Foundry Castings

[Delwin D Fandrich]

----- Original Message -----
From: "gordon stelter" <lclgcnp@yahoo.com>
To: <pianotech@ptg.org>
Sent: August 27, 2002 12:08 PM
Subject: Re: Foundry Castings


> According to the AS&W transcript, gray#50 is preferred
> because of tremendous compressive strength, and no
> harmonic resonance.

Maybe at the time some foundries were using #50 (the 50 referring to its
approximate breaking tensile strength) but that is not common now. Nor has
it been standard over the years. Many early plates were cast using gray iron
having a tensile strength as low as 12,000 to 13,000 psi. The last plates we
purchased were cast using gray iron with a tensile strength of approximately
24,000 to 26,000 psi. (We had no choice in this. It's what the foundry used
to cast piano plates.) Its compressive strength was approximately 2 to 2 1/2
times that. Depending on the cross-section of the member.

Contrary to popular opinion, gray iron castings do have resonances just like
other castings. Due to their high damping these resonances damp out
relatively quickly.

Del