Foundry Castings

[Alan R. Barnard]

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Cast iron IS brittle but it will not deform nor compress under stress =
and tension the way steel, aluminum, and other metals do. Nor does it =
expand and contract with changing temperatures as much as other metals. =
The key point is that it holds its shape and, most important, the =
critical string length dimensions.=20

I understand that cast aluminum was tried back in the 40's or so. It =
would sure be nice to find a different, lighter, less brittle =
material--then you wouldn't need such a heavy wood frame either. Every =
time I move a piano, my thoughts stray in this direction ...

I'm guessing that a lot of the metal in the casting is just to make the =
plate "beefier" so it doesn't break so easily.=20

Alan R. Barnard
Salem, MO
  ----- Original Message -----=20
  From: Delwin D Fandrich=20
  To: pianotech@ptg.org=20
  Sent: Tuesday, August 27, 2002 1:16 PM
  Subject: Re: Foundry Castings


  And If I haven't created enough confusion yet, I'll toss out another =
one:

  Just why do we think gray iron is the best of all possible materials =
to use for piano plates anyway? What is it about gray iron that is so =
special?=20

  We say it is extremely rigid -- but it is not. It's brittle. Is this =
an advantage?

  We say it has excellent internal damping characteristics -- but is =
this an advantage? Why?

  Right off hand I can think of only two characteristics that make it a =
particularly good choice for piano plates: [1] It is easy to machine and =
[2] it is cheap. Neither of these has anything to do with its =
performance in the piano.

  Del=20




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