Constant Force Tourbillon 11 Platinum

Constant Force Tourbillon 11, Platinum Edition
The essence of a 260-year heritage
With their new interpretation of the Constant Force Tourbillon 11 Platinum, Arnold & Son pay tribute to the watchmaking genius of the House’s founder. This platinum edition represents the final opus of the Constant Force 11 collection – launched with the gold model – and crowns the celebration of 260 years of heritage. It also celebrates the magic of nature with a dial ornamented with a hand-guilloché surface in the “tremblé” style, evoking the fern-covered moors around Tintagel in Cornwall – the birthplace of John Arnold and setting for the legendary adventures of King Arthur.  

Adorned with new refinements, the Constant Force Tourbillon 11 was purposefully designed by Arnold & Son to honour the timepiece that Abraham-Louis Breguet presented to John Roger Arnold in 1808. Now conserved by the British Museum, this historic timepiece, based on John Arnold’s No. 11 chronometer, is believed to be the first tourbillon-regulated watch made by Abraham-Louis Breguet after he filed the patent in 1801. 

A fern-covered dial
The Constant Force Tourbillon 11 platinum edition features a distinctive solid gold dial. The fine detail of the “tremblé” is expertly crafted by hand with a burin engraver. Under the controlled motion of the tool, the sharp tip has traced a succession of artfully irregular zigzags. This organic pattern is surprisingly harmonious and takes its inspiration from the wild moors of Cornwall, where ferns curl in fleeting arabesques as the sea winds blow. Each etched curve seems to capture the soul of this mystical land, the birthplace of John Arnold and home to Arthurian legends. The engraving weaves a poetic tie between the master’s watchmaking heritage and the elemental forces that shaped his childhood. The wind, the dancing ferns and the famous mists – all the magic of Cornwall – are reflected in the golden dial, transforming timekeeping into an ode to nature and history. 

The dial is meticulously pierced to accommodate the white opal hour and minute subdial, as well as the mechanism delivering constant force to the tourbillon cage. The latter can be seen under an 18-carat gold bridge and rotates in exact, one-second increments. This rhythm is far from insignificant as it carries the legacy of marine chronometry when each second counted was a longitude reclaimed from the ocean. 

A timekeeper’s testament
The classically shaped, rounded case measures 41.5 mm in diameter. Crafted in platinum, it appears exceptionally slender on the wrist. On the dial side, it is fitted with a delicate bezel framing a domed sapphire crystal with an anti-reflective coating on both sides. On the reverse, it features a sapphire case back through which the bridges and the tourbillon of the in-house manual winding A&S5219 calibre can be seen. Water resistant to 3 bar, the watch is worn on a hand-stitched midnight blue alligator leather strap, fastened with a platinum folding clasp. 

A constant force mechanism
To ensure perfect isochronism throughout its 100-hour power reserve, Arnold & Son have positioned their patented constant force mechanism between the main gear train and the tourbillon. Visible on the dial, this ingenious system regulates the energy from the barrels, eliminating any variations in torque that could disturb the balance’s oscillation. Second after second, it rearms a finely adjusted spiral guaranteeing a completely stable transmission of energy to the tourbillon cage. The precise choreography of this constant force mechanism is magnified by an 18-carat gold bridge, emphasising the watchmaking excellence.

The constant force mechanism replaces the group of components known as the “fusée-and-chain” that John Arnold used in his chronometers. The advantage of this system is that it not only delivers a constant force to the regulating organ, it also produces a true-beat seconds display. The seconds are not indicated by a traditional seconds hand, but by the tip of the hand-blued anchor, which simultaneously serves as a structural bridge for the constant force mechanism. 

A balanced tourbillon
This final limited series of 11 pieces pays tribute to the legendary friendship between John Arnold and Abraham-Louis Breguet. Its sapphire case back reveals the A&S5219 calibre, whose architecture is directly inspired by the first regulator with tourbillon created by Abraham-Louis Breguet. This chef-d'oeuvre, housed in the British Museum, was inspired by Arnold’s No. 11 chronometer and offered to his son in 1808. The Constant Force Tourbillon 11 revives this watchmaking bond: its tourbillon cage faithfully reproduces the original design. With extremely pure lines, the tourbillon features a distinctive and remarkably delicate linear, mirror-polished and rounded cage bridge, revealing a variable-inertia balance whose design draws on John Arnold’s most accomplished chronometers. In this true dialogue across time, every component speaks to the extraordinary union of two masters of timekeeping.

