RChung

Yeah, a little.

asgelle

I wonder given the advances in CFD, if bike designers have moved to using CFD as the primary design tool with testing either in the wind tunnel or field used primarily to validate the CFD results rather than the designs themselves. I know that's where we're moving in my field.

TimothyH

Then I don't suppose you would be interested in Bicycling Science by by David Gordon Wilson and Jum Papadopoulos.

It has a decent section on aerodynamics, especially as it pertains to individual components; round vs bladed spokes for example.

I think the lack of published data acquired outside of a lab environment simply reflects the relative difficulty of measuring things in the field. Let us know what you find.


-Tim-

RChung

Pretty much, though they had to validate the CFD models first (usually by tunnel testing). Now that the CFD models are more mature, they mostly use them for primary design cuz it's quicker than building a physical model (or physical scale model) for testing. Eventually, however, they take completed models into the tunnel and on the road. One example of real-world testing I'm peripherally familiar with is the left-side drive on the US Olympic track bikes for the 2016 Olympics, and the testing we did for the 2012 and 2016 Olympics on the team pursuit -- there weren't tunnels large enough for the entire pursuit teams so the bikes/riders were instrumented and tested on the velodrome. That was a tricky optimization problem, but pretty cool.

Abe_Froman

You have no idea the amount of stuff I'm not familiar with. I'm pretty certain we don't have nearly enough time to cover all of it

Now THIS would seem to be a really interesting application of field testing that would yield useful results.

RChung

Except 1) you admitted you hadn't read my presentation, and 2) you brought up the +/- 2% error in instantaneous power measurement as if it were dispositive (hint: I cover why it's less important than you think in that presentation). So while I may not know the amount of stuff you're not familiar with, I certainly know enough about the stuff you're not familiar with to know that you have opinions that are not backed by knowledge.

bruce19

TiHabanero

"but don't you think lab testing would be more helpful than real world? How could you possibly isolate just aerodynamics in a meaningful way for testing on a moving bike outside a wind tunnel? I have a feeling the margin for error introduced by any number of factors would be greater even than the aero differences you're trying to test. You would never know how 'real' any result is. "
I think what I am after is how meaningful are aero dynamics of a frame when put to the test and all the elements of riding the road are incorporated. It is assumed it makes a difference, however it has not been proven outside of a laboratory environment. I know aero wheels make a difference as we comparison tested them over several time trials on the same course with similar weather conditions. Results were consistently huge. If it can be done with wheels, it can be done with a frame. Timed results will be small so It might be difficult to find consistency.

RChung

Oh, that. Years ago Tom Anhalt field-tested a 2001 or 2002 (?) Cervelo P2K (already a pretty aero TT bike for the day) against a 2007 or 2008 Cervelo P3C. It turns out that when holding the wheels and his position and clothes constant, the CdA of the P3C at zero yaw was about .023 m^2 less than the P2K. This turns out to be almost exactly what was measured in a wind tunnel. The predicted time difference based on this estimate for him would have been just a tad more than 2 sec/km in a TT, and was confirmed later that year at the SCNCA TT championship course, where under slightly worse wind and air density conditions but almost exactly his same average power, he improved his time with the P3C by something like 1.8 sec/km on the P3C vs. the P2K. So there is your real-world racing difference. There was an insanely long thread on Slowtwitch where a million questions and criticisms were asked (I think the criticisms were roughly equivalent to the one above, and I answered them in 2008 so there you go). That was for two TT bikes. The difference between a road bike and a TT bike would, of course, be larger.

The bottom line is that you don't often hear about "real-world tests" not because they're not done, but because the results you get from the field and wind tunnel tests tend to validate each other.

That said, if you're interested in total drag (as you should be) as opposed just to aero drag, you have to take into account rolling resistance, which you can't do in a wind tunnel. In a wind tunnel you only measure aero drag (obviously) so, for example, narrow tires always do better than wider tires. However, in field tests we can look at total drag on varying surfaces, and that's when you can determine that there are instances where you can trade off some aero drag for better rolling drag and end up lowering total drag. I've done that for a couple of the recent world hour record attempts, and for some road race championships. As mentioned above, I've done a little bit of work with Olympic pursuit teams. That worked well, and In another Olympic test, in the run-up to the 2016 Olympics, the Swiss MTB team tested various tires at various pressures using my method, and it worked out for Nino Schurter.

