Hi John, I think that what you are wondering about is the relation between tension, elasticity and overstretching of steel wire and of coarse its friction. I would say that the most important point of all these is the overstretching because thats the razor's edge between a stable tuning and the breaking point. For a string to be stable, the wire has to reach its tensile limit before overstretching. That limit its the physycal limit of an elastic body to return to its original form (size) after beeing stretched. Once you overstretch it, it will never return to its original shape and will loose its flexibility properties which are of a great concern to us tuners. An overstreched string will loose its beautifull timbre (tone), will become dull and full of false beats, not to mention that will also loose its stability because it stops offering resistance. Imagine a rubber band that you stretch to its limit and leave it like that for a couple of months, and then you come back to it and is no tense any more, and if you take it off, you will notice that it won't come back to the original size. Now, the thing I mentioned before, the breaking point, you will reach it once you get to the overstrech point and continue to apply tension (Very obvious). If you want all the numbers and formulas to calculate the precise amount of tension required to have a specific length and size of wire to have it "stable" I realy suggest that you read "The Piano: Its acustics" by W. V. McFerrin. It has a lot of tables of tension for the different wire sizes. Remember that there is no sich a thing as a "stable tuning" per se. The most detriment factor for inestability is humidity! Good luck! Rafael. _________________________ Rafael M. Huberman Muñiz ArtePiano Jazmines #309, Col. Reforma Oaxaca, Oax. CP 68050 México +52(951)5152629 044(951)507-0960
This PTG archive page provided courtesy of Moy Piano Service, LLC