Excellent work Tom!

Here's a related quiz to test out everyone's "eyeball wind tunnel" capabilities in regards to "Chunging it" with two different framesets:

Off the top of your head: if the "Chung method" estimate for the CdA of this rider/bike combo is around 0.270-0.275 (based on multiple TTs)...
http://www.hcphoto.smugmug.com/...2858355_aZDzn/Medium

...what would you estimate as the CdA for this rider/bike combo? http://www.hcphoto.smugmug.com/...4318610_i69ri/Medium

In the interest of full disclosure, here are the only equipment/kit differences between the two:

1) Bento box behind the stem in photo #1 (according to the MIT interview, should provide some significant aero savings)
2) Shoe covers in photo #1 (according to most sources: small, but measurable aero savings)
3) Rider weight around 2-3 lbs. less in photo #2 (yeah, I know the riders calf looks weirdly large in photo #1, but I think that is an optical illusion - it hasn't changed in size)
4) Different aerobar extensions (same S-bend shape though)
6) Different saddle
6) Different sunglasses
7) Different frameset (2005/6 Motobecane Nemesis (same frameset as the Fuji Aloha 1.0) vs. 2005 Cervelo P3SL

Everything else equipment-wise is the same (including components) down to the tubes/tires and tape on the valve holes. Total bike weights are within 0.5 lbs of each other.

As you can see, the rider's body position is VERY similar in the two photos. I could give you the measurements, but there are only very minor differences. Based on testing, I don't believe any of these to be aerodynamically significant.

I'll wait until I get some guesses about the CdA difference, and then reveal the answer...

Thanks for playing!

Rik

I have never denied that it provide such an advantage. I just don't think that it is is a very significant one, at least in the big scheme of things. Wind, after all, is the true enemy, not lack of routes for which the elevation is known (note that I did not say "flat", since that is not a requirement when using either the signal averaging or regression approaches).

 
.250 - .255 m^2

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http://bikeblather.blogspot.com/

Your English isn't bad for a non-native speaker.

.249.

Candy@sses ... ;^>

I think I'm barred from entering this contest Gee that second frame looks familiar...

last month at the Piru

Damn... now that I know that... I shoulda gone. :)

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36 kona qualifiers 2006-'23 - 3 Kona Podiums - 4 OA IM AG wins - 5 IM AG wins - 18 70.3 AG wins
I ka nana no a 'ike -- by observing, one learns | Kulia i ka nu'u -- strive for excellence
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1. Sweet lard: you can pedal in that position? Ouch!
2. How much wind was present for both datasets and from what angle? ;-)

I confess to not reading every single post in this thread, but Tom..your time savings look to be at least double what Andy has posted in the past, and also roughly double what the Trek whitepaper would suggest. Am I missing something, are you or your methods somehow doubling the savings?

Thanks for posting, BTW, very nice work overall!

Well then, you should've read every post ;-)

Here's what Andy had to say in post #23: http://forum.slowtwitch.com/...rch_string=;#1802599



Maybe I'm missing something, because I don't recall there being a P2K test in the Trek white paper.



Thanks. Considering that the TTX is recognized to be "neck and neck" with a P3C, I bet you're glad you upgraded from the P2K, huh? ;-)

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http://bikeblather.blogspot.com/

I must say I am finding this thread mildly amusing. Here we have the same people who kick anyone who tries to do a similar test to gauge power improvements seen with PowerCranks around the block, describing the method as being essentially worthless, stating the PM is the only acceptable method of measuring power, yet we are using the same technique (just putting in different knowns and unknowns) to assess aerodynamic drag and everyone thinks it is wonderful and amazingly accurate.

Hey, you work with what you have, and if you don't have $thousands to get into a wind tunnel to assess drag or don't own a PM to assess power, you do the next best thing. While this is an interesting result and probably indicates an improvement I would be extremely surprised if the real improvement is as great as is calculated here. It seems way too large (as someone stated, 25% of the total bike drag) when there are so many uncontrollable variables involved in the technique.

