String termination question

[Farrell]

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