Login required to started new threads

Login required to post replies

Prev Next
Re: the hierarchy of aero [monty] [ In reply to ]
Quote | Reply
monty wrote:
Hey listen everyone, i think wind tunnel testing is the tits. And just like pool testing for wetsuits and skins it is the best possible place to eliminate as much noise as you can to get any meaningful results. I think tunnel tests should be done on all this new stuff. My point is that i'm very leery when someone says this or that will take 4 minutes or 10 minutes off your bike times.

monty, expressing something in minutes is akin to expressing it in grams of drag. It's simply a unit of measure, not a value judgement. The stipulation is "all things being equal".

Quote:
This has been going on since the first bike went into the tunnel. If you add up all the savings that aero shit is supposed to give you, then guys should be well under 4 hours in hawaii.

Well, that's where the "all things being equal" comes in. Some changes are incompatible with others. You can't stack them all up. It's not a purely additive sum.

But in general, wind tunnel testing has pretty much fulfilled its promise. I'll leave you with the quote that my friend, Jim Martin, often uses:

Laurent Fignon wrote:
Greg [Lemond] believes he can win, but it is impossible. I am too strong in the mind and the legs. Fifty seconds is too much to make up in such a short distance.

AndyF
bike geek
Quote Reply
Re: the hierarchy of aero [AndyF] [ In reply to ]
Quote | Reply
I have been in the wind tunnel and wound the results quit similar to reality. I tested my Specialized Shiv with TT-helmet against a Baum road bike with a road helmet. The theoretical difference in the tunnel would imply a massive 6,5 minutes difference over 50 k, and when I tested it outside (with a Powertap powermeter with 300 watts in average on both) I ended up up with an average difference of 30 sek on a 5 k course which would have been 5 min over 50 k. The reason I think there is a 1,5 min error is that the best TT-position (which was the base of my calulations) was with my head really low, and not a position I could hold 100 % of the time. Every once in a while I had to look up and watch out for holes in the road, cars etc. Therefor my aerodynamic drag in the tunnel (CdA of 0,208) was a bit lower than I could do on a rolling course with some turns.

At least my little experience with the tunnel is that is is a very good and precise way to find out what actually is aero for you, and what is not.

But I agree that is seems odd with all the aerodynamic improvements that the time have not been reduced more, but I think that often the companies are exaggerating their claimed benefits. Also we must not forget that it needs massive reduction in aerodynamic drag to save a lot of time. I reduced my drag with about 10 %, which is a lot, but that only gives me about a 7 minutes theoretical saving over 180 k, and I do not think the best triathletes get a 10 % overall drag reduction that often.

http://www.triallan.com
Ambassador of:
Quintana Roo - https://quintanarootri.com
Bioracer
Precision Fuel & Hydration
Quote Reply
Re: the hierarchy of aero [AndyF] [ In reply to ]
Quote | Reply
btw, if skin is that much slower than aero fabric/textile, why does not Bradley Wiggens wear a long sleeve og gloves? I would guess that Bradley Wiggens olympic setup is one of the most tested setups in the world of cycling. Then again, he is riding with around bottle.



http://www.triallan.com
Ambassador of:
Quintana Roo - https://quintanarootri.com
Bioracer
Precision Fuel & Hydration
Quote Reply
Re: the hierarchy of aero [Allanhov] [ In reply to ]
Quote | Reply
$$ trump Aero.

How much do you think teams get paid to ride with the Gatorade bottle?
Quote Reply
Re: the hierarchy of aero [scofflaw] [ In reply to ]
Quote | Reply
I understand that a well located mirror will save lots of drag in a race situation.
Quote Reply
Re: the hierarchy of aero [Allanhov] [ In reply to ]
Quote | Reply
At least my little experience with the tunnel is that is is a very good and precise way to find out what actually is aero for you, and what is not.

And it sounds like you confirmed that field testing is also a good way to find out what is aero...



