Advertisement
If you have a new account but are having problems posting or verifying your account, please email us on hello@boards.ie for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact hello@boards.ie

Power meter readings

Options
  • 05-12-2014 9:12am
    #1
    maesrichard1
    Registered Users Posts: 67 ✭✭


    Should a power meter read out some wattage if its suspended on a bike stand?


Comments

  • Options
    #2
    godtabh
    Moderators, Science, Health & Environment Moderators Posts: 23,204 Mod ✭✭✭✭godtabh


    maesrichard1 wrote: »
    Should a power meter read out some wattage if its suspended on a bike stand?

    Why would it? Is there power being applied?


  • Options
    #3
    Idleater
    Registered Users Posts: 6,236 ✭✭✭Idleater


    maesrichard1 wrote: »
    Should a power meter read out some wattage if its suspended on a bike stand?

    Yes. Why wouldn't it?

    I guess it would be difficult to get a high power reading though, given the lack of residence.


  • Options
    #4
    Beasty
    Administrators, Social & Fun Moderators, Sports Moderators Posts: 75,544 Admin ✭✭✭✭✭Beasty


    What is the PM, and are you talking about when you apply force by turning the pedals? Some pedal systems only recognise power on one side for example so if you turn the other crank nothing will register


  • Options
    #5
    fat bloke
    Registered Users Posts: 5,822 ✭✭✭fat bloke


    If the back wheel is up in the air and you turn the pedals it will register power sure, but not much - a couple of watts maybe cos obviously the resistance is so low that it only takes minimum wattage to turn the wheel.


  • Options
    #6
    maesrichard1
    Registered Users Posts: 67 ✭✭maesrichard1


    Im turning the pedals obviously. Stages PM. Good point beasty, i was turning the opposing crank arm to see if there was a reading. Thinking about it do, shouldnt it still register a an output?


  • Advertisement
  • Options
    #7
    Leroy42
    Registered Users Posts: 15,494 ✭✭✭✭Leroy42


    Stages will only return a reading if it senses pressure (force) in the left crank arm. So it won't register either power or cadence if doing a one-legged drill using the right leg for example


  • Options
    #8
    quozl
    Registered Users Posts: 3,308 ✭✭✭quozl


    maesrichard1 wrote: »
    Im turning the pedals obviously. Stages PM. Good point beasty, i was turning the opposing crank arm to see if there was a reading. Thinking about it do, shouldnt it still register a an output?

    If it was measuring force in the bottom bracket or something else that force is being applied to when applying it to the RHS crank arm.

    Stages measure force in the LHS crank arm - by measuring deflection of a stress meter inside the LHS crank arm. So, when turning the RHS crank arm, there's no force being applied to the LHS crank - except for a tiny bit of force being exerted on it by the bottom bracket forcing it to rotate along with the RHS crank.

    So no (neglible really) force = no deflection in the stress meter = no reading.


  • Options
    #9
    maesrichard1
    Registered Users Posts: 67 ✭✭maesrichard1


    quozl wrote: »
    If it was measuring force in the bottom bracket or something else that force is being applied to when applying it to the RHS crank arm.

    Stages measure force in the LHS crank arm - by measuring deflection of a stress meter inside the LHS crank arm. So, when turning the RHS crank arm, there's no force being applied to the LHS crank - except for a tiny bit of force being exerted on it by the bottom bracket forcing it to rotate along with the RHS crank.

    So no (neglible really) force = no deflection in the stress meter = no reading.

    Thats makes sense, I was thinking that centrifugal force might even produce some output but it obviously creates no deflection. Thanks.


Advertisement