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SubscribeSilly Wind Tunnel Hate
Mon, 03/19/2007 - 11:00pm by alex
I did one last test before I broke down the drag rig. I tested a shoe (Diadora Club Racer) with and without a shoe cover, getting readings of 58 vs 61 grams. I found a site that claims a rider saves 10 seconds in a 40k TT at 30 mph by adding shoe covers, so I wanted to see if I could confirm this. One intriguing thing happened during this test. On every other test, the rig vibrated and oscillated like a broken down old jalopy, but on the shoe with shoe cover run, it was steady as a rock, completely inert. I guess it was a particularly aero shape, very free of turbulence.
So what does this mean?
Ok, if math makes your eyes glaze over, you might want to skip ahead. I took a crack at interpreting my results, and this is what I came up with. Feel free to critique.
First of all, my gram readings are pretty meaningless, since I'm not able to isolate the shoe or helmet with my rig. But I think the differences are significant. In other words, it doesn't matter that one is 58 and the other is 61. The critical number is the 3 gram difference. Since the shoe and my weights are at different distances to the hub, I have to apply a .564 conversion factor to account for differences in leverage. So each shoe experiences 1.69 grams more drag at 13 mph without a shoe cover, or 3.38 grams for two shoes. Next I chose a random CdA number of .2341, a number for a rider tested by Smiley at the San Diego LSWT. The rider was male, medium height, with full-on TT kit. At 13 mph, his resistance is determined by this formula:
Drag (newtons) = 1/2 x air density x CdA x velocity squared (meters/second)
With 1.18 for air density, I get 475.78 grams of drag for this rider at 13 mph. Using this formula in reverse for the same rider without shoe covers, with his total drag now 475.78 + 3.38, his CdA goes up to .2358. Now, back to that 30 mph 40k TT. The formula for power is:
Power (watts) = 1/2 x air density x CdA x velocity cubed
With our .2341 CdA, our rider will need to put out 332 watts to maintain 30mph (if we ignore other sources of resistance), and he'll take 49:43 to complete a 40k. Now, assuming this rider puts out the same power but without shoe covers, his speed now drops to 29.93mph, and his 40k time increases to 49:50, a 7 second loss.
You can put away the NoDoz now
Welcome back. Did you hit your forehead on the keyboard?
Ok, so some random site predicts a 10 second advantage for shoe covers, and I get a 7 second advantage with my test. Does that mean I'm pretty close? Does that validate my rig and testing procedure? I'm really not sure. But let's pretend it does and apply the same calculations to my helmet test. Since the Spiuk was the fastest, I'll make it the baseline.
Without back:
Uvex and Garneau +2.3 seconds
Garneau w/ visor +5.8 seconds
Rudy +23.3 seconds
Giro +26.8 seconds
With back:
Uvex +5.8 seconds
Garneau +8.2 seconds
Garneau w/ visor +10.5 seconds
Rudy +24.5 seconds
Giro +31.4 seconds
Now, it kinda blows my mind that buying the wrong helmet can cost you 31 seconds. So much so that I almost refuse to believe it. But Smiley told me that he tested 2 helmets at the SD LSWT and found a 15 second difference over the same parameters (30mph, 40k). I can't tell you which helmets they were, and in any case, I didn't test one of them, so I can't compare my results. But that does tell me that a 15 second difference is within reason.
Meanwhile, someone posted this link to last week's article, where someone tested the Rudy vs the Garneau at the SD LSWT. They reported a whopping 55 second difference between them! Watching the video, you can see that they did the run at 23 mph. I ran my Garneau and Rudy numbers at 23 mph, and I got a 22 second difference. Since they had the Rudy's tail way off the rider's back and the Garneau flush, I used my Rudy w/0 back number and my Garneau w/ back number, and the difference went up to 31 seconds. I'm sure if I had the Rudy angled down like they did the difference would be even greater.
