Hi Roger, I left the entire *history* intact this time. John Lillico's contention was that even with *no* support structures being involved that humidity some how changed the shape of the plate. Of course I agree that the wooden structures *do* cause the plate to change shape. And in fact other hints (I will not enoble it and call it research) have indicated to me that plate flex has a great deal to do with pitch correction, much more than the crown of the sound board. At 12:45 AM 08/18/2000 -0600, you wrote: >Hi Don, > Of coarse the humidity effects the plate. As the crown rises,so >does the pitch. This in turn increases the loading on the plate. The >whole reason for nose bolts, is to minimize the flex of the plate due to >changing moisture conditions. Most pianos have a nose bolt fairly close to >killer octave range and tenor break, to minimize this effect. In some >cases the plate web will be increased in height, and or, it's T >construction design is used to compensate. Depending on the ductility of >plate material. it will influence the shape of design, and what extra >support will be required. Further to this, many grands will have an added >support structure that is under tension to help stabilize movement of the >whole system. In the case of Steinway, the horn is under compression, >the thin slats that fit across the beams tension. >Many factors come in to play. due to torsional stresses. How much force is >supported by the plate, beams, rim, integration of pin block to whole >structure, and trapezium distortion of the rim. This is just to name a few. >You have opened a real can of worms, that is extremely complex. >No black and white answers, only case by case study will yield a few answers. > >Regards roger > > >At 08:22 PM 17/08/00 -0600, you wrote: >>Hi John, >> >>I can see temperature affecting the plate but not humidity. I am still >>having trouble visualizing what you are trying to tell me. Interesting >>suggestion that the duplex is a stability device. More worms anyone? >> >>At 09:46 PM 08/17/2000 -0400, you wrote: >>>At 08:36 PM 08/17/2000 John Lillico stated >>> >>>Throw away the soundboard and bridge and just have your strings and plate. >>If the plate doesn't swell with humidity, although I think it might, it >>will at least be tilted somewhat through expansion of that upon which it >>rests. The plate edge beyond the bridge keeps getting longer, not by note >>but by string. This is on both grands and uprights and that's why your >>right string is found to be at a greater tension than the left. >>> >>>This may not be as extreme where you have those "adjustable" duplux >>doohickeys on some grands though. >>> >>>John Lillico, RPT >>>Oakville, Ontario >>> >>> >>> >>> >>> >>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 >> >>drose@dlcwest.com >>http://donrose.htmlplanet.com/ >> >>3004 Grant Rd. >>REGINA, SK >>S4S 5G7 >>306-352-3620 or 1-888-29t-uner >> >Roger Jolly >Saskatoon, Canada. >306-665-0213 >Fax 652-0505 > > 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 drose@dlcwest.com http://donrose.htmlplanet.com/ 3004 Grant Rd. REGINA, SK S4S 5G7 306-352-3620 or 1-888-29t-uner
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