Scale tension

[Newton Hunt]

First there is hammer weight.  Heavier hammers, even a little, will
effect the impact on the strings.

Next is metal fatigue.  Those string would likely have gone very soon
with the original hammers.  Metal fatigue is a fact of life and is
caused by multiple tunings, hammer impact and lots and lots of playing. 
Absolutely no way to avoid metal fatigue.

Then there is tuning.  Tuning stresses the stings quit a bit, friction
bearing points, etc., etc., and there is little to be done about that. 
ust know that you will have to restring the pianos every ten to thirty
years, especially in a school environment.

		Newton

> After voicing (which required a bit of juice in the top octave) and a bit
> of shaping there have been no more string breakage.
> 
> So ....like Wim asks... what causes the strings to break ?
>