Soundboards/stress

[Rob Kiddell]

Jim Coleman Sr. wrote:

> There is an almost right angle caul to which the Bass and front edge of
> soundboard is fitted to on the glue-up press. A curved fitted caul is
> placed around the curves side of the board. This caul is squeezed about
> 1/8 inch to put pressure across grain while the board is being held down
> by 2 or 3 unglued ribs while the others are being glued and set with the
> go-bars. Mind you, this was the system use back in the early 70's. I
> think they may have done away with go-bars by now. This system was 
> used on all of the small grands. You are right that the ribs were flat 
> and the table was flat. The 7' and 9' grands were pressed in curved
> cauls using pneumatic pressure on each curved rib in a controlled
> environment. I can't remember if these had cross grain pressure applied
> while gluing up.
> 
> Jim Coleman, Sr.

Jim, 

	I was at the Conway Baldwin grand plant in April, and all the 
soundboards they produce there are done in the curved caul/pneumatic 
pressure jigs in the gluing room. This applies to all the Artist 
Series grands, M 5'2" to SD-10 9'. However, I can't vouch for the 
vertical pianos or the Chickering 507 grand  series produced in 
Trumann. 
	Tommy Edgeman, the production manager, said that the boards were 
"crowned in the traditional manner", but he didn't elaborate (and I 
didn't think about this at the  time).  Just what would a 
"traditional" crowning technique mean, versus a "modern" technique?

Regards, 

Rob Kiddell
R.P.T., P.T.G.
C.A.P.T. Student
Edmonton, Canada
http://www.planet.eon.net/~atonal/atonal.html