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OT?...How does gravity vary?

Discussion in 'Electronic Design' started by Roy Hammond, Feb 10, 2007.

  1. Roy Hammond

    Roy Hammond Guest

    Pendulum clocks - the usual electronic movement type (battery feedback
    pulses solenoid when magnet on pendulum passes by).

    My experience with these movements is that they are somewhat delicate: you
    have to carefully adjust the clock movement vertically and horizontally
    until the pendulum swings reliably.

    However after running for several hours, sometimes the pendulum stops.
    I think that I've ruled out the battery as the guilty party.
    That set me to wondering: does gravity vary? If so, what are its
    characteristics? Could gravity changes account for the pendulum stopping?
     
  2. Try a horizontal pendulum.
    It would be independent of gravity.


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  3. Yes. Sometimes the heavy gravity sits as a layer on top of the light gravity
    and holds it down causing a gravity inversion layer.
     
  4. Gareth

    Gareth Guest

    Gravity varies a little bit due to the effects of the sun and moon
    (which is why we have tides) but I doubt that this is the reason for
    your clock stopping.

    Gravity also decreases with increased altitude, and is slightly
    different at different places on the Earth's surface due to different
    local geology.

    A gravitational force of attraction exists between any objects with
    mass, so in theory moving any object would cause a change in the total
    gravitational force seen by the pendulum. However, the Earth is very
    large and close, so most other things will not cause any detectable change.

    --
     
  5. There appears to be an accumulation of the heavy gravity underneath my
    bathroom scale.
     
  6. I don't think variations in gravity are stopping your clock. I have one
    that has been running on one AA battery for about 2 years.

    The pendulum needs to be aligned not only in the lateral plane (side to
    side so that it swings equally to either side of the solenoid
    mechanism), it needs to be aligned fore and aft so that the pendulum's
    bearing (usually some sort of blade or wedge shape) makes contact with
    its rest with minimal friction.
     
  7. And when teenage boys watch porn the reverse seems to happen in their pants!
     
  8. Robert Baer

    Robert Baer Guest

    Nope! No observable reason for it to stop other than dirt accumulated
    in the bearings due to (too much) oil.
    The force of gravity changes with locale; known to be stronger near
    large deposits of iron.
    Extremely doubtful of local "modulations", and the variations
    mentioned above are very small.
     
  9. Robert Baer

    Robert Baer Guest

    As the hippy would say, "Heavy, man!".
     
  10. Hmm. I thought that was due to the gravitational attraction to
    satellites passing overhead.
     
  11. Guest

     
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