[CAUT] Sperrhake Harpsichord wire

[Ron Nossaman]

Fred Sturm wrote:
> On Dec 4, 2009, at 9:46 AM, Ron Nossaman wrote:
> 
>> The mass of the larger wire requires more tension to reach pitch, 
>> true, and the smaller wire less tension. The misconception inherent 
>> here is that tension and break% are the same thing. They aren't. The 
>> smaller wire will break at a lower tension than the larger wire. As a 
>> result, the smaller, original, and larger wire are all at very nearly 
>> the same break% at pitch. This is what the math shows, and this is 
>> what empirical testing has indicated. All these strings will break at 
>> about the same pitch, on average.
> 
> 
>     Have you actually plugged wire gauges into a spread sheet to verify 
> this? 

Of course. Why haven't you?


>And what empirical testing have you done? 

I haven't, at least nothing that will stand up in court. I'm 
relying on published data and formulas of those more qualified 
than I, who have.


>My own empirical testing 
> has shown, on harpsichords, that what I have stated is true. I have 
> assumed it would be true for pianos.

Not with piano wire. Iron, brass, bronze, cat gut, or 
whatever, may work harden more so smaller diameter wire has a 
disproportionately higher tensile strength. What type of wire 
are you talking about?


>     Part of my assumption is based on the fact that bridges are curved 
> to a scale, and it is not a logarithmic one that doubles lengths for 
> every octave. A given string at the same tension should give an octave 
> lower at double the length, two octaves lower at 4 times the length, 
> etc. Scales foreshorten these distances. Hence, I reason that the given 
> size wire would need to be at a lower tension if the octave lower length 
> were shorter. Is this not true?

It's certainly irrelevant to whether replacing a given string 
with a different size changes break%, which has, I think, been 
the question.

Otherwise, you control the tension ranges within the scale by 
your initial choice of wire diameters for given pitches and 
string lengths. The only means to control break% in wire 
strings of specific material is when you get to specify 
speaking length, and/or chose the material.
Ron N