An in Depth Look at our Natural Escapement
Controlling the flow of time
All mechanical watches contain a means of storing energy (usually a barrel containing a mainspring), a series of gears to transfer energy (gear train) and a means of dosing that energy to ‘control the flow of time’ (escapement).
Swiss lever escapement
For generations, watchmakers have continuously obsessed over perfecting the escapement as they seek to improve chronometric performance, rate stability, shock-resistance and efficiency. Typically, most mechanical watches on the market today feature a Swiss lever escapement, a modern-day take on the English lever escapement invented by Thomas Mudge in 1754.
The Swiss lever escapement, a form of ‘detached escapement’, allows the balance to swing freely throughout most of its oscillation except when the escape wheel is serving an impulse. This method of ‘controlling the flow of time’ is reliable and easy to both service and regulate.
The Swiss lever escapement has two weaknesses. As the escape wheel rotates clockwise, its teeth engage with two ruby pallets (the entry pallet and the exit pallet). The teeth slide along the face of the entry pallet, which ultimately provides the impulse, effectively pushing the pallet lever upwards. This action causes the lever to pivot and provides momentum to the balance (an indirect method of serving the impulse). This sliding action creates friction, reducing the efficiency of the mechanism. Moreover, this friction necessitates using a lubricant; however, lubricants inevitably deteriorate with time; one of the reasons for having a watch regularly serviced.
The natural escapement - a highly efficient mechanism
In 2012, Laurent Ferrier released a watch equipped with an automatic movement, the Calibre FBN229.1. This movement was unusual in that it featured a micro-rotor and, even more remarkably, a natural escapement.
In itself, the natural escapement is not a new concept. In 1802, Abraham-Louis Breguet completed a watch featuring the échappement naturel (natural escapement). Breguet’s system imparts momentum to the regulating organ by serving the impulse directly from the escape wheel to the balance axis. As the escape wheel only rotates clockwise, it can only serve an impulse in one direction. Clearly, for the balance to oscillate it needs an impulse in both directions, hence the natural escapement addresses this issue by having two escape wheels.
Wheel A (the driving escape wheel) is powered by the mainspring via the gear train and turns clockwise. It turns the second wheel, Wheel B (the driven escape wheel) which rotates in a counterclockwise direction.
Small columns are integrated into the upper surface of each escape wheel. These columns impulse the double table roller, part of the balance. The lever located between the escape wheels provides a resting point for the columns, similar to the pallets found on a Swiss lever escapement.
However, Breguet discovered that the play between the escape wheels caused ‘backlash’. Excessive play could lead to a variable impulse being served to the balance or cause the escapement to halt. On the other hand, too little play would lead to excessive friction.
Laurent Ferrier Calibre FBN229.01 – natural escapement
Laurent Ferrier surmounted the problem of ‘backlash’ by positioning the driving wheel (A) asymmetrically against the driven wheel (B) and optimising the geometry and gearing to minimise the amount of play between the escape wheels while at the same time still leaving just enough play.
Moreover, the Maison was able to overcome the problems that Breguet discovered by utilising modern-day technologies and materials. For example, the escape wheels are made of nickel phosphorus, formed using UV-LIGA technology. This cutting-edge technique involves using UV light to create a microscopic mould that is then used for effectively growing parts with a high aspect ratio. The aforementioned columns are integrated into the upper surface of each escape wheel, made to infinitesimal tolerances that are impossible to achieve using regular moulding or CNC. The resultant escape wheels are both smooth and strong.
A further example where Laurent Ferrier utilised state of the art technology relates to the use of silicium. This lightweight glass-like material is made using DRIE (Deep Reactive Ion Etching). The Maison has made the lever and double table roller from silicium, culminating in parts that are virtually friction free, thereby sidestepping the need for lubricants.
By utilising modern-day materials and technologies, Laurent Ferrier has been able to create a lightweight escapement. The mechanism needs less inertia to move components, making it more efficient, mitigating energy consumption.
Closing remarks
When Breguet created his échappement naturel in 1802, his objective was to avoid using lubricants and achieve superior chronometric performance. His approach was logical, but his aspirations were frustrated by the materials available to him at the time.
The Laurent Ferrier natural escapement is similar in many ways to Breguet’s approach but embraces cutting-edge materials and technology. The resultant automatic movement (Calibre FBN229.1), equipped with a micro-rotor, proves incredibly efficient.
So, why don’t all watch companies use a natural escapement? The answer is simple, it takes much time and expertise to fine tune the system in order to make it operate perfectly, factors which preclude mass production. However, Laurent Ferrier is the very antithesis of mass production. The independent company subscribes to low-volume production methods, is blessed with incredible in-house watchmaking expertise and believes in taking its time. It is for these reasons, that the Maison has been able to bring the natural escapement to life.
