Sub 20 10TT - Power needed?

Alex_Simmons/RST

meanredspider wrote:

Yes - traffic makes quite a difference. So, forgiving the fact that it's a Strava segment, but if I climb the Kessock Bridge on the side WITH the traffic I'm so much faster than if I cross on the side AGAINST the traffic (for anybody that thinks I've lost my marbles and started riding on the wrong side of a busy dual carriageway, both are on segregated cycle paths separated from the traffic only by 3' of Armco (5' now)). I would think a steady stream of trucks (like the testers who ride on the A14 near Cambridge heading towards Felixstowe and Ipswich docks must see) must make quite a difference.

I know this is about time trials, but I wrote about the impact of wind on climbing speed, and how that can affect estimates of power based on speed or vertical ascent methods.

This for a 5.8W/kg rider on an 8% grade:



Even on hilly terrain air movement makes a substantial difference.
http://alex-cycle.blogspot.com.au/2013/07/windbags.html

bahzob

Alex_Simmons/RST wrote:

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Once there is any air movement then the precision of field aero testing drops, meaning that one can probably determine large changes in aerodynamics OK (and which are usually pretty obvious anyway), but once you start refinements (aero optimisation really is an iterative process of working on a lot of small details) you need benign conditions.

Put in this way - on an indoor velodrome a rider riding on the opposite side of the track is sufficient to affect the data such that I would toss it. Unless of course I was testing the impact of having a rider on the opposite side of the track.

Very interesting and explains why the limited aero testing I have done hasn't really yielded any useful data.

Alex_Simmons/RST

I probably should have said "Once there is any unmeasured or unaccounted for air movement" but yes, it doesn't take much wind disturbance to make interpretation problematic.

One of the cool things about quality power meter data is that it is sensitive enough to reliably and repeatedly detect such things, but with that also comes a need for sound protocol and analysis methodologies.

Many more people have the former than apply the latter.

bahzob

Alex_Simmons/RST wrote:

I probably should have said "Once there is any unmeasured or unaccounted for air movement" but yes, it doesn't take much wind disturbance to make interpretation problematic.

One of the cool things about quality power meter data is that it is sensitive enough to reliably and repeatedly detect such things, but with that also comes a need for sound protocol and analysis methodologies.

Many more people have the former than apply the latter.

Thanks again for your info Alex, it will certainly help avoid wasting time. In last couple of weeks of good weather in 2014 I spent lots of time trying to get more "aero". I tried various methods: roll down tests, trying to measure frontal area, doing short laps of my TT course and Chung analysis.

The end result was largely a mess. Nothing really made much sense. What you have said explains this, its very likely that the confounding factors of traffic and other local conditions swamped the results.

Anyway I decided i was putting the cart before the horse, there was no point being "aero" if it meant losing lots of power and being thoroughly uncomfortable/miserable.

Hence why now I am just concentrating on being able to ride comfortably in a TT position at "normal" power.

I'm hopeful this will yield results, so when the weather gets better I'd like to try doing some more aero tests again. I'd be interested if you can point me in the direction of anything you think resembles best practice in this area.

RChung

Work on "practice" before obsessing about "best practice."

http://anonymous.coward.free.fr/wattage ... ations.pdf

bahzob

RChung wrote:

Work on "practice" before obsessing about "best practice."

http://anonymous.coward.free.fr/wattage ... ations.pdf

Yes take your point. And in my case at least put the cart before the horse, not much point working on aero position until at least established a comfortable base point.

Still its handy to know that you are on this forum. I'll be doing some more testing later on so if got some questions with real data will post them.