Strings riding up (was Tuning stability)

Ed Sutton ed440@mindspring.com
Thu, 8 Apr 2004 21:45:17 -0400


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David-

No smiley face....more like a puzzle face....We tap for different =
reasons, and you're right that we need to be clear which reason we're =
tapping for.

Let me say that in practice, I'm pretty conservative, a slight push or =
very light tap in front of the pin is what I'll do if I feel the tone is =
fuzzy or beating.  Since it's part of Yamaha's service system, I'll do =
it on a new Yamaha.  In North Carolina we don't get the humidity =
problems talked about in this thread, except in a school that manages to =
get the music building into the low 20% range in winter.

And I'll tap the bends on a new string.  (I agree that with positive =
front and rear bearing and a flat bridge cap, the strings mostly seat =
themselves.)  I wonder if a push or tug against the bridge pin might be =
better than a tap.

On the other hand, this thread is asking some "deep" questions about =
string terminations.  A few years ago Ron and I discussed the =
possibility that bridges might work better if the caps were "hollowed" =
in the center.  I've not been motivated to do that much carving to test =
it. Fred's post reminded me of that, and set me to wondering if it could =
be accomplished by tapping, since we all agree that tapping can dent =
wood!  I will try it some time on a piano that's dead anyway.


The piano I'm restringing doesn't have serious curve to the bridge cap, =
so it really isn't a good candidate.  And that's something to smile =
about.  ;-)

Ed Sutton

 =20
  ----- Original Message -----=20
  From: David Skolnik=20
  To: College and University Technicians=20
  Sent: Thursday, April 08, 2004 9:00 PM
  Subject: Re: Strings riding up (was Tuning stability)


  Ed -

  No smiley faces, so I'm not sure if you're serious.  In case you are, =
here's what I think:

  At 06:02 PM 4/8/2004 -0400, you wrote:

    Fred wrote:
    > The real thrust of my musing was to consider
    > "going with the flow" in real world situations, where recapping or =
bridge
    > replacement aren't going to happen (at the particular moment). =
"Curvature
    > happens." Bridge tops crush at both sides more than on top. This =
is what we find
    > most often in the field.
    and
    >    BTW, if anyone reading really believes that  light tapping =
doesn't crush
    bridge
    > tops, take a piece of wire, lay it on a bit of exposed bridge top =
(above C8, eg)
    > and give it a tap with your brass rod. Even with your hammer =
shank. Give the
    > amount of tap that has "given focus to the tone," "allowed you to =
see the string
    > drop," "dropped pitch 4 cents," whatever. Then look at that bridge =
top. I
    > guarantee you'll see a little groove where none was before.

    So, this suggests we should be tapping the string in the middle!

    Not near the termination points, but along the arc in the center of =
the bridge
    cap.

  The question again is, "Why are you tapping?". What are you trying to =
accomplish?  If there IS some benefit to be gained, even temporarily, it =
will be had by tapping either pin or in front of the bridge, not on the =
bridge surface.  If there is some negative front bearing, tapping on the =
bridge  string segment will not seat the string.  The question still =
remains whether you want, or need to seat it, against its natural =
inclination to form a straight line. If you think seating improves the =
tone, what's the cause?



    If humidity change can crush the wood at the edges to make the =
curved string
    groove, then tapping forcefully in the middle should be able to =
deepen the groove
    in the middle so that the string is not lifted away from the =
termination points at
    the edges.

  I don't think you're visualizing the real configuration, but apart =
from that, if you could, in fact achieve string seating like that, what =
would you be doing to your downbearing? =20



    Would we then reach a point of stability as the crushed wood becomes =
harder, or
    would we just be starting the process over again, so that the next =
rise in
    humidity  would push the edge grooves still deeper?

  I am also curious whether the crushing process increases the =
resistance to further deformation.


    Let's hurry up and get this figured out, I'll be restringing the =
next piano in
    about 2 weeks!

    Ed Sutton


  Ed -

  Great opportunity for some documentation.  Are you willing to do it?  =
Measuring all the downbearing (front, rear, net, bridge profile)?  One =
question I would have would be how much downward movement you would =
observe in the seating process, once the piano is under tension.  In =
other words, what would prevent the strings from seating themselves, at =
least in a piano with positive front and rear bearing?


  David Skolnik



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