A new power, cadence and speed meter called Arofly that attaches to an inner tube valve and weighs only 10g is available for US$129 (around £101).
Arofly sends your cycling data via a Bluetooth connection to be displayed in real time on a custom mobile app on your smartphone.
It has a diameter of 2cm, a height of 1.9cm, and fits to both Schrader and Presta (via a titanium adaptor) valves in seconds. The 10g weight includes the coin cell battery.
Obvious question: how the hell does it work?
“Originating from aerospace technology, Arofly is the result of years of research and cooperation between aerospace scientists and sports biomechanics professors, developing a patented air pressure differential technology based on the pitot tube design, from the F-117 combat aircraft,” says the Taiwanese group behind it, TBS Group Corporation.
Cycling sales blurb is chock-full of aerospace references.
A pitot tube is a pressure measurement instrument that measures fluid flow velocity. As well as being used in aircraft (not just the F-117!), pitot tubes measure the water speed of boats, for example, and liquid, air and gas flow speeds in industrial applications.
The inventors say that once attached to the valve of the inner tube, the Arofly measures the tiny variances in air pressure to work out the power being applied by the rider. That’s all we know right now. Sorry. We’ve asked for more info though.
The Arofly has an operating temperature of -30°C to 85°C – safely covering everything you’re likely to ride in – and it’s said to be both waterproof and dustproof.
The Arofly is compatible with iPhone 4S or later and Android OS 4.3 or later.
How well does it work? We haven’t got a clue. We’ve not used the Arofly nor even got our hands on one yet. We’ll do our best to get one in for test.
For more information go to www.aroflybike.com.
73 thoughts on “Introducing Arofly, “the world’s smallest power meter” + video”
Such a shame this is not ant+
Such a shame this is not ant+! (if it works)
If this works it will sell
If this works it will sell like crazy.
Can’t see power meters being
Can’t see power meters being a big seller in the folding and shopping bike market. Would still love to see DC Rainmaker have a look at it.
Without a contact point with
Without a contact point with the drive train I cant see how this is going to be more accurate than the free strava guesstimate based on ones weight speed etc
Velomark wrote:
Exactly. It’ll possibly be marginally more accurate as it might be able to obtain better information regarding wind speed and direction
Looks like just another
Looks like just another iteration in the iBike Newton power meter that’s been on the market for several years. It’ll be interesting to see how accurate it is…
10grams imbalance is enough
10grams imbalance is enough to chuck you over a hedge on a descent.
Freddy56 wrote:
Its not you know.
Not sure how wheel speed is
Not sure how wheel speed is related to power. how does this take account of
1) gradient/elevation gain
2) wind speed/direction
3) rider weight
4) drafting
These are my guesses:
These are my guesses:
To summarise I think the app does a lot of the heavy calculations similar to Strava, and this device measures wind speed / direction to help make the data more accurate. This probably explains why it doesn’t put out ANT+ signal, because a reading of wind speed alone will be useless to other devices.
I bet £50 this won’t work on rollers.
Errrr, no!
I’m no physicist, but my meagre grasp of the concepts calls BS on this. As you say, a pitot tube can measure the velocity of an object passing through a fluid or gas. So, this device can measure, to a greater or lesser degree of accuracy, how fast the valve cap is moving relative to the airflow around it. Even if it couples this with an array of accelerometers, it can’t measure power. It would have to know other factors such as gear ratio and cadence to work out power from the speed of rotation of the wheel. The software in the phone is making a best guess based on known factors, but there must be a huge margin of error – about as accurate as my Garmin HRM that thinks I’m dead for half the ride. So even if it guesses well, people who want this data want it spot on, or it’s useless.
I think the idea is that it
I think the idea is that it calculates power based on air pressure changes within the tyre – that is, you apply pressure to the pedals and that causes a small but measurable change in pressure within the tyre at the valve. Sort of like standing on a balloon, causing the balloon to deform. That means it does more than measure its own air speed or the rate at which the wheel moves (as others are suggesting). I assume that’s how they detect cadence even though it only attaches to the front wheel – the cyclic nature of pressure change as you press the pedals is presumably used to infer how fast you’re pedalling.
It seems like it would be fairly unreliable though. Surely hitting a bump in the road will cause similar changes in air pressure. I like the idea of a £100 power meter, but it just seems like it would be too unreliable by not directly measuring the force you exert.
asdfqwerty wrote:
Almost, you are heading in the right direction, but as described above you are endangering Newton’s laws.
Overall force on the ground (total front and rear) can’t change due to pedalling, 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.
Griff500 wrote:
Nope, there is not a direct realationship, there is a indeterminate coupling between the two, and that’s why it could never work by measuring tyre pressure.
