Plate Bushings - was Re: Bushing vs. bigger pin?

[Delwin D Fandrich]

----- Original Message -----
From: Farrell <mfarrel2@tampabay.rr.com>
To: <pianotech@ptg.org>
Sent: June 02, 2000 7:49 PM
Subject: Re: Plate Bushings - was Re: Bushing vs. bigger pin?


> Jim wrote:
>
> >"The sound board still has gracious plenty crown throughout the scale and
> does not touch the outer rim anywhere."
>
> Just a question regarding piano design/construction. I thought a
soundboard
> should idealy be fit snug to the outer rim.  Are not Steinways built like
> that? How else can the "sound be reflected back into the soundboard" if
the
> soundboard is not snug against the outer rim? Do you think that in cases
> where there is a gap between the soundboard edge and outer rim, the gad
> should be filled? Just curious. I hear of this "sound reflected back"
thing
> and wonder if some of that may be just bunk. Thanks for any thoughts.
>
> Terry Farrell
> Piano Tuning & Service
> Tampa, Florida
> mfarrel2@tampabay.rr.com
----------------------------------------------------------------

If I understand the reasoning behind this notion correctly -- and it is a
bit obscure -- fitting the soundboard tightly against the rim is somehow
supposed to aid in maintaining soundboard crown.

Don't think of it as energy (not sound, please) being reflected back into
the soundboard, but rather as wave energy being retained in the
soundboard -- where it can produce sound energy -- as opposed to being
transferred into, and absorbed by, the rim.  To accomplish this the rim
should be as stiff and as massive (relative to the soundboard) as is
reasonable and the soundboard should be solidly terminated at the rim.  The
soundboard is terminated at the point where it meets the inner rim at which
point it is glued to that rim.  It is the glue joint that terminates the
vibrating area of the soundboard panel.

Any gap between the edge of the soundboard panel and the outer rim is
irrelevant.  Assuming, of course, that the glue joint is secure.  Any gap
present will have no effect on either energy transfer from the soundboard to
the rim or on maintenance of soundboard crown.

Regards,

Del