News Flash: Carbon fiber does not bend and propel, it breaks

Carbon fiber can be constructed to have different properties in different directions. In bikes they are both light and strong without being stiff/uncomfortable. The are stiff in the directions that they need to be while damping vibration for the rider.

The ground is doing the work bending the plate when you land; the runner benefits from the loaded spring being released as you take off.

zcxvzcxv wrote:

The ground is doing the work bending the plate when you land; the runner benefits from the loaded spring being released as you take off.

Exactly boys, it's this simple.

mnbvc wrote:

Fyzics is Phun wrote:

How is it possible for your grasp of physics to be so lacking?

Oh that's right you're 10 years old.

Isn't he the 'flat earther'?

No, I'm the guy that posted this analysis of running mechanics. You're the two jokers who posted jokes and nothing else. You've gotta have something of substance to be taken seriously.

Who can do it? Who can defend their faith in "energy return" against me without using this sophomoric snark? The truth doesn't care if your imaginary audience laughs at your jokes.

physics at work wrote:

zcxvzcxv wrote:

The ground is doing the work bending the plate when you land; the runner benefits from the loaded spring being released as you take off.

Exactly boys, it's this simple.

You need to study physics. The plate would not bend at all if not for the strong nuclear force exerted by the foot above it. Never oversimplify - be thorough.

If you're gonna model the overall physics of that, you'll have to consider biomechanics, and learn exactly when force is applied and how. Go ahead and try! We all know you won't do that, let alone register your "physics at work" handle and try to live up to it for the rest of your LRC life.

Hahaha OP said that carbon fibre cannot bend. Is this real?

The amount of people who go out of their way to support a fucking shoe is insane. Based on a couple of media reports that say that the carbon doens't help...

Regarding the spring - for anyone that has worn the VF - when you run - it feels like a spring to me.

Look at Bikes to see that you are wrong wrote:They are stiff in the directions that they need to be while damping vibration for the rider.

That's what she said.

sbeefyk2 wrote:

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.

I see you know nothing about carbon fiber fly rods.

Pole Vault poles use carbon.

Look at Bikes to see that you are wrong wrote:

Carbon fiber can be constructed to have different properties in different directions. In bikes they are both light and strong without being stiff/uncomfortable. The are stiff in the directions that they need to be while damping vibration for the rider.

That's mostly marketing hype. Bikes really can't be stiff one way and flexy another. The frame geometry cancels out that potential. They would have to be flat structures to really exhibit that trait.

Steely dan wrote:

Real men ride steel.... Or horses.... or steel horses.

I've got an older steel framed LeMond bicycle but I really like my newer carbon fiber road bike. It rocks and that's what real men ride!

sbeefyk2 wrote:

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.

It does neither. It distributes impact over the entire cushioning area rather than compressing at a more isolated point. And it does that every. single. step. That's why it's unstoppable.

This is a funny thread because not long ago I was trying to demonstrate for my wife the Vaporfly bounce into the air thing, like that one video by bending it on the floor and letting go. Well the plate straight up snapped and it didn't go anywhere haha. So from there, I snapped the plate in the other shoe and now they're great recovery/easy day shoes with more flex to them! She was not amused, since we share a bank account.

If you read the science papers around the VF, you'll know that the the "spring" is the foam. The CF plate is there to add stability to an otherwise soft and squishy foam which returns energy at a higher rate than other similar foams.

sbeefyk2 wrote:

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: Every see a modern road or mountain bicycle?

check-it-out.

Arch reduces energy cost of running by 17%. [1]

Achilles alone stores and releases 35% of the mechanical energy generated during running. [1]

MTP is unable to return any energy. [2]

Regular flat plates reduce energy cost at MTP but increase energy cost at talocrural. [3]

Extremely curved plates (vaporfly) manage to reduce energy cost at both MTP and talocrural. [3]

Vaporfly foam returns 45 times more energy than the plate. [4]

So the curved plate is there for stifness and moment arm without compromising talocrural energy cost - not for "spring". Everyone seems to know what a spring is (I do, it stores and releases energy!); not everyone knows materials, biomechanics, anatomy (I don't). So it's natural that everything is dumbed down to "IT'S A SPRING!". No. If there is a spring, it's the foam (not the plate).

Sources:

[1] Lieberman, D. (2013). The Story Of The Human Body: Evolution, Health & Disease. pp. 85

[2] Stefanyshyn, D. and Nigg, B. (1997). Mechanical energy contribution of the metatarsophalangeal joint to running and sprinting. Journal of Biomechanics 30: 1081-85. doi:10.1016/S0021-9290(97)00081-X

[3] Farina, E., Haight D. and Luo G. (2019). Creating footwear for performance running. Footwear Science 11: 134-35. doi:10.1080/19424280.2019.1606119

[4] Hoogkamer, W., Kipp S. and Kram R. (2018). The Biomechanics of Competitive Male Runners in Three Marathon Racing Shoes: A Randomized Crossover Study. Sports Medicine 49: 133-43. doi:10.1007/s40279-018-1024-z

check-it-out.

TL;DR: Yes, the plate doesn't act as a spring!

It does bend though. And it also does break if you run over it with an Escalade (can't provide sources).

Even if the plate doesn't contribute directly you are increasing your leg length with the stack height, that alone will make you more efficient as you'll take a lower amount of steps to cover the same ground. The stack height on a vaporfly vs a Asics hyperspeed is a huge difference at around the same weight.

you're not even a has been: you're a never was wrote:

https://video.twimg.com/ext_tw_video/1007958930595565568/pu/vid/360x640/6Ohbn53rmY-O0p0Y.mp4

I wonder if the next %s or alpha flys have even greater pop?