COMPLICATION Greubel Forsey Quadruple Differential Tourbillon
the next generation of tourbillons and how they work by wei koh
ENTER THE SUPER TOURBILLONS
motion or revolution, and its counterpart the circle, form the basis for a vast amount of symbols in human culture. It is the primary motion in most forms of dance, it is the emblem for the cycle of the seasons, it is at the core of most martial arts and it depicts the way in which our solar system enters into a self-sustaining symbiosis between the planets and the stars. It is also the basis on which we depict time through two hands that revolve around the perimeter of a dial. Perhaps this explains why we find the tourbillon so compelling, because with its eternal turning cage, it is horological symbolism reduced to its most poetic embodiment of time’s perpetual progression. In the last issue of REVOLUTIHN we charted how the tourbillon has become less of a chronometric device and more a means for artistic expression. One theme that has emerged from this age of tourbillon related artistic alchemy is that of the orbital tourbillon – a tourbillon (or in the case of Ulysse Nardin’s Freak, a balance wheel) that rotates not just around its own center but that simultaneously orbits around the central axis of the watch. In Breguet’s Double Tourbillon – which boasts two separate tourbillons that are connected by a differential mechanism that averages out their errors – the regulators are connected to the dial via a bridge which also serves as the watch’s hour hand. The dial, bridges and tourbillons can be thought of as one fixed element geared to complete one revolution every 12 hours. While this is too slow for the naked eye to actually discern the progression of the tourbillons, there is something enthralling about looking at your watch to see that the tourbillons have shifted place as surely as the canopy of stars in the night sky shifts position. Piaget’s Polo Tourbillon Relatif also uses one of its central structural elements to give a reading of the time. From what we understand, the initial concept for this watch came from Carole ForestierKasapi, the head of Cartier’s high watchmaking movements. It comes as no surprise that
Jean Dunand’s Tourbillon Orbital
The result is a tourbillon that appears to transmigrate around the circumference of the dial, orbiting around the central watch hands once every hour
DEFYING THE BOUNDS OF GRAVITY - MULTIPLE AXIS TOURBILLONS
Because the tourbillon was created to compensate for errors caused by gravity when pocket watches were in the vertical position, such as when tucked into waistcoats, a debate has raged as to the chronometric value of placing a tourbillon in wristwatches that often remain in the horizontal
AROUND THE WORLD – THE ORBITAL TOURBILLONS The circular
Forestier-Kasapi was also the individual behind the initial concept for Ulysse Nardin’s Freak, the first watch to use its own rotating movement as time telling indicators. Although more information about the Piaget Polo Tourbillon Relatif has been difficult to find, this is what we can see from studying the watch: it appears that the disc that bears the watch’s hour indicator also serves to cover the watch’s center wheel. This wheel transmits power to the going train which is hidden behind the plate bearing Piaget’s signature carousel-type Emperador tourbillon. The going train beneath the plate engages the central pinion of the tourbillon cage which causes the escape wheel’s pinion to rotate around a fixed fourth wheel that is clearly visible if you look closely. This pinion turns the escape wheel which gives power to the lever which gives impulse to the balance wheel. This entire bridge and tourbillon assembly is geared to complete one revolution per hour and serves as the watch’s minute hand. While the transmission of power to the tourbillon in Piaget’s Polo Tourbillon Relatif takes a fairly conventional approach, the transmission of power that simultaneously causes the balance to pulse and also causes the escape bridge to rotate once per hour is highly unconventional in Ulysse Nardin’s masterful Freak. In the Freak, power flows from the central pinion to the escape bridge (minute hand) which is rigidly fixed on the central pinion. When the pinion turns, the escape bridge has to turn. As this happens, the first wheel which is geared in the upper fixed track “recuperates” or gathers energy from the fixed track, just as the tires of a car “recuperate” the energy from the fixed road, and conveys this energy across the escape bridge towards the escape wheels. Finally, energy is sent from the escape wheels towards the oscillating balance passing through the alternator. For the combination of technical innovation, coupled with poetic expression and refined haut de gamme execution, it’s hard to beat Jean Dunand’s Tourbillon Orbital. The movement comprises a flying tourbillon regulator and a watch barrel set opposite each other and fixed between two plates. These two plates then rotate on their own central axis, completing one revolution every hour. The result is a tourbillon that appears to transmigrate around the circumference of the dial, orbiting around the central watch hands once every hour.