Anyhow, it will be interesting to see how much you actually improve your TT performance based upon your expected improvement based upon these numbers.

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Frank,
An original Ironman and the Inventor of PowerCranks

I've been watching this thread all day wondering what would happen first...

1) Frank jumping on trying to bring PC's into the discussion.

or

2) Someone telling you that while you're wasting your time arguing endlessly about bullshit seconds, they're just gonna go train and get faster.


I guess now that I have an answer I can on about my business.

Oh, and thanks for posting your results - very interesting reading!

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Erik
Strava

I assumed the P2K was no worse than a Madone...which I didn't think was unreasonable.

I upgraded based on the data from the whitepaper and Andy...when I lose TTs now, I have only my own execution, preparation (and parents) to blame...just how I like it!

He probably made the same mistake I made. Using the degrees of separation (P2C and P3 are similar in drag, and the P3 and P2K look similar), I certainly wasn't expecting this much of a difference--though with Andy's results I shouldn't be surprised. I figured that once you put a disc on the bikes, the covered seat tube and shaped seat stays weren't a big deal. Obviously, I was way wrong on that one.

I've either underestimated the P3 or overestimated the P2K, but either way, it looks like my 'over-under' guess is way off. To echo what the others have said, nice work!

Very simple. You're attempting to test the effect of training with powercranks, and attributing the result (or at least part of it) to powercranks.

Difficulty in testing: to show that powercranks is effective, you have to measure:
Before: prior to any training
After: 1. Training with powercranks
2. Training an equivalent amount, without powercranks
Technically, to determine the effect of powercranks, you'd have to use the same test subject, which is impossible. You can't have someone train with powercranks, then "detrain" him back to his original state, then train back up without powercranks and measure the difference.

Hence, the statistical approximation: take a *large* sample of people
Before: measure everyone's fitness prior to training
*Randomly* assign people to train either with powercranks, or without powercranks.
After: 1. Measure "fitness" (power?) of people who trained with powercranks
2. Measure "fitness" of people who trained without powercranks
Both groups should have trained and equal amount, and powercranks should not have caused either group to train more or less, if you really want to measure the effect of powercranks. Of course you can consider this variable as endogenous and ignore it (consider it as part of the overall effect of powercranks).

Only then do you have a scientific study with powercranks.


It's much easier to do with a wind tunnel / aerodynamics test. Individual variables are easily isolateable. Tests are repeatable, using identical equipment, same wind tunnel, same testing conditions (or at least well defined corrections can be made based on the testing conditions). Which results in a more rigorous scientific study overall.

Anecdotal evidence is a first approximation. Powercranks *possibly* help, but until you (or someone else) does a full scale independent scientific test, people will always have reason to doubt you. Nobody doubts that aero helmets, aero frames, aero wheels do work: the evidence is out there.

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Chewie
Slowtwitch Aeroweenie since '06

Ugh, all we say is that our typical user is gaining 40% in 6-9 months after starting exclusive training with PC's. That claim does not say that every watt of increase is due to PC's. Some of it, of course, may be due to training effect and, in fact, some probably is. That is why one does independent studies to try to isolate the variables. However, 40% is much more than most people expect to see in that period of time so some must be due to the PC's and the independent studies that have been done seem to suggest a substantial benefit in both efficiency and VO2 max can be attributed to use of PC's.

So, if someone comes here and says I have increased my speed x amount in 6 months of training with PC's and that calculates to X watts increase. You may disagree as to how much of the increase is due to PC's themselves and how much they might have seen if they had trained traditionally but the result remains yet people come here and call them liars and shills and whatever. Yet, when similar "unbelievable" improvements are seen in aerodynamic drag by using one of current "favorite" bikes of this site everyone thinks it is just wonderful and justifies their last or future purchase despite the fact that no good control of all the variables existed in the test. If someone really wanted to know what the difference was they would go to a wind tunnel and put a mannequin on the bike(s) so everything would be known to be exactly the same between the tests, except the bike. Then we would know.

