Elastic limits,

[Ron Nossaman]

Hi Ed and all,

The elastic limit (or plastic deformation limit) was exceeded at every point that a permanent bend was made in every wire in a piano. Elasticity in these regions drops drastically as a result. The crystal structure of the steel changes, and it "work harde
ns" (same thing). This HAS to increase the likelihood of breakage in these areas. You're dead center. This is part of the answer.

PS: I have bark scars on my forehead too. <G>


Ron Nossaman


At 07:41 AM 4/26/97 -0400, you wrote:

>
>     I would suggest,  that breakage is usually caused by the elastic limit
>being  well surpassed on the outside of the curve of the wire, where it goes
>around the agraffe, or V-bar.  This outer circumference  is the place where
>breaks begin.  If the string is put near it's break limit, and then forced to
>bend,  the wire will micro-fracture on the outside bend.  If these fractures
>continue, they effectively reduce the diameter of the string at this site,
>and the breaking tension for this site is reduced.  Eventually,  that limit
>will decrease to the tension used in play, or tuning, and the string will
>break at it's weakest section.   I believe that this is the reason for the
>propensity of steeply angled strings to break, rather than the excessive
>friction generated by the sharpness of the turn.
>     But perhaps I am totally missing something here,   ( I have found a
>forest before by walking into a tree......)
>
>Regards,
>Ed Foote
>Precision Piano Works
>Nashville, Tn.
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> Ron Nossaman