10 gram Power Meter???

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There is a company that says that they have invented a power meter that weighs 10 grams.  The company is Arofly and it says that it is going to sell, in February 2017, a power meter that is the smallest and measures power, cadence and speed.  Pretty good,  it seems.

The thing that is hard to understand is that the power meter is just a valve cover cap.  Yep, a small thing you screw to the top of you tire inner tube valve.   It is hard to grasp how that could possible measure the power that a rider is putting into their pedals, right?

I don’t get it.  But I’m not smart enough to say that it is impossible.  There are lots of inventions that didn’t seem possible initially that become reality.

According to Arofly’s website, their technology is “a patented air pressure differential technology based on the pitottube design, from the F-117 combat aircraft.”  

I have no idea what the pitot tube design is.  I’m going to look it up right after finishing this. Okay, I lied, I looked it up.  And I still don’t know what it is.  It might take a little more time.  I think it is a little complicated.

The power meter, if you pre-order, costs $129.  And, for that price, it comes with a holder for your phone.  That is very fair and, by far, the least expensive power meter on the market today.  So, it will be the smallest, lightest and cheapest.  Appealing.

Like I said above, just because it seems doubtful that this might work, doesn’t mean it won’t.  I remember when Jim Gentes walked up to me at Interbike and showed me a styrofoam prototype helmet. He asked me if I would be interested in wearing one.  I said sure, thinking to myself that there is now way that piece of styrofoam would meet the standards to qualify to be a safe helmet.

Jim made the helmet and that is when Giro helmets was founded.  Pretty incredible for 31 years ago.  Revolutionary advance.

Anyway, it will be interesting to see if this works.  I’d love to get my hands on one.  I hope to be riding outside pretty soon and would be happy to test one and give a real review.  Until then, we’ll just hope.

It's the little valve cap below the boxes.

It’s the little woven valve cap below the boxes.

27 thoughts on “10 gram Power Meter???

  1. KrakatoaEastofJava

    So long as it gives YOU consistent readings from day-2-day and effort-2-effort, that’s really all that matters. Considering that even two high-priced SRMs will probably give the same effort two separate wattage scores. Unless you really care about telling your friends what your wattage scores are, I wouldn’t worry.

  2. kmak

    Seems like a scam to me. A pitot tube measures the velocity of a moving fluid. No idea how they could do that in such a sized device with such variance in relative velocity of the air moving at the valve stem.

  3. Joe Clement

    I’m not a good engineer, and it still looks fishy. Pretty sure DC Rainmaker will do one of his awesome reviews. If someone wants to buy me one, I’ll compare it to my Power to and 4iiii/stages.

  4. mks

    As mentioned above, pitot tubes measure the velocity of a moving fluid. They’ve been used a long time in marine applications as part of the way to tell boat speed. In that application they were “kind of” accurate. They’ve been first replaced by “paddle wheel” type sensors and now replaced by GPS technology for telling speed in a boat. For a bike it will give “reasonable” accuracy for speed, etc. but the power will be generated by an “algorithm” so an estimation at best. Maybe that’s better than nothing……. but I’d challenge an experienced cyclist using “perceived effort” might do just as well. The need to have your smart phone on your handlebar is a total deal breaker to me. Like many things in life, you get what you pay for.

  5. numbnuts

    like to see the electronics in that… power = amps x volts… so if you can get the amperage and volts, you can probably estimate the wattage to some degree of error.
    microprocessor technology is getting smaller and smaller and system on a chip is as well ( en.wikipedia.org/wiki/System_on_a_chip) .
    Considering one can embed an accelerometer within a chip or FPGA/ASIC now a days…
    ex: http://www.sparkfun.com/products/10937

    I’d still like to see the schematics/chipset of that thing. I suspect its using all active components rather than passive components, passive RLC circuits are big… but, active technologies are bringing the size down considerably.
    Are they reliable? (ie take them out in the cold) maybe not so much so…
    Are they durable (ie bang the crap out of them) maybe not so much so…
    Are they accurate (ie how much accuracy do you really need, that’s like people being real weight weenies, go have a crap before you race… 500 grams saved!)

    I’d buy one to try it out, I definitely wouldn’t by a 2000 dollar power meter…. I like cycling, but not that much… that’s kind of foolishness really. A cheap rough estimate power meter would suffice though, some place around 200 bucks sounds reasonable.

  6. numbnuts

    opps, it seems to be based on velocity estimates… so

    P = W/t W=FΔx W=ΔKE ΔKE=mvf2-mfi2

    I suspect the value would be an estimate, but who needs to be exact when overall one is really looking at the average wattage over a given time period. If you were measuring some nano-device, then I’d say be accurate… but, you’re measuring a human body output over a time period. Averages should be alright.

    I’d buy one, I ain’t spending 2000 bucks on some power meter that’s for sure… waste of money.

  7. Ted

    A pitot tube is a part that sticks out of any plane – usually pointing forward – the difference in air pressure helps the establish air speed of a plane (named after the inventor). Hope these guys made this to fit presta valves – wouldn’t it be a bonehead move if they just made it for shraeder vales (looking at the photo)

  8. Robo

    I hate to say this, but does anyone else see the irony in Steve’s comment re: the “revolutionary advance” of the Styrofoam helmet?

