The Lever Escapement

The escapement is the heartbeat of any mechanical timepiece: in its tick-tock oscillations, energy released from the mainspring is divided into tiny, regulated increments that govern the turning of the hands. In other words, it is where energy is turned into precise timekeeping.

In the classic Lever Escapement (found in almost all mechanical watches), the gear train carries power to an escape wheel; a pallet fork, governed by an oscillating balance wheel, unlocks the teeth of that escape wheel, which allows the gear train to advance incrementally, turning the hands. The Lever Escapement is robust, reliable and mechanically straightforward, but its Achilles heel is friction: lubricants are needed to alleviate this, but can eventually degrade and clog the parts. The holy grail of escapements, then, is one without friction.

Daniels’ Independent Double-Wheel Escapement (1974)

In the late 20th Century, Dr George Daniels rose to prominence as watchmaking’s greatest modern innovator. Daniels, who had authored the definitive book on Breguet’s watchmaking, determined to solve the shortcomings of the Natural Escapement. Whereas in Breguet’s formulation the escape wheels were geared to each other, one driving the other, Daniels separated them: he designed a separate gear train and mainspring for each, meeting in a single escapement. Daniels’ Independent Double-Wheel Escapement was precise, efficient and hugely elegant in its symmetry. It was also fantastically complex to build, and vulnerable to shocks. Whilst Daniels would use it for his pocket watch masterpieces including two astronomical ‘Space Traveller’ creations, it was too bulky, too complicated and too impractical a mechanism for the demands of a wristwatch.

Constant Force

As with the Daniels Independent Double-Wheel Escapement, the Central Impulse Chronometer features two independent gear trains, two mainsprings and two escape wheels. To this, Lederer adds a crucial further element: two remontoir d’égalité mechanisms, one for each gear train, to even out the flow of power to the escapement.  

The remontoir was an invention of John Harrison, the celebrated 17th century inventor of the marine chronometer, who first installed it in his H2 clock of 1739. In any timepiece powered by a mainspring, the energy delivered can vary as the spring unwinds. The remontoir counters this: it features a tiny spiral hairspring that’s wound up every few seconds by the mainspring, before delivering exact parcels of energy – what’s known as ‘constant force’ – to the escapement, buffered it from any variations in the mainspring’s energy release.

Conquering Inertia

The key escapement components are made from titanium instead of more traditional steel. Titanium is considerably lighter than steel, stiffer and with a much lower inertia, making it much more energy-efficient, and able quickly to restart after the kinds of shocks and jolts that are inevitable in a wristwatch.

Together with a 3 Hz oscillating frequency – as compared to the more stately 2Hz frequency of the Daniels escapement – these innovations ensure absolute precision and rate stability, even when shocks or abrupt movements impinge on the mechanism. Such jolts momentarily lower the amplitude of oscillations, and throw moving parts minutely off-kilter; the Central Impulse Chronometer minimises such impacts.