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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Sorry, but it’s not quite a complete
enough formula for purposes of this discussion. When comparing two strings
that produce the same pitch but with different tensions, either the original
length will be different or the diameter will be different (or both), thus a similar
change in length will yield a different change in tension and thus pitch.
</span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'> </span></font></p>
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<p><font size=2 color=navy face="Times New Roman"><span style='font-size:10.0pt;
color:navy'>David Love<br>
davidlovepianos@comcast.net<br>
www.davidlovepianos.com</span></font><font color=navy><span style='color:navy'>
</span></font></p>
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<p class=MsoNormal style='margin-left:.5in'><font size=2 color=black
face=Tahoma><span style='font-size:10.0pt;font-family:Tahoma;color:windowtext'>-----Original
Message-----<br>
<b><span style='font-weight:bold'>From:</span></b> caut-bounces@ptg.org
[mailto:caut-bounces@ptg.org] <b><span style='font-weight:bold'>On Behalf Of </span></b>Richard
Brekne<br>
<b><span style='font-weight:bold'>Sent:</span></b> Sunday, June 10, 2007 4:00
AM<br>
<b><span style='font-weight:bold'>To:</span></b> caut@ptg.org<br>
<b><span style='font-weight:bold'>Subject:</span></b> [CAUT] pre-stretching new
string?</span></font></p>
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face="Times New Roman"><span style='font-size:12.0pt'> </span></font></p>
<p class=MsoNormal style='margin-left:.5in'><font size=3 color=black
face="Times New Roman"><span style='font-size:12.0pt'>The degree any string
changes tension due to a change in length to any of its segments is calculated
by the formula given by Dr. Galembo. I've posted this several times now.
Again. it is <br>
<br>
Change in Tension = (E*S*Change in Length) / Original length.<br>
<br>
Where E is Youngs modulus and S is the cross section of the string.<br>
<br>
You first figure the length change, then figure the change in tension, then add
the change of tension to the original tension... then with both the new tension
and new length you can figure change in pitch. This works for plain
wire. If you actually apply this formula find out what kinds of things
need to happen to a given string for it to experience the kind of pitch changes
we observe... you immediately see that the pitch changes we see at the tenor
bridge have no (at present) good explanation. <br>
<br>
Cheers<br>
RicB</span></font></p>
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.5in'><font size=3 color=black face="Times New Roman"><span style='font-size:
12.0pt'><br>
<br>
The degree to which a string goes out of tune will be a function of the break
point percentage (BPP) when it is at pitch (thanks Ron N. for clarifying
that). The lower the BPP, the greater the change in pitch for a given
change in length. The top end of the bass section is generally
considerably higher BPP than the low tenor, and the low tenor is usually the
lowest BPP in the entire piano and thus goes out of tune the most with seasonal
changes. <br>
<br>
David Love</span></font></p>
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