  9. Steve Tilford Post author

    Robo-It was revolutionary compared to what was available at the time. You could wear a Bell V1, Skidlid, or a few other off-brands. There would have been no way to get European pros to convert to the hard helmet rule without the weight reduction of the styrofoam helmet.

  10. numbnuts

    just checked their website… that’s old technology… many aircraft use that system to determine velocity.


    originates from aerospace technology, and is based on the pitottube design


    definitely based on velocity…
    I worked on this aircraft (submarine hunter aircraft) when at Lockheed many years back (90s) https://en.wikipedia.org/wiki/Lockheed_CP-140_Aurora it had many of those… all sorts of calculations done with that on the AN/UYK system…

    I was expecting something way way more complex.

    Anyhow, for power, it doesn’t need to be that accurate. Not as though you are measuring nano meter movements or small objects… we’re merely measuring a human body over some given large period of time. Who’s really concerned about measuring power over every inch or foot for that matter…thus, we’re mostly interested in rough estimates of power.

    This device should suffice. I ain’t spending 2000 bucks for an over designed power meter… waste of cash.

  11. old and slow

    Agree with the message but Skid-Lid wasn’t really valid any more by the time that the USCF made “Hardshell helmets” mandatory in 1985, I think?

    They were pretty much eviscerated by a single review in Bicycling circa 1983 or maybe a year earlier and would have never passed Snell or ANSI without a major redesign.

  12. conrad

    Why are people trying so hard to make an inherently fun activity (riding a bike, remember?)- annoying. If you want to be fast, you have to put the miles in. One might think that staring at a screen with semi pointless numbers would make it more difficult to do that. Or how about the new shades from Oakley. How far can you go before you want to put a bullet in your head.

  13. KrakatoaEastofJava

    Why? Americans are obsessed with measuring their cocks (and comparing numbers). Same reason they’d choose 10-gram carbon vs. 13-gram aluminum. Three grams of bragging rights.

  14. JB

    I’m often glad that I just ride for fun/exercise. 2×8 and steel still work great!

    As for racers and those that care about power meters: go for it! , as long as it’s still fun…

  15. Chris Froome

    Hey Cycling Fans and Mr. Tilford! It’s me the one and only Champion of the Universe Froomey- Absolute BadAss King of the entire History of Cycling Forever Period! Disclaimer- Sir Braillie made me say that! That’s what I calls him now, I do, I DO! Team Sky ™ is gonna rule for a decade, Bros! Headed Down Unda for some killer training blocs and we are shipping the Team Pie In The Sky RV Down Under so I can sleep and dope in private luxury – UCI can’t touch us during the rolling mobile training season yo! Bloody clandestine- and we also have survellience and even a guy tailing Durian Rider. More on my Adeliade training later, but first I gotta clear the air about my old Frenemy nemesissy pal-o-mine Wiggo and his TUE fiasco. Look mates, this is a very simple situation: Sir Wiggo took very low doses of these steroids only to treat his legitimate allergies and such… there, I said it. That’s it. End of story. That’s what I’d be saying with my publicist and what not. I mean Sir Davey Wavey is beside himself! If this old tattooed hipster sticks around until Tokyo it’s just like Sir Lancelot’s comeback! Someone will eventually slay the dragon! Then we all go down! When we at British Cycling / Team Sky say, “He’ll always have a place here,” of course what we are really saying is- get the fuck out Wiggins- it’s time for you to retire.

  16. Gen X'cited

    Before our home boy Jim Gentes re-invented the helmet we used to carve out enough foam in a Bell V1 pro helmet xs size to fit with a Dremel tool . Drove Les Ernest mad.

  17. Choppy Warburton

    Those helmets work amazing wonders of protection and self-preservation!!!!

    As long as one wears them.

  18. PB Anders

    No pitot tube. It uses a solid state FBM320 barometeric pressure sensor for the tire pressure measurements, and uses a Bosch three-axis accelerometer for wheel speed measurements. From charts on their web site, looks like they’re determining cadence from the frequency of the pressure variations, and pedal force from the amplitude. No idea of how it’s calibrated. Apps are available now for Android and iPhone, but the info they need is insufficient for what you’d need to have to do a cross-calibration with a force balance method. Can’t say it’s clear how or if this works, but it’s not just a hoax from what I can see. Their “real world” chart looks awfully messy to me, not clear that cadence and power can be extracted with that kind of data.


    After several years of research, Technology has allowed inventors to expand their imagination and smartness to achieve the world’s smallest and most affordable power meter.”AROFLY. only 10 grams in weight and offers everything one needs in a power meter. . Accuracy is important, but to what extent. Really, there is nothing out there which will be 100% accurate. We can live with 90% to 95% accuracy.

    Go back 30 years ,the smallest Mobile Phone weighed 23 lbs and over ………Today it weighs less than one lb .and offers more functions.

    Its only natural for skepticism. That is OK.The proof in the pudding is to test one yourself.
    Every cyclist deserves a chance to reach their optimal potential, hence the AROFLY was designed to be most affordable.

    Visit http://www.aroflybike.com Launch Feb 2017. First batch of shipment will be going out Mid Feb 2017 .

    Have fun


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