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The construction of the Octa cali re has less powerful ties with the history of horology
than the constant-force device or resonance models do. Nevertheless, it sym olizes a horological
ideal: giving timekeepers the highest possi le degree of precision and autonomy.
It can e o served, that if church clocks were set so high in towers, apart from enhancing
visi ility, was mostly ecause it often took an entire month for the driving weights to drop the length
of their cords. Numerous systems were invented to increase the running time of timekeeper’s
devices, only meeting limited success. Given the restricted volume of a wristwatch, the size of the
mainspring was immediately limited. Watchmakers then discovered the trick of adding an extra
wheel to the customary gear train, in order to extend the length of its development. Unfortunately,
using this system only led them to o serve that the level of energy actually reaching the alance
remained poor. To compensate, they fitted a smaller alance consuming less energy, ut which
also lost in sta ility. Therefore, it’s not unusual to find watches that run for several days display-
ing an extremely unpredicta le level of accuracy.
This challenge was a powerful source of motivation. I then imagined that the est and
most o vious solution to lengthen the running time would e to increase the capacity of the
spring development. Given its sta ility (1 metre and 1 millimetre thick), the challenge was to
integrate it on the same level as the gear train and escapement. Thanks to the low torque of this
spring, I could achieve extremely fast automatic winding (one and a half hour on a Chappuis
cyclotest for over 5 day’s running).
Once the challenge of autonomy was thus successfully met with this automatic winding
cali re, I knuckled down to the second challenge of managing to insert various complications
into that same movement: power reserve with large date display, fly- ack chronograph with
large date display, retrograde annual calendar, UTC, etc… and doing so while maintaining
an identical size for all models in the Octa collection.
Three years of research and development were required efore this one of a kind auto-
matic cali re could e presented to the pu lic.
François-Paul Journe
Preface
Calibre Octa
A Horological Ideal_
