#21
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Landis' aerobars
"Tom Kunich" wrote in message ink.net... No, what it might mean is that all the photographs we've seen were of riders sitting up for turns, ending their wind tunnels tests or that sort of thing. In other words, the teams didn't want photos of their "working" positions showing. Why should they spend money for testing and then throw the majority of it away by showing the competition? Since when do teams have control over whether photographs of riders in turns or in their tucked position are published? |
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#22
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Landis' aerobars
Ronald wrote:
I've seen three photographs now of the Rabobank guys and unless those photographs were purposely staged to show the wrong sort of positions, I can't see how those positions could possibly result in good aero results. Rasmussen (also Rabobank) uses a position like Landis: http://www.cyclingnews.com/photos/20...ikes4/IMG_0469 Yeah, but that's just in an effort to keep on the fricken bike! |
#23
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Landis' aerobars
Carl Sundquist wrote:
"Tom Kunich" wrote in message ink.net... No, what it might mean is that all the photographs we've seen were of riders sitting up for turns, ending their wind tunnels tests or that sort of thing. In other words, the teams didn't want photos of their "working" positions showing. Why should they spend money for testing and then throw the majority of it away by showing the competition? Since when do teams have control over whether photographs of riders in turns or in their tucked position are published? I was thinking more along the lines of photographers taking more "interesting" pictures of riders full faces and not of someone in a full tuck etc. |
#24
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In article ,
"Steve Freides" wrote: "Ryan Cousineau" wrote in message ... In article , "Steve Freides" wrote: "jeremy" wrote in message oups.com... Steve Freides wrote: I don't think this is a one-size-fits-all kind of thing - there are tradeoffs wherein a more aero position simply doesn't let you pedal or breath as well and results in an overall deficit in performance. It looks like Menchov's back is already flatter than Landis', i.e., Menchov's hips are higher in relation to his shoulders than Landis'. Looks like Menchov's legs are quite a bit longer than Landis'. -S- Interesting comments - Thank you but this is nothing new. .so how to those without access to a wind tunnel decide which position is best for them (besides the odvious Time Trial & Error approach)? To a first order, an amateur can get the "right" TT position by taking a picture and using it to measure (and minimize!) their frontal area, and then make some educated guesses about the aerodynamics. I think this is a bit too much of an oversimplication. Look, e.g., at this picture of Ullrich from earlier this year: http://www.cyclingnews.com/photos/20...e065/Par734507 He is clearly _not_ going for a small frontal area - he looks a lot like the Menchov pictures. This photo raises questions, but perhaps as many for you as for me: -the caption says Jan is approaching the finish. Was he making a finishing push, and thus not entirely in his usual tuck? -where are Jan's hips? Would getting his chest lower result in an appreciable reduction in frontal area, or just make him less comfortable? What's most aerodynamic for some may be to focus on total frontal area, but Jan's positioning suggests different thinking. I don't imagine one of the world's best time trialists, well, you can finish that sentence for yourself. I did say "to a first order", weasel words meant to express something a little more complex: the coefficient of drag (essentially the measure of how aero a shape is) and frontal area are both fundamental to the drag of an object (not as important as velocity, but reducing speed is not an option. using a few tricks, amateurs have a half a chance at making accurate measurements of their frontal areas in various positions. If one assumes that they have access to a power measurement system, one can even check for relative power losses in each position. Actually, if one didn't have a power measurement, but did have a hill that was steep, but not so steep as to take the rider out of their tuck, you could set up a test which would compare power outputs per position, with wind effects minimized. The problem is that for coefficient of drag measurements (actually, total drag measurements), you can't beat a wind tunnel. So amateurs are reduced to copying the pros, or finding a nearby indoor velodrome and doing some timings to check speed for a position given constant power output across multiple positions (thank you SRM). One compromise which is consciously made is balancing aerodynamics against power loss for any given position, and similar physiological issues. Lance famously experimented with a TT bike known as "the narrow bike" which had to be abandoned because although it demonstrated a measurable aero advantage, he couldn't comfortably ride it. I wouldn't imagine one of the world's best time triallists would drop E at a party and fail a drug test, but... You don't need a Weatherman to know which way the wind blows ... -- Ryan Cousineau http://www.wiredcola.com/ "I don't want kids who are thinking about going into mathematics to think that they have to take drugs to succeed." -Paul Erdos |
#25
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Landis' aerobars
Ryan Cousineau wrote:
So amateurs are reduced to copying the pros, or finding a nearby indoor velodrome and doing some timings to check speed for a position given constant power output across multiple positions (thank you SRM). Given the inherent measurement characteristics of on-bike power meters, I don't think runs at constant power is the best way to do it at all. |
#26
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In article ,
"Robert Chung" wrote: Ryan Cousineau wrote: So amateurs are reduced to copying the pros, or finding a nearby indoor velodrome and doing some timings to check speed for a position given constant power output across multiple positions (thank you SRM). Given the inherent measurement characteristics of on-bike power meters, I don't think runs at constant power is the best way to do it at all. Since you're the guy who published the Rosetta Power Files, I cede the field. What's the issue, and what's the better way? -RjC. -- Ryan Cousineau http://www.wiredcola.com/ "I don't want kids who are thinking about going into mathematics to think that they have to take drugs to succeed." -Paul Erdos |
