You'd get lots of interest from the UK if you included the planet X frame which is VERY popular over here. It also goes under a lot of other names, but looks like this:

"...
Results will be comprehensive and for sale after this test..."

...shortly after which they will be available for free on every tri and TT related forum etc..."

I don't see you making money on this one!

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My Blog

So why not sell the results beforehand to help pay for it all?

Id be in for a resonable fee....

Sell it to a magazine?

As far as the making money part of it, I am pretty sure I can cover the costs of this with sales of the results. If I make a profit, great....I'll run some more tests with helmets, aero cranks, hydration options etc.

As to how to sell it so that it doesn't appear on every bulletin board, chat room and website within 24 hours...well there are ways to do this. If this project comes to fruition, rest assured I will not be "winging it" in regards to tunnel protocols OR the best way to protect the results. Tunnel experts and legal experts will both be in the mix from Day 1. Which I guess is today.

I forgot to mention, significant ST discounts will apply.

Thanks for taking the initiative for getting this going!

I don't have any bikes in those sizes that I can lend, but if you're doing pre-orders for the results to help funding, I'd definitely be interested.

Hope this works out..

Dave,

I like Andrew69's suggestion. I'd become a "subscriber" or "sponsor" up front in exchange for the results. Of course, it puts a bit more pressure on you to see it through, but it would get you some operating capital.

.

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Bob C.

The "science" on any matter can never be settled until every possible variable is taken into account.

I think someone proposed something like this before recently. They mentioned people chipping in. I'm in for $29.52 up front once you know it's going to happen.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

great idea! How about going one step further--you'll be testing all the flagship, why not test all the entry level bikes from the same manufacturers. It would be interesting to see a comparison. Also, how about adding Kuota?

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______________________________________

"thoughts become things, choose the good ones"

the kuota has already been proven to be a brick. Why test what we know is already a third tier frame?

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

For purely selfish reasons, I ride one of those bricks--and yes, it's the entry level brick.

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______________________________________

"thoughts become things, choose the good ones"

Are you borrowing the bikes, or do you get to keep them? If they are truly "donated to science", then you *might* be able to cover costs by selling the inventory of bikes after testing. I also think the best market is to sell the data to individual bike shops. Make the data proprietary and something which can't be shared, so each shop has to purchase/license/subscribe. Shops which carry the "best" bikes could then further justify a premium for the "best"/"fastest" bikes, and they would have the data to back it up. So that is how I see the $$$ side of it.

I wouldn't consider purchasing data of either the bike alone or of you on the bike. Although, on second though, it might prove useful for me to calculate how many watts I need against you at the VA State TT Champs next year, at least if you are the rider ;-) Sure, I'm good for $20 in order to know your drag information, and I only want the data from one bike!

Do you have any wind tunnel testing experience? Any aerodynamics expertise?

I would think you could get fairly far with this if you had a comprehensive test protocol and data reduction proposal prior to going to test. Personally, I would write a proposal detailing these items - and the intended data set you plan to present "for sale" - to solicit greater participation.

Old school fast frames? Zipp and softride?

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~~~~~~~~~~~~~~~
-Cartels: Serotta, Zipp 2001, Guru, eh?
-"It was kinda long and then i got really tired"

Sure, I'm good for $20 in order to know your drag information, and I only want the data from one bike!

One other thought; how are you going to get all the bikes set up the same if you're borrowing them? Presumabley it will mean steerers sticking out as you can't cut them to length.

no mag (no american mag aside from consumer reports) would purchase the results. us tri mags are a monopoly and are biased towards those that purchase advertising space in them

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Adrenaline TriSport | Boulder, Colorado
Close Out Sales
Your Front Range source for Felt, Argon18 and Blue Bikes
| TYR | DeSoto | Skirt | Rocket Science Sports | Speedo | Spiuk | Zipp | Mizuno | Brooks | Zeal | Aquasphere |

I'd like to see you add a Look 596 to your test. Yes?

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.
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Paul

add a Look 596 to your test.

Ambitious project. You should also test with the head turned to the side.

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Frank,
An original Ironman and the Inventor of PowerCranks

That's a good point, easily overlooked. I wonder if it would be 'best' to have a spacer stack and some clay, and normalize it to ~3 CM of spacers above the stem. Not optimal, but better than having inconsistencies. Those aero spacers aren't particularly expensive, and would lower the effect a bit.

Personally, I'd only be happy seeing that sort of set-up on a bike that was originally designed to have spacers. The Shiv has deliberately put the top of the stem level with the top of the top tube.

Good point. Perhaps it would be wise to test 1 bike (that uses spacers) with and without them on top, and get a rough conversion factor, which can then be applied. Either way, aero spacers should be used.

It'd difficult to properly test that area - it's very dirty air if you use a front bottle and with arms, but very clean on a solo bike. I know that, in general, bike alone is a good stand-in for bike+person, but in that area, I'm not so sure.

You can calculate what the effect of a given height of cylinders would be when placed in the free stream. As you say though; that'll change if you put stuff in to disrupt it.

I'm assuming that the tunnel testing will be done without a rider as I doubt there are many riders who could hold a single position on different bikes over the time it would take.

The DZ dummy could :-)

You can have my zipp 2001. It's a 700c bike and I ride a 54cm road bike so the frame size is representative of an 'average' size tri bike.

