RE Friction

[Kenneth Sloane]

                      Subject:                              Time:  2:36 PM
  OFFICE MEMO         RE Friction                           Date:  8/4/95

                     -------STEVE BRADY WROTE-----------
>It's important, however, to remember that laws which
>apply to a brick on a table may not be the same laws which govern a
>complex and dynamic scenario such as a piano action in motion. To assume
>that they do seems incredibly naive to me.

        ---------DAN SQUIRE RESPONDED-----------
Do the laws of nature change from one system to another?  Can understanding
how a brick slides on a table provide insight on how music wire will side
over its termination points?  Can it provide insight on all points of
friction within the piano?  Assuming that the piano is such a "complex and
dynamic" structure where would be a better place to start the process of
understanding?  Yes, you can call me naive if you wish, but I will still
strive to understand the beautiful dynamics of the piano.

Nature first made things in her own way, and then made human reason skillful
enough to be able to understand some of her secrets, but only by hard work.
                                          - Galileo Galilei

             ----------------M Y RESPONSE-------------
The laws of nature do not change from one system to another. However, our
methods of analysis with pianos sometimes introduce conditions into that
analysis that do not exist when the piano is being played as a musical
instrument. For example, when we use touch weights to measure friction in an
action, the key moves slowly and the knuckle stays, more or less, continuously
in contact with the jack and repetition lever. This is also true with the
wippen/capstan bearing.  I believe that it is generally considered that this
does not occur when the piano is played. After initial compression of the
knuckle against the jack/rep lever and the capstan against the wip bearing,
the hammer assembly gets moving. The inertia of the moving hammer assembly
then helps to carry the assembly to the string. So, is there more friction
during that "period of compression" (as opposed to when we use touch weights)
and less when the inertia "takes over"? Even more confusing is how the hell we
would begin to measure these "varying" friction levels when playing.

Ken Sloane, Oberlin Conservatory