New powermeter rumours

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RadB
Posts: 229
Joined: Mon Mar 02, 2020 3:24 am

by RadB

Does everybody require +/-0.5% accurate PMs, are you suggesting they do?

Adequate accuracy is indeed a thing, it's the same concept as control when riding and racing; it only needs to be adequate to get the job done, or performed in such a manner that is fit for purpose to the application at hand.

jever98
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Location: Seattle

by jever98

I still don't get it: what is the real use case for dual sided measurement? Spiders get all the power and can approximate balance. I am yet to see training that incorporates balance beyond identifying gross imbalances (which you can also do with a spider based power meter).

RE infocrank: again, not a great way to measure power: no auto zeroing, and if anything happens to the crank arm (which is way more likely than to the spider), it's damaged or broken.

The biggest argument I see for pedals is to be able to travel with them minus the bike.
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TobinHatesYou
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Joined: Mon Jul 24, 2017 12:02 pm

by TobinHatesYou

RadB wrote:
Wed Dec 07, 2022 12:36 am
Does everybody require +/-0.5% accurate PMs, are you suggesting they do?

Adequate accuracy is indeed a thing, it's the same concept as control when riding and racing; it only needs to be adequate to get the job done, or performed in such a manner that is fit for purpose to the application at hand.

My L/R balance changes with intensity, fatigue, cramping, gradient, etc. My L/R balance indoors is 50/50. My L/R balance outdoors is often 52/48, sometimes 53/47.

jever98 wrote:
Wed Dec 07, 2022 12:37 am
I still don't get it: what is the real use case for dual sided measurement? Spiders get all the power and can approximate balance. I am yet to see training that incorporates balance beyond identifying gross imbalances (which you can also do with a spider based power meter).

RE infocrank: again, not a great way to measure power: no auto zeroing, and if anything happens to the crank arm (which is way more likely than to the spider), it's damaged or broken.

The biggest argument I see for pedals is to be able to travel with them minus the bike.

Spiders are great and are/can be accurate. However spiders don't measure power off of approximate L/R balance. They estimate L/R balance based off of changes in AV.

tomato
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Joined: Mon Jul 01, 2019 8:37 pm

by tomato

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Last edited by tomato on Wed Dec 07, 2022 3:39 am, edited 1 time in total.

tomato
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Joined: Mon Jul 01, 2019 8:37 pm

by tomato

TobinHatesYou wrote:
Tue Dec 06, 2022 11:57 am
Something is either accurate or it isn't.
The accuracy of an instrument is a specification; it's not a yes/no property.

jever98
Posts: 1175
Joined: Wed Feb 18, 2009 12:02 pm
Location: Seattle

by jever98

TobinHatesYou wrote:
Wed Dec 07, 2022 1:23 am

Spiders are great and are/can be accurate. However spiders don't measure power off of approximate L/R balance. They estimate L/R balance based off of changes in AV.
Not quite, for p2m at least. The pm takes 60 torque readings per second and compares the power integral of the two halves of each crank rotation.
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TobinHatesYou
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by TobinHatesYou

tomato wrote:
Wed Dec 07, 2022 3:38 am
TobinHatesYou wrote:
Tue Dec 06, 2022 11:57 am
Something is either accurate or it isn't.
The accuracy of an instrument is a specification; it's not a yes/no property.
What I stated does not exclude what you stated. It is not possible for a left-only power meter to be accurate within *any* specified limits unless the operator is only pedaling with a single leg. There is claimed accuracy relative to its own calibration…as in the reported values will never be >1% deviation, and then there’s real-world accuracy as in how good is this device at measuring the amount of power going into turning crankarms / propelling a bicycle.
Last edited by TobinHatesYou on Wed Dec 07, 2022 9:31 am, edited 3 times in total.

TobinHatesYou
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by TobinHatesYou

jever98 wrote:
Wed Dec 07, 2022 5:08 am
TobinHatesYou wrote:
Wed Dec 07, 2022 1:23 am

Spiders are great and are/can be accurate. However spiders don't measure power off of approximate L/R balance. They estimate L/R balance based off of changes in AV.
Not quite, for p2m at least. The pm takes 60 torque readings per second and compares the power integral of the two halves of each crank rotation.

And if you lift at all with your “back” leg then those L/R values aren’t accurate.

Hexsense
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Location: USA

by Hexsense

Part of my power delivery (~25%) come from top foot push forward and bottom foot pull backward. It doesn't matter how high sampling rate you have. With only one sensor, you can't distinguish left vs right contribution when force are applied from 2 legs simultaneously at the top and bottom.

TobinHatesYou
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by TobinHatesYou

Hexsense wrote:
Wed Dec 07, 2022 8:55 am
Part of my power delivery (~25%) come from top foot push forward and bottom foot pull backward. It doesn't matter how high sampling rate you have. With only one sensor, you can't distinguish left vs right contribution when force are applied from 2 legs simultaneously at the top and bottom.

Yeah, on flat ground at threshold my power phase starts around the 12 o'clock position and ends at 7:30. At higher intensities and on steeper grades, the power phases elongate. At sprint intensities, the power phases length can be fairly random. Even in the 20min example below my right leg is obviously pulling through the bottom more than the left leg. If the P2M works as stated, that extra right legged power would be attributed to the left leg. And note the swap in L/R bias at different intensities.
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BigBoyND
Posts: 1350
Joined: Mon May 31, 2021 1:51 am
Location: Berlin, DE

by BigBoyND

Hexsense wrote:
Wed Dec 07, 2022 8:55 am
Part of my power delivery (~25%) come from top foot push forward and bottom foot pull backward. It doesn't matter how high sampling rate you have. With only one sensor, you can't distinguish left vs right contribution when force are applied from 2 legs simultaneously at the top and bottom.
As long as the top push and bottom pull are the same with both feet, accuracy won't be affected. It's only a problem of you push/pull with one leg differently than the other (which you surely do, but likely it's close enough for most people)

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Conza
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by Conza

Whats the deal with favero assimo's - a new version anytime soon?
It's all about the adventure :o .

toxin
Posts: 496
Joined: Tue Apr 18, 2023 5:56 pm

by toxin

Conza wrote:
Tue Jul 25, 2023 2:45 pm
Whats the deal with favero assimo's - a new version anytime soon?
They've been hinting on social media for over a year, but there jack shit as concrete info goes

Coolcat
Posts: 70
Joined: Tue Apr 06, 2021 7:21 pm

by Coolcat

Re dual vs single sided PMs: A spider PM cannot measure true power from each leg. The propulsive force is a sum of positive ("downstroke") and negative ("upstroke").

Power=(tangential force leg 1 + tangential force leg 2)*angular velocity

Pedals like Assioma measure force and angular velocity from both pedals every 20 ms or something, so they can distinguish the power contribution.

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Conza
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by Conza

toxin wrote:
Tue Jul 25, 2023 2:54 pm
Conza wrote:
Tue Jul 25, 2023 2:45 pm
Whats the deal with favero assimo's - a new version anytime soon?
They've been hinting on social media for over a year, but there jack shit as concrete info goes
Oh really!? Have just had a look, not been able to find anything in particular :shock:
It's all about the adventure :o .

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