Call for scaling spreadsheets

[John Delacour]

At 3:26 pm -0400 30/9/06, Farrell wrote:

>...I.e. if a plain tricord has 160 lbs. of tension on each string, 
>there will be a total of 480 lbs. tension for that note. If you 
>consider then a wound bicord note, would you design each string of 
>the note to have 160 lbs. for a total of 320 lbs. tension on that 
>note, or would you shoot for a total of 480 lbs. tension on that 
>wound bicord note where each of the two strings would have 240 lbs. 
>of tension each?

Neither of these solutions makes any practical or logical sense at 
all, as you could easily discover by measuring the strings of any 
half-decent piano.  At the transition from trichords to bichords 
there is always an increase in the tension of the strings and a 
similar increase in tension is required at the transition from 
bichords to singles.  For example a 6'6" piano with 12 singles and 14 
bichord notes on the bass bridge might be strung throughout the plain 
wire at a target tension of 160lbs.  The bichords might then be 
designed for 190lbs throughout with a jump to 270lbs at the top 
single.  From there on down the tension might fall to 210lbs at note 
1.  This would be a pretty good model for a bass scale on such a 
piano.  I omit to speak of core sizes except to say that a typical 
scale might have bichords wound on sizes 17 -> 19.5 and singles wound 
on 21 -> 24.

The longer the piano the more choices there are for bass scaling.  I 
quite often aim for 60% of breaking strain throughout the bass scale, 
which means that the tension in the bichords might rise from 180lbs 
to 220lbs as you go down.

Most difficult and unpredictable of all are short grands, since these 
are most sensitive to variables in the construction and especially 
the soundboard. One often needs to sacrifice purity for volume by 
using stiffer strings, but then again there are exceptions, such as 
the 5' Blüthner.

These are just elementary observations of a general nature.  It is 
not possible in a short email to condense the experience of 20 years 
of bass string design and manufacture, not to speak of the 130 years 
of experience that preceded mine.

JD