Pertaining to bridges/ unisons/ etd/

[John Meulendijks]

I had been thinking of this possible damping effect on the bridge of the
mutes. I cannot think it is substantial compared to the forces we deal with.
But reading your notes I consider the damping effect differently: Thanks.
The idea is that the coupling is damped by the dead but not immobile
strings. It is substantially damped with two strings muted: the two muted
strings are relatively free in motion apart from being damped by one
another. It is less substantially damped when the mute is place between two
chorusses (word? I mean sets of strings belonging to one tone/ note) And at
the same time: the third string is damped firmly. That is why this third
string is not (measurable)decoupling the unison of two strings.
It's a thesis.
Give it a thought and a test: Take a mute, cut it's end  and place it
between two chorusses. It should not touch the soundboard now. Measure
possible pitch drop/ raises........ (I hate ETD's because of the time they
take to correct them/ me/ the piano, so I don't have one.)

 I cannot find anymore who asked : 'and what about striking the key harder:
That doesn't lower the pitch like in the the idea of virtually longer
strings has to be expected.' O.k. but that is because the bigger the
amplitude of the string, the bigger the tension, and the higher the pitch
is. (temporarily)

yet another test: is the left pedal use of a grand leading to simular pitch
lowering/ raising effects? (Especially when it is set to far and only two
strings are hit.)


John Meulendijks
Tilburg The Netherlands


----- Original Message -----
From: Richard Brekne <Richard.Brekne@grieg.uib.no>
To: PTG <pianotech@ptg.org>
Sent: Friday, February 16, 2001 9:34 PM
Subject: Pertaining to bridges


> This thread on Virgils beats, ETD question and related stuff
> prompts me to aks a question of our rebuilders who are familiar
> with this stuff about bridges.
>
> Also... Weinreich talks about the impedance from the bridge
> having three main possible characters. Massy, Springy, and
> Resistive. Are these to anydegree something one can design into a
> bridge / soundboard  assembly ?
>
> To mind pops up Ron Overs recent postings on the orientation of
> bridge wood grain relating to supporting bridge pins... how does
> grain orientation fit in (if at all) with impedance charachter ?
> For that matter... loose bridge pins themselves.  Would seem to
> me that a bridge pin that can give a bit sideways would tend to
> effect the whole assembly (for affected notes) in the direction
> of being springy...which in turn tend to lend itself towards
> pitch drop.
>
> Another thing that I am a bit foggy on here is how exactly does
> coupling in more strings exasperate these three conditions ? Take
> for example a springy termination. Muting the string would tend
> to hold the bridge a bit stiffer right ? .... aslo increasing
> impedance seen by the string allowed to vibrate.. and releasing
> the muted string then releases that stiffening effect on the
> bridge... with a resultant decrease in impedance seen by the
> first string.  But this affects only the amount of apparant
> bridge impedance... not its character ??? or does it also
> compound or otherwise effect the character of impedance ??
>
> Anybody want to clear this up for me ??
>
> Or is my mind
>
> --
> Richard Brekne
> RPT, N.P.T.F.
> Bergen, Norway
> mailto:Richard.Brekne@grieg.uib.no
>
>