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power reserve

power reserve

THE POWER OF ENDURANCE: THE LANGE 31 A. Lange & Söhne unveils the watch you wind only 12 times a year BY WEI KOH


A. Lange & Söhne CEO, Fabien Krone

hat you’re looking at is a revelation, particularly if you think about it like this… Each year is a 365-day period that stretches before us with a certain temporal gravitas. It is a period where inchoate actions can become resolute and when ambitions can become realities. It is a period where four distinct seasons run their course and provide a temporal staging room for people to fall in love and get married. During this period, your watch acts as a companion. But while you need to wind most manual watches daily, with the Lange 31, you need only to wind your watch all of 12 times in a whole year. That’s because the Lange 31 boasts the longest power reserve of any watch in the world. While the American-based jeweler Jacob & Co. introduced a prototype of a timepiece that could theoretically achieve this power reserve last year, its fuel source was seven vertically-placed barrels, resulting in an all but unwearable timepiece. As we’ve yet to hear of or see any watches delivered, we assert our prerogative to distinguish between legitimate horological acts and lesser ones. In contrast to the Jacob, the Lange 31 embodies legitimate horology. It is crafted by a company whose single impetus is to use the language of its watchmakers’ skilled hands to write new chapters in modern watchmaking, giving full respect to the enduring fabric of its past. Accordingly, the Lange 31 is a useful, functional timepiece and, in spite of its large 46-mm case diameter and 15.9-mm height, it is eminently wearable. From its exterior, the Lange 31 brings the manufacture’s traditional sobriety to a near ascetic exercise of Zen minimalism. The platinumcased watch with a silver dial boasts four indications: the signature Lange grande date mechanism located at ten o’ clock on the watch dial that is


activated by the pusher beside it, the central civil time hands, a small seconds indicator at six o’clock, and at three o’clock is a power reserve indicator that brings self-effacing understatement and gentlemanly discretion to an all-new extreme. Only the small numeral “31” at the upper end of its scale hints at the massive store of power caged within. Says A. Lange & Söhne’s CEO, Fabien Krone, “The mainsprings of this watch are so powerful that, together, they can lift a 100-gram bar of chocolate a full ten feet in the air.” As expressed by Sam Raimi’s Spiderman movies, power without control is destructive. Winds sweep across plains in America’s mid-west, uprooting trees, homes and cars. Conversely, channeled in the right direction as with a hydroelectric dam,




The mainsprings of this watch are so powerful that, together, they can lift a 100-gram bar of chocolate a full ten feet in the air A. Lange & Söhne CEO, Fabien Krone

power reserve



At 1,850mm, Each of the two mainsprings in the Lange 31 is five to ten times longer than any conventional watch mainspring



Here it is, in full technical detail: the inner workings of A. Lange and Söhne’s Remontoir BY WEI KOH

hat you need to know is that a remontoir isolates the watch’s oscillator from the mainspring. What drives the oscillator here is a special constant force hairspring that is fixed to the seconds wheel. The seconds wheel drives the escape wheel, which sends pulses of energy to the anchor. The anchor, in turn, sends this energy to the oscillator. This much is fairly clear, but how does the hairspring on the seconds wheel get rewound every ten seconds? The answer is pretty simple actually. What happens is that one side of the hairspring is fixed to the seconds wheel, and the other side is fixed to another seconds wheel (lower seconds wheel) that lies directly beneath the first seconds wheel (top seconds wheel). The lower seconds wheel is powered by the mainspring, but because it doesn’t engage the escapement, it is regulated only by a special one-toothed intermediate wheel. This intermediate wheel is locked into place. Every ten seconds, this intermediate wheel is released and allows the lower seconds wheel to revolve just enough to charge the remontoir hairspring with enough energy to drive the top seconds wheel for ten seconds. Once this energy is depleted, the intermediate wheel is released again to recharge the hairspring, and so on.


