Dithering Hammers

[Dave Nereson]

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  ----- Original Message -----=20
  From: Alan Forsyth=20
  To: pianotech@ptg.org=20
  Sent: Tuesday, April 01, 2003 5:20 PM
  Subject: Dithering Hammers


  A message I tried to send a few weeks ago!


  Hi guys,
  I am Alan and have been servicing pianos in Edinburgh for the last 10 =
years
  with also a previous short stint in Southern Africa.

  I too have been baffled by the problem of dithering hammers in Yamaha
  uprights (brand new) after re-regulating the set-off to 1/8". It seems =
to me
  that the factory set the set off wider than usual to accommodate the =
muffler
  rail so that the hammers would not block when the muffler rail was in =
the
  down position. However, with the set-off being 1/4", without the =
muffler
  rail (practise pedal) in use, does not give the piano a very dynamic =
touch
  i.e. you cannot play very loud, and above all you cannot play very =
soft!
  which is what "piano" is. The closer the set-off to the string the =
more
  dynamic control the player has . Set- off is the point at which the =
jack
  disengages from the butt and from then on the player has no control =
over the
  hammer.

  If the set-off is too far away you have less control from the moment =
of
  escapement. Now in most actions if you regulate to 1/8" set-off and =
even
  less in the treble, (I'm talking upright actions here) and all the =
other
  measurements are left standard, the action works fine. But on some =
actions
  this just does not happen as with Yamaha. Playing loud is fine, but as =
soon
  as you play very softly, the hammer dithers.
  Now this hammer dither is caused by the butt bouncing off the jack =
before
  the hammer has had a chance to go in to check, and not by the balance =
hammer
  bouncing off the check

   You mentioned a design problem, but just exactly where is the design
  different from other actions? The only design feature I can think of =
is that
  the length of the jack is too short. In other words there is not =
enough
  leverage on the jack by the set-off button. If the jack were longer, =
the tip
  of the jack would move much faster away from the butt during the =
aftertouch
  motion. The jack must get out of the way faster than the hammer =
bounces off
  the string! So to cure the problem is problematic; one can't obviously
  lengthen the jack, but you might be able to increase the leverage on =
the
  jack. I have tried moving the set-off rail closer to the jacks =
themselves
  but this only seems to make a very slight difference. Changing the =
tension
  of the butt springs does not solve the problem either. The only =
reasonable
  solution I have found is to adjust the check distance much closer to =
the
  strings. But then this becomes a non standard measurement, 1/4" =
instead of
  1/2".

  Of course all this begs the question; How softly is a piano supposed =
to
  play? I have had many years experience playing piano in restaurants =
and
  believe me, if there is a table right next to the piano, you have to =
play
  VERY SOFTLY.

  I sure hope one of you out there has not just a solution, but the =
correct
  solution. This has been bugging me for years.

  Best regards
  Alan Forsyth

  _______________________________________________
  pianotech list info: https://www.moypiano.com/resources/#archives


      I don't think you can expect to play quite as softly as a =
well-regulated grand, but almost.  When I used to complain about this to =
the tech. folks at Yamaha in Buena Park, they would say to check the =
same things listed in Carman Gentile's reply, including the pinning, the =
latter being an item you might not expect to be a contributor to the =
problem.  Any hesitation in the key stroke, which might be partly caused =
by a tight key bushing, could contribute to the tendency to dither, or =
"bobble".  So you might take the action out, and tap with quick =
repetition on the rear end of the keys and see that they all return with =
no sluggishness.  Maybe allow the key dip to be slightly larger than =
normal.
      Regarding let-off, if I'm not mistaken, the Yamaha uprights that =
have a Disklavier with the "Silent Piano" feature have let-off at almost =
1/2" !   Maybe it's only 1/4".   I first heard of this at a Disklavier =
servicing seminar given by  LaRoy Edwards at a Yamaha dealer's store.  I =
believe he was claiming that it didn't affect the playablility of the =
piano all that much, which seems doubtful.  I didn't play the piano, but =
the Disklavier mechanism played it at what I would call a pp level, =
maybe even ppp.  So maybe let-off can be a bit wide.  Don't know what =
else to suggest, except call Yamaha and see if they have anything new on =
the subject.  --David Nereson, RPT, Denver

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