Modal Analysis

[Delwin D Fandrich]

----- Original Message -----
From: "John Delacour" <JD@Pianomaker.co.uk>
To: <pianotech@ptg.org>
Sent: December 06, 2001 12:38 AM
Subject: Re: Modal Analysis


> At 7:41 PM -0800 12/5/01, Delwin D Fandrich wrote:
>
> >I don't think so. There is more to it than just the physical load placed
on
> >the bridge. The hydraulic rams could apply the down force alright but I
> >doubt they would have the compliance (for lack of a better word) that the
> >string plane has. Specifically the effect the backscale has in
restraining
> >the motion of the soundboard assembly.
>
> That's why I included the rubber facings in the pressure strips.  The
> flexibility over a given length is a measurable quantity and could be
> closely reproduced by a proper selection of rubber thickness/hardness.
>
> JD
>

While I had never thought of using hydraulic rams for this purpose, I have
given the idea of simulating the downforce of the string plane some thought
over the years. I think--and this is based only on theory and
supposition--you might be more successful using springs of some type.
Probably coil springs. If these were mounted on some type of adjustable
ram--and here hydraulics might well work--it might be close enough to the
real thing to obtain meaningful results.

I think rubber would absorb and dissipate too much energy from the system.

You'll probably only know if you actually try it and compare your
results--those of your tests--to the results taken from the actual piano
normally strung.

Del