rim supported soundboards tesnion resonator rods

[Brian Trout]

I really have serious doubts in my mind about the validity of the little
demonstration at the conventions, you know the one where they take the
little stick of spruce between secure ends, have a little crown bent in it
at rest between those ends, and insert a business card at one of those ends
and show how much more crown has happened in that little stick of spruce.

It's a fun little thing to show, but I really don't know how much that
concept, the arch supported crown, bears any similarity in a piano.

Just a couple of things that come to mind.  That ain't much of an arch!
Seriously, if you want to get into measuring things, measure how long the
soundboard is across the length of that crown, and then measure how long
that soundboard is across the same length without the crown.  It ain't a
whole lot different.  And for those who work with soundboards, as in shaping
and building, do you realize how soft even Sitka spruce is?  All you have to
do is drop a pencil on it while you're working over it and there's a dent in
it!  Spruce is soft.  And it will compress, especially under the load of a
half ton or so of downbearing.  (This might be another place to put in a
little plug for rib supported crown!)  Any difference that the ol' tension
resonator might make in the actual crown of the board, I would think, would
probably be temporary at best.

All that being said, I do like the 'tension resonator' that M & H used(s?).
I think it makes for a very solid support system for the rim by tying it all
together very solidly.  And I suspect that THAT is one of the things that
makes these pianos so wonderful to work with.  The more solid the rim of a
piano, the better termination that soundboard has as it attaches to the rim.
This is a good thing!  Ya know, I'd love to hear what a piano made out of a
concrete rim would sound like.  Only thing, I have a feeling we'd have
trouble finding piano movers!

'Nuff comments from the peanut gallery.  (Just some random thoughts
anyway...)

Have a good day, folks!

Brian Trout
Quarryville, PA
btrout@desupernet.net




----- Original Message -----
From: "Richard Moody" <remoody@midstatesd.net>
To: "piano tech" <pianotech@ptg.org>
Sent: Tuesday, February 06, 2001 1:42 AM
Subject: rim supported soundboards tesnion resonator rods


>
>
>
> >But certainly if the rim did spread out a bit, it would tend to flatten
the
> >board. So I should think the rods would help maintain crown. Yes? No?
>
> No.
>
............................................................................
....
> ....................................
>
>
> There is nothing preventing piano makers from using the rim to support a
crown.
> Whether it worked or not is another story.  Yet according to Dolge, the
"Tension
> Resonator" patents of Richard Gerz in 1900 were supposed to do just that.
>
> "...the purport of which is to regulate the pressure in the arch of the
> soundboard against the strings and to assist the vibratory efficiency of
the
> entire soundboard......    Another function of this resonator is to
restore the
> original arched form of the soundboard....[to]draw together the entire rim
upon
> which the soundboard is fastened, and force the latter back to its
original
> arched form, reinstating and enlivening the vibratory action of the entire
> board. ...the tension rods can be screwed up, either simultaniously to
bring
> pressure upon the entire board, or individually if any part of the
soundblard
> should show a pronounced flatness.  They are furthermore of great value in
> maintaining the correct form and shape of the rim.  This invention has
been
> applied to all the grand pianos made by Mason & Hamlin since the granting
of the
> patent. "
>         (Alfred Dolge, Pianos and Their Makers. p110)
>
>     I have heard considerable debate about what actually (if anything) was
> accomplished by the rods.  Never the less if M&H did design a rim to
support the
> sound board arch the concept was at least given a try. The interesting
part of
> the debate to me is whether this is an efficacious way of maintaining the
crown.
> I am not sure anyone knows, unless they are/have actually used it.
>     I wonder if makers have put soundboards by themselves in a room with
> variable humidity and measured dimensional changes, the arch in
> particular.  ---ric
>
>
>