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Re: Ask us anything about Aero Camp [Runless] [ In reply to ]
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Runless wrote:
Heath is pictured in 16 and 20 and the captions talk about some of his changes. Sounds like clothes and helmet were a big part of things http://www.slowtwitch.com/..._Aero_Camp_4145.html

thanks for the heads up on the images. his position and equipment in 16 suggests to me that a 14% improvement is indeed extraordinary.

fwiw, a std road helmet to a full-on aero helmet is about a 3% delta at beta=0.

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Kraig Willett
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Re: Ask us anything about Aero Camp [Jim@EROsports] [ In reply to ]
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Jim@EROsports wrote:
Great question. Rich Sawiris at Wheelbuilder.com insures our Powertaps are calibrated properly; not sure there's anyone in the business who understands them better. We like using PT's for a few reasons, one of them being they don't drift. We've seen many a pm come through testing that we're clearly not calibrated properly, and it does have obvious effects. We had it happen at this camp, in fact. I absolutely agree with DCRainmaker's assertion that a majority of athletes are riding around with improperly calibrated pm's.

This has been enough of an issue that we're ready to insist everyone use only our Powertaps to insure consistent results. We've also considered offering a calibration service, but time is an issue for us.

Beyond that, the pm being used is zero'd before every run. We definitely can see when a pm drifts and, trust me, some very obviously drift during a test.

Do you have 650c wheels with powertaps?
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Re: Ask us anything about Aero Camp [Duckie] [ In reply to ]
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Duckie wrote:
I am guessing that since I am a straight cyclist testing a TT position, some things may test differently for me than for others so keep that in mind.

Can you expand upon this educated guess please? Does it refer only to how the Aeon tested, or more about position et al?

_____________________________________
What are you people, on dope?

—Mr. Hand
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Re: Ask us anything about Aero Camp [BikeTechReview] [ In reply to ]
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BikeTechReview wrote:
Runless wrote:
Heath is pictured in 16 and 20 and the captions talk about some of his changes. Sounds like clothes and helmet were a big part of things
http://www.slowtwitch.com/..._Aero_Camp_4145.html


thanks for the heads up on the images. his position and equipment in 16 suggests to me that a 14% improvement is indeed extraordinary.

fwiw, a std road helmet to a full-on aero helmet is about a 3% delta at beta=0.


You of all people should know better than to trust the "eye-ball" wind tunnel. And I'm sure you're not suggesting that your eye is better than what they are doing up the road from you at the Velosports Center.

At any rate, my baseline run was .2643. That is what is pictured in number 16. My next change was dropping the armrests down 1cm. that got me to .2507. I then took off the rear bottle which barely moved the needle but did slightly down to .2494. The helmet, as your extensive experience showed you was not a huge CdA dropper, but it did drop it to .2447. The last change was to test in the PI skin suit, that dropped me down to .2267

This seems to jive pretty well with what others have found:

http://forum.slowtwitch.com/cgi-bin/gforum.cgi?post=4165683#4165683


And based on manufacturers claims from companies like Castelli and Pearl, while eye opening, the savings from the suit doesn't seem too far out of line. FWIW, the Kiwami suit is a probably not as tight as it should be (I ordered up a size due to body length which was a mistake) and it exposes a lot more skin than a normal top.



Heath Dotson
HD Coaching:Website |Twitter: 140 Characters or Less|Facebook:Follow us on Facebook
AeroCamp February 25-26, 2020 A2 Wind Tunnel
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Re: Ask us anything about Aero Camp [Ex-cyclist] [ In reply to ]
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Ex-cyclist wrote:
You of all people should know better than to trust the "eye-ball" wind tunnel. And I'm sure you're not suggesting that your eye is better than what they are doing up the road from you at the Velosports Center.


I don't have a dog in this fight...I rarely do wind tunnel work with athletes these days. Field testing can be done well, but it is tricky. And, yeah, my eyeball is a good independent line of inquiry, and when things don't jive with it, it piques my curiosity...and then I test again, and again, and again, and...y'know, to make sure what I'm measuring is indeed there and not just noise.

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At any rate, my baseline run was .2643. That is what is pictured in number 16.

how many repeats of this configuration did you do?

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My next change was dropping the armrests down 1cm. that got me to .2507.

that is an extraordinary improvement for a 1cm change in drop. Are there any other things that might explain this large delta?

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I then took off the rear bottle which barely moved the needle but did slightly down to .2494. The helmet, as your extensive experience showed you was not a huge CdA dropper, but it did drop it to .2447.

a good head position is pretty robust to aero helmet choice. a 2% delta seems high for an aero helmet to aero helmet swap even with a non optimal head position.

