Hi Richard: The National Wire Co of Niles MI had an Instron tensioning machine which extended a 10 inch wire at the rate of 1 inch per minute. A graph was made of the result of the tensioning up to the time of the break. The graph was linear up to the point of elongation. An arbitrary line was drawn afterward which was parallel to the original graph straight line portion, but spaced at .2 % away. Where this line intersected the yield curve was the official location of the yield point on the curve. One could then figure the % of break strength. The graph is too complicated to try to draw with ASCII art. The words elastic limit were not used in this study. I assume them to mean the limit to which a string can be stretched and yet return to its original length. Of course in piano considerations, the speaking length of the string remains relatively constant since the V-bar does not move and the bridge moves very little. In Bass string making, it is important to know how much the string stretches in coming up to pitch because it is not wise to pull the copper winding up into the agraffe. The thin high tensioned wound strings in the tenor section can stretch more than 3/8 inches. Most string replacement companies will generally make the unwrapped lengths at the agraffe end a little longer than the original just to guard against the possibility of the wrap ending up in the agraffe. The Parson PScale program computes this elongation in order to let the designer have full control of the unwrapped lengths which have so much to do with the final inharmonicity of the Bass strings. Jim Coleman, Sr. PS Thet above test was actually done by another person under the supervision of Charles Walter, my boss (term of endearment). On Sat, 26 Apr 1997, Richard Moody wrote: > > <html> > <pre> > > > > Jim Coleman's Data > > > >Here are some examples of tests taken at the CGConn engineering > labs while > > >I was there. > > > > > >wire size yield point break point > > > > > >13 258 lbs 290 > > >13.5 267 303 > > >14 317 355 > > >15 > > >16 347 398 > > >18 431 487 > > > > > > > > >There can be as much as 10 to 20 pounds greater tension in the > segment > > >between the tuning pin and agraffe as there is in the speaking > length > > >while pulling pitch up. > > > I take it to mean the yield point is the same as elasticity limit. > Where the elasticity limit is that tension where "stretch" or > elongation occurs. The string gets pulled so much that intead of > returning to its original length, it stays "stretched". This happens > well below the breaking point. There are theories that strings > pulled beyond their elasticity limit,"no longer can be expected to > function as music wire". (the other explanation for false beats) > > So two question, is yield point the same as elasticity limit? and > how is/was yield point measured? > > Here are some historical records of string strength taken from > Dolge. > (wish I had a scanner) > > 1867 World's Exhibition, Paris > Moritz Poehlmann's wire Nos. 13 14 15 16 17 18 > broke at a strain of .............Lbs. 226 264 292 296 312 348 > > 1876 World's Exhibition, Philidelphia > Steinway & Sons' testing machine used. > Moritz Poehlmann's wire Nos. 13 14 15 16 17 18 > Lbs 265 287 320 331 342 386 > 1893 Chicago World's Fair > Poehlmann's wire Nos 12.5 13 14.5 15 16 > break point lbs 325 335 350 400 415 > > Jim Colman's tests Nos 13 13.5 14 15 16 18 > break point lbs 290 303 355 398 487 > > This shows piano makers have had modern strength wire for 100 years. > > Richard Moody > > > > > </pre></html> > > > >
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