Ulysse Nardin’s Freak 28’800 V/h
Piaget Polo Tourbillon Relatif
atchmaking in the new millennium has seen an explosive advancement in tourbillon design. Tourbillons are now exploiting the third dimension with multiple axis cages, combating gravity with fast rotating cages, “averaging out the averages” with twin tourbillons connected via differential mechanisms and opening up their inner workings for our pleasure through the use of glass plates and bridges. Collectively, we call this new evolution of the whirlwind the era of the Super Tourbillons! Here are some of the most significant….
Franck Muller Tourbillon Revolution 2
of power constant. Watchmaker and REVOLUTIHN contributing editor Curtis Thomson explains, “Prescher realized just as Goode did, that constant force mechanisms are required to achieve a suitable result.” Thomson also points out that Prescher’s efforts were borne from the desire to create visually spectacular timepieces, with no claims of timekeeping advantage. Similarly, Franck Muller has not issued claims related to the chronometric performance of their Revolution 2 and 3 (double and triple axis tourbillons respectively), preferring to let the sheer artistry of the detailed universe inhabited by the constantly twisting lithe gold balance wheels ensnare you with its visual riches. MULTITUDES – THE DOUBLE TOURBILLONS The logic behind using
two regulating organisms connected by a differential in a wristwatch is such: if you can adjust the two balances so that one runs slightly faster and one slightly slower, you can further average out the error in their rates, resulting in a more accurate wristwatch. However, movement designer Takahiro Hamaguchi of Audemars Piguet Renaud & Papi also points out, “But if you adjust both your balances either too fast or too slow you will increase the inaccuracy of your watch.” The first modern wristwatch to use two balance wheels and a differential Jaeger-LeCoultre’s Gyrotourbillon
is Philippe Dufour’s Duality. Dufour came across an image in a book depicting a movement using two balances. Inspired, he set about creating a watch movement that similarly used two balances. The secret to averaging out the errors between these two balances is the mechanism known as a differential. Cars similarly have differentials which average out power delivery to the two wheels. In the last few years several avant-garde manufactures have unveiled watches featuring two tourbillon regulators that are linked using a differential mechanism. The theory behind this is that while tourbillons average out the deviations of the balance wheels resulting from positional errors, the differential mechanism further averages out the averages of these two tourbillons. While this may seem like something of a tongue twister, the rationale behind it is sound enough, provided the two tourbillon regulators are well regulated such that one is running slightly faster and one is running slightly slower. Where this becomes difficult, is as we’ve seen in our article, ‘How a Tourbillon Works’: simply poising a single tourbillon such that both the balance wheel and cage function well is difficult enough. Now add to this the challenge of adjusting two tourbillons so that not only are they well poised but they run at just slightly different rates in diametrically opposed directions and you’ve got a rather massive fine-
Thomas Prescher erupted onto the scene as the first watchmaker to make a double axis flying tourbillon in a pocket watch, followed by double and triple axis flying tourbillons in wristwatches
Greubel Forsey Double Tourbillon 30 Degrees
position such as when left on a desk. With this in mind, a group of ingenious young horologists began to think about how to alter the basic construct of the tourbillon to endow it with greater relevance as a wristwatch. Independently, watchmakers Eric Coudray of Jaeger-LeCoultre, Stephen Forsey, Robert Greubel and Thomas Prescher designed multiple axis tourbillons, where the balance rotated in not just one, but two (and yes, even three) planes to adopt a far greater number of positions in space. The theory is sound: as the balance travels through its ethereal, three dimensional dance, it will average out positional errors in both the vertical and horizontal planes, resulting in a tourbillon with real wristwatch application. The idea of multi-axis tourbillons emerged in the ’70s when two British watchmakers Anthony Randall and Richard Goode created experimental timepieces featuring them. In both Goode and Randall’s tourbillons, axes were constructed at 90 degrees to one another. In an immobile clock, this placed the balance back at the vertical position, but in a wristwatch, the placement of the two axes at 90 degrees to each other created two problems. The first was that it necessitated a very