PM me and let me know how you want it built up/built down and where to ship it to.

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My training

I'd want to see a P3 aluminum in there also.

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Want: 58cm Cervelo Soloist. PM me if you have one to sell

Vintage Cervelo: A Resource

Guys, I appreciate all the input on this.

In no particular order...

I will be borrowing bikes. I will be setting them up as as identically as possible. Bikes of similar size normalized to stack and reach is how I am going about this. Same wheels and tires of course. Zipp disc and deep front and possibly Hed disc and Hed front if there is time and money for that many runs/bike. All will use something like Vision basebar and clip on (the same set and angle and brake levers and shifters and stem length) for all bikes EXCEPT the ones that come with a proprietary and unswapple set from the manufacturer ala the Shiv etc. Cables will be in place and trimmed or made to look as trim as possible to the tunnel on all bikes. Pedals will not be on the bikes but I will be using a standard crank aligned the same for each bike. Spacer stack will be accounted for. Obviously bikes with hidden cables won't be showing any cables they would not normally. Protocols will be professional and transparent. I will tell you all what I intend to do before I even do it.

I have no direct experience in the wind tunnel but I will be working both with the tunnel engineer as well as an outside consultant who has run these types of tests before. Got no horse in this race. I have followed every tunnel and aero thread and bit of info on this site and the web in general for numerous years so I would like to think I know what I am getting into.

I will update the list in my OP as to what bikes will be tested and which ones I have already secured. I will add the Look 596 and I already have offers of a Zipp 2001 and a newer beam bike as well.

As to expenses and pre-orders, let me get a little further along with the planning of this and I will let you know. When it looks sure to happen I will re-address this issue. Expenses for this will mostly be shipping and tunnel time and that will be very close to the time of the test itself. I have two excellent mechanics on the project and I am soliciting a few guys to help design and verify the test protocol.

And Flanagan, I am going to spend some time down there on my new Giant tweaking the position. I'll give you that info for free in exchange for me picking your tires at the state TT next year.

Since your intent is to compare the frames, I think you should probably do something similar to what QRoo did in their Cd0.1 testing with some minor "tweaks".

http://forum.slowtwitch.com/...=cd0%201%20;#2225340

In other words, test the bikes without bars. My suggestions for "tweaks" to that protocol would be:

1. Place a capped round tube (PVC?) over the portion of the steerer sticking out of the top of the headtube. Use and appropriate length tube and/or spacers under it, so that the vertical distance from the BB to the top of the tube is the same on each tested configuration. This would mean figuring out which of the "units under test" has the most stack and then working from there. This would eliminate having to play around with stems and such throughout the testing.
   
2. Use a consistent seat and seat position (again, relative to the BB) across all of the bikes. Alternatively an adjustable "blob" could be made to go onto the top of each seatpost to eliminate the fact that portions of the seatpost heads that aren't normally exposed in use ARE exposed during the testing without a rider. Again, the top of the "blob" would be set relative to the BB in a consistent manner.
   

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http://bikeblather.blogspot.com/

Tom: how to you test the Trinity Alliance, shiv, speed concept with that setup? Also, you mess up the 596 testing (or is that stem removable?). Additionally, that means cleaner air hitting the top tube - doesn't that exaggerate the effects of a good top tube (to a small degree).

Well...with the Shiv, just leave the bars off ;-)

Seriously, though...you make a good point. But, that difficulty in comparing across those models with proprietary and not easily removable bar setups is going to be there no matter what. I was just trying to make a suggestion that would lessen the test time and variability.

Never mind...

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http://bikeblather.blogspot.com/

There are a couple ideas I am considering for spacers. One would be to make them all the same as the highest bike but that would give the "no spacer" bikes even more advantage. Another is to see if it is possible to calcualte the drag effect of different stacks of spacers and subtract it out. Option three is to just lie to all my bike donors and cut everything flush. <----big joke there...you're bikes will be returned as you remember them. Actually better, as part of the protocol will be to test clean and waxed bikes.

Dave Luscan

I love the idea of testing clean v. waxed.

I always wax my ride before a race with Speed Shine. Takes <1min to apply so this, or a similiar spray-n-wipe product, may save you some time.

http://www.griotsgarage.com/...aners/speed+shine.do

-tim

X2 on the Planet X and Aluminum P3. A Zipp would be very interesting too, and what about a Lotus and/or Hotta? Those would probably be tough to come by, but it would interesting to see the results! I'd likely be willing to throw in some money to see the results.

Cheers,

Mike

It's a pretty common practice in kayak racing to wax beforehand - same concept, just denser fluid.

Hi Dave,

I'm a big supporter of this concept, but of course have to get the go ahead to share bikes. We don't have many Shiv's right now, so delivery would be based on time of year. I have a couple of questions and notes here:

1. Mike Giraud at the A2 Tunnel knows what he's doing, so I'd trust independent results from him. Who's the other expert consultant you're looking to bring in?

2. Yaw testing at A2 takes a long time right now. To do this test right, you'd need to test at least one bike 3 or more times throughout the test. Current protocol puts yaw sweeps at ~45 minutes with no wheelbase length changes. This would be ~7 hours for 10 bikes tested plus controls. This extensive of a bike test (to garner reliable answers) would take ~12-15 hours. So tunnel time alone, we're talking $6,000. Sounds like you anticipate this cost, but to be clear, I'd only support the test if the protocol is entirely scientific including tare sweeps and the re-running of 1-2 bikes multiple times through the test (whether it be one or more days long).

