World's smallest power meter attaches to valve stem and costs $129
12-06-16, 02:32 PM
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12-06-16, 02:33 PM
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12-06-16, 02:35 PM
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Max Wu As a Professional World Cyclist, I find AROFLY® to be the ultimate Biking solution. AROFLY® , helps me in monitoring all the biking data in real time during my practice, which includes, power, speed, cadence, heart rate and a lot more. It is convenient to handle, and very easy to install. AROFLY® is one of the best biking meters, I have ever experienced.
Eva XieEvery biking contest is very important; every practice is hard preparation for the main event. Instant and precise biking data and feedback is most needed for my biking preparation. For a demanding professional Cyclist like me, to improve and get an overall bike training and efficiency in a short time, AROFLY® is my best choice
12-06-16, 02:36 PM
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12-06-16, 02:38 PM
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Another post with more info:
Overall force on the ground (total front and rear) can't change due to pedaling, but there is a weight shift between front and rear. Push the pedal, weight comes off the front of the bike and onto the rear. Push the pedal harder, more weight comes off the front of the bike. The extreme case being where the front wheel lifts altogether and you do a wheely. So there is a direct relationship between the power you are hitting the pedal with, and the reduced pressure in the front tyre. Measure this on a cyclical basis, and its easy to filter out short term transients such as bumps, and long term changes such as temperature. I haven't done the maths, and currently have a few gaps such as whether it needs to know your overall bike plus rider weight. (I suspect that as it's only pressure difference you are looking at and weight is constant, that it cancels itself out in the maths, but that might be BS) Anyway, I think that's the gist of it.
Overall force on the ground (total front and rear) can't change due to pedaling, but there is a weight shift between front and rear. Push the pedal, weight comes off the front of the bike and onto the rear. Push the pedal harder, more weight comes off the front of the bike. The extreme case being where the front wheel lifts altogether and you do a wheely. So there is a direct relationship between the power you are hitting the pedal with, and the reduced pressure in the front tyre. Measure this on a cyclical basis, and its easy to filter out short term transients such as bumps, and long term changes such as temperature. I haven't done the maths, and currently have a few gaps such as whether it needs to know your overall bike plus rider weight. (I suspect that as it's only pressure difference you are looking at and weight is constant, that it cancels itself out in the maths, but that might be BS) Anyway, I think that's the gist of it.
Even if the weight distribution were constant, you'd still have small pressure changes because the tire will deform differently during the power stroke. If that was consistent enough, and you measured precisely enough, it sounds plausible that you could derive torque from that.
12-06-16, 02:46 PM
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Overall force normal force on the ground (total front and rear) can't change due to pedaling. (although it can, if your pedaling is bouncing you up and down but never mind that)
Even if the weight distribution were constant, you'd still have small pressure changes because the tire will deform differently during the power stroke. If that was consistent enough, and you measured precisely enough, it sounds plausible that you could derive torque from that.
Even if the weight distribution were constant, you'd still have small pressure changes because the tire will deform differently during the power stroke. If that was consistent enough, and you measured precisely enough, it sounds plausible that you could derive torque from that.
12-06-16, 02:48 PM
#32
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I've shown vendors to the door for saying stuff like this, or at a minimum, have asked that they arrange for an engineer to spend a half hour with me, alone.
I realize that it is likely a marketing guy but this doesn't make me want to buy their products.
-Tim-
I realize that it is likely a marketing guy but this doesn't make me want to buy their products.
-Tim-
12-06-16, 02:52 PM
#33
Chases Dogs for Sport
2cm by 2cm hanging on your valve stem. That's relatively huge. At speed, I wonder if you can feel it bounce the tire/wheel? And if it's based on tiny differences in air pressure, what happens when you hit a bump (BIG difference in internal air pressure) or experience a strong wind gust (big difference in external air pressure)? There are some significant logical gaps here.
If it sounds too good to be true (and it does), it probably isn't real.
If it sounds too good to be true (and it does), it probably isn't real.
Last edited by FlashBazbo; 12-06-16 at 03:04 PM.
12-06-16, 02:54 PM
#34
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I think they were originally designed to detect when hard drives were dropped so they could park the heads.
So all you have to do is a lot of signal analysis and filtering to detect the pedal strokes.
12-06-16, 02:58 PM
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Maybe it keys on micro changes in air density, like the tracking device in "Alien."
