BikeTechReview.com

Recently, it was pointed out to me that a Ph.D. in Mechanical and Aerospace Engineering from Rutgers University reported that he has measured the lead rider in a paceline to receive an 8-10% reduction in CxA.  FWIW, I looked at this NASCAR effect about 10 years ago (dueling it out with Jobst Brandt on rbt, nonetheless!).  Here is a BTR forum link with additional info regarding  (cliff's notes is that I estimated the effect using race car data at around 2-5% at the time IIRC...but even that might be a generous estimation):

biketechreview.com/index.php/forum/1-general-discussion/3573-blast-from-the-past

...here's some inviscid analysis to also help ballpark the expected effect (figure 5 is the one of merit, remembering velocity is related to pressure):

http://biketechreview.com/index.php/performance/demand/478-flow-stagnation-ideal-fluids-and-you

..and here's some reported data off of velonews from over 10 years ago regarding the topic of "lead rider in a paceline" aerodynamics:

http://velonews.competitor.com/2002/12/bikes-and-tech/technical-qa-with-lennard-zinn-the-aerodynamics-of-drafting_3330

I'm not quite sure what is going on with the previously mentioned Ph.D's methods/instrumentaion, but it is at odds with multiple independent lines of inquiry.  A 10% reduction in CxA is quite significant, and really wouldn't require anything fancy in order to detect this kind of effect at track pursuit speeds...so, it's surprising that it hasn't been reported more frequently...

About 4 or 5 years ago, I was helping out a world champion and multi-olympic team member with some field testing at the ADT center in Los Angeles.  We'd previously tested in the tunnel here in san diego and we were just checking some things out (I'm a fan of multiple independent lines of inquiry y'know!).

One key parameter to keep an eye on is air density as a function of time while doing aerodynamic testing.  I had my data logging Kestrel in hand at the time, and it was a good thing...y'know, cuz, even when you think air density is constant indoors (i.e, temperature, pressure, humidity are stable)...well, it isn't:

I just dug this one up:

https://docs.google.com/a/google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US20120221257.pdf

...and quickly checked the public disclosure dates made to folks by the inventors on the now-defunct google wave (and personal emails to me) regarding their ideas.  Seems as if they beat the 1-year deadline by a week or so based on those dates.

Despite the real possibility that the inventors missed the 1-year application deadline due to some other public disclosure I am not aware of, my limited knowledge of patent law means that since they disclosed prior to filing an application they would not be eligible for patent rights in japan or europe (where no 1-year grace period post-public disclosure is allowed).

It will also be interesting to follow the prosecution and see how the examiner decides on the topic of "obviousness".  For example, I would consider myself as skilled in the art of determining CxA via virtual elevation methods (among other techniques), and the beta/wind problem is a well known one.  This problem was one of the reasons I built this embedded system last year (complete with a BT radio to send results real-time to my smartphone):

http://biketechreview.com/index.php/blog/516-measurement-at-a-distance

http://biketechreview.com/index.php/blog/517-wind-angle-probe-calibration

http://biketechreview.com/index.php/blog/520-laps-with-wind

Furthermore, I think the patent application misses the dependence of CxA on reynolds number, and Crr on speed+surface when creating a virtual elevation profile...ooh, maybe I should patent that!

...The clock's a ticking, now, though!

Words and Images by Kraig Willett

In 2002 I bought a used SRM Pro powermeter.  I’ve had the crank battery replaced once in the past 9 years (less than 20,000 km).  Since day one, the powercontrol (the head unit) battery has been a bit problematic.  First of all, the display that supposedly shows how much battery life was remaining was unreliable.   For example, the PCV display might have said that I had 25 of 29 hours left on the charge, but inevitably, it would run out after only a few hours.  Secondly, and probably related to what is mentioned above, is that the battery just wouldn’t hold a charge for very long.