Archive-URL: http://search.bikelist.org/getmsg.asp?Filename=tandem.10306.0230.eml
Date: Wed, 11 Jun 2003 07:41:29 -0700 (PDT)
From: "Precision Tandems" <Mark(AT)PrecisionTandems.com>
Subject: [T(AT)H] Shimano 16 spoke wheels

Hi All,

I just completed a home-grown experiment this past weekend to reveal to
myself how much difference wheels having 16, 40 or 48 spokes would make.

My initial evaluation was to wind it up by hand in a 55x11 while in the
workstand and subjectively noted more wind or fan like air motion from a 40
spoke wheel as compared to that of the 16.  From this one could intuitively
surmise that the 16 spoke wheel is more efficient.  Another point of
interest was how quickly the 16 spoke wheel would accelerate during hand
cranking compared to the heavier 40 spoke set.  BTW, the weight savings of a
Shimano tandem hub/FiR rim with 40 spokes as compared to the Shimano 16
paired spoke wheels is 2702g - 2207 = 495g.

Searching for a constant power source, a Makita battery operated drill was
used with a bolt in the chuck which served well to turn the entire
drivetrain via the crankarm bolt.  The timing chain was removed to minimize
the motion caused with the cranks in phase.  Hmmm....  maybe it is
impossible to pedal smoothly with cranks in phase after seeing the effect of
alternating crank motion when powered by a non ocillating power source!
...but that is another topic.

A computer was hooked up to the rear wheel to monitior the maximim speed in
the chosen 55x21 gear combination.  And after several trials, it was
determined that the drill battery needed to be charged for 3 minutes between
each test in order to maintain reproducability.

Multiple trials were run for each wheel to insure consistency.

The maximum speeds recorded for the 16 spoke wheel were 69.5 mph.
The maximum speeds recorded for the 40 spoke wheel were 63.5 mph.
The maximum speeds recorded for the 48 spoke wheel were 61 mph.

After the data was recorded, the 16 spoke wheel results were again
duplicated and verified just on the chance that our 3 minute charge time
combined with the multiple runs did not cause an accumulated change in the
battery conditon.  The 16 spoke wheel was again clocked at 69.5mph, the same
as the intial test.

Any math folks on the list are welcome to jump in here and enlighten us as
to the speed increase or the increase in efficiency one can expect from
running 16 spoke wheels at speeds one would expect on "real" rides, i.e.,
15-20 mph, 20-25 mph, as compared to that of 40 or 48 spokes.

On wheel/ride compliance... nah... won't go there just yet! ;-)   .....not
until I develop a stokajoltameter that WILL quantify some things.  Not all
things are imagined.

Mark Johnson
Precision Tandems
Shawnee, KS
913.962.8866
http://www.precisiontandems.com
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