Using your analogy of the front wheel lifting off the road if you put power in, that’s only true if you have your weight towards the rear of the bike, move your weight forward, you’ll get a different reading, change the angle of your peak torque with respect to the ground and you’ll get a different result. Put different forces through the bars, you’ll get different results. Do pretty much anything and you’ll get different results. At best all you could do woud be determine cadence.
I can also say from my day job, which has in the past involved developing electronics and software to produce a complete solution for the optical measurement of road surface roughness, that it’s far easier to say “it’s easy to filter out transients”, than to actually filter out those transients 🙂
IanMunro wrote:
Nowhere did I say this device works, and I even said in another post that I won’t be at the head of the queue when the product launches in February. As a scientist by training however I don’t draw conclusions without the facts, and on this product we don’t have all the facts. I have only tried to explain how Arofly say it works, explain the science behind what they are trying to do, and dispel the red herrings you and others posted about the device measuring atmospheric pressure rather than tyre pressure. (Despite the fact that Arofly state in numerous places that it measures tyre pressure and in the manual state that the core of a Presta valve must be unscrewed.)
Yes there are big gaps in the Arofly explanation provided to date, and if it works, they clearly have a trick they are not telling us about. The lack of setup data such as weight or tyre size is mindboggling. I contacted Arofly to highlight the level of skepticism and asked for more information (adding that I am a Physicist and Electronic Engineer to try and add some credibility). They responded immediately, stating that they understand the skepticism and will give me further information. My breath is baited!
asdfqwerty wrote:
As you say, road deformations, moving in your saddle, standing, sitting would all create larger tyre deformations than those from cadence / power variations.
I say it’s BS. No better than a strava gestimation. The website provides no information at all, but patents have been applied for which means the IP is in the public domain. If it was new and ground breaking, it would be all over the engineering world. It’s not. I say BS
I’d want one if it works, but
I’d want one if it works, but I’m somewhat sceptical. I don’t see how it can measure cadence and I’d be surprised if the power “measurement” is accurate.
with PM if cheap does it
with PM if cheap does it matter if accurate. As long as power is consistent then you measure yourself on that and if it is 50W out, who cares unless you comparing to others using 1K PM’s ?
I’m a bit sceptical too. I’d
I’m a bit sceptical too. I’d certainly want to know a lot more before I parted. But if something workable is available at this kind of price then i reckon there’d be a good take up.
The idea of measuring tyre pressure makes some sense. as asdfqwerty says, the pressure would vary in time with your pedalling, so it can work out cadence. it’d be pretty simple to filter out extraneous spikes caused by a bump as there’s no way you could suddenly double cadence (as in get a 2nd spike in a wheel revolution). The pressure changes would also be a function of weight and force applied, so it could take that into account. Accelerometer(s) would work out wheel speed and rate of climb/descent.
It would never be as accurate as a meter that is actually measuring the forces through the drivetrain. But it could be a reasonable approximation. And as long as it is consistent with itself, does it really matter if it report 300 watts or 320 watts? Needs ANT+ though.
Guanajuato wrote:
was reading a blog piece yesterday which says to rely on BLE only is going ot kill a product. Those of us with Garmins and that is a lot with want Ant+ and BLE are nowhere near killing it off (piece is on Ray Maker’s things to read if interested) .
the standard is ANT+ and to develop something without to try and keep some costs down is folly, IMHO.
ianrobo wrote:
I’m in the BLE camp and I think that’s the future. Yes, ANT+ is certainly more common these days, but most modern phones have a BLE stack built into them, so it’s easier to get devices talking to your phone with BLE.
I think Garmin are somewhat resting on their laurels at the moment and all it takes is a good competitor using BLE to shake them up a bit.
hawkinspeter wrote:
It’s the fact that you can connect ANT+ to multiple devices that makes it so versatile.
I can connect my power meter to my Garmin, Zwift and TrainerRoad all at the same time using ANT+.
If I was using Bluetooth (my pm is dual band) then I’d only be able to connect it to one.
n8udd wrote:
I don’t have any problem connecting my phone to multiple BLE devices either.
hawkinspeter wrote:
That is a different scenario. The point here is that ANT+ broadcasts, and doesn’t require a handshake, so a cadence sensor for example can be picked up by a sportswatch, cycle computer and phone all at the same time. I use this facility as well. BLE can’t do this.
Pub bike wrote:
That is a different scenario. The point here is that ANT+ broadcasts, and doesn’t require a handshake, so a cadence sensor for example can be picked up by a sportswatch, cycle computer and phone all at the same time. I use this facility as well. BLE can’t do this.— hawkinspeter
I see – I didn’t realise that.