3. I'd simplify and run with only one wheelset that you test on everything. If you want to check any wheel stuff afterwards, finish your test and pick one or two bikes to go back and study. Any typical aero wheelset would work well -- but don't run with crazy narrow or fat tires. A solid 23c clincher or 21-23c tubular is nice.

4. Spacer stack can not be messed with or calculated out. I sincerly recommend picking a stack and reach you're trying to meet (i.e. a "typical" triathlete position for a guy who's 5'10" etc.) It's hard to be locked into one position, I know, but making changes or getting close does not work. Variations in stem length are less significant than stem angle -- i.e. if you go up higher with stack, even with a round steerer tube, you should lock into 1 angle of adjustment for the stem. Use one stem manufacturer and various lengths. Additionally, stack matters more than reach for aero drag in the cases you're looking to study. If you can only match one perfectly because of a frame's geo, match stack.

5. You need to cut steerers. Long cylinders put into the wind generate a lot of drag and you cannot accurately compare the drag of two bikes with different steerer lengths sticking up above the stem. If Specialized were to support this kind of a test, it wouldn't be a big deal to get you a fork you can cut the steerer on.

6. Cable routing matters -- all bikes should be fully ridable IMO. The mechanic just needs to do the best job he/she can when building the bikes.

7. Cranks -- crank arms should be tangential to the wind, or at least consistent for all tests. If you angle them up/down, the crank length matters a tiny bit.

8. 2x on using the same saddle and height. Should also use the same elbow pad, or no pad at all.

9. Back to 4. I would use a good stack and reach tool to measure and re-measure the bikes. The skeleton should be fixed and the bike be made to fit that position, not the other way around.

10. Good luck! This is great and very ambitious but all the best. Let us know more as you continue in the process.

And the wind tunnel aero helmet/mannequin thing I did with a friend as a senior thesis at MIT. We tested 14 aero helmets at 3 different yaw angles and 3 angles of attack. PM me your email and I'll send it over. Or someone tell me how to post a file up here. I keep forgetting how. We can get a thread going on that study. It was pretty extensive and showed the range and mean improvement with aero helmets in the marketplace.

Cheers,

Mark

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Mark Cote
MITAerobike
Specialized Bicycle Components

I'd add one more bike frame to the mix...the BP Stealth or Martec frame design. This is a competitor to the Titanflex style of bike in the style of the old Lotus superbikes...and afaik there is no actual tunnel data anywhere on it. I ride a size medium and would happily send the frame/fork off for testing if you are interested, as long as it isn't in the middle of race season when you finally determine a protocol and run the tests! I'm actually featured on the splash page for http://www.bpstealth.com at the moment.

I'd be very interested in a third party objective evaluation of the frames. I'd considered going to NC myself (and still am thinking about it) for a tunnel session, but it would be valuable to me to know if my bike is decent/crappy/competitive with the best that's out there before bothering.

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Sent you a PM in regards to loaner bikes. Have a Pinarello Montello FP8 and LOOK 576 available. Also have access to a few more such as Fuji D6 and Jamis should you wish to include them.

I would really like to lend help in this as far as being at the tunnel to provide physical man power for moving bikes, set-ups and documenting if needed. I sent you my contact info in an email. Thanks.
-Mike

Do you mean this study?

http://dspace.mit.edu/handle/1721.1/40486

That was linked to in a thread here last week on aero helmets:

http://forum.slowtwitch.com/...ing=helmets;#2557630

I wouldn't mind it if you emailed or PM'd me the "decoder ring" for the helmet identification though ;-)

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http://bikeblather.blogspot.com/

Working on it. It would be sooner rather than later. I'll let you know about chipping in. I also don't know how the data would be presented, where, etc.

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Brandon Marsh - Website | @BrandonMarshTX | RokaSports | 1stEndurance | ATC Bikeshop |

Assuming I have a road bike by next year I'll loan you my 596. The only thing is that it is a XS which probably is similar to a 51 P3C. I don't know what size range you are trying to stay within.

Exactly what I was thinking. Which is which?

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Want: 58cm Cervelo Soloist. PM me if you have one to sell

Vintage Cervelo: A Resource

Dave,

My P4 (54) is gonna be hanging on the garage wall from now until early March, so if you'd like to have use of it during that time for this, let me know.
-M

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float , hammer , and jog

Thanks for the reply. I hoped you would. I have been kicking this around for some time and running projected costs and just decided to go for it today. Mike Giraud has an email, and if he is interested, I would use him exclusively.

As to the tunnel time and $$, I am probably going to address this by culling the list a bit and making it most relevant to buyers of a new bikes who place primary emphasis on speed over style. I would rather test the fastest bike from each manufacturer, rather than all of them. We already have a good idea as to how the P2 compares to the 3 and 4 so why spend the time and money. Probably won't test bikes like the Ceepo Venom as buyers of those are not primarily interested in aerodynamics, IMO.

One wheelset makes the most sense. I was waiting for more specific info as to how long this will all take per run and you provided it first. Thanks. Question I would ask is, why so long for full yaw sweeps?