1) Energy flows from the two huge stacked barrels to the gear train, and then from the gear train to the lower seconds wheel. 2) This wheel is in contact with the pinion of the one-toothed intermediate wheel. The intermediate wheel is locked by a lever, which is in contact with a triangular-shaped cam on the top seconds wheel. 3) This cam acts on the lever to release the intermediate wheel. The intermediate wheel travels 180 degrees simultaneously, allowing the lower seconds wheel to revolve. 4) Because the lower seconds wheel is fixed with one end of the constant force hairspring, which is fixed on the other side to the top seconds wheel, this action winds the hairspring. In other words, the lower seconds wheel is always turning slightly ahead of the top seconds wheel to wind its hairspring.

constant force mechanism


wheel, resulting in a loss of amplitude. In the fusée and chain, as the barrel unwinds, the chain compensates for reduced spring tension by achieving greater leverage on the fusée, which in turn places greater tension on the gear train. This then helps to maintain sharp impulses on the escape wheel. The escape wheel transmits this energy into impulses to the balance wheel, which keeps the lift angle high and helps to maintain constant amplitude. But the problem with implementing a fusée and chain is that you must have space for this additional apparatus. In a watch where already three-quarters of all available space is occupied by two huge oversized barrels, the fusée and chain simply could not be THE QUALITY OF POWER One of the problems with considered. any wristwatch is maintaining a good quality of power This left Lange with only one alternative, which as the mainsprings uncoil. At their full wind, the springs is to create a constant-force mechanism known transmit high power, which translates into high torque to the as a remontoir. If you look at a remontoir from the gear train. This, in turn, sends sharp, precise bursts of energy perspective of an escape wheel and balance, it serves to the regulating organism known as the balance. Quality precisely the same purpose as the fusée and chain, of power is of an even greater concern in long power reserve which is to send brighter pulses of energy to the escape watches where the deviation in quality of power between the wheel even as the energy in the mainspring wanes. It A. Lange & Söhne Pour first three days and the last four days of spring wind can be achieves this by isolating the impulses of the escape le Mérite Tourbillon immense. As power diminishes, the pulses wheel to the balance from the gear train. It of energy to the balance become weaker. takes power from the gear train to charge This can cause the lift angle of the balance up its own regulating system – either a wheel — the angle it travels before it swings spring in wristwatches, or a set of weights in the opposite direction — to diminish. The and pulleys in clocks – which, in turn, total degree of travel between the extremes of sends regular energy to the escape wheel oscillation is known as its amplitude. To have and balance. a loss of amplitude means that the balance is To ensure that the optimum energy is The fusée and chain not swinging to its outer extremes because produced throughout the vast 31-day it is not being fed enough power. This lifespan of the Lange 31, the Lange uses a results in timing inaccuracies. To have four days of poor quality power remontoir mechanism, becoming the third manufacture after Françoisor diminished amplitude totally negates the rationale for having a long Paul Journe and DeWitt to successfully implement this complication. But power reserve watch. while Journe and DeWitt use their remontoirs to power tourbillons, the Lange 31 is the first timepiece to use this constant-force device to ensure CONSTANT-FORCE MECHANISMS Luckily, maintaining a constant high accuracy of a basic watch with an extremely long power reserve. rate of quality of good power over the lifespan of a watch happens to That is to say, in our opinion, Lange is the first to see a profoundly be something that A. Lange & Söhne knows a fair bit about. Lange has functional application for this mechanism. already created two watches that address the diminishment of amplitude In the Lange 31, the pre-tensioned remontoir spring is fixed to the as the spring barrel empties by using a fusée-and-chain mechanism — arbor of the fourth wheel, also known as the seconds wheel. Note that the Pour le Mérite Tourbillon and 2005’s Tourbograph. The fusée-and- the seconds hand of the watch is also attached to this arbor. Every ten seconds, the spring is tensioned by 60 degrees. The balance of the movement assures the uniform rotation of the fourth wheel and thus, the cyclical winding of the remontoir. The remontoir consists of a cam shaped like an equilateral triangle with convex sides attached to the arbor of the seconds wheel. Every ten seconds, the cam moves a pivoting lever. The lever is fixed with two pallets that engage a single-toothed wheel. This wheel is connected to the coupled stacked spring barrels via a wheel train. It briefly stops chain mechanism is thought to have been invented by Leonardo da Vinci the motion of the spring barrel every 180-degree turn. At the same hundreds of years ago and it essentially uses leverage to compensate for time, each time the wheel turns, the remontoir spring is incrementally waning spring tension. A chain is fixed between the spring barrel and the rewound within fractions of a second, and during the following ten fusée, which is a ramped cone placed co-axially to the center wheel. As seconds, it delivers its energy to the escape wheel. So there you have it, the barrel’s energy depletes, the barrel places less tension on the gear in a land of increasingly complex marketing-derived smoke and mirrors, train, which subsequently sends weaker energy to the escape wheel. This, the Lange 31 is a sublime expression of functional watchmaking at its in turn, sends less intense impulses to the balance wheel. It is precisely best. Stay tuned for more details of the intriguing remontoir system in these weaker impulses that cause the reduced lift angle for the balance this watch. H