tall movement to incorporate a tourbillon cage fixed on a vertical plane. Says Stephen Forsey, “To make a tourbillon with two 90 degree axes in a wristwatch would result in something that was unfeasibly thick.” The second problem was that because wristwatches spend much of their life leaned over on their side (particularly if you have a deployant buckle) this would place the balance back at the undesirable horizontal plane for long periods of time. The solution adopted by Eric Coudray, inventor of Jaeger-LeCoultre’s Gyrotourbillon, as well as Greubel Forsey in the Double Tourbillon 30 Degrees was to alter the angle of their tourbillons’ axes so that the balances spent the least amount of time as possible in the horizontal position. This also allowed the construction of a mechanism that was significantly thinner and thus more suitable for a wristwatch. Amazingly, the Gyrotourbillon adds to the double axis tourbillon mechanism a running equation of time indicator. Because the movement now has to power not one but two cages, efforts were made to minimize their weight in the Gyrotourbillon. The external cage was machined from aerospace aluminum while the inner cage is made from aluminum and titanium. The outer cage makes a full revolution every minute, while the inner cage supporting the balance wheel, escapement and spiral literally hurtles through space completing a full rotation every 24 seconds. Coudray also canted the Gyrotourbillon’s cage at 37 degrees to create a flatter watch and to maximize visibility of the balance wheel. The Gyrotourbillon and the birth of the Multiple Axis Tourbillon Era served to further widen the divide related to the tourbillon and claims to its functionalism. Only Jaeger-LeCoultre and Greubel Forsey took the courageous step to offer real empirical proof that their multiple axis tourbillons provide higher chronometric results than single axis tourbillons or well regulated standard wristwatches. Stephen Forsey explains, “We used a very scientific approach to test the effectiveness of our Double Tourbillon 30 Degrees. We took the one minute, three armed tourbillon cage and we fixed that in a movement so that it worked as if it was a simple manual wind watch. We tested this in six positions. The biggest difference in timing accuracy was 10 seconds (of error in a day). Then we took the same three armed cage and made it turn as if it was a classical one minute (single axis) tourbillon. We tested this watch in six positions and we had a result of seven seconds’ error. Then we took this same cage and placed it within our Double Tourbillon 30 Degrees and again subjected it to testing in six positions and this gave us results of three to 3½ seconds.” While Greubel Forsey and Jaeger-LeCoultre’s goal was to improve chronometric functionalism, Franck Muller and Thomas Prescher took a different route, embracing the three dimensional artistic expressionism innate to the multiple axis whirlwinds. AHCI member Thomas Prescher erupted onto the scene as the first watchmaker to make a double axis flying tourbillon in a pocket watch, followed by double and triple axis flying tourbillons in wristwatches! Prescher discovered that with a mechanism as heavy as his multi-axis tourbillon, he needed a way to keep the delivery
COMPLICATION regulating proposition on your hands. As such, it is perhaps best to regard double tourbillons such as Roger Dubuis’s beautiful Excalibur EX01 movement with twin flying tourbillons, or deLaCour’s Bitourbillon created by Christophe Claret, as brilliantly creative works of art rather than super chronometers. In contrast, Stephen Forsey has stated that the intention behind Greubel Forsey’s Quadruple Differential Tourbillon which boasts a pair of double tourbillons, both with balance wheels inclined at 30 degrees and linked via a spherical differential, is to achieve better accuracy than that displayed by the brand’s already highly chronometric dual axis tourbillon. MECHANICAL MASTERY – THE SPLIT SECOND CHRONOGRAPH TOURBILLONS In the realm of high complications, no one timepiece
Here is a watch that not only defeats gravity’s insidious clutches but also offers the ability to capture elapsed times in interval format Richard Mille RM 008
Roger Dubuis’s beautiful Excalibur EX01 movement with twin flying tourbillons
deLaCour’s Bitourbillon created by Christophe Claret
