Jan Heine's recent article about frame flexibility and it's contribution to making him feel and perhaps be more efficient was interesting and got me thinking; how does that play for a touring frame with a low cadence, lower power output touring rider?
I can imagine how the right frame force/flex profile, cadence and effort could converge on a frequency or rate of deflection that would assist propulsion. Right or wrong it intuitively makes sense to me. It seems like that could be a significant bonus for randoneurs, racers and sporting riders who exert highish pedal forces and have brisk cadences. But I wonder; would a tourist benefit from the same sort of attributes and behavior, and would the flexibility work to significant detriment in other areas like stability in load carrying? It seems to me that many tourists cadence, pedaling forces/frame deflection and power output are significantly lower than sporting riders. Mine sure is. I don't crawl but I don't maintain momentum and hammer over rollers either when touring. It doesn't feel like I'd hit any beneficial harmonic or deflection recoil rate while touring. For the most part I don't ride quickly unless there is sympathetic hill or wind, or a good meal that may be missed. My cadence is slowish and pedal forces light for the most part; not too much frame deflection from them and any frame flex restoration would seem much quicker than, and out of phase with, my cadence. Like bait casting; you have to snap the rod quickly and deflect it enough for it's flexibility to do any good. Too fast doesn't work well and too slow works less. It doesn't feel like I fit that analogy under touring conditions and I wonder if that's typical of touring cyclists in general. At the same time I think a more flexible bike would be more prone to experience harmonic vibrations of problematic magnitude and frequency if moving quickly, particularly with an extra 50# of gear. Certainly the need to damp vibration of some conventionally tubed frames under certain circumstances by pressing a knee against the TT seems undesirable, viewed in a vacuum. Larger diameter tubesets are torsionally and latterally stiffer and have increasingly higher frequency harmonics which would be less likely to be excited under riding conditions. So, if my hunch is right and frame flexibility doesn't help propulsion much, or perhaps at all, at low cadence and effort then perhaps the design goals and details of touring vs. randonneur frames are subtly different. Does anyone know if the touring bikes or builders of the last half of the 1900s tell us anything on this count? Just what was different between randonneur and touring tubesets and major design elements? Any thoughts?
Regards John Clay Tallahassee, FL
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