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Tour Magazine June 2012 Wheel Test?
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damon_rinard
Jun 12, 12 13:17
Post #26 of 57
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Re: Tour Magazine June 2012 Wheel Test? [jackmott]
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In a wind tunnel, clothing is horribly inconsistent for aero testing.
If the question is about clothing, you need clothing. If the question is about anything else, you need NO clothing.
Cheers,
===========
Damon Rinard, Senior Advanced R&D Engineer
Vroomen.White.Design
http://www.cervelo.com
http://www.bbright.net
jackmott
Jun 12, 12 13:18
Post #27 of 57
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Re: Tour Magazine June 2012 Wheel Test? [Paulo Sousa]
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Paulo Sousa wrote:
Your bias towards Zipp and Hed is cringe-worthy.
This test may well be unfairly crowning the 808 as king.
It *certainly* overstates the aerodynamic performance of the HED Jet 5
where is my bias now bro?
Memorial day sale at ATC and Meet Pro Triathlete Matty Reed - Sat May 25 - Captex!
The newest tri shop in Austin - ATC 360
Freelance sports & outdoors writer Kathryn Hunter
(This post was
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Carl
Jun 12, 12 13:26
Post #28 of 57
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Re: Tour Magazine June 2012 Wheel Test? [jackmott]
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depends on how well they designed it in the first place. if you don't anticipate (or understand) the issues related to position variability and how it might affect your results then you could certainly end up with something undesirable.
Carl Matson
Trek Bicycles
Design Engineer - Speed
Redog
Jun 12, 12 13:32
Post #29 of 57
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Re: Tour Magazine June 2012 Wheel Test? [jackmott]
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They actually used two bikes: Canyon F8 and Treks SC
and did get very different results for the same wheels depending on the frame.
jackmott
Jun 12, 12 13:35
Post #30 of 57
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Re: Tour Magazine June 2012 Wheel Test? [Redog]
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Redog wrote:
They actually used two bikes: Canyon F8 and Treks SC
and did get very different results for the same wheels depending on the frame.
Yes, I know, and I suspect that is an artifact of poorly controlled conditions, rather than frame/wheel interactions.
Memorial day sale at ATC and Meet Pro Triathlete Matty Reed - Sat May 25 - Captex!
The newest tri shop in Austin - ATC 360
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Herbert
Jun 12, 12 13:50
Post #31 of 57
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Re: Tour Magazine June 2012 Wheel Test? [Redog]
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Tour Mag means well, but ......
Redog
Jun 12, 12 13:58
Post #32 of 57
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Re: Tour Magazine June 2012 Wheel Test? [Herbert]
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Herbert wrote:
Tour Mag means well, but ......
....but they are the only ones who are even trying to provide objective data.
Personally I put more weight on what the Tour says then data provided from the Mfgs about their own products.
jackmott
Jun 12, 12 14:13
Post #33 of 57
(2427 views)
Re: Tour Magazine June 2012 Wheel Test? [Redog]
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They are not the only ones who are even trying.
biketechreview tries
velonews tries
field testers try
This particular tour mag testing with the clothed dummy, you really can't put any weight on it at all. Zero. You can't tell which of those wheels in the test is best, or even which are pretty good and which are bad.
you look at this test and go buy an 808 or a Campy Eurus because of it, and you might be spending way too much money, or buying a useless aero wheel =)
Redog wrote:
Herbert wrote:
Tour Mag means well, but ......
....but they are the only ones who are even trying to provide objective data.
Personally I put more weight on what the Tour says then data provided from the Mfgs about their own products.
Memorial day sale at ATC and Meet Pro Triathlete Matty Reed - Sat May 25 - Captex!
The newest tri shop in Austin - ATC 360
Freelance sports & outdoors writer Kathryn Hunter
Herbert
Jun 12, 12 14:29
Post #34 of 57
(2391 views)
Re: Tour Magazine June 2012 Wheel Test? [Redog]
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Objective and smart / correct are not necessarily the same. No doubt they attempt to be objective, but even their frame tests are flawed. Though meaning well.
bnation
Jun 12, 12 14:50
Post #35 of 57
(2349 views)
Re: Tour Magazine June 2012 Wheel Test? [jackmott]
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Could this be a good project for Kickstarter? I wonder how many triathletes would pony up cash to facilitate an independent test of wheel aerodynamics if it was being managed by some reasonably trustworthy subject experts(cobb?, slowman?). Test protocol could be vetted by the slowtwitch masses beforehand. Stretch goals to add more wheels\tires. After creation some percentage of each new purchase of the data could go toward testing further wheels to keep the data up to date. Could work kind of like AFM's Crr spreadsheet, but not free.
