Weber upright from 1884.

[John Delacour]

At 13:46 -0600 1/1/08, <mccleskey112 at bellsouth.net> wrote:

>I'm wondering what the difference is
>in foot pounds between 435 and 440 cps.

Foot-pounds doesn't come into it -- it is _pounds_force_ we deal with 
in speaking of the tension of piano strings.

The tension is proportional to the square of the frequency, so a 
string that requires 160 lbs. to come to pitch at A=435cps. will need 
163.7 lbs. at A=440cps.

   160 / (435 ^ 2) * (440 ^ 2) = 163.70

Looked at from a practical point of view, if you raise your A 5 
cycles above pitch in order to set the pin etc., which is not an 
outrageous proposition, you are already raising it to 440cps.  The 
main "ill-treatment" I referred to is subjecting any part of the 
string at any time in its life to a tension greater than the wire is 
designed to withstand and the greatest danger is at the highest 
singles, the highest bichords and the highest trichords, where the 
wire is most likely to be closest to the tensile limit.

JD