power can be the source of great productivity. Understanding this, the technicians at Lange & Söhne have constructed two massive, stacked barrels to contain the immense power of the two 1,850-mm mainsprings (each of these is five to ten times longer than any conventional mainspring), to channel their vast quantities of energy into power of exceptional quality. Finally, because the springs are so powerful, a conventional winding crown would not generate adequate leverage to wind them effectively. As such, Lange & Söhne has revived the key winding system used in pocket watches. At the rear of the watch, the key is inserted through an aperture to directly wind both barrels, while a clutch prevents overwinding.

power reserve

power reserve

power reserve

ANATOMY OF A MASTERPIECE – INSIDE A. LANGE & SÖHNE’S REMONTOIR Please note that ‘top seconds wheel’ and ‘lower seconds

wheel’ are not technical terms, but they are used for clarity. The top seconds wheel is actually the second seconds wheel (independent of the mainspring), while the lower seconds wheel is the seconds wheel (powered by the mainspring).

TOP SECONDS WHEEL: This is what gives power to the escapement. Rather than receive its energy from the mainspring (which varies in torque according to its state of wind), the wheel receives its energy from a hairspring fixed to its center. It is perhaps A. Lange & Söhne’s specialization in in-house hairsprings that has allowed the development of this technology. LOWER SECONDS WHEEL: This wheel is powered by the mainspring. Since

it doesn’t contact the escapement directly, the only thing regulating the flow of power to this wheel is the one-toothed intermediate wheel. The purpose of this wheel is to wind the top seconds wheel. So, when the one-toothed intermediate wheel is released by the pivoting lever, which is in turn activated by a special cam on the top seconds wheel, the lower seconds wheel rotates very quickly. Because one end of the hairspring of the top seconds wheel is fixed to it, this action winds the hairspring, giving it enough power to run autonomously for another ten seconds.

ONE-TOOTHED INTERMEDIATE WHEEL: This wheel has two purposes. It stops

the flow of power from the mainspring, isolating the top seconds wheel from the mainspring’s changing torque. At the same time, it releases the energy of the mainspring to turn the lower seconds wheel, which in turn

pivoting lever

winds the hairspring of the top seconds wheel. PIVOTING LEVER: This pivoting lever has two toothed ruby pallets in the

center, which stop the one-toothed intermediate wheel and momentarily cuts off the flow of power from the lower seconds wheel. On the far right, the lever ends in a kind of fork with two additional rubies. This fork is contacted by a special triangular-shaped cam with convex sides fixed to the top seconds wheel. The action of this cam causes the lever to shift enough every ten seconds, so that the one-toothed wheel is released, allowing it to unleash power from the mainspring. The lever is attached on the far left to a counter-weight to keep it balanced and to ensure that the pallets stay in contact with the triangular cam.

