The latest Advanced Research timepiece from Patek Philippe has arrived. This series of watches is akin to concept cars that various marques release from time to time to showcase new technical and design advancements, and the Geneva manufacture had released only four of them since 2005, with this Aquanaut Travel Time Ref. 5650 being the fifth. The watch showcases two main improvements in watchmaking technology: a new hairspring design, and a new flexible mechanism in traditional steel.

Aesthetically (and functionally), the timepiece is largely similar to the existing Aquanaut Travel Time Ref. 5164, with general symmetry along both axes. To reflect the times in two different cities, two hour hands are used, with an aperture for each one to indicate day/night. Meanwhile, the date, which is tagged to local time, is shown via a sub-dial at six o’clock. Where the new Advanced Research timepiece differs is the massive aperture on the left of the dial; the opening shows off the new flexible mechanism, which is one of the two technical highlights in this watch.

Aquanaut Time Travel Ref. 5650

The flexible mechanism is, as its name suggests, a mechanism that works based on the flexibility of materials. This isn’t a new concept, but its usage is novel to watchmaking, which has traditionally depended on levers and pivots to create articulating mechanisms to transfer forces. In the Ref. 5650, the flexible mechanism is used to adjust the local time’s hour hand, and consists of the entire crab-like structure exposed by the dial’s cut out. Note the four “crosses” on the structure – each is a pair of leaf springs that cross over each other, with just 0.15mm between them, and together they are responsible for transferring each pusher’s actuation into a correction in the local time’s hour hand. There’re several advantages to such a system: fewer parts are needed (12 instead of 37) which translates to faster assembly (just four screws are used), a reduced height for the mechanism from 1.45mm to 1.24mm, and the elimination of friction that causes wear and tear. Since the mechanism is entirely crafted in steel, it can also be finished using traditional methods. Of course, the flexing of the leaf springs must be below a certain amplitude, so material fatigue will not occur.

Aquanaut Time Travel Ref. 5650

Flip the watch around, and the second major advancement shows itself – the new Spiromax balance spring. This hairspring’s material is still the silicon that Patek Philippe developed as part of a consortium that also included Rolex and the Swatch Group. What’s changed is its geometry. In addition to the outer terminal curve (a slight misnomer, since it is flat and just widens, rather than curving upwards like the Breguet overcoil), the innermost coil has now been widened as well. Patek Philippe terms this the “inner boss”, likely a translation issue from the French word “bosse”, which means bump. Whatever the nomenclature, the changed inner profile is, according to the manufacturer, crucial in improving the concentric breathing as the spring expands and contracts. The principle behind this is simple: because of its shape a spring’s centre of gravity varies as it expands and contracts, so compensation is needed to reduce this shift in its centre of gravity, which exerts an uneven force on the balance wheel. A silicon hairspring, however, cannot be bent to form the Breguet overcoil, so modified profiles are needed, with this being the latest one. The change is quantifiable: Patek Philippe is regulating this timepiece to an astonishing -1/+2 seconds per day.

Aquanaut Travel Time 5650 Specifications

Movement Self-winding Patek Philippe Caliber 324 S C FUS with date, second time zone and day/night indications; 35-hour power reserve (minimum)
Case 40.8mm in white gold, water resistant to 120m
Strap Blue composite strap with deployant clasp in white gold

This article was originally published in WOW.