Recrowning/bridge wedging

[Richard Moody]

Greetings Jim

	I wrote 

	>>The tuning fork
> > when struck produces an amazing amount of more volume when the
board
> > is arched, that when it is without the bow.  However there are at
> > least four problems I can think of how this model relates to the
real
> > piano. 

>From your post (see below) you have added at least four more
problems.  

However I would like to add, for those who have never seen this demo
and heard its effects, you are out in the woods (sorry I couldn't
resist) as far as the arching of soundboard material and its results
of tonal amplification. (I don't know about sustain) 

	How this relates to piano sound board construction is for those who
have attempted it. If the arch produced by the model were replicated
in piano sound boards I suspect the crown would have at least 3/8
inch. (10mm)  So much for models.  
	Speaking of attempts, what is the Golden Gate suspension bridge
idea? 

Richard Moody 





----------
> From: Jim <pianotoo@IMAP2.ASU.EDU>
> To: Richard Moody <remoody@easnetsd.com>
> Cc: pianotech@byu.edu
> Subject: Re: Recrowning/bridge wedging
> Date: Tuesday, June 03, 1997 1:45 AM
> 
> IMHO There is no relationship between the Sales Demo of a piece of
> spruce which can be put in tension and therefore amplify a tuning
fork,
> and the structure of a piano soundboard. Where is the down bearing?
> Where is the compression? Where is the maple rim comparison? Where
is
> the rib crowning? Where is the rib spacing? Where is the bridge?
> None  of it is in the Sales Demo. OK, I know it sold lots of Mason
and
> Hamlin pianos. I built a piano with a tension soundboard. It did
not
> help the sustain. I used the Golden Gate suspension bridge idea to
sell
> my idea of the piano soundboard. Salesmanship is one thing, Piano
> construction is an entirely different thing.
> 
> Jim Coleman, Sr.
> 
> 
> On Mon, 2 Jun 1997, Richard Moody wrote:
> 
> > 
> > 
> > ----------
> > From: Ron Nossaman <nossaman@southwind.net>
> > To: pianotech@byu.edu
> > Subject: Re: Recrowning/bridge wedging
> > Date: Sunday, June 01, 1997 11:43 AM
> > 
> > 	The purpose of the crown is to put the wood under tension. It 
has
> > nothing to do with bearing.  The sound board is crowned,
installed
> > into the piano , and then the bridge installed, then the bearing
set.
> >  However this varies from factory to factory is probably due to
trade
> > secrets.  The sound board must maintain this tension, as
established
> > by its crown through variations of humidity, temperature, and
time. 
> > ( and I suppose usage might figure in ) .  
> > 	The main purpose of bearing in most stringed instruments is to
> > prevent strings from rattling on the bridge.  However in a piano
with
> > dual bridge pins less bearing is needed especially considering
the
> > tension of the strings. This has to be because if the bridge were
> > like a harpsichord's, the bearing would destroy the sound board
> > before the first chip was completed. In the end, for pianos, the
> > bearing must not be so much that it destroys the crown.
> > 	To demonstrate the effects of this tension in the wood produced
by
> > crown there is a  model consisting of a piece of soundboard with
a
> > tuning fork mounted in the middle. The board is about 18 inches
long,
> > and 5 inches wide. On each end are two blocks. When these blocks
are
> > squeezed together the board bows, or gets a crown. The tuning
fork
> > when struck produces an amazing amount of more volume when the
board
> > is arched, that when it is without the bow.  However there are at
> > least four problems I can think of how this model relates to the
real
> > piano. But that is for another thread.  It is a given fact of
nature
> > that an arched piece of wood amplifies sound much more than the
same
> > piece with out an arch.
> > 
> > 
> > 
> > . 
> > 
> > 

> > 
> > The idea if wedging the bridge is to restore the arch in the
sound
> > board ala keystone fashion. However to be frank, I have not tried
> > this idea, (nor had the opportunity to do so) But I would expect
the
> > results to be as good as the technicians I have heard talking
about
> > it. 
> > 	To proove the point though, it seems that the demonstration
model
> > could be fitted with a "bridge" with a kerf in it.  A wedge could
be
> > inserted and the sound difference noted. 
> > 
> > Richard Moody 
> > 
> > 
> >