Spacer stacks is the biggest issue I have run into so far. I would love for donor bikes to be all the same but yeah right... I think I am going to go direct to the manufacturers and see what they have to say. Along these same lines are the bikes with proprietary seatmasts that need to be cut to fit. Daunting logistics to be sure but I intend to do this right or not at all. Leaning heavily towards doing it right however.

Advice taken on cable routing. I just learned that there will be plenty of time between runs and having two identical set up for this is probably the way to go.

3 hours passed since I started this post, gave me daughter anap, cooked dinner etc. Got an email from Mike at A2 and I should be speaking with him on the phone tomorrow.

Honestly my biggest concern with this is not going broke. If I knew right now I could break even and never make a dime I would still do it cause it ain't about the money. I think this needs to be done.

Dave Luscan

I definitely agree that you can not "post-process" the results in terms subtracting/adding drag for a spacer stack. The flow off the tip of the cylinder stack is complex and different frames will interact with the shed wake differently. If you are limited to borrowing personal bikes, I believe the most uniform way to test would be to set the test stack to the max stack out of your sample of bikes (as you have previously suggested). It should be relatively easy to raise the stack on bikes with steerer tubes cut too short (using some sort of temporary strut to clamp the stem to; the strut can be bolted into the star nut and would then be sheathed in spacers to maintain the same O.D. as the rest of the steerer). Hopefully the range between max stack and min stack is minimized by carefully choosing frame samples. This method, of course, will benefit new bikes such as the Shiv (since the desired stack will need to be reached using pad spacers instead of steerer tube spacers).

Chris

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Chris Yu
Applied Technology
Specialized Bicycle Components
@chrisyuinc

Dave,

Sent you a PM about a loaner bike. I wonder if it won't be better to test bikes with either a flat or bludge disc depending on which is optimal for that bike, so we would determine the fastest overall system. A TTX for example is supposed to be faster with a bludge disc than a flat, and a P4 will only take a flat disc. Just a thought. That might make things too costly though. Sounds really cool.

Dave, I would add the Blue Triad to the list, I know they offer free wind tunnel testing at A2 with purchase of bike and that they have bikes for testing at A2 so it should be fairly easy to talk to Chance at Blue and see if they would be in.

Kevin

I've got a L transition you can use depending upon when you do it.
We start racing in Feb out here.

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Brian Stover USAT LII
Accelerate3 Coaching
Insta

I've also been meaning to ask (either you or anyone else who knows) whether facilities (A2, LSWT, etc..) have the capability to back sweep at shifted yaw angles, so as to not repeat the same angles as the forward sweep. When I used to test in our tunnels, we would offset the sweep coming back (only repeating the zero angle point) to get a better idea of what the force curve looks like and more importantly better define any flow hysteresis that may be masked by sampling the same points.

It would admittedly be hard to tease out with limited sweep angle resolution, but signs of significant flow hysteresis could point to "reluctance" of certain stalled areas to reattach in dynamically changing yaw situations; usually a bad thing in the real world. I'm just thinking aloud here about other ways a bike can be better aerodynamically than another...ie; even though drag is lower in steady state for bike A, bike B may be dynamically better if it manages separation and reattachment better than bike A. This is probably a higher order effect though, as yaw angle would have to change relatively rapidly throughout a ride for this to matter.

Chris

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Chris Yu
Applied Technology
Specialized Bicycle Components
@chrisyuinc

 

You can use my Softride TT7 but it is large size not medium.

I can tell you the results of the test already:

Second place - The Cervelo P3C

First place - Everything else..............


Hugh Blake

Moving along on this as fast as possible.

Looking at the sourcing of bikes with regards to issues of size, spacer stack and proprietary cut-to-fit seatmasts, I have decided to go right to all the manufacturers first and see what they have to say/contribute. Expect to see a wide range of responses there.

As this has really snowballed in the last 24 hours, I will say again, this will be done right, or not at all.

Dave Luscan

I wonder which marketing departments have already started working overtime to come up with excuses!?!


I've been thinking about this.

I'm beginning think that the effect of extra spacers above the stem won't actually be that bad as they would follow the basic aerodynamic drag equation fairly closely so could be calculated out (although this calc would need to be shown obviously).

The additional spacer stack will be above the stem and thus at least that far above the top tube. What that means is that it will be dealing with slightly messy air off arm rests etc. but the wake won't strongly interact with the top tube or any other part.

I should point out that I'm assuming that the vertical component of the velocity won't be adversely affected by the angle of the spacer stack.

Otherwise, I agree with MIT's points.

I've been trying to work out how to get more money for this test. Is it possible that you could get sponsorship whilst keeping the test impartial? Sponsorship from a wheel or component manufacturer? The tunnel themselves? A magazine who aren't interested in pandering to the manufacturers?

One other thing might be interesting to throw into the mix since you are going to all this trouble. When you are looking at aero helmets throw in a look at their cooling ability. If you are going to use a standard manequin it would be easy to put a thermocouple on a moist head and see where the temp leveled out at below ambient in the tunnel. This would give you a good indication of the relative cooling ability of the various helmets.

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Frank,
An original Ironman and the Inventor of PowerCranks

That's a seperate study entirely. We've tested this on a mannequin and subject in >30deg heat conditions, and found no difference between a regular helmet and an aero helmet with vents uncovered.

