more bass scaling questions

[John Delacour]

At 08:57 -0700 22/7/08, Gene Nelson wrote:

>... Piano is 5'8", long bridge is relatively straight at lo tenor, 
>notes 26-30 (bichords) are on the long bridge,  # 10 core = #22, spl 
>= 1156.5mm, #11 core = 19.5, spl = 1148mm.  #30 core= #19, spl = 
>985mm, Note #31 = #19 and spl = 964.5mm

Yes.  A piano of this length ought to have more singles (say 13) and 
more notes on the bass bridge (say 28 or 29). The problems with this 
type of scale are as follows:

1.  Since the bichords go down too low in the scale, it is impossible 
to keep the tension at a proper level (say 190-210 lbs) and at the 
same time keep the tone acceptable and allow a clean transition to 
the singles.  The solution is a fudge -- they try different 
combinations, all of them unsatisfactory, until they get a result 
that is as close as they can, and there's the scale.

I suspect, without having all the lengths, that the best arrangement 
for this piano would be 14 singles and 15 pairs, all on the bass 
bridge with no break notes on the long bridge.  Thus you would have 
note 14 with a 21.5 core and a diameter of 3.49mm giving you about 
261 lbs and note 15 with a 19.5 core and a diameter of 2.92 giving a 
tension of about 202 lbs.

Since you need to stick with only 10 singles, you might get a better 
break by using a double cover on these if they are at present single 
covered, for example a 22 core with a 0.65 under-cover and 1.00 top 
cover would give you 4.18 mm and a tension of about 250 lbs.  That's 
just a hunch.  If I were with the piano and could listen to the break 
myself, I'd be able to judge better.  Your note 11 strings are too 
fat and flabby and your note 10 next door is probably a bit too fat 
but stiff and tight with it.  You need something not quite as tight 
and more flexible.

>>As to the pair at note 30, I can say without knowing anything else
>>that the tension is far to high...
>
>< I will input the #16.5 core into the scale to see how the tension 
>will decrease.  I assume that I would also decrease wrap diameter? 
>Current = .057in

Well, when I said 16.5 I was supposing the note was on the bass 
bridge.  This brings us to the second problem, which is the same in 
character to the first  --  2.  Since the bichords don't go high 
enough on the bass bridge, another fudge is needed, namely 5 pairs of 
covered strings on the long bridge.  Not satisfied with solving one 
more break problem, they give themselves two more -- the break from 
bass bridge to long bridge AND the break from covered pairs to plain 
triplets.

Without knowing the piano and all the lengths, I'd guess you might be 
better off using a 17.5 core for note 30 with a 0.175 cover, which 
will result in a diameter of 1.30 mm and a tension of 182.  Perhaps 
use 17.5 for all five long bridge bichords and then go down to 16.5 
for note 26 keeping the tension about the same

JD