Tuning stability (bridge re-surfacing)

[Mark Cramer]

This is a multi-part message in MIME format.

---------------------- multipart/alternative attachment

  -----Original Message-----
  From: caut-bounces@ptg.org [mailto:caut-bounces@ptg.org]On Behalf Of David
Skolnik
  Sent: Monday, March 29, 2004 11:52 PM
  To: jpstickney@montanadsl.net; College and University Technicians
  Subject: Re: Tuning stability


  Fred and Marc..can you tell me what is accomplished by sanding (or
planing) out the string grooves?  As much as we are cautioned about "over
tapping" the strings to the bridge, it seems it would be a lot easier to do
serious damage in the groove-removal effort.  Likewise, unless the bridge
edge has been mangled, what would be the purpose of renotching?



  David Skolnik

  [Mark Cramer]

  David,

  Bridge tops are a bit like hammers, in that strings cut into both, and
that does diminish clarity.

  When you re-surface a bridge, it's just to restore optimal string contact.

  Some people think filing hammers reduces their life, due to all the felt
removal.

  If your habit is to file well below the string cuts, then perhaps that's
true, however, in most cases we're merely re-shaping the hammer's profile to
match the contact surface the strings have already created.

  Same with surfacing the bridge, though I'm often asked " doesn't that
reduce down-bearing?"

  My answer, as I only surface til the grooves are faint (not invisible)
would be "no," though over-zealous string-settling and seasonally-excessive
down-bearing might.

  So, for whatever reason, the grooves are there, and they do affect tonal
clarity by extending wood contact beyond the termination, into the speaking
length.

  By experience (have you ever obsessed over a mysterious "dead-note" only
to find it cause by a peice of lint under the capo?) providing solid/clean
string-terminations and bearings all the way along, is well worth the
effort.

  Next time you have a piano de-strung, have a look at the notches; they
will likely (hopefully) begin precisely through the center of the bridge-pin
line, or better still, just a "hair" behind.

  Now take a close look at the string grooves. The deeper ones obviously
extend well into the bridge notch, and that's where the real string contact
terminates, not back at (and in tandem with) the bridge-pin as it should.

  If you've ever encountered a "shallow notch" where the oscillating string
contacts the notch (buzzing), though there's
  no "visible" string contact, you'll agree, string contact (interference)
can take place well beyond what's visible. (casual contact, the most
dangerous kind!)

  Having said all that, I wouldn't want to encourage anyone unsure of this
work to do something that may damage a piano.

  Everyone contemplating this should read the article described below.
Bill's writing has a gentle way of inspiring, convincing and then empowering
you. (Dr. Bill?)

  However, still hoping to answer your question David, I would suggest in
the same vein that we describe bridge-pins as "loose," capos and agraffes as
"grooved" and strings as "kinked,"  the bridge cap is indeed "mangled."

  What's more, no special skills are required to re-dress the bridge cap
than any of the other defects described above.

  Bill Spurlock caught my attention a decade ago with the following comment;

  "occasionally I have skipped this work (bridge reconditioning) on a
particularly well-preserved piano, only to find a disappointing number of
false beats and variations in tone from string to string. Removing a few
strings and spot repairing has significantly improved the situation, leading
me to adopt the procedures here as standard practice whether repairing an
old bridge or building a new one."

  Bridge Repairs for Better Tone; Bill Spurlock, PT Journal,March 1992

  I've always been pleased with the results David, and am sure you will be
too.

  Meanwhile, the forecast is sunny and 12 degrees C tomorrow. I'm off to the
lake and see if I can finish plumbing the second floor.

  There are still about 30 ice-fishing shacks out on the lake, anyone want
to wager when the last one will fall through?

  (if you don't know what ice-fishing is, do a google search or call
Garrison Keelor!)

  best regards,
  Mark Cramer,
  Brandon University















---------------------- multipart/alternative attachment
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/caut.php/attachments/2c/a4/7f/90/attachment.htm

---------------------- multipart/alternative attachment--