New powermeter rumours
Moderator: robbosmans
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.
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.
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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.
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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RadB wrote: ↑Wed Dec 07, 2022 12:36 amDoes 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 amI 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.
The accuracy of an instrument is a specification; it's not a yes/no property.
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.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.
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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.
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jever98 wrote: ↑Wed Dec 07, 2022 5:08 amNot 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.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.
And if you lift at all with your “back” leg then those L/R values aren’t accurate.
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.
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Hexsense wrote: ↑Wed Dec 07, 2022 8:55 amPart 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.
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)Hexsense wrote: ↑Wed Dec 07, 2022 8:55 amPart 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.
Whats the deal with favero assimo's - a new version anytime soon?
It's all about the adventure .
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.
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.
Oh really!? Have just had a look, not been able to find anything in particular
It's all about the adventure .
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