boasts a more intimidating performance arsenal than a tourbillon with a split second chronograph. Here is a watch that not only defeats gravity’s insidious clutches but also offers the ability to capture elapsed times in interval format. But the challenges in rendering a split second chronograph tourbillon are vast, and as with most things in watchmaking, have a great deal to do with generating adequate power. As we’ve established, it takes a fair amount of power to drive a tourbillon cage. Now add to this tourbillon a chronograph mechanism which in its traditional laterally-coupled form is driven either by a wheel that is co-axially linked to the third wheel that is already powering the tourbillon cage or off a toothed wheel fixed to the tourbillon cage and you can begin to see the amount of additional power needed to ensure there is no substantial drop in amplitude when you switch the chronograph on. The two additional gear wheels fixed to the chronograph’s coupling arm as well as the central chronograph wheel all need to be turned by the same spring powering the tourbillon. Moreover, in the case of a split second chronograph, there is the additional resistance to be factored, caused by the return lever roller jewel having to overcome the profile of the split second heart shaped reset cam whenever the split second mechanism is employed. Now add to this already heady bag of problems the fact that power quality rapidly diminishes as a watch’s power supply wanes and you’ll understand the supreme logic behind A. Lange & Söhne’s use of their signature torqueregulating chain and fusée mechanism in their split
COMPLICATION second chronograph tourbillon, the Tourbograph. The chain and fusée (as detailed by Anthony de Haas in our article ‘Technical Top Guns’) compensates for the loss of torque as a mainspring unwinds. As opposed to this highly traditional solution demonstrated by A. Lange & Söhne, Richard Mille’s RM 008 split second chronograph tourbillon utilizes all-new teeth profile of the gear wheels to ensure that minimum power is lost to friction. Further, the watch actually displays the quality of power generated by the mainspring so that you know when to use the split second chronograph and when to rewind the watch. In addition, Giulio Papi, the designer of Mille’s movements, has developed a new ratcheting split second mechanism specifically to eradicate the loss of amplitude demonstrated by traditional split second chronographs. This new mechanism should be released by the end of 2007.
Parmigiani Fleurier presented the Forma XL Tourbillon in 2004, with the goal being to enhance the regularity of the tourbillon by doubling the speed of rotation of the tourbillon cage
THE SPEED DEMONS – THE SUPER FAST TOURBILLONS The
power reserve. Yet look at 12 o’clock on the dial of Parmigiani’s tourbillon and you’ll see an indication for the watch’s full eight days power reserve – a feat truly worthy of resounding applause. When asked how he coaxed such an immense power reserve from his twin barrels to power his fast moving tourbillon cage, Parmigiani smiled stating, “This was not easy. One of the major things we had to overcome was the loss of power as a result of friction in the going train. We spent a lot of time optimizing tooth profiles of gear wheels to eliminate the wastage of power. This is the only way we could have such a long power reserve while accelerating our cage to this speed.” While conventional wisdom dictates that a tourbillon that averages out errors twice as often as a traditional tourbillon could provide better timekeeping results, Zenith’s every flamboyant CEO Thierry Nataf offers another take on speed and its application to building a better tourbillon. Zenith’s El Primero chronograph movement is the world’s fastest beating caliber. Nataf’s first stroke of genius upon taking the helm of the brand was to offer consumers a direct view of the blazingly fast balance by creating a massive aperture in his dials through which the hypnotic speed of the oscillations in tandem with locking, unlocking and impulse of the
Patek Philippe’s 10 Days Tourbillon
escapement could be on constant display. Now take this same balance and place it in the rotating theater of a beautifully realized carousel tourbillon with two armed cage and you have one of the most visually enchanting tourbillons in the world. Do we feel that the speed of Zenith’s balance wheel makes for a more accurate tourbillon? Only so much as a faster beating balance generally creates a more accurate wristwatch in general (the size of the balance remaining constant). But on a purely emotional level, to behold the light speed oscillations that ignite the inner world of every Zenith tourbillon is indeed a thrilling experience. ENDURANCE: THE LONG POWER RESERVE TOURBILLONS
We’ve established that it takes more energy to power a tourbillon cage than to power a traditional watch balance. As such, logic would dictate that most tourbillons would possess very short power reserves. But several manufactures have created tourbillons with life spans ranging from an impressive eight days to a truly startling 22 days of power reserve. That Chopard L.U.C and Patek Philippe also have their tourbillons COSCcertified as chronometers clearly underlines their belief not only in the
