string pressure on board

[Ron Nossaman]

>Hi everyone,
>
>Is there any one good with numbers out there, who can calculate the
>*approximate* difference in string pressure on a typical baby grand or
>upright, between 440 hz and 435 hz? Please duplicate answer to me privately.
>
>I've heard techs state that the difference is "many tons", but my gut tells
>me that is an exaggeration. Am I right?
>
>Howard S. Rosen, RPT

Arbitrarily using a 6' 3" grand scale that was on the short file list in
Excel, at A - 440 I have an overall tension of 37,566lbs of tension, and
470lbs of downbearing. At A - 435, total tension is 36,717, and downbearing
is 460 lbs. In actual practice, which my scaling spreadsheet and I aren't
smart enough to figure automatically, the board would rise some with the
tension drop and the bearing would be somewhere between 460 and 470. Not
much change compared to the tension. That bearing is for a new board with
bearing ranging from about 0.4° in the bass and low tenor, up to about 1.5°
in the high treble. In older soundboards with less bearing, sometimes a lot
less, it won't be nearly that high, and bearing load changes with pitch
changes will be very small. 

Ron N