flagpoling or killing pin-block?

[Marcel Carey]

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Re: flagpoling or killing pin-block?comments interspread below for
discussion purposes:

Marcel
  -----Original Message-----
  From: owner-pianotech@ptg.org [mailto:owner-pianotech@ptg.org]On Behalf Of
Jon Rhee
  Sent: 30 novembre, 2001 12:37
  To: pianotech@ptg.org
  Subject: Re: flagpoling or killing pin-block?


    My interpretation of the  whole issue of bending of the pin is this:
The tuning the pin flexes upwards while one raises the pitch whether one
realizes it or not.
    "Only if you use the lever between 9 and 11 O'clock"
       This is due to the many forces  acting on the pin during the raising
of the pitch.   At rest there is the string tension pulling downwards on the
pin, not only a rotational tension but a vertical tension.  The rotational
force (torque) is balanced by the static friction between the pin block and
the pin.  The downward force is balanced by the strength of the elasticity
of the  steel in the tuning pin. The pin IS flexed down  while there is
string tension on it.
    " Considering the forces in action (distance from block or bushing,
diameter of tuning pin and string tension) I wonder how much the tension
could deflect the pin (In other words, I don't think so)."

    The tricky part is understanding how the tuning lever is acting on the
pin.  When the string moves during the raising of pitch  the forces are no
longer in balance.  At the very least  (if the force of the tuning hammer is
imagined as a person pulling  on another string wrapped around the pin the
other direction) , the rotational  friction between block and pin and the
tension of the string have been overcome.  If the string is moving (raising
pitch) has the vertical tension  also been overcome?    The solution is
complicated by the fact that the force from the tuning lever is off center
because it has one handle.  Which direction is it being pulled from? Usually
the from right but the variations in lever and arm position could cause
upwards or downwards forces to act on the pin. The technicians arm position
may also not be in line with the rotation of the pin (though it should be as
close as possible) which is probably why this is more of a vertical piano
problem than with a grand.  Ever try to break a lug nut free with a tire
iron and have it come flying off into the ground?  That's because (like the
tuning lever) the forces are not applied purely as torque or tangentially to
the pin.
    "  This is why I would never use the long tuning tips that I've seen on
the market "

    The school of thought of "tweaking " the pin back down into its resting
position believes that the pin has been relaxed from its flexed position
during the tuning.  A third hand to play the note and a T handled tuning
wrench with the other two hands on it is what we need.  Or a physics
(mechanics) major.

    Sorry for the lengthy diatribe.

    Jon Rhee
    Weymouth, MA




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