Time for Hate
Wind tunnel data is incredibly hard to come by, and as much as that annoys me, I can understand why. If a guy pays around 1k an hour to get an edge on the next guy, you can bet he's in no rush to give that edge away. And from the wind tunnel owners' perspective, the less you know, the more time you'll have to spend in the tunnel, the more money they make. As for the manufacturers, well, only one of them's going to publicize test results, right? If nothing else, I hope you enjoyed the transparency with which I conducted these tests.
So where does that leave us?
I'll leave it up to you to decide if these results mean anything. In some ways I feel that my methods are validated, but I'm still very skeptical. One thing's for sure, I'm sticking with that Spiuk.
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Add a commentI NEED the name of the picture, please send me by a e-mail (por favor padrino, confio en que lo vas a ver)
man I just bought a Rudy TT Helmet in December. Maybe thats why Im close to 30 seconds off the winner every time.
I'll probably take you up on that, eventually. I only wish I hadn't listend to Schmalz... I got suckered by weather.com and ended up riding all the way up to tweed and back in a gritty downpour... and in the nude! damn nasty. Well, out of town for funeral and another missed weekend of racing. G.G.
Schmalz tries to mind control me into crashing whenever I ride.
What about testing an aluminum foil wrapped helmet, not only an aero advantage, it also saves you from mind control rays.
Pretty sure it works. It'll be in the next test for sure.
How bout testing a saran-wrapped helmet?? Me and fellow cheap asses would like to know.
How bout testing a saran-wrapped helmet?? Me and fellow cheap asses would like to know.
George, I defer to Schmalz for riding tips. But the best Smiley tip I got was to start in a big gear at a lower cadence, and start easy. Send me an email if you want more of his tips. Not being secretive, just don't want to act like I'm an expert.
No shaving whatsoever - the hair creates a turbulant barrier.
no head-shaving. gotta draw the line somewhere.
TT secrets:
Ride nude
No shoes - just covers
Helmet on backwards
forgot to identify myself (in keeping with personal policy): Sucky Master, c'est moi. G.G.
Yeah, Andy I know you've spent your time and energy on this, and are reluctant to give away your secrets, but as a journalist you do probably feel an obligation to your readers. So let us know what the quick and easy things we can do to shave time from our TT times (not to beat you, just so we don't embarrass ourselves).
I posted that hoping y'all would find the rediculous nature of the post. Apparently I didn't go far enough in the rediculousness, except maybe for Eugene who has latched onto a new set of factors in fluid dynamics. Can't wait to hear Eugene's Unified Theory of Time Trial Fluid Dynamics
Andy, you've thought about this stuff a lot: what in your opinion are, say, the four or five key (technical, not fitness) things a guy with little TT experience can do to maximize his TT performance, assuming he has clip-on aerobars but no other specialized equipment and just wants to try for decent personal best?
weed growing in the background of the shoe pictures?
Shoe covers are very midwestern
At 78 degrees, the saddle becomes a rectal thermometer.
What effect does the seatpost angle have? At 78 degrees you are positioned more over the bottom bracket and when compared with being out of the saddle it sort of makes sence in my mind that you would be able to transfer more power. Is this correct? It is however very difficult to test due to wind on 9W and getting tired etc.
If, while TTing, there is a temperature drop due to the wind chill, then we may have discovered a 4th component of fluid energy (elevation, pressure, velocity, wind-chill). Since the total energy in a fluid system is always constant, and since the air pressure and elevation don't change, the drop in temperature must be offset by an increase in velocity. Wind chill = more speed!
Ahh...., the return of the dreaded wind chill; may it never die. And, responding to anonymous, doesn't Adler always ride a smart race? (Is that the proper response? I'm a relative "new poster" to NYV).
thought you were going to say you take your rectal temperature while you were riding...whew...glad i was wrong
I use a thermometer to determine the power loss from my time trial position. When I am in my time trial position, I am going faster so I can tell the windchill using the themometer. The 10 degree drop in temperature more than offsets the 2% powerloss from the further forward and flatter TT position.
I have not ever really noticed a drop in power between the TT bike and the road bike. My intervals are usually within a few watts between bikes. I dont do a whole lot of training on the TT bike......around 20 hours last season. I do, though, make a sorta revving sound when I am on the TT bike so this may be aiding me in ways I'll never understand. N=1
Adler
No!
