David_Stone said:*Thanks for the ideas about platforms, D3. I'm not sure what Q is.*
Well essentially, it is the distance between pedals. Sheldon Brown
calls it "tread" or "Q-factor", and makes it the distance between pedal
attachment points, which is close enough. Distance between pedals on a
unicycle is determined by axle length and crank design. Some cranks
flare outwards more, increasing their contribution to a given wheel's Q.
Widening a unicycle hub with welded-on flanges not only separates the
flanges more, but also separates the pedals more.
On the stock Coker, my feet always wanted to drift outwards, even when
using super grippy pedals to try to "lock" my feet in place. This left
me fighting the unicycle and was quite unsettling. When I switched to
the wide hub, I was noticeably happier on both grippy and non-grippy
pedals. Similarly, on my Suzue-based 29er, I had to add pedal
extensions to be comfortable. Recent experiments I've done with a KH
hub-based 29er show me that the pedal spacing for me is pretty good
without adding the extensions, since the hub/axle are wider and the
cranks have more contribution to Q than the Bike Euros on the other
29er.
Since pedal spacing is a factor in bicycle fit, it is reasonable to
conclude it is also a factor in unicycle fit, with the above experiences
serving as instances of a general principle. However, a bit of thought
about the nature of unicycling and fit shows one that individual body
characteristics, seat height, seat type, crank length, riding type, and
even terrain type are all complicating factors, so that calculating the
ideal Q for a person is a non-trivial task. It is currently not
possible to calculate accurately a person's ideal unicycle Q from body
measurements and the like.
However, road riding is the unicycling style that is the most controlled
in terms of seat height and body motion, so it may be the one to start
with by simple individual experimentation, as I have done.
In general, we currently have control over: seat type, hub width (more
precisely, axle length), crank brand, pedal width. These things are
worth playing with for a serious rider in order to achieve optimal Q.
Note that some hubs have proprietary axle/crank interfaces so that using
a different brand of cranks is not possible. Note also that, for some
or most cranks, choosing a longer crank also increases that crank's
contribution to Q.
Optimal Q is desirable for: relaxing while maintaining proper foot
position on the pedals, even on rough terrain; minimizing side pressure
on the saddle; minimizing muscle and tendon interference by the saddle;
developing optimal energy transfer through the legs to the pedals;
developing higher spinning rates with longer cranks; and the like.
Although some riders dismiss Q as an issue, I believe, partly based on
my own personal experience, partly from simple thought experiments, and
partly from the bicycling literature, that Q is quite important for the
serious unicyclist. As distance riding (both road and off-road, touring
or racing) develops, Q-factor will become a major factor in fitting a
unicycle to a rider for optimal performance over many miles. I have
started developing a unicycle-specific system for quantifying this, and
hope to fold it into 'the unicycles I build'
(http://www.livewireunicycles.com).
--
U-Turn - As long as my feet keep movin'...
Weep in the dojo... laugh on the battlefield.
'LiveWire Unicycles' (http://www.livewireunicycles.com)
'Strongest Coker Wheel in the World'
(http://www.unicyclist.com/gallery/albup39)
'29er Tire Study' (http://u-turn.unicyclist.com/29erTireStudy/)
'New York Unicycle Club' (http://www.newyorkunicycle.com)
-- Dave Stockton
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