A. Lange & Söhne Lange 31

Precision Watchmaking. Watchmakers take pride in building what has never been done before. Sometimes the functional value of these creations is questionable, and almost always the price of these creations are prohibitive.

A. Lange & Söhne Lange 31. One such creation is the A. Lange & Söhne Lange 31. On its face, the Lange 31 is a date watch with a power reserve indicator. The power reserve indicator is a not a commonly found feature in wristwatches, but it is not unique. What makes the Lange 31 unique is that the power reserve indicator displays a power reserve of 31 days.

Inside the fairly large 45.9mm case diameter is the A. Lange & Söhne L034.1 maunal winding movement. This movement stores enough energy to keep the Lange 31 running non-stop for a period of 31 days. The energy storage function is handled by a large twin mainspring barrel with two stacked spring barrels. They barrels contain the two mainsprings, each of which is 1,850 millimetres long. These springs are five to ten times as long as the springs of conventional mechanical wristwatches.

The problem with placing such powerful mainsprings is that barrel has its maximum force when the spring is fully wound and then declines substantially as the spring relaxes. The wide range of power delivered by the mainspring makes delivery of the constant power needed to for precision timekeeping difficult. To harness the power of the powerful mainspirng A. Lange & Söhne watchmakers used a constant-force escapement.

The main element of this mechanism is a pretensioned spiral spring that is quickly retightens on the fly at intervals of ten seconds. During the ten seconds that follow, the energy stored in the spring is delivered to the going train in a controlled manner. The torque output is virtually constant and powers the watch uniformly throughout 31 days.

Key Winding Mechanism. In order to wind the watch, instead of a watch a key is provided to wind the watch. The key is inserted into a slot at the back of the watch. It allows a considerably larger winding transmission ratio than would be possible with a crown. So fewer rotations are needed to wind the watch.

The winding key

To prevent inadvertent overtightening of the mainsprings, the key features an integrated torque limiter. An attempt to turn the key further - once the mainspring is fully wound - disengages the triangular toothing of two wheels inside the key and interrupts the flow of power.

The watch is built of precious metal, the case of the watch is being made of Platimum and the dial is made of solid silver.

About A. Lange & Söhne. A. Lange & Söhne was founded in 1845 by Ferdinand Adolph Lange in Glashütte, State of Saxony. During World War II arial bombardment decimated its workshops. After the war, what was left of the company's property was expropriated the post-war socialist regime in 1948. With this, the A. Lange & Söhne brand ceased to exist.

In 1989, after the collapse of the Berlin Wall and the end of the East German government, Adolph Lange's great-grandson, Walter Lange, sought to reestablish the company. A year later, with the help of IWC and the Richemont Group, A. Lange & Söhne reopened its doors in the city of Glashütte.