Do you think Adler will ride a smart race?
Get on a trainer and ride at a fixed cadence. Sit in various positions, wearing a heart rate monitor. See what happens to HR.
On my road bike for the same speed on the trainer my HR is 3-5 beats higher riding in the drops than a little more upright, on the hoods.
Quantifying this -- figuring out if the increase in effort from a lower position is worth it -- is a harder question. I think a good way to address this is to find a still day and do laps on a circuit like the Kissena velodrome at consistent HR and see which is quicker. Or do consistent speed and see which results in higher HR. Never tried this myself.
I was half afraid that I'd click through to this article and find out Andy had stolen a prosthetic limb in the name of science.
I was half afraid that I'd click through to this article and find out Andy had stolen a prosthetic limb in the name of science.
Votre sarcasme est juste le simulation de la sarcasme
Thanks Andy for your good efforts.
Now I will wear my shoe covers.
Piques my curiosity about cleaning up the bottom of the shoe though.
Perhaps a quick and dirty test by smoothly taping the pedal clip on the bottom of the shoe and see what improvement you get - shoud be more than the shoe cover.
Again, thanks for the info.
Cheers,
Neal
writing in a french accent is pretty much the most hilarious thing ever ventured. seriously, never, ever stop that. just keep doing it.
What is zis mayonnaise? Zat ees what je vais put on my pommes frites de la McDonald's, ou le BigMac iz not quite as bon sans le ketchup. Et plus...I have zee preference pour le Royale avec Fromage. Besides, eet is not a real mayonnaise but just zee SIMULATION de le mayonnaise. Eet is ze Kraft whip de la miracle! Putain!
I'm more aero than you
I have no real data, but I've never felt a loss in power from being aero. But I ride my TT bike a lot, so I get used to it.
Andy, have you been able to pinpoint the position where you are losing enough power so that the more aeroness is not making up for it. This I suppose is now the point where you might be giving away hard earned edge data but can you share any info on your ideal sadle position/effective seat tube angle vs power vs aerodynamics. Cancellara had that special Cervelo for Paris-Roubaix last year and I remember them saying that he was sitting back in the saddle in that solo effort while in many cases you see Dave Z in TT with half the saddle sticking out behind him.
What about lycra shoe covers vs oversocks?
Wool vs. cotton?
Sublimated Vs. solid color?
Toenails clipped vs. hangnails?
right foot vs. left foot?
Godzilla vs. Mothra?
Baudrilard vs. Mayonaise?
Chomsky vs. Lil' Scrappy?
So Andy, when are you going to be building the NYC LSWT full rig to test your TT position?
All I can say is thank God we'll be racing this weekend and Andy can get back to some sort of normal routine so we can resume talking about who sat in, who made the break,etc. And I'd like to take this opportunity to nominate Mrs. Andy for sainthood, poor woman.
The snazzy wheels all take tubies, and I'm vain...
Never got the concept of rolling resistance 'til a couple of weeks ago, and even then, only partially. How much correlation is there between RR and the bounciness of a tire?
Mike, you should've seen the chaos that fan created. Stuff was flying everywhere.
Andy has actually said that he is not geeky enough
to worry about rolling resistance. I did not really believe it then and now i definitely dont believe it. I've got 2 rolls of grey duct tape,one roll of blue low tack painters tape, a case of 1000 10 oz coffee cups (with lids if that helps) and 1 sheet of exterior grade plywood.
Andy there must be something you could come up with using these materials to test RR of tires.
sorry, "differently for shoes THAN it does for humans"... i hate grammar mistakes. almost as much as i hate capital letters.
andy, just spring for a bigger, nastier fan. don't you think that the conversion probably works much differently for shoes as it does for humans on bicycles? anyway, at your stage of, uh... scientific intrepidity?... it's not like having a giant fan in your apartment is gonna ring any more cuckoo alarms than the styrofoam head wearing a bicycle helmet and hovering over your pingpong table...
