<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: bass string problem</title></head><body> <div><font face="Arial" size="-1" color="#000000">Hi David,</font></div> <div><br></div> <blockquote type="cite" cite><font face="Arial" size="-1" color="#000000" >           Had a string break in the low tenor during a pitch raise on a 1983 Everett console.  Decided to put on a universal string and leave it if it sounded OK.  (Would order custom string if it didn’t).  Measured the string on the tapered slot gauge and it said # 8, so that’s what I put on.  Wouldn’t pull up to pitch – it broke.  Have only had that happen maybe twice in 25 years.  Brand new strings can usually be pulled way over pitch and still not break.  So tried a # 8 ½  instead, thinking it’s meant to be at a higher pitch than the # 8.  Nope, it broke too! </font><br> </blockquote> <blockquote type="cite" cite><font face="Arial" size="-1" color="#000000" >            Now, the winding on the original string is aluminum or nickel (I assume), not copper, but should that matter?</font></blockquote> <div><br></div> <div>It certainly matters. Copper has a specific density of 0.89 gr/cc, whereas Aluminium has only 0.256 - 0.264, depending on its analysis. A copper winding of the same diameter will cause a higher tension to be required to achieve a certain pitch.</div> <div><br> <br> </div> <blockquote type="cite" cite><font face="Arial" size="-1" color="#000000"> It’s the core wire that holds the tension, right?  I measured them all when I got home and the original string’s core wire is .037”, the # 8 measured .039”, and the # 8 ½ measured .038”, I believe.  Shouldn’t that be close enough?  Should I go back and try a # 9?  </font></blockquote> <div><br></div> <div>Before you get a new string made, it would be worth having a look at the original design on a scaling spreadsheet. Post up the speaking length, cover diameter and the note number on the piano. We can look at the tension to see if it is getting up near critical levels. Quite a few of us on the list have spreadsheets in which we can drop the numbers to see what is going on.</div> <div><br></div> <blockquote type="cite" cite><font face="Arial" size="-1" color="#000000">P.S.  Why did they use aluminum or nickel wound for the two lowest tenor strings, when all the bass are copper?</font></blockquote> <div><br></div> <div>Probably because the designer wanted to wrap the strings to avoid the usual tension drop near the break, but a copper wrap might have caused the tension to go too high. Even a small diameter copper wrap will cause a big increase in the tension at pitch. Aluminium will result in a much smaller tension increase on account of its lower density. The higher tension of the wrap will be more likely to be a problem if the wound strings are place on the same bridge as the plain wire - a design approach which doesn't work.</div> <div><br></div> <div>I've considered using Aluminium previously for a couple of adjacent break notes. I had some strings wound and tested the tone. But in the end I decided that the best approach would be to design the wound strings so that 0.2 mm (8 thou) is the smallest copper wrap used, and if they have to be used in the treble section that they are located on their own tenor bridge with a reduced speaking length. I've had experimental copper wrapped strings wound with diameters going right down to 0.125 mm (5 thou) as well, but I had to make up a special spool with a ball bearing mounted shaft, to prevent the wrap wire from breaking as the winder wrapped the string. Its altogether too much trouble.</div> <div><br></div> <div>Post up your string specs and we'll have a look.</div> <div><br></div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>   </i></font><font color="#0000FF"><i>Grand Piano Manufacturers</i></font><font color="#000000"><br> _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au</font></div> <div><font color="#000000">mailto:ron@overspianos.com.au<br> _______________________</font></div> </body> </html>