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Bulle & Eureka Parts & Restorations

The place to come for all your Bulle and Eureka restoration parts.

Code

Price

BU004

Material 0.15mmAlloy 36 (Invar)

Size 18 coils of 4mm, 2 half end coils at right angles

These Isochron springs are made as per the original Favre Bulle specification and Patent and differ from BU013 in that they are temperature compensating. But they do not appear to be the same material as found on actual clocks. Please read the Isochron story for a fuller explanation.

The Invar compensates for variations in battery voltage and temperature. They are made from Alloy 36 a material formerly known as Invar. It is a nickel-iron alloy which has a rate of thermal expansion approximately one-tenth that of carbon steel at temperatures up to 400°F (204°C). It is used for applications where dimensional changes due to temperature variation must be minimized such as clocks.

These Invar springs are less robust than the Stainless steel version and must be handled with care. The most common method of destroying these is when a “Repairer” forgets that it is connected to the pendulum and removes the latter by at least 4 feet before noticing that is somewhat reluctant to separate itself from the clock. You normally end up with a four inch long spiral of useless metal.

Each is supplied in a clear perspex box.

£7.00