#27
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Landis' aerobars
"Ryan Cousineau" wrote in message
... In article , "Steve Freides" wrote: "Ryan Cousineau" wrote in message ... In article , "Steve Freides" wrote: "jeremy" wrote in message oups.com... Steve Freides wrote: I don't think this is a one-size-fits-all kind of thing - there are tradeoffs wherein a more aero position simply doesn't let you pedal or breath as well and results in an overall deficit in performance. It looks like Menchov's back is already flatter than Landis', i.e., Menchov's hips are higher in relation to his shoulders than Landis'. Looks like Menchov's legs are quite a bit longer than Landis'. -S- Interesting comments - Thank you but this is nothing new. .so how to those without access to a wind tunnel decide which position is best for them (besides the odvious Time Trial & Error approach)? To a first order, an amateur can get the "right" TT position by taking a picture and using it to measure (and minimize!) their frontal area, and then make some educated guesses about the aerodynamics. I think this is a bit too much of an oversimplication. Look, e.g., at this picture of Ullrich from earlier this year: http://www.cyclingnews.com/photos/20...e065/Par734507 He is clearly _not_ going for a small frontal area - he looks a lot like the Menchov pictures. This photo raises questions, but perhaps as many for you as for me: -snip- No. I figure this is something for pro's and their hired guns, and most of the rest of us should just go out and pedal as hard as we can. I realize many folks here race but I'm not one of them - I ride, and I enjoy following bike racing, but that's as far as it goes for me. When I want to be aero, I grab my bars near the stem and hunker down and that's good enough for me. -S- |
#28
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Ryan Cousineau wrote:
Robert Chung wrote: Given the inherent measurement characteristics of on-bike power meters, I don't think runs at constant power [across varying positions] is the best way to [estimate CdA] at all. What's the issue, and what's the better way? An example of a constant power test is a roll-down test: the power is fixed at zero. It turns out that even tiny amounts of wind and tiny amounts of grade can screw up these tests. Most people try this by rolling down a hill, but Wilson's MIT students used to try to do roll-down tests on the flattest and least windy venues they could find: down the long linoleum hallways of the buildings.The precision was affected by whether doors along the hallway were open or closed, as well as the skill of the rider. Even if you have an on-bike PM, most people don't do constant power runs on the road because the PM display is too jumpy and there's too much latency to use as a proper control. Instead, most people think that the best way to estimate CdA with a power meter is to do constant speed runs on flat windless surfaces and then solve algebraically for the drag. They do this because constant speed reduces the acceleration to zero (which simplifies the calculation). However, it's hard to find venues that are both flat enough and windless enough (even the hallways at MIT), and the on-bike PM display is still a little too jumpy for control. I have data files from guys who've tried just this on the road and they end up with very poor estimates of CdA. So, from a statistical analytical point of view, it's better to bite the bullet and keep track of the accelerations. Vary the speed and power. It's more of a pain but the estimates are better. |
#29
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Landis' aerobars
On 2006-06-04 22:23:05 -0400, "Robert Chung" said:
Here's how Landis set up his aerobars: http://www.cyclingnews.com/photos/20...phine06-pg-012 For comparison, here's Menchov: http://www.cyclingnews.com/photos/20...phine06-pg-009 And Landis has been using Kraig Willett (who used to hang around rec.tech a lot) to get to that position... http://www.cyclingnews.com/tech.php?...es/levi_tunnel Here's what he does for fun: http://biketechreview.com/stems/extremeload.htm#Updated! |
#30
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Landis' aerobars
In article ,
"Robert Chung" wrote: Ryan Cousineau wrote: Robert Chung wrote: Given the inherent measurement characteristics of on-bike power meters, I don't think runs at constant power [across varying positions] is the best way to [estimate CdA] at all. What's the issue, and what's the better way? An example of a constant power test is a roll-down test: the power is fixed at zero. It turns out that even tiny amounts of wind and tiny amounts of grade can screw up these tests. Even if you have an on-bike PM, most people don't do constant power runs on the road because the PM display is too jumpy and there's too much latency to use as a proper control. Instead, most people think that the best way to estimate CdA with a power meter is to do constant speed runs on flat windless surfaces and then solve algebraically for the drag. They do this because constant speed reduces the acceleration to zero (which simplifies the calculation). However, it's hard to find venues that are both flat enough and windless enough (even the hallways at MIT), and the on-bike PM display is still a little too jumpy for control. I have data files from guys who've tried just this on the road and they end up with very poor estimates of CdA. So, from a statistical analytical point of view, it's better to bite the bullet and keep track of the accelerations. Vary the speed and power. It's more of a pain but the estimates are better. Thanks for the answer. That's just good stuff. And it reinforces my violent predjudice against TTs for amateurs . Now, is there any way we can use this data to fight off the arguments of the HPV set? There's another violent predjudice I need confirmed. Everything that's wrong with usenet, -- Ryan Cousineau http://www.wiredcola.com/ "I don't want kids who are thinking about going into mathematics to think that they have to take drugs to succeed." -Paul Erdos |
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