Quote Reply
Re: the hierarchy of aero [Orbilius] [ In reply to ]
Quote | Reply
Orbilius wrote:
$$ trump Aero.

How much do you think teams get paid to ride with the Gatorade bottle?

Gatorade uses a lot of money of on marketing so I understand that they will use a product that is not the best regarding pure performance, you would think that they would make a aerodynamic bottle with Gatorade on.

But Wiggens rides with a HED 3-spoke wheel and Osymetric chainrings (changed to round ones now) even if that is not on Team Sky's sponsorlist, so obviously they have drawn the "$$ trump Aero"-line somewhere.

http://www.triallan.com
Ambassador of:
Quintana Roo - https://quintanarootri.com
Bioracer
Precision Fuel & Hydration
Quote Reply
Re: the hierarchy of aero [rruff] [ In reply to ]
Quote | Reply
rruff wrote:
At least my little experience with the tunnel is that is is a very good and precise way to find out what actually is aero for you, and what is not.

And it sounds like you confirmed that field testing is also a good way to find out what is aero...

Field testing have unfortunately a too much margin of error to be a good way to find out what is error. With my Shiv I had 30 % less drag than on the roadbike, which is massive. That translated in to 30 sec difference on 5 k course, but I had 3 sec differance on each run with identical set up. It I would make changes which is smaller, like changing from a TT-helmet to a road helmet, it would be much more difficult to see. And if you do smaller changes it might be impossible to conclude anything on field testing (if not in a velodrom like the ERO does).

In the wind tunnel I could instantly see the impact on the smallest changes since I had my drag projected in front of me in real-time while I was pedaling.

http://www.triallan.com
Ambassador of:
Quintana Roo - https://quintanarootri.com
Bioracer
Precision Fuel & Hydration
Quote Reply
Re: the hierarchy of aero [jackmott] [ In reply to ]
Quote | Reply
jackmott wrote:
3. the totality of not having a bunch of shit hanging off your frame

this
Quote Reply
Re: the hierarchy of aero [gtingley] [ In reply to ]
Quote | Reply
gtingley wrote:
http://www.socalttseries.com/...al-aerodynamics.html

Aerodynamics for Time Trial Racing - Where to invest upgrade dollars when considering new equipment and gear.

Nice link.

Obviously fit will be dependent on your given individual body, but what are some skin suits that would be worth looking at?

Likewise, what shoe cover do you personally use?
Quote Reply
Re: the hierarchy of aero [Allanhov] [ In reply to ]
Quote | Reply
Allanhov wrote:
Field testing have unfortunately a too much margin of error to be a good way to find out what is error.
Not always.
Quote Reply
Re: the hierarchy of aero [Allanhov] [ In reply to ]
Quote | Reply
Allanhov wrote:
Orbilius wrote:
$$ trump Aero.

How much do you think teams get paid to ride with the Gatorade bottle?


Gatorade uses a lot of money of on marketing so I understand that they will use a product that is not the best regarding pure performance, you would think that they would make a aerodynamic bottle with Gatorade on.

But Wiggens rides with a HED 3-spoke wheel and Osymetric chainrings (changed to round ones now) even if that is not on Team Sky's sponsorlist, so obviously they have drawn the "$$ trump Aero"-line somewhere.

I believe the UCI restricts the shape and size of aero bottles - quite a few of the popular models are UCI-illegal these days. Also, with the special cages, it might cost Wiggo more time being out of the aerobar and fiddling with the bottle than he'd save with an aero shape.

ZONE3 - We Last Longer
Quote Reply
Re: the hierarchy of aero [Allanhov] [ In reply to ]
Quote | Reply
In the wind tunnel I could instantly see the impact on the smallest changes since I had my drag projected in front of me in real-time while I was pedaling.

It is good for that... which would be subtle changes in positioning.

A few years ago I analyzed the raw data on someone's wind tunnel test (a respected tunnel and operator) and was not impressed. The random variance on drag was ~ 2% when doing a yaw sweep and returning to zero.
And conclusions were made on differences that were much smaller than this... based on a single run.

