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  #1131  
Old 04-08-12, 18:14
FrankDay FrankDay is offline
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Originally Posted by sciguy View Post
Frank are you really positive that I'm wrong on the first one? Would you please post a side view of the upper thigh of a short crank user being in the wind shadow created by the shoulders with the rider in a sustainable position where they can see up the road for at least on hour if not several.
You seem to have forgotten that one of your reasons for advocating the shorter cranks is so that the rider isn't so scrunched up in a tight ball IE the raised thigh is more extended. Can't have it both ways here....

Interesting to be pronounced wrong before the test has been run. No bias at work here

Hugh
Well, in the video I did and linked to in the first post of this thread I used an animation program I have to demonstrate how the legs move into the wind shadow of the shoulders. And, I could also do so with the pictures that I took for my "aerodynamic musings" essay but didn't use (if I have some time I will try to do that). The issue is the shape of the legs. If the seat is moved up, something back there is moving into the wind shadow of the shoulders which do not move. If one is really high, it is the pelvis, as one gets lower in front it is the "exposed" part of the thighs and the part that moves into the wind shadow is the widest part of the leg. So, even though the upper leg is somewhat "more exposed" because the foot moves down the total area exposed is less because the part moving down is the lower leg and ankle, the narrowest part of the leg, and the part moving up into the wind shadow, is the thigh, the widest part of the leg. Since the amount of movement up and down is the same, more frontal area moves into the wind shadow than moves out so the total area exposed to the wind has to be reduced.

I am not declaring your overall prediction to be wrong, I simply declared your statement that the total exposed area of the leg remained the same to be wrong. I was simply giving you my reasons as to why my prediction is going to be somewhat different from yours. If your prediction is more correct then I will have to revise my thoughts as to what is going on because shape will at some point become more important than frontal area.
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  #1132  
Old 04-09-12, 06:39
sciguy sciguy is offline
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Originally Posted by FrankDay View Post
Well, in the video I did and linked to in the first post of this thread I used an animation program I have to demonstrate how the legs move into the wind shadow of the shoulders. And, I could also do so with the pictures that I took for my "aerodynamic musings" essay but didn't use (if I have some time I will try to do that). The issue is the shape of the legs. If the seat is moved up, something back there is moving into the wind shadow of the shoulders which do not move. If one is really high, it is the pelvis, as one gets lower in front it is the "exposed" part of the thighs and the part that moves into the wind shadow is the widest part of the leg. So, even though the upper leg is somewhat "more exposed" because the foot moves down the total area exposed is less because the part moving down is the lower leg and ankle, the narrowest part of the leg, and the part moving up into the wind shadow, is the thigh, the widest part of the leg. Since the amount of movement up and down is the same, more frontal area moves into the wind shadow than moves out so the total area exposed to the wind has to be reduced.

I am not declaring your overall prediction to be wrong, I simply declared your statement that the total exposed area of the leg remained the same to be wrong. I was simply giving you my reasons as to why my prediction is going to be somewhat different from yours. If your prediction is more correct then I will have to revise my thoughts as to what is going on because shape will at some point become more important than frontal area.
OK, I went back and looked at the stick figure again. When you say wind shadow of shoulders it would appear you really mean to say upper arms at least in regards to that figure. Interestingly you very distinctly say and label "Lowering the knee here" to show the top of the stroke.
'
So let's look at this a sightly different way. Say we start with someone riding 170mm cranks with a nice horizontal back and compare their frontal area to someone riding 105mm cranks also with a nice horizontal back. Who has a larger frontal area? I think the one with the more extended raised leg will so long as each ride has a horizontal back. Now at this point you're going to pipe in that the rider with the 105mm cranks can lower their bars even farther while I would contend that unless they can see out the top of their skull this is an unridable position of any length of time. Perhaps the real question here should be what is the more important limiter in time trial position, how compacted the rider's hip angle is or their ability to use their neck to see down the road safely.

I see merit in doing wind tunnel testing on this but it will be very important to access the results in regards to whether the the positions tested can truly be ridden for significant lengths of time.

YMMV,

Hugh
  #1133  
Old 04-09-12, 15:20
FrankDay FrankDay is offline
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So let's look at this a sightly different way. Say we start with someone riding 170mm cranks with a nice horizontal back and compare their frontal area to someone riding 105mm cranks also with a nice horizontal back. Who has a larger frontal area? I think the one with the more extended raised leg will so long as each ride has a horizontal back. Now at this point you're going to pipe in that the rider with the 105mm cranks can lower their bars even farther while I would contend that unless they can see out the top of their skull this is an unridable position of any length of time. Perhaps the real question here should be what is the more important limiter in time trial position, how compacted the rider's hip angle is or their ability to use their neck to see down the road safely.
Well, that isn't the question I am asking and I don't know the answer to that question. I would guess that two riders with the same horizontal back would have similar frontal area regardless of crank length and it might be possible that the shorter crank length would have a larger frontal area because the TDC leg is lower. But, the question I am asking is take that person with a flat back on 170 cranks and then see what happens when he goes to shorter cranks. In this instance his back will be "different" whether flatter or slanted head down some. This situation should lower his frontal area and, hopefully, his overall drag. So, the issue is not trying to compare two different riders but to let any single rider better understand what might possibly happen to him/her with this change.

Here is the problem I am trying to solve. if everyone could ride their time-trial bike looking like Levi Leipheimer or their road bike looking like Tom Boonen this would not be a huge issue. There might still be some benefit to going lower but I suspect there won't be much. But the vast majority of bicycle racers (including other pros) don't come anywhere close to these positions and we have to ask why. I suspect it is a flexibility/power problem. Shorter cranks seem to solve this problem.
Quote:

I see merit in doing wind tunnel testing on this but it will be very important to access the results in regards to whether the the positions tested can truly be ridden for significant lengths of time.

