Ultrathin Tourbillon Skeleton Red Gold

Ultrathin Tourbillon Skeleton Red Gold

The finesse of curves 

With its graceful curves and wide apertures, Ultrathin Tourbillon Skeleton also stands out for its slimness. Its new case, with a diameter of 41.5 mm and a thickness of 8.4 mm, presents the flying tourbillon calibre in its purest expression. The Ultrathin Tourbillon Skeleton collection, adorned in red gold or platinum, is issued in two limited series featuring 28 watches apiece.

Arnold & Son continues its tour of the Ultrathin Tourbillon collection. The A&S8320 calibre unveils its curves, apertures and details within a 41.5 mm case in either red gold (5N) or platinum (PT 950), each released in a run of 28 timepieces. Encased in this precious housing, Arnold & Son’s flying tourbillon stands out for its finesse and precision.

Finesse, because at just 3.3 mm thick, it is one of the slimmest skeleton tourbillon calibres in existence. Precision, because this one-minute flying tourbillon is assembled with a variable-inertia balance for enhanced calibration stability.

Radiating originality

The purpose of a skeleton is to convey a message, be it geometric, generic or minimal. For Ultrathin Tourbillon Skeleton, the skeletonisation of the calibre reveals pronounced curves and numerous inflection points that are highlighted by an original finish. On both the Ultrathin Tourbillon Skeleton Red Gold and Platinum, the bridges are treated with rose-gold PVD (4N) after being decorated with radiating Côtes de Genève stripes.

The flange around the calibre adopts this same finish, clearly revealing the Arnold & Son signature at 6 o’clock and enabling the off-centred white opal dial to be displayed in its purest form.

Golden carriage

At the heart of Ultrathin Tourbillon Skeleton beats the A&S8320 calibre, whose architecture and slimness are its principal protagonists. Designed without an upper bridge to minimise its thickness, the calibre is classed as a flying tourbillon.

The variable-inertia balance with inertia blocks ensures more precise calibration over time. The slender triangular carriage is supported by a double arrow, which is actually a counterpoise. The arrowhead on the staff of the escape wheel serves as a seconds pointer, as the carriage completes one rotation per minute.

Performance reserve

The changes to the tourbillon carriage and regulating organ give the A&S8320 calibre a power reserve of 100 hours. While this is a larger power reserve than for standard tourbillons, particularly slim ones, it is entirely in line with the performance regularly achieved by Arnold & Son calibres.

Technical specifications

Functions

• Hours, minutes

Movement

• Calibre: A&S8320, 1-minute flying tourbillon, manual winding
• Jewels: 29
• Diameter: 32.00 mm
• Thickness: 3.30 mm
• Power reserve: 100 hours
• Frequency: 3 Hz / 21,600 vph
• Finishes                  
• mainplate: skeletonised, rose-gold PVD treatment (4N), Côtes de Genève stripes radiating from the centre
  
• bridges: skeletonised, rose-gold PVD treatment (4N), polished and chamfered by hand, Côtes de Genève stripes radiating from the centre
  
• wheels: circular satin-finished
  
• screws: blued and chamfered, mirror-polished heads
  
• tourbillon carriage: ‘Arnold & Son’ signature, polished, satin-finished and chamfered by hand    

Dial

• white opal

Case

• Material: 18-carat (5N) red gold 
• Diameter: 41.50 mm
• Thickness: 8.40 mm (with crystal)
• Crystal: domed sapphire with an anti-reflective coating on both sides
• Case back: sapphire crystal with an anti-reflective coating
• Water-resistance: 3 bar (30 metres/100 feet)

Strap

• Material: blue alligator leather, black alligator leather lining, hand-stitched
• Clasp: folding clasp in titanium with cover in 18-carat (5N) red gold 

References

•  red gold: 1UTBR.Z01A.C246R

Limited edition      

• red gold: 28 timepieces

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.