double-wound strings

[Stephen Airy]

--- John Delacour <JD@Pianomaker.co.uk> wrote:
> At 6:54 PM -0800 12/8/01, Stephen Airy wrote:
> >What do you think is better in a piano with a 142cm
> >speaking length on low A?  Singles all the way
> >through, or doubles from notes 1 to 10 and singles
> >(bichords) from 11 to 27, like the piano I'm
> talking
> >about is now?
> 
> 
> I've taken the bridge shape (string lengths) of an
> old 6"6" Bechstein 
> as a basis for Sample Scale 1, added notes 26 and 27
> and put the 
> break after note 10, as on your piano.  Your bridge
> could easily be 
> very different, but the question is about the low
> bass, so it is 
> probably be somewhat similar.  Sample Scale 2 is a
> scale with similar 
> targets but with a different bridge shape.
> 
> As it is, you probably have on note A1 a No. 25 core
> with a 200 - 210 
> cover, the thickest normally used (Steinway go up to
> 220 but I can't 
> get it because nobody asks for it).  This will give
> you a tension 
> roughly between 200 and 220 lbf with a strain left
> or right of 35%, 
> which is low.  On most pianos these bottom notes
> will not sound too 
> good.
> 

I'm not sure what mine is, but it sounds fairly good
to me.  (It's quite a lot better than my mom's 5-foot
premie(sp?) baby grand and way better than some
friends' spinets, but not quite as nice as a 9-foot
baby grand.

> Practical considerations prevent the spinning of a
> 210 cover on say a 
> 22 core.  It is just about possible, but noone would
> want to do it, 
> so a 25 core is used mainly just to avoid breakages
> and the waste of 
> a lot of copper as a result.  There is also the
> question of the ratio 
> of core to cover to consider;  Too large a ratio
> will result in a 
> string that vibrates in a peculiar way, giving rise
> to discordant 
> partials.  This 25/210 string will be pretty stiff
> at this length.
> 
> I can't guess what your piano is, but it's probably
> American.  

It's "Ricca & Son" - New York.

> I have 
> just begun work on a 6'6" piano with 140 cm for A1,
> ten singles and 
> 16 bichords.  All the singles on this piano are
> double-covered, as 
> opposed to the Bechstein which has all s/c like
> yours and a break at 
> A13.  

My monochords are all double-covered.  Oh, by the way,
it's a 56" upright.

> I would prefer the break at 12 or 13 on these
> pianos in order 
> to get a better transition.  Very old pianos with
> the transition too 
> low very often have a disproportionately rough sort
> of trombone 
> quality about the lowest bichords.
> 

My piano has some room for improvement in the tone
from F1 to G#1, around where the break is (F1 & F#1
being monochords and G1 and G#1 being bichords), and
other spots as well.

> I already mentioned my preference for a single cover
> down to the 
> point where the strain becomes too low and where it
> is possible to 
> get a smooth transition.  This introduces one more
> 'break' to deal 
> with but proper treatment allows this to be smooth,
> just as proper 
> treatment of the other transitions.  In the example
> below, the length 
> of the piano allows me to use a 1:3 under-:top-cover
> ratio, which 
> gives a closer resemblance of the s/c properties
> than a closer ratio. 
> I use three basic ratios, normally using one ratio
> only throughout 
> the d/c section, though sometimes I use all three in
> succession -- it 
> depends on the scale and what I'm aiming for in the
> light of various 
> considerations.  I make more strings for others than
> I make for 
> myself and do not impose my own conceptions on
> customers I know have 
> different tonal aims, though these happen to be in a
> tiny minority. 
> When the strings are for my own stock pianos, which
> comprise only 
> makes that I choose, then I tend to work within a
> fairly narrow 
> range, having first determined the overall tonal
> qualities of the 
> instrument as a whole.
> 
> Here are the machine worksheets for the two scales. 
> Sizes are New 
> Westphalia for the steel (not much different from
> American) and 1/100 
> mm for the covers.  The third column is the speaking
> length.
> 
> 
> For Scale 1 I have tapered off the tension from ca.
> 285 lbf on note 
> 10 to ca. 250 at A1.
> 
> Scale 2 is the nicer-shaped bridge, though I would
> put the transition 
> at 12/13, and I have kept the tensions high right to
> the bottom on 
> this one with almost 300 lbf on note A1.
> 
> Both scales are simply hypothetical examples.
> 
> 
> ++++++++++++++++++++++++++++++
> 
> SAMPLE SCALE 1
> 
> 
> A	1	142.5	23.5	65	175
> A#	2	141.8	23.5	60	170
> B	3	141.2	23.5	60	160
> C	4	140.5	23.5	55	155
> C#	5	139.8	23.5	55	150
> D	6	138.8	23.5	50	140
> D#	7	137.8	22.5	170
> E	8	136.8	22.5	160
> F	9	135.8	22.5	150
> F#	10	134.2	22.5	140
> G	11	132.7	20.5	100
> G#	12	131.1	20.5	95
> A	13	129.5	20	90
> A#	14	127.4	20	85
> B	15	125.3	19.5	80
> C	16	123.2	19.5	75
> C#	17	121.1	19	70
> D	18	118.5	19	65
> D#	19	115.9	18.5	60
> E	20	113.3	18.5	55
> F	21	110.7	18	50
> F#	22	107.8	18	50
> G	23	104.8	18	45
> G#	24	101.9	18	45
> A	25	98.9	17.5	40
> A#	26	94.8	17.5	40
> B	27	90.8	17.5	35
> 
> 
> 
> ======================================
> 
> SAMPLE SCALE 2
> 
> 
> A	1	139.6	24	85	185
> A#	2	139.0	24	80	175
> B	3	138.5	23.5	75	160
> C	4	137.9	23.5	70	150
> C#	5	137.3	23.5	65	140
> D	6	136.4	23.5	60	135
> D#	7	135.5	22.5	175	  -
> E	8	134.6	22.5	160	  -
> F	9	133.7	22.5	150	  -
> F#	10	132.6	22.5	140	  -
> G	11	131.6	20	115	  -
> G#	12	130.5	20	105	  -
> A	13	129.4	20	100	  -
> A#	14	127.9	19.5	90	  -
> B	15	126.5	19.5	80	  -
> C	16	125.0	19.5	75	  -
> C#	17	123.5	19	70	  -
> D	18	121.7	19	65	  -
> D#	19	119.9	19	60	  -
> E	20	118.1	18.5	55	  -
> F	21	116.3	18.5	50	  -
> F#	22	114.1	18.5	40	  -
> G	23	111.9	18	40	  -
> G#	24	109.6	18	35	  -
> A	25	107.4	18	35	  -
> A#	26	104.9	17.5	30	  -
> B	27	102.1	17.5	25	  -


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