Greubel Forsey’s Tourbillon 24 Secondes Incliné
To behold the light speed microorganism that presides within every Zenith tourbillon is indeed a thrilling experience
great Chinese military strategist Sun Tze espoused speed as an essential component to victory, but is speed also the key to dominion over gravity? This was a thought undoubtedly on the mind of Michel Parmigiani and Greubel Forsey when they unveiled tourbillons with cages that revolved at far greater velocities than the traditional one-minute rotational pace. In the instance of Greubel Forsey’s Tourbillon 24 Secondes Incliné – a tourbillon with a cage that rotates once every 24 seconds – the intention was to improve timekeeping accuracy. However, the reasons why this tourbillon boasts good results have been misunderstood in the past. Says Stephen Forsey, “It would be incorrect to think that by making the cage rotate faster it would endow the tourbillon with some degree of autonomy from gravity. In order for that to theoretically happen, the cage would have to be accelerated far beyond what we are capable of today. Instead, the essence to why it functions better is that the balance wheel adopts all different positions twice as often, which leads to a more frequent averaging of errors.” Parmigiani Fleurier presented the Forma XL Tourbillon in 2004, with the goal being to enhance the regularity of the tourbillon by doubling the speed of rotation of the tourbillon cage. However the ever frank Michel Parmigiani states, “Why double the rotational speed of the cage? Primarily because it looks visually dynamic. Tourbillons definitely create better accuracy in pocket watches. But I would hesitate to say that they create much better accuracy in wristwatches. For me they are an expression of great watchmaking skill and artistry.” The typically modest Parmigiani does not mention that his tourbillon is hugely impressive for yet another reason. As explained in our story ‘How a Tourbillon Works,’ it takes a fair bit of power to drive the tourbillon mechanism which is why cages are crafted to be as light as possible. But a cage that rotates at double the speed of a traditional tourbillon needs even more power to accelerate to this blistering pace. As such, logic would dictate that Parmigiani’s watch would have a very low
Chopard L.U.C Quattro Tourbillon
FULL FORCE – THE CONSTANT FORCE TOURBILLONS The brilliant watchmaker F.P. Journe is fond of saying that putting a tourbillon in a wristwatch in pursuit of accuracy is a lot like intentionally breaking your leg before a foot race. Here’s why: power is contained inside the watch’s barrel.
Ulysse Nardin and Corum utilize glass movements to create emotionally evocative tourbillon wristwatches characterized by their transparency
De Witt created an all-new type of constant force mechanism for his Tourbillon Force Constante Academia
Caged within is the mainspring. When you wind your watch the barrel turns and the spring coils more densely towards its center. The more you wind it, the tighter the watch coils until it reaches the limit of its spring tension. At its tightest, the barrel provides optimal power. But as it lessens in spring tension, power weakens. Power is transmitted by the barrel to the gear train, which in turn sends power to the escape wheel, which transmits power to the watch’s regulating organ – the balance. But in a tourbillon, this same mainspring must drive a much heavier mechanism which consists of a massive cage as well as a balance. Consequently, differences in the strength of the mainspring’s torque are further weakened by the weight of the tourbillon mechanism. It is for this reason that A. Lange & Söhne rationalized the use of a chain and fusée mechanism in their Pour le Mérite tourbillon to ensure constant delivery of torque to the going train. Conversely a constant force mechanism regulates the quality of power to a balance wheel by giving an additional impulse to the regulator somewhere in between the fourth wheel and the balance. The distinction of creating the first constant force mechanism for a tourbillon as chronicled in Jack Forster’s article ‘In the Footsteps of Breguet’ belongs to F.P. Journe. In 2006 Jérôme de Witt, the founder of DeWitt watches, created in collaboration with movement maker BNB an all-new type of constant force mechanism for his Tourbillon Force Constante Academia. Says Jérôme de Witt, “The mechanism is actually based on a flying regulator like you find in a grande sonnerie.” This constant force device absorbs energy from the barrel once every second and redistributes it every 10 seconds to the tourbillon. You can watch this redistribution of power in action as the elegant inertia weight, which is shaped like a cross, completes six revolutions per minute.