I don't know why... maybe small changes in position or something else. I know that I have a huge range even with all the contact points fixed depending on how I hold my head and shoulders.

So like field testing, I think you want to spend a lot of time in the tunnel if you are looking at changing small things. Test each configuration multiple times, switch back and forth, etc.


Quote Reply
Re: the hierarchy of aero [rruff] [ In reply to ]
Quote | Reply
rruff wrote:


A few years ago I analyzed the raw data on someone's wind tunnel test (a respected tunnel and operator) and was not impressed. The random variance on drag was ~ 2% when doing a yaw sweep and returning to zero.
And conclusions were made on differences that were much smaller than this... based on a single run.

I don't know why... maybe small changes in position or something else. I know that I have a huge range even with all the contact points fixed depending on how I hold my head and shoulders.

So like field testing, I think you want to spend a lot of time in the tunnel if you are looking at changing small things. Test each configuration multiple times, switch back and forth, etc.


Easily the best post in this thread. Great observations and advice.

Jim Manton / ERO Sports
Quote Reply
Re: the hierarchy of aero [rruff] [ In reply to ]
Quote | Reply
rruff wrote:


A few years ago I analyzed the raw data on someone's wind tunnel test (a respected tunnel and operator) and was not impressed. The random variance on drag was ~ 2% when doing a yaw sweep and returning to zero.
And conclusions were made on differences that were much smaller than this... based on a single run.


Well, was this a constant speed yaw sweep or do you mean "test at some non-zero yaw then move the table back to zero yaw, let the flow stabilize, and then test again at zero yaw" and see a 2% difference in zero-yaw drag?

Last edited by: RChung: Aug 26, 13 7:39
Quote Reply
Re: the hierarchy of aero [RChung] [ In reply to ]
Quote | Reply
The later.

I was told by someone who had a lot of experience at San Diego (it wasn't that tunnel), that 1% was what they would typically see. And I'm sure it varies a lot with the person... if it is indeed mostly a small positional change that was causing it.
Last edited by: rruff: Aug 26, 13 13:33
Quote Reply
Re: the hierarchy of aero [Jim@EROsports] [ In reply to ]
Quote | Reply
I wasn't even thinking of your velodrome testing. I can definitely believe that you get results that are as consistent as a good tunnel, with the only limitation that can't look at yaw effects. On the other hand you do get the "power to spin the wheels" term included which is missing from tunnel tests.
Quote Reply
Re: the hierarchy of aero [rruff] [ In reply to ]
Quote | Reply
rruff wrote:
The later.

I was told by someone who had a lot of experience at San Diego (it wasn't that tunnel), that 1% was what they would typically see. And I'm sure it varies a lot with the person... if it is indeed mostly a small positional change that was causing it.

That's interesting. I knew that same tunnel same rider same setup across sessions could typically be 1% different but I hadn't realized that you could see 2% within a session. That sounds large.

One of the things I've played with in field testing is a better way to get the standard error for the estimate of the CdA.
Quote Reply
Re: the hierarchy of aero [rruff] [ In reply to ]
Quote | Reply
Hello rruff and All,

There is still quite a lot of room for aero improvement in conventional triangular frame bicycles/riders/equipment in triathlon though less in the more strict UCI depending on how rules continue to evolve.

I do agree with Monty that data gleaned in a pristine wind tunnel or testing protocol when used for a sales presentation (yes my data too) very likely shows better results than the data that would be gathered when in a race, outdoors, gusty wind, hot humid day, with dust and sweat in your eyes, in traffic, with your jersey riding up, your left leg hurts, there is a bee in your helmet, you missed the last feed station, and your competition is somewhere up ahead of you. However it is standardized data and can be compared to other standardized data ........... but as Monty says ......... should be taken with a grain of salt when applied in a race environment.



While not a triangular frame .......... even in HPV aerodynamics make a difference ...... 82+ mph ............... :)

I expect market forces in cycling will continue to cause the various rules to be modified creating obsolete equipment and procedures requiring periodic replacements.

