Soundboard stiffening

[gordon stelter]

Hunh? When was thelast time you compressed a spring by
hand??? Everyone I've ever compressed definitely
offers more resistance ( stiffness) the further it is
bent, or compacted.
     Twoing

--- Phillip Ford <fordpiano@earthlink.net> wrote:
> > >At the risk of oversimplification, isn't a
> crowned soundboard just a big
> > >spring, the more you compress it, the more rigid
> it becomes?
> > >
> > >David Love
> > >davidlovepianos@earthlink.net
> > >
> >
> >David,
> >
> >This is the point that I was trying to make.  I
> believe that the
> >soundboard is essentially just a big spring.  A
> spring doesn't get
> >more rigid or stiff the more you compress it. 
> Within its working
> >range it has a constant spring rate or stiffness.
> ... If the board is
> >actually getting stiffer as a result of applied
> load then it's not
> >acting like a spring or a beam, and I would like to
> understand what
> >mechanism is causing that to happen.
> >
> >Phil Ford
> >
> >   Phil
> >   If this is true then why can I measure a
> predictable amount of residual 
> > bearing at the bridge after the board is string?
> 
> You could do that whether the spring rate was linear
> or non-linear.  Let's 
> say you put on 1 1/2 degrees of bearing everywhere. 
> Let's say that the 
> bridge sinking 1/10 inch would decrease that to 1/2
> degree bearing.  Let's 
> say for the sake of argument that the spring rate of
> the board is uniformly 
> a linear 1000 lbs/in. everywhere.  Let's say total
> downward load from the 
> bearing is 100 lbs.  This would result in a
> predictable and measurable 1/2 
> degree bearing after stringing.
> 
> I don't see that the board spring rate has to be
> non-linear (the board 
> doesn't have to be stiffening as you load it) in
> order to end up with 
> bearing after stringing.
> 
> 
> >    I thinkthe boards compression rate is non
> linear. At least that's the 
> > wya it behaves in my hands.
> >    DAle
> 
> 
> You may be right.  But I'm going to have to see some
> measurements to be 
> convinced.
> 
> Phil
> 
> 
> 
> 
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