#271
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And so we agree on the 7oclock.
You also said this: Quote:
Last edited by kramnnim; 02-21-2018 at 03:07 PM. |
#272
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That's from post #16. I've continued to develop that idea as we've gone along, and if you want I can recap some of what I've posted. |
#273
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You have NEVER explained where you think this energy is going and by what mechanism. |
#274
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By what mechanism? Where does it go and how is it isolated from the driveline that created it?
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#275
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Downward pressure from the rider flexes the frame rather than providing radial force to the crank arm to make the crank rotate. Frame flexes back when the now tangential force from the rider lessens and does not provide any rotation to the crank arm.
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#276
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If the frame flexes back after 6 o'clock, that means the pedal is being raised. If the pedal is being raised while it is already traveling upward, how is that not helping the rider pedal?
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#277
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The upward and lateral movement of the BB (including the entire crankset as well as the pedal) does not result in crank rotation.
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#278
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The pedal is on the end of the crank and it is rotating upwards between 6 and 12 o'clock. So if the end of the pedal is lifting as it swings up from the BB, and your foot is at 7 o'clock when that happens, it is most certainly helping move your foot in the direction of pedaling.
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#279
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Does the frame unflexing lift the entire BB and crankset, or just the pedal? When the frame unflexes, does the pedal rise a greater distance than the center of the BB? Does "moving in the direction of pedaling" result in rotational force to the crank arm? How far can you propel a bike without rotating the crank arms? Last edited by kramnnim; 02-22-2018 at 06:33 AM. |
#280
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The key question to the current point of contention appears to be: In the bigger picture, is there a difference between the stored flex energy driving the bike forward directly, and the stored flex energy making it easier for the rider to drive the bike forward? In the end, it comes down to the total energy the rider expends, and the total energy that propels the bike. All the evidence seem to indicate that the flex in the frame has little affect on either of them. Between the moment the frame begins to flex, and the moment the frame has un-flexed, the amount of energy expended by the rider, and the amount of energy that propels the bike, will be the same as if the frame hadn't flexed at all. |
#281
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As the frame unflexes, the pedal moves more than the BB if it is above or below the line that the BB is flexing around. So if the pedal is a 7 o'clock, it is moving more than the center of the BB. It's a lever. Yes, because it adds to the movement that is already happening. Depends what you mean. A 4 o'clock the GCN video shows how the bike would be moved. At 6 o'clock the question doesn't make a lot of sense - you don't pedal a bike by stepping straight down on a static pedal, and you can't use the motion of a static pedal if it isn't allowed to continue to rotate. It sounds like you are trying to "prove" that flex can't help pedaling, but the only way you can do that is to stop the pedaling. |
#282
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I would agree that in most modern carbon frames, there isn't enough flex to affect the amount of energy expended. If the frame is considerably flexier than that...many riders may notice the flex, and the bike may feel sluggish. I have yet to see proof that such flexy frames are not wasting energy. |
#283
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What I think you're calling "the energy that makes it easier for the rider" -- we've talked about it lifting the rider's foot on the pedal -- that energy comes from forces the rider puts on the frame which would never drive the bike forward, no matter how the frame behaves. The example is when the bike's on the trainer, the pedal is at 6 o'clock, and you press down and "sway" the BB to the side. You could do that on the road, instead of on the trainer, and bounce up and down and flex and unflex the frame all day, and never go anywhere. So on one hand there's effort, or force, that wouldn't ever move you forward, and frame flex that, when it returns its strain energy, ...won't move you forward. Then on the other hand there's force which, if it didn't get borrowed by flex, would move you up the road. And the flex that's a response to this force is best regarded as a different mode of flex from the first. We used the example of the chainstays' bowing sideways for this, and the thing that separates this flex from the first mode is that it reduces the effective distance between the rear cog and the chainring. Another way to say it is that this flex shortens the "free chain" between the crank and the rear wheel. I still have some doubt about that, and I have a scenario I want to sketch out to frame my question -- however I've run out of time just now. But, have I clarified what I mean there? Does it look reasonable to isolate those two modes of flex, even though I haven't yet said what it'll be useful for? |
#284
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#285
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