Xav

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AeroCoach UK
http://www.aero-coach.co.uk

Where are your results and protocol?

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Frank,
An original Ironman and the Inventor of PowerCranks

In a drawer. This is off-topic

Xav

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AeroCoach UK
http://www.aero-coach.co.uk

What helmet did you use. I find it hard to believe that no wind and wind yield the same temperature.

Maybe . . . hopefully . . . possibly I am wrong, but I will be AMAZED if you get any cooperation from the manufacturers.

Most of them have an active self-interest in NOT having independent data made available. My guess, if the manufactures aren't in control of the test protocol and the presentation (read manipulation) of the results, they will want no part of this.

Again, hopefully I am wrong. But I doubt it.

I remember an older study, but wouldn't be able to put my finger on it that came to the same conclusion. I believe A Coggan has mentioned the same study, he may be able to put his finger on it.

Styrrell

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Styrrell

While I agree that the drag on the spacer stack itself can be characterized decently well via test or simulation (I am not aware of any basic aerodynamic drag equation for a non-infinite shedding cylinder....unless you are thinking about empirical fits/models on tests of similar geometries), I think the bigger issue is the interaction effect with the rest of the bike. Although (as you pointed out) this effect is very small relative to the absolute drag on the spacer stack, it may or may not be negligible relative to the drag differences among different bike frames (the original question we are trying to answer). It sounds like you know what you are talking about, so I'm interested in your thoughts (perhaps I'm emphasizing a level of precision that is completely unnecessary...). Also, as a practical point having extra spacers above the stem may make it harder to compare with bikes like the Shiv/Trek Speed Concept where this is not possible....whereas spacers under the stem can at least be comparable (in terms of real world setup) to arm pad spacers.

Also, I wanted to ask anyone that knows: What is the data acquisition rate on the force balances in question and what is the typical sample duration?

Chris

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Chris Yu
Applied Technology
Specialized Bicycle Components
@chrisyuinc

Then, my comment stands. Perhaps he should consider adding this to his protocol.

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Frank,
An original Ironman and the Inventor of PowerCranks

Isn't it a rule of thumb that about 25% of the bodies cooling comes from the head? There are three main methods to transfer heat to cool the body: conduction, convection, and evaporation. The helmet could alter all three. Seems unlikely there would be zero difference between helmets, let alone between a standard helmet and an aero one.

I would like to see the protocol and to have it confirmed before I "believed" such a result.

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Frank,
An original Ironman and the Inventor of PowerCranks

Perhaps in a free convection state...but, what about forced convection?

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http://bikeblather.blogspot.com/

As I think about it the amount of cooling in the sweating athlete due to the head is probably less than 25%, although the head still probably contributes more than its fair share based upon surface area considerations alone since it is so exposed to the wind relative to other body parts, usually (unless encased in a poorly vented helmet perhaps).

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Frank,
An original Ironman and the Inventor of PowerCranks

My thinking was based on the idea that by looking at a stem with a steerer cap, you're already looking at a cylinder with one end (the bottom end is integrated into the bike). Even with only a stem, there will still be a top end to the cylinder. I'm not suggesting removing a non-infinite cylinder [by calculation], I'm suggesting removing a small infinite cylinder from an exiting non-infinite cylinder.

The bit that will cause errors is the air flowing down after going over the top of the steerer top cap. I'm making the following assumptions about this flow:

a) The vertical component of the airflow behind the stem is near 0 when it reaches the top tube. This means that we won't affect the airflow around the top tube by adding a spacer stack.

b) That the vertical airflow passing over the steerer cap and 'dropping' into the wake of the stem is damned nearly the same as the vertical airflow dropping into the wake of spacers.

If either of those assumptions are wrong then ignore the idea; it's much more difficult to remove a chunk of cylinder by calculation.

Edit #7 - Dang, the Spec Transition with it's top tube fairing of the stem is number 8 on the list of bikes to test. That would be essential test without a spacer stack on top of the stem.

Edited several times to make my thoughts and words correlate!

BTW Dave, big kudos for attempting to do something that (almost) everybody on ST says should be done, but hasnt attempted.

Kevin

 The "First Annual Slowtwitch Wind Tunnel Shoot Out" has a nice ring to it:)

Slowman?

-Scott

Ah, I see what you are thinking. I was imagining that the flow leaving the stem with a top cap (ie; no spacer stack) was more akin to a trailing edge flow (treating the cap as part of the stem 'fuselage', and the stem as a slender body). If this is close to reality, a spacer stack would substantially modify the flow field to one of a shedding cylinder tip. Again, I am just poking and guessing here since I have no direct experience with flow fields on a bike (this is the cue for Mark to jump in with his expertise).

Putting aside the fluids babbling, I'd like to add to the praise that Dave is getting for taking on a project of this size. Let's hope it all works out....

Chris

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Chris Yu
Applied Technology
Specialized Bicycle Components
@chrisyuinc

LOL

I guess you beat me too it. One of the reasons the head is a bigger sink under normal circumstances more blood flow goes to the head. When exercising the limbs will tend to vasodilate as you start to sweat so, it would seem the percentage loss from the head would drop.

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Frank,
An original Ironman and the Inventor of PowerCranks

Hey Dave, kudos for your ambitions to address a hot and sticky topic...as indicated by the Slowtwitch buzz/firestorm.

