Currier Composite Plate (was self tuning piano????)

[Delwin D Fandrich]

----- Original Message -----
From: "Phillip Ford" <fordpiano@earthlink.net>
To: "pianotech" <pianotech@ptg.org>
Sent: July 03, 2002 10:41 AM
Subject: Currier Composite Plate (was self tuning piano????)


> Del,
>
> Could you expand on this a bit?  Why was this piano untunable?  What could
> have been done to correct the design?

The tuning pins were spread quite some distance apart, especially so in the
treble. For example, at C-88 the lower (right hand) pin was located about
where you would expect it, just above the pressure bar. The upper (left
hand) pin was a foot or so above this. It took quite a bit of pin rotation
to get the speaking length to change pitch, then it would invariably
overshoot. Impossible and frustrating.

I assume this was done to spread the load out a bit, though I don't really
know if this was necessary. According to the engineer I talked with it was
never tried any other way; there was just an assumption that this would be
necessary as it would be in an aircraft load-bearing structure. The tuning
problem pretty much insured the failure of the project before there was any
chance to discover and solve any other problems that might have been endemic
to the design. Too bad, it looked like an idea with lots of possibilities
and potential.



>
> On a related subject - I don't have
> personal experience with pianos with aluminum plates but I've heard that
> pianos that were manufactured with aluminum plates had tuning stability
> problems.  Do you know the cause of this?

I don't have any personal experience with them either. My guess is that they
flexed quite a bit during the tuning process and they probably never did
stop bending under stress.

In addition to this problem, I have read that there was a sustain problem
associated to the use of aluminum in the plate. Too little mass to keep
hitchpins, etc., from vibrating and absorbing energy from the strings.

Del