So, in order to blend these three top notes you would need the figures for how many notes going down (and also up I presume-the first two notes across the break in the low tenor are also wrapped strings). Can you describe the formula you use for what you refer to as the yield point? David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of John Delacour Sent: Saturday, January 08, 2011 12:27 PM To: pianotech at ptg.org Subject: Re: [pianotech] Yamaha Upright String Breaker At 11:04 -0800 08/01/2011, you wrote: I've got a Yamaha studio upright that continues to break strings at D3 (wrapped bichord). The speaking length is 890mm, the core wire 14 gauge and the outside wrapped dimension is .058". My spread sheet shows that at 69% BP but my own formula might be low. Any string makers care to input here? It seems to me it's got to be too high. By my reckoning that gives over 180 lbs. - 84% of the yield point of #14 when 70% is the maximum allowable for safety, so it is designed to break and break again. Suppose it is covered at present with 0.35mm. copper at present, then if you want to stick with a #14 core you need to go down three sizes of copper to 0.275mm., which wil give you 151 lbs. and 69% of max strain, which is just within the limit. If you use a #15 core with the same cover, you will get 162lbs. and 68%. You will need to change both strings of the pair and probably the strings for the two notes below as well if you don't want the same to happen to them. Don't confuse _your_ 69% with _mine_ . Whatever spreadsheet you and others are using is misleading. You should not have bass strings at a tension greater than 70% of the figure in the table below. From what I've heard from others who use, probably, the spreadsheet you refer to, you should not exceed 50% of the BS figures it uses. And yes, I'm a string maker. JD 12 0.725 174 12.5 0.750 185 13 0.775 196 13.5 0.800 207 14 0.825 218 14.5 0.850 229 15 0.875 240 15.5 0.900 251 16 0.925 264 16.5 0.950 276 17 0.975 288 17.5 1.000 300 18 1.025 314 18.5 1.050 326 19 1.075 339 19.5 1.100 339 20 1.125 371 20.5 1.150 387 21 1.175 405 21.5 1.200 421 22 1.225 439 22.5 1.250 455 23 1.300 479 23.5 1.350 504 24 1.400 532 24.5 1.450 570 25 1.500 609 25.5 1.550 660 26 1.600 726 -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20110108/fcfd1bb2/attachment.htm>
This PTG archive page provided courtesy of Moy Piano Service, LLC