[pianotech] finding the strike line

[David Love]

Do you typically find, then, that when changing to a transition bridge that
there is a maximum percentage reduction in speaking length that you are
willing to undertake in order that the change in SPR doesn't result in too
dramatic a change in the tone in that section?  It seems that the smoothest
transitions (at least on paper) require quite significant reductions in
speaking length in the transitions.  More modest changes which likely would
have less impact on the SPR seem to mean compromises in the scaling through
that section--though, I guess, not as much of a compromise as the original
which caused one to consider the change in the first place.  

David Love
www.davidlovepianos.com


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Delwin D Fandrich
Sent: Monday, February 09, 2009 12:17 PM
To: pianotech at ptg.org
Subject: Re: [pianotech] finding the strike line

| -----Original Message-----
| From: pianotech-bounces at ptg.org 
| [mailto:pianotech-bounces at ptg.org] On Behalf Of David Love
| Sent: February 09, 2009 10:01 AM
| To: pianotech at ptg.org
| Subject: Re: [pianotech] finding the strike line
| 
| Why is that?  I noticed that you moved the agraffe line on 
| the Walters Grands that you developed with transition bridges.  
| 
| David Love
| www.davidlovepianos.com

Yes, I did. But that was on a new design and a new plate pattern. It seemed
prudent to at least start the piano out with the hammer strike point ratio
(SPR)
I deemed "proper." When laying out a new plate design--or modifying an
existing
production plate pattern--there is no reason not to do it right.

It's hard to say, however, just what SPR philosophy was being followed in
many
piano designs (some of which are still in production today). There may have
been
one at some early date but then the scaling was changed forty-seven years
later
by someone who did not have a grasp of such subtleties with the result that
as
the piano exists today there is no consistent SPR being followed. Or the
scaling
was changed but no one bothered to change the agrafe line. Or the V-bar
shifted
a time or two as the plate pattern was being repaired. Or the cope and drag
mated up out of alignment for a few (or a few thousand) castings. 

The bottom line is that, as a rebuilder, I'm pretty much stuck with what I
get.
Unless, of course, I want to plug the original agrafe holes and redrill and
tap.
Somehow it has never seemed worth the effort. Does some deviation from that
"proper" SPR make a tonal difference? Yes, but it may be a difference that
is
only measurable using relatively sophisticated equipment and not one that is
readily audible. 

With existing pianos the proper use of a transition bridge--along with good
scaling--will reduce the timbrel variations due to deviations from the
"proper"
SPR across the bass/tenor break to such an extent that they can usually be
voiced out without too much trouble. At least this has been the case with
the
type of soundboard construction and the overall scaling philosophy I've been
using for the past thirty-five years or so.

ddf