[CAUT] S & S D rest cushions

[Jeff Tanner]

You're right. I've never experienced it.  I had some of the world's premier pianists playing one of the instruments with this issue (shanks well over a half inch above the cushions) over several years, and that was never an issue. Our piano faculty studios all had to be regulated with shanks very high above the cushions and I never got a complaint about catastrophic action failure that wasn't due to a sluggish pinning or really low checking somewhere.  Inability to repeat fast enough for the player because checking was too low happened.  I've seen catastrophic action failure happen many times, but it is due to sluggishness or inefficiency somewhere, always remediable by something other than changing the rest height.

At that speed, the hammer should hit the check and the jack reset before the key can rebound, so something else is causing the mis-hit.  If the hammer tail drives through the check, that could cause it.  Raising the rest cushions might also seem to solve it, but that not treating the cause.  The key would have to rebound fast enough that the hammer misses the check for the rest cushion height to be the problem.

You are correct, and it did occur to me immediately after I hit the send button that my statement ignored certain circumstances.  In certain cases where the shanks are regulated too close to the wippens, shanks will hit the repetition lever adjustment screws unless the rest rail is adjusted absolutely perfectly, and even then might still click on them.  But that is an action geometry problem, not the fault of the rest rail.

Jeff


  ----- Original Message ----- 
  From: Fred Sturm 
  To: caut at ptg.org 
  Sent: Friday, August 14, 2009 5:05 PM
  Subject: Re: [CAUT] S & S D rest cushions


  On Aug 14, 2009, at 2:04 PM, Jeff Tanner wrote:


    "Catastrophic Action Failure" happens because checking is too low, hammer flange, jack or rep lever pinning too sluggish or rep springs doing absolutely nothing at all.  Not because of rest cushions.  We shouldn't even need rest cushions or rails.  I've had the same issues with hammer shanks having to be so high above the rest cushions to get aftertouch with reasonable keydip and never one issue of catastrophic action failure unless one of the above was the cause.


  Maybe you haven't experienced it. I have (with all those other variables within good parameters). It happens with specific types of playing, and is rather rare, but it can be a "catastrophic" problem when it occurs in a concert. It has to do with specific timing of a hard, staccato blow and what happens to the key following the blow. Sometimes it is a matter of a fairly rapid repeat, sometimes just a matter of the key not let up all the way before the hammer has completely rebounded (the key keeping the wipp in a somewhat up position). In any case, the result is a jack jammed between knuckle and rep window cushion, which the rep spring can't overcome, I guess because of geometry. I have had the complaint, have asked for a demo, and have been able to reproduce the symptom. The only cure was getting the cushion closer to the shank, and it was definitely a cure. This after checking all those other parameters.
  Ask Eric Schandall, he's had precisely the same experience and strongly recommends that cushions be very close to shanks. I expect Kent Webb would tell you the same.
  "We shouldn't need rest cushions or rails" is a rather naive statement. There are, actually, reasons manufacturers include them, this being one of them.

  Regards,
  Fred Sturm
  University of New Mexico
  fssturm at unm.edu









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