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The last change was to test in the PI skin suit, that dropped me down to .2267

that is an extraordinary difference. A CxA reduction of ~0.02 is roughly equivalent to going from a road jersey that is a couple sizes too big to a skin-tight one in my experience.

Again, I don't have a dog in this fight, but this thread reminds me of the quote: "No one believes the results of a theoretical analysis except the analyst. Everyone believes the result of an experiment except the experimentalist."

=================
Kraig Willett
http://www.biketechreview.com - check out our reduced report pricing
=================
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Re: Ask us anything about Aero Camp [BikeTechReview] [ In reply to ]
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I think a drop of more than 10% is possible, especially with amateur triathletes that did not have much prior testing done and you optimize both position and equipment.
I liked the graph you posted, but as long as air density is accounted for in the calculation I do not see a problem. Also I have seen spikes in temperature and increased humidity like that when somebody picks up the device to take a reading. That would be aVERY lokalized effect and would not effect the measurement.
I think I send you tunnel data before trying to attach a probe to a bike to measure dynamic pressure and found way to much rider interaction in every acceptable position. so I disagree that measuring q would be the better idea. I think field testing works and has been showen to give usable results. The biggest source of error is the rider.
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Re: Ask us anything about Aero Camp [ In reply to ]
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I asked about this but wasn't responded to...

How does an aero bottle on the down or seat tube perform on a Speed Concept in general? How about just having a single behind-the-saddle bottle setup vs a frame-mounted bottle?

Any generalized insights?

Thanks.
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Re: Ask us anything about Aero Camp [Outlawdon] [ In reply to ]
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I alluded to this earlier. It depends upon the size of the frame. What size frame do you have?

Brian Stover
Accelerate3 Coaching
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Re: Ask us anything about Aero Camp [IJ] [ In reply to ]
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IJ wrote:
I think a drop of more than 10% is possible, especially with amateur triathletes that did not have much prior testing done and you optimize both position and equipment.

I agree. Are you suggesting Heath is an amateur triathlete that hasn't done his homework? To me, his position/equipment during his first run looks pretty good - certainly not like the folks I've seen get 10%+ improvements in CxA.

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I liked the graph you posted, but as long as air density is accounted for in the calculation I do not see a problem. Also I have seen spikes in temperature and increased humidity like that when somebody picks up the device to take a reading. That would be aVERY lokalized effect and would not effect the measurement.

I think the real reason I posted the graph I did (data taken during an ADT test session quite some time ago when no volleyball games were being played) was primarily to illustrate non-monotonicity of DA. One of the individuals who tested on the day(s) of the aero camp that is the subject of this thread mentioned that they thought there was a linear drift between runs...maybe there was, and maybe there wasn't - without measurement of the things that matter, it's difficult to say. The test director on the day is the guy who will be able to shed some light on how these things are measured and dealt with systematically/automatically.

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I think I send you tunnel data before trying to attach a probe to a bike to measure dynamic pressure and found way to much rider interaction in every acceptable position. so I disagree that measuring q would be the better idea. I think field testing works and has been showen to give usable results.

I haven't seen your data. Please share it in this thread. I'm sure there are folks smarter than I reading who might be able to provide some insight. If you are basing your perspective on data acquired in a wind tunnel where blockage might be a factor, that is something to consider. I agree that field testing can work, as long as one understands the limitations of their tool/methodology. That could be a serious piece of work to undertake for a given individual who shows up on field-test day.

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The biggest source of error is the rider.

I'd agree as long as everything else that matters is measured and accounted for. In a wind tunnel, where the force and q measurements are calibrated and known day to day or rider to rider, yeah, for sure, the rider and the clothing they choose to wear on the day are a big source of error. In a venue where the force (i.e, power meter of unknown calibration and ability to deal with reverse torque) and ambient conditions (e.g. air density, wind pattern changes due to associated behaviors during volleyball games in the infield etc...) are not known, well, then, maybe I'm not as sure as you seem to be....and as Bjorn alluded to earlier, without the means to verify or record how rider's behave _during_ a run, well, things could very well be a bit of a dog's breakfast.

=================
Kraig Willett
http://www.biketechreview.com - check out our reduced report pricing
=================
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Re: Ask us anything about Aero Camp [desert dude] [ In reply to ]
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desert dude wrote:
I alluded to this earlier. It depends upon the size of the frame. What size frame do you have?

It's a small frame with Hed Jet 4 in front and Hed Jet disc in the rear.
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Re: Ask us anything about Aero Camp [Outlawdon] [ In reply to ]
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iirc and I think I do, the Bontrager bottle on the small frame actually worked better than no bottle or a round bottle.

I suspect bc it fills in the junction between the seat/down tube and BB a good deal.

