atch construction and engineering are one thing (one highly complex thing – and we’ll come back to that presently), but ensuring the legibility of the indications served up by the interior workings to the exterior, is another thing altogether. From the point of view of the person wearing the watch, looking at it and pressing its buttons, the display takes priority over any other consideration, in terms of both readability and precision. This is particularly true when, as in this case, the point is to freeze, display and read – instantaneously and intuitively – a time measurement to the nearest tenth of a second. Which is barely any time at all.

The red central 1/10 second hand of the Ref. 5470P Monopusher Chronograph performs one sweep around the deep blue dial every 12 seconds. Every second, the hand passes over one of the twelve one-second sectors on the railway track scale around the outside edge of the dial. Each segment of the scale is marked off with a red subdivision clearly divided into 10 sections – or ten tenths of a second.

Never has it been so simple, precise or intuitive to read tenths of a second off a mechanical chronograph.

When the chronograph is activated, two central hands are simultaneously set in motion. The black seconds hand sweeps around the dial in 60 seconds, while the 1/10 of a second hand performs one revolution every 12 seconds. When they are stopped, the user can intuitively read off the number of seconds shown on the pearl markers by the black hand, and the number of tenths shown by the red hand against the railway track scale. Minutes are read off the instantaneous 30-minute counter at 3 o’clock, and elapsed seconds are displayed on a subdial at 9 o’clock.

Never has it been so simple, precise or intuitive to read tenths of a second off a mechanical chronograph. To achieve this result, the engineers and watchmakers of Patek Philippe’s Research & Development department, led by Philip Barat, had to use all their ingenuity. For proof, one need look no further than the seven patents registered for the new CH 29-535 PS 1/10 calibre that equips this monopusher chronograph, Patek Philippe’s first ever wrist chronograph to display tenths of a second.

A little history

While this is indeed the first Patek Philippe bracelet chronograph to display tenths of a second, the origins of the watch can be traced back to the Geneva maison’s long and illustrious history. As early as 1856, the watchmaker earned a reputation for its excellent pocket chronographs, with or without flyback mechanism, often paired with perpetual calendars or minute repeaters. In 1930-1931, Patek Philippe produced a pocket watch with a 1/10th of a second chronograph. In 1923 the first wrist chronograph with on-demand flyback was unveiled, followed in 1927 by the first series manufactured wrist chronographs, with or without rattrapante hands.

The first step, then, was to increase the frequency, taking it up to 5 Hz or 36,000 vph, which is ten per second. The next step was to design the most perfect and legible display possible. A single hand rotating at a frequency of 5 Hz, moving in 1/10th of a second increments, would not be capable of displaying tenths of a second with the precision and legibility required, because there’s not enough room to actually show the ten divisions within each second.

In 1923 the first wrist chronograph with on-demand flyback was unveiled, followed in 1927 by the first series manufactured wrist chronographs, with or without rattrapante hands.

Ref. 5470 P-001 1/10 Second Monopusher Chronograph. Case in 950 platinum. 41 mm x 13.68 mm. Calfskin strap with embossed textile motif.

Moving closer to the present, by 2005 Patek Philippe had designed, developed and manufactured entirely in-house a full range of chronograph movements, from the simple to the complicated, with flyback hands, minute repeaters, perpetual calendars, annual calendars and World Time. Today there are more than twenty versions in the current collection, for both men and women. In its way, the 5470P-001 1/10th Second Monopusher Chronograph, which takes its place in the Complications collection, represents the pinnacle of this long history.

The patient quest for legibility

The history of the 1/10th Second Monopusher Chronograph actually began ten years ago. The need for a thinner calibre, one of the defining features of Patek Philippe watches and something Thierry Stern takes extremely seriously, required a lengthy period of research.

It started with a chronograph movement developed by Patek Philippe earlier this century; the CH 29 535 PS calibre, launched in 2009, is a hand-wound column wheel calibre with horizontal clutch, featuring two central chronograph hands in its rattrapante version, incorporating six patented innovations. But, like all the maison’s wrist chronograph movements, this calibre beats at 28,800 vibrations per hour (4 Hz), which is eight per second. This is perfect for calculating eighths of a second, but not tenths.

In its way, the 5470P-001 1/10th Second Monopusher Chronograph, which takes its place in the Complications collection, represents the pinnacle of a long history.

The first step, then, was to increase the frequency, taking it up to 5 Hz or 36,000 vph, which is ten per second. The next step was to design the most perfect and legible display possible. A single hand rotating at a frequency of 5 Hz, moving in 1/10th of a second increments, would not be capable of displaying tenths of a second with the precision and legibility required, because there’s not enough room to actually show the ten divisions within each second.

To create a perfectly legible display, Patek Philippe’s designers developed an innovative solution: give the CH 29-535 PS 1/10 calibre two independent, but coordinated, chronograph mechanisms: one for the seconds and instantaneous 30-minute counter, and another exclusively for displaying the tenths.

An immediate, intuitive reading

The two concentric hands – one for the seconds and the other for the tenths – each driven by their own independent mechanism, make it possible to read off the desired time measurement instantaneously. The seconds (whose black hand performs one revolution of the dial in 60 seconds) are displayed in the traditional fashion, while the red 1/10th hand takes 12 seconds to complete its tour of the 12 graduated sections divided into tenth-of-a-second increments. With a quick glance, the wearer can read the seconds off the pearl markers, and the tenths on the outer railway track scale.

