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  • Coefficients for actual spring-mass-damper system

    From Christopher Howard@christopher@librehacker.com to sci.physics on Thu Dec 18 15:18:18 2025
    From Newsgroup: sci.physics

    Hi, I am playing around with model spring-mass-damper systems on my
    analog computer. I was wanting, for comparison purposes, to make an
    actual system with a spring and a mass. But I am a little confused how I
    would know what the damping coefficient and spring coefficient is for
    any given spring, as that doesn't seem to be listed for any springs I
    can purchase on the Internet. Is there some catalog of springs out there
    that lists those coefficients, or a way to calculate them from some
    other listed parameter, or a practical way to measure them?
    --
    Christopher Howard
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  • From John Hasler@john@sugarbit.com to sci.physics on Thu Dec 18 19:29:33 2025
    From Newsgroup: sci.physics

    Spring catalogs will list nominal spring constants but there's lots of variation. Better to measure your particular spring. As far as I know
    nobody publishes damping coefficients. You could compute them from the
    spring dimensions and the material properties but I don't think that
    would be very accurate.

    You can measure the spring constant by measuring the spring, applying a
    known force, and measuring again. The spring constant is the force
    divided by the change in length.

    Knowing the spring constant you can then hang a mass from it, start it oscillating, measure the period and decay time constant, and calculate
    the damping coefficient. That way you would be including the effects of
    the air. Hang it from something rigid and massive, of course.
    --
    John Hasler
    john@sugarbit.com
    Dancing Horse Hill
    Elmwood, WI USA
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  • From ram@ram@zedat.fu-berlin.de (Stefan Ram) to sci.physics on Fri Dec 19 08:43:28 2025
    From Newsgroup: sci.physics

    John Hasler <john@sugarbit.com> wrote or quoted:
    You can measure the spring constant by measuring the spring, applying a
    known force, and measuring again. The spring constant is the force
    divided by the change in length.

    Knowing the spring constant you can then hang a mass from it, start it >oscillating, measure the period and decay time constant, and calculate
    the damping coefficient. That way you would be including the effects of
    the air. Hang it from something rigid and massive, of course.

    Yeah, that makes sense.

    I'm probably overthinking this kind of stuff. My first idea was to
    record the curve and fit it to figure out those parameters.

    But how would you even record a curve? You could film the
    oscillation with a smartphone on a tripod. After that, you can
    grab the individual frames using ffmpeg. The data's pretty easy to
    analyze automatically if you highlight the moving part of the spring
    - like by sticking a small light on it and filming in the dark.

    Possible expression for fitting: a exp( -bt )cos( ct + d )+ e.

    Possible software for fitting: Python (SciPy + NumPy + Matplotlib),
    MATLAB, LabVIEW, or GraphPad Prism.


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  • From John Hasler@john@sugarbit.com to sci.physics on Fri Dec 19 08:17:42 2025
    From Newsgroup: sci.physics

    https://en.wikipedia.org/wiki/Harmonic_oscillator#Damped_harmonic_oscillator

    https://en.wikipedia.org/wiki/Mass-spring-damper_model
    --
    John Hasler
    john@sugarbit.com
    Dancing Horse Hill
    Elmwood, WI USA
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