12-06-16, 03:00 PM
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This is what appears in the comments thread below that original article-
"Via the tyre valve the Arofly measures tiny tyre pressure variances. According to producer Taiwan’s TBS Group, “the bicycle tyre is the first to know your pedaling power effectiveness by its reaction force from the ground. Through core and patented algorithm and advanced calibration technology the precise pedaling power is registered and with that the cycling performance. The Arofly is a hi-tech, precision ‘Pressure Sensor’ that turns tiny air pressure variances into digital data.”
Arofly: World?s Smallest Power Meter - Bike Europe
Another post with more info:
Overall force on the ground (total front and rear) can't change due to pedaling, but there is a weight shift between front and rear. Push the pedal, weight comes off the front of the bike and onto the rear. Push the pedal harder, more weight comes off the front of the bike. The extreme case being where the front wheel lifts altogether and you do a wheely. So there is a direct relationship between the power you are hitting the pedal with, and the reduced pressure in the front tyre. Measure this on a cyclical basis, and its easy to filter out short term transients such as bumps, and long term changes such as temperature. I haven't done the maths, and currently have a few gaps such as whether it needs to know your overall bike plus rider weight. (I suspect that as it's only pressure difference you are looking at and weight is constant, that it cancels itself out in the maths, but that might be BS) Anyway, I think that's the gist of it.
"Via the tyre valve the Arofly measures tiny tyre pressure variances. According to producer Taiwan’s TBS Group, “the bicycle tyre is the first to know your pedaling power effectiveness by its reaction force from the ground. Through core and patented algorithm and advanced calibration technology the precise pedaling power is registered and with that the cycling performance. The Arofly is a hi-tech, precision ‘Pressure Sensor’ that turns tiny air pressure variances into digital data.”
Arofly: World?s Smallest Power Meter - Bike Europe
Another post with more info:
Overall force on the ground (total front and rear) can't change due to pedaling, but there is a weight shift between front and rear. Push the pedal, weight comes off the front of the bike and onto the rear. Push the pedal harder, more weight comes off the front of the bike. The extreme case being where the front wheel lifts altogether and you do a wheely. So there is a direct relationship between the power you are hitting the pedal with, and the reduced pressure in the front tyre. Measure this on a cyclical basis, and its easy to filter out short term transients such as bumps, and long term changes such as temperature. I haven't done the maths, and currently have a few gaps such as whether it needs to know your overall bike plus rider weight. (I suspect that as it's only pressure difference you are looking at and weight is constant, that it cancels itself out in the maths, but that might be BS) Anyway, I think that's the gist of it.
12-06-16, 03:01 PM
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I confess that I've never considered this idea, and if it's not a scam it's pretty brilliant because it's simple and plausible.
12-06-16, 03:07 PM
#38
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People are figuring out all kinds of ways to use the tiny accelerometers that are found in cell phones.
I think they were originally designed to detect when hard drives were dropped so they could park the heads.
So all you have to do is a lot of signal analysis and filtering to detect the pedal strokes.
I think they were originally designed to detect when hard drives were dropped so they could park the heads.
So all you have to do is a lot of signal analysis and filtering to detect the pedal strokes.
The device sounds plausible. Whether or not they built it right, I can't say. And a lot more accurate than what Strava gives me. I don't have to get 98% accuracy... I'm not going into pro track racing.
I've been wanting to add a cadence sensor. So, might as well give this a try. It should be fun.
So... here's to hoping my new power meter arrives before Christmas.
BTW: $129 + $30 Shipping = $159.
12-06-16, 03:23 PM
#39
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12-06-16, 03:33 PM
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GPS could be used to calibrate wheel diameter, speed, and various speed related aerodynamics.
GPS isn't too great with elevation, but it could help with that too.
Other typical phone sensors? The device apparently requires a smartphone.
Oh, also ambient pressure can be used to estimate elevation, or elevation change.
As mentioned, coasting (top/bottom pedal stroke) deceleration is probably critical, and if it is assumed to have zero force, then weight and other factors don't need to be calculated. I suppose I shouldn't try my PowerCranks with it
12-06-16, 03:33 PM
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Seems like the claims are simple enough to verify. All they need to do is to install a bike with their device and a more conventional power meter, ride it over a range of conditions, and plot the readings of one versus the other.
12-06-16, 03:38 PM
#43
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12-06-16, 04:06 PM
#44
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I would hope that it would be designed to self-calibrate, at least for some things.
GPS could be used to calibrate wheel diameter, speed, and various speed related aerodynamics.
GPS isn't too great with elevation, but it could help with that too.
Other typical phone sensors? The device apparently requires a smartphone.
Oh, also ambient pressure can be used to estimate elevation, or elevation change.