However, I still think BLE use will increase in the future due to the sheer number of BLE enabled phones. There’s also the argument that ANT+ broadcasts aren’t secure, but I don’t see that as being a problem (unless you’re wearing a HRM and telling lots of lies).
n8udd wrote:
for me it is a no brainer would never use a phone to track my ride, mainly because Iphone battery is so shite and frankly Garmins are so good. My devices fails never to connect. This is the post I refer to
http://keithhack.blogspot.co.uk/2016/11/why-hasnt-ant-been-crushed-by-ble.html
ianrobo wrote:
I think I remember from a podcast of his that there are licensing and membership issues with ANT of something like £25k. That would be prohibitive to most startups.
If has an accelerometer in it
If has an accelerometer in it, it could measure cadence easily. Unless you’ve got the smoothest pedalling stroke in the world, it could easily detect the slight pulse in acceleration going through the wheel on each power stroke.
guyrwood wrote:
Hmm… Going to have a lot of noise to remove from the road surface if it’s looking for micro accelerations.
Like others I’d be very surprised if this is accurate but if DC Rainmaker reviews it I’ll keep an open mind.
Completely useless to most without ANT+ though.
racingcondor wrote:
Where do people get this accelerometer Myth. The OP is clear, it measures air pressure, and as pressure in the tyre changes with each pedal stroke cadence measurement comes for free! Cadence is half the period of the pressure variation, power comes from the magnitude of the pressure variation. If you measure the front wheel, pressure reduces with greater pedal power. On the rear wheel it is the converse. Basic Newton’s 3rd law. Simples!
Griff500 wrote:
Where do people get this accelerometer Myth. The OP is clear, it measures air pressure, and as pressure in the tyre changes with each pedal stroke cadence measurement comes for free! Cadence is half the period of the pressure variation, power comes from the magnitude of the pressure variation. If you measure the front wheel, pressure reduces with greater pedal power. On the rear wheel it is the converse. Basic Newton’s 3rd law. Simples!
— guyrwood
The schematics are easily accessible online, it contains an accelerometer. As for its intended purpose, however…
asdfqwerty wrote:
I stand corrected. I can’t see the schematics on their site. Do you have the link please?
Griff500 wrote:
I suspect most people talking about accelerometers just assumed it had one, rather than had read about them anywhere. The application for FCC approval in America shows schematics, etc.: https://fccid.io/2AJGD-AROFLY01 In the ‘Block Diagram’, the BMA250E component is a 3-axis accelerometer.
asdfqwerty]
I suspect most people talking about accelerometers just assumed it had one, rather than had read about them anywhere. The application for FCC approval in America shows schematics, etc.: https://fccid.io/2AJGD-AROFLY01 In the ‘Block Diagram’, the BMA250E component is a 3-axis accelerometer.
[/quote
Thanks for that. I note they also claim the sensor measures cycling speed. A wheel mounted accelerometer would measure wheel rotations and therefore give speed. Tyre pressure sensor measures crank rotation, therefore cadence, and front/rear weight shift to give power measurement.
Whether it works or not, it is an interesting device, and certainly not cheap to develop. If only someone would put that amount of effort into developing a sensible bike camera with 6+ hours recording and without the aero of a brick!
Griff500 wrote:
The schematics show a barometer, but its range is 0.3 to 1.1 bar, so can’t directly measure tyre pressure. And I’m puzzled by the reference to pitot tubes in the article.
Their website says they have Taiwanese and worldwide patents, but I can’t find them. (Though I did find one for a power meter using a static strain gauge on the rear drop-out. Interesting idea)
Looks like it does measure
Looks like it does measure tyre pressure variance. Here’s what I managed to find (http://www.bike-eu.com/sales-trends/nieuws/2016/10/arofly-worlds-smallest-power-meter-10127915):
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.”
As that was from October 25th, I wonder why no-one’s actually tested one of these?
Yeah as long as it’s
Yeah as long as it’s consistent you can do your own arithmetic on rides to work out what you should be riding at after you get used to it.
Hyper skeptical though.
” the Taiwanese group behind
” the Taiwanese group behind it, TBS Group Corporation.”
They are pulling your leg, T(otal) BS corporation….
This is brilliant: a Fredcebo
This is brilliant: a Fredcebo. Screw it to your inner tube valves and let the meaningless numbers it spews out convince you to ride faster. But, like a sugar pill is to expensive medication, it only works if you don’t question it.
restrict it from zwift use…
Ahahaha…
Will wait new KOMs in Zwift from dumb schoolboys using this empirical meter of “power” – like that who gives out 600w x15 min … schollboy from pro pelothone)))
Why?!
But no one has seen it… and you can’t buy it.
This has to be the most pointless post I’ve seen to date on Road.cc!!
If you want to increase awareness in this fictional product, just tweet about it!
You’ve literally copied info from the website!
What is the point?!
I had a quick look at the app
I had a quick look at the app store and the “arofly” app by Louis Chen has had zero reviews. He has got a Bluetooth remote control car app that has had 1 review.
