Originally Posted by
rpenmanparker
We talk about spring constant of the BB as a simple conversational tool like a problem being worked through on the blackboard in freshman physics class. In truth the energy absorbing deformations of the bicycle frame AND components due to pedaling are so complex that no measurement of even one of them is likely to be possible, much less measurement of the composite constant.
Since your original question was about the contention
that an appropriately stiffer frame (e.g. at the BB) facilitates power transfer the spring constant is going to be the dominant mechanism. Components etc are not relevant. The italics are a quote from your OP.
Originally Posted by
rpenmanparker
You have taken no notice of the peculiarities of pedaling style either. Surely there are very conservative and very lossy pedaling styles. But in your discussion, it is pure and simple: no energy lost.
Also not relevant to difference between frames (your OP).
Originally Posted by
rpenmanparker
Furthermore, you are using your hypothesis as part of the proof when you insist that energy returned to the frame by the reversal of the BB (or other deformed part) will go into the drive train. I don't think anyone argues that some fraction of it won't be returned somehow, but no one has established how much will be lost in the deformed part (hysteresis), how much of the energy will be returned to the drivetrain at all, and perhaps most important how much will be returned in a way to produce forward motion. We don't just care about returned energy, we care about energy that can be translated to forward bicycle motion.
My contention is that the spring energy is indeed returned as forward motion. There is no significant hysteresis in metal frames at the frequencies of interest, I doubt that even with lossier materials like CF composites that there is enough to matter but I haven't tested that.
Originally Posted by
rpenmanparker
Your contention about zero energy loss isn't fact. First if it were true it would be the first known case of a perpetual motion machine. It is well known that there is no such thing as zero energy loss in any real world spring. Is the loss in this case significant? Don't know, and neither do you.
Ignoring your rhetorical flourishes, you misrepresent me. I have consistently said the loss is near enough to zero not to matter. I made one error where I did not include the "near enough" bit, that was wrong and I have since corrected it. To be clear; I am not claiming zero loss, I am claiming there is not enough loss for the differences between frames to matter.
Originally Posted by
rpenmanparker
Just as importantly your opinion doesn't answer my question. That disconnect has been the main reason for your posts being ridiculed over several pages. You continue to insist that because you say it, it is true. Hardly. Paraphrasing Jerry McGuire, show me the data. Oh wait a minute, that is what I asked 15 pages ago.
We're back to point one. Yes it's a reductionist argument, but your OP implies, and the majority of the marketing of the major bike brands explicitly states, that a less stiff frame absorbs significant energy making the bike less efficient.
If this was not what you meant, I have indeed been tilting at a straw man but I don't think it was an unreasonable take home from your question.
IMO the flak I have copped has been largely because I haven't been willing to reveal my methods; that's a fair enough criticism. The ridicule heaped by you and others speaks volumes about you and little about me.