Metrigear pedal spindle-based weenie-compatible power meter

Discuss light weight issues concerning road bikes & parts.
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djconnel
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by djconnel

Okay -- I stand corrected. I was sloppy in my language. I should have written "targeted".

I think the key message is that if you want power for the bulk of the 2010 season, I wouldn't bet my training on this one being installed and running by 31 March. But if one is happy for example with ones present powertap, but is contemplating something race-wheel-compatible, it might make sense to watch this one rather than invest in a Quarq or SRM.

tranzformer
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by tranzformer

So how does this compare to the ICYCLOPOWER: E’SY POWER? Basically same idea?

New power meter: http://www.o-synce.com/en/cyclometer-power.html
ICYCLOPOWER: E’SY POWER

ICP enable to measure the exact vertical & horizontal power the biker is using on the pedal. It‘s the only solution in the world which can be easily mount w/o complicated tools or knowledge, can be changed to any kind of bicycle in a few minutes and will be able to get:
    • an exact power measurement over the crank set angle position.(biomechanical analyzing)
    • enable to a comparison of power with each leg (performance optimization)
    • utilizate the aerodynamic drag force (to optimize to the most economic position on the bike -aerodynamic in relation to biomechanical movement) Combinable with the MACRO X series. Available mid of 2010.

Image[/quote]

tranzformer
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by tranzformer

The Stig wrote:I would think that measuring power at the pedals is like measuring HP at the crankshaft in an engine...I think that the best way to measure power accurately are at the wheels or wheel horsepower as they say, minus the rotational weight/friction of the drivetrain....


Anyone have an idea how much power is lost through the drivetrain? I know a rough estimate for a FWD/RWD car is 10-12% and an AWD car is ~20-25% from the crankshaft horsepower compared to the wheel horsepower.

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djconnel
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by djconnel

Approx 3%. Although Kraig Willett reported the difference between a new and old chain can be around 3 watts, by his measurements of SRM + Powertap.

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bcheung
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by bcheung

Thanks for the info! I'm really looking forward to following this product's development!

tranzformer
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by tranzformer

3% isn't really that much, seems like that is well within the SD so probably isn't statistically significant.

youngs_modulus
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by youngs_modulus

djconnel wrote:Right: You could imagine looking at a DFT of a recent time sampling of the signal, where you'll find peaks at f and 2f, where f = 2 pi / cadence. It would take a few pedal strokes to totally lock in to this. But those guys know more about this stuff than I do....



Your comment about Fourier transforms got me thinking...why does this device have an accelerometer at all? I know in a previous post I mentioned getting cadence as a function of time, but now I'm not sure that's such a good idea. These accelerometers are going to be very small, and their natural frequency will be quite high. They'll be picking up all sorts of extraneous stuff, and you'll have to do a fair amount of signal processing to filter it out. After all that, the velocity number you get may not be any more accurate (or any higher resolution) than a simple chainstay pickup. So why include accelerometers?

Maybe I'm wrong about the amount of data teasing required...I guess we'll find out in 6-12 months :)

Cheers,

Jason

The Stig
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by The Stig

tranzformer wrote:3% isn't really that much, seems like that is well within the SD so probably isn't statistically significant.
\

3% maybe insignificant over a short distance but over long distances like stage racing, it could be mean the difference between winning and loosing...just like in motorsports, 1 or 2/10's of a second difference per lap is small, but over a race distance is significant. But that's just me....
Sempre Ferrari

bikemesenger
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by bikemesenger

The Stig wrote:3% maybe insignificant over a short distance but over long distances like stage racing, it could be mean the difference between winning and loosing...just like in motorsports, 1 or 2/10's of a second difference per lap is small, but over a race distance is significant. But that's just me....


But why does that matter if your hub based powermeter reads 3% lower then your crank based powermeter? As long as they are both reading consistently the same numbers it doesn't matter if one is reading the 3% drivetrain loss.

On a side note one of the guys that is behind the design of this powermeter is a member of this forum so maybe he will come in this thread and answer the questions.

jediknights
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by jediknights

isn't what matters most is using the power meter for a training utensil and matching it with your zones, and not how big the wattage # is weather its coming from the hub or the cranks or hear in the pedal?

thanks for the awesome info dj.
Theforcetraining.com

youngs_modulus
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by youngs_modulus

The Stig wrote:
tranzformer wrote:3% isn't really that much, seems like that is well within the SD so probably isn't statistically significant.
\

3% maybe insignificant over a short distance but over long distances like stage racing, it could be mean the difference between winning and loosing...just like in motorsports, 1 or 2/10's of a second difference per lap is small, but over a race distance is significant. But that's just me....