I am yet to be convinced to be honest
All smells a bit whiffy to me
First off, I graduated with a degree in electronics in 1988 so I can read a schematic with the best of them. I can also watch a video. And having watched the video on the aerofly website which claims that the unit can measure heart rate, and that it could be adopted by “commuting students” I’m really not sure.
I once got the job of designing a gadget to determine how many paintballs a paintball gun could fire by analysing pressure variations in the compressed air cylinder used to propel the balls out the gun. It took a SERIOUS amount of doing and I had the advantage of being able to easily isolate the pressure change caused by firing the ball from background variations a) because the pressure change was sizable and b) there were no background variations.
It took us a long time to get this right and we had to do some pretty fancy stuff in the end to compensate for temperature changes – the number we calculated was reliably within 10% of the actual number of paintballs the air in the tank could actually fire.
This aerofly device claims a massive operating temperature range and I just find it hard to believe that it’s possible to pick out variations in pressure caused by application of force to the pedal from background variations caused by uneven road surfaces, pressure changes caused by heating and cooling of the braking surface etc. etc. I’m also not at all sure that you can reliably translate this into a meaningful power measurement. Potentially possible to get a relative measure (i.e. “you’re pedalling harder now than you were”), but I’d not even bet on that.
I’m pretty sure that it’s beyond my capabilities to design this device and get it working reliably to a point I’d by happy with.
tonyleatham wrote:
While you were playing with toys, I was doing miltary signal processing.
To be fair, the FBM320 pressure sensor used appears to be noted for it’s onboard temperature compensation capabilities. The fact it is only rated up to 15psi does however question how accurate it would be at the 90-100psi region many of us run our tyres at.
As for differentiating between road surface vibrations and pedal stroke? Most road vibration is in the 10’s of Hz range and random in nature. Power variation due to pedalling at a cadence of up to 90, would produce periodic variations of 0-3 Hz. Any electronics or physics undergraduate could design a digital filter to cope with that in the timeframe of an exam question! Remember also that a conventional crank mounted pressure sensor already needs to be able to filter out a the vibration not filtered out by tyre and frame, (the lowest frequency stuff closest to pedal cycle in frequency) so filtering is still necessary here.
So assuming you could get the pressure reading, the signal processing is trivial. The Pressure sensor used however doesn’t appear to be up to use anywhere near tyre pressures.
Incidentally, for those arguing Ant versus BLE, the schematic also shows Ant2.
Griff500 wrote:
I’m quite happy admitting that this device is not something I could design – I speak from experience of having worked on something similar. Part of the reason I think it’s incredibly complicated is that the amplitude of the pressure variation caused by pedalling I suspect is incredibly small and in the real world, all assumptions about what can and can’t be filtered usually don’t survive the first test. Add to that the conversion time of the sensor is pretty slow (of the order of normal pedalling cadence), and I just don’t think it’s possible with this circuit.
You may scoff at my non-military experience, but I’ve worked both in defence (BAe) and consumer electronics, and by far the best people I worked with were outside of defence.
If you feel it’s something you could make work, do it and I’ll buy one off you for $129.
tonyleatham wrote:
Sorry about the scoff, but when someone opens a post by stating ” I have a degree”, they are setting themselves up!
I never said I could make it work for the price and size, I said the theory works but it’s the wrong sensor. Read my post!
As for the pressure change being ‘incredibly small”, it is exactly the same change conventional power metres measure at the crank, you are just measuring it at a different point in the system. (Back to Newton 3rd).
Griff500 wrote:
I’m quite happy admitting that this device is not something I could design – I speak from experience of having worked on something similar. Part of the reason I think it’s incredibly complicated is that the amplitude of the pressure variation caused by pedalling I suspect is incredibly small and in the real world, all assumptions about what can and can’t be filtered usually don’t survive the first test. Add to that the conversion time of the sensor is pretty slow (of the order of normal pedalling cadence), and I just don’t think it’s possible with this circuit.
You may scoff at my non-military experience, but I’ve worked both in defence (BAe) and consumer electronics, and by far the best people I worked with were outside of defence.
If you feel it’s something you could make work, do it and I’ll buy one off you for $129.
— Griff500 Sorry about the scoff, but when someone opens a post by stating ” I have a degree”, they are setting themselves up! I never said I could make it work for the price and size, I said the theory works but it’s the wrong sensor. Read my post! As for the pressure change being ‘incredibly small”, it is exactly the same change conventional power metres measure at the crank, you are just measuring it at a different point in the system. (Back to Newton 3rd).— tonyleatham
Sorry my degree offends you – what would you rather I do? Pretend not to have one?
