String tension

[Tom Cole]

Roberto Rovira wrote:
> 
> Dear list,
> I had to raise half step the pitch of an upright  piano today.
> The owner asked me how many kilos (or tons)the tension increase
> in that case .
> Could anybody tell me about this subject? I take for granted that
> many of you would be able to do that.
> Thank you in advance.
> 
> Roberto Rovira
> Argentina
> roberto_rovira@ciudad.com.ar

Roberto,

In my home-made string scaling program, I opened a document that had
entries from a 1907 Steinway upright. I changed the number of a note
from (in this case) 37 to 36 - to make the note go a half step flat. I
saw the tension go from 161 pounds to 144 pounds. Therefore, raising the
pitch of this note 1/2 step (back to standard pitch) would amount to
11.8% (17 pounds). If the whole piano were raised that amount, and let's
assume all the strings are normally at around 160 pounds (they're not,
of course), then a rough estimate of the total amount of tension added
would be 88 x 17 = 1496 pounds or 678 kilos.

-- 
Thomas A. Cole, RPT
Santa Cruz, CA