there of, on stage 2 indicate?

He got caught out in the echelons

but wait, this over the top TT rider is juiced up to the max, so if he can produce the TT he did, then why could he not keep up with this team a day later after a simple 15minute effort??

I didn't see the stage but that was my assumption. Wasn't Van Garderen and Van Avermaet the only BMC riders to make it? From what I saw it was Etixx and Saxo who drove the pace to break things up. Strong crosswinds would be like blood to a shark for their rouleurs and classics guys.

Contador got caught out in echelons in '09, as did Froome in '13, because it's about positioning and reading the race as much as anything else.

On the other hand, Brad McGee always said that he felt flat for a day or two after a really good prologue and he won one at all 3 GT's. It's the second stage, no one's had a chance to do anything completely mental yet.

I must have got the wrong impression from cyclingnews' article this morning...

Van Garderen and the bulk of his team were present and accounted for when the peloton split in the crosswinds, while Vincenzo Nibali (Astana) and Nairo Quintana (Movistar) both lost 1:28 by the time they crossed the line behind stage winner Andre Greipel. Dennis was unable to make the front group and BMC were caught in two minds as to whether they should press on or wait for Dennis, ...

That suggested he'd struggled to keep up...

Or that he was taking a nature break, getting a bike adjustment, adjusting his kit, was behind guys who didn't react... Missing an echelon doesn't mean that he struggled to keep up. Maybe the TT took some zip out of his legs, but he look just fine once the group he was in got organized.

 

[Catwhoorg]

Re: Re:

ASO took down the link, but assuming it's the official race video of Sagan closing the gap to avoid Contador & co. being caught like Nibali, and not some amateur video of Sagan motorpacing later on ( ): well, yeah, there's a moment when being a beast makes closing the gap possible, but that's only if you happen to be right where the gap is being opened. That's presumably not what happened to Dennis.

Seem to remember Cav saying a couple of years ago he put out more power making the split than he did winning the final sprint.

I recall that Cav comment, looked like it on the footage too. A real all out sprint to make the split

 

[42x16ss]

Luke Durbridge's SRM for the TT is available here:

http://home.trainingpeaks.com/blog/article/2015-power-analysis-tour-de-france-week-1

His file is showing that the parcours was indeed 400m short.

 

[Dear Wiggo]

Re:

Luke Durbridge's SRM for the TT is available here:

http://home.trainingpeaks.com/blog/article/2015-power-analysis-tour-de-france-week-1

His file is showing that the parcours was indeed 400m short.

tsk tsk started too hard tsk tsk ...

 

[Alex Simmons/RST]

Re: Re:

Luke Durbridge's SRM for the TT is available here:

http://home.trainingpeaks.com/blog/article/2015-power-analysis-tour-de-france-week-1

His file is showing that the parcours was indeed 400m short.

tsk tsk started too hard tsk tsk ...

lol

In any case if course was really 13.4km and not 13.8km, then 55.4km/h was really 53.8km/h, and that's 40W less average power required for Dennis.

13.4/13.8 = 3% error in distance. If that was a wheel speed sensor, that would be a silly large error in wheel circumference setting (>6cm). With GPS and corners, who knows what the error might be?

Over such a distance and speeds, every 100m of error in course distance ~= 10W error in power demand estimates.

 

[Catwhoorg]

Interesting that the course may have been significantly short.

 

[42x16ss]

As Alex said above, if that's a GPS rather than a wheel sensor then the figure could be out as GPS cuts the corners, especially at speed. Orica use SRM computers but I don't know if they use GPS or wheel sensors.

 

[Alex Simmons/RST]

Re:

As Alex said above, if that's a GPS rather than a wheel sensor then the figure could be out as GPS cuts the corners, especially at speed. Orica use SRM computers but I don't know if they use GPS or wheel sensors.

If Durbridge used a PC7 head unit then it can only be a wheel speed sensor.

In this start line photo it looks like a PC7 on his bike:

Looking at other photos of team riders in the TT, all I could see were PC7s.

 

[Jacques (7 ch)]

Re:

Luke Durbridge's SRM for the TT is available here:

http://home.trainingpeaks.com/blog/article/2015-power-analysis-tour-de-france-week-1

His file is showing that the parcours was indeed 400m short.

Machine calibration error.

 

[SeriousSam]

Alex, is there a good publicly available resource on the ins and outs of power estimation? I have a strong background in statistics but don't know any physics if that helps.

 

[Benotti69]

Re: Re:

Luke Durbridge's SRM for the TT is available here:

http://home.trainingpeaks.com/blog/article/2015-power-analysis-tour-de-france-week-1

His file is showing that the parcours was indeed 400m short.

Machine calibration error.

Bingo..........

 

[Alex Simmons/RST]

Re: Re:

Luke Durbridge's SRM for the TT is available here:

http://home.trainingpeaks.com/blog/article/2015-power-analysis-tour-de-france-week-1

His file is showing that the parcours was indeed 400m short.

