Another possibility, if the Grotrian was made
around the seventies, is that the bridge was
designed with insufficient spacing between the
unisons. This problem results in insufficient
wood around the pins to properly support the side
bearing forces. With an example I have
experienced, several unison strings are so close
to the pin of its neighbouring unison that noise
(metallic in character) is generated at the
bridge during heavier playing. The source of this
noise can be confirmed by holding a blade
screwdriver between the suspect bridge pins.
In 1988 one of my clients purchased a new bridge
cap from the factory for his Grotrian 223 grand
when he visited Germany. In hindsight, I wish we
had ditched the replacement cap and laid out a
new design. But its easy to be wise after the
event. When my clients son inherits the piano
there are plans to recap the bridge again, but
the board is starting to exhibit symptoms of
failure, so it could end up being a total board
redesign.
Ron O.
>On 10/16/2010 1:43 PM, Robert Callaghan wrote:
>
>>It is a Grotrian grand and has a beautiful sound with all
>>types of playing except this one note on heavy playing. I began to
>>suspect the bridge cap, but this sound is metallic.
>
>Three things. Is the slant of the speaking
>length bridge pin around 20°, or nearly
>vertical? Is the string offset angle across the
>bridge top around 10°, or nearly straight (I'm
>guessing nearly straight, from the description)?
>Is the downbearing angle there positive, if
>there is any?
>
>Sounds to me like the string is slapping the
>bridge pin from lack of, at least, side bearing.
>Ron N
--
OVERS PIANOS - SYDNEY
Grand Piano Manufacturers
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Web http://overspianos.com.au
mailto:ron at overspianos.com.au
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