TiHabanero

The whole is made from the sum of all the parts. Total drag is the measurement of course. I find the Cervelo info interesting and wish there were more comparisons like this.

brianmcg123

redlude97

VN Tech podcast ep. 1: Chris Yu explains how CFD makes bikes more aero | VeloNews.com

Carbonfiberboy 

It tells us nothing about the frame. Different wheels, different components, different tires. Silliness except that it might sell Cervelos, which has gotta be the point.

531Aussie

Tour Magazine did a long test which I gather was outdoors, but I dunno if that's what you're looking for.
There's a long thread about it on here:
Tour Magazine 2016 Aero Road Bike Test

There's another thread on Weight Weenies about it. I'll have a look later

canklecat

The mysterious Mr. Hematocrit, for Peloton Magazine video reviews. Probably the best you'll find for real world aero bike testing. He compares two or more bikes per test. He's built like a beast, too muscular for long climbs, but perfect for downhill runs. Useful insights into handing characteristics too.

531Aussie

Exactly. I'm not shooting the messenger, but that's a farkin joke putting the most parachute-like wheels on the non-aero frame. I annoys me.
I guess they wanted to test the whole package of an aero vs non-aero bike, but it's not a wheel test.

RChung

OTOH, sometimes there are things you probably shouldn't do with CFD and wind tunnels, that might be better with field tests.
https://www.tue.nl/en/university/new...ously-assumed/

531Aussie

Here ya go: 37 pages of arguments about aero frames. I thought the test was outdoors, but now I'm not sure. I'll read Tour Mag article on the first page later
https://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=136752

The test was done in 2016
The times in the black bars for the bikes using 404s

531Aussie

Ooops! This was the test I was thinking of. Jee, 4 years has gone fast. It's an "aero vs light" frames test from 2014. Interestingly, some of the supposedly non-aero frames were faster than the aero frames. Once again, I'm not sure if it was outdoors. No Treks, Pinarellos, or some other big brands.
Only 19 pages of bickering on this one https://weightweenies.starbike.com/forum/viewtopic.php?f=3&t=123175
Most links to the related article have been removed from the Weight Weenies thread, so I dunno what the parameters were. I think it was 100km covered with a constant wattage which wasn't that high; I think well under 300W.

The differences are obviously relatively small, considering the duration of over 4.25 hours.



I stuck them all on the one list. In bold are the "non-aero" frames

4:17:11 Cervelo S5
4:17:34 Merida Reacto EVO
4:17:51 BMC Time Machine TMRO1
4:18:01 Giant Propel Advanced SLO
4:18:02 Specialized S-Works Venge
4:18:06 Simplon Nexico
4:18:18 Scott Foil Team
4:18:25 Cervelo R5
4:18:29 Canyon Aeroad CF
4:18:33 Neil Pryde Bura S1
4:18:37 Scott Addict SL
4:18:45 Neil Pryde Alize
4:18:46 Canyon Ultimate CF SLX
4:18:48 Giant TCR Advanced SL
4:18:52 Ridley Noah Fast
4:18:54 BMC Time Machine SLR 01
4:18:56 Rose Xeon CW-8800
4:18:57 Simplon Pavo 3
4:19:04 Storck Fascenario 0.6
4:19:05 Storck Aerario
4:19:07 Specialized S-Works Tarmac
4:19:12 Ridley Helium SL
4:19:27 Rose Xeon CR5
4:19:42 Merida Scultura CF Team

Racing Dan

The fastest earo bike you can get is a clip on bar and some tight fitting clothes. An aero drop bar bike is close to an oxymoron.

Racing Dan

That is less then one percent gain from the slowest light weight to the fastest aero bike. If you are not racing for money, then who cares?

531Aussie

How about bolt-on aero bars on an S5 vs bolt-on aero bars on a CAAD9? I'd say that's the point of those tests, even though, yes, as you suggest, the drag on the body is so massive it makes the drag on other parts look tiny.
I've got no idea about, it, even though I've read those threads on Weight Weenies. People on both sides of the argument -- "aero road frames are worth" vs "it's just marketing bollocks" -- make good points, it seems to me, at least

531Aussie

Yes, good point. However, as someone claimed in that thread, the target output for the 4+ hours was "only" 200 Watts, and the "pro aero frame" guys reckon that higher speeds/output would've produced more drag, and, therefore, bigger differences.

RChung

Different people have different goals and different incentives. By minimizing aero and rolling drag, I've helped a couple of people set world records, a couple of teams win Olympic medals, and one guy to finally beat his brother-in-law in their annual family race. That was sweet.

OBoile

IIRC they did do some similar aero bike vs aero bike tests where they used the same wheels.