[CAUT] Wire Stretch

[John Delacour]

At 11:37 pm +0100 3/5/07, RicB wrote:

>For a 0.8 mm ¯ string of 150 mm long speaking length, 50 mm back
>length... and tension at 150 with zero deflection, a 5 mm deflection
>will increase tension to 189 lbs, cause a frequency change of 248 hz
>(from 2057 to 2305) and impose a 28 lb bearing force on the point of
>deflection.

Well I calculate that to have a 13.5 wire of 150mm in length (a very 
rare occurrence) you would need to have it about note 69 to get a 
tension near 150lbs and the frequency of note 69 is 1396.91 cps.  You 
seem to be saying that you can get a frequency of 2057 cps. from 
150mm. of 13.5 mwg. wire (in other words about note 76) and I say 
that would produce roughly 350lbs of tension and the string would 
break before any upward deflection was imposed on it, let alone 5mm, 
which is inconceivable at any rate at this point of the soundboard.

Have I misunderstood your numbers?

JD