[CAUT] Gravalla Tension regulator

[Scott E. Thile]

Interesting article, Ron. I stand corrected in terms of the direction of the
forces at play... 

It would be interesting to know what would happen in your model if the board
were glued into the jig like it would be in the piano. I suspect capturing
the board by gluing it down (after it's crowned) could still contribute to
resisting forces by preventing the ends from moving as freely (regardless of
the direction). 

Even if stiffness of the rim assembly does not contribute to retention of
the crown and/or downbearing, it does effect tone production. My experience
is the effects are dramatic, especially in projection, and especially in the
"killer octave".  My point is that regardless of the effects of maintaining
crown, stiffness in the rim assembly seems to be is an important factor.

Back to the original question. I like the wood stiffener as well as the
other method's Steinway uses to achieve stiffness in the assembly. That
stiffener would appear to be an attempt to address the killer octave, and I
think it works. I recently rebuilt a D with a new board, and I replaced that
little stiffener, as well as lots of other work to rim and braces, which had
been significantly compromised in order to include an M&H tensioner at one
point. It's hard to know if any of that contributes to the success of this
piano or it's just benefiting from the new healthy board.

Steinway's methods of stiffening the assembly seem to work really well, and
they seem to hold up at least as well over time as other methods. I would
not want to eliminate one of them in order to install another....

In pianos, Scott
Murray State, Murray, KY

> -----Original Message-----
> From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On 
> Behalf Of Ron Nossaman
> Sent: Monday, September 24, 2007 10:26 PM
> To: College and University Technicians
> Subject: Re: [CAUT] Gravalla Tension regulator
> 
> 
> 
> > The piece that is in there is intended to stiffen the belly 
> rail, and 
> > it works. My understanding is that it is under tension as 
> opposed to 
> > compression. It's pulled end to end as it holds the bell rail from 
> > pushing out under the down bearing on the board. If you 
> picture that 
> > it's easier to understand it's size than if your thinking 
> compression 
> > like the beams.
> 
> The belly rail won't push out from downbearing load. If 
> anything, it'll pull in. Soundboard crown isn't an arch. See 
> April 2006 Journal, "Rib crown as an End-Buttressed Arch".
> 
> Ron N