As a small manufacturer I've had the same dream, but lacked the resources to bring it to life.
I'd be honored to have a TitanFlex in the game. Just let me know when and where to ship the new stretch model.

Acknowledging the difficulty in normalizing for the proprietary aspects of individual frames*, I trust your judgment in constructing a test protocol that is transparent and impartial. I also appreciate how tedious/costly it would be to satisfy everyone's pet concern. That said, here are my suggestions:

1. Because you're not testing saddles or seatposts I like the idea of attaching a "blob" to the saddle/seatpost.

2. I also like the idea of standardizing the stack height. If need be, put stack spacers under stem. Maybe just make the elbow pads the same height above the ground/bottom bracket. In the interest of simplying the set ups, I'm okay with using a standardized front end "blob/nosecone" as well.

3. As one poster mentioned, forks should also be normalized--to something close to the Shiv's if it is tested. TitanFlex uses a 1" steerer and I would be happy to include an Easton EC90 Aero fork you could cut down.

4. For obvious self interests, I question the inclusion of frames no longer in production (Lotus, Hotta, Zipp, etc.)

That's all I got for now. I'll continue to follow the thread, where considerable expertise has been showcased...along with a few distracting/obnoxious posts (par for the course).

Cheers,
Tom Piszkin
UCSD Masters Triathlon Coach

*The P4's integrated water bottle comes to mind. I can imagine Cervelo designing a test that required all frames to carry water! A TitanFlex sponsored test would require all bikes to be tested with riders sustaining an aggressive aero position for 3 hours while somehow simulating rough roads.

Disagree on a universal fork. I designed the 4000 and the Airfoil fork to work directly with the frame.

This is where wind tunnel data is subjective.

The goal with Kestrel is to match fork, bars, post, etc together to make a fast BIKE, not just the frameset.

To get fair data, the complete bike as presented to the customer should be tested, and really a rider should be in place to see how the complete unit (bike and rider) work together.

None of the bike data matters if the complete unit isn't tested.

I agree with Seve on the fork/post issue. The fork affects the flow over the entire bike. The fork and seatpost are part of the frame.

Aerobars, not so much. The extensions don't matter - arms cover them anyway, so might as well stay consistent. Basebar makes a huge difference in aerodynamics, but that's all out to the side, where it doesn't really interact with the rest of the frame.

It's quite common to buy a high end bike with low end components, expecting to change the aerobars, seat, and chainring, so there's no reason that those parts should have to match the bike.

You're crazy. Almost no one I know rides a "stock" bike. Everyone rides with race wheels that didn't come with the frame as most of the time finding $10k all in one place is tough, but a bike one year and race wheels the next is pretty common. Some people upgrade the bars and cranks etc. Anyone who cares about a bike past fit and color want to know what the frame alone does to performance.

This sounds like another defense of your bad, unexplained wind tunnel tests.

Ken

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"the trick is to keep losing weight until your friends and family ask you if you've been sick. then you know you're within 10 pounds. if they start whispering to each other, wondering if you've got cancer or aids, you're within 5. when they actually do an intervention, you're at race weight." - Slowman

EXACTLY but don't you want to know what parts work best with YOUR bike??? Why just get a set of wheels or bars if you don't know the real affect it has on the rest of the bike????

To me, a complete bike is the way to test and a rider on the bike to back up the results is our final test.

If you are testing frames, great but personally I want to know what bars, stem, etc. affect the frame so I can build the fastest bike. A simple test we did was to create 3 different forks to see how they worked with the frame and the wheels. We used the fastest of the three to compliment the frame. To me, this is incredibly important.

I also tested multiple bars with the bike. I wanted to see how each bar worked with the frame and fork.

I want to know how spoked wheels and trispoke wheels affect the frame and how deep rims or shallow rims affect the results.

My goal is to test bikes, give details on the complete bike.

All that said, I also understand that testing a frame is somewhat important and offered up the Airfoil and the 4000 to be tested.

The most important data I have learned in the tunnel? We in the industry can do all we can to make an aero bike however the percentage of athletes poorly fit on a bike counter act all the aerodynamics from the bike.

So, fire away on the tests, I'm happy to present all of the Kestrel bikes that are requested.

The problem with the methodology is that most people who care about wind-tunnel data are NOT going to use the stock set-up put together by the manufacturer. Most people in this group have their own race wheels, saddles, tires, and aerobars. In that case, how the bike tests as built up by the manufacturer is irrelevant outside of the frame.

Again, disagree.

So you are telling me if I tell you that your wheels won't be as good as XYZ brand, you don't want this information?? Or if bar XYZ works better, you don't want to consider keepig the parts that came with the bike on there?

Trust me, I get it. I owned a store for 15 years. I understand customers want to make changes but in those 15 years of ownership, I would have loved to know what parts worked best with the frame.

My guess is that the consumer would too.

So you are telling me that Kestrel tests every possible wheel and aerobar in the wind tunnel and specs the ones that, in tandem with the particular frame, produce the lowest drag?

You spec bikes with non-race wheels all the time. Are you trying to say that your bikes will be faster with those wheels than a set of Zipps I might have in the garage? Give me a break.

All bars and wheels, no, but many of the most popular ones. That's the advantage of the A2, they have most of the product there and vendors also provide me with lots of product to test.