As mentioned, coasting (top/bottom pedal stroke) deceleration is probably critical, and if it is assumed to have zero force, then weight and other factors don't need to be calculated. I suppose I shouldn't try my PowerCranks with it
GPS could be used to calibrate wheel diameter, speed, and various speed related aerodynamics.
GPS isn't too great with elevation, but it could help with that too.
Other typical phone sensors? The device apparently requires a smartphone.
Oh, also ambient pressure can be used to estimate elevation, or elevation change.
As mentioned, coasting (top/bottom pedal stroke) deceleration is probably critical, and if it is assumed to have zero force, then weight and other factors don't need to be calculated. I suppose I shouldn't try my PowerCranks with it
12-06-16, 04:07 PM
#45
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Reading the copy on the site, it's obviously written by somebody who is not a native English speaker. Though I have no opinion as to the veracity of their claims, I don't think that nitpicking the language gets us further insight.
If the company doesn't do it, clearly some cycling journal/site will do a head to head comparison with more established devices. I'll wait for that. And if the tests are positive, I'll buy one at that price, for sure.
If the company doesn't do it, clearly some cycling journal/site will do a head to head comparison with more established devices. I'll wait for that. And if the tests are positive, I'll buy one at that price, for sure.
12-06-16, 04:08 PM
#46
Chases Dogs for Sport
Lots of interesting questions here, but the most interesting is, "Does this device even exist?" It wouldn't be the first vaporware to develop a bikeforums following.
I'm calling vaporware. I think you'll be more likely to spot a live Loch Ness Monster than a fully functional one of these. I will be glad to be proven wrong.
I'm calling vaporware. I think you'll be more likely to spot a live Loch Ness Monster than a fully functional one of these. I will be glad to be proven wrong.
12-06-16, 04:13 PM
#47
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Arofly says its 10-gram device can read power, speed, cadence and other factors | Bicycle Retailer and Industry News
So... for the HR, a 3rd party accessory. Simple enough.
So... for the HR, a 3rd party accessory. Simple enough.
12-06-16, 04:13 PM
#48
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If it's worth having, DCR will do a review and give us 50 graphs comparing it to PowerTap, Quarq, p2m, and Vectors. If DCR doesn't review it, keep your money.
12-06-16, 04:13 PM
#49
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What I really need to know is if the Arofly is compatible with the SpeedX Leopard bike.
SpeedX Leopard review - BikeRadar USA
SpeedX Leopard review - BikeRadar USA
12-06-16, 04:13 PM
#50
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Just for reference the Powerpod power estimating device uses the following information:
Speed sensor - Powerpod requires a separate speed sensor to accurately determine the bikes speed
Accelerometers/Altimeter - Powerpod needs to know if you are going up or downhill. I'm not sure of the exact mechanism they use for this but powerpod needs to know if you are going up or downhill.
Wind speed - Determines the wind speed of the bike which allows powerpod to account for head/tail winds when combined with the speed sensor data.
With this information plus weight and an assumption on what your aerodynamic drag is the power is able to be estimated.
I'd imagine that this valve based power meter would need to know similar information.
The speed could be determined easily based on the rpm of the wheel with an accelerometer. Garmin produce a speed sensor that straps onto the hub that does exactly this plus many crank based power meters use a similar method.
The incline/decline I'm not so sure how this would work with this power meter.
The wind speed, I'm not so sure how they do this either. Maybe they take an average based on the pitot tube on the power meter??
I'm not really sure why they would need to know cadence as it is irrelevant for calculating power in this case ( but essential for a crank based power meter).
Speed sensor - Powerpod requires a separate speed sensor to accurately determine the bikes speed
Accelerometers/Altimeter - Powerpod needs to know if you are going up or downhill. I'm not sure of the exact mechanism they use for this but powerpod needs to know if you are going up or downhill.
Wind speed - Determines the wind speed of the bike which allows powerpod to account for head/tail winds when combined with the speed sensor data.
With this information plus weight and an assumption on what your aerodynamic drag is the power is able to be estimated.
I'd imagine that this valve based power meter would need to know similar information.
The speed could be determined easily based on the rpm of the wheel with an accelerometer. Garmin produce a speed sensor that straps onto the hub that does exactly this plus many crank based power meters use a similar method.
The incline/decline I'm not so sure how this would work with this power meter.
The wind speed, I'm not so sure how they do this either. Maybe they take an average based on the pitot tube on the power meter??
I'm not really sure why they would need to know cadence as it is irrelevant for calculating power in this case ( but essential for a crank based power meter).