In my book, buggering about with minuscule variations in pressure reported by a slow sensor that no matter what the data sheet says will be prone to temperature drift is TOTALLY different to working with a fast strain gauge that will see a much bigger differential. I’m sure if you spend some time thinking about it, you’ll get to this conclusion in the end. Or maybe playing with soldiers hasn’t given you enough experience.
[
[
Sorry my degree offends you – what would you rather I do? Pretend not to have one?
In my book, buggering about with minuscule variations in pressure reported by a slow sensor that no matter what the data sheet says will be prone to temperature drift is TOTALLY different to working with a fast strain gauge that will see a much bigger differential. I’m sure if you spend some time thinking about it, you’ll get to this conclusion in the end. Or maybe playing with soldiers hasn’t given you enough experience.
[/quote]
No no offence whatsoever, I just didn’t realise it was necessary to list qualifications on this board at the start of a post to try to justify themselves.
For somebody who claims to be an engineer, you seem to be very closed minded. Yes strain gauges are the traditional answer, but a decent set cost close to 3 figures and require a crank rebuild to fit. Doesn’t it occur to you that if somebody really does have a £100 solution which takes 5 seconds to fit, it might be worthy of consideration, especially for those amateur cyclists among us who don’t require a high level of accuracy?
You keep rabbiting on about temperature drift affecting the result, yet you don’t know what algorithm the inventor has implemented. What are you a mind reader? For example if he has assumed zero force at the neutral point (pedal at 12 o’clock) and is only looking for differential pressure round a rotation, then temperature drift may not matter to him. Response time? No different to a digital strain gauge (or were you going to implement in analogue).
As for these “miniscule” variations in pressure you seem to think exist, let me give you an example of miniscule pressure changes. In my younger days I flew gliders and hang gliders. The primary instrument used in any form of gliding is a variometer, which measures changes in air pressure, and hence indicates by how much you are climbing or descending. In 1980, 40 years ago and long before the days of “systems on a chip” my £60 variometer could easily measure a climb rate of 1 foot per second, purely on air pressure change, and yes I really do mean 1 foot. Pick it up off a table, lift it one foot, it would indicate the difference based on air pressure change alone. In comparison the 10’s of pounds force I am putting through my pedals which are trying to lift the front wheel off the ground are considerable!
Strain gauges undoubtedly give higher accuracy, not least because they measure the right side of the drive train, and also measure the power per leg. People on here have often posted wishing there were a cheaper alternative so why be so quick to dismiss such an alternative for which the theory is sound, when frankly, we don’t have the evidence to know if the implementation is also sound. Nope, lets all put the blinkers on, and do everything the way we always have!
As noted by others, this
As noted by others, this product is complete bollocks.
There’s no pitot tube in it, nor any reason it would have one.
It measures atmospheric air pressure to determine your rate of climbing or descending, and it measures wheel RPM to get velocity.
From these two variables and user entered data for weight, it will be guestimating what your power output is.
Strava will produce just an accurate result, but without this lump of tat stuck on your valve.
I have a 25yds Swimming
I have a 25yds Swimming Certificate, and I have to say I quite like the knurling.
To all those having a degree
To all those having a degree in anything: the pressure sensor does not measure tire pressure, and does not claim to. First, because it cannot do it (someone checked the datasheet), second because in order to convert it to a force, I would require the area of the tire patch. Anyone to measure the tire patch realtime?
As mentionned above by IanMunro and others: the pressure sensor measure barometric pressure and infers a rate of climb together with speed, known with the accelerometer.
Got it?
jerome wrote:
“Ian Munro and others” clearly didn’t read the Arofly blurb before guessing how it works.
Quote Arofly:
Algorithm and calibration technology
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.”
“
Yes, I agree it sounds like BS, but let’s see where they go with this.
It was me who checked the data sheet for the pressure sensor, and although as I said, it is only rated up to 15psi, that does not mean it turns into a pumpkin at higher pressures. It is very common in novel applications (Oil & Gas, process plants, miltary, submarine, polar exploration etc) to use an electronic component outwith the manufacturers rated range. It usually requires the designer to personally test and characterise the component under the conditions he intends to use it under.
Would you trust the marketing
Would you trust the marketing blob or the schematic/datasheet? They also mention a Pitot but there is no need for a Pitot to measure air pressure in the chamber, where there is no wind AFAIK.
“It is very common in novel applications […] to personally test and characterise the component” not when there are components readily available, or when you overshoot the specified range 6 folds.
What, no retraction of the
What, no retraction of the smartass “got it?” comment?
Neither. I’d trust the test I would do myself, and I’ve done similar things a number of times, sometimes in high reliability high accuracy applications.
This is often a matter of component manufacturers testing and underwriting against the standard commercial component standards and intended use, rather than going to the expense of testing to a range where the component is not envisaged to be used. If I am selling a barometer chip, why would I test and underwrite its performance to 110psi?
