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Power meter for a turbo?

pmorgan1pmorgan1 Posts: 173
Hi,

Appreciate if anyone could recommend subj please (hopefully the one that costs less than the bike itself). I would have thought that, for instance, on my "single speed" turbo the power is simply a function of the speed (which I can read off the computer)... Shouldn't be too difficult to convert one into another?

BTW - what makes the usual power meters that expensive - design, materials, etc?

Thanks.

Posts

  • GavHGavH Posts: 933
    pmorgan1 wrote:
    BTW - what makes the usual power meters that expensive - design, materials, etc?

    Probably the fact that almost everyone wants one!

    In all seriousness though, from what I can gather, the strain guages that measure the forces which in turn become your 'power' are cheap as chips. Hubs/cranks/bottom bracket/pedals don't cost the earth either hence the cost must come from the R&D associated with making these things. Just my 2p etc...
  • amaferangaamaferanga Posts: 6,789
    Cheapest route to reliable power measurement is probably a used Powertap. The older wired versions are the cheapest.

    Inferring power is a complete waste of time so you either need to buy a power meter or just forget about power and use HR and/or perceived exertion.
    More problems but still living....
  • 5858558585 Posts: 207
    If you just want power measurement on the turbo this might be the cheapest: http://www.chainreactioncycles.com/Mode ... delID=9756

    A power meter needs to be accurate, have good repeatability, be weather proof, light, durable etc, If you think you can produce and market one for less than the base power-tap model then you will be a rich man. Can't be that hard, eh? :wink:
  • pmorgan1pmorgan1 Posts: 173
    58, thanks for the link, the turbo looks good and is reasonably priced indeed.

    I think my fluid turbo can pull more progressive power (however my beef is I don't know what the power or an equivalent gradient is! :)

    Re: powertapping, marketing is always hard, however not impossible. Where do we start? A piezoelectric sensor translating tension into power (<1$ :), bluetooth transmitter (<5$), iPhone app (priceless :) ?
  • chrisw12chrisw12 Posts: 1,246
    pmorgan1 wrote:
    Hi,

    simply a function of the speed (which I can read off the computer)... Shouldn't be too difficult to convert one into another?

    But unfortunately it's (power) also a function of rolling resistance and losses in the turbo (neither of which are constants)
  • yes speed and power are tightly correlated on a turbo, esp a magnetic one where there is a linear relationship. The problem is without calibration there is no way to know the association between actual speed and power.
  • liversedgeliversedge Posts: 1,002
    The new lemond turbo does away with tyre press-on so translating speed to power should be easy and reliable.

    I also hear that the air braking and big fly-wheel make for a road like feel.

    http://www.pinkbike.com/news/lemond-tra ... -2010.html
    --
    Obsessed is just a word elephants use to describe the dedicated. http://markliversedge.blogspot.com
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