tuning stability

[David ilvedson]

I have been tapping the bridge pins themselves and not the 
string lately.  The vibration will seat the string and won't 
damage the bridge top.  Give it a try...

David Ilvedson, RPT
Pacifica, CA


> From:          "Richard Moody" <remoody@easnet.net>
> To:            <pianotech@ptg.org>
> Subject:       Re: tuning stability
> Date:          Mon, 11 May 1998 00:57:38 -0500
> Reply-to:      pianotech@ptg.org

> Here is another take on not about seating strings so much, rather as how
> bearing affects the seating of strings. 
> 	Bearing is how much the strings push down on the bridge.  To accomplish
> this think of how much the bridge should push UP on the strings. The
> string without a bridge would occupy a straight line from the hitch pin to
> the upper bearing point.  In order for the string to be amplified through
> a soundboard, a bridge is needed. this bridge forces the string away from
> its straight line so that contact can take place.  
> 	Now in most stringed instruments the point of contact of the bridge with
> the string is just that..a point.  In a piano  however, there are TWO
> points of contact with the bridge. This can be refered to as the front
> bearing and the rear bearing on the bridge.  This can be visualized by
> imagining how the bridge surface between the front and rear  bridge pins
> contacts the string. Now you can see if this contact is not ideal, tapping
> the string to make contact can only be temporary.  
> 	How can the contact not be "perfect"?  Imagine the bridge rising to meet
> the string as an elevator.  There is the shorter string segment from the
> rear of the bridge and the longer segment from the front of the bridge.
> What then is the ideal plane of the bridge surface to the angle of
> deflection of the string?  If this "ideal" relationship has been met by
> the piano maker, no tapping is necessary. The pressure of the string on
> the bridge will seat the string properly.  If the surface of the bridge is
> canted away from the string, too far either way, you will be tapping
> forever, in order to "seat the string" in order to reduce false beats or
> tuning instability. 
> 	Even if the string is seated "properly", there is a debate about whether
> more down bearing should be at the rear of the bridge or at the front of
> the bridge. And engineers who argue that this is impossible to worry
> about, (measure) because the tolerences are too small. But don't tell that
> to the people who favor rear duplex systems, or the "accujust" hitch pin.
> And there is also the concept that induced strain on a sound board
> "amplifies" the sound.... 
> 
> In regards to tapping strings to the bridge with a hammer shank or brass
> rod, I prefer a toothbrush handle.  It seems to give a better sonic
> response, in additon to the concerns mentioned below by N Barret, and R
> Jolly.   I have done this so rarely, because of considerations mentioned
> above, I wonder if others might want to comment about the sonic
> differences between wood, brass, or plastic tappers? 
> Richard Moody   
> 4-11-98
> ----------
> > From: Norman Barrett <barre46@ibm.net>
> > To: pianotech@ptg.org
> > Subject: Re: tuning stability
> > Date: Sunday, May 10, 1998 10:41 PM
> > 
> > Hello list,
> > Let me post my 2 cents worth about seating the strings. The tool that I
> made to
> > do this job is a piece of 1/4" brass rod about 5" long. One end I have
> filed a
> > grove in to help keep it on the string. This tool fits nicely in the
> > combination handle and I can just lightly bump each string down with the
> heel
> > of my hand. You could probably do the job by simply pushing down gently
> because
> > the only thing holding the string off the bridge is friction against the
> bridge
> > pin. This is my humble opinion.
> > Norm Barrett
> > 
> > Roger Jolly wrote:
> > 
> > > Hi Jerry,
> > >          The reason I prefer a hammer shank, is that it will split
> before
> > > you can kink the wire, ( another scorce of false beats) also less
> chance of
> > > indenting the bridge.
> > 
> > 
> 
>