A celebration of friendship
The finishing of the main plate, bridge and tourbillon cock is virtually identical to that of the very first tourbillon. To complete the tribute, Arnold & Son have included hand-engraved inscriptions on the barrel bridge and added the famous plate on which another homage has been engraved: “To the revered memory of John Arnold and Abraham-Louis Breguet. Friends in their time, legendary watchmakers always.”. This inscription definitively gives the Constant Force Tourbillon 11 its place in a unique historical saga: one in which the friendship between two geniuses gave rise to some of the most remarkable advances in chronometry.

Technical specifications

Functions

• hours, minutes, true-beat seconds

Movement

• Calibre: A&S5219 hand-wound mechanical movement, constant force, one-minute tourbillon
  
• Jewels: 35
  
• Diameter: 33 mm
  
• Thickness: 10.48 mm
  
• Power reserve: 100 hours
  
• Frequency: 3 Hz / 21,600 vph
• Finishes:
  mainplate: 3N golden finish, grained, polished angles
  barrel bridge: 3N golden finish, grained, polished angles, stretched edges, hand-engraved
  tourbillon bridge: golden finish, grained, polished angles, stretched edges, satin-finished Durnico steel retaining spring 
  screws: blued, chamfered, mirror-polished heads               
  tourbillon: mirror-polished carriage plate, satin-finished pallet bridge, mirror-polished stud-holder, rhodium-finished balance, polished and rounded-off carriage bridge
  constant force bridge: 18-carat yellow gold (3N), polished bevel, satin-finished flat surface, polished angles 
  constant force carriage lower bridge: flame-blued, mirror-polished, polished angles                 
  

Engraved plate

• "To the revered memory of John Arnold and Abraham-Louis Breguet. Friends in their time, legendary watchmakers always."

Dial

• 18-carat yellow gold (3N), hand-engraved, Arnold & Son “fern” pattern

Hour dial

• white opal, concave

Case

• Material: platinum (Pt 950)
  
• Diameter: 41.50 mm
  
• Depth: 13.70 mm
• Crystal: Domed sapphire with an anti-reflective coating on both sides
  
• Back: Sapphire crystal, anti-reflective coating on both sides
  
• Water-resistance: 30 metres / 3 ATM
  

Strap

• Material: midnight blue alligator leather with black alligator leather lining, hand-stitched
  
• Clasp: folding, platinum (Pt 950)

Reference                           

• 1FCBX.Z01A.C0232X

Limited edition                    

• 11 pieces    

Astronomy, Chronometry and World Time

Arnold & Son's three founding principles

Throughout human history, measuring time has always referred to the stars. It was by observing certain stars and understanding their cycle that the first calendars were established with impressive accuracy. It took several millennia before this precision was enclosed in a timepiece like the ones designed by John Arnold. 

The golden age of maritime explorations and discoveries ushered this precision into a new technical ideal – determining longitude at sea. Its immediate corollary was the identification of local time, which changed constantly as the observer moved along an east-west axis. Astronomy, chronometry and what we now call world time are thus inextricably linked within one and the same question, to which John Arnold and his son devoted their lives, their art and their genius. 

This is how these three dimensions – astronomy, chronometry and world time – have come to be embodied in the House's contemporary timepieces.  Echoes of John Arnold's inventions and preoccupations, these pillars represent the foundations on which the Arnold & Son collections are based.

Chronometry: Be accurate

Rate accuracy, which is known as chronometry, is the key requirement of Arnold & Son's contemporary watchmaking. It is the standard of excellence for its collections, the first condition to be met and constantly checked, whether it is at the forefront or in the background of a watch designed by Arnold & Son. It is the most discreet of a movement's characteristics. 

When building an Arnold & Son collection, all the thinking is focused on this chronometry. The manufacture calibres are based on advanced technical fundamentals that are not necessarily the best known. One of them is the choice of small, lightweight balances capable of rapidly returning to their isochronous rate after the latter has been disturbed by inevitable everyday shocks. Another is the routine use of large barrels or even two series-coupled barrels to store the energy required for the movement to function.  They consequently provide Arnold & Son's manual winding calibres with above-average power reserves of 90 hours and more. A third is the particular attention paid to manufacturing the gear trains, roller-burnishing the pinions and polishing the gear teeth, as well as the precision of the machining and therefore the relative positions of the moving parts, a key concept in rate accuracy.

