At 10:20 +0100 12/2/08, Richard Brekne wrote: >I'll have to measure the bass strings as the scale was modified a >bit by the string maker... tho I can measure if you like. However >in the high treble here is one example at anyrate. G83 is size 13 >PS wire and just barely over 60 mm long. That's very short. So this is a real antique piano you're dealing with? >It failed when the pitch of the piano was up to 436-437. Both >calculations using formulas I have, and PS table put breaking >percent at under 55% in this instance. Well, at pitch A=440 the tension would be at about 101 lbs. and Mas Cabré gives the breaking strain of No. 13 as 224 lbs. Now for Röslau wire I use 196 lbs. as the tensile limit (Paulello calls it the 'Real Breaking Strength', and his figures are very close to mine) and, for bass strings at least, never exceed 70% of that, i.e. 137 lbs. Supposing that PS wire is considerably weaker that Röslau, then you must be pretty near the limit and probably exceeded it. Mas Cabré's "Breaking Strain" is another thing altogether-- quite what I have no idea, and I think it was Ron Nossaman that said he used this value BUT, instead of my 70%, aimed not to exceed 50%. If your calculations tell you you've gone to 55% then you've gone too far. JD
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