Deflection = power loss (true or false)?

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youngs_modulus
Posts: 664
Joined: Wed Sep 20, 2006 1:03 am
Location: Portland, OR USA

by youngs_modulus

ghisallo2003 wrote:
Sun Jun 27, 2021 8:12 pm
My favourite commentary on the question: https://www.renehersecycles.com/what-is-planing/
Why do you like Heine's commentary? I like it too, but perhaps for different reasons. That post happens to be my favorite example of cargo-cult science.
ghisallo2003 wrote:
Sun Jun 27, 2021 8:12 pm
I think deflection and release can be positive or negative depending on cadence, power dynamics, riding style, gradient, and that there is a sweet spot. Too much flex and energy is returned out of cycle, too little and the pedal dynamics become super-critical.
You're not wrong, but no one is actually right on this yet, AFAIK. In other words, this is a really complex question that hasn't yet been answered, at least to the best of my knowledge.

We don't know who's right, but we do know that Heine isn't. His ideas about "planing" are on par with the idea that disease is spread by "miasma."

JoO
Posts: 419
Joined: Thu May 04, 2017 7:30 am

by JoO

I think it is time for an experiment.

use a flexy bike with a pm ride up hill out of the saddle.

Do the same with the stiff bike.

Keep wheels, tires, PM constant.

Adjust the weigh by adding sand in a bidon.

Compare the results.

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AJS914
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Joined: Tue Jan 28, 2014 6:52 pm

by AJS914

They pretty much did that experiment in the link above. The question is how to tune the flex for the rider.

ghisallo2003
Posts: 730
Joined: Mon Jan 02, 2006 7:10 pm

by ghisallo2003

I like the Heine commentary because it captures the idea of a sweet spot well, making the same observation as Tobin but in, as you say, a pseudo-scientific way, which captures the feeling: of course the bike is not planing (and I do not believe he thinks it is). What it is though is giving the sensation (as you have when you foil) of increased forward drive for the same energy.

Great frames in the sweet spot have this feeling.

TobinHatesYou
Posts: 10930
Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

I made no observations…I doubt I could tell the difference between two BBs that had lateral deflection of 50n/mm and 70n/mm.

cunn1n9
Posts: 216
Joined: Sat Jan 15, 2011 1:24 am

by cunn1n9

JoO wrote:I think it is time for an experiment.

use a flexy bike with a pm ride up hill out of the saddle.

Do the same with the stiff bike.

Keep wheels, tires, PM constant.

Adjust the weigh by adding sand in a bidon.

Compare the results.
Good idea.

I predict the answer is there is exactly 0 difference in the climb times and if there is it is so small as to be irrelevant.


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Valy
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Joined: Tue May 29, 2012 11:16 pm

by Valy

duplicate

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