Epic-o
Jun 12, 12 16:04
Post #36 of 57
(2287 views)
Re: Tour Magazine June 2012 Wheel Test? [Redog]
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I suppose that the dummy isn't pedaling. Is there any comment about dummy's legs position? Crankarms are turned 180º from Cervelo's DZ dummy legs position
BICYCLE DESIGN AND +
http://cds-0.blogspot.com/
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Redog
Jun 12, 12 16:11
Post #37 of 57
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Re: Tour Magazine June 2012 Wheel Test? [Epic-o]
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no
Tom A.
Jun 12, 12 16:33
Post #38 of 57
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Re: Tour Magazine June 2012 Wheel Test? [jackmott]
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jackmott wrote:
There is every indication that in this particular test, the noise from their protocol is bigger than the differences between wheels. If Tour is lurking on slowtwitch, I would echo the recommendations of others that they remove the clothing from the dummy as a start.
Well...their aero frame test had error bars that were as wide as 7-8W on the measurements IIRC, which would mean that pretty much all of their measurements on THIS test are within the margin of error.
Yeah, at least they're trying...but, they sure could try a little
better
IMHO, without much more effort either...
http://bikeblather.blogspot.com/
rockdude
Jun 12, 12 18:33
Post #39 of 57
(2190 views)
Re: Tour Magazine June 2012 Wheel Test? [Aralo]
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I always felt my eurus were fast. My Eurus and Rolf vectors feel faster than my Zipps.
JoeO
Jun 12, 12 20:30
Post #40 of 57
(2131 views)
Re: Tour Magazine June 2012 Wheel Test? [Herbert]
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Herbert wrote:
Objective and smart / correct are not necessarily the same. No doubt they attempt to be objective, but even their frame tests are flawed. Though meaning well.
How are they flawed?
Tom A.
Jun 12, 12 20:36
Post #41 of 57
(2125 views)
Re: Tour Magazine June 2012 Wheel Test? [JoeO]
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JoeO wrote:
Herbert wrote:
Objective and smart / correct are not necessarily the same. No doubt they attempt to be objective, but even their frame tests are flawed. Though meaning well.
How are they flawed?
Load case not matching real world?
http://bikeblather.blogspot.com/
JoeO
Jun 12, 12 20:40
Post #42 of 57
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Re: Tour Magazine June 2012 Wheel Test? [Tom A.]
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Sorry, could you expand that a little?
(Do you mean load as in weight? I thought we were talking about aero tests)
Tom A.
Jun 12, 12 20:49
Post #43 of 57
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Re: Tour Magazine June 2012 Wheel Test? [JoeO]
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JoeO wrote:
Sorry, could you expand that a little?
(Do you mean load as in weight? I thought we were talking about aero tests)
I was assuming Herbert was referring to their frame "stiffness" tests.
Their frame aero tests suffer from the same large error bars as the wheel test they just published...too much noise to get anything meaningful.
http://bikeblather.blogspot.com/
JoeO
Jun 12, 12 20:58
Post #44 of 57
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Re: Tour Magazine June 2012 Wheel Test? [Tom A.]
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Ah. Understood. Thanks
Herbert
Jun 12, 12 21:07
Post #45 of 57
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Re: Tour Magazine June 2012 Wheel Test? [JoeO]
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JoeO wrote:
Sorry, could you expand that a little?
(Do you mean load as in weight? I thought we were talking about aero tests)
No, the always hyped stiffness tests. They are actually flawed, and the Magazine is too hyped up about stiffness numbers. Plus letting manufacturers send you frames for those tests is another issue.
