Hubbard, on p. 281, in a footnote, states that theoretically strings of equal length and the same material should all break at the same pitch, regardless of diameter, then goes on: "The process of drawing steel into fine wires seems to produce a structure composed of a hard sheath around a softer core. This sheath is always roughly equal in thickness, and thus occupies a larger percentage of the diameter of a thin string than of a thick one. Therefore a thin string will actually stand a slightly higher pitch than a thick one." He is, of course, refering to practical experience as a harpsichord builder stringing the high end of the instrument. The explanation seems reasonable to me. Ed Sutton ----- Original Message ----- From: "Fred Sturm" <fssturm at unm.edu> To: <caut at ptg.org> Sent: Saturday, December 05, 2009 7:54 PM Subject: Re: [CAUT] Sperrhake Harpsichord wire > 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 > > > > >
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