Brian Stover
Accelerate3 Coaching
Insta Twitter

Last edited by: desert dude: Jan 26, 14 16:52
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Re: Ask us anything about Aero Camp [desert dude] [ In reply to ]
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Bontrager Speed Bottle reportedly tested nicely on Small/Extra Small Gen. 1 SC. I didn't see the test, but got that from the rider afterwards.
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Re: Ask us anything about Aero Camp [JTolandTRI] [ In reply to ]
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Thanks for the feedback and info on the aero bottle guys! I appreciate it and will continue to use an aero bottle on the frame then.

I have a random hypothetical and experimental question...how would the drag look if someone completely taped up the inner triangle of a TT frame from the down tube to the seat tube. Obviously not UCI legal, but would it be safe and also fast?
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Re: Ask us anything about Aero Camp [JTolandTRI] [ In reply to ]
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Thanks for posting the blog link. It was interesting to me because I'm also a long-legged 6'3" and have always suspected that I'm not terribly aero despite making most of the Slowtwitch-accepted position/equipment choices. Suspected because my power output to speed ratio isn't great compared to what some here post. Was the long-leg thing something they told you there, or is it somehow common knowledge?

In any case it's enough to make me decide to reserve some track time since it's only a couple of hours drive for me anyway.
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Re: Ask us anything about Aero Camp [trail] [ In reply to ]
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Little bit of both. Common sense in general, but then people will also just state it as an observation. The fact that raising your seat 1cm can make a big impact sort of leads to the conclusion that raising it 10cm would make a giant impact. Body proportions are also likely a big part. I'm 6'3" with a 37" inseam and +3 ape index, which sort of means I have lots of long round "cylinders" all over the place. In contrast, someone with a super long torso who can get horizontal the ground and have minimal limbs all over the place will likely be more aero.

No expert confirmation on that, just common sense.
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Re: Ask us anything about Aero Camp [JTolandTRI] [ In reply to ]
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>No expert confirmation on that, just common sense.

Sure, makes sense in the eyeball wind tunnel. I guess we'll just take solace in the fact that some of the best TTers or triathlon uberbikers (Wiggins/Rapp) are also cylinder-all-over-the-place types. Though I'd be curious to know if that's because the body type can have natural advantages in aerobic capacity or pedaling leverage that outweighs the aero cost, or some other reason....
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Re: Ask us anything about Aero Camp [Outlawdon] [ In reply to ]
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It's been done, Trimble made a bike like that. Carbon fiber main triangle. I suspect fast at 0 yaw. not sure what would happen at higher yaw angles.

Brian Stover
Accelerate3 Coaching
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Re: Ask us anything about Aero Camp [BikeTechReview] [ In reply to ]
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BikeTechReview wrote:
Runless wrote:
Heath is pictured in 16 and 20 and the captions talk about some of his changes. Sounds like clothes and helmet were a big part of things http://www.slowtwitch.com/..._Aero_Camp_4145.html


thanks for the heads up on the images. his position and equipment in 16 suggests to me that a 14% improvement is indeed extraordinary.

fwiw, a std road helmet to a full-on aero helmet is about a 3% delta at beta=0.

14% is a lot, but it can and does happen, although it's usually not solely through positional change alone (although I have seen some awful starting positions and crappy clothing), e.g. we might see double digits if we also consider impact of wheels etc (you might be surprised at what people think is aero, or that wheels don't matter - seriously!). And the unecessary paraphernalia they have on their bike!

For those whom have managed to self set up a reasonably decent TT position I'm working pretty hard to find a 5% CdA improvement through positional changes in one 2 hour testing session, but it can be found and that's not an uncommon outcome, obviously it's an individual thing.

Did that recently with a recent world elite track champion and another former pro turned masters racer (just loves his racing) and managed a CdA reduction due to position adjustment of ~4%. Obviously we also look for other improvements, with helmets being the obvious one.

I've seen examples where lowering the rider's front end down from a similar position to your posted photo has made their CdA higher, I've seen it result in very little change, and I have also seen it result in substantial improvements. What you notice happen for one individual just does not universally translate. Indeed we found this testing the elite world champion rider the other week - we had to bring his front end up in order to lower his CdA. It seemed counterintuitive, but we had 4 hours of solo test time to re-run multiple times and be absolutely sure.

Some people are just aerodynamically gifted and some respond (in a CdA sense) to positional changes far more than others. Aero is weird like that.

And the best helmet choice for that same WC rider was one of the most unusual as well. I almost said to not bother with that helmet as it never wins when performing aero helmet comparison testings. Well it did for this guy. Aero is weird like that.

On some people I have tested road to aero-helmet difference that is negligible (including myself), and yet I've seen substantial differences with same helmets on others. It is so individual. Aero is weird like that.

