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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=mfarrel2@tampabay.rr.com
href="mailto:mfarrel2@tampabay.rr.com">Farrell</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">Pianotech List</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, July 20, 2006 10:15
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: tuning pin torque</DIV>
<DIV><FONT size=2></FONT><FONT size=2></FONT><BR></DIV>
<DIV><FONT face=Arial size=2>There will certainly be some variation of opinion
on what "acceptable" tuning pin torque might be, but maybe about 60 to 150
in.-lbs. (note: inch-pounds, not foot-pounds) will yield a reasonable-tuning
piano. </FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>Terry Farrell</FONT></FONT></DIV></BLOCKQUOTE>
<P><FONT size=2>Just to hijack this thread, I've always been curious about the
exact units for torque. In rec.music.makers.piano, Don Gilmore (an
engineer) wrote this reply. </FONT></P>
<P><FONT size=2>I wrote:</FONT></P>
<P>> ...The force on a tuning pin is measured as torque, but just considering
<BR>> string tension, I guess simple mass is the right unit, as though a
weight <BR>> were hanging off the end of the piano (right?). <BR></P></DIV>Hi
Cy: <BR>
<P>Yeah, tension is just in pounds. Properly it's force (or weight), not
mass, <BR>but that's just being picky. One pound-mass on earth weighs one
pound <BR>(exerts one pound of force downward) and since you probably won't be
working <BR>on pianos on the moon, a pound is a pound. <BR></P>
<P>Torque is the tension multiplied by the distance from the center of
<BR>rotation. If the string has a tension of 150 lbs and the center of the
<BR>string is .125 in. from the center of the tuning pin then the torque is
<BR></P>
<P>150 lbs x .125 in. = 18.75 lb-in <BR></P>
<P>To get lb-ft we can divide by 12 and get 1.56 lb-ft. In the engineering
<BR>world we call torque "pound-feet" instead of "foot-pounds" so that we don't
<BR>confuse torque with energy. <BR></P>
<P>Sorry to interrupt the thread with my nit-picking. <BR></P>
<P>Don <BR>Kansas City </P>
<P>-----------------------</P>
<P>Thus it seems the common unit we use is simply the string tension (150 lbs.),
while the proper (?) equivalent in torque would be 18.75 "pound-inches".
Yet the torque wrenches we use for tuning pins are calibrated in pounds...
right?</P>
<P><FONT size=2>--Cy--</FONT></P></DIV></BODY></HTML>