And no, of course a Mavic wheel isn't as fast as a Zipp. Point is that the Zipp wheels I used tested faster then a 404 or Hed Stinger on my bike.

Again, the idea really is to use what we learn in the tunnel to your advantage. Many of us in the industry spend hours in the tunnel learning and it's rare to see a consumer in there who has the ability to test like we do.

Even if you independently test frames, there is still the advantage of knowing what parts compliment that frame.

And with that, it's time to go enjoy Halloween

Please do enjoy Halloween!

Also, I understand that you spend a good deal of time in the wind tunnel and here on ST dealing with us. I just want you to know that it is appreciated. I am not trying to rag on you. Just trying to get to the truth.

I agree entirely with this comment. There are some components that few people seem to change and the forks are one of them.

I don't really agree with this comment though, but there is no correct way to test a bike and as such, testing should be representative of what people want to know. For me this comes down to the question of what most people, who want to see this data, buy; F&F (plus trimmings) or complete bike. If it's the first answer, then you need to standardise components.

I think that the idea of testing with a person is a really bad one though; it's just a source of inaccuracy.

edit - you didn't run your tests with a rider and then calculate him out did you?

Are we ever going to get clear answers to the questions repeatedly posed to you in the other thread?

Able to lend: medium/56cm Fuji D-6, 54 or 56cm Ketrel Airfoil Pro

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wovebike.com | Wove on instagram

Steve makes a good point about forks. The front end of the bike is the most important aero-wise. Because some frames sport integrated/proprietary forks I revise my first comment and say let each frame manufacturer donate whatever fork they want tested (provided it's available to the public). It's the only way to fairly represent real world/market conditions.

Tom Piszkin
UCSD Masters Triathlon Coach

If you get one of these could you test it?

Ambitious project... good luck

the idea is very interesting/intriguing.

If you have any need for a small TTX (actually about a 54), or a round tube Merlin Ariel, or need a round tube roadie I don't mind lending them out for this test.
My one question is on wheel choice for the tests.
Why test with something like a 1080 on the front when very few people actually race with a 1080 on the front?
To me the more logical choices would be:
HED Stinger 60 front, 90 rear/Stinger disk
Zipp 808 front, 1080 rear/900 disk
and then maybe a comprable clincher version of each.

I also think that each bike should be tested with the seat post that comes with it and fork rather then trying to standardize those.

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Mike Plumb, TriPower MultiSports
Professional Running, Cycling and Multisport Coaching, F.I.S.T. Certified
http://www.tripower.org

What else do you need to know?

This will be incredibly useful information for me the next time I send my bike to a race.

Wait a minute: I don't send my bike off to races, I take it to races. I ride my bike in races.

It may be academically interesting to know which bike frame is most aerodynamic, but without data that can in some formula correlate that data to the drag from the rider/bike combo, this information is specious at best, and may be totally misleading in context of selecting a frame for the real world.

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http://www.whydoesgodhateamputees.com/

Sigh....

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http://bikeblather.blogspot.com/

Tom-

Most people are like goldfish - nothing but very short term memory.

Kyle published such data >15 y ago.

What wheels, handlebars, etc., were used on each of the three bikes that were tested.

If the bikes were tested "as supplied to the consumer" as claimed in the figure legend, then how/why do you think it is fair to compare framesets fitted with different components (esp. different wheels)?

If the bikes were tested fitted with the same components, then why does the legend of the figure say "as supplied to the consumer"?

Depends per wind tunnel but the ones I've worked at, I've run at 100 Hz and test 10-30 seconds for equipment tests and 40-60 seconds for athlete tests. I've run as high as 10 kHz and as low as 10 Hz and the data has averaged out well (i.e. can capture everything needed at 10 Hz depending upon the design of balance). For solid balances like SDLSWT, A2, MIT, Texas A&M, UWAL, data collection as slow as 10 Hz is good. In CO, we had an air bearing based design and we collected data at a bit higher rate (100 Hz+).

I prefer testing 100Hz+ due to the intense vortex shedding that occurs off of the tubes at yaw above 10 degrees.

When we do equipment tests, we've studied how quickly we can test each yaw point (run) at each tunnel. At A2, 10 seconds has been plenty. No difference between 10, 20, 30, or 40.

Also, so everyone knows, the A2 tunnel doesn't do "sweeps" of yaw angles at this point. They move the balance, let the wind settle to a steady state condition, then begin gathering data. The data does not change based upon the direction you change yaw angles (i.e. negative to positive yaw or positive to negative yaw).

MC

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Mark Cote
MITAerobike
Specialized Bicycle Components

Do you think/find that doing "fixed" yaw angles makes a difference due to not having flow attach or reattach as the yaw angle changes? Or does it all tend to come out in the wash?

Kevin

Mark, thanks for your expertise here. And spot on as to how A2 tests yaw. I will be holding off my testing until they update the tunnel mechanism to provide faster yaw testing, as well as possible yaw sweeps. Scheduled for sometime Q1 of 2010.

Dave

This was what I was wondering about. Your preference makes sense given the typical Strouhal number for shedding cylinders (of bicycle tube size and at bicycle speeds).