As for controlling for conditions, yeah definitely something to stay on top of and venues need good inspection and repeated use to gain insight into what can/does happen (but a new tunnel presumably has same issues). Which is why it's great to see professionals like these guys working hard to nail such things. Personally I monitor and adjust for air density changes continually (every run is checked before/after), and venues I use don't have other stuff like volleyball going on as I book the venue for exclusive use, so things like loading dock doors are a non-event or readily spotted. Also I try to have baseline runs repeated during and at the end of a session to see how consistent they are.

Heck, on the right days I've got some pretty good testing data at outdoor tracks. Precision suffers a little, so it then becomes a matter of working out what level of change can be reliably detected. My team mate runs our local LS wind tunnel, just a shame it doesn't (yet) have a bike testing rig as we could on the same day compare results.
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Re: Ask us anything about Aero Camp [JTolandTRI] [ In reply to ]
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37" inseam for 6'3" is just fractionally over average for the height. It is a higher ratio than the population average but most people don't realise that inseam ratio scales with height. So your 48.x% is higher than male average 47.7% but not unexpected. As it happens you have the same dimensions as me, but over 20kg lighter. Luckily I have a lot more power to make up for the CdA hit (my best is ~0.26, with 0.245 in power sacrificing positions).

Speedtheory | ST Interview
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Re: Ask us anything about Aero Camp [cyclenutnz] [ In reply to ]
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Interesting. I've always assumed 37" inseam for 6'3" was pretty big given peoples response, including many people in the height range. I would be surprised if that was close to national average. I wonder if as you start to reach towards the extremes the ratio's get thrown off possibly? No background knowledge just thinking out loud.

I definitely count on watts/kg when racing, because my watts/CdA certainly isn't cutting it right now.
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Re: Ask us anything about Aero Camp [RChung] [ In reply to ]
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RChung wrote:
cerebis wrote:
I think this is a great idea and something I would considering doing for sure but I have a question about experimental methodology.

The environment being used is highly controlled (I appreciate why) and -- I'm assuming -- the athletic efforts during measurement are short and free of many real-world factors. Riders will be highly conscious of being the subject of study and therefore will more than likely be on their best behaviour. How do you control for that difference so that when these equipment and position choices are taken outside, they're still optimal?

What I am thinking about mostly is changes in posture over long efforts; form frequency of head-dipping to fatigue related postural changes.


Well, first, that's something that can happen with wind tunnel measurement, too. Second, one of the virtues of field testing is that you can often tell whether your position is sustainable for the targeted length of your event; third, even if you can't hold that position for the whole time, the times when you can hold it will either be faster for the same power or require less power for the same speed, which can help your run; and fourth, sometimes you have to just HTFU.

When I do testing, I get to see after 2 hours of runs how the athlete deals with that level of fatigue. It's a factor and is something you can only really see by watching a rider.

If a rider happens to race at a suitable venue and under consistent conditions, it is also possible to see fatigue induced increase in CdA through post-hoc data analysis. I've done that a few times, which resulted in adjustments to both set up and mental approach (awareness of the issue helps them to pay attention to their position on the bike as they fatigue). It also works when analysing something as short as kilo track TTs, track pursuits as well as longer road TTs.

That's the nice thing when you see a rider actually riding, with the bike moving freely underneath them, such things if they occur become apparent and so appropriate action can be taken.
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Re: Ask us anything about Aero Camp [Jim@EROsports] [ In reply to ]
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Jim@EROsports wrote:
I constantly bother Andy too. Poor guy. It can be done with the system now, but it's not ideal.

To answer another question...yes, power meter accuracy is very important. On at least two riders the numbers didn't add up to what I was seeing, and both times there were issues. One was a pm reading to high, and another was a wheel rubbing slightly on a brake pad. We're very close to having clients only using our pm's to keep the numbers consistent across the board. It does drive home how important proper pm calibration is for everyone.

Anomalous mechanical drag aside, a stable torque zero I find is a good sign and gives confidence, at least such that you can determine the CdA deltas with good precision.
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Re: Ask us anything about Aero Camp [RChung] [ In reply to ]
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RChung wrote:
It really hammers into your head that things that work on one person don't necessarily work on someone else, and that the eyeball is a poor wind tunnel. It's humbling when you realize that everything you know is wrong.

Aero is weird like that.
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Re: Ask us anything about Aero Camp [JTolandTRI] [ In reply to ]
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From USA Miltary data for 4000 individuals

Data is getting patchier at our height but the trend is very clear. People are just amazed by 37" inseam as they don't have context on what normal is for tall people

Speedtheory | ST Interview
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Re: Ask us anything about Aero Camp [Watt Matters] [ In reply to ]
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Watt Matters wrote:
<snip>

Best of luck in your business ventures.

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Kraig Willett
http://www.biketechreview.com - check out our reduced report pricing
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