[CAUT] S & S D rest cushions

[Jeff Tanner]

What it sounds like you are describing is a pinning problem.  In this case, too free.  Rep lever and/or hammer flange bushings that are too free make for touchy rep spring adjustment.  Start by repinning those bushings and see if it can't withstand stronger rep spring adjustment without bobbling, and eliminate CAF.
Jeff
  ----- Original Message ----- 
  From: Andrew Anderson 
  To: caut at ptg.org 
  Sent: Friday, August 14, 2009 6:20 PM
  Subject: Re: [CAUT] S & S D rest cushions


  Have to agree with Fred here.  I experimented with the rep springs and had to choose between bobbling hammers at mp play or bolstering the whip cushions with additional cushion felt tack glued to the original felt.  I did this after advising the customer that the previous hammer install had been severely botched and that the action would benefit from a total rebuild.  They went for the cheap fix and were delighted with it.


  Andrew Anderson


  On Aug 14, 2009, at 4:05 PM, Fred Sturm wrote:


    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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