Steingraeber factory pictures, bridge agraffes & adjustable vertical hitchpins

[Ric Brekne]

Hi Terry

Grin.... good question.  And as you are no doubt aware at this point 
there is a lot of speculatation about the answer but no real definitiv 
answers.  Hard to isolate the effect of the mass of these aggraffes from 
the vertical vibrational modes bit.  I did put the question directly to 
Wayne Stuart about a year ago, who btw seemed like a very nice fellow, 
and he replied simply that the concept was well researched and 
documented mathematically by CSIRO Mathematician Dr Bob Anderssen  who 
did the research and that anyone who wanted to could contact him if they 
wanted more infomation.  To quote:

    Dr Anderssen has found out how the new coupling method is
    responsible for the wonderful clarity of sound that the Stuart
    pianos produce. By exploiting existing knowledge about piano sounds
    and string vibration, some of it over two thousand years old, Dr
    Anderssen was able to build a mathematical model of the way piano
    strings vibrate. "The model reveals how, in standard grand pianos,
    the strings begin vibrating vertically but change to vibrate
    horizontally, parallel to the soundboard," Dr Anderssen says.

    "This change to a horizontal vibration makes the sound less
    harmonious." "But, in the Stuart piano, the vibrations stay in the
    vertical plane because of the special coupling method implemented by
    Stuart. This gives a more harmonious and stronger sound," he said.

Strikes me that if folks want answers to these questions then  Andersen 
is a good place to start... followed up by a good deal controlled 
testing.  Speculation... armchair or otherwise may be fun and perhaps 
even thought provoking... but it remains speculation.

Cheers
RicB



Terry Farrell writes:

How would sideways tension (I think more like intermittent point-source 
longitudinal compression) on the bridge reduce the ability for the 
soundboard to vibrate more freely? Whatever tension or compression or 
whatever forces are within the bridge - not the soundboard. How would 
what is/isn't going on in the bridge affect soundboard performance?

Terry Farrell
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