Thanks very much for the info. --David Nereson -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org]On Behalf Of John Delacour Sent: Tuesday, September 26, 2006 10:54 AM To: Pianotech List Subject: RE: bass string problem At 2:55 am -0600 26/9/06, David Nereson wrote: >OK, the core wire diameter is .0365", the overall diameter with >aluminum wrap is .070", the speaking length is about 32 1/4", maybe >32 3/8" -- can't tell exactly because it's out of the piano and the >bridge pins didn't leave very discernible bends. It's the >right-hand string of a 2-string unison on F#3 (note number 34). You need 0.15mm copper wound on a No. 16 core for this note. 0.15 is the thinnest wire we use in bass string making and it gets very little used -- in fact I am still using the 1 Kg. reel I bought when we set up the string-making factory 20 years ago. You could also use a 0.20mm. copper cover. This would bring the tension to 73% of breaking strain, rather than the 70% maximum I adhere to, but provided you are aware that the string is near its limit and are careful not to take it more than a few beats above pitch when fitting it, there is no danger of its breaking. You need no fancy software to calculate whether a string is too tight. You can do it as accurately as you need with a standard calculator following the steps below. As you will see, the tension on your No. 16 wire would be about 326 lbs. whereas is ought to be no more than 184 lbs. F ( Frequency note 34 174.61 cps.) L ( Length 32 3/8 = 82.2 cm.) D ( Diameter 0.07" = 0.178 cm.) F 174.61 * L 82.2 --=> 14353 * D 0.178 --=> 2555 * = --=> 6527124 / 20000 = --> 326 _____________ To recap (USE CENTIMETRES!) : F * L * D * = / 20000 Very simple. This is what I myself do to check the tension of all odd strings I am sent for replacement. When you order a replacement string, you should always tell the string-maker what note it is so that he can calculate whether the string has broken through excessive tension and make adjustments. If he can't do that, use a serious string-maker. JD
This PTG archive page provided courtesy of Moy Piano Service, LLC