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Subject:
From:
John Larson <[log in to unmask]>
Reply To:
Harpsichords and Related Topics <[log in to unmask]>
Date:
Mon, 20 Nov 2017 11:45:07 -0600
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I'm not qualified to comment on the wire gauges and materials, but is it 
possible that the core became twisted by turning more revolutions at one 
end than at the other?

   John


On 11/20/2017 11:34 AM, Phillip Allen wrote:
> Hi All,
>
> I am “almost” finished buildinng my first clavichord, a Hubert 1784 (serial
> #8604) drawn by Loucks (1974) / revised Loucks (1977 & 1981) that I
> purchased from Friends of St Cecilia’s Hall in Edinburgh. From the
> temperament question I posted last week I have decided to tune it to 440
> equal temperament.
>
> I built a wooden string winding lathe to make the 22 over-wound strings and
> it seems to work quite well. The stringing schedule for these 22 over-wound
> strings is appended below. The 0.016” yellow-brass strings were purchased
> from The Instrument Workshop (http://www.fortepiano.com/) while the copper
> covering (110 Copper wire) from McMaster-Carr (www.mcmaster.com). Since
> there was no 0.015” Cu wire I substituted 0.016” Cu-wire.
>
> The general procedure was:
>
> 1. Hitch-pin loop on each end (main & sacrificial/temporary)
>
> 2. Mark with a sharpie pen area over tangent & bridge
>
> 3. Tension wire on Lathe, using PitchLab ~45hz F#1,
>
> 4. Loop Cu-wire through main hitch-pin loop, tag-end wind along helix for
> 1cm to anchor it.
>
> 5. Start the over-wound spiral using a piece of leather to hold the
> tension. In the middle the tension normally deflects the yellow-brass core
> wire 2-3cm from its center line. I hope that makes sense since I have no
> idea of lbs/kg of force that I am putting on the Cu-wire.
>
> 6. Cu-wire is wound as an open spiral over the entire length but wound
> closed over were the tangents and bridge are marked out with a sharpie pen.
>
> 7. Lathe tension was removed and the sacrificial/temporary loop cut off.
>
> The over-wound strings look real good just like pictures on the internet of
> store-bought strings! They even sound very nice.
>
> Of the 22 made I have broke more than 12 of them trying to tune them! They
> keep breaking right at the tuning peg. Typically they are breaking two full
> notes below (need F# and break when they get to E or F). So far I have
> managed to splice a piece of 0.018” yellow-brass to the broken end for two
> strings and get them tuned up. No such splicing luck for the others.
>
> I have just made another wire and tightly/close wound the Cu-wire all the
> way from the bridge past the tuning pin thinking the Cu was weakening the
> yellow-brass as it rests on the tuning peg. It also broke like the others.
>
> So what am I doing wrong?
>
> Should I switch to some sort of iron wire core?
>
> Is the Cu-wire the problem?
>
> Is the wire-core or over-wound tension while winding wrong?
>
> Thanks for any suggestions to resolve this problem. The winding lathe is
> hand-crank operated and my girlfriend is getting tired of turning this
> stupid crank!
>
> Phil
>
> String # Note #1 Speaking Length_1 Yellow_Brass_Core Cu_Wrap
> 1 C 1097 0.016 0.016
> 2 C 1097 0.016 0.016
> 3 C# 1082 0.016 0.016
> 4 C# 1082 0.016 0.016
> 5 D 1069 0.016 0.012
> 6 D 1069 0.016 0.012
> 7 Eb 1054 0.016 0.012
> 8 Eb 1054 0.016 0.012
> 9 E 1038 0.016 0.012
> 10 E 1038 0.016 0.012
> 11 F 1022 0.016 0.012
> 12 F 1022 0.016 0.012
> 13 F# 1007 0.016 0.012
> 14 F# 1007 0.016 0.012
> 15 G 986 0.016 0.012
> 16 G 986 0.016 0.012
> 17 G# 968 0.016 0.010
> 18 G# 968 0.016 0.010
> 19 A 948 0.016 0.010
> 20 A 948 0.016 0.010
> 21 Bb 923 0.016 0.010
> 22 Bb 923 0.016 0.010
>
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::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Note:  opinions  expressed on HPSCHD-L are those of the  individual con-
tributors and not necessarily  those of the list owners  nor of the Uni-
versity of Iowa.  For a brief  summary of list  commands, send mail to
[log in to unmask]  saying  HELP .
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