Soundboardcrownpress

[Farrell]

David Hughes attempts to do this with his pneumatic soundboard press. He describes his press in a Journal article a few years back.

Terry Farrell
  
----- Original Message ----- 
From: "gordon stelter" <lclgcnp@yahoo.com>
To: "Pianotech" <pianotech@ptg.org>
Sent: Tuesday, December 17, 2002 11:54 AM
Subject: RE: Soundboardcrownpress


> Has anyone built a soundboard press/rib cutting system
> which insures that the apogee of the board's crown is
> right under the bridge, where it seems, for
> durability, stability and tone, that it ought to be?
> Due to the shape of pianos, ribs cut at a constant 
> radius and glued to the board in a constant radius
> press will place the apogee alongside the bridge, in
> many areas.
>      Is the correction of this what Chris Robinson
> refers to as the "catenary arc"?
>      When I was "laid-up" a few years ago I spent
> considerable time designing a press for this, but
> never built it. It depended upon screwing/clamping the
> bridge core to a series of "ribs" ( actually slats in
> the place of the ribs, perhaps of carbon fiber or some
> other uniform, flexible material )  then pressing upon
> the bridge core with a reverse pressure reflective of
> down bearing, so that these slats assumed a natural
> curve with the apogee at the bridge line.
>     Their ends protruded beyond a mock-up rim, and
> slid over it. Then, bolts underneath held them in
> place, or cauls could be cut to this shape. This, then
> formed the "dishing" table.
>      $10 to the first who builds this, or an
> improvement thereof.
>      Thump
> 
> --- Ron Nossaman <RNossaman@cox.net> wrote:
> > 
> > >Environment humidity was about 60%, that's normal
> > in Belgium (but after
> > >reading other mails, I think to high for gluing
> > ribs)  Concerning the
> > >humidity of the wood it self, I can't tell you.
> > >
> > >I made the board and placed it upside down (has to,
> > otherwise you will
> > >get reversed crown)  in the press for gluing on the
> > ribs. The wood of
> > >the press bends just enough when you blow the hoses
> > for receiving about
> > >1 cm of crown
> > >The strange thing is when I eye-checked it,  the
> > crown seems to have
> > >disappeared (ie, when the board came out of the
> > press, one really saw
> > >the crown) .  But now, when I'm heating it to dry
> > before gluing it in
> > >the piano, and checked it with a straight piece of
> > lumber I have crown
> > >(about 12, 13 mm) across the ribs, the highest
> > point of the board is
> > >where it has to be, and I see  a little bit of
> > negative crown along the
> > >ribs (although this could be caused from heating
> > the board, so it'll be
> > >warmer in the center as on the ends)
> > 
> > Peter,
> >  From your description, I wouldn't expect your board
> > to have done anything 
> > else but go flat when you dried it. Why would you
> > dry it to glue it in the 
> > piano when you apparently didn't to glue on the
> > ribs? I don't understand. 
> > As Del said, I hope you can get the ribs off without
> > destroying the panel 
> > so you can start over again. In the four years or so
> > that you've posted to 
> > the list, at least a month's worth of reading has
> > been posted on soundboard 
> > crowning methods and expected results. Please go
> > back and read some of this 
> > stuff, particularly the differences between rib
> > crowning and panel 
> > (compression) crowning.
> > 
> > Ron N
> > 
> > _______________________________________________
> > pianotech list info:
> https://www.moypiano.com/resources/#archives
> 
> 
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