Recrowning/bridge wedging

[Jim]

Hi Richard:

The idea of the Golden Gate Supension bridge is that a thin bridge can
be suspended by cables mounted from tall towers. My idea for a soundboard
was that instead of having a crown, the soundboard would be in tension
which is a tiny bit more analogous to the tuning fork on sprung spruce
board. I reasoned then that a longer bridge supported by tension would
be more stable that a crowned board. The board was laminated bass wood.
I was quite proud of my idea (Rippen pianos used it previously) because
the argument of the suspension bridge for vehicles with all of their 
weight seemed to make sense to me when you consider all the downbearing
weight of piano strings. Unfortunately, a tensioned soundboard does not
help sustain like a compressed soundboard does. This tensioned sound-
board was introduced in the Conn C-42 scale and later was in the
Janssen pianos which were made by Conn. In the C48 scale which later
became the Walter W48 scale, the tension soundboard was abandoned and
solid spruce was again used under compression. That piano has good
sustain.

Jim Coleman, Sr.

On Tue, 3 Jun 1997, Richard Moody  wrote:

> 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 
> > > 
> > > 
> > > 
>