why are power meters soooo expensive?

craigw99
craigw99 Posts: 224
edited December 2012 in MTB general
the title really says it all - down to limited knowlege as far as i can tell are they not just a couple of strain gagues a battery and a wireless transmitter if so then why so much?
opinions are worth exactly what you pay for them ;-)
2012 boardman team F/S tarting has begun..
1992 cannondale m1000 still going just
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Comments

  • schweiz
    schweiz Posts: 1,644
    Accuracy (which has a direct impact on allowable production tolerances of components) and amortisation of development costs.

    Think how many people own a bike
    Then think how many of those people own a 'good' bike
    Then think how many of those people train rather than just ride
    Then think how many of those people train with a power meter
    Then think how many different products are on the market

    The reality is that there's not that many people with power meters and of those that have one, there's a realistic choice of half a dozen products.

    I'd hate to think how much Garmin have invested in the Vector pedal and it's still not on the market due to it not being able to produce reliable and consistant power figures!
  • cooldad
    cooldad Posts: 32,599
    As someone who likes to ride bicycles in the dirt, who cares?
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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  • craigw99
    craigw99 Posts: 224
    thanks good answer - i see them getting hyped everywhere and im like they are how much :shock:
    opinions are worth exactly what you pay for them ;-)
    2012 boardman team F/S tarting has begun..
    1992 cannondale m1000 still going just
  • bennett_346
    bennett_346 Posts: 5,029
    Why would anyone want a screen that displays an arbitrary number? May as well have someone throw a pack of cards at you and see which number hurts the most (it would be about as much use).
  • Why would anyone want a screen that displays an arbitrary number? May as well have someone throw a pack of cards at you and see which number hurts the most (it would be about as much use).

    The numbers do have their use, you can measure performance if you are training hard and develop power baselines for different terrain.

    That said, I don't think 95% of people have any use for one.
  • njee20
    njee20 Posts: 9,613
    Why would anyone want a screen that displays an arbitrary number? May as well have someone throw a pack of cards at you and see which number hurts the most (it would be about as much use).

    Do you mean that in reference to power generally, or an inaccurate power meter?

    If the former then you don't really understand power do you? :?

    Stages Cycling are doing a $600 power meter, from January, but only for sale in the US, pain, as I fancy changing my PowerTap.
  • bennett_346
    bennett_346 Posts: 5,029
    njee20 wrote:
    Why would anyone want a screen that displays an arbitrary number? May as well have someone throw a pack of cards at you and see which number hurts the most (it would be about as much use).

    Do you mean that in reference to power generally, or an inaccurate power meter?

    If the former then you don't really understand power do you? :?

    Stages Cycling are doing a $600 power meter, from January, but only for sale in the US, pain, as I fancy changing my PowerTap.
    I meant an innacurate power meter would be as useful as a chocolate teapot, hence they're all expensive.

    But i also don't think many people need a power meter.
  • njee20
    njee20 Posts: 9,613
    Aah, I see! No one needs one. They're a useful training aid.
  • ilovedirt
    ilovedirt Posts: 5,798
    I don't know much about the workings of these power meters (didn't really know they existed), but as an electronic engineering student, we're constantly being told that being an engineer is all about compromise. Do you really NEED a really expensive circuit, or can you get away with a cheap one that does the job? I'm guessing if these are a fairly new technology, then they'll have some fairly complex digital circuitry inside them, which isn't cheap to begin with. The more accurate you want something to be, generally the more work goes into designing it, and the more components go into it, all of this incurs cost, particularly the man-hours. I haven't looked at anything any where near as complex as these things, but as with all new technologies, it'll start off expensive and then get cheaper as certain components get cheaper to produce and these things become easier to design.
    Production Privee Shan

    B'Twin Triban 5
  • For your average rider/racer who wants training zones a HR monitor will do the job perfectly and at a fraction of the cost.
    Zesty 514 Scott Scale 20 GT Expert HalfwayupMTB
  • i STILL have no idea what a power meter is.
  • Yep... mainly because I don't really care.
  • bennett_346
    bennett_346 Posts: 5,029
    Why complain then?
  • I wasn't complaining.. just pointing out I didn't know what it was, since the last thread about this mystical training thing baffled me.

    If you can justify the cost for something, you can't really need it that badly imo.
  • njee20
    njee20 Posts: 9,613
    They're not new - Lemond played with one in the late 80s. They're getting more affordable as new ones come out, and they're making inroads into MTB, and BMX. But they're not new.
  • cooldad
    cooldad Posts: 32,599
    i STILL have no idea what a power meter is.
    They're obviously for racing snakes not fat bastards.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

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  • cooldad wrote:
    i STILL have no idea what a power meter is.
    They're obviously for racing snakes not fat bastards.

