> From: "Robert W.Hohf" <rhohf@idcnet.com> > To: "pianotech@ptg.org" <pianotech@ptg.org> > Subject: RE: Singing Strut > Date: Sun, 23 Nov 1997 19:24:27 -0600 > Reply-to: pianotech@ptg.org Now that is interesting...I thought that cast iron naturally had a high level of graphite/carbon in it. I didn't know? it was added for piano manufacturing. Is this really true? David ilvedson, RPT Pacifica, CA > > > A number of years ago I attended a very interesting and informative class > given by Henry(?) Wickham of the now defunct Wickham Foundry. One of the > topics he covered was how the composition of the iron effects the resonance > of the casting. Here is what I recall him saying (FWIW): it is the > addition of carbon to the iron which reduces the resonance. It seems that > one of the difficulties in the casting process is keeping the carbon > uniformly distributed in the molten metal. When enough carbon migrates out > of a strut, the strut can sometimes resonate at a distinct frequency. If > this is true (it's been quite a few years), it would seem to indicate that > a "singing strut" is not necessarily due to faulty design, but possibly > faulty casting. However, none of this helps to solve the problem. > > Bob Hohf > Wisconsin > > >
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