Key Inertia - action saturation

[Isaac sur Noos]

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Sarah, list,

Hello

First thanks much for all of you that send me gentle posts they enlighten my
Christmas day ! I indeed did not take too seriously the "reaction" of Mr.
C.T. I know the feeling to be made frustrated or nervous with the reading of
some posts, all of these is really of little importance in the end.

I conscientiously have read the beginning of that thread (that I did not
really follow from the start) .

I like the way you describe the "impedance match" between the pianists
hand/arm and the action . Particularly the "running in the sand"

There are likewise actions that are too massive for me to play comfortably.
If I were a huge person, on the other hand, I imagine I would be able to
play those actions with ease -- and my friend's spinet would seem like even
more absurd a tinker toy.

   > Mind you, I don't really know how the mechanical impedance of an arm
would be characterized and how it would best be matched to the impedance of
the action, as referenced to the front of the key.  Perhaps our engineer
friends could help us with that one. In the end, I would think it important
to have some degree of impedance mismatch, to aid with the hand's rebound
from the key.  If the action's impedance is higher than the arm's (which I
would think would be an INCREDIBLY heavy action such as we've not built),
then the hand would spring off of the tops of the keys.

   Have that kind of feel with some Kawai action (series KG) when loaded
with massive Renner hammers like it was done in France on all of them in the
70's (because the original hammers where really too mushy I guess) Static DW
then is as high as 120 g in the low bass, and around 80 DW in the medium.
  There was a period where pianists believe that heavy actions was better
for them - from a muscular point of view. Hopefully we came back to more
acceptable standards after some time and a few tendinis I suppose.

  >  If the impedance is the same, then there would be little or no
"spring," and there would be a sensation similar to running in the sand --
maximum energy transfer per note, but too much "bogging" on each note to
have energy to put into the next note.

  I've find that kind of sensation on some "accelerated actions" and also on
action with leading nearer the balance rail - while the sensation is may be
also due to other parameters regarding the return of the action, kind of
lack of rebound there.

  >  If the impedance is lower, then the key would bottom, and the
fingers/hand/arm would be able to "hop" off of the front rail.  If the
impedance is too much lower, then there would be "nothing there" -- as with
the spinet -- and playing the piano would almost be the effortless
experience of "playing" one's dining room table -- or a toy electronic
keyboard.  I suspect this all comes down to trial and error -- personal
taste.  Perhaps some table of values could show average preferences, but I'm
sure much would depend on the individual.

  That is where having enough friction during letoff allows to gain a little
controllable resistance in the action, seem to me that the pianists use a
basic "sustentation" of their arm that serve to adapt to the general
impedance of the instrument, and that the part remaining for nuances is in
the fingers and wrist abilities to find a compliance with the letoff moment
and the very last moments before (namely action compression)

  I wanted also to restate why I talk often of the way the action is under
compression, while it is fairly possible I am very wrong on the subject.
  Nobody seem to answer on these, may be because this sound too much
esoteric comments (they are certainly not facts that could be ascertain with
certitude)

  If I see a piano action acting with springiness (from the shank and from
the key) it is mostly because of friends that have seen the videos of the
key touching the front punching before the hammer actually hit the string
(under certainly only heavy playing) , but also because there is an
important change in tone depending of the aftertouch (grand piano) Then I
theorize about synchronization of the bottoming of the key and the contact
moment at the hammer.

  Experiment that could show from what velocity the friction on the roller
induce flexion of the key (what kind of torque is applied at the
jacks/roller contact point and how is delayed between shank flex and key
flex) should certainly help me to clear up those matters.

  The hammer is accelerated a lot during the stroke so it is certainly
generating a lot of torque on the rest of the system.

  I suppose also that a truly rigid action would be difficult to deal with.

  I understand that these are certainly not subjects even easy to approach
with some numbers, but , assuming the letoff occur at 2 mm from the string,
to produce that move let's say that a 2/5 = 0.2 mm move at the front of the
key is necessary, seem to me not very unrealistic that the key is able to
flex that little if a sufficient torque exist at the capstan (shank flex not
even in the picture).

  I understand that as "action saturation" my take is that there is always
some , particularly if the pianist play too hard. Some of you may certainly
have some good way of expressing those ideas, and correct me if I am wrong.

  That is also why I lend to the side of James Ellis for the key lack of
stiffness induced by too much holes in them, notice that Steinway keyboards
have a longer capsule than usual, if we have to reinforce the key because of
the leading method employed that seem a too heavy task for what is expected.

  Again thanks to all who write me their good Christmas wishes - I am 48
today BTW.
  It's been a wonderful year on PianoTech, take care of you.

  Peace (TM - copyright Sarah)

  Isaac







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