Machine calibration error.

As I pointed out, to have a distance error of that magnitude from a wheel speed sensor would require the wheel circumference value used be wrong by ~6cm (which would be very unusual as entered circumference for most race tyres might be spread at most over a 15mm range, usually less), or for there to be a loss of data from the sensor. The latter is possible but when inspecting the data file on TP, there are no speed data drops shown.

Data files from others would assist validate.

 

[Alex Simmons/RST]

Re:

Alex, is there a good publicly available resource on the ins and outs of power estimation? I have a strong background in statistics but don't know any physics if that helps.

Well the maths of the physics is pretty well known. If you are estimating power from speed data of an individual, then all you need do is a sensitivity analysis on each of the inputs/assumptions used. The sensitivity of various inputs depends on the circumstances, e.g. a sensitivity analysis on climbs will result in a different outcomes than on the flats due to the large variance in the energy demand factors.

e.g. in this case a potential error of 2.9% (400m/13,800m) in course distance or speed value = an error in power estimate of 8-9% (~40W).

This paper is a good start on the maths of the physics:
http://content.lib.utah.edu/utils/getfile/collection/uspace/id/3039/filename/image

It's possible to have very good estimates, you just need to know all of the inputs. This is problematic outdoors when in a flat TT 85% of the total energy demand is required to overcome air resistance, it only take a tiny error in wind assumption for a large variance in power estimated from speed. This is why when we do aero testing, the wind conditions are known precisely.

Power estimates from speed on flat terrain are very sensitive to errors in rider speed and relative wind velocity, and are also sensitive to estimates of a rider's aerodynamics (frontal area and coefficient of drag), air density (temperature and air pressure), and rolling resistance factors.

You can generally get reasonable numbers for air density, and can somewhat normalise for CdA variances by quoting estimates as a ratio of power to aero drag, rather than power alone. That's why I often quote the W/m^2 number instead of the power number alone.

 

[Archibald]

Re: Re:

Van Garderen and the bulk of his team were present and accounted for when the peloton split in the crosswinds, while Vincenzo Nibali (Astana) and Nairo Quintana (Movistar) both lost 1:28 by the time they crossed the line behind stage winner Andre Greipel. Dennis was unable to make the front group and BMC were caught in two minds as to whether they should press on or wait for Dennis, ...

That suggested he'd struggled to keep up...

I was being factious about this claimed extraordinary TT'er not able to keep up the day after his supposedly phenomenal ride

That does not suggest he struggled.
An echelon consists out of as many people can take up space on the road. So with side wind echelons, there is a limit amount of people that can be in that echelon. All others are riding in the wind and not really getting the advantage of the echelon. So when a peloton of 200 riders breaks into echelons, mathematically, only about 20-25 can be in the first. If your name is not between those 25, it doesn't suggest anything, except that you weren't in the first 25 when the echelon was formed.

If there is a crash or someone who cannot follow in front of you, you have even more chance of not being in the first echelon. And still no suggestion of struggle.

I suggest some of you to ride a bit more in crosswinds before assuming and making up some very wild theories. The lack of facts, experience and even the simpliest of causal relationships / theories / common knowledge about racing, shown in many of the posts in the clinic, is astonishing.

settle petal, it was a piss-take on the claims of Rohan's doping... a tongue-in-cheek facetious "2+2" on some logic used. And based on an interpretation of events described.
Nothing to do with what you assume is my own riding/racing experience

 

[proffate]

this strava segment seems accurate (because it matches where Laurens Ten Dam and others were pedaling hard)

https://www.strava.com/segments/9845969?filter=overall

13.5km

 

[Dear Wiggo]

Some of the power figures next to those PT rider times are well dodgy.

 

[Alex Simmons/RST]

Re:

Some of the power figures next to those PT rider times are well dodgy.

For reference - the power numbers with the lightening bolt are from power meters, the rest are Strava guesstimates which are always going to be prone to large error. For those from a power meter, you then need to assess the validity of the power and speed/distance data depending on what was used to generate the data (e.g. a Stages v a well calibrated SRM, a GPS speed sensor vs a wheel speed sensor).

 

[Dear Wiggo]

DAMIANO CARUSO Jul 4, 2015 44.7km/h 180bpm 194W Powermeter - 18:14

Height: 1.78 m
Weight: 65 kg

 

[Alex Simmons/RST]

Re:

DAMIANO CARUSO Jul 4, 2015 44.7km/h 180bpm 194W Powermeter - 18:14

Height: 1.78 m
Weight: 65 kg

i agree there's some dodgy numbers there, just putting some context to the list for general reference. Like I said, one needs to assess the validity of the data whatever the source. Without seeing the actual file it's hard to say. Some are listed combined with more than the TT data.

But flipping through some of the individual Strava files, the distances listed vary a lot. 13.4 to 13.9km. Others are weird, multiple laps etc.