Unwrapped ends of bass strings

[John Delacour]

At 00:06 01/10/01 +0300, antonis karavelis wrote:

>I have noticed in all pianos, even in the finest grands, that in some 
>bichords in the bass section the unwrapped end of one string of the unison 
>varies in lentgh sometimes significally from the other.

This is just careless manufacture.

>  I'm aware that these unwrapped ends influence inharmonicity (as W.Trow 
> Goddard proposes in his handbook on the strings of the piano)  and I 
> suspect that these varations occur in order to produce a beatless unison.

1. For this test, Goddard used a string of hexagonal section roughly 
equivalent to m.w.g. No. 16 with a 0.70 mm cover on note 20 with a tension 
of about 166 lb.  The length of the string was 100 mm., typical of a rather 
small piano.  Such a combination would be rather unusual in any case, but 
to conduct a test with hexagonal wire seems to be courting errors.  The 
wire ought to have been carefully and evenly filed for this test.

2. Even if Goddard's results are reliable, what is interesting is not how 
_much_ difference the bare ends make, but how _little_ difference.  In his 
table, he jumps from 6 mm. to 20 mm. and from this huge jump obtains a 
difference of a single cent in the 5th partial. 6 mm. is about the minimum 
even the most painstaking string-maker would allow at the soundboard bridge 
end and nobody would make strings to come that close to the top bridge -- 
12 mm. would be considered extraordinarily close.  Whereas 20 mm. is 
already far too much at the soundboard end and slightly more than average 
at the top end.  When I am making strings for my own pianos, I aim to get 
the copper as close as possible to the bridges and can do this because I 
can totally trust my own measurements and have the piano present.  It is 
impossible to rely so much on customers' measurements, even the most 
careful craftsmen, because there are factors such as hitchpin angle, 
downbearing that cannot be accurately allowed for.

If I receive a carefully made rubbing from a reliable customer, I will aim 
to give him 8 mm. bare wire at the soundboard bridge and 15 mm. at the 
top.  This is far closer than the work of most run-of-the-mill stringmakers 
and that includes Steinway in Hamburg, whose strings are in no way 
exceptional and are made with wide tolerances.


>However, is there any method with predictable results for a tuner to match 
>a given set of bass bichords or trichords and how can this be applied in 
>the field? I'm going to restring a S&S D and I fear that in the end I'll 
>come up with a bass section full of "dirty" unisons.

The longer the strings, the less the effect of "bare ends" and if the bare 
ends are minimized their effect on a Model D can be completely 
disregarded.  Far more important is the quality of the steel and copper, 
the evenness of the winding, the tightness of the winding and the proper 
termination of the copper at the soundboard bridge.  By this last point I 
mean the "whipping in" of the copper to add weight at the bottom 
end.  Steinway always used to do this and the only reason they stopped 
would be to save pennies, but it is many years since they bothered.  This 
whipping has far more effect on the disposition of the harmonics than any 
bare wire at the agraffe end.

It seems logical that maximum uniformity in a covered string should be 
beneficial and we have always aimed for the minimum "bare end" that the job 
will allow, but if Trow Goddard's experiment has any value at all then it 
demonstrates that the effect is in fact much less than aesthetics and logic 
would suggest.  To investigate this effect properly, it would be necessary 
to work with a whole range of strings, not a single metre of roughly wound 
hexagonal wire.  One thing can be predicted: the effect will not be 
detectable on a concert grand.

JD