If we were looking for the true ideal .......... 'it is the cyclist - not the cycle' meme ........... we would all ride the same device with the same position, clothing, etc.

I think I like the current evolving equipment environment better than a static one even though is involves more thought and time that could be better spent on training.

Cheers,

Neal

+1 mph Faster
Quote Reply
Re: the hierarchy of aero [Allanhov] [ In reply to ]
Quote | Reply
Allanhov wrote:

Field testing have unfortunately a too much margin of error to be a good way to find out what is error...

I think I would have to disagree with this statement...it might depend on the protocol/experimenter ;-)

http://bikeblather.blogspot.com/...ng-chung-method.html (limit of detection apparently less than ~1.5W at race speeds)


http://www.trainingandracingwithapowermeter.com/...aerodynamicists.html (also limit of detection apparently less than ~1.5W at race speeds)

http://bikeblather.blogspot.com/
Quote Reply
Re: the hierarchy of aero [RChung] [ In reply to ]
Quote | Reply
Ya... even 1% is pretty big. When you think about the drag on a set of wheels being 10% of the total, that represents a 10% variance on wheels alone... if you are comparing one set to another with no other changes. The same goes for a lot of other aspects.

The people doing the testing are in a tough position, because it is much easier to sell the service if you tell someone they can come in and test 20 setups in 2 hrs. If you have a client who is not able to hold consistent positions, you don't really want to say "sorry, none of your data are good... that will be $2k please". Easier to just give them the numbers... everyone is happier. But in reality you need to test that baseline over and over again, and the variation establishes the accuracy of your results. It will give you an idea of how many times you need to test each configuration to factor small differences, too. It's tedious, time consuming... and expensive unless you are doing field testing on your own... and even then you have to figure what your extra time is worth.
Quote Reply
Re: the hierarchy of aero [rruff] [ In reply to ]
Quote | Reply
The reason I liked your post was that you touched on two key points.

First, you're correct, when you see small changes in drag, it's important to know if they're within your margin of error. Yes, we see very consistent results, but we also understand that a small, unintentional, position change by a rider can effect CdA on any particular test. We're able to detect small changes in hand position, so we certainly have to understand results must be questioned and verified.

This, of course, leads to your second point, which was equally correct. Test and test again. If the results are close, it's very important to test back and forth. Get a bigger picture and see if the results are consistent. I actually find myself re-testing for validity even when the results are dramatic, or really, because the results are so dramatic. Sometimes it just seems to good to be true, and I'm compelled to verify. It's just good science; at least that's my intention. :-)

Jim Manton / ERO Sports
Quote Reply
Re: the hierarchy of aero [nealhe] [ In reply to ]
Quote | Reply
nealhe wrote:
While not a triangular frame .......... especially in HPV aerodynamics make a difference ...... 82+ mph ............... :)

FTFY.
Quote Reply
Re: the hierarchy of aero [JoeO] [ In reply to ]
Quote | Reply
JoeO wrote:
One thing you might do -- particularly for those on a budget -- is separate front and rear wheel. As I understand it, a front aero wheel gives you a much bigger improvement than a rear.

Can you elaborate? & then why are front wheels generally lower profile than rear/disc wheels? And then why not a deeper front wheel? Not trying to argue, just to understand. Thx.

_____________________________________
What are you people, on dope?

—Mr. Hand
Quote Reply
Re: the hierarchy of aero [scofflaw] [ In reply to ]
Quote | Reply
I'm not the expert. I've just been made to understand -- mostly from reading here -- that the front wheel plays a much larger role in aerodynamics than the rear. Perhaps Tom A. or someone else who lives in this world can elaborate (or correct me). The way I understand it, the front wheel is so important because it's the first thing the air hits. The air is pristine at that point. However air is quite a bit "dirtier" by the time that it reaches the rear wheel so the savings are reduced.

Again, purely my rudimentary understanding.
Quote Reply

Prev Next