String Breakage

[Jim Coleman, Sr.]

Hi Rhose or Tony:

When I was in Secondary School and playing in the Marching Band, I noticed
that when we turned a corner, the Band members on the outer part of our
rank had to take larger steps to stay in line and stay in rhythm. Something
similar happens as a string goes around a curve (V-bar, aggraffe, or tuning
pin). There is more forced stretching at the outer portion of the curve.
This stretching actually is forcing the yield point. Most piano wire will
yield somewhere around 90% of the breaking point. Most pianos are strung at
around 70% of the breaking point in the treble. In the Bass the percent
of break strength is much lower, but because the core wire is much larger
in diameter, there is more yielding going around the curves of the contact
points. So, even though the percent of break strength of the lowest Bass
strings may be at around 35%, the yield stress in greater. You will notice
this especially when you try to remove a string from its tuning pin in 
order to install a larger tuning pin. Unless you maintain a semblance of
tension on the string as you unwind it, the string will break at the 
beginning of the coiling. You don't even need to ask how I know.

For those few individual loose tuning pins, I would suggest that you 
use the CA glue to firm up the pins. You may need more than one treatment.
I know by personal experience that this will help. It may also prevent
over pulling the tension which caused the string breakage. There also
will be less string breakage if you use short quick jerks in pulling up 
the string rather than using the cautious smooth pull technique.

Jim Coleman, Sr.

On Mon, 8 Mar 1999, Rhose Caught wrote:

> 
> Hi List,
> 
> String breakage, I never got  all the answers on this subject so I will =
> ask, why do the strings break at the point where the wire starts curving =
> around the tuning pin?
> 
> I have a CF Yamaha in my care that is now breaking strings in the bass =
> A0, B1 & G1.  All singles. So far. All T pins are loose.
> 
> History.  The piano has been stored in  a 5% humidity environment,  the =
> tuning pins are loose some very loose, and over the last 5 years the =
> piano is constantly out of tune with pins slipping.  Constant spasmodic =
> tuning,
> 
> The owners wants to know what is the cause of the breaking strings ?  =
> What is the cause ?
> 
> I have read most of what was said on this subject but I can't recall if =
> an answer was given.
> 
> Please help me give the right information to the owners.
> 
> To me, I am querying the clues given in this thread and am offering and =
> asking for assistance in either proving or disproving the following =
> theory.
> 
> Because when piano wire is down down to the required dimension, the =
> outer part of the wire goes hard while the inner core remains softer.
> 
> 1.     Is this process work hardening the wire in a controlled process =
> and then other excessive bending causing the outer side hard wire to =
> crack.  ???
> 
> 2.    Should piano wire because of the hard outer and soft core be more =
> likened to a metal tube filled with lead.
> What would happen if you flex or bend the tube back and forth a few =
> times, would this cause the metal tube to crack. ?
> 
> I am no engineer or metallurgist but this seems feasible to me.  BUT =
> what do I tell the owners that caused the strings to break.
> 
> 
> Regards   Tony Caught  caute@accessnt.com.au
> 
> 
>