Maybe this is a dumb question, but how does it calculate angle? Is more than one pitot tube needed to capture direction? I thought a pitot tube only captured a linear velocity along the tube axis.

I was trying to look up the sensor Flo used, and it doesn't seem to be in production anymore. But the same company has newer more solid-state-like sensors that seem to use arrays of transducers to presumably do some vector math to calculate direction. Kind of interesting.

Sorry, my thought experiment was ill-formed - ignore it.

To answer your specific question, though, each point on the graph is indeed an average value (as described in the paper, which you seem not to have read).

The airport control tower, correct, and direction data were only obtained at the end of each run (by radioing the tower and asking.)

(This was pre 9/11, so Jim was able to gain access to the airport taxiway simply by asking nicely. The airport was still open, though, so there were several times we had to all scramble out of the way of a corporate jet that had just landed or was getting ready to take off. A bit surreal, that.)

If they did, why woudn't they have told us? It's a big marketing bonus if they are accounting for conditions that others aren't.

They'd want others to continue to not account for those conditions? Trade secret kind of stuff.

The tip is multiport, with 3 precisely machined openings in the rounded end. One in the center and one on either side of it. Each of those ports are hooked up to a pressure sensor. Additionally, there is a ring of tiny holes further back on the tip on the cylindrical part. Those are there to get the free stream pressure.

Apparent wind angle and magnitude are determined from the output of all three of the tip port pressures, in comparison to the "ring" pressure.

I took a quick look at some previous data files had, and I mis-remembered. Although the WASP unit I'm using to receive the ANT+ signal can handle the 4Hz data, it looks like the files are recorded at 1Hz.

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http://bikeblather.blogspot.com/

i built a beta probe a few years ago and published some results on my blog - from what I remember, I experienced a lot more beta in the testing I did compared to what has been promoted here in slowtwitch-land:


http://biketechreview.com/...rement-at-a-distance


http://biketechreview.com/...le-probe-calibration


http://biketechreview.com/...9-overtaken-by-a-car



http://biketechreview.com/...g/520-laps-with-wind

http://biketechreview.com/...log/521-gps-and-beta



and here is a parts list of my setup - oh, yeah - garage science at its best! ;-)

http://biketechreview.com/...t_biketechreview.pdf



I _generally_ remember cobbling up the arduino sketch that drove the data acquisition...and the reported betas in the links/images above were most likely average values over a given reporting interval...iow, reported betas have been damped.




ETA: glad to see someone else chiming in on damped beta measurements of the past ... :-)


https://forum.slowtwitch.com/...ost=4803288#p4803288

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Kraig Willett
http://www.biketechreview.com - check out our reduced report pricing
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Most people buying wheels (the great majority I'd guess) are going to rely on test results and word of mouth. Now that the "consensus" is to focus on <10deg, it wouldn't be smart for Zipp to design for high yaw and not tell people why.

I agree. I'm all for a reasonable level of transparency. FWIW, however, Zipp is also not telling us they're designing for low yaw, or, if they are, why. They aren't acknowledging/accepting the consensus. It's a veritable vacuum of information from them, except Josh here, who left years ago. And the little they do share focuses primarily on high angles - though mostly in the context of "stability" rather than drag. They don't even have comparative testing results among their own wheels.

That will be another reason why hambini doesn't see the same r^2 with his own testing, clearly averaging will increase r^2, e.g. I just spent a few seconds extending my monte carlo simulation to generate two samples and average them:

There are reasons for their (Zipp's) opacity...

As opaque as your post? :)

Looks like more wheels have been added and there is a new 'winner'.

Are these wheelsets tested as pairs? The latest update mentions a planet x disc and deep section front

That new winner will stir the pot quite a bit!

I think it says the same thing that most people here always say. Ride a disc unless you aren't allowed.

I really wish that was done as a stand alone front or front/rear Planet X 80 to compare how much is rear disk vs front. We don’t seem to have data on the Planet X front otherwise.

On first blush, yes. However the rear disc tilts things in favor of that combination considerably. At 15 degrees of yaw at 40km/hr a disc over an 80mm rim can easily be worth 5+ watts. At 50km/hr I could see that delta grow considerably. The final factor, which is unknown, is how Hambini's transients would affect a disc. As Josh@Silca recently pointed out, going from 0-30 yaw does not yield the same results as going from 30-0 yaw. Sweeping "in" results in flow reattaching at a lower yaw than flow would otherwise detach. My gut feeling is that a disc would be less affected by this thus its performance delta over an 80mm rim at yaw increases.

When possible, ride a rear disc :)

From the Hambini test result page (link in OP):



Whats up with this? I have no horse in this race and have previously called Hambini out in this thread for the sometimes condescending tone with all the "we're rocket engineers we know better" but do people need to be careful now when they conduct aero tests and post their own findings?

Not a great response from them imo, though I wonder if they had more of an issue with the statement in the blog post that they "had a limited understanding of aerodynamics of rotating objects".

I'll be honest, as interested as I am in the findings, I'm completely turned off by the tone of the writers.

With Hambini and crews response was there really any other way?

Yes. Ask for their protocol, take the fastest wheels they tested, and go back to the tunnel. Flo resorting to a threatening letter is childish bullying especially considering that they do not have the resources to actually follow through with their threat.

Ok before this gets out of hand, ABSOLUTELY NONE of this is true. There are no lawyers involved, no letters have been sent, we have never asked to have our power figures removed from the study, there have been no threats of court action, and we do not pay any of the forum members on this forum.

I really have no idea what Hambini's is talking about or what he is trying to accomplish by starting this rumor.

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Chris Thornham
Co-Founder And Previous Owner Of FLO Cycling

How would you know what Flo's resources are?

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Make Inside Out Sports your next online tri shop! http://www.insideoutsports.com/