I don't really buy into the "tuning pin turns" theory. How they can one explain a 100 year old Kimball upright (real beater - all original) I have tuned twice - both times in the summer when AC is running and humidity is very constant in homes. This piano had moderate-to-minimal tuning pin torque (no pins were real snug/tight). The first tuning was August 2001. I raised the pitch 200 cents and tuned it. The second tuning was August 2004 - I only tuned it because the piano was right up to pitch! Terry Farrell > I've read the comments that have been thoughtfully posted, but I have a > very hard time believing that bridge grooves, string stretching, etc., > will take a piano 50 cents flat in 10 years--especially if it's an old > beater that has been crushing and stretching for 75 years. > > I've seen pianos go 100 cents flat in 5 years. Newer pianos, now, > not old beaters. But I would not be surprised if I raised pitch to A440 > on an old piano that should have already done most of its stretching, > then came back 10 years later to find it 50 cents flat. In fact, I > think it's happened to me several times. Even on an old one that's had > 75 years to crush and stretch, if you raise pitch, you're adding more > tension to the strings and more pressure to the top of the bridge. It's > gonna react because it's wood and stretchable metal, not concrete. > > I agree with Sarah Fox; I think those pins are s-l-o-w-l-y turning; > unwinding, if you will. > > It's the only explanation that, to me, could account for such huge > changes. If the strings were stretching, they'd be getting thin and I've > measured enough old strings to know that, except when abused, they don't > change /that/ much. > > No, not that much, but they can decrease in size by a thousandth of an > inch, which is one string size. And yes, if the pins are a bit loose, I > suppose they can unwind a bit, but I don't think it's the main factor in > causing a piano to go flat. > Ever seen the becket sticking out of a pin a little too far, so you > squeeze it in? Does the pitch drop by just a few cents? NO! It drops > WAY down! It just doesn't take much at all to make a string go flat, so > all those reasons above combined (string grooves, pins settling, etc.) > are plenty to explain the pitch drop, even if the pins don't unwind at > all. It's an exponential, not a linear function, right? Isn't pitch > related to the square of the tension? (IMHO) > --David Nereson, RPT > > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives >
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