With its large number of moving parts, the mechanical wristwatch was made to measure for the young and cutting-edge science of tribology
The study of friction, wear, lubrication and how moving surfaces interact. A modern, precision timepiece might simply grind to a halt without the holistic vision of tribologists and their ability to make components spin, slide or grip to perfection.
Tribologists often say that only one watch component rightfully escapes their attention: the dial. It is static, untouched by other moving components and protected from wear and tear. Otherwise, the watch movement and its tiny moving parts, the case, bezel, crystal, the bracelet and clasp, as well as production processes, machinery, tools and lubricants, all come under the scrutiny of these Renaissance men and women. Their science combines the knowledge of the engineer, the chemist and the watchmaker. Today, dedicated teams of tribologists at Rolex are key to raising reliability, accuracy and comfort to unprecedented levels.
Tribology only emerged between the late 1960s and 1980s with growing understanding of the multiple effects of stress on materials used in high-technology engineering industries. Nonetheless, some of the principles of this multi-disciplinary science have been applied unwittingly for centuries. When pioneering watchmaker John Harrison created the first ultra-precise timepieces, marine chronometers, in the 18th century, in order to minimize the impact of friction, he went to great lengths to make the first-ever clockwork mechanisms that did not need lubrication. At the time, oils were of poor quality, made of animal or vegetable fats that deteriorated quickly, limiting their efficacy for vital navigational instruments on the high seas.
Yet, it is only on the threshold of this millennium that new science evolved and came to complement the watchmaking craft in a systematic manner. Applied to the mechanical movement, tribology has a fundamental impact on precision, longevity and the very functioning of a watch.
Applied to the case and bracelet, it influences comfort, quality and aesthetics. Its impact is evident to the user, ranging from the reassuring click and feel of the Oysterlock clasp on a Rolex watch when it is opened and shut, to the latest new-generation movement, which extensively resorts to tribology in order to set new standards of precision.
Initially, tribologists were often employed as problem solvers, a baffling task that demands enormous patience because the suspect component itself – and therefore the evidence – may have been destroyed by wear. However, the biggest evolution over the past 15 years has been their intervention in research and development, when materials are chosen and parts are designed.
The newest watch movements are manufactured to extremely fine tolerances equivalent to those found in the aerospace industry. Scaled down to the infinitesimally small size of spinning staffs or gear wheels, the forces involved in friction and wear are immense.
The pressure on ruby bearings or the teeth of a gear wheel is equivalent to that exerted by a locomotive on its rails. Each tick of a watch corresponds to an impulse given by the escapement and therefore a moment of friction and wear: there are some 250 million of them a year in a Rolex watch. The contact patches between moving surfaces, however, can be tiny: a few microns.
In the 18th century, hard rubies were first used as bearings in watchmaking to minimize the destructive wear caused by friction on brass pivots. Equally, without highly developed, long-lasting oils, today’s high-precision mechanical watch movement would seize up within a fortnight, leaving a mass of metal shavings.
These high-performance lubricants are synthesized under the guidance of tribologists, replacing oils or greases derived from animal hooves that were still on the shelves about a decade ago. Rolex is the only watchmaking brand that develops and makes its own range of lubricants in-house at a specialized laboratory. Each type of oil has a specific application and requires about a decade of R&D. Low viscosity, or thinner, lubricants are used for high-speed contacts, such as in the oscillator. High viscosity, or thicker, ones are employed in high-pressure, impacting contacts such as the gear trains.
The quantities used are breath-takingly small. Just 100 litres of specialist lubricants, approximately, are thought to be consumed by the whole Swiss watch industry each year. Mere microlitres of lubricants are applied to each single Rolex movement across 50 to 100 lubrication points, depending on the model. Since tribology came into play, each drop is scientifically calculated and applied by skilled operators using a type of automated syringe in order to ensure the right dose. Too much oil can lead to moving components sticking or being slowed down. Too little increases wear and friction.
But the huge range of criteria taken into account doesn’t stop there. Nanometric coatings called epilames may be used on part of a component to modify surface tension and ensure the lubricant stays in place or in a given area. Even the shape and curvature of a microscopic drop of oil is carefully considered. For example, a purely spherical droplet might roll out between two surfaces in due course instead of cushioning them.
Sometimes a degree of friction is desirable. For example, the mechanics of a rotatable bezel are carefully designed and balanced. Even the shape and geometry of the characteristic fluting of a Sky-Dweller’s bezel were studied to ensure the ideal grip for the user.
Tribologists have such an acute sense of precision that they rarely speak of the smoothness of metal but of its roughness, because they know that even a polished surface examined under an electron microscope is never as smooth as it looks to the eye or feels to the fingertip. Satin-finish surfaces are also analysed by tribologists to ensure they do not become polished with wear.
But the most outwardly obvious fruit of the advent of tribology may be found on the bracelet. In platinum and gold Oyster bracelets, and the President bracelet, notably on the new Day-Date, ceramic inserts were developed and placed inside each link to reduce the wear that may develop when the surfaces rub, due to the inherent characteristics of each metal. The inserts also ensure an exceptionally supple fit for the bracelet. Lubricants would have been unsatisfactory because they would swiftly wash off such an exposed part of the watch, and stain the wearer’s clothes.
With such scope, it is not surprising to find that many of these specialists have completed advanced study beyond degree level. Their working day is governed by methodical and rigorous science, yet tribologists are ultimately romantics at heart: they are matchmakers, who marry materials and moving parts to work together in perfect harmony.
The tribologist combines the knowledge of the engineer, the chemist and the watchmaker.