YMMV,

Hugh
Unless one has the information as to whether it might be worthwhile trying to make this change it seems silly to try. Perhaps that is why no one has tried in the past. And, of course, to be useful one does need to actually train themselves to race in this aerodynamically improved position. The lower one is the harder it is on the neck. This may not be a big deal for a 3k track race but it is for a 5 hour Ironman or 8 day RAAM race. Therefore, each person will have to take this data and see if it will be worth the work necessary to gain this advantage for the kind of racing they do. It is similar to using PowerCranks. If you aren't interested in doing the hard work necessary to gain the advantage (assuming I demonstrate an advantage) then I suggest you don't even try (and I suggest that you prepare to get used to losing regularly to those who do make the effort).
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Last edited by FrankDay; 04-09-12 at 15:23.
  #1134  
Old 04-09-12, 18:34
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If you aren't interested in doing the hard work necessary to gain the advantage (assuming I demonstrate an advantage) then I suggest you don't even try (and I suggest that you prepare to get used to losing regularly to those who do make the effort).
Such comments carry as much weight as: "scientific studies have shown" and "nine out of ten Dentists use". More marketing jibberish rather than real science.
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  #1135  
Old 04-09-12, 20:02
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I am making a plea to Frank: For your research and data to be credible, you need an independent person to design your experiment based on your aim(s) and then you need to provide an independent person with the raw data. Sciguy seems to be putting his hand up (?) and has the credibility, knowledge and skillset to be able to design this experiment. Unfortunately Fergie has failed to meet the challenge, but hopefully Frank you will not. Please Frank, in the name of stopping this merry-go-round, minimize your experimental biases and let someone with a biomechanical/sports physiology background design your experiment.
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  #1136  
Old 04-09-12, 20:05
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Sure you meant "Fergie never accepted the challenge".

Still waiting for any data that shows the importance of crank length on cycling.
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  #1137  
Old 04-09-12, 20:57
FrankDay FrankDay is offline
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Originally Posted by elapid View Post
I am making a plea to Frank: For your research and data to be credible, you need an independent person to design your experiment based on your aim(s) and then you need to provide an independent person with the raw data. Sciguy seems to be putting his hand up (?) and has the credibility, knowledge and skillset to be able to design this experiment. Unfortunately Fergie has failed to meet the challenge, but hopefully Frank you will not. Please Frank, in the name of stopping this merry-go-round, minimize your experimental biases and let someone with a biomechanical/sports physiology background design your experiment.
First, this is not a research project as I only have 2 hours. I am simply trying to gather data to answer my own intellectual curiosity and to help me to better advise customers beyond my thought experiment and anecdotal reports. It is more a proof of concept than an actual research study. As I told the aero guru at the wind tunnel I hoped what I am doing here might stimulate him or someone at that university to do a real study to look at this to better prove our findings, presuming they are interesting. Second, while the basics of what I want to look at will be my idea the actual data will be gathered by the wind tunnel guy. The concept is pretty simple. Change one thing and see what happens to the drag. Not a difficult experimental design. Anyhow, since he has done this for some of the best cyclists in the world I presume his data will be as good as possible under the circumstances. Third, I, of course, will interpret the data as I think best but I intend to also present it in "raw" form for pretty much anyone to check my work if they disagree with the findings. All I ask of Coach Fergie, since we can pretty much assume he won't like the results, is he show his work. Hopefully, if the data is what I think it will be, this effort will encourage others to repeat this work using a "better" experimental design.
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  #1138  
Old 04-09-12, 21:00
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Please Frank, in the name of stopping this merry-go-round, minimize your experimental biases and let someone with a biomechanical/sports physiology background design your experiment.
Just out of curiosity, what exactly do you think my background is? If we are looking at aerodynamics wouldn't an engineering background be useful also?
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  #1139  
Old 04-09-12, 22:39
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One aero negative created by the use of shorter cranks is an increase in the exposed average leg length at any given moment. With each crank length the fully extended leg would always expose a similar amount of area but the less retracted upper leg will expose more area when using shorter cranks. This may well represent a non-trivial addition to drag.
Here is another way to think of what shorter cranks do to the frontal area. The total frontal area of each leg varies with crank position. But, because we are dealing with a reciprocal/rotary motion we can look at the mean or average value for analysis. The mean/average would be when the legs are at 3 and 9 o'clock. Well, when they are in this position the feet are at the same horizontal height compared to the BB regardless of the crank length but the rear end is still pushed up more into the wind shadow of the torso as will the be the upper legs when changing to shorter cranks and keeping fit the same at BDC. In other words, the feet are the same but less leg is exposed to the wind. If we define frontal area as the area directly exposed to the wind and if we start with a typical rider bike fit, the only way the total frontal area can go with this change is down.
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  #1140  
Old 04-09-12, 23:37
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OK, I'm pretty sure where everyone is coming from now.

Frank - I understand the desire to satisfy your own intellectual curiosity and use this forum as a think tank to throw around ideas. I also understand the difficulties in getting a project, whether it be a pilot study or a research project, funded and completed. However, I am a little frustrated because I can see no resolution in sight.

Coach Fergie - Unfortunately I cannot understand your retinence to engage Frank on a more intellectual and academic level. I see the discussions between sciguy and others with Frank and for the most part they seem very reasonable and informative. However, you don't participate at the same level, whether by choice or inability, and prefer to resort to negative and unsubstantiated comments, such as manipulating data.

So, that's me signing off this thread. I gave up watching Days of our Lives cold turkey when at university and realized how much of my life I had wasted watching such a train wreck, and now I can put this thread in the same basket. I am sure I will check in a year's time and nothing will have changed. Enjoy!
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