Maximum tension

[Paul]

Richard
These were copper wound bicords.  Also, I have a client with a Knabe grand
that shows a long history of string breakage, twice for me, randomly across
the scale. This grand has the steep shelf  in front of the agraffs to the
tuning pins. Thanks for your replies.

Paul Chick

----- Original Message -----
From: Richard Moody <remoody@midstatesd.net>
To: <pianotech@ptg.org>
Sent: Sunday, June 04, 2000 12:58 PM
Subject: Re: Maximum tension


> You can change the guage to lower the breaking point.  The thinner the
wire,
> the less tension needed to pull it to the desired pitch.   The fact that
> strings break *around* the same pitch for all sizes (at the same length)
is
> for curiosity rather then design. Besides design should be based around
> elasticity limits, not breaking points.  If length alone dictated scale,
> considering spinets and concert grands, one or the other could not exist.
> (although for both spinets and concert grands the highest notes have
roughly
> the same length for a while, so Newton's observations apply there) But for
> the notes you mention, measure the length and guage, compute the tension,
> then  choose the guage that gives the  tension at least a semitone below
the
> elasticity limit. Make that two semitones  + since there are reports of
> pianos changing a semitone through humidy  alone.  Now if they keep
breaking
> at the upper bearing, and the tension is under 200 #  then you might have
> too sharp of a bearing point.  Still though the elasticity limit of the
core
> wire should be known.  Were these aluminum wrapped in that
erett?   ---ric
>
> ----- Original Message -----
> From: Paul <tunenbww@clear.lakes.com>
> To: <pianotech@ptg.org>
> Sent: Saturday, June 03, 2000 7:47 AM
> Subject: Re: Maximum tension
>
>
> > Nweton
> > Would this explain why, for no apparent reason, strings in a section of
a
> > well known piano i.e. Everett studio has strings breaking in the bicord
> > section during tuning and playing? Several tuners had a crack at this
> piano
> > and, finally the dealer replaced it with another one and no more
problems.
> > But I've often wondered if increased string length due to poor bridge
> > placement was the problem.
> >
> > Paul Chick
> >
> > Newton wrote:
> > > The point of this is that if the speaking length is too long
> > > for a given pitch  changing the wire size will not change at
> > > which pitch the string breaks.
> > >
> > >  It was discovered that the bridges were located too far from
> > > the capo bar so the tension was way past safe breaking %.
> > > Changing string sizes would not have solved this problem
> > > either.  The manufacturer had to change the design.
> > >
>
>