This result is an estimate yet it seems people are taking it as gold. And the number is so large it is hard to believe it to be true but people want it to be true which probably accounts for why everyone is taking it as gold. We will see how the racing goes. (of course, we will need a lot of numbers to assess whether race conditions affected the results one way or another.)

I simply pointed out the seeming hypocrisy.

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Frank,
An original Ironman and the Inventor of PowerCranks

thanks for trying... please, PLEASE, let's just ignore him and maybe he'll go away.

I was really enjoying this thread up 'til now.

Oh...thanks for that! For a second, I just thought you were just being an ass...

I'll be curious to see how many others view the 'hypocrisy'.



Phooey...

You're pointing out a double standard which I don't believe exists.

Mannequin? LOL... Cervelo did just that. They're using it in their wind tunnel tests.

I don't understand what you mean by "no good control of all the variables existed in the test". Could you elaborate? Or have you never been to or conducted a wind tunnel tests? We (people who do these tests) usually make an effort to ensure that proper controls are taken, and it shows: many of these independent tests arrive at the same conclusion, with very similar numbers. These numbers that we come up with are hardly "estimates": they're calculated, based on well established models. You're using the word "estimate" in the same way that creationists call evolution just a "theory".

Sometimes the numbers we come up with are large. And they are, cos that much of an improvement was made. You're insulting the people who test in the wind tunnel, as well as the people who conduct the test, by saying that people want to believe the results are true.

Oh, and if you don't mind, could you email / PM me the "independent studies that suggest a substantial benefit in both efficiency and VO2 max can be attributed to use of PC's"? Finals are gonna be over, and I think I'll have time to pour over them. I'm honestly curious.

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___________________________
Chewie
Slowtwitch Aeroweenie since '06

Weren't the tests involved that started this thread done on the road? As I understood it these were calculated improvements, not measured improvements. That is what I meant by "no good controls". It is not possible. 1-2 mph winds could substantially affect the results yet it would seem to be virtually calm to the rider. Is the rider riding the same straight line each trial, hitting the potholes the same, etc.?

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Frank,
An original Ironman and the Inventor of PowerCranks

Andy, quick question for you regarding your Rule of Thumb above (based on 28-29MPH?)

I will be testing using the iBike iAero, which gives me a static CdA readout. What formula should I use to calculate out the relative differences in CdA as applied over 40KM ... will your formula CdA improvement of 0.005 m^2 = 0.5 s/km faster work for me at 29MPH/76kg?

Thanks,

- Gary

"Weren't the tests involved that... blahblahblah..."

Frank, read the protocol.


We, as an "online community" should really begin to institute a consensual standard that requires a poster to demonstrate at least a rudimentary understanding of the topic under discussion before taking seriously their attempts at stone-throwing.


...of course, such a standard would effectively eliminate 90% of your "contributions" to this board...



Could everyone please just ignore the FDBS, and continue on with the excellent thread?


(back to lurking...)
.

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Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
Coaching and bike fit - http://source-e.net/ Cyclocross blog - https://crosssports.net/ BJJ instruction - https://ballardbjj.com/

No no, this thread is just getting interesting. No point in putting forward these claims and data without some critical reviews!

Full credit to the OP for doing this.
Full credit to Frank for laying down a critical eye, I just hope this thread stays clean so we see some real ideas surface.

Can I ask how many of the players in this thread are honestly neutral in their views? and not in the 'pro P3' or 'anti P3' clubs?
Its eaiser to find data to support what you want rather than what you dont want...

(This post was made with genuine interest, none of which was intended to bait)

The only problem is that Frank really didn't make a 'critical review' or even ask a question about the protocol (well he did--but the question was so silly that is shows he's never bothered to read the information on the Chung protocol).

Remember, this is the same guy who spent 8 pages arguing that Joaquin's file wasn't manipulated, only to then admit that he didn't even have a rudimentary understanding of power files?? I'm all for a critical eye....but this is just silliness...

You can always go to analyticcycling.com to double-check, but the short answer is: yup. That ROT pretty much applies.