Rib overkill

[Delwin D Fandrich]

----- Original Message -----
From: "Sarah Fox" <sarah@gendernet.org>
To: "Pianotech" <pianotech@ptg.org>
Sent: July 28, 2003 12:10 AM
Subject: Re: Rib overkill


> Hi all,
>
> Dumb question:
>
> In a rib-crowned soundboard, the spring action is in the rib.  However,
ribs
> are made of wood, and wood eventually loses shape under constant
pressure.
> There have been experiments with steel soundboards, which don't quite
sound
> right in the treble end.  But what about spring steel ribs of some sort?
> Perhaps thin wooden ribs with steel leaf springs screwed to them, affixed
> with a flexible adhesive to prevent buzzing.  They wouldn't lose their
> shape, for the most part, and could be engineered to whatever spring
> constant is desired.

Lot's more things to go wrong. Besides, in a rib-crowned soundboard system
the ribs are quite long-lived. The stresses are moderate compression along
the top of the rib and moderate tension along the bottom. This is what the
wood fibers were created for and they handle the stresses quite well and
for quite a long time.


>
> A related dumb question:
>
> When the treble needs stiffening (higher acoustic impedance and lower
> compliance), that would be achieved by raising the spring constant.  Why
not
> do that with coil assist springs between a frame element and the
underside
> of the SB beneath the bridge?  An added benefit would be the offloading
of
> downbearing pressure that otherwise distorts the crown over time.  (The
same
> downbearing is preserved between the string and bridge, insuring the same
> efficacy of vibrational coupling.)
>
> Has anyone tried anything like this?

Yes. There are several exchanges in the archives on this subject. There is
not a large base of information as yet but it has been done with at least
mixed results. That is to say, sometimes positive results, sometimes none.
But at least none negative. (To the best of my knowledge.)

Del
Delwin D Fandrich
Piano Designer & Builder
Hoquiam, Washington  USA
E.mail:  pianobuilders@olynet.com
Web Site:  www.pianobuilders.com