But as I said, I commend them for trying to do the right thing, and I know they mean well.
bradl016
Jun 12, 12 22:00
Post #46 of 57
(2043 views)
Re: Tour Magazine June 2012 Wheel Test? [rockdude]
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you're probably feeling the 'high quality bearings'
---------------------------------
Oklahoma State Cycling Club
Bicycles of Tulsa Racing Team
District Bicycles - Stillwater, USA
damon_rinard
Jun 13, 12 3:51
Post #47 of 57
(1966 views)
Re: Tour Magazine June 2012 Wheel Test? [JoeO]
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Hi Joe,
Tour's wind tunnel photos show many sources of error. Most are "consistent" to the casual eye so are easy to dismiss as nit picking, but all of them can change the flow in unnatural (and often non-obvious) ways. The general effect is that the bike or wheel is being "tested" in some (invisible!) swirling air that, yes, produces a drag force, however precisely measured, but that has potentially weak (or no) relation to the drag you pedal against when riding out doors.
Here are a few examples off the top of my head:
Swinging safety chain in the wake has upstream effects that are not present when riding. Might not seem obvious that this is important but users of CFD will recognize how a good wake is critical to getting stable test results.
Struts are unnecessarily large, creating unnatural changes in flow.
Large open holes in the floor can affect flow in an unnatural way as well. In both cases the turbulent flow shouldn't be there, but it is , and it can be picked up by the tires and thrown into the (supposedly) clean flow around the wheels and frame.
Component groups were not the same on different frames (Red, Di2, etc.)
Clothing.
If the question is about clothing, you need clothing. If the question is not about clothing, you want NO clothing.
Even "the same" clothing is never the same aerodynamically. Drag forces are very sensitive to even the smallest shift in fabric in even a very tight fitting skin suit. Cervelo wanted to clothe foam Dave (for lots of reasons, hides the joints and gives advertising value to the pro team's sponsors, etc.) but found that even with the awareness we'd gained through years in the tunnel we could not get the consistently precise results we wanted with clothes on.
Below are a few more thoughts I wrote earlier.
http://forum.slowtwitch.com/...post=3746899#3746899
A few comments, again with a grain of salt without having seen the article. In no particular order:
· Clothing. justkeeppedaling nailed it. We learned years ago that clothing, although it's realistic (no one rides naked, well almost no one!), it does add noise to the measured drag data, potentially swamping small differences in frames. Wrinkles matter, to an athlete for sure, but especially when the question isn't about the effects of clothing but about the effects of different frame designs.
· Right or left foot forward: Although our DZ mannequin doesn't pedal, we've played around in the wind tunnel with pedaling mannequins. There are still challenges to doing complete testing with moving legs, but one of the things we've experimented with is fixing the mannequin's legs at different points around the pedal circle. It's perhaps surprising that the main bike interaction is with "legs", and drag isn't so sensitive to "legs here or legs there," other than asymmetries some of you have already noticed. DZ's fixed legs are in the position that matches the same average drag as pedaling legs.
· Bottles. I didn't communicate personally with TOUR about bottles, but we did design the S5 with bottles in mind, since road riding is rarely done without at least one. Tom A. has already quoted the typical aero drag penalty for a round bottle, and also the improvement with the S5. The S5 was built with bottles in mind, and TOUR's test did capture that it seems.
· Mannequin position: Posture makes a difference, but if it's the same it's fair. John Cobb has even named "A" backs and "B" backs, for example. Cervelos work with both, so I don't think this is a big flaw with TOUR's mannequin. Could be closer to the average back shape perhaps but I'd put it farther down the list.
· Arms: Yes, our mannequin has triathlon arms. We chose that because triathlon is important to Cervelo, and our tri bikes need DZ's arms on the aero bars. That said, we've also done some other experiments and found that arms on tri bars have a very small effect on the frame’s aero drag, since the arms are a little above most of the frame elements that affect drag. There's less vertical component to air flow than some might imagine.
· Lasers: TOUR is smart to use precision positioning. I assume they've also positioned the bike in a smart way: For example, when the rear axle is fixed in the same position on the tunnel balance, then changes in chain stay length move the BB (thus the rider) forward or back, so the rider's position is different with respect to the wind tunnel. Same with BB height. We learned this years ago and account for it now.
· Open or closed wind tunnel: Both can work well.