But we're just talking about the raw wattage number here. It's not like you'll be making 3% less power in a time trial if you measure at the crank instead of the rear hub.

In training for a 40K time trial, it would work like this:

- Do whatever test to establish a threshold power number;
- Train based on that number;
- Race the time trial based on your improved threshold power number.

The absolute wattage number never plays into it--you're only interested in relative improvements. If your PowerTap data tell you that your threshold power is 300 watts, you're not going any slower (or faster) than your identical twin whose threshold power is 303 watts according to his SRM.

So I'm not sure exactly what you're trying to say here. What exactly is it that you're trying to say?

Cheers,

Jason

Raxel
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by Raxel

youngs_modulus wrote:
djconnel wrote:Right: You could imagine looking at a DFT of a recent time sampling of the signal, where you'll find peaks at f and 2f, where f = 2 pi / cadence. It would take a few pedal strokes to totally lock in to this. But those guys know more about this stuff than I do....



Your comment about Fourier transforms got me thinking...why does this device have an accelerometer at all? I know in a previous post I mentioned getting cadence as a function of time, but now I'm not sure that's such a good idea. These accelerometers are going to be very small, and their natural frequency will be quite high. They'll be picking up all sorts of extraneous stuff, and you'll have to do a fair amount of signal processing to filter it out. After all that, the velocity number you get may not be any more accurate (or any higher resolution) than a simple chainstay pickup. So why include accelerometers?

Maybe I'm wrong about the amount of data teasing required...I guess we'll find out in 6-12 months :)

Cheers,

Jason



Yes, the pedaling force will oscillate with the pedaling frequency so we do not need accelerometers to get the cadence at all. Even simpler method to get cadence is putting a simple rotary encoder at the pedal axle.

That said, 3-axis accelerometers and gyros chips are very small and cheap nowadays, and I think we can do something better with more sensory data.

mca56
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by mca56

I think a bigger issue will be pedal compatibility. I checked my old set of Speedplay Zero Ti and they do indeed have pedal flats. Neither my Dura Ace 7810 nor my Look Keo Ti have wrench flats. I have no interest in going back to Speedplays. I love the features of this power meter, however, it appears that the trend away from wrench flats on newer pedals may be an issue.

The Stig
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by The Stig

youngs_modulus wrote:
The Stig wrote:
tranzformer wrote:3% isn't really that much, seems like that is well within the SD so probably isn't statistically significant.
\

3% maybe insignificant over a short distance but over long distances like stage racing, it could be mean the difference between winning and loosing...just like in motorsports, 1 or 2/10's of a second difference per lap is small, but over a race distance is significant. But that's just me....


But we're just talking about the raw wattage number here. It's not like you'll be making 3% less power in a time trial if you measure at the crank instead of the rear hub.

In training for a 40K time trial, it would work like this:

- Do whatever test to establish a threshold power number;
- Train based on that number;
- Race the time trial based on your improved threshold power number.

The absolute wattage number never plays into it--you're only interested in relative improvements. If your PowerTap data tell you that your threshold power is 300 watts, you're not going any slower (or faster) than your identical twin whose threshold power is 303 watts according to his SRM.

So I'm not sure exactly what you're trying to say here. What exactly is it that you're trying to say?

Cheers,

Jason


all I'm saying is that for me, I prefer measuring power at the wheel, net of any drivetrain/frictional losses...I'm looking at it from an automotive background/perspective, which I think is more accurate. Like I said...that's me. We're not quite on the same page as you're referring to raw wattage, while I prefer net wattage.
Sempre Ferrari

Ypsylon
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by Ypsylon

If the price stays at $1000 you could get a nice pair of 4hole shoes before you reach the price of an SRM or one of the lighter powertaps. More pedals couldn't hurt, but if those prove to work well, they are definetly a weenie option, and if I see this right there are no magnets, cables or sensors on the bike, which I appreciate.
"Nothing compares to the simple pleasures of a bike ride," said John F. Kennedy, a man who had the pleasure of Marilyn Monroe.

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