String vibrations (was Re: Stuart)

[Phillip Ford]

>  I dont know Phil, but it seems fairly intuitive that a pulse, or wave... or
>however you want to conceptualize it... traveling down a wire and hitting an
>end point is going to tend to get deflected by the condition of that endpoint.
>If its angled as the bridge pins are, it would seem reasonable to assume that
>there will be some degree of force exerted on the vibrating string on that
>angle.. How much is another matter altogether... but its rather hard to
>disregard the data Wapin has assembled on the subject.
>
>I was under the impression that Wapins bridge was conducive to 
>vibration in the
>vertical direction, not horizontal. If Rons statement  is true, then the whole
>thing becomes just that more interesting... and as I said a bit back... it
>would be nice to see the same kind of frequency data on the Stuart as is
>available for the Wapin for comparison
>
>RicB

Before we get too far down the rabbit hole may I say that the only 
point that I was trying to make is that it is not possible (according 
to my interpretation of the physics) to confine the string vibration 
to a single plane.  As to whether these two practitioners are in fact 
making that claim I offer this:

 From the Stuart website - 'The challenge of applying contemporary 
design and technology to the evolution of the piano inspired the 
invention of the bridge agraffe. This sophisticated string coupling 
device is designed to retain the vertical mode of vibration produced 
when the hammer strikes the string'.

Leaving aside the preposterous claim that he invented the bridge 
agraffe (perhaps he means that he invented his particular version of 
a bridge agraffe), I read this as saying he believes his system 
causes the string to vibrate only in a vertical plane.

 From the Wapin patent (6,100,457) - 'Although the nature of the 
mechanical coupling between the strings, bridge structures and 
soundboard  and its influence on tone
quality is not fully understood, and not intending to be bound by any 
particular theory herein, it is believed that the perceptible sustain 
time of an excited string in an arrangement
incorporating the present invention is effectively and perceptively 
longer than a comparable string whose speaking length is terminated 
by a bridge structure having a first
bridge pin which is not substantially perpendicular, as defined 
herein. It is further believed that the fundamental frequency of an 
excited string in an arrangement incorporating
the present invention may have a greater amplitude than its first 
overtone when compared to a comparable string which is not 
substantially perpendicular.

It is further contemplated that the above-described benefits of a 
substantially perpendicular first bridge pin are derived from an 
increase in the amount of a string's initial
vibrational energy in a plane generally parallel to the soundboard 
(i.e., generally perpendicular to a first bridge pin incorporating 
the present invention). Because the mechanical
impedance in the plane parallel to the soundboard is high relative to 
the mechanical impedance in the plane perpendicular to the 
soundboard, a string's vibrational energy is
dissipated largely in the perpendicular plane. As such, it is 
contemplated that the present arrangement places more energy into a 
plane which is parallel to the soundboard and
produces a tone with a longer decay time because more energy is 
initially "stored" for later dissipation in the perpendicular plane'.

So, as I read this the Wapin folks are not claiming to confine the 
string vibration strictly to the horizontal plane.  Actually, 
compared to the outlandish claims one often sees in patents and the 
know-it-all 'this is the way things work' attitude that often obtains 
in discussions about pianos, their patent is refreshingly restrained.

Comments about Wapin in a separate post.

Regards,

Phil Ford