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PostPosted: Tue Apr 02, 2013 9:06 am 
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Joined: Fri Nov 13, 2009 10:03 am
Posts: 77
eric wrote:
A friend of mine is beta testing them, on a bike also equipped with a current production PM and two head units running debug software.
He reported some of the numbers to me on a ride and the two units seemed to be tracking pretty well.


Somehow this has managed to go by without anyone really commenting on it.

Your friend is testing which powermeter exactly? A Garmin Vector? If so, it's nice to see that it is out doing field testing and that that there is software out there as well. That's closer to a finished product than we've heard about in ages.

Any word on the head units being tested? Are they both Garmin units?

Would love to know more information if there is more to be known. It's a nice enough tease as it is.


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PostPosted: Tue Apr 02, 2013 8:10 pm 
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Location: Santa Cruz, California, USA
Its pretty much all I feel I ought to say, and in any case I don't know much more.

But I was impressed with the accuracy on this ride, and the extent of the testing program.

At this point I would hope that any new PM would be easy to zero and would report more often than once a second/once per rpm in order to cut down on inaccuracy. The current PMs shortfalls are regularly posted on the wattage list, all they need to do is wade through the BS to find them, and then solve the problem or fix the software.

I wonder how difficult it would be for Garmin or Brimm to support SPD-SL pedals?


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Posted: Tue Apr 02, 2013 8:10 pm 


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PostPosted: Tue Apr 02, 2013 9:52 pm 
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I don't know about Brim Brothers, but I do recall Metrigear (and Garmin) stating that they would be able to support other pedal platforms in the future since their strain gauges were all located in the spindle.

Whether or not that still holds true is another story. It makes sense that Garmin will want to recoup their investment in purchasing Metrigear and the money they have put in for additional R&D via their own branded products first.

But hopefully they will put them out later on other platforms. I'd love to see them on the Time Xpresso platform or Shimano's SPD-SL platform.


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PostPosted: Tue Apr 02, 2013 10:14 pm 
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I'd love to see them on Ultralite Sports.

Just look at the thing: like Aerolite before it, it's basically all spindle:
Image

If members of this forum were the primary market.... alas.

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PostPosted: Tue Apr 02, 2013 11:54 pm 
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One non-existent product per company isn't enough for you guys? Now you want a whole suite of non-existent products?


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PostPosted: Wed Apr 03, 2013 3:44 am 
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Anyone tried the power estimate monitor from PowerTap based on heart rate? Obviously not a true power meter but looks interesting as a cheap way to get a kind of gauge

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PostPosted: Wed Apr 03, 2013 5:29 am 
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Do you mean PowerCal?

There's a review from DC Rainmaker and I'm using it too sometimes: it works reasonably well for longer, steady efforts.


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PostPosted: Wed Apr 03, 2013 10:29 am 
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Location: Finland
I guess the main issue with PowerCal is that it is not possible to follow your progress with it. When the power on given HR level increases, the PowerCal has no way of noticing it.


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PostPosted: Wed Apr 03, 2013 7:48 pm 
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Location: Denver
Kervelo, I don't think that is correct. It doesn't look at heart rate per se as an isolated metric, but rather the heart rate variability (essentially R-R interval analysis). It's biggest limitation is that you cannot use it to gauge instantaneous power changes (like a sprint)- it's ok for looking at power over time (10-30 second averages work well). I bought one a couple of months ago, and using it within its limits, I have been pretty pleased, especially considering the price! It is a good gauge of steady efforts as claus mentioned, and is useful to look at interval efforts. You certainly can use it to compare how your power improves, for example, over a certain course segment over time. Just don't expect it to function as a measure of sprint power.


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PostPosted: Wed Apr 03, 2013 8:31 pm 
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dereksmalls wrote:
Anyone tried the power estimate monitor from PowerTap based on heart rate? Obviously not a true power meter but looks interesting as a cheap way to get a kind of gauge


1. export ride data to spreadsheet
2. plot power versus heart rate

You get a big cloud. You can try smoothing power using different algorithms, even smoothing and delaying. You still get a cloud. HR isn't a good predictor of power.

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PostPosted: Wed Apr 03, 2013 10:54 pm 
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Location: Denver
djconnel, that is absolutely true. But the power cal is not using heart rate as its metric, nor does it use smoothing- it is looking at heart rate variability (that is, beat to beat variability) in conjunction with heart rate (the algorithm is obviously proprietary, because I was not able to find it published in the exercise physiology literature). Take a look here http://bikehabit.blogspot.com/2012/07/cycleops-powercal-versus-quarq-is.html, and here http://teamrodrigo.com/2012/07/23/comparing-power-readings-from-powercal-and-powertap/ for an explanation of what I mean. There is a correlation between Power Cal and true power measurements, that is obviously better over longer time epochs (that is, you can't get an accurate measure of instantaneous power with any accuracy), but is nevertheless useful as a tool for measuring and training under conditions of sustained power efforts- and a lot cheaper than an SRM. As always, you get what you pay for, but it is not a scam.


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PostPosted: Wed Apr 03, 2013 11:36 pm 
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I have thought the power cal is a little like this

http://www.firstbeat.fi/consumers/heart-rate-monitors

Close but, not "really exactly" what is happening, just like ibike.


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PostPosted: Wed Apr 03, 2013 11:39 pm 
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If powercal is relatively accurate over long averages of time, why can't someone use a post-processing approach and use regular HRM data to create power?


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PostPosted: Thu Apr 04, 2013 6:13 am 
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post-processing won't work because the data are not there to access- you need to be able to analyze (in milliseconds and in real time) the variability from one heart beat to the next- that is not the same as heart rate itself.

uraqt, I suspect they are using some algorithmic variant of that. There is a lot of work done on heart rate variability as it relates to autonomic function, and this is how they are deriving the power measurements.


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PostPosted: Thu Apr 04, 2013 7:13 am 
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if i have 2 riders who ride the same course in the same time with identical HRs (and hence identical HR rate of change) but 1 rider weighs 50kg and the other weighs 100kg, how can this system possibly report an accurate power number for either rider? even in long, steady state efforts? are weight and CDA so insignificant that they can be ignored? getting beaten up climbs be smaller, lighter riders who make significantly less than me tells that me that they cannot.


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Posted: Thu Apr 04, 2013 7:13 am 


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