BEAUTY STRIPPED BARE – THE TRANSPARENT TOURBILLONS
So we’ve established that the tourbillon is the most visually engaging of all horological devices. How do you make a tourbillon even more beautiful? You strip it bare to reveal its inner world to its owner. Both Corum with its Tourbillon Saphir and Ulysse Nardin’s Royal Blue Tourbillon utilize glass movements to create emotionally evocative tourbillon wristwatches characterized by their transparency. Within the vibrant geometry of these timepieces the traditional architecture of the movement has been reinvented, creating a weightless vision of time telling poetry. In Corum’s Tourbillon Saphir, metal is banished from the inner volume of the watch where all plates and bridges are made in blue sapphire crystal. The watch’s flying tourbillon appears to float in space, disconnected from any of the watch’s gear train. Similarly the Royal Blue’s sapphire transparency unveils the appealing logic of the movement’s design. Look closely and you can see how the barrel of the watch connects to the tourbillon escapement with the bare minimum of gear wheels. The watch’s crown seems disconnected completely from the barrel. Yet as you turn the crown, the barrel also magically turns to charge its mainspring, thanks to a wheel recessed into the bezel. Inlaid in the inner dial flange is a rhythmic pattern of perfectly matched diamonds juxtaposed by the intense blue light of 12 sapphires placed to act as hour indices. Observe the tourbillon in flight and watch the dexterity of the gearwheels functioning in perfect synchronicity beneath their blue sapphire bridges and you perfectly understand Ulysse Nardin owner, Rolf Schnyder’s simple motivation behind its creation. As he puts it, “Because it’s beautiful,” which in the end may be the best reason for anyone to create a tourbillon. H Corum’s Tourbillon Saphir
Bovet 22-Day Tourbillon
quantity of their power reserve but also in its quality. Patek Philippe is one of the few modern manufactures that eschew the fashion for placing tourbillons on the dial side of their watches. While the brand’s owner Philippe Stern tell us, “This is because we don’t want oils in the tourbillon to dry up when exposed to direct sunlight,” another reading of this is simply as a statement of Patek Philippe’s immense understated appeal, combined with a respect for the historic roots of the tourbillon mechanism, which was always placed on the movement side of a watch in Breguet’s halcyon days. What is impressive about Patek Philippe’s 10 Days Tourbillon is that it is not only certified to COSC standards as a chronometer but actually passes even stricter internal testing. The challenges in creating such an accurate tourbillon are vast. Says the manufacture’s technical director JeanPierre Musy, “ For the cage to not influence the amplitude of a watch too considerably, it must have minimum weight. To make it light, it must be made as thin and delicate as possible. But even if the case is extremely light, it still takes a lot of energy. So as a result the balance has to be made relatively small. If the balance is too small you don’t have a stable watch… but for Mr. Stern our tourbillons had to defer to the roots of Breguet’s complication and be chronometric.” Now combine the fact that Patek Philippe’s 10 Days Tourbillon is not only highly accurate but also boasts an immense power reserve and you understand how it is an extraordinary feat of technical virtuosity. Not to be outdone, in 2003 Chopard L.U.C unveiled the Quattro Tourbillon which met all COSC standards as a chronometer, underscoring Chopard co-president Karl-Friedrich Scheufele’s insistence that his tourbillons be functional as well as alluring. Just as impressive was this watch’s massive eight days power reserve generated from a then recordsetting four spring barrels. While Chopard uses two sets of stacked and coupled barrels to achieve extraordinary endurance, Bovet achieves the groundbreaking 22 days power reserve for its latest tourbillon by combining two huge barrels. The impressive feat in design architecture is in the fact that the resulting timepiece is not particularly thick and highly wearable. Says Bovet’s Pascal Raffy, “For me a watch, even our 22 days tourbillon, is to be worn, it must be horological and not a gadget or gimmick.” Raffy’s focus was on creating a coherent, beautiful and wearable watch rather than a “talking piece.” Adding credibility to this whirlwind’s pragmatic persona is the retrograde date indicator that arcs resplendently across the upper half of the fathomless black enamel dial, as well the 24-hour format second time zone display found at 6 o’clock. When it comes to horological masterworks, few timepieces compare with Daniel Roth’s in-house Tourbillon 8-Day Power Reserve. When creating this timepiece Daniel Roth’s technicians used one of the manufacture’s striking watches as a starting point. Where the second barrel of the watch was initially used to power the strike train, with the latter removed the barrel could be coupled with the first barrel and together the movement yielded an impressive eight days of power reserve. During testing the torque created by these two barrels was so strong that it actually caused gear teeth to break, so Daniel Roth reconfigured the going train to correct this. The existence of high torque in this movement is considered a good trait as it generally leads to high accuracy, particularly when accelerating a heavy organism like a tourbillon. The 2006 version of this iconic timepiece has been subtly modified to incorporate a gracefully curvilinear dial with raised three dimensional indices. As with the majority of Daniel Roth timepieces, this tourbillon is characterized by the three armed propeller-shaped seconds indicator which is fixed to the tourbillon cage, to be read off a three-tiered seconds track.
Daniel Roth’s in-house Tourbillon 8-Day Power Reserve