IN CONVERSATION WITH ANTHONY DE HAAS – A. LANGE & SÖHNE’S PRODUCT DEVELOPMENT DIRECTOR How many seconds wheels are there in this constant force mechanism?

There are two seconds wheels. They are co-axially mounted, one on top of the other. For the sake of clarity, we can call them the lower seconds wheel (mainspring driven) and the top seconds wheel (hairspring driven). Which is powered by the mainspring? The lower seconds wheel is mainspring powered. The seconds wheel is geared with the pinion slightly to the left, which drives the special one-toothed intermediate wheel, so this wheel is also mainspring driven. What is the function of this intermediate wheel? You can see that the

intermediate wheel’s tooth is in contact with one of the two ruby pallets

intermediate wheel triangular-shaped cam

of the special pivoting lever. As a result, the intermediate wheel – which, as I’ve mentioned, is geared to the seconds wheel that is driven by the mainspring – is blocked by the lever. And so, the power from the mainspring is blocked. Now, every ten seconds, the intermediate wheel is released and the power of the mainspring is released with it. The wheel jumps 180 degrees to the opposite pallet. The lever is released by the triangular-shaped cam on the top seconds wheel (the one with the hairspring on it). This cam is fixed to the pinion of the top seconds wheel and turns with it. As you can see from the image provided, the cam contacts the two rubies on the side of the fork projecting out of the pivoting lever. So, what happens next? As the intermediate wheel rotates 180 degrees, it allows the lower seconds wheel to turn. Now, as you can see, the top seconds wheel is fixed with a special hairspring and it is this hairspring that drives the wheel in ten-second periods of fixed energy. Because this hairspring is what creates the regularity of impulse to the escapement, you have constant force being delivered to the balance. But of course, this hairspring needs to be rewound every ten seconds. Also, because it is fixed to something that is always turning, the mechanism winding it must also turn.

for the first five days, the energy would be so huge that the balance would be overbanking... You would have some crazy amplitude of something like 550 degrees. The irony is that the longer the power reserve you create, the larger the disparity in torque between the first and last days of power reserve, which would give you a wild variation in amplitude and timing accuracy. For us, this is a new idea. There are other patents that apply different solutions to this problem, but we are very proud of implementing this one, because it is really functional and works across the entire 31-day lifespan of the watch. If you want to make a watch with a long power reserve, you have to ensure the time-keeping accuracy. A long power reserve watch without a constant force mechanism simply makes no sense. H

lever triangularshaped cam

How is this constant force mechanism’s hairspring rewound? It is the mainspringdriven lower seconds wheel that fulfills both of these purposes. Look closely and you will see that the hairspring is fixed to the top seconds wheel on one side, and to the lower seconds wheel on the other side. Once the intermediate wheel releases the lower seconds wheel, it rewinds the hairspring, which drives the top seconds wheel. And it is this top seconds wheel that delivers power to the escapement. When did your team start this project and what were you inspired by? Ferdinand Adolph Lange used a constant force mechanism in many of his works, such as the one found in the big clock located in his old house. If you visit us, it is very entertaining to look at because the pendulum of this clock travels all the way through several floors of the house and ends in the basement. You are correct in that when we first embarked on this project, we initially tried to implement a chain and fusée in the watch, but because the barrels occupied so much space, it was basically impossible. So, we searched for other solutions.

counter weight

intermediate wheel

pinion of intermediate wheel

constant force hairspring

top seconds wheel

constant force hairspring

top seconds wheel

lower seconds wheel


bottom seconds wheel

characteristic of Lange. It’s great to have a long power reserve watch, but you will never get good timing results from something that has two huge barrels without a constant force mechanism. If we removed this device and connected the gear train to the escapement




Explain how this is a functional innovation

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