This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment ----- Original Message -----=20 From: Mark Ultsch=20 To: pianotech=20 Sent: Monday, October 01, 2001 9:46 AM Subject: request advice on sostenuto trapwork design List, =20 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: =20 1. What kind of pin should be used? what diameter? should it be = plated? (I can't find anything in parts catalogs.) =20 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? =20 3: Any thoughts on the spring rate of compression spring to be used? = Any good sources to purchase these? =20 Sorry if these questions are too basic. If you have other thoughts or = concerns I'll be happy to get them. Thanks all. =20 Mark Ultsch Madison WI 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. Sincerely, David Nereson, RPT, Denver =20 =20 =20 ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/43/a2/8f/47/attachment.htm ---------------------- multipart/alternative attachment--
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