I’m not an expert on silicon pressure sensors, but a bit of basic research comes up with comments about the diaphragms used being not only resistant to extreme overpressure, but remaining perfectly elastic and relatively linear up to the point of fracture. Which kinda suggests if it doesn’t break, you will get some sort of sense out of it. (This is very different to overtemperature where at 125 degC or so things can rapidly start to go off a cliff.) There is no point us guessing if its good enough, because we have neither the data, nor the detailed knowledge of the algorithm or implementation these guys use.
jerome wrote:
Nowhere does it say there is a pitot tube. They say the sensor is based on F117 pitot tube technology, because pitot tubes are required measure small relative pressure changes! They presumably mean an integrated pressure sensor, a/d convertor signal processor and serial bus on a chip as opposed to the old days of analogue pressure sensors in pitot tubes. (Your bike manufacturer may well brag about his aerospace grade carbon fibre, but it doesn’t mean your bike will fly!)
“What, no retraction of the
“What, no retraction of the smartass “got it?” comment?”
Nop, not till you explain how you measure force (required for power) with only pressure.
jerome wrote:
No idea. Been wondering myself.
I’m just the guy whose researched what little there is out there on this and tried to correct a misconception. The insults are totally unjustified, but if you want to stand by your post, so be it.
I did not mean to be
I did not mean to be offensive (not native english speaker BTW), just to tell that lenghty speculative posts (not yours in particular) lead to nowhere. There is only one way we can see the device work right now (assuming it works) and this is not by measuring tire pressure, but measuring rate of climb/descent and guesstimating aerodynamic forces.
jerome wrote:
Sorry, I don’t believe the climb / descent theory for one minute. If all you were doing was measuring altitude, why on earth would you mount the sensor on the wheel and have the additional complexity of a 670mm or so cyclic change of height? Then of course there is the accelerometer. If you were using that to measure acceleration, why have it rotating? You’d spend a lot of processing power just figuring out which way is up and which way is forward. These points, plus the fact that the Arofly press release I quoted says they are measuring tyre pressure, and the clear description they give of power measurement being a function of reaction against the ground, seem very clear.
Strava already does exactly what you say based on digital map data, and does it well. Comparing my sector times with guys with power meters give remarkably close results, except when there is wind, which for Scottish cyclists like myself can sap as much power as hills.
The App set-up sheds no light the issue. They talk of switching from bike to bike and simply booting up bluetooth, yet there is no mention of providing weight figures or wheel sizes, or calibration.
“the additional complexity of
“the additional complexity of a 670mm or so cyclic change of height”
Which is easily filtered, did not you mention that already?
“If you were using that to measure acceleration, why have it rotating?”
Because you obtain speed directly and all times when substracting gravity: a = g + V^2 / R
No need for integration which would lead huge errors over time. Dead simple.
“the Arofly press release” you keep giving more faith to those Taiwanese bullsh*ters than to your own jugement.
“measuring tyre pressure” which is a dead end you admitted it.
“remarkably close results, except when there is wind” so you admit my theory is valid
“weight figures or wheel sizes” are obviously required
Got fed up of that discussion. Byebye.
OK not completely away
OK not completely away 😉
The pictures in the FCC submission clearly show a hole and a dent to depress the valve (saw that on another forum). So here is my new guess: the device actually measures tire pressure, as a mean to measure barometric pressure. This is the way they found to protect the pressure sensor, that would otherwise be exposed to water as soon as you run in a puddle. When barometric pressure drops, the tire enveloppe slighly swells and the pressure drops into the tire drops. I do not the relation between the pressure inside the tire and the pressure outside, but maybe it is close enough to 1:1 on that rather small range. As Griff500 rightly pointed out, the FBM320 has an absolute max rating of 10 bars, so they probably asked for a custom version with different gain/offset before ADC. They have to average the pressure over maybe 10s to keep only long term variations.
So to summarize: change of cyclist altitude causes change of barometric pressure, reflected by a change in tire pressure. That give a rate of climb/descent, and along with cc+bike weight gives one part of power. The other part of power required to overcome aerodynamic forces is estimated with cc speed, with is derived from the centripetal acceleration.
‘hope this is not a too long and speculative post 😉
jerome wrote:
Inventing things again? Griff500 never mentioned 10 bars anywhere, he said the supplier only rates it as far as 15psi, which is 1 Bar.
Also, as I have been at pains to point out, the manufacturer clearly states that the device measures “the reaction force from the ground”. You seem to be telling him he is wrong and it works in a totally different way!
You will also have great difficulty getting a value for the elasticity of the tyre/tube combination, which determines the relationship between internal and external pressure. 1:1, that’s a joke. How would the tyre hold 100psi if it has a 1:1 pressure relationship to the outside!