    This may be the reason, however I did think they were more of a lycra brigade thing.
  • njee20
    njee20 Posts: 9,613
    They're an expensive training aid. If you're not fussed by training and quantifying your fitness levels they're totally useless. If you are interested in that,they're great. As overweight weekend warriors it's unlikely, ergo they'll offer you nothing, and you should spend the money on beer, bacon and the latest tyres which will revolutionise your riding.
  • Can't you just quantify your fitness by comparing lap times around the same route...or by actually competing against others.

    free v $600. hmm.
  • njee20
    njee20 Posts: 9,613
    edited December 2012
    No, because changing bikes, weather, tyres, suspension set up etc all affect that. Other people isn't a constant metric, what if they're getting fitter, or less fit?

    A watt is a watt. Whether on an MTB in the alps, a BMX on the track or at a road race. Higher power:weight = fitter.

    Like I say, it's a training aid, if you don't train then it's of no interest.
  • cooldad
    cooldad Posts: 32,599
    njee20 wrote:
    They're an expensive training aid. If you're not fussed by training and quantifying your fitness levels they're totally useless. If you are interested in that,they're great. As overweight weekend warriors it's unlikely, ergo they'll offer you nothing, and you should spend the money on beer, bacon and the latest tyres which will revolutionise your riding.
    You got me there.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • njee20 wrote:
    No, because changing bikes, weather, tyres, suspension set up etc all affect that. Other people isn't a constant metric, what if they're getting fitter, or less fit?

    Surely though, 'power output' is also affected by this?

    (i'm not not trying to seem argumentative, genuine questions now lol).
  • ilovedirt
    ilovedirt Posts: 5,798
    njee20 wrote:
    No, because changing bikes, weather, tyres, suspension set up etc all affect that. Other people isn't a constant metric, what if they're getting fitter, or less fit?

    Surely though, 'power output' is also affected by this?

    (i'm not not trying to seem argumentative, genuine questions now lol).
    Nope. You're confusing power and work. Two totally different things.
    Production Privee Shan

    B'Twin Triban 5
  • cooldad
    cooldad Posts: 32,599
    Those with power do the least work. Simple.
    I don't do smileys.

    There is no secret ingredient - Kung Fu Panda

    London Calling on Facebook

    Parktools
  • njee20
    njee20 Posts: 9,613
    Surely though, 'power output' is also affected by this?

    Nope, as above its absolute. If you do a ride and average 200 watts, then repeat it at 220 watts you've got fitter (or gained loads of weight), even if one ride was on a TT bike with a 50mph tail wind and the other was on a 16" kids bike! Hence why it's the gold standard for training. Even HR doesn't mean all that much, a decrease in HR could be increased fitness, overtraining or illness.
  • ok.. so I assume that things like Strava use calculations such as Power = (weight x height risen)/time
    Do the powermeters measure force and convert that to power (using velocity) or?

    Gold standard stuff is for top level though, not really the average forum user... so I'm not surprised it costs a lot!
  • scarbs85
    scarbs85 Posts: 170
    A watt is a measurement of energy and time (joule / second).

    Consider yourself as an engine. The watts you can produce is how much power you can put through any given bike. If your putting that power through any given bike in any given conditions, the time, distance etc will be different, but the watts will always be the same.

    Think fitting the same engine into a hummer and a mini cooper. The engine still produces the same power, but will drive one vehicle faster than the other.

    Edit// don't know what calculation Strava would use, but it would have to involve velocity as a flat trail still requires power.
  • njee20
    njee20 Posts: 9,613
    Yes Strava has a wild guess based on weight and speed, and it's just that!

    Power metres measure torque either through the hub or the crank, or the deflection of the crank against a known value in the case of the new Stages power meter, that means it only measures on the left though, and doubles the result for a total power output, so doesn't really work if you have an imbalance in legs. But as NM says, gold standard = pricey. Love mine though, even though I don't really use it to its full potential any more.
  • schweiz
    schweiz Posts: 1,644
    Strava use an algorithm that, amongst other things, takes into account rider weight, bike weight, height gain, distance, speed, an 'average' road surface coefficient of friction and an 'average' wind resistance. I have a power tap (i'm a roadie who has wandered onto the MTB forum) and the strava calculations are close for average speed (without actually checking, i'd say within 5-7 %). If it was particularly windy then it is way off. Strava can also give stupidly high max power values. Most power meters claim to be accurate to +/- 3%.

    Also, in response to previous comments strain gauges are nothing new but they can be a PITA to get reliable, repeatable data from. I worked on an aircraft that had them installed in various positions to help calculate the fatigue life if the airframe. In the end the stress and reliability Engineers gave up trying to get any meaningful data out of some of the gauges.