Sorry to go slightly off topic. What about RR? I've heard somewhere that the best clinchers actually have less RR than the best tubies when properly inflated. I imagine you've seen this too. Are you running clinchers on the TT bike currently, if not, why not?
I NEED the name of the picture, please send me by a e-mail (por favor padrino, confio en que lo vas a ver)
man I just bought a Rudy TT Helmet in December. Maybe thats why Im close to 30 seconds off the winner every time.
I'll probably take you up on that, eventually. I only wish I hadn't listend to Schmalz... I got suckered by weather.com and ended up riding all the way up to tweed and back in a gritty downpour... and in the nude! damn nasty. Well, out of town for funeral and another missed weekend of racing. G.G.
Schmalz tries to mind control me into crashing whenever I ride.
What about testing an aluminum foil wrapped helmet, not only an aero advantage, it also saves you from mind control rays.
Pretty sure it works. It'll be in the next test for sure.
How bout testing a saran-wrapped helmet?? Me and fellow cheap asses would like to know.
How bout testing a saran-wrapped helmet?? Me and fellow cheap asses would like to know.
George, I defer to Schmalz for riding tips. But the best Smiley tip I got was to start in a big gear at a lower cadence, and start easy. Send me an email if you want more of his tips. Not being secretive, just don't want to act like I'm an expert.
No shaving whatsoever - the hair creates a turbulant barrier.
no head-shaving. gotta draw the line somewhere.
TT secrets:
Ride nude
No shoes - just covers
Helmet on backwards
forgot to identify myself (in keeping with personal policy): Sucky Master, c'est moi. G.G.
Yeah, Andy I know you've spent your time and energy on this, and are reluctant to give away your secrets, but as a journalist you do probably feel an obligation to your readers. So let us know what the quick and easy things we can do to shave time from our TT times (not to beat you, just so we don't embarrass ourselves).
I posted that hoping y'all would find the rediculous nature of the post. Apparently I didn't go far enough in the rediculousness, except maybe for Eugene who has latched onto a new set of factors in fluid dynamics. Can't wait to hear Eugene's Unified Theory of Time Trial Fluid Dynamics
Andy, you've thought about this stuff a lot: what in your opinion are, say, the four or five key (technical, not fitness) things a guy with little TT experience can do to maximize his TT performance, assuming he has clip-on aerobars but no other specialized equipment and just wants to try for decent personal best?
weed growing in the background of the shoe pictures?
At 78 degrees, the saddle becomes a rectal thermometer.
What effect does the seatpost angle have? At 78 degrees you are positioned more over the bottom bracket and when compared with being out of the saddle it sort of makes sence in my mind that you would be able to transfer more power. Is this correct? It is however very difficult to test due to wind on 9W and getting tired etc.
If, while TTing, there is a temperature drop due to the wind chill, then we may have discovered a 4th component of fluid energy (elevation, pressure, velocity, wind-chill). Since the total energy in a fluid system is always constant, and since the air pressure and elevation don't change, the drop in temperature must be offset by an increase in velocity. Wind chill = more speed!
Ahh...., the return of the dreaded wind chill; may it never die. And, responding to anonymous, doesn't Adler always ride a smart race? (Is that the proper response? I'm a relative "new poster" to NYV).
thought you were going to say you take your rectal temperature while you were riding...whew...glad i was wrong
I use a thermometer to determine the power loss from my time trial position. When I am in my time trial position, I am going faster so I can tell the windchill using the themometer. The 10 degree drop in temperature more than offsets the 2% powerloss from the further forward and flatter TT position.
I have not ever really noticed a drop in power between the TT bike and the road bike. My intervals are usually within a few watts between bikes. I dont do a whole lot of training on the TT bike......around 20 hours last season. I do, though, make a sorta revving sound when I am on the TT bike so this may be aiding me in ways I'll never understand. N=1
Adler
No!
Do you think Adler will ride a smart race?
Get on a trainer and ride at a fixed cadence. Sit in various positions, wearing a heart rate monitor. See what happens to HR.
