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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 href="mailto:multsch@jvlnet.com" title=multsch@jvlnet.com>Mark =
Ultsch</A>
</DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
href="mailto:pianotech@ptg.org"
title=pianotech@ptg.org>pianotech</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Monday, October 01, 2001 =
9:46
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> request advice on =
sostenuto
trapwork design</DIV>
<DIV><BR></DIV>
<DIV><FONT size=2>List,</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>I am attempting to rebuild a 1920's 5' George =
Steck that is
missing all sostenuto linkage between the pedal rod and =
pitman. I'm
unable to find replacement parts or pictures of the original
replacement. (Thanks to you all who looked for me a while =
back.)
So. . . it appears that I need to design some parts. Being a =
novice yet,
I have a few questions:</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>1. What kind of pin should be used? =
what
diameter? should it be plated? (I can't find anything =
in
parts catalogs.)</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>2. What kind and size of felt is generally =
used in the
bushings and what is the relationship of hole diameter in the block =
versus the
pin diameter and felt thickness?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>3: Any thoughts on the spring rate of =
compression
spring to be used? Any good sources to purchase =
these?</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Sorry if these questions are too basic. =
If you
have other thoughts or concerns I'll be happy to get them. =
Thanks
all.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>Mark Ultsch</FONT></DIV>
<DIV><FONT size=2>Madison WI</FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=2>Trapwork pins are in the APSCO catalog, I =
believe. I
s'pose a large hinge pin would work also. Bushing cloth -- about =
the
same as for damper guide wires. The spring -- either the coil =
type or
leaf-spring type (also APSCO or Schaff) would work, depending how the =
trap
lever is mounted under the keybed. Rate of compression? =
Don't go
buy a newtons per kilogram per second gauge -- just compress it with =
your hand
or foot and see if it feels to stiff or too weak. How far it's =
located
from the pivot pin will determine this. Size of hole -- I would =
just
wrap the bushing cloth you're gonna use over the pin you're gonna use =
and
measure the overall diameter with a caliper or micrometer. Then =
drill a
trial hole in a scrap piece of wood, tear or cut the cloth into strip =
3 times
the diameter of the hole, pull it through the hole, then push the pin =
in and
see if it's too loose or too firm, and adjust drill size up or down
accordingly -- or the thickness of the bushing cloth, if you have =
several
thicknesses. None of this is all that critical -- just so =
the
pedal isn't too stiff or too loose -- look under other pianos, take
measurements, and copy one. Usually the pitman and the =
coil-type
spring sit in flat-bottomed shallow holes in the trap lever (use a =
Forstner or
spade bit), with a similar hole in the keybed for the top end of the
spring. Sometimes they're bushed with felt, sometimes not. =
L-shaped threaded hooks usually go under one end of the trap =
lever to
keep the pitman from falling out if a pedal rod or the whole lyre is
removed.</FONT></DIV>
<DIV><FONT size=2> =
Sincerely, David
Nereson, RPT, Denver </FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
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