What 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 platinum-cased 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, 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.

THE QUALITY OF POWER One of the problems with any wristwatch is maintaining a good quality of power as the mainsprings uncoil. At their full wind, the springs transmit high power, which translates into high torque to the gear train. This, in turn, sends sharp, precise bursts of energy to the regulating organism known as the balance. Quality of power is of an even greater concern in long power reserve watches where the deviation in quality of power between the first three days and the last four days of spring wind can be immense. As power diminishes, the pulses of energy to the balance become weaker. This can cause the lift angle of the balance wheel — the angle it travels before it swings in the opposite direction — to diminish. The total degree of travel between the extremes of oscillation is known as its amplitude. To have a loss of amplitude means that the balance is not swinging to its outer extremes because it is not being fed enough power. This results in timing inaccuracies. To have four days of poor quality power or diminished amplitude totally negates the rationale for having a long power reserve watch.

CONSTANT-FORCE MECHANISMS Luckily, maintaining a constant rate of quality of good power over the lifespan of a watch happens to be something that A. Lange & Söhne knows a fair bit about. Lange has already created two watches that address the diminishment of amplitude as the spring barrel empties by using a fusée-and-chain mechanism — the Pour le Mérite Tourbillon and 2005’s Tourbograph. The fusée-and-chain mechanism is thought to have been invented by Leonardo da Vinci hundreds of years ago and it essentially uses leverage to compensate for waning spring tension. A chain is fixed between the spring barrel and the fusée, which is a ramped cone placed co-axially to the center wheel. As the barrel’s energy depletes, the barrel places less tension on the gear train, which subsequently sends weaker energy to the escape wheel. This, in turn, sends less intense impulses to the balance wheel. It is precisely these weaker impulses that cause the reduced lift angle for the balance 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 considered.

This left Lange with only one alternative, which is to create a constant-force mechanism known as a remontoir. If you look at a remontoir from the perspective of an escape wheel and balance, it serves precisely the same purpose as the fusée and chain, which is to send brighter pulses of energy to the escape wheel even as the energy in the mainspring wanes. It achieves this by isolating the impulses of the escape wheel to the balance from the gear train. It takes power from the gear train to charge up its own regulating system – either a spring in wristwatches, or a set of weights and pulleys in clocks – which, in turn, sends regular energy to the escape wheel and balance.

To ensure that the optimum energy is produced throughout the vast 31-day lifespan of the Lange 31, the Lange uses a remontoir mechanism, becoming the third manufacture after François-Paul Journe and DeWitt to successfully implement this complication. But 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 high accuracy of a basic watch with an extremely long power reserve. That is to say, in our opinion, Lange is the first to see a profoundly functional application for this mechanism.

In the Lange 31, the pre-tensioned remontoir spring is fixed to the arbor of the fourth wheel, also known as the seconds wheel. Note that 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 the motion of the spring barrel every 180-degree turn. At the same time, each time the wheel turns, the remontoir spring is incrementally rewound within fractions of a second, and during the following ten seconds, it delivers its energy to the escape wheel. So there you have it, in a land of increasingly complex marketing-derived smoke and mirrors, the Lange 31 is a sublime expression of functional watchmaking at its best. Stay tuned for more details of the intriguing remontoir system in this watch.

A. Lange & Söhne 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 A. Lange & Söhne CEO, Fabien Krone

The fusée and chain

A. Lange & Söhne Pour le Mérite Tourbillon

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


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 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.

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 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.

How is this constant force mechanism’s hairspring rewound? It is the mainspring-driven 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.

Explain how this is a functional innovation 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 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.


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