Just so we're all on the same page, carbon fiber cannot be a spring. It does not bend and propel forward. If carbon fiber bends, it will shatter. Especially very thin sheets such as those in a shoe. In a shoe it just gives support and stability to avoid losing energy that would be lost from a less structurally sound shoe.
News Flash: Carbon fiber does not bend and propel, it breaks
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the point is to increase efficiency of the ankle movement. for the nikes it adds stability because the foam is so soft otherwise, but in other carbon fibre shoes without the pebax foam it still functions well.
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sbeefyk2 wrote:
... carbon fiber cannot be a spring. ... If carbon fiber bends, it will shatter. Especially very thin sheets such as those in a shoe...
Why do you state this with such certainty?
You are wrong. Carbon fiber parts can definitely undergo elastic deformation. -
Hmmmm, ever heard about carbon fiber layers in snowboards or skis?
The only pupose of these is to provide a snappier rebound than fiber glass when the board is flexed. -
... and why would a carbon fiber fork on a road bike be superior at damping vibration if it was completely rigid (aka couldn't bend)?
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[img]https://en.wikipedia.org/wiki/Mechanics_of_Oscar_Pistorius%27s_running_blades#/media/File:Oscar_Pistorius_2_Daegu_2011.jpg[/img]
Just so we're on the same page, carbon fiber is the material of construction for prosthetic running legs... definitely acting as a spring there... -
Fart Garfunkel wrote:
sbeefyk2 wrote:
... carbon fiber cannot be a spring. ... If carbon fiber bends, it will shatter. Especially very thin sheets such as those in a shoe...
Why do you state this with such certainty?
You are wrong. Carbon fiber parts can definitely undergo elastic deformation.
What? It cannot bend, period. Get a life Garfartel. -
Do you know what "bend" means?
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moot issue one way or the other. Springs won't make you run faster. Any "energy return" is merely pushing up on a heel that is already moving up on its own via the ordinary mechanics of running.
Try this, folks: while running, keep your heel on the ground all the way through takeoff. You can't. As your body moves forward, it pulls the heel forward and thus upward around the toe which is the last contact point with the ground. All forward acceleration is done by the body pushing itself forward from that toe.
If, somehow, "energy return" were able to add acceleration to this, it wouldn't be free - it would exert extra force on the body, and the body would have to exert extra equal and opposite force to counteract it. Any extra speed would still require the same extra effort it ordinarily would.
Think what happens when an elevator first starts ascending - it seems like gravity momentarily gets stronger. If you jump right then, you won't go any higher relative to the ground than when the elevator was at rest. Once it's moving, you might jump higher, but you still had to spend the extra energy counteracting the initial acceleration. -
Fart Garfunkel wrote:
Do you know what "bend" means?
Yeah I do knucklehead, it don't bend. I had a pair and returned them and I run 3:59 for 26.2, so I'm a fast fVcker:):):):) -
Bad Wigins wrote:
moot issue one way or the other. Springs won't make you run faster. Any "energy return" is merely pushing up on a heel that is already moving up on its own via the ordinary mechanics of running.
Try this, folks: while running, keep your heel on the ground all the way through takeoff. You can't. As your body moves forward, it pulls the heel forward and thus upward around the toe which is the last contact point with the ground. All forward acceleration is done by the body pushing itself forward from that toe.
If, somehow, "energy return" were able to add acceleration to this, it wouldn't be free - it would exert extra force on the body, and the body would have to exert extra equal and opposite force to counteract it. Any extra speed would still require the same extra effort it ordinarily would.
Think what happens when an elevator first starts ascending - it seems like gravity momentarily gets stronger. If you jump right then, you won't go any higher relative to the ground than when the elevator was at rest. Once it's moving, you might jump higher, but you still had to spend the extra energy counteracting the initial acceleration.
I'm not a big believer of any of this shoe hype, and I don't care at all who wears what shoe, but a shoe can be designed to perform differently by modifying foam properties or incorporating other structural elements. I don't believe that "energy return" has a major contribution to running, but theoretically it could.
