When did I say that my theoretical improved design wouldn't include a rear wheel fairing?

In point of fact, it does (currently made out of shaped foam glued to a piece of aluminum that is screwed into my lower bottle cage mount.

It's the space above the wheel but below the rider that I tend to dislike, mostly because I have a 37" saddle height and there is a LOT of space there for me.

When my fairing is actually finished and usable, I will post a picture.

Chris

How come it does not happen?

I know they have them in stock - not sure on sizes and what size you need.

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Steve Fleck @stevefleck | Blog

The two bikes you mentioned that Cervelo could improve Zipp/Softride were both seattube-less bikes, so I drew what seemed to the logical conclusion from that.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

So at yaw angles close to zero.


How are you measuring power?

The orientation of the track I test on is approximately perpendicular to the wind coming off of the bay in Eureka, Ca. Variation seems to be only about 10 degrees during the summer afternoons at this location. It's an oval track, so the bike/rider/wheels will see pretty much every yaw angle possible. That is why I feel like this type of testing, while not being accurate down to a single watt, will always be more useful as a real-world test than a tunnel.

I originally started with an SRM Amateur system and then moved up to an SRM Pro.

Chris

Well, the major flaw that I've always seen in these designs (since I was a little kid in fact) was that the air separates after the down tube and then must be broken again by the wheel with all of downfalls that you mentioned. Filling the gap so that air is only broken by the down tube and then remains attached all the way along the rear wheel gives you the advantages of both worlds.

When I say "improve", I mean find the flaws and fix them. That's what engineers do.

Chris

Sorry, I thought you were testing first thing in the morning, when there was very little, if any, wind.


Okay, next question then: how do you process the data, and how reproducible are the measurements?

Spot the engineer!

??

I'm not an engineer.

Following that logic to the extreme results in a bike like that built by Brent Trimble, which as it turned out wasn't particularly aero, at least with a rider aboard.

Really? I assumed that you were based on the advice you've been giving people and the questions you were asking!

Sorry 'bout that.

No need to apologize - I've been called worse. ;-)

That's right...he could have called you a physician .

Tom (the REAL engineer)

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http://bikeblather.blogspot.com/

Now that I might have taken as an insult. ;-)

well i can see my selve as indepent testing

and evrytime i did the testing the cervelo was faster timetrail bike then TTX
(altough i like TTX cycling wise better)

as i also have some test from giant time trail bike as well the CFD of those bike's

and the amount of work cervelo put in their bikes of aerdynamic testing is not for nothing

again hats of for that

i only would like to see that they where more open in the CFD testing
like other compagnys do example is here GIANT

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http://www.ada.prorider.org
skype ceesbeers191053

Cees,

Are you referring to the new Giant TT bike? It seems to be a step back from the new age TT-bike thought.




Never had I considered non-uci bike as obsolete as after this thread. Very eye opening.

I test at many different times of the day and collect immense amounts of data. Temperature, humidity, wind direction, wind severity, etc all at 5 second intervals. I typically make a run at least 10 laps of the 3/8 mile track, but it really depends on how small the changes I am expecting are going to be. If I am trying to resolve < 5 watts, I would probably do 20 laps. I use a pressure sensor for starting and logging times for each 1/2 lap top make sure that gusting winds are not adversely effecting lap times and ruining my resolution.

I work as a software engineer for a design of experiments and automated experimentation company, so I work with several custom tools built off of our product line to store and analyze correlated time-series data. Our company is not in any way related to the bike industry or really this kind of data collection, but since I work specifically on the import/export of our designs and response data, it's easy for me to build custom modules for my data input devices.

I work with people who are experts in numerical analysis and general statistics/mathematics/optimization and have tapped their collective talents in my pursuit of bicycle speed. I assure you that the attention to detail and repeatability of my data makes Tour Magazine's aero testing look like it was arranged by Fisher Price engineers.

Not trying to put anyone down, but this stuff is very important to me and I take it very seriously when someone publishes data that says system a is faster than system b.

