stretching wire

[Ron Nossaman]

> Not to be argumentative, but just want to be clear.  What happens when 
> the string deflects under load, mashed bridge cap or not?  Wouldn't the 
> string have to stretch in order to be deflected?  

Of course, but not permanently, unless you put so much 
pressure on it that you damage it. Otherwise it springs back.


>Does the string have 
> to stretch to be tuned?  Are you simply saying that once tensioned and 
> in a static state, the string does not passively stretch, but rather the 
> bends around it's bearing points continue to change?  If we add more 
> tension to it, or deflect it with the pizza wheel, then it will stretch, 
> up to it's elastic limit, yes?  If no, what accounts for string deflection?
> 
> Thanks,
> William R. Monroe

There is no appreciable (nothing is absolute, but it's 
inconsequential) long term stretch, or creep, of piano wire 
below it's yield point tension and under around 600°F. So 
"pre-stretching" doesn't pre-stretch. It will naturally 
immediately stretch under tension within it's elastic limits, 
but long term pitch drop doesn't come from elongating wire. If 
the strings aren't forcefully bent around the bearing points, 
they will slowly do so on their own under string tension and 
play, dropping in pitch as the wire's path between bearing 
points straightens. Remember that, while the straight string 
segments are (hopefully) well below their yield point 
tensions, the bends at the bearing points have been forced 
beyond the wire's yield point in order to make the bend.
Ron N