action ratios

[Isaac OLEG]

Hello Bill Ballard,

In fact the assist spring may not be used with too heavy hammers then,
as friction will be extreme at letoff moment anyway (that was probably
the reason why these Schimmel where unplayable)

Very interesting your proposal about the angled capstan.
I guess this was not on purpose, only because the magic line is 90? to
the intersection of the capstan/whippen heel . SO the ratio is
changing all along the move of these angled whippen .I've seen them in
the Pfeiffer book, and they where said to be less efficient than
'normal ones is not it ?.

About hammers filing, how I understand it actually, even when we file
the hammer, we don't really want to reduce the height, if we where to
file to that point, the hammers are to be changed anyway. The height
is reduced by the wear of the hammers it is enough as that , if I file
a hammer the string marks may stay apparent, and the top unfilled.

And taking too much felt is bad (too much weight off). After filing we
can restore some height by deep needling and having the hammer to grow
a little again, that is why lacquered ones are finished once
lacquered.

Thanks for the ideas.

Regards.

Isaac OLEG




> -----Message d'origine-----
> De : pianotech-bounces@ptg.org
> [mailto:pianotech-bounces@ptg.org]De la
> part de Bill Ballard
> Envoye : vendredi 1 novembre 2002 16:06
> A : Pianotech
> Objet : RE: action ratios
>
>
> At 11:59 AM +0100 11/1/02, Isaac OLEG wrote:
> >I wonder something about the assist springs too :
> >
> >As they are less strong when the whippen is at letoff
> height than when
> >at rest, they can lighten the beginning of the key move, or make
> >heavier the letoff moment, depending of the way they
> regulate, if the
> >difference is enough.
>
> Agreed. This is one of the nice by-products in the behavior
> of srping
> balancing. The spring's effect is greatest at the beginning of the
> stroke, when you need help to get the parts moving up to speed. At
> the far end of the cycle, its effect is at its minimum, right where
> you want gravity (now about to pull the hammer back down)
> to have as
> little opposing competition as possible.
>
> Kind of like the angled capstan. File the hammers, they get lighter
> and shorter. Raise the hammerline to compensate for the shortened
> hammerbore, and the angled cap moves backwards on the rep heel,
> raising the action ratio and compensating for the lightened SWs.
>
> >Do someone try to measure the difference of efficiency
> between these
> >two positions, in grams ?
>
> One could certainly measure the rep weight at the start and end
> positions of its movement, giving you the decrease in
> balance weight
> due to the motions' lightening of the spring pressure. I'd guess it
> would fall in the bag of things resulting in the friction
> gradient we
> all encounter measuring DW/UW.
>
> Bill Ballard RPT
> NH Chapter, P.T.G.
>
> "When writing a mental note, first procure a mental piece of paper"
>      ............mental graffitti
> +++++++++++++++++++++
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