Then of course there is the not inconsiderable problem that changes in tyre pressure due to pedal power changes (the bit that Arofly have told us they measure) are much greater than the altitude related changes you are trying to measure, and will totally mnask your altitude effect.
Griff500 wrote:
Griff500 posted this. Has Griff500 been busted using multiple logins, or does Griff500 usually refer to himself in the 3rd person?
davel would like to know.
davel wrote:
No, not usually, just this once
I am thinking of holding a discussion with myself though, because i’d get more sense out of me than out of Jerome
The pressure sensor can be
The pressure sensor can be reprogrammed while in use to set a new pressure baseline, so that 1 bar range could be intended to just cover the small range of pressure variation at the valve as the tyre rotates. But, the absolute maximum pressure for the sensor is only 5 bar (72 psi), so it’s not clear if it would cope with the higher pressures used in road tyres, or if it would fail to function. (as mentioned by someone else earlier, these sensors often operate outside of their rated operational bounds – the manufacture themselves have listed this in the datasheet as the upper limit). Anyway, proof is in the pudding, maybe DC Rainmaker will get his hands on one…
asdfqwerty wrote:
Apparently it is only being released to the market in February 2017. This can go one of two ways: If it works as advertised, we will very soon see these things everywhere. If it doesn’t, we will never hear of it again. Personally, I will watch what happens with the greatest of interest, and will happily part with my £100 if it works. But I certainly won’t be at the head of the queue.
just been invited to place a pre-order….
….all i need now, is to see release date of April 1st and my decision is made!
Arofly 2019 ~Link ant+, X-Elite Bluetooth
2019/5/2
Hi all,
The AROFLY team has dedicated several experiments and tests to design the customized Sensors, Hardware and Integration of the exclusive software for the AROFLY system.
AROFLY’S dynamic air pressure system, is totally a” New Invention”. All the technology in hardware, software and algorithms had to be created from Zero. There is no similar technology and system of a power meter in the market to compare or learn from.
By accumulating information from several valuable experiments and tests, the AROFLY team identified the core value for the AROFLY power meter system.
After two full years of hard and dedicated work on more advanced technology, the AROFLY team developed, the ELITE, LINK and XELITE in 2019.
The first AROFLY model was designed in 2017. The AROFLY Sensor, worked in conjunction with a Smart Phone APP, using GPS for altitude and gradient.
The slow response of the required data from the Smart Phone was not good enough for the AROFLY sensor to identify the slope changes, causing late data output, thus confusing the cyclist.
We valued all the positive and negative feedback from the market, we listened to our customers very seriously. This feedback was discussed and has driven the AROFLY team to carry out more research, development and evaluation, to complete a new generation for AROFLY.
The following are the improvements to the New AROFLY generation, ELITE, LINK, and XELITE.
1. The AROFLY team, designed a highly sensitive pressure sensor with a MCU in the AROFLY sensor for the upgraded algorithm and filtering program, to remove interference from road conditions.
2. Designed a highly sensitive altimeter and GPS in the hardware, for quick response on slopes and gradient changes, to correct algorithm mode for data output.
3. Included additional sensors in the system as sensor fusion to collect more raw data of road condition and pedaling status, to assist the algorithm with quick & correct data output.
4. Integrated the system with more functions and riding data on the products
5. The “ LINK” version, now offers a very affordable, Bluetooth & ANT + connectivity to other Bike Computers
6. The “ELITE” & XELITE versions now offers a very affordable bike computer, with all the features and benefits of the more expensive bike computers in the market.
These new improvements will add more accuracy, consistency and flexibility to the operation of the AROFLY new generation, ELITE, LINK and XELITE.
The new product are estimated to launch June/July 2019.
Thank you for your reading.
Team Arofly
Arofly Outdoor:
https://youtube.com/watch?v=MF91PD8DrJo
Arofly Indoor:
https://youtube.com/watch?v=cil-Z0_fpFE
Arofly ELITE OPERATION:
https://youtu.be/P_2U8pJyFU8
Arofly ELITE INSTALLATION: https://youtu.be/btI-EBrjfi8
AROFLY
https://youtu.be/ZhMn7XAGYhk
Arofly Link, X-Elite
2019/5/6
Hi all,
The AROFLY team has dedicated several experiments and tests to design the customized Sensors,Hardware and Integration of the exclusive software for the AROFLY system.
AROFLY’S dynamic air pressure system,is totally a”New Invention”. All the technology in hardware,software and algorithms had to be created from Zero. There is no similar technology and system of a power meter in the market to compare or learn from.
By accumulating information from several valuable experiments and tests,the AROFLY team identified the core value for the AROFLY power meter system.
