The information below is apparently not available in any published forum.
Physical rupture testing carried out in October & November 2020
Wire sizes are suitable for use in a small clavichord
Steel Music Wire
0.18mm diameter publ. max.: 6.10kg tested max.: 5.58 - safe max.: 4.98kg
0.19mm diameter publ. max.: 6.79kg tested max.: 5.07 - safe max.: 4.52kg
0.21mm diameter publ. max.: 8.30kg tested max.: 7.35 - safe max.: 6.55kg
0.22mm diameter publ. max.: 9.11kg tested max.: 8.01 - safe max.: 7.14kg
0.23mm diameter publ. max.: 9.95kg tested max.: 10.15 - safe max.: 9.05kg
0.25mm diameter publ. max.: 11.76kg tested max.: 11.99 - safe max.: 10.69kg
Figures in red are where the published figure is higher than the tested maximum tension.
"Tested maximum" indicates the tension at the semitone point at A440hz which the string
sustained immediately below the rupture point.
The "safe max", minus 2 semitone figure seems to be a safe working maximum tension. JG
Phosphor Bronze wire
V 0.211mm diameter publ max.: 3.032kg safe max.: 1.578kg
V 0.235mm diameter publ. max.: 3.637kg safe max.: 3.005kg
V 0.248mm diameter publ. max.: 4.297kg safe max.: 3.55kg
V 0.277mm diameter publ. max.: 4.823kg safe max.: 4.823kg
V 0.309mm diameter publ. max.: 6.188kg safe max.: 5.74kg
V 0.326mm diameter publ. max.: 7.307kg safe max.: 6.8kg
H 0.35mm dia. publ. max.: -- safe max.: 8.1kg
V 0.364mm diameter publ. max.: 9.11kg safe max.: 6kg
H 0.4mm dia. publ. max.: -- safe max.: 9.1kg
H 0.445mm dia. publ. max.: -- safe max.: 11.303kg
H 0.5mm dia. publ. max.: -- safe max.: 11.342kg
H 0.56mm dia. publ. max.: -- safe max.: 12.655kg
V = Vogel CuSn6 H = Heckschers Phos Bz
The rupture testing was carried out on a beam of wood mounted with a wrest pin at each end--574mm apart.
The string was then tensioned and its pitch noted as it attained each semitone at A440hz.
Two semitones below the point of rupture was noted, and this is the "safe max" figure, to allow for a safe seasonal rise of one semitone.
