From: ssorensen@jplpds.jpl.nasa.gov (Sugi Sorensen)
Subject: Re: Time Trial Wheels
Organization: Jet Propulsion Laboratory
Date: Fri, 2 Oct 1992 05:03:09 GMT

In article <1992Oct2.015323.24058@elroy.jpl.nasa.gov>, goell@nomad.jpl.nasa.gov (Michael
Batchelder) writes:
> Each January the USCF does a series of aerodynamic tests of various
> commercially available aero products at the low-speed wind tunnel
> at Texas A&M University.  The great deal of the time is spent testing
> various aero wheels.  I have some hard copy graphs of drag vs. angle
> of attack for a bunch of different wheels.  GIVEN THEIR SET-UP, the
> CLEAR winner was HED. ...
> ...
> Some interesting results ensued.  Wheels which performed well without
> rotation, which included 3- and 4-spoke wheels (Specialized, Zipp,
> others), performed the worst under rotational conditions.  Also, many
> straight-walled cross-sectional disk wheels (Zipp, Mavic, others) did
> well off the bike, but under the most realistic conditions (rotating,
> on bike, with rider) their performance dropped quite a bit.  Relevant
> to your interest, the Specialized tri-spoke ended up having MORE drag
> than a normal 32 hole spoked wheel (MA40 rim).  This was the case for
> all the n-spoke wheels.
> 
> The clear winner was a Hed disk wheel, which had the least drag at
> ...
>  The next nearest competitor wheel was so far away that I don't
> even remember which it was...
The articles I have read do not support these claims. Please cite your
sources. If you have the hard copy graphs, why do you not remember the
"next nearest competitor wheel." Perhaps reading it off of your graph
would help?

Contrary to your claim that "the Specialized tri-spoke (and all other
n spoke wheels) ended up having MORE drag than a normal 32 hole spoked
wheel", the following articles showed otherwise when compared to various
other wheels:

(1) Zahrdanik, Fred and Drake, Geoff, "Fast Decisions...", BICYCLING,
Jan/Feb. 1992, pp.49-53.
(2) Kyle, Chester R., "Wind Tunnel Tests of Bicycle Wheels and Helmets,"
CYCLING SCIENCE, March 1990, pp.27-30.

In article (1), the Specialized tri-spoke wheel showed the greatest
calculated time savings for a 40-km TT compared to a HED CX, a Zipp 3000
tri-spoke composite, two bladed spoke wheels, and a conventional 32-hole
spoked wheel. The BICYCLING set-up was an outdoor test on a velodrome 
where a constant power output was maintained over a set distance.

In article (2), the Specialized tri-spoke recorded the lowest drag at
30mph compared to many other 27-inch wheels (including an Aerosport lens 
disk, a Campy lens disk, an unspecified tri-spoke, an Aerosport carbon 
flat disk, various bladed spoke, and regular round spoke wheels). The test
set-up was a wind tunnel at UC Irvine with the wheel in a jig rotated
by a variable-speed motor.Tests were done at an AOA of 0 degrees and 10
degrees.

Caveats: 
- I am only summarizing the results here. Example: at a 10 degree AOA in
  article (2), the Aerosports kevlar lens disk showed a lower drag than the
  specialized tri-spoke.
- Both of the above mentioned tests have been called into question by various
  folks. It should be noted that the test in (2) was commissioned and sponsored
  by Specialized.
- Many other wind-tunnel and outdoor tests have been performed and reported on
  in various publications. I have only referred to the above-mentioned articles
  because they are the only ones I had access to. The USCF reportedly has 
  performed several tests in the past few years at the wind tunnel at Texas A&M.
  Perhaps Les (or others who have the results) could summarize here for us.
- I have no commercial ties to Specialized or other companies, nor have I used
  their wheels (in fact I own the Batchelder-raved-about HED disk).

I cite the above articles because I question the conclusions of Mr. Batchelder.
It is rather strong language to assert, without hard data to back it up,
that the HED disk was the "CLEAR winner" and was "so far" ahead of its nearest 
competitor that it induced memory loss. I suggest that the original poster
read the data and draw his own conclusions.

Newsgroups: rec.bicycles.tech