Sorry, I used the term "sweep" loosely...I actually meant what you are referring to above. From the pictures, it looks like the entire setup is on an electronic turntable. Is the typically coarse sampling resolution in yaw (usually every 5 deg) due to practical concerns with tunnel time, or some other technical reason?


This is actually pretty interesting. I wonder if this is due to either 1) nothing has fully/catastrophically separated at the max tested yaw, or 2) the yaw sampling resolution is too low (for an airfoil that stalls at eg; 20 deg AoA, I have seen hysteresis confined to above 15deg AoA on the back sweep). If neither the above is happening, then something else interesting is going on...

Thanks for the info! I'll admit this stuff isn't directly relevant to the bike shootout test, but it's satisfying my curiosities and I'm learning a lot here...

Chris

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Chris Yu
Applied Technology
Specialized Bicycle Components
@chrisyuinc

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Mark Cote
MITAerobike
Specialized Bicycle Components

Cool -- I chatted with Mike Giraud about this on Thursday and we both agreed it made sense to hold off until the new automated system is running. We're pretty stoked about the upgrades.

Thanks to everyone on these conversations. This is where progress in the bike design world happens -- through conversations like this. I look forward to the first Cycling Aerodynamics Symposium we'll have to pull together sometime in the future.

Cheers,

Mark

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Mark Cote
MITAerobike
Specialized Bicycle Components

Good luck keeping the information private.

Thanks for your helpful contirbutions as always Matt. I realize that protecting the data after the fact presents some challenges. I do imagine this can happen, which begs the question... Can you do it? ;>)

Dave

Correct, that's the St range I was thinking of (and if I remember correctly, it stays amazingly constant over broad Re). Yes, it makes a lot of sense that these effects may be academically interesting but probably have relatively little influence in the grand scheme. Then again, you never know what small physical phenomenon (once discovered) can be harnessed to produce a much larger effect (think vortices on a flapping insect wing). Of course this is all limited by what is practical....not very much in consumer bicycles as you have mentioned before. We need to get the military interested in fast bicycles....then wait for the gov't grants to roll in =P. I also agree that the next "big thing" in testing is having the ability to study dynamic situations - both in terms of drag performance and in handling as you suggest. The planned upgrades to A2 sound like an exciting first step in this direction.


If this is actually the case (and I have no reason to believe otherwise), it needs to be underscored how impressive this really is. To delay significant separation for ~5 deg is huge, especially given the design constraints in making a bicycle.


Definitely. Just give me a holler whenever.

Chris

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Chris Yu
Applied Technology
Specialized Bicycle Components
@chrisyuinc

There are several options but my consulting is not free since it's what I do for a living. You can PM me and I can set up an arrangement to detail some options to you.

Are you taking notes MITaerobike? ;-)

What are $ estimates?

I expect to pocket somewhere in the low 7 figures. ;>)

sorry to bump an old thread, but any update on this endeavor?

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Hungry for tri!

Maybe they're not interested in aerodynamics because they KNOW that they can choose most any bike on that list and as long as they get one that fits them very well it won't be the bike that determines how fast they are. It will be 1) how hard they push the pedals, 2) their position on the bike and 3) how well they execute the race. The differences in bike aerodynamics on basically all of the top bikes is insignificant.

Sorry if I sound completely negative and harsh but I have zero interest in this data. I think it's mostly a complete waste of time. Where people should be spending their time and money is on improving their position on their current bike. Hell, they'll probably be faster if they spend their time going on a proper diet and lose something like 5 lbs. Most importantly, spend time and money that help you focus on the 3 things above.

Thanks, Chris

Absolutely agreed. I realize that this place isn't likely actually taking away from anyone's training time, but honestly the amount of mental effort the average AG'er ptus into things like aerodynamics and equipment is much better spent thinking about training and race execution. People like to spend money, and that's fine, it's what keeps the economy going - but if someone's true goal is to get faster, there are WAY bigger fish to fry.

I totally agree with your statements regarding the vast majority of age groupers. But some of the detailed oriented people are trying to ring out every bit of performance from our equipment choices. If I can save 45s/40k just from switching frames that could be a slot/no slot choice for me. Thus I am interested in the data. This is low hanging (expensive) fruit IMO.

Yes and no. Look at the flailing cables at your next triathlon. They likely wont be neat and tidy even on a P3C. This is an example of people spending big cash but not thinking of aero details.

To me, winter time is aerogeek time to establish the vehicle my trained body will be riding this spring/summer.

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Want: 58cm Cervelo Soloist. PM me if you have one to sell

Vintage Cervelo: A Resource

I hear what you're saying as I obviously took that into consideration when I made my post. However, I believe people will discover that frame aerodynamics will vary depending on rider position. So, what you think might be the fastest frame via wind tunnel testing (where you were not a participant), is not the fastest frame for you. The fastest frame for you will be dependent on your position on that specific bike. Hence my statement applies to the typical AGer and the detail-oriented one too. Sometimes the problem with certain detail-oriented people is that they're focusing on the wrong details.

Thanks, Chris

Bump... any update?

I am in a holding pattern on this. Folder with test protocols, contact info etc sits on my desk getting dusty (with a few others). The multiple logistical challenges are surmountable, time and $$ not so sure.

Blowing the dust off this thread! Did this ever happen???

If not, is there anywhere one can find independent aerodynamics comparisons?

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-Jason
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Is that all you've got? Are you sure?