[pianotech] Bridge agraffes FYI

[Encore Pianos]

Hi Jim:

Did you get a chance to look at that Steingraeber Phoenix at Larry Buck's
shop in May when we were there for the Bill Shull Steinway Patent day?  I
know you were there because you had to sit next to me,  you poor soul.  If
Larry still has that piano, you could probably give him a call and ask him
to take some measurements for you.

I spent some time listening to that piano, both with my hand and others
playing it.  There was much to like about it (I favored it over the
"regular" bridged Steingraeber next to it, it was well voiced and seemed to
have good volume and sustain.)  It did lack what I might call dynamic
excitement and was a bit linear as it stepped up the loudness ladder.  It
sounded like a very good piano with bearing a bit on the shallow side, to my
ear.   Understand that these are small criticisms, I did like the piano.
What did bother me more was what I would call a "warble" that seemed to be
there on all of the notes, and was more audible than I would have preferred.
On louder playing, the piano sounded a bit overloaded, perhaps due  to
bridge agraffe leakage.

This is speculation on my part, but there really seems to be only one point
of contact for termination on this system and the Stuart agraffe as well,
although they are slightly different from one another.  Since piano wire is
round, and that wire is bearing against the rounded over, straight edged
termination piece, it seems to me that there is only a single very narrow
point of contact between the string and the bridge terminus.  Of course,
there is the bearing force of the string deflection along with its tension
to press and hold the wire to the termination.  Let's compare that to our
bridge pin drilled at an angle of about 70 degrees in relation to the bridge
top.  The side bearing presses the wire into this angled corner, against two
bearing surfaces.  When life is good (tight bridge pins, good notching, etc.
etc.) the sound will be very clean and it will be  a sufficiently secure
termination.  Contrast this to our bridge agraffes with their single point
of contact.  It seems that it has to be less secure, the bearing forces of
the deflected wire notwithstanding.  When the hammer sets the string into
motion, it doesn't just vibrate in the vertical plane, but in the horizontal
plane, and everything in between.  I can't help but believe that this
singular termination point is insufficient to constrain the wire adequately
in the other planes, and perhaps even less well so in the vertical plane.
Hence the noisiness these agraffes seem to have at higher volume levels.
Or, at least that is my theory.  

There is another potential problem with this design, at least as it is
implemented individually by Stuart and Dain.  In both these designs the
terminating pieces are separate pieces from the main body of the agraffe.
Stuart's design has something akin to a bridge pin laying on its side in a
curved well in the main body of the agraffe.  As far as I can see from
looking at pictures of the agraffe, it is held in position only  by the
downward pressure of the strings.  I don't know if they are epoxied in
place. If not, is this secure enough to not allow any movement in position?
I am not so sure that it is.  Consider how little insecurity it seems to
take for a traditional bridge pin to start getting false.  The Dain agraffe
is this triangular shaped piece that goes through an opening at the front
and back of the bridge.  There is a screw that holds the agraffe securely to
the bridge, and presumably  that presses into the tapered sides of the
termination piece.  Is that sufficiently secure to not cause problems?  I am
not so sure it is, either.  

I would enjoy other's reflections and comments on this, as there is a lot
more I would like to understand more about how all this stuff works
together.  

Will Truitt




-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of Jim Ialeggio
Sent: Friday, October 26, 2012 9:15 AM
To: pianotech at ptg.org
Subject: [pianotech] Bridge agraffes FYI

meant to add...

Has anyone seen the bridge height on a Steingraber Phoenix or Stuart Piano,
or indeed a retrofit (other than a base retrofit)?

Jim

-- 
Jim Ialeggio	
jim at grandpianosolutions.com
978 425-9026
Shirley Center, MA