JD   Thanks to your voice of experience <div> </div> <div> </div> <div style="clear: both;">Dale S. Erwin www.Erwinspiano.com Sitka Soundboard Sales Ronsen Piano hammers 209-577-8397 </div> <div> </div> <div> </div> <div style="font-family: arial,helvetica; font-size: 10pt; color: black;">-----Original Message----- From: David Love <davidlovepianos@comcast.net> To: pianotech@ptg.org Sent: Fri, Apr 15, 2011 7:30 pm Subject: Re: [pianotech] Wire tensile limits <div id="AOLMsgPart_0_108c9868-5f73-4fd0-8e39-9dc94afcad63" style="margin: 0px; font-family: Tahoma,Verdana,Arial,Sans-Serif; font-size: 12px; color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);"> <pre style="font-size: 9pt;"><tt>Thanks for clarifying all that. Helpful. David Love <a href="http://www.davidlovepianos.com" target="_blank">www.davidlovepianos.com</a> -----Original Message----- From: <a href="mailto:pianotech-bounces@ptg.org">pianotech-bounces@ptg.org</a> [<a href="mailto:pianotech-bounces@ptg.org?">mailto:pianotech-bounces@ptg.org</a>] On Behalf Of John Delacour Sent: Thursday, April 14, 2011 1:05 PM To: <a href="mailto:pianotech@ptg.org">pianotech@ptg.org</a> Subject: Re: [pianotech] Wire tensile limits [ subject was 'Breaking bass string' ] Looks as if there was a problem with the image. Here it is again as an attachment. At 10:28 +0100 14/04/2011, I wrote: >OK, I've worked it out now and applied it to the published Ršslau >breaking strains... The chart below compares the curves of (1. blue) 80% of 'practical breaking load' calculated from Ršslau official figures and (2. red) the tension calculated with the formula T = 0.515 (dthou^1.667), which gives 60% of the 'ultimate tensile strength' = 'nominal breaking load' = 'mechanical resistance'. The scale goes from 10 mwg to 26 mwg including half sizes. I have inserted the American size 13 at column 6. As you see, the values are almost coincident except for the very thick sizes, where it really doesn't matter. I reiterate that this gives the absolute maximum at which point the wire reaches its elastic limit. The values in question are: 13: 151 lbs. 13 American: 156 lbs. 15: 188 lbs. 17: 225 lbs. 19: 267 lbs. 20: 287 lbs. 21: 308 lbs. The maximum allowable for bass strings, using Ršslau wire, I have learned from long experience, is 55% of ultimate tensile strength and I never exceed this. In practice I use nearer 50% of UTS (60% of 'practical breaking load') for many serious pianos. It is only necessary to approach the elastic limit in certain very short pianos. Examination of hundreds of 19th and 20th century pianos shows that the great majority of them obey the same rule, some of them very closely. JD </tt></pre> </div>  </div>