These Isochron springs are made to the original design but are made from 0.15mm C902 steel instead of Invar. 18 coils of 4mm, 2 half end coils at right angles. They are the only springs that are consistent with the compositional characteristics of the original Bulle spring as shown in the laboratory test conducted over 2004 / 2005. The original patent specifies Invar, but this is much too soft for use as a spring. Each is supplied in a clear perspex box.
C902 is a nickel-iron-chromium alloy made precipitation hardened by additions of aluminum and titanium. The titanium content also helps provide a controllable thermo-elastic coefficient, which is the alloy’s outstanding characteristic. The alloy can be processed to have a constant modulus of elasticity at temperatures from -50°F to 150°F (-45 to 65°C).
(Ni SPAN C 902, Nispan C, UNS N09902; BS 3127; SAE AMS 5210, 5221, 5223, 5225)
Please see The Isochron Story, by clicking on the link below:
The price includes VAT & recorded delivery within the UK.
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