Virtual Capstan

[Isaac OLEG]

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Hello Tom,

Indeed your comment make sense, the lightening is to be supported by the
pianist's hand but indeed the whippen ratio is probably changing, as the
friction between the capstan and whippen heel).
These virtual changes are probably not the same depending the speed the key
is played, but I just suspect it, don't see why it should be.

If there is a reaction time between the magnets then they act as springs are
not they ?

Is there one ???????

I wish I will be experimenting with those before the end of the month .

I showed the setup to Stephen Paulello, and he find the idea very neat, he
experimented once with a magnet driven letoff, that suppress the friction at
the button, but indeed too much problems to be precise and consistent.

Very interesting project, and a generous Richard !

Greetings.

Isaac OLEG



Isaac OLEG

Entretien et reparation de pianos.

PianoTech
17 rue de Choisy
94400 VITRY sur SEINE
FRANCE
tel : 033 01 47 18 06 98
fax : 033 01 47 18 06 90
cell: 06 60 42 58 77

  -----Message d'origine-----
  De : pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org]De la
part de Thomas Cole
  Envoye : dimanche 22 juin 2003 10:10
  A : Pianotech
  Objet : Re: Virtual Capstan


  Bob,

  In your analogy, it wouldn't matter if you lifted the sack of sugar
directly or by means of repelling magnets because there's no difference in
leverage.

  I believe the idea is not that the magnets are not supplying extra force,
nor removing weight as wippen assist springs do, but that they are shifting
the position of capstan and heel which changes the action ratio. Lower ratio
equals less DW. It remains to be seen if  there is any advantage in actual
playing. If Richard is getting favorable DW/UW measurements, and I don't
doubt that he is, that's one thing, but it's only a theoretical point.

  Tom Cole

  BobDavis88@aol.com wrote:

    Imagine holding a 10-lb. sack of sugar. You feel it as ten pounds. Now
attach a powerful magnet to the bottom of the sack, and a powerful repelling
magnet in your hand. The magnets might not touch, but is the sugar lighter?
No. It might even float a few inches in the air, but you still feel ten
pounds of weight in your hand, the same as if it were sitting on top of a
coil spring which you were holding.

    This is because the magnets are part of the lever system. In order to
actually remove weight from the system, they have to be external to it. This
is true as well of springs. Wippen assist springs are external to the
system. Their  force acts against the support flange, and in turn upon the
[theoretically rigid] wippen mount rail. In order for a pair of magnets to
store potential energy in the deformation of the magnetic field, one of them
must be mounted outside the moving part of the system; i. e., on the action
frame.

    I think Richard should re-do his measurements.

    Bob D


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