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A. Lange & Söhne
Lange 31
Lange 31

Price not available


Référence du produit


  • 130.025
Boîtier du produit


  • Material : Platinum
  • Diameter : 45.90mm
  • Thickness : 15.90mm
  • Back : Sapphire
Mouvement du produit


  • Type : Manual-winding mechanical
  • Power reserve : 744h
  • Frequency : 21600 Alt/h
Cadran du produit


  • Colour : Silver
Bracelets du produit


  • Material : Leather
  • Buckle type : Folding buckle
Fonctions du produit


  • Date
  • Hours
  • Minutes
  • Power reserve
  • Seconds

The LANGE 31: Key technology with power for an entire month

No other watch runs longer: The new manually wound A. Lange & Sohne timepiece

has a power reserve of one month. That is why it has been named the LANGE 31.

Another innovation, a constant-force escapement, assures that power delivery is

uniform throughout the entire 31-day period. Additionally, Lange reintroduces the

venerable key winding mechanism.

People have always been fascinated by the waxing and waning of the moon. So much

so, in fact, that already the oldest calendars used the span between two new moons as

their basic unit of time. The construction of a mechanical wristwatch with a power

reserve of a whole calendar month, not to mention constant rate accuracy across the

entire period, was one of the few as yet unmastered horological feats. Now, it is reality:

the LANGE 31. A programmatic designation for a power pack with the so far unimaginable

power reserve of 31 days – plus continuous rate stability. With it, the horological

year is now subdivided into 12 “winding sessions”.

To store this amount of energy, the LANGE 31 features two stacked mainspring barrels

with an inside diameter of 25 millimetres. The prominent twin barrels occupy three

quarters of the movement's footprint. Each measuring 1,850 millimetres in length, the

two mainsprings are five to ten times longer than those found in conventional

wristwatch movements. Their combined energy is enough to lift a 100-gram bar of

Swiss chocolate 320 centimetres – more than 10 feet. It would be quite a cumbersome

task to wind strong springs like these with the delicate components of an ordinary

winding crown train. That is why Lange's engineers turned to the “key technology” of

historic pocket watches. The leverage delivered by a key makes it possible to choose a

transmission ratio that would be inconceivable with a crown. A square key, inserted

through an aperture in the sapphire-crystal caseback, delivers the energy to the spring

barrels. The key features a built-in backstop ratchet to allow smooth winding as with a

regular crown, and a torque limiter prevents accidental overtightening of the springs.

Uniform energy delivery for the escapement

It stands to reason that a movement with such an extraordinary power reserve cannot

constantly run at a stable rate without special technical precautions. The laws of

physics dictate that in the process of relaxing, a spring loses more and more of its initial

torque and thus cannot deliver the same amount of energy between the points where it

is fully wound and fully unwound. As its torque wanes, the amplitude of the balance

declines and so does the rate accuracy of the movement. To outwit this law, Leonardo da Vinci invented the fusee principle 500 years ago. It allows the spring's loss of torque

to be largely offset by leverage. In the form of a fusee-and-chain transmission, this

principle has been embodied in two of Lange's new-era watches: the TOURBILLON

“Pour le Merite“ and the TOURBOGRAPH “Pour le Merite“. But to handle a power

reserve of 31 days, this construction would have been made impossible by the sheer

size of its parts. So Lange's engineers sought – and found – a different solution: the

constant-force escapement. It is based on an auxiliary spring that is periodically

rewound by the mainspring and always builds up the same torque, regardless of the

state of wind of the mainspring.

As it relaxes, this pretensioned so-called remontoir spring on the fourth-wheel arbor

always delivers the same amount of energy to the escape wheel. Every ten seconds,

this spring, attached to a stud, is retensioned by 60 degrees at its outer end. To

complete the mechanism, it is also necessary to integrate a device that dependably

and accurately controls this motion sequence. This task is handled by the balance. It

not only assures the uniform rotation of the fourth-wheel arbor that indicates the correct

time but also controls the cyclical winding of the constant-force escapement. This is

done with a Reuleaux polygon, a cam shaped like an equilateral triangle with convex

sides. It is attached to the fourth-wheel arbor. Every ten seconds, in other words after

every 60-degree rotation, it moves an ingeniously designed pivoting lever. Two pallets

on the inside of the lever alternately engage with a one-toothed wheel that is connected

to the spring barrel via a wheel train and briefly stops its motion after every 180-degree

rotation. Each time it 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. Within these ten seconds, the torque curve fluctuates marginally, but on

average, a constant amount of energy is delivered for the full 31-day period. The

motion sequence of the constant-force escapement, which indeed resembles a classic

escapement, can be observed through the sapphire-crystal caseback. A transparent

sapphire jewel reveals the fascinating interaction of the three-point cam with the

pivoting lever.

On the bottom line, the constant-force escapement prevents the waning torque

provided by the mainspring barrel from diminishing the rate accuracy of the watch. The

result: uniform energy delivery, constant amplitude, same rate accuracy from the first to

the thirty-first day on which a shutoff mechanism halts the movement. Theoretically, the

movement could continue to run. But then, the force generated by the mainspring

would drop below the torque needed to wind the remontoir spring. The constant-force

escapement would no longer function reliably.

Historic continuity

The constant-force issue already preoccupied Ferdinand Adolph Lange. Around 1866,

he invented a constant-force escapement with jumping seconds – a so-called “onesecond

remontoir” – for his precision pocket watches. He later developed a similar

construction for the large house clock at the Lange headquarters which today, with its

almost 10-metre long pendulum, still tells Lange staff members and citizens of

Glashutte precisely what time it is. Some 140 years later, his horological descendants

demonstrated the success of their quest for constancy by introducing the newly

developed calibre L034.1 movement with 31 days power reserve. It is an exceptional

timekeeping instrument for daily use, and its convenience is readily apparent. It

displays the precise time longer than any other manually wound watch, even if it is not

worn for several days or a few weeks. The LANGE 31 is a seamless continuation of an

old Lange tradition: to create useful innovations.

The platinum case of the LANGE 31 has an impressive diameter of 46 millimetres and

an overall height of 15.9 millimetres. After all, it takes space to store so much time. And

the circular 31-day power-reserve indicator that occupies nearly the entire right-hand

half of the solid-silver dial requires space as well. It is the hallmark of a true breakthrough

in horology. The last segment, in red, reminds the owner that after a full month

has elapsed, it is finally time to rewind the watch. The Lange outsize date on the left

side harmoniously balances the face. Needless to say, the LANGE 31 also showcases

all of the quality features that make timepieces by A. Lange & Sohne so coveted

around the world. A glance through the sapphire-crystal back reveals the screw

balance, the whiplash precision index adjuster on the hand-engraved balance cock,

screwed gold chatons, and lavishly decorated elements in the classic Lange style.

The brand

Following the vision of Ferdinand Adolph Lange to build the world’s best watches, A. Lange & Söhne strives for ultimate precision and explores new avenues in order to advance the art of fine watchmaking.

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