Hi, I read this with great interest. I wonder if the damping effect of the cast iron and the resultant energy *bleed* is the cause of the lowering of the pitch on three string unisons. It would certainly be variable from piano to piano as plates are not really too consistent. >My thinking was that when a string is struck and vibrates then there must >be an periodic increase in tension. When a string of fixed length is >displaced then it seems to me that there must be an increase in tension. >For the fundamental, as the string swings up the tension increases, comes >back to nominal as the string comes back level, and increases again as >the string swings down. This is happening several times a second. Also, >this is happening for all of the partials, just at different frequencies. This >increase in tension must be sustained by the plate. Admittedly, the loads >in question are low and the deflections must be small. But, cast iron has >high damping (by metal standards) and the vibrations are occurring several >times per second, so even a small amount of deflection could perhaps >dissipate consequential amounts of energy. The amount of this deflection >will depend on how stiff the plate and pinblock arrangement are. --- Regards, Don Rose, B.Mus., A.M.U.S., A.MUS., R.M.T., R.P.T. Tuner for the Saskatchewan Centre of the Arts mailto:drose@dlcwest.com http://donrose.xoasis.com/ 3004 Grant Rd. REGINA, SK S4S 5G7 306-352-3620 or 1-888-29t-uner
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