The tourbillon (or the fact of putting the regulating organ in rotation on its axis to best adjust the effects of gravity on the balance and its hairspring) was patented after John Arnold's death, but it was undoubtedly at the heart of his chronometric research and discussions with his friend Abraham-Louis Breguet, who incidentally assembled his first tourbillon on a John Arnold pocket watch in homage to this great watchmaker. Nowadays, the tourbillon has become a must in Arnold & Son collections.

While the tourbillon was not a complication in John Arnold's time, constant force underpinned the design of his marine chronometers. The regularity of the rate of the sprung balance relies on the consistency of the energy that it receives. However, this naturally fluctuates due to the circular and spiral nature of the mainspring contained in the barrel. To achieve a perfectly smooth torque, in other words a constant force, Arnold & Son uses a one-second constant-force mechanism. Housed just before the escapement, it stores up a small but always equal amount of energy in a secondary spring, the remontoire. Thus, every second, the sprung balance receives very precisely the same force to power its oscillations. These become more even, thereby creating the conditions for a high-precision rate.

Arnold & Son also works with another of John Arnold's historical chronometry indicators: deadbeat seconds, a mechanism that was indispensable to navigators at the time for calculating longitude. This mechanism advances one step each second, rather than six or eight smaller jumps in sync with the frequency of the balance. Instead of the term deadbeat seconds, Arnold & Son prefers a name whose very sound means accuracy: “true beat second”. Its jump is a signature of John Arnold's marine chronometers and a complication that is still alive and well in the House's collections.

Astronomy: Under the sky

The Pole Star, Southern Cross, astrolabes and sextant: measuring time has relied on the recurrence of astronomical phenomena in order to find long, reliable points of reference there that can be used under any conditions. The fruit of the human ingenuity, patience and dedication of countless observers and astronomers from every culture, these markers of cyclical time are foundational for Arnold & Son watchmaking.

Astronomical complications are a signature of Arnold & Son collections, with the moon as the heavenly body of choice, main subject and major inspiration. The distinctive feature of the Brand's moon phase timepieces is that they feature “astronomical” display precision as a matter of course. This term corresponds to an accumulated one-day deviation in the moon phase display every 122 years. Since setting this complication requires great finesse, the Arnold & Son moons generally have a double display with a secondary indicator on the case back next to the movement. This extremely rare display bears witness to Arnold & Son's involvement in all types of development and reflects its favoured themes, which are as much chronometric as astronomical.

Over and above their precision, Arnold & Son's moon phases attract all the light, either with a large moon opening up over half the dial, or with a 12-mm three-dimensional rotating moon, making it the largest of all moons. Whether in two or three dimensions, the moon is always treated as a small work of artistic craftsmanship, composed of materials that are rare in watchmaking such as marble or Paraíba tourmaline, or delicate such as mother-of-pearl, meteorite or aventurine glass. The Arnold & Son moon also shines at night, often with a subtle addition of luminescent material. 

World Time: Here, elsewhere, everywhere

With ocean navigation, humankind divided up the world and invented longitudes, which were calculated by comparing the local time, observed using the sun, and the time at a starting point, kept by an extremely reliable timepiece. John Arnold was one of the leading suppliers of chronometers to the British Navy. He was the one who successfully improved the reliability and simplified the production of these indispensable marine chronometers, so much so that he became a benchmark among great explorers such as James Cook and later Dr David Livingstone. The indication of several time zones is therefore integral to Arnold & Son's watchmaking identity.

As this navigation was itself inseparable from cartography, for this world time complication Arnold & Son has chosen to depict a three-dimensional terrestrial hemisphere, making it possible to tell what time it is at any point.

In parallel to this graphic vision, Arnold & Son has developed a second approach to the time elsewhere in the world: with a double tourbillon featuring two distinct rotating regulating organs, making it possible to follow time zones offset by 15, 30 or 45 minutes compared to a full hour – a freedom in terms of setting that remains extremely rare. 

Once again, and because this double display is based on a profoundly chronometric complication, Arnold & Son’s fundamental principles are interwoven. One never advances alone; there are always two – if not three – together. This is how a pillar's strength is measured: it relies on the next one, creating the conditions for a solidity that stands the test of time.