string breaking test

[Isaac OLEG]

The way the tension is applied, is the string pre tensioned first and
leaved for some time before the test, and other parameters influence
the test results more than a little, been said.

That is why test are made more or less 10 times for each gauge to be
relatively accurate (and evened).

What counts more than the breaking strain is the limit of the elastic
zone.

Another fact I was explained is that during the breaking test, the
wire actually show a different breaking strain than in real, while I
don't recall the exact explanation why, it have to do with the
reaction of the metal before the break, while the length augmentation
became non linear (the upper part of the curve) that should say that
the wire really break at a lower tension than its real breaking strain
I guess.

Forwarded that to Stephen Paulello for other ideas.

Actually, test made on Stephen's  modern type wire showed that the
elastic limit was at 92% which may be a good thing. Nowadays I like
their timber a lot.

I still have to wait for a few weeks to have final results, as the
wire stiffen with time differently than Roslau (I am mounting them and
mixing, in a little grand). For the moment I like the warmness and the
open power of those strings, they are pleasing to my ears, nowadays,
the projection is different from Roslau, as the stiffness. I hope I'll
be as enthusiastic with the finished piano - I'll keep you posted...

Isaac OLEG
------------------------------------
Isaac OLEG
accordeur - reparateur - concert
oleg-i@noos.fr
19 rue Jules Ferry
94400 VITRY sur SEINE
tel: 033 01 47 18 06 98
fax: 33 01 47 18 06 90
mobile: 033 06 60 42 58 77
------------------------------------


Hope that helps


> -----Message d'origine-----
> De : pianotech-bounces@ptg.org
> [mailto:pianotech-bounces@ptg.org]De la
> part de Stéphane Collin
> Envoyé : mardi 2 mars 2004 20:45
> À : Pianotech
> Objet : string breaking test
>
>
> Hello all.
>
> I just made some strings breaking tests, and am a bit in trouble.
> Have that beautiful Bechstein model IV in mint condition,
> from 1870, with I
> believe original strings on it.
> Asked a friend (engineer) to do the breaking tests on that
> wire, and at the
> same time, do the same tests on modern wire.  Both tests
> led to this numbers
> :  1870 wire breaks at about 1500 N/mm² and modern (2000)
> wire (Röslau) :
> exactly the same.
> Good news : I can restring that 1870 piano with modern wire.
> Bad news : when I read Stephen Paulello papers, the numbers
> don't match at
> all : he says modern wire should break at something between
> 1800 and 2200
> N/m².
> Any comments ?
>
> Stéphane Collin
>
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