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<DIV><STRONG><FONT face=Arial size=2>I have this piano where every single string
is false. I know it is not the bridge pins because there are no bridge
pins. Another form of clamping the strings to the bridge is being used. (
I'll leave you to imagine what that might be.</FONT></STRONG></DIV>
<DIV><STRONG><FONT face=Arial size=2></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face=Arial size=2>Now, as for the cause, we have to start
from the very beginning. A false beat is two different frequencies produced by
the same string. To have two frequencies produced can only be caused by changes
in either the speaking length or a change in the tension of the string. What is
the actual mechanical link between a loose bridge pin and either of the above
causes? Does a loose bridge pin create changes in tension or changes in the
speaking length of the string?</FONT></STRONG></DIV>
<DIV><STRONG><FONT face=Arial size=2></FONT></STRONG> </DIV>
<DIV><STRONG><FONT face=Arial size=2>AF</FONT></STRONG></DIV>
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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: black"><B>From:</B>
<A title=ricbrek@broadpark.no href="mailto:ricbrek@broadpark.no">Ric
Brekne</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Saturday, September 09, 2006 10:57
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Bridge Seating (was Re: Where to
notch a bridge,& relative effects ????? (Advice sought)</DIV>
<DIV><BR></DIV>List:<BR>
<BLOCKQUOTE><BR>"Exactly right William, thank you. Johnathan, when you hear
a <BR>string that sounds like something you would typically seat, <BR>try
this. Place a screwdriver tip against the speaking length <BR>bridge pin of
that string, and apply a bit of pressure to the <BR>side of the pin opposite
the string. Odds are, the sound will <BR>clean up as if you'd seated the
string. Take the screwdriver <BR>away and the noise returns. Replace the
screwdriver, and the <BR>sound cleans up again. Ask yourself why that is,
when you <BR>haven't seated the string at all."<BR></BLOCKQUOTE><BR>I'd
suggest folks go a couple steps further with this advice. Ask yourself
why if you increase pressure on the screwdriver the beat starts up
again. Also actually count and write down which strings have false beats
and which of these actually reacts to the screwdriver. Then figure your
percentages. The real odds are that the percentages are somewhat more a
game of bingo then anything else. More importantly, when you are done
identifying all the strings that react to the screwdriver trick and have
written down each note and string, go back through and remove each of
them one at a time and check to see whether the conditions given to explain
both the false beat and the fact that the screwdriver trick works are present.
If this explanation was correct then in nearly every (if not all) instance you
should find 1:) a loose pin, and 2:) a deepened string
mark that effectively places the notch behind the pin<BR> <BR>If you
actually do this, as I have on several restringing jobs to date, you will find
somewhat less then half of the pins are actually loose, and that the string
mark factor shows up even less often. Since the above quote is a
leading into the loose pin / false beat proposition again, we might as
well go there right off and get it done with. Complete your researcher's
ensemble by proceeding to add CA or epoxy to your pins. Add it to ALL
the pins. When done re-identify all individual strings that show false
beats. What you will find is a general improvement of significant
degree. But closer examination of your data will indicate there is some
other casual effect at work. The data shows that 1:) far from all of the
original false strings are cured. 2:) some amount of the uncured are
improved. 3:) there is a significant degree of new falseness on strings
that were clean originally.<BR><BR>All this can lead you to try several
different experiments in an attempt to better understand false beats.
And in the end you will still lack anything close to the definitive
answer. My experience shows clearly to me that a string is just as
likely to display false beats (of the sort that reacts to the screwdriver)
with the above conditions as without. Loose pins can be downright wobbly
in there holes with the string propped up with a center pin under the strings
2-3 mm behind the pin and still there is no significant degree of assurance
that a false beat will or wont appear. Try it on 20 or so strings on the
next beater you get in your shop. On the other hand pins that are tight as you
can ever expect them to be can also display this same kind of beat.
<BR><BR>There is just plain too much randomness to the occurrence of false
beats if the loose pin/crushed edge explanation is applied. <BR><BR>What
we do know (because the rest is pure conjecture) is that the introduction of
CA or epoxy significantly improves the situation. Even more so then replacing
with larger pins by accounts I've heard here. So add the stuff and be
glad for the improvement. But as far as I can see we have not arrived at
an explanation for false beats.
<BR><BR>Cheers<BR>RicB<BR><BR><BR><BR><BR><BR><BR><BR><BR>
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