Quote:
Originally Posted by Mark McM
I don't think most people would define the rider (or their legs) as part of the drivetrain. I think most people would see it as the "engine". So most would separately classify the energy paths through them. But putting aside the definitions of energy paths, in the end there appears to be no net loss of energy in frame flex - the strain energy transferred into the frame is not lost, but is returned in a useful way (through one mechanism or another). Tests and rider performances appear to bear this out.
However .. I think the mechanism of the energy return actually is important at least in one regard. As we've been discussing, the changing force vectors on the pedals through the crank revolution will not only affect how much strain energy goes into the frame, but also at what points in the crank rotation that it goes in and comes back out. This in turn affects the mechanisms by which the returned energy is utilized. The reason this is important is because riders often vary their pedaling styles to match different situations (for example, I don't think anyone will claim that they pedal the same way between standing or seated, or between steady continuous effort and short full-power sprints). I think it is highly likely that riders will vary there pedaling styles (if only subtly) in response to frame stiffness, and with practice will adapt their pedaling to optimize their pedal motions/forces with the frame response.
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I don't think a anyone who broke a driveshaft from too much torque on a muscle car would consider the motor separate from the drivetrain when looking for causes. If you are examining how power is distributed from leg muscles to road it is a bit arbitrary to say that flesh doesn't count.
As to adapting to how the energy goes in and comes out, that sounds like something your brain figures out in about 4 pedal strokes and is little different than the learning curve of walking with new shoes. Why would it be important?
It seems like the only important thing that these discussions really have to offer is convincing people that, despite how it might feel, you aren't actually throwing away energy if your frame flexes.