[pianotech] Tuning the duplex sections

[John Delacour]

A propos of nothing in particular, I mentioned the other day the 
sloping wrestplank on certain 19th century pianos as illustrated below




and mentioned that the angle is 8° and that the bearing cloth serves 
as little more than a damper for the front section rather than a 
bearing as such.

This design seems to have several advantages from a mechanical and 
tuning point of view over the design that followed it and persisted 
for many years.  Contrast this with the arrangement on a classic 
Bechstein grand where you have a beech bearing up to 3" wide covered 
with a thin bearing cloth -- sooner or later it becomes extremely 
difficult to tune these owing to the friction at the bearing combined 
with oxidation of the strings.  With the old arrangement the pressure 
on the bearing/muting cloth is minimal, but it must have very similar 
characteristics to a front duplex that is listed or otherwise muted.

The reason why this old design died out might have something to do 
with the development of the full metal frame with integral wrestpin 
plate, but I can't see any practical difficulty in making a casting 
to follow this design.  The other possibility is that makers decided 
this arrangement was tonally inferior to the design that followed 
it...

...On pianos of the next long-lived generation with agraffes, which 
is to say almost all pianos except Steinway copies, the bearing is 
brought so close to the agraffe that you often need to kink the wire 
when pulling it through in order to avoid nicking the bearing cloth. 
In other words there is only a very small length of wire between the 
stud and the bearing, so that there can be no appreciable leak of 
energy across the bridge and the bridge becomes as closely as 
possible a true termination to the speaking length.

The case of the studded upright is similar in effect the stud 
provides for a fixed angle and an extremely short length between the 
bridge and the string holes.  In my experience the tone of that 
minority of uprights that have studs all through has always been 
good, though uprights with studs always to come from makers that are 
pretty good in the first place.

This topic has got me questioning certain ideas that I've held, or 
been developing, for a long time.  The primary consideration must 
always be optimum tone.  If a certain design makes it easier to tune 
or more durable, well and good, but if a design that has advantages 
is to the slightest detriment to the tone, then tonal considerations 
must prevail, I think.

JD
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://www.moypiano.com/ptg/pianotech.php/attachments/20110316/7576ee34/attachment.htm>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: sloping_plank.jpg
Type: application/octet-stream
Size: 21777 bytes
Desc: not available
URL: <https://www.moypiano.com/ptg/pianotech.php/attachments/20110316/7576ee34/attachment.obj>