[pianotech] new sting broke twice

[Joseph Garrett]

Mr. Frere said: "I epoxied a bridge for an Acrosonic #293752. String #33
was broken (the
right string of G#2). I don't remember at this point if I had the broken
string to measure, or if I ordered based on the left string specs. Ordered
string from Schaff. It broke above the V-bar while bringing it up to pitch.
I could feel too much tension before it was even a semitone away. Sure
enough it snapped before it reached pitch. I spliced it - snapped again.
 
Schaff was kind enough to replace it at no charge. I figured it was a flawed
string. Again, the same exact feeling and pop. Right at the point the string
begins to coil on the pin. I could feel it coming. Probably should have
looked more closely before popping it. The string was straight, which tells
me it wasn't catching on anything. I can't imagine why the epoxied bridge
cracks should effect it. I have installed dozens of strings, and don't feel
like I did anything wrong. Could it be a whole batch of string is flawed?
 
Today I measured the left string, and it did read .001" smaller core
diameter and .002" smaller copper diameter. The length of the winding looked
good. I didn't think this is significant enough to break a string, but I'm
not sure. (It is significant enough to give a poor unison though.) I tested
the strings adjacent, lowering pitch and re-raising to see how tight they
feel - they felt normal.
 
I'm thinking of ordering from a different company, being super careful while
replacing, and seeing what happens. If it works normally, I could call
Schaff and ask for a refund. If they refuse, no big deal. However, if this
new string breaks even after being *super* careful, then I'm at a loss. I
will order based on the left string measurements, naturally.
 
Has this happened to any of you?
 
FYI the strings that broke - and yes I mic'd them before installing - were
.040 core; .118 winding; hitch to winding 5 1/8"; winding length 30 3/4".
The new string will be the same lengths but .039 core and .116 winding."

Noah,
With out dragging out my puter program and running the numbers, my
instincts tell me that Core wire is way to small. I'd normally find/design
a core of somewhere in the .045" to .043" for a winding of that overall
diameter. I suspect a screw up on the part of the original manufacturer.
You, unwittingly had Schaff duplicate the mistake. That's my take on it w/o
actually running the numbers.
Joe
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Joe Garrett, R.P.T.
Captain of the Tool Police
Squares R I