Audemars Piguet, even more so than Patek Philippe, largely owes its success to a single model line: the Royal Oak. While Geneva-based competitor Patek Philippe has more pillars to stand on – albeit less stable ones – than the famous Nautilus, Audemars Piguet has found it more difficult to diversify beyond the Royal Oak and put a successful dress watch on the market. It remains to be seen whether the brand really needs to do this, but the discontinuation of the stainless steel ref. 15202ST and the introduction of the CODE 11.59 collection show that AP is definitely aiming to expand their portfolio. In 2025, the CODE 11.59 collection is expected to account for 20% of the company’s revenue. Audemars Piguet offers much more than sporty three-hand models, as evidenced by its impressive catalog of highly complex timepieces from the recent past.
Ultra-Complication Universelle RD#4 – Highlight of the RD Series
The other two members of the unofficial haute horlogerie “Holy Trinity,” Patek Philippe and Vacheron Constantin, make multiple appearances in top 10 lists of the most complicated mechanical watches of all time. Vacheron Constantin in particular seems to have the goal of repeatedly breaking its own record for the most complications in an – admittedly bulky – case. Audemars Piguet, on the other hand, stubbornly refuses to enter the competition, where the bar is now set at 63 complications. However, this does not mean that the manufacturer shies away from complexity in their wristwatches. A prime example is the RD#4 Ultra-Complication, which has 40 “functions,” including 23 complications.
The RD#4 provides an excellent tour of the most interesting complications recently developed by Audemars Piguet. It incorporates key innovations from its predecessors in the RD series, i.e., the RD#1, 2, and 3, combining all the essentials into a single case and movement. It’s not the sheer number of these complications and functions that is of interest, but rather the unusual and innovative constructions with which some of them are realized. Thanks to its modular, layered construction, the RD#4’s movement is only 8.8 mm thick, which is exceptionally thin for a movement with such a large number of complications. Let’s take a closer look at the technological prowess of the caliber 1000, and how its predecessors in the RD line laid the groundwork for the newer watch.
The Striking Mechanism From the RD#1 Supersonnerie
Let’s start with the striking mechanisms, which are based on the proven and patented Supersonnerie technologies that debuted in the RD#1 in 2015, and were developed in collaboration with EPFL Lausanne. The most important innovation of this concept watch was attaching the gongs of the striking mechanism to a metal membrane, instead of the usual placement on the case or case back. Together with a resonance chamber in the form of a second, outer case back with several cut-outs, a particularly powerful sound is achieved. The Supersonnerie technology was later introduced in the Code 11.59 collection and, of course, was an essential addition (in a slightly modified form) to the “Ultra-Complication” RD#4.
In the RD#4, the outer case back come resonance chamber can be opened to reveal the movement inside. This is achieved by the design of the membrane, i.e., a sapphire glass disc surrounded by a metal frame to which the gong is attached.
Space-Saving Chronograph Design
Opening the case back reveals another design trick that contributes to the movement’s low overall height: connoisseurs will quickly identify the structure in the center as a split-seconds mechanism. It’s not just the mechanism itself that is so impressive, but its location embedded into the oversized ball bearing of the automatic rotor. Since the mass of the rotor contributes very little to the movement’s winding performance, the space that the rotor and split-seconds mechanism would each take up separately is halved or at least greatly reduced by combining them. The chronograph mechanism does not use the vertical couplings favored by aficionados, because the caliber 1000, with its diameter of 34.3 mm, offers ample space to accommodate numerous components in a single plane, rather than stacked vertically. Audemars Piguet takes a similar approach with the barrels, which are both housed on a single layer; one being responsible for the respectable 64-hour power reserve, and the second, smaller barrel powering the sonnerie. You aren’t afforded a view of the other layers of the movement up to the dial. The chronograph gears and levers are located beneath the rotor and split-seconds mechanism, followed by the actual base movement. The Grande and Petite Sonnerie are tucked away out of sight between the dial-level complications like the perpetual calendar, moon phase, and a flying tourbillon.
Perpetual Calendar From the Royal Oak RD#2 and a Compact Moon Phase
The perpetual calendar complication is again based on an existing RD timepiece, in this case the RD#2. The main innovation here is the two-dimensional design of the program wheel, which mechanically encodes the lengths of the months, in a single plane. Traditionally designed perpetual calendars require more height. Furthermore, the caliber 1000 perpetual calendar is equipped with numerous safety mechanisms and quick-adjustment devices, and theoretically only needs to be corrected after 400 years.
The former RD#2 made it into Audemars Piguet’s “conventional” collection as the Royal Oak Perpetual Calendar Ultra Thin, with the caliber 5133 standing at an incredible 2.89 mm, despite its automatic winding mechanism and calendar module. Given that the Jaeger-LeCoultre-designed base caliber 2120 is 2.45 mm tall, this leaves less than half a millimeter for the construction of the calendar module, including tolerances. No doubt this patented design is used in the RD#4 to minimize the overall height. Accommodating all the displays of the aforementioned complications on a single dial is a challenge in itself. Audemars Piguet came up with something very special for the moon phase in particular in order to find space alongside the flying tourbillon, calendar, and time displays. The patented design uses two concentric discs, each showing one half of the Moon – or its absence. The result is a compact moon phase that does not move continuously, but passes through ten images of the Moon in discrete steps.
Flying Tourbillon From the RD#3
The flying tourbillon, which is only mounted on one side, is inspired by the last in-house RD timepiece, the RD#3. The same watch was also the muse for the orientation of the tourbillon cage drive which helps to reduce the overall height even further, as demonstrated in the 3.4 mm flat caliber 2968 powering the RD#3.
With a diameter of 42 mm and a height of 15.55 mm, the RD#4’s dimensions that are far below those of many other highly complex wristwatches. This is partly due to newly designed, space-saving mechanisms, but also to the groundwork carried out by the previous RD timepieces. The RD#4 can rightly be considered a masterpiece from the complication experts at the new production facilities in Les Saignoles, which up until a few years ago was known as Audemars Piguet Renaud & Papi. At the GPHG 2023, this achievement was honored with the coveted Aiguille d’Or award.
