Grist for the Mill

[Michael Gamble]

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Good point there Alan. I am sure you are right! Which is why we use CA =
to tighten up those pins - to STOP them from revolving =
counter-clock-wise. I don't know about you, but I often find that =
subsequent to replacing a pair of metals (due to breakage etc.) the new =
string stays much better in tune. Though what that has to do with this =
subject I'm not sure. Just food for thought.
Regards
Michael G.(UK)
  ----- Original Message -----=20
  From: alan and carolyn barnard=20
  To: Pianotech=20
  Sent: Thursday, May 12, 2005 1:50 AM
  Subject: Grist for the Mill



  We recently had a long dialog on here about the actual changes in a =
piano that has gone flat. There was much poo-pooing (can we say that on =
TV?) from some folks of the notion that tuning pins turned =
counter-clockwise when pianos go flat. Their arguments were logical and =
some folks even produced mathematics to demonstrated that pin reversal =
is unlikely.

  BUT ...

  I was thinking about this on my way home from PTG chapter meeting (2.5 =
hr drive) and came up with a little point of logic which suggests that =
the pins MUST move. See what you think ...

  Virtually all pianos go flat over longish time periods and certainly =
are found flat more often than sharp if you go through a whole cycle of =
season changes, i.e., an annual tuning. When we bring a flat string up =
to pitch, it tends to increase the width of the coil slightly every time =
we turn the pin. If the pin is turned one full revolution--360 =
degrees--over years of tuning, this would add the thickness dimension of =
the wire to the overall coil width and one full wire wrap to the number =
of coils.=20

  You with me?

  So let's take a hypothetical piano string--say a very stable 1905 =
Howard upright A4 middle string--that has averaged (let's be =
conservative...) falling flat enough that a 7.5 degree turn of the pin =
was required each year to bring it up to pitch. Now 7.5 degrees is a =
fairly small annual adjustment, just a little tweak, actually. Ce n'est =
pas? It's only 1/6 if a quarter turn.

  So, between 1905 and 2005, we have turned that string's pin 100 X 7.5 =
=3D 750 degrees, more than two full turns.

  How many old pianos do we run into that have five or more coils on the =
pin? I never noticed any.  In fact, most seem to have the original 3 =
coils standing about as far from the plate as the day it was =
strung--unless someone has hammered them in, in which case it's still =
only about 3 coils!

  Pause ... thinkin on that?

  Now strings must become ever so slightly thinner as they stretch, =
especially in the earlier years. So, for the string to produce the same =
pitch, the string tension required would be ever so slightly less over =
time. This would have a very slight mitigating effect on the thought =
puzzle proposed above. But nowhere near enough to explain 100 years of =
flatness, methinks. And ven if the string is stretching, you would still =
be adding linear length to the coil every time. =20

  I believe, in fact, that about a 30 annual correction, or more, would =
be very common.  Think about your own real-world, real-piano experience. =
Visualize pulling your tuning hammer through a 30 degree arc, i.e., 1/3 =
of a quarter turn. That's still a pretty darned small once-a-year =
adjustment. So, I think my estimates here have been very, very =
conservative.

  Anyway, at 30 degrees the piano would have to have a total of 8+ full =
coils on every pin if the pin never turned backward.

  Your turn or, as we used to say in Viet Nam .... I n c o m i n g ! ! ! =


  Alan Barnard
  Hunkered in the Bunker in Salem, MO


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