Inertia (magnetic driven action)

Isaac sur Noos oleg-i@noos.fr
Wed, 31 Dec 2003 00:44:18 +0100


Hello,
A friend of mine pianist (professional), have find very tiring the
Fazioli fitted without leads (actually I believe the system is now
mixed leads/magnets).
Because he was obliged to go with the key all along (no way to throw
the key and wait for it to rebound)

He calls that inertia of a key (absence of inertia in that case) and
say it is necessary (to have some) for really fast playing.

Best Regards.


Isaac OLEG

------------------------------------
Isaac OLEG
accordeur - reparateur - concert
oleg-i@noos.fr
19 rue Jules Ferry
94400 VITRY sur SEINE
tel: 033 01 47 18 06 98
fax: 33 01 47 18 06 90
mobile: 033 06 60 42 58 77
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> -----Message d'origine-----
> De : caut-bounces@ptg.org [mailto:caut-bounces@ptg.org]De
> la part de Ed
> Sutton
> Envoyé : mardi 30 décembre 2003 15:05
> À : College and University Technicians
> Objet : Re: Inertia
>
>
> John Hartman wrote:
> >
> > I figured the MOI for the three action parts of a typical
> note. The
> > hammer was 8 gms and there were three leads in the key.
> The front arm of
> > the key was 25cm and action leverage was 5.3/1 with a BW
> of 35gms. Here
> > are the number for the MOI as adjusted for reflected MOI:
> >
> > Key MOI = 10,307 gmcm^2
> > Wippen MOI = 3149 gmcm*2
> > Hammer and shank MOI = 165,528 gmcm*2
> >
> > There may be many virtues for keeping leads out of the
> keys but I can't
> > see how it makes very much difference to the perceived
> weight of the
> > action.
>
> Similarly, using Jim Ellis' simple velocity formulas, I
> calculated that with a 12
> gm hammer head, and 48 gms of lead (more than any of us are
> likely to use!), with
> the leads magically compressed at 1/2 distance of the key
> from the balance pin,
> the force to move the leads would be 1/25 of the force to
> move the hammer head
> (all other factors omitted).  If the leads were magically
> compressed to be at 1/4
> of the key length from the balance rail, the force to move
> the leads would be
> 1/100 of the force to move the hammer.
>
> These are simplified and exaggerated results because
>     1) All other parts weight are omitted
>     2) The front weight is excessive
>     3) It would not be possible to compress the leads to a
> single point, so that
> in practice one could not make such a significant change in
> the location of the
> leads.
>
> This leads to the question of whether a pianist could
> discern a difference in the
> order of 1/100th, 1/50th, 1/25th of the total force needed
> to move the system and
> make a sound of a given intensity.  And how might we test
> this empirically?
>
> One of the claims of the Magnetic Balanced Action is that
> the key lead inertia is
> removed from the system.  This is certainly true, but is it
> significant for
> performance? A blind comparison between two Fazioli pianos
> with identical
> downweights, one with key leads, one with MBA would be the
> way to test this.  (A
> performer friend who has played the MBA is convinced he can
> feel the "lack of
> inertia."  However, I have felt a similar ease and
> sensitivity in a standard
> Fazioli, so I am not yet convinced what he feels is the
> result of removing the key
> leads.)
>
> Or might it be possible to install a few MBA keys in a
> standard weighted piano,
> adjust them to correct downweight, and see if the performer
> can detect them, and
> how?
>
> Again I suspect that the difference would be in speed of repetition.
>
> So, Jim, we're looking forward to your experiments in jack
> reset time!
>
> Ed Sutton
>
>
>
>
>
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