pre stretched strings

[KUANG]

Hi Mr. Moody and list:

> >
> > > An interesting idea pre-stretched strings.  However the debate is
> "is
> > > it stretch or is it bends"? that causes a new piano string to be
> so
> > > unstable at first, and then in good 80 old pianos be so bad for
> > > business.  In "stretching" a new wire with the grooved or roller
> > > tools, screw drivers or whatever,  there is the risk of damage to
> the
> > > notches at the bridge pins., and also of stretching the string
> > > (especially its bend) beyond its limit of elasticity.
> Certainly
> > > when observing the seating  marks on a bridge with the strings
> > > removed, a lot of variation can be seen. I wouldn't want to be
> the
> > > cause of it, especially those "fan" shaped grooves.  Some one
> > > mentioned a dent in the bridge pin.  I am wondering since all the
> > > strings swagger, shouldn't all the pins have a dent?  Or only
> those
> > > whose strings got stretched?  I have not looked for that before.
>
> > > 	 Any how the theory that it is the bends in the strings that
> take a
> > > while to form makes sense to me.  After all if a piano string
> > > "stretches" how can it do so and not violate the laws of
> elasticity?

A piano string stretches because it's under a constant tension.  The rate
at which it streches depends on the material, temperature, tension and the
relative length it already has streched (plus other factor(s) I missed?).
Of course, the longer it has stretched, the slower it stretches further.
And when the rate at which it streches reaches about zero, it will lose
its elasticity and breaks (the elasticity decreases as the string
stretches, does this make sense?). A pre-stretched string should be a
string that has a much slower rate of stretching than a new string.  It
doesn't mean that it's fully stretched and thus lost its elasticity (who
would buy them anyway :) ) - it means it has been stretched by a certain
fraction of length.
Something is "elastic" if the material can be compressed and stretched.
When a wire is bent, one side is stretched and other side is compressed.
I believe it's easier to stretch metals than to compress it, I could be
wrong (isn't that because metallic bonds are much shorter?).
	A string breaks at striking point because the rate of stretching
is faster there due to frequent striking _and_ higher local temperature
(the temperature at that point of the string).


> > > And look at the bends the wire goes through, at least six, or
> seven
> > > if you count the becket.  It would be impossible to prestretch a
> > > piano string if these bends are the culprit in causing new piano
> wire
> > > to go out of tune so fast.
> > > 	So that is why a tied string is so much more stable in tuning
> than a
> > > new string, the bends are already there, at least four of  them.
Also, the old string sounds more uniform :)

> > > Those that have used the same (treble) wire that broke at the pin
> by
> > > settling for one and a half turns would know for sure. That's
> eight
> > > new bends on pre stretched wire.  And no I don't think that's why
> > > Steinway used to put four turns on their upper pins, or maybe
> they
> > > still do. ; )
> > > Richard Moody
> > >
> > > ----------
> > > > From: KUANG <v137z2ng@ubvms.cc.buffalo.edu>
> > > > To: pianotech@byu.edu
> > > > Cc: pianotech@byu.edu
> > > > Subject: Re: Tying knots (was Re: lifetime job?)
> > > > Date: Thursday, April 10, 1997 11:12 AM
> > > >
> > > >
> > > >
> > >
> > > > I was thinking if any supply house stock "pre-streched" wire?
> > > Maybe
> > > > there's no such thing?  Wouldn't it be very expansive to supply
> > > those
> > > > kind of wire?  I know at least one violinist who always put new
>
> > > > violin strings on her second violin so whenever she needs new
> > > strings,
> > > > the strings would be "ready" to play.
> > > >
> > >
> > >
> > >
>
Sincerely,
Kuang