Spring behavior

[Isaac OLEG]

Hello,

Good points about the repetition speed , my theory have some lead in
the wings (translated from French , may be shot in the feet is OK ?).

My thought was that the graphite grease in the springs slot, as well
as the mutton tallow that is used on the key pins in some factories,
can well be the artifacts that helps to even the action feel, or act
as a security towards repetition, while not allowing to repeat so fast
than in optimum configuration.

For sure they slow things in the 2 cases, but the final feel is then
more even, despite the irregularities in pinning , BW, and differences
in ratio from note to note.

I had the bad surprise on some actions after cleaning of the slot and
the spring, to be obliged to re pin more than expected to obtain a
more even touch.
Sure the springs are too strong immediately when we clean the
graphite, but the jack's return will be less fast, as you point out,
with a less strong spring.

The slowliness in the balance lever induced by the spring add a delay
that allows to be sure that the jack/roller contact is more secure,
because more tension goes towards the jack.

For sure a very objectionable reason & method.

For the key pins in particular, I always clean them, and use only
Teflon actually but I believe the little grease that stay at the
balance hole helps to maintain the key in place when the hole is
almost pulley, that is why this mutton tallow is so much used actually
in repairs.

Regards.

Isaac OLEG






is in place first

> -----Message d'origine-----
> De : pianotech-bounces@ptg.org
> [mailto:pianotech-bounces@ptg.org]De la
> part de A440A@aol.com
> Envoye : lundi 21 octobre 2002 12:13
> A : pianotech@ptg.org
> Objet : Spring behaviour
>
>
> Oleg writes:
>
> >I used to worry about the graphite gunk in the balancier
> slot, but have
> >find it to act as a regulator of the spring tension,
> anyway when not too old.
> >As it slows the top of the lever it eventually send more
> energy towards the
> >key , thus helping more repetition that a very slippery
> spring that will tend
> >to push up the hammer too fast.
> >Any idea about it?
>
> Greetings,
>    I don't believe that the increased friction at the top
> of the spring will
> increase repetition speed.  Under fast repetition, the
> hammer doesn't rise
> from check before the jack is reset.  Rather, the spring
> uses the inertia of
> the hammer to increase the speed of the key return.  This
> necessitates that
> the spring move in the slot,(called the grub at the
> factory), and any
> friction here will reduce the speed of the spring's work.
>    As friction increases at the grub, the spring may be
> strengthened to
> compensate, which may put more pressure on the jack to
> return, but the spring
> doesn't lift the hammer in the time it takes the key to
> rise far enough to
> allow the jack to reset. (try it,  put a hammer into check
> and let go of the
> key as rapidly as possible, you will see the hammer drop to
> rest without
> moving upwards at all. )
>    Also, the difference in key return speed between a
> spring that slowly
> lifts the hammer and one that throws the hammer off the
> jack is virtually
> nil.  There is no need for a spring to be strong enough to
> feel the recoil in
> the key upon the hammer's release from check.  An overly
> strong spring just
> creates wasteful resistance to fine escapment control at
> pianissimo levels of
> play. It may force the drop to be set too low, creating
> even more resistance
> during final escapement. It will also create problems with
> checking, and a
> hammer that isn't checked will cause a much slower key
> return than one that
> is.
> Regards,
> Ed Foote RPT
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