tapping strings

[David Skolnik]

I'll try for a little more coherence tonight-

First,  thanks Ron N for helping me locate those previous postings. It's 
going to take a while to sift through them, but I've seen enough to 
understand your sense of deja vu.  Interestingly enough (or not) the date 
was almost exactly one year ago.  The thread actually seemed to start with 
this:

>From: ANRPiano@AOL.COM
>Received: from ANRPiano@aol.com
>         by imo-m04.mx.aol.com (mail_out_v29.14.) id 4.a1.134c86c4 (17382)
>          for <pianotech@ptg.org>; Sat, 31 Mar 2001 08:14:36 -0500 (EST)
>Message-ID: <a1.134c86c4.27f7323c@aol.com>
>Date: Sat, 31 Mar 2001 08:14:36 EST
>Subject: Bridge caps


Second, a question for all you rebuilders out there.  When stringing a new 
board/bridge assembly, do you preload the board before bringing up the 
string tension?  If not, then it would seem to me that until the board has 
conformed to its anticipated shape under load, the down pressure of the 
strings, as they are being pulled up will be mostly on that front edge of 
the bridge. Would that help to explain the severity of the indentation, 
even in the absence of excessive playing, tuning or climate swings?

The next question might be, at what point the notch in the bridge pin 
forms, and which, or what combination of mechanical actions is 
responsible.  Is it the initial application of string tension (with the 
sliding motion of the string being pulled up to tension)? The static stress 
over time? The tuning process? The motion of the string when played?  I 
could see the notch causing enough friction to inhibit the downward return 
of the string to its seated position, especially if the other restorative 
forces like downbearing and string offset were less than those numbers Ron 
used in his example. Which brings us to this:

Ron N qualified his remarks by defining his conceptual model as having the 
theoretically ideal downbearing configuration, positive on both front and 
back, but not too much.  Sorry mate, I haven't seen one of these creatures 
in much too long a time.  So let's try a different model:

Let's suppose I have front bearing of  (-).006" with positive net .004" 
(rear bearing + .010") as measured with Lowell gauge.  (From the point of 
view of assessing termination characteristics, these numbers are deceptive, 
but that's for a different posting).
The tendency for the string to ride up the pin will be resisted by the 
pin's cant, but we can assume that, at some point in time, that string will 
come up.  Let's say I get a little tell-tale twang.  My options are to tap 
string for temporary (?) improvement or to allow string to remain at the 
equilibrium point it has arrived at, thereby maintaining greater tuning 
stability.  As far as where you tap, I suspect its a bit like the 
accelerated action dichotomy, in that you could tap the string somewhere on 
the bridge, using greater force, or right at the pin, using less force.  As 
with most other aspects of piano work, with proper care, I don't believe 
tapping NEED be injurious.


David Skolnik