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limits</title></head><body>
<div>[ subject was 'Breaking bass string' ]</div>
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<div>At 10:28 +0100 14/04/2011, I wrote:</div>
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<blockquote type="cite" cite>OK, I've worked it out now and applied it
to the published Ršslau breaking strains...</blockquote>
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<div>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'.</div>
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<div>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. </div>
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<div><img src="cid:p0624081ec9ccdb52200c@[192.168.1.66].1.0"></div>
<div>I reiterate that this gives the<font color="#AA0000"><b> absolute
maximum</b></font> at which point the wire reaches its elastic limit.
The values in question are:</div>
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<div>13: 151 lbs.</div>
<div>13 American: 156 lbs.</div>
<div>15: 188 lbs.</div>
<div>17: 225 lbs.</div>
<div>19: 267 lbs.</div>
<div>20: 287 lbs.</div>
<div>21: 308 lbs.</div>
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<div>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.</div>
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<div>JD</div>
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