Twisting bass strings

[John Delacour]

At 8:24 PM -0800 1/29/02, David Love wrote:
>No, it's not the bridge.  I've spent a good deal of time 
>reconstituting it (as it were), repinned, renotched, bearing reset, 
>secured, etc..  Without twisting the strings, they sound totally 
>dead, when the strings are twisted they do  come up and have quite a 
>decent sound.  Other strings I've used don't require it and sound 
>good straight on.   A bit of a mystery to me.

David,

I reprint below a message I wrote to the list four months ago.

I think the simple answer to your mystery is that stringmaker X is 
pulling hard enough on the copper and stringmaker Y is not.  Last 
week I got a call out of the blue from a guy in Scotland who set up 
as a stringmaker four years ago and was having a problem with 
dull-sounding thick single-covered strings. Apparently the strings 
are not buzzing but people just say they're lifeless. I asked him to 
describe his technique and from this description I knew that he could 
not possibly be applying the proper tension to the copper, which is 
really very high for the thick gauges.  I told him how to change his 
practice and maybe he will -- if not, he will never make good bass 
strings.

At 1:51 PM -0800 1/29/02, Carl Meyer wrote:
>Arledge says "no twist"  I think that is because he twists the core 
>wire before winding.  He uses a motor on each end of the core wire 
>that can be programmed to do whatever.  A servo controlled tension 
>feeds the copper wire.

I mention pre-twisting as a possibility in the last paragraph of the 
message below.  One thing I did not mention is the desirability of 
straightening the steel wire, whether for bass strings or plain wire. 
A set of bass strings should hang almost vertically.

JD


_________________________
Message-Id: <5.1.0.14.0.20010902133006.00ac5c30@pop3.demon.co.uk>
Date: Sun, 02 Sep 2001 15:31:07 +0100
To: pianotech@ptg.org
From: John Delacour <JD@Pianomaker.co.uk>
Subject: Re: Twist GC bass strings?

At 15:29 01/09/01 -0700, Diane Hofstetter wrote:


>I'm just about to install my first set of Danny's strings in years.
>
>I forget, my "oldzeimers" is acting up again, I don't need to twist them,
>right?

I write as a restorer of 27 years standing and as a commercial bass string
maker.

My answer is that you should twist them and I'll give two reasons:

1.  When the stringmaker stretches the steel core on the machine between
the chuck and the hook, the wire is "flat", that is to say not twisted.  It
would be possible to pre-twist the wire and there may even be some
masochistic stringmaker somewhere in the world who does so, but I'll deal
with this question in a moment.  The stringmaker next proceeds to wind on
the copper covering wire.  The thicker the covering wire, the harder he has
to pull the copper as it is going on, in order that the wire may wrap
itself tightly round the steel core.  This tension is applied firmly and
evenly until the end of the second flattened portion of the core is
reached, at which point the wire is broken off.

The tension applied to the copper is, of course, less than the elastic
limit of the copper wire;  the wire is therefore elastic and stretched,
having the potential to restore itself to its natural length.  At the point
where the copper encounters the perimeter of the steel core it is suddenly
forced to change direction and the effect of this is to compress the under
part of the wire and stretch the upper part _beyond_ its elastic limit.

The wire, which was soft and pliable through the stringmaker's gloved hands
is now more brittle;  its cross-section is no longer round but rather
egg-shaped with one side of the egg slightly flattened against the
steel.  The lesser diameter of this egg is say 8% less than the original
diameter of the soft round wire.  But in spite of the trauma the copper
spiral has undergone, it retains some on the tension that was applied and
is trying to unwind.  This it cannot do because it is gripped at each end
of the steel by the flattened lengths of the steel and the ends of the
steel are gripped in the chuck and the hook of the machine.

What happens when the string is released from the chuck is that the
residual tension in the copper, now free to exert itself, twists the steel
core until the opposing action of the steel balances this force.  This
twisting (ie. unwinding of the copper) is clearly observable by the
stringmaker.  The actual degree of twist will vary according to the
relative thickness of the copper and steel wire; the thinner the core, the
less it will resist the twisting force of the copper.

Now this release of tension in the copper needs to be restored.  A properly
made string will not buzz even if the technician installs it without
twisting, but nevertheless the copper will not be as tight as it should be,
not as tight as it was wound by the experienced stringmaker, and AT LEAST
that twisting that occurs on releasing the string from the machine should
be restored to it.

2.  To be sure of regaining the lost tension, at least one whole turn would
need to be applied, but experience shows that the tone of a (new) string
will actually be improved by further twisting.  I personally give at least
two full turns to the thinnest strings and at least one full turn to the
thickest.  The great makers (of the past) vary in their practice but many
of them did roughly the same and after 120 years their strings still sound
good.

I don't believe this increased brilliance of tone can be explained simply
by the fact that the twisting tightens the winding, though this is
obviously a factor.  There are many contributory factors to piano string
tone and the most obscure of these is at the molecular level, for which
there is no exact science.  When a replacement bass string is first
installed, it will rarely sound as good as its neighbours, provided these
are in good order, and the difference can sometimes be so great as to lead
one to suspect the quality of the new string.  After two or three days and
one or two tunings, the difference will be scarcely perceptible.  After
eight days the new string will either match its neighbours perfectly or
exceed them in tone quality.  Any experienced tuner will recognize his
phenomenon.  The cause of it lies in the very gradual realignment of the
molecules in the steel and copper wire to accommodate to their new
stretched state, that same realignment that leads to the lowering in pitch
of newly-installed strings.

Finally, I said I would say a word about the possibility of "pre-twisting"
the cores before winding.  Certainly this would do no harm, but from the
stringmaker's point of view it is not only a waste of time but rather
pointless, since the technician who buys the strings will either know what
he is doing or not and no amount of molly-coddling is going to improve the
work of a ham-fisted technician.  I have one customer with a shop
locally.  Whenever I visit the shop, I like to hear the strings we have
made and judge the results in different pianos.  On every set he installs
there will be dark marks where the copper has been handled.  Every time, I
repeat my injunction to him and his son NEVER to touch the copper and
either learn to string without touching it or else wear gloves.  He will
not learn because he belongs to that superior cat-like breed of technicians
whose hands never sweat even in the summer!
JD