TR: Virtual Capstan

[Isaac OLEG]

Ron, Richard

What we may consider is how much force is necessary to keep that
advantage long enough during the stroke and not have it transferred
abruptly to the capstan, seem that we have now a variable leverage
during the stroke.

What I don't figure well is how velocity play a role, the pressure on
the contact parts is very strong during the stroke unless the action
decompress, is the repulsive action of the magnets still producing a
significant advantage under those conditions, why not ?

I guess I see your point about inertia, do you mean there is a
supplementary frictional force between the 2 magnets acting as a brake
is not it ? or was it just because of the weight of the parts.

The thing about the (less) friction input and the way it evolve during
the stroke may well be something to consider I guess.

Because the lower magnet is supported it rob a tad of friction, may be
not very significant for sure.

I guess another point that concern the shape of the magnetic field may
be examined, is a ring type magnet more focused and with less side
effect ? probably yes. may be a ring should be used on the keys and a
tubular magnet or a less large one on the whippen. WE should avoid
interference the most, and may be look for the most efficient setup in
that regard. I've seen also that some dome shaped magnet exist, (not
in that size may be) They could stay more efficient while the parts
are getting farther (and out of alignment).

Late stuff tonight !

Bests


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 : Ron Nossaman [mailto:RNossaman@cox.net]
> Envoye : dimanche 22 juin 2003 22:26
> A : oleg-i@wanadoo.fr; Pianotech
> Objet : RE: Virtual Capstan
>
>
>
> >It is lessening the friction a lot probably, that may change under
> >real play modes, while I don't understand how the magnet force act
> >verse the inertial mass of the parts (what are the
> elements involved
> >?)
>
> I doubt any significant friction effect, though there may be. It's
> primarily just leverage. Using a random action model I have
> on hand for
> dimensions, 1g placed on the key where the magnet would be
> adds 0.79g to
> the touch weight. 1g on the wippen where the magnet would
> be adds 1.27g to
> the touch weight for a net +2.06g to the touch weight. 1g
> of magnetic lift
> adds 0.79g, and removes 1.27g, for a net loss of 0.48g to
> the touch. So 1g
> magnets must produce at least 2.06g lift to break even.
>
> Setting this up, the lighter of the magnets should go on
> the wippen, and
> the adjustment and doubled magnets (if any) on the key
> because the weight
> penalty is greater on the wippen, where the lift wouldn't change.
>
> >A couple magnets in the whippen rail and whippen lever should more
> >work as assist springs (and with the same pitfall in regard of the
> >help given only at the beginning of the stroke).
>
> The boost isn't only at the beginning of the stroke, but it
> does lessen as
> the key goes down and the magnet gap widens.
>
>
> >I bet that only once installed in a real action one can
> evaluate what
> >it really gives, but if it help to break the initial
> inertia that is
> >yet great, as this is what pianist tend to complain the most.
>
> Yes, it will require a real fully working prototype or two.
>
>
> >The effort is given in the same direction of the whippen
> lever spring
> >also, so is the lesser friction at the heel  meaning more
> friction at
> >the roller/lever interface, or does it stay the same under the same
> >global force applied ?
>
> Don't know.
>
>
> >I wonder if a magnet is not exactly acting in the most optimum way
> >against inertia lessening it far better than a spring
> because of its
> >permanence.
>
> It won't lessen inertia. It will increase it. The question
> is how it feels
> in play.
>
>
>