But while the display itself is intuitively simple, the integration of a second mechanism to guarantee the precision of the 1/10 of a second display throughout a 30-minute chronograph activation period, required considerable research to find innovative solutions. The first challenge was to supply the energy required to ensure stable operation of the dual mechanism. The single barrel was optimised by reducing the diameter of the central barrel arbor and increasing the number of mainspring coils. To compensate for the increased forces on the system, a patented notch eliminates the risk of damage as the mechanism is wound.

While the display itself is intuitively simple, the integration of a second mechanism to guarantee the precision of the 1/10 of a second display throughout a 30-minute chronograph activation period, required considerable research to find innovative solutions.

Precision and stability

In order to ensure the highest precision and stability, Patek Philippe decided to incorporate the Oscillomax ensemble unveiled in 2011, the subject of 17 patents, which has hitherto been reserved for the Patek Philippe Advanced Research 5550 P Perpetual Calendar introduced in 2011. This is the first time it has been used in a regular collection.

This high-tech regulator mechanism based on the Silinvar^® silicon derivative technology includes a Spiromax^® balance spring, a Pulsomax^® escapement and a Gyromax^® balance wheel with gold inserts. Despite the considerably higher energy consumption, it guarantees a maximum deviation of -3/+2 seconds per day (a requirement of the Patek Philippe Seal) and a minimum 48-hour power reserve (with chronograph deactivated).

The first challenge was to supply the energy required to ensure stable operation of the dual mechanism.

Eliminating irregularities

A huge amount of research went into synchronising the two hands and making their motion as fluid as possible. The result was a highly innovative 1/10 driving wheel which is the subject of a European patent submission (EP3042250A1). As well as synchronising the two hands, it prevents any jumps or vibrations in the 1/10 hand, which must operate perfectly smoothly to ensure the absolute precision required.

The solution was an innovative dual-layer wheel, with flexible spokes on the upper part and rigid spokes on the lower. The elasticity of this anti-backlash system completely eliminates the risk of vibration in the hand, which flies around the dial in just 12 seconds.

It also ensures a precise display. When the chronograph is activated, this driving wheel, which performs one rotation every 60 seconds, meshes with the 1/10 of a second pinion, which rotates five times faster, i.e. it performs one revolution every 12 seconds. This considerable acceleration is made possible by microtoothing: this vital pinion has 136 teeth in its 1.469 mm diameter, and a tooth height of 30 μm.

The “mechanical filigree” of the CH 29-535 PS 1/10 calibre elegantly marries classic architecture, cutting-edge mechanical innovation and a high-tech oscillator. Chamfered bridges, polished edges, Côtes de Genève and manual finishes are executed in the maison’s finest horological tradition.

Acceleration + shock absorption

Acceleration is key, but shock protection is also vital. This calibre is sporty by design, and thus subject to the possibility of all kinds of shocks. It must be able to effectively withstand some rough treatment.

A patented shock absorber hook maintains the chronograph clutch rocker in place during operation, protecting it from any disturbance. A second patented mechanism employs a pendulum system that uses the components’ centre of gravity to compensate for accelerations on the components. Rather than accumulating, the shocks cancel each other out, and the components remain in position.

Rather than accumulating, the shocks cancel each other out, and the components remain in position.

A classic, sporty appearance

If the CH 29-535 PS 1/10 calibre is all about high-tech innovation, architectural accomplishment and timeless finishes, the external appearance of the Ref. 5470P Monopusher Chronograph is an ode to perfect clarity and intuitive design. The blue of the dial, red accents, and the strap made not from textile but from elegant calf leather with an embossed textile motif, all point unequivocally to the sporty vocation of this watch.

And it is immediately obvious that concern for the wearer’s experience – ease of use, precision, a clear display and comfortable ergonomics – were central to the design, construction and realisation of this timepiece.

All these elements come together to create an elegant and efficient experience in use. The monopusher at 2 o’clock, a throwback to classic chronograph codes, offers superlative precision and an intuitive way to start, stop and zero the timing mechanism.

It is located at 2 o’clock on the side of the platinum case (reinforced by the ritual diamond at 6 o’clock) with its smoothly rounded lines, concave bezel, recessed satin-brushed flanks and gently curved lugs, recalling the shape of the manual flyback chronograph Ref. 5370 from 2015.

If the CH 29-535 PS 1/10 calibre is all about high-tech innovation, architectural accomplishment and timeless finishes, the external appearance of the Ref. 5470P Monopusher Chronograph is an ode to perfect clarity and intuitive design.

There’s one last detail, and it’s certainly not the least. Set against the blue dial with its applied 18K white gold Breguet numerals and pearl markers, the red 1/10 hand is a distillation of technological accomplishments. While the running seconds hand is in classic sandbrushed rhodium-plated steel, the 1/10 hand is made from Silinvar^®. This light and stiff material was chosen specifically for its ability to withstand shocks, and marks the first time Patek Philippe has used this material for an external component. The method used to attach the Silinvar^® hand is the subject of yet another patent, as is the specific coating technique employed here to create the red lacquered finish.

When deactivated, the two hands sit perfectly together, the 1/10th hand sliding underneath the second hand. When the chronograph is activated, they both spring instantaneously into action, the red quickly outstripping its partner, eating up the dial at a rate of 12 seconds per lap, while the second hand trots along behind at a steady sixty seconds per rotation. This fascinating spectacle of short-time measurement is a feast for the eyes.