On Dec 5, 2009, at 1:56 PM, Ron Nossaman wrote: > In that REAL WORLD you were so insistent on, are you likely to > deviate more than 0.001" on that string replacement? And wouldn't > that calculated break% difference be at worst, a half percent by > your formulas? And how, by any reasonable criteria, is this worth > the time spent on this thread trying to drag useful information out > of it? When you are in the real world with a string breakage problem, you are probably in a high range of the breaking %, no? What are you going to do? Is changing the speaking length an option? Not often. So you need to have a knowledge of the principle that underlies this. Try entering lengths in your spreadsheet that get you in the 55-60% break range. Experiment with increasing and decreasing diameter. You'll find (or at least I have found) that a .001" change narrower can get you 1-2% lower break%. A change wider gets you higher break%. It's a consistent pattern. I grant you, it isn't dramatic, and might not turn out to be significant on pianos, in real application. But it is clear that if you are going to experiment with substituting string size, to deal with a note that is breaking consistently, a smaller size is much more likely to solve your problem. I haven't found an instance where the pattern was reversed, have you? I have never done this on pianos (except that if I happen to be missing the half size at the moment, I go small rather than large). My experience in this is with harpsichords. On harpsichords, I suspect that the break% variance is probably larger in proportion, judging from my experience. Partly because we are dealing with proportionally larger differences of string mass (.014 versus .015 is a bigger difference than .040 to .041), and often with scales that are a lot more "ambitious" (pushing the break% envelope). Maybe someone on the list has a set up for harpsichord tension, break%, etc and can run some figures or provide a spreadsheet. I do know from several experiences of trying, that, for example, replacing the .015 brass string that is breaking with .016 is a waste of time and material. It will break, probably faster than the .015 (probably when you get to about 1/4 step flat of target pitch). Replacing it with .014 is pretty likely to be successful. Which is really the only point I was offering, except that I wanted to explain why it is so, because it is counter-intuitive. You are right, far more smoke than fire in this thread, especially in application to pianos. But it is a useful thing to know if you work on harpsichords, where this problem often arises. And that is what this thread was about originally. I don't believe, though, that any of the statements I made about pianos was wrong (though the significance is maybe lower than the verbiage would indicate). For instance, I believe you will find it is true that any string on a piano replaced with 13 gauge will have an equal or lower break% than with its existing gauge (and similarly for other gauges moving down the scale). Regards, Fred Sturm University of New Mexico fssturm at unm.edu
This PTG archive page provided courtesy of Moy Piano Service, LLC