The primary goal of the shoe is to provide cushion damping shock from impact forces. To provide the cushioning, the shoe must deform and absorb the force of your weight landing.
"Energy return" is then any return force that comes from the elastic return of the shoe. This exists to some extent with every shoe. I think of it as any reduction of you sinking down into the foam of the shoe. It doesn't propel you at all, but over greater distances it can reduce fatigue.
If you don't believe in energy return at all, then why don't you just buy the mushiest shoes you can find? -
Fart Garfunkel wrote:
Bad Wigins wrote:
moot issue one way or the other. Springs won't make you run faster. Any "energy return" is merely pushing up on a heel that is already moving up on its own via the ordinary mechanics of running.
Try this, folks: while running, keep your heel on the ground all the way through takeoff. You can't. As your body moves forward, it pulls the heel forward and thus upward around the toe which is the last contact point with the ground. All forward acceleration is done by the body pushing itself forward from that toe.
If, somehow, "energy return" were able to add acceleration to this, it wouldn't be free - it would exert extra force on the body, and the body would have to exert extra equal and opposite force to counteract it. Any extra speed would still require the same extra effort it ordinarily would.
Think what happens when an elevator first starts ascending - it seems like gravity momentarily gets stronger. If you jump right then, you won't go any higher relative to the ground than when the elevator was at rest. Once it's moving, you might jump higher, but you still had to spend the extra energy counteracting the initial acceleration.
I'm not a big believer of any of this shoe hype, and I don't care at all who wears what shoe, but a shoe can be designed to perform differently by modifying foam properties or incorporating other structural elements. I don't believe that "energy return" has a major contribution to running, but theoretically it could.
The primary goal of the shoe is to provide cushion damping shock from impact forces. To provide the cushioning, the shoe must deform and absorb the force of your weight landing.
"Energy return" is then any return force that comes from the elastic return of the shoe. This exists to some extent with every shoe. I think of it as any reduction of you sinking down into the foam of the shoe. It doesn't propel you at all, but over greater distances it can reduce fatigue.
If you don't believe in energy return at all, then why don't you just buy the mushiest shoes you can find?
I told you from my first post, it don't bend fartman, cut your intellectual loses and move on. -
op's thread is an epic fail
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Carbon energy return; you load the spring ( golf shaft) , change direction to release the energy .
https://i.ytimg.com/vi/WpUzr1ARKqo/hqdefault.jpg -
OP goes home DEVASTATED.
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I’m loving all the wannabe materials scientists trying to get in on the Vaporfly discussion haha
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Fart Garfunkel wrote:
I don't believe that "energy return" has a major contribution to running, but theoretically it could.
The primary goal of the shoe is to provide cushion damping shock from impact forces. To provide the cushioning, the shoe must deform and absorb the force of your weight landing.
"Energy return" is then any return force that comes from the elastic return of the shoe. This exists to some extent with every shoe. I think of it as any reduction of you sinking down into the foam of the shoe. It doesn't propel you at all, but over greater distances it can reduce fatigue.
If you don't believe in energy return at all, then why don't you just buy the mushiest shoes you can find?
The human body is already able to absorb the force of landing on its own. That's why the arch pronates and supinates and the elastic tendons stretch and rebound.
Adding to that by putting a spring under them is like attaching a rubber band to another one. You don't get a stronger rubber band, merely one that goes farther. The shoe creates a false elastic surface under the heel, increasing its vertical displacement and prolonging footstrike. As this new surface isn't perfectly efficient (drop a ball on a trampoline and see if it bounces forever!) it actually results in less energy return overall.
The greater displacement could accelerate the heel upward to a higher speed off the ground, but that doesn't matter and could even be detrimental. The heel lifts naturally on its own, as I already mentioned, and the muscles don't start applying a lot of force until it's high enough to raise the arch via the windlass mechanism. Before then, the arch is too flexible to efficiently transfer force from the leg to the ground. -
lololol wrote:
op's thread is an epic fail
But he posts here all the time, how could he be wrong?
