Fw: bore distance: was Re: hammer replacement

[Erwinpiano]

  At least for stwys I'd like to disgree.  I beleive it was Chris Robinson
who stated that steinway actions are designed to reach let-off when the
shank is horizontal and the hammer over centers the last 1mm or so to the
string. The reason he gave had to do with attaining the most effeicent
geometry for that design.  One clue which leads me to think this is right is
that when I have allowed the bore distance to be to long the touchweight was
heavier feeling.  This because poor geometry is now creating more friction
as every part of the action and regulation are cranked further down in its
cycle.
----- Original Message -----
From: "Newton Hunt" <nhunt@optonline.net>
To: <pianotech@ptg.org>
Sent: Friday, June 29, 2001 12:27 PM
Subject: Re: bore distance: was Re: hammer replacement


> Hi David,
>
> The shank should be slightly below horizontal when the hammer is resting
on
> the string.  By measuring string height and center pin height, subtract
the
> shorter from the longer and you have the bore distance when the hammer is
> against the string, optimum, then at about 1/32 inch for future filing.
> When filing initially the hammer will expand to maintain original
> dimensions.
>
> Newton
>
> David Love wrote:
> >
> > Newton:
> >
> > Another issue is the starting point for the shank.  Boring to the
let-off
> > point positions the shank slightly higher and reduces resistance at the
> > beginning of the key stroke effectively reducing the force required to
get
> > the key moving.  (I'm sure there's a more technical explanation)
> >
> > David Love
> >
> > >From: Newton Hunt <nhunt@optonline.net>
> > >Reply-To: pianotech@ptg.org
> > >To: pianotech@ptg.org
> > >Subject: Re: bore distance: was Re: hammer replacement
> > >Date: Fri, 29 Jun 2001 09:41:16 -0400
> > >
> > >Hi David,
> > >
> > >Interesting question you raise.
> > >
> > >I always calculate to string height because that is where the engineer
> > >determined the optimum mechanical advantage for the action.
> > >
> > >But...
> > >
> > >If you measure from bore center to strike point then add 1/8" to an
> > >imaginary line, that line represents the optimum regulation height for
> > that
> > >hammer.  No matter whether that point is below or above the actual
string
> > >height.  So, taking that in reverse...
> > >
> > >               Newton
> >
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