On my road bike for the same speed on the trainer my HR is 3-5 beats higher riding in the drops than a little more upright, on the hoods.
Quantifying this -- figuring out if the increase in effort from a lower position is worth it -- is a harder question. I think a good way to address this is to find a still day and do laps on a circuit like the Kissena velodrome at consistent HR and see which is quicker. Or do consistent speed and see which results in higher HR. Never tried this myself.
I was half afraid that I'd click through to this article and find out Andy had stolen a prosthetic limb in the name of science.
I was half afraid that I'd click through to this article and find out Andy had stolen a prosthetic limb in the name of science.
Votre sarcasme est juste le simulation de la sarcasme
Thanks Andy for your good efforts.
Now I will wear my shoe covers.
Piques my curiosity about cleaning up the bottom of the shoe though.
Perhaps a quick and dirty test by smoothly taping the pedal clip on the bottom of the shoe and see what improvement you get - shoud be more than the shoe cover.
Again, thanks for the info.
Cheers,
Neal
writing in a french accent is pretty much the most hilarious thing ever ventured. seriously, never, ever stop that. just keep doing it.
What is zis mayonnaise? Zat ees what je vais put on my pommes frites de la McDonald's, ou le BigMac iz not quite as bon sans le ketchup. Et plus...I have zee preference pour le Royale avec Fromage. Besides, eet is not a real mayonnaise but just zee SIMULATION de le mayonnaise. Eet is ze Kraft whip de la miracle! Putain!
I'm more aero than you
I have no real data, but I've never felt a loss in power from being aero. But I ride my TT bike a lot, so I get used to it.
Andy, have you been able to pinpoint the position where you are losing enough power so that the more aeroness is not making up for it. This I suppose is now the point where you might be giving away hard earned edge data but can you share any info on your ideal sadle position/effective seat tube angle vs power vs aerodynamics. Cancellara had that special Cervelo for Paris-Roubaix last year and I remember them saying that he was sitting back in the saddle in that solo effort while in many cases you see Dave Z in TT with half the saddle sticking out behind him.
What about lycra shoe covers vs oversocks?
Wool vs. cotton?
Sublimated Vs. solid color?
Toenails clipped vs. hangnails?
right foot vs. left foot?
Godzilla vs. Mothra?
Baudrilard vs. Mayonaise?
Chomsky vs. Lil' Scrappy?
So Andy, when are you going to be building the NYC LSWT full rig to test your TT position?
All I can say is thank God we'll be racing this weekend and Andy can get back to some sort of normal routine so we can resume talking about who sat in, who made the break,etc. And I'd like to take this opportunity to nominate Mrs. Andy for sainthood, poor woman.
The snazzy wheels all take tubies, and I'm vain...
Never got the concept of rolling resistance 'til a couple of weeks ago, and even then, only partially. How much correlation is there between RR and the bounciness of a tire?
Mike, you should've seen the chaos that fan created. Stuff was flying everywhere.
Andy has actually said that he is not geeky enough
to worry about rolling resistance. I did not really believe it then and now i definitely dont believe it. I've got 2 rolls of grey duct tape,one roll of blue low tack painters tape, a case of 1000 10 oz coffee cups (with lids if that helps) and 1 sheet of exterior grade plywood.
Andy there must be something you could come up with using these materials to test RR of tires.
sorry, "differently for shoes THAN it does for humans"... i hate grammar mistakes. almost as much as i hate capital letters.
andy, just spring for a bigger, nastier fan. don't you think that the conversion probably works much differently for shoes as it does for humans on bicycles? anyway, at your stage of, uh... scientific intrepidity?... it's not like having a giant fan in your apartment is gonna ring any more cuckoo alarms than the styrofoam head wearing a bicycle helmet and hovering over your pingpong table...
Sorry to go slightly off topic. What about RR? I've heard somewhere that the best clinchers actually have less RR than the best tubies when properly inflated. I imagine you've seen this too. Are you running clinchers on the TT bike currently, if not, why not?
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