Spurlock shimming method.

[Delwin D Fandrich]

----- Original Message -----
From: "Overs Pianos" <sec@overspianos.com.au>
To: <pianotech@ptg.org>
Sent: May 10, 2001 7:13 AM
Subject: Re: Re: Spurlock shimming method.


> >How can anybody really believe there is
> >enough rigidity in that rim to resist that 0.21 mm expansion?
>
> Your criticism of the Koreans for using 'select hardwood' is well
> known, and I can only concur with your opinion. However, that rim to
> which you refer has an inner rim thickness of 45 mm, with an outer of
> 26, and while the standard Samick grand piano rims are manufactured
> with substandard less dense timbers, the WFG series grands (according
> to the Samick website) use maple. It is probably reasonable to assume
> that maple continues to exhibit the same density as found when used
> by other manufacturers, when Samick use it for rim construction also.

My comment was not really a critisism of Samick. I fully understand the
necessity of using a variety of woods in piano rim construction. My real
objection to the phrase 'select hardwood' is with the double-speak used to
make the selection of a light-weight, easily bendable wood -- chosen for
legitimate manufacturing needs -- sound like something it is not.

I only brought it up to point out that the rim is not going to support
crown.



> >Hence the difference
> >between the chord length and the arc length will also be considerably
less.
> >Remember also that a fair number of these ribs terminate on the
bellyrail,
> >all of which are notorious for their flexibility.
>
> But need not be if they were fixed at say two points along their
> length (as in Welmar pianos) to the plate and were made of suitably
> dense timber.

Even suitably dense timbers undergo compression set.



> >The best argument given so far discounting the whole notion of the rim
> >supporting crown is given above where you point out that when you lean
> >against the rim of the piano the crown of the board changes. And this is
the
> >same rim that is supposed to be supporting crown by virtue of its
absolute
> >rigidity?
>
> Sure, but the words 'absolute rigidity' are yours not mine. I too can
> understand that a rim may give way, especially since most pianos are
> ineffectively cross braced. But an understanding of simple
> engineering principles must lead me to suspect that an arched sound
> board which has not gone flat and remains attached to a substantial
> rim must be getting, OK just a tiny bit of support. While I don't
> doubt your experience with sound board technology, you must concede
> that however weak the spruce and low the arch of the panel, it still
> has to be pushed and wont just fall straight - at least not in the
> short term.

Yes. And when I jump straight up I will move the earth away from me just a
tiny bit. I doubt that you'll notice, but an understanding of simple
engineering principles assures me that this is so.

Regards,

Del