· Cable housings: To accurately compare frames, cable housings should be included when the cable routing is different, since cable routing is a design choice that can really affect aero drag. In addition to different personal judgments on lengths and loops, with the "same" bike and cables we've seen that cables add turbulence and drag as expected, but they also add variability due to vortex shedding. It's typical in a wind tunnel test that the inner cables might not be fully connected to the derailleurs (or even present), and without the normal spring tension on the inner wires the outer housings create large drag variability because they'd be more flexible than in real life. We insert rigid inner wires (weld wire, for example) to address this. Otherwise you get unintentional drag variation that can be wrongly attributed to some other design aspect. Di2 is another variable – if some bikes are mechanically equipped then are you really comparing frames?
These are just a few of the thoughts off the top of my head and I'm sure the TOUR guys will only get better at wind tunnel testing. They've shown when they updated their stiffness test protocol that they're willing to improve as new knowledge comes, and after a few more trips to the tunnel I'm sure we'll have really good data from them.
You probably know Cervelo has spent a lot of time in various wind tunnels. We've learned there are a lot of details that can make surprising differences. This doesn't mean wind tunnels aren't any good, it just means that to find the differences you’re looking for you have to control all the other variables. There are many variables that at first glance don't seem to be, in fact, variable. It takes a lot of experience to accumulate the "mistakes" that lead to this knowledge. If done well, the difference in performance due to decisions in frame design is also there for the rider in real life, even when the other variables are there as well.
(End quote)
Wind tunnel testing can be a good, valid way to measure the biggest performance aspect of bicycles. At Cervelo we were in the wind tunnel before the company was even started. We know the mistakes we've made and learned from in the past and it drives me nuts to see the latecomers (and not only TOUR Magazine) making many of the same mistakes. We've even offered to help but it takes money and that's understandably hard to come by when "bad" wind tunnel testing sells just as many bikes and magazines.
Okay, sorry for the rant. Suggestions welcome on how to move toward a better wind tunnel test protocol for the industry including companies and magazines.
:-)
Cheers,
===========
Damon Rinard, Senior Advanced R&D Engineer
Vroomen.White.Design
http://www.cervelo.com
http://www.bbright.net
JoeO
Jun 13, 12 5:48
Post #48 of 57
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Re: Tour Magazine June 2012 Wheel Test? [damon_rinard]
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That was an excellent answer. Thank you for the detail
rockdude
Jun 13, 12 6:00
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Re: Tour Magazine June 2012 Wheel Test? [damon_rinard]
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I guess the question is, if all this nit picking in what seems to be a fairly controlled study caused enough noise to skew the results of which wheel is better, then what happens in the real world with thousands of uncontrolled variables. WIth this thought, in the real world, one day my Eurus might be fastest, then next day my zipps 303 might be faster and following day my Easton EA70X.
My guess is these wheels are very close to each other in Drag and which one is faster really depend on the conditions you ride in.
jackmott
Jun 13, 12 6:07
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Re: Tour Magazine June 2012 Wheel Test? [rockdude]
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No, that is not quite right, for two reasons:
1. The amount of error in these tests is on the orders of 7-8 watts. That means an 8 watt advantage could be hidden in this test by the error. An 8 watt advantage is still a lot in the real world.
2. This is *error*. It is not a situation where the Campy Eurus was *actually* faster than a bunch of aero wheels because the dummy and its clothes happened to be oriented a certain way. It is a situation where the uncontrolled variables happened to align advantageously for some wheels and not for others.
In other words, there are no situations in the real world (or very few anyway) where the Campy Eurus would save you time over a HED Stinger 4 or Zipp 303 (assuming of course that a controlled wind tunnel test would confirm that it really isn't that slippery in the wind, of course).
Does that make sense?
rockdude wrote:
I guess the question is, if all this nit picking in what seems to be a fairly controlled study caused enough noise to skew the results of which wheel is better, then what happens in the real world with thousands of uncontrolled variables. WIth this thought, in the real world, one day my Eurus might be fastest, then next day my zipps 303 might be faster and following day my Easton EA70X.
My guess is these wheels are very close to each other in Drag and which one is faster really depend on the conditions you ride in.
Memorial day sale at ATC and Meet Pro Triathlete Matty Reed - Sat May 25 - Captex!
The newest tri shop in Austin - ATC 360
Freelance sports & outdoors writer Kathryn Hunter
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The New Specialized Wind Tunnel
Will this be a game changer for Specialized, in both sales and product design, or will it not move the sales and design needle versus those in Specialized's competitive set?
Yes, Game Changer
Minor move forward
Won't budge the needle
