Singing Strut

[David ilvedson]

> 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
> 
> 
>