String Levelling questions

[Newton Hunt]

Comments:

Agraffes are not the problem in grands.  Modern machine tools are quite
good and drilling brass is a simple procedure the produces quite equal
pieces.  Without proof I would tend to plame the felt material the
string crosses on it's way to the tuning pin.

String curl could be to blame, but more likely is inhamogeniuty of the
wire, tension inequalities produced during stringing and initial
tunings.  

Because strings are lifted upward on the tuning pin side of the agraffe
there is a catenary curve to the string before it enters the agraffe. 
This curve nagatively effects inharmonicity, sustain and string level. 
This curve needs to be minimized after stringing by lifting all the
strings of each unison.

In the case of verticals I must (to my possible demise) disagree with
Del.  (duck!)  Verticals DO have less a problem with string leveling,
one because the v-bar and the pressure bar are of metal and the
closeness of the pressure bar to the v-bar helps keep strings level.  I
do find strings that need leveling on uprights and push them toward the
back or file the hammer to mate the strings.  

I think that in the past, when softer hammers were the norm, we need to
do more leveling for the harder hammers.  THe harder the hammers the
more critical string level becomes.

Strings that are unlevel are struck at different times, measured in
micro seconds, which causes partial (harmonic) phase shifting that
causes phase cancelations.

If all the strings are leveled before final assembly by lifting each
unison to the same height when the piano is at pitch then far less
lifting by individual string will be needed.  The string leveling lever
from APSCo works well.  Hint; do not use on old strings.

One further area is at the bridge pin.  A string roller helps fit the
string to the pin and the bridge to minimize the catenary curve. 
Individual strings can be helped with the tool like a small screw driver
with a notch cut in the center of the blade about trice the string
thickness which can be used to bend the string around the bridge pin and
down into the notch of the bridge to help with false beats.

Leveling strings is like pitch raising a piano.  It is lift, tune, lift,
tune, etc. until the lifting and the tuning is stable.

	Newton
	nhunt@jagat.com