There are about 2 hours a day during which I can collect reproducible data (2-3 watts) for "tough" wind conditions (when normalized based on wind angle and velocity), and about 2 pre-dawn hours when I can collect calm condition data (usually < 2 watts)

Chris

That almost looks like a geometry prototype. It's neither the Trinity Alliance nor the Trinity Carbon. Wonder if it's a one off built to test a specific geometry (or for the specific needs of a given rider)?

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Man, you guys are still talking about this? ; )

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Shawn
TORRE Consulting Services, LLC
http://www.TORREcs.com

That almost looks like a geometry prototype. It's neither the Trinity Alliance nor the Trinity Carbon. Wonder if it's a one off built to test a specific geometry (or for the specific needs of a given rider)?[/reply]

It was for rogers - they had a video clip about it during the tour. You're right on with the geometry proto theory.

It was for rogers - they had a video clip about it during the tour. You're right on with the geometry proto theory.[/reply] YES! I am SOOOOOOOOO badass... ;)

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

Rapp, any chance you'll expand on your initial thought in the BTR insiders?

I could simplify it a bit:
TTX: 32mm downtube width
P3C: 28mm downtube width

Interesting to note Cees comments that he tested the P3C as being faster than the TTX, but found the TTX to be nicer to ride. The TTX is a very stiff bike (a bit heavy with the aluminum crown fork, but I see they've changed that for the SSL) and rides very nicely. The cable routing is also excellent and nicer than the P3C with the behind-the-stem entry and full length cabling for very nice shifts.

I've certainly been very happy with it. I'm not sure I would say it is the most aerodynamic frame you can buy, but I also don't think it's gonna hold anyone back. And there are lots of other things that make it very nice. One big thing that I'm very happy with is the seatpost binder. Everyone likes how clean the Cervelo binder is (the TTX is, aerodynamically, also very nice), but I don't think they are the most secure based on people I've ridden with. Now, is a seatpost binder worth X watts? I don't know. I'm just saying that I think Cees point that there are certain things that make a bike nice besides aerodynamics.

But I know that aero also sells. It's too bad that Trek wasn't less marketing on this. It would have been fine to give the whole story - Basso, P3C, position changes, etc. Shows that the frames are close enough, shows the importance of positioning. But I guess that's why I don't work in marketing.

I've been happy with my Trek. As I said on BTR, I don't know that it's the fastest frameset in the world. But it's certainly done me right this season, except for wanting to go off course ;) I'd not have any trouble highly recommending it to someone looking for a TT bike.

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"Non est ad astra mollis e terris via." - Seneca | rappstar.com | FB - Rappstar Racing | IG - @jordanrapp

I didn't realize the Trek was 32mm wide. Thanks for the info.

There was also a comment on a BTR thread on this same graph. Someone stated that when Trek tested the bikes sans rider the Cervelo tested faster. The BTR member contacted someone from Trek and response was they believed the cleaner front end of the Trek(fok fin to downtube, cable routing) was the difference maker with the rider on board and that the better rear end of the Cervelo(seatpost shape, wheel coverage) didn't have the same effect. Take this as what it is though, second/third hand info. This theory also goes against Gerard's belief that a bike tests very similarly with and without a rider that he has expressed before on the forum.

The TTX 9.9 might be faster than a P3C but given their scarcity and unavailability it really doesn't matter now does it? Why bother with a fancy test on something you don't actually sell - what I mean by this is a shortage on supply of frames.

Trek: Our bike is crazy fast and aero, look at the pro's who ride it! Very distinguished athletes ride our bike the TTX. However, we are really sorry to tell you this but you can't have one b/c we don't actually have any ourselves to sell you, especially not the venerable 9.9 SSL (wait til spring 08 at least). Further, you have to visit a Trek LBS to acquire, don't trip on the tricycles or big wheels while you spend $8000.

Cervelo: Our bike is crazy fast and aero, look at the pro's who ride it. Very distinguished athletes ride our bike the P3c and p2c. Say, you want one? Got to your LBS and pick it up today, heck, have 5 or 10 or 12.

There is a part of the story that wasn't covered...availability ; )

Hence, I am getting carpal tunnel syndrome trying to find a used one on the net.