ribs and stuff (was alternatives.)

[Doug Richards]

Del,

I don't know if I buy that.  Is the plate in or out?  Regardless, my gut
says it would take a very large force from the pipe clamp to measure a
difference in crown.  I think the sound board is constrained all the way
around, but a force outward will not necessarily "suck" the crown out unless
the force is HUGE (my gut feel only).  

I have an idea.  Since you do soundboard replacement, I'd propose an
experiment:

1.  Take a soundboard has been crowned before installation, lay it on a flat
surface and "somehow" measure the force/deflection rate.
2.  Repeat the force/deflection measurement after the board is glued in
(with the plate installed).

3.  And since I have an outline of a soundboard for a FEA prediction for
simply supported Vs constrained, I have no excuse.  We can compare notes.

What do ya think?

Regards,
doug richards
San Jose, CA
mailto:doug.richards@quantum.com

> -----Original Message-----
> From:	Delwin D Fandrich [SMTP:pianobuilders@olynet.com]
> Sent:	Friday, December 04, 1998 6:36 PM
> To:	pianotech@ptg.org
> Subject:	Re: ribs and stuff (was alternatives.)
> 
> 
> 
> Newton Hunt wrote:
> 
> > Not if the end support moves. (soundboard end that is).
> >                 Newton
> >
> > Ron Nossaman wrote:
> >
> > > Newton,
> > >
> > > The case has nothing to do with maintaining crown. The ribs maintain
> the
> > > crown, one way or another.
> 
> ----------------------------------------------
> 
> Yup.  Even then.  You can demonstrate this for yourself by taking a pipe
> clamp
> -- the type that turns around so that you can exert force in an outward
> direction -- and positioning it so that you can spread the rim apart.
> This is
> fairly easy to do on pianos using 'select hardwood' rims.  Whatever crown
> there
> was originally in the soundboard stays there.
> 
> Del