After two full years of hard and dedicated work on more advanced technology,the AROFLY team developed,the ELITE,LINK and XELITE in 2019.
The first AROFLY model was designed in 2017. The AROFLY Sensor,worked in conjunction with a Smart Phone APP,using GPS for altitude and gradient.
The slow response of the required data from the Smart Phone was not good enough for the AROFLY sensor to identify the slope changes,causing late data output,thus confusing the cyclist.
We valued all the positive and negative feedback from the market,we listened to our customers very seriously. This feedback was discussed and has driven the AROFLY team to carry out more research,development and evaluation,to complete a new generation for AROFLY.
The following are the improvements to the New AROFLY generation,ELITE,LINK,and XELITE.
The AROFLY team,designed a highly sensitive pressure sensor with a MCU in the AROFLY sensor for the upgraded algorithm and filtering program,to remove interference from road conditions.
Designed a highly sensitive altimeter and GPS in the hardware,for quick response on slopes and gradient changes,to correct algorithm mode for data output.
Included additional sensors in the system as sensor fusion to collect more raw data of road condition and pedaling status,to assist the algorithm with quick & correct data output.
Integrated the system with more functions and riding data on the products
The “LINK”version,now offers a very affordable,Bluetooth & ANT + connectivity to other Bike Computers
The “ELITE”& XELITE versions now offers a very affordable bike computer,with all the features and benefits of the more expensive bike computers in the market.
These new improvements will add more accuracy,consistency and flexibility to the operation of the AROFLY new generation,ELITE,LINK and XELITE.
The new product are estimated to launch June/July 2019.
Thank you for your reading.
Team Arofly
Arofly Outdoor:
Arofly Indoor:
Arofly ELITE OPERATION:
Arofly ELITE INSTALLATION: https://youtu.be/btI-EBrjfi8
AROFLY
https://youtu.be/ZhMn7XAGYhk
Arofly Link, X-Elite
2019/5/6
Hi all,
The AROFLY team has dedicated several experiments and tests to design the customized Sensors,Hardware and Integration of the exclusive software for the AROFLY system.
AROFLY’S dynamic air pressure system,is totally a”New Invention”. All the technology in hardware,software and algorithms had to be created from Zero. There is no similar technology and system of a power meter in the market to compare or learn from.
By accumulating information from several valuable experiments and tests,the AROFLY team identified the core value for the AROFLY power meter system.
After two full years of hard and dedicated work on more advanced technology,the AROFLY team developed,the ELITE,LINK and XELITE in 2019.
The first AROFLY model was designed in 2017. The AROFLY Sensor,worked in conjunction with a Smart Phone APP,using GPS for altitude and gradient.
The slow response of the required data from the Smart Phone was not good enough for the AROFLY sensor to identify the slope changes,causing late data output,thus confusing the cyclist.
We valued all the positive and negative feedback from the market,we listened to our customers very seriously. This feedback was discussed and has driven the AROFLY team to carry out more research,development and evaluation,to complete a new generation for AROFLY.
The following are the improvements to the New AROFLY generation,ELITE,LINK,and XELITE.
The AROFLY team,designed a highly sensitive pressure sensor with a MCU in the AROFLY sensor for the upgraded algorithm and filtering program,to remove interference from road conditions.
Designed a highly sensitive altimeter and GPS in the hardware,for quick response on slopes and gradient changes,to correct algorithm mode for data output.
Included additional sensors in the system as sensor fusion to collect more raw data of road condition and pedaling status,to assist the algorithm with quick & correct data output.
Integrated the system with more functions and riding data on the products
The “LINK”version,now offers a very affordable,Bluetooth & ANT + connectivity to other Bike Computers
The “ELITE”& XELITE versions now offers a very affordable bike computer,with all the features and benefits of the more expensive bike computers in the market.
These new improvements will add more accuracy,consistency and flexibility to the operation of the AROFLY new generation,ELITE,LINK and XELITE.
The new product are estimated to launch June/July 2019.
Thank you for your reading.
Team Arofly
Arofly Outdoor:
Arofly Indoor:
Arofly ELITE OPERATION:
Arofly ELITE INSTALLATION: https://youtu.be/btI-EBrjfi8
AROFLY
https://youtu.be/ZhMn7XAGYhk
OK George, please show us
OK George, please show us graphs of simultaneous readings from an Arofly and a strain gauge powermeter on the same bicycle over a hilly course. (I wouldn’t expect precise agreement, but would expect the integrated readings over the entire course to be close.)
janusz0 wrote:
Like the ones in this review — https://road.cc/content/review/227916-arofly-power-meter — which appear to indicate that the basic concept doesn’t work at all?
rkemb wrote:
Thanks for the reminder rkemb. I’d forgotten about that article! It doesn’t look good, but maybe George can point us at an up to date comparison.