Hi again, Ron Well, let's keep at this a little while longer. Hope springs eternal? At 12:40 PM 4/19/97 -0500, you wrote: >Hi Susan & all, > >My whole point here is that I'm NOT assuming the string gets up there by hopping, creeping, or anything having to do with being struck by a hammer. I hope none of us are assuming anything. What I'm doing is making a physical model in my imagination, "feeling" the stresses and strains, considering the textures of the materials, and coming up with as many (hopefully) plausible possibilities as possible, that will need to be tested to be any use at all. I haven't encountered anything yet that made me cry "Eureka!" >I still haven't seen a clear argument in support of this. That's why I proposed the argument that strings driven up the bridge pins by a blow would go sharp as they were stretched through a wider stagger angle. I asked if anyone had ever seen a piano driven SHARP by heavy play. What you're attempting to do is disprove the "creep" and "impact" theories by tying them to the "sharp" result. I agree that pianos haven't been driven sharp by heavy use in my experience. Your model of a string going sharp since the path higher on the pin gets longer is very plausible, but in order to be conclusive, you would have to determine that other larger factors couldn't overshadow and mask it. I sympathize, but it's very hard to prove a negative. >In an environment where the heat and humidity have been reasonably stable, the piano is tuned, beat through a recital, and tuned again for a later one, we should see that ol' octave 5 1/2 - 6 debil going significantly sharp if strings are being driven up the pins. I haven't seen this. I agree. When Horace (Greelosaurus) didn't correlate heavy blows with _immediate_ unseating, I abandoned the "sudden death" approach. > If they are creeping up over a period of time, there are too many variable conditions to be able to separate this conjecture from that of the bridge swelling from humidity increase and leaving the pins stranded high when it recedes. Yes, we can't tell, one way or the other. When I suggested "creeping" I didn't associate a cause with it. (Why? Total ignorance, of course.) Heavy blows and vibration from loud notes seem the most likely, but there may be another reason. Bridge roll might be involved, too, with the back bridge pin higher than the front. This could be checked, to see if unseated strings and discrepancies in front and back bearing are associated. (Tuning at 36%, previous tuning 35%, 50% in between, octaves 5.5 and 6 are still sharp.): > Why weren't the strings still up the pins from the last high RH period so the next one wouldn't have moved them? I think that, if anything, strings creep DOWN toward the bridge with play. Otherwise, the first high RH cycle would put them up the pin where they would stay forever (unless tapped down) and the bridge surface would NOT BE GROOVED at all! For all I know, some might indeed come back down. However, grooves appear as soon as strings are put on, like string grooves appear very quickly in hammers. Their presence doesn't proove anything one way or the other. After an enterprising tuner whacks the strings down, heavy grooves can be present, wherever the string likes to hang out. (the string cycling itself up and down with changes in humidity:) >The pin gets burnished flat through the migration path. I don't think the flat spot has a thing to do with holding the string up, but rather, it is a wear track of where the string has been. The vertical distance traveled is very short, making the wear track look like a notch that catches the string and holds it up, but I think it is ovoid, and the pin NEVER LEAVES this indentation. Well, here is something we could check. According to the "humidity swing" model, the pin is tight at the bottom of the hole, and loose further up. It shouldn't be hard to remove a few, and look at them under high magnification. _Is_ the notch ovoid? _Does_ it look burnished, or does it look flakey and sharp edged? If you were a string, would you feel trapped by it? Anybody have some notched bridge pins they could play with? (I don't, unfortunately.)(All I contribute is excessive theorizing.) >As I proposed earlier, if pin climbing is impact related, why don't we see bigger gaps between the string and bridge in extreme cases? And why aren't tunings knocked sharp????? I think this stuff is basic to the puzzle. Has anyone got cause & effect models on the impact theory? No, but I also have trouble with the humidity theory. (However, it's _remarkably_ original and interesting!) First, why has no one noted a difference in the need for string seating in wet and dry climates, or between buildings with good and poor climate-control? Second, the amount of wood that is swelling is very small: only the area from the point where the pin is loose to the top of the bridge, possibly less than 1/2 the length of a bridge pin. This isn't much at all! And if you subtract the amount lost to crushing and deepening the groove in the top of the bridge, that leaves even less. Third, has anyone noticed a difference in string seating in those brands that have the bridge grain going a different direction? There should be one! Vertical-grained bridges should swell higher than horizontal, shouldn't they? Have they? >Endtrans, you're all "it" > >Regards, Ron Nossaman > I've shot my wad, I think, until someone with more data enlightens us. Maybe somebody else can be a better "it". >PS: Sorry about the length of this (these) thing(s). This language is a great thing to play with, but a miserably cumbersome communication medium. Yes, but language is the best we've got! Mime just isn't in the running at all. >>If there's a groove in the pin, doesn't that imply that the string was up >>there quite awhile, sawing away? We seem to have been assuming it hops up, >>but wouldn't it just creep up, reach the limited height that tension and >>downbearing allowed, and then proceed to vibrate and groove the pin? >>Susan Kline Susan Kline skline@proaxis.com P.O. Box 1651, Philomath, OR 97370
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