Ayesha wrote:An engine can be tuned to give most torque at the low end, a ‘stump puller’, or at the high end, a ‘howler’.
A ‘Power curve’ is produced.
A cyclist can apply equal torque all the way up the rev range until it is physically impossible to move the legs fast enough. A straight inclined ‘Power curve’ is produced until it tails off at high speed.
Not true. Everyday cycling experience, supported by measurements reported in Bicycling Science, demonstrates that the human engine is likewise capable of high torque at low rpm and less torque at high rpm, and that the product of this varying torque and rpm produces a power curve.
The human engine is, in fact, like a motor with a camshaft profile and timing that can be altered on the fly, by deciding to apply more effort or adopting a different action, e.g. by sliding forward on the saddle or (a radically different 'camshaft') by standing and dancing on the pedals! Each effort level yields a different curve (according to Fig. 2.11 p49 of the 2nd Edition), with a maximum efficiency that is not only lower for long duration riding than that which may be sustained for a short time only but also peaks at a lower rpm. This chimes with experience. The same person will usually pedal faster when trying hard, than when cruising (and not because he's run out of gears) and an athlete will use a higher gear AND a higher cadence for a short time trial, compared to a long one.
But the curves in Fig. 2.11 are quite flat. For a given level of effort (measured by oxygen consumption, which is a proxy for fuel consumption and hence yeilds an efficiency value), a variation of cadence as much as 20% different from the optimum results in only a few percentage points loss of efficiency.
With gaps between gears of 14% (like a Rohloff hub or a wide-range MTB cassette) the most anyone will have to vary their cadence from the optimum (without also altering their breathing rate) is 7%. Looking at the curves in Fig. 2.11, it is hard to conceive of even a 1% reduction in efficiency from altering ones cadence by such a small amount, half a percent maybe. And one can always breathe a little quicker or slower to make that new cadence optimum. So I don't think we need finer tuning.
Racers maybe. If they're already breathing at the limit they have nowhere left to go and half a percent could be winning or losing.
One thing that will please Ayesha, is that the optimum cadences in Fig. 2.11 are much closer to his big gear churning than my twiddling! He must have a good old British motorcycle engine, whereas mine's a Yamaha!
Much of the data behind Fig. 2.11 however, came from Japan!
