Small lange vs. large flange hubs

On Tue, 09 Aug 2005 18:41:37 GMT, Bob
wrote:

OK... fill me on philosophy on this. Back in the good old days, we
all rode large flange. The theory I always heard was that large
flange had shorter spokes and therefore resulted in a stiffer wheel.
Supposedly that was a good thing. Now though we have small flange
and low spoke counts - which would result in a comparatively
flexible wheel, I would think.

Comments? How come no one wants high flange anymore ?

Bob

Dear Bob,

"Common large-flange hubs spoked tangentially are about
twice as stiff torsionally as common low-flange hubs. Such
low flange hubs require about twenty meter-kilograms (mkg)
per degree of hub wind-up. This means that the average
rider, using a two-to-one chain ration and 170 mm cranks,
would have ot press on the pedals with 250kg to wind-up a
small-flange hube one degree, or about 520kg (more than half
a ton) for a large-flange hub."

"It is evident from this comparison that small-flange hubs
prodve adequate torsional strength and stiffness. There is
no need to use large-flange hubs for greater torsional
stiffness, but their reduction of torque-induced spoke loads
might improve fatigue life slightly. However, with larger
flanges the spoke angle at the rim becomes less
perpendicular causing spokes to bend at the nipple. This
bend increases failures at the threads and probably cancels
any gains from reduced torque loads. To avoid this problem,
large-flange hubs are often spoked in a less than fully
tangential pattern."

"The Bicycle Wheel", 2nd edition, Jobst Brandt, p.64-5

" . . . using large flange hubs provides no functional
advantage and has the disadvantage of adding weight."

"Tandem bicycles are an exception. With 36 spokes or less,
tandem wheels require large-flange hubs to withstand the
torque of two riders. And to support the additional weight,
durable tandem wheels require at least 48 spokes, which can
only be accomodated by larger flanges."

--p.64

Carl Fogel