As always I cannot resist these technical discussions. Please forgive me...
Richard Wizins wrote:
Maybe you are right Frederik, maybe not. I am personally not convinced that we can pedal very much more efficiently than most skilled cyclists already do.
This seems plausible. There is so much money in pro cycling that it would be unlikely that the pro teams haven't already done what's within the reach of scientific investigation to promote the highest possible efficiency.
This, of couse, dosen't exclude new scientific discoveries...
B. We have the issue of aerobic limitations. I.e. the cardiovascular system can not support an increase in power over any lenght of time even if we have the muscles to do it.
This I agree is the limiting factor for power output for most cycling activities.
energy. One could argue that it "only" prevents us from actually resting on the pedals on the upstroke and thereby counteracting the push on the other pedal. There is no telling how much power we actually add - it could well be nil.
Yes. The idea of Powercranks is to avoid spending some energy counteracting youself, i.e. pushing 'backwards' with one leg and 'forwards' with the other. Some energy would undeniably be saved if this can be avoided. It might be very little, though, maybe too little to bother. And maybe the action of actively lifting one leg instead of just letting it be lifted causes involvement of additional muscles, resulting in a nil gain or a loss. The human body is mechanically quite complicated (sic) and activating one muscle here generally requires another muscle there to be counteracting, to avoid the having body severely twisted...
Bikedrive on the other hand does address the problem of erratic power. If we accept that we have an spike of force on the down stroke (or up stroke by the way) which is in part lost on trying to overcome the bike's (and rider's) moment of inertia (weight basically, in this case) we have an interesting opportunity here. By storing part of the access force (energy actually) in the spring instead of "burning" it on a fruitless attempt to jump the bike forward we can use that energy during the otherwise virtually powerless 12-6 o'clock part of the cycle. Thereby we would add no new energy, but we would waste less of what we have on fruitless short accelerations (F=m*a).
Well, storing energy as spring tension or as momentum would make no difference, would it? Only the momentum storage is more light-weight, and has no termal losses...
BTW, the energy provided by each pedal stroke is small compared to the moving energy of the bike with rider, I think. I the energy of the moving bike was plotted, the pulsing caused by pedalling would be a tiny riddle on top of a comparatively steady line.
- My first impression of the Powercranks was a bit flawed. Their main
principle is preventing "resting" (pushing if you like) on the pedal in the up-stroke. Learning to use muscles to lift the foot will increase effective power (theoretically). If the power contribution in the up-stroke remains small (but not negative) it will do nothing to smooth the power curve. This might work, but I'm sceptical.
I am, too. But read the last lines below: