Piano wire tensile strength

[Delwin D Fandrich]

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From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf Of
PAULREVENKOJONES@aol.com
Sent: June 25, 2005 2:08 PM
To: pianotech@ptg.org
Subject: Re: Piano wire tensile strength


In a message dated 6/25/2005 2:30:14 PM Central Standard Time,
fandrich@pianobuilders.com writes:



I just read something in an old report I've been looking at that strikes me as
odd. Basically it says that piano builders put as many as three or four twists
in bass strings to increase the tensile strength of the core wire. 

Does this ring any bells? Does anyone know of a piano manufacturer doing this
(twisting bass strings this much)? Is anyone out there metallurgist enough to
know if there is any validity to this claim?




Del:

I've talked with only one older factory stringer (he's unfortunately dead now so
confirmation isn't possible) who claimed that he put 3-4 twists in bass strings
only to tighten the coils on the wire to avoid buzzing as the core stretched. Of
course the tension on the coils will release slightly as well, but I can't
figure how tensile strength (either overall or in the components --copper or
steel) would be increased by twisting which shortens the wire and would cause
the need for slightly lower tensions to account for the difference for pitch. Or
do I have that backwards? The ductility of copper doesn't argue logically for
higher tensile strength except for the stiffening that results from stretching a
wire as in lead in stained glass windows which visibly stiffens when stretched;
but that is not for tensile strength, more for shearing strength. The same
observation would hold for steel as well?

Paul R-J 

 
I have heard that some factory stringers tend to put a couple of twists on the
bass strings but they have always said it was to prevent buzzing strings from
certain string makers. This was especially true as string lathe speeds started
reaching up into the stratosphere.
 
Never before have I heard it said it would increase tensile strength. 
 
Del

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