String termination question

[Joe And Penny Goss]

Hum,
Never thought along those lines.
Could lead one to think that the sound board might also be involved in the
mix.
Joe Goss RPT
Mother Goose Tools
imatunr at srvinet.com
www.mothergoosetools.com
----- Original Message ----- 
From: "Farrell" <mfarrel2 at tampabay.rr.com>
To: "Pianotech List" <pianotech at ptg.org>
Sent: Monday, January 14, 2008 9:04 AM
Subject: Re: String termination question


> I'll stick my neck out here and speculate on a direct answer to Geoff's
> original question of why we need a two-plane termination at the bridge and
> only one at the capo/agraffe.
>
> Is it not because at the capo/agraffe, we can easily have as much of a
> counterbearing angle as needed to provide adequate clamping of the string
to
> the termination up there. However, on the bridge, the counterbearing angle
> (or backscale or downbearing angle) is restricted by soundboard
performance
> needs and is usually rather small. So the small backscale simply does not
> provide for sufficient downward string force into the bridge - so we need
to
> provide a clamping mechanism.
>
> In other words, the front termination is self-clamping because of the
large
> force of the string on the termination point created by the string tension
> and the large counterbearing angle. The bridge termination requires a
manual
> clamp (offset bridge pins) of some type because of the small force of the
> string on the termination point (bridge) created by the string tension and
> the small counterbearing/backscale/downbearing angle.
>
> And of course, there may be more reasons, but it seems to me this basic
> difference in string pressure on the termination points is reason enough
to
> go to something like what we see in most pianos. Even the bridges with
> agraffes have similar needs & features.
>
> Ron?
>
> Terry Farrell
>   ----- Original Message ----- 
>   I made the mistake of thinking the other day, and I started wondering
why
> piano strings are terminated at the bridge on both the X and Y axis but at
> the capo bar, or agraffe, on only the X, (or perhaps that's Y depending on
> how you are looking at it), axis. We go to lengths to make sure the
strings
> are seated properly at the bridge so that there is a definite and precise
> termination in both planes at the bridge and bridge pin. Why then is the
> lack of termination in both planes not a problem at the agraffe and capo
bar
> end?
>
>   -- Geoff Sykes, Los Angeles
>
> ----- Original Message -----
> >> I don't think the primary purpose of a bridge pin is to prevent the
> >> string from sliding around on top of the bridge.
> >
> > The pins serve two functions. They are the string termination, and they
> > clamp the string to the bridge.
> SNIP
> > Ron N
>
>