The GRAND COMPLICATION represents the pinnacle of Lange watchmaking artistry. Inspired by the Grande Complication No. 42500, a pocket watch that dates back to 1902, it bundles a host of elaborate complications in a single time-keeping instrument.
L1902 GRAND COMPLICATION
The grande sonnerie functions
Grand and small strikes: The GRAND COMPLICATION is endowed with a striking mechanism that activates itself at each full hour and every quarter-hour. The grand strike indicates the full hours together with the quarter-hours. The small strike sounds the quarter-hours and only at the top of the hour the hours. The strike mode can be chosen with a selector in the bottom case flank. The letters refer to the German terms: “G” stands for grand strike, “K” for small strike. The selector at the top of the case allows the striking mechanism to be engaged and disengaged. “S” stands for strike. “R” means rest; in this position, the mechanism is turned off. A separate spring barrel delivers the energy needed for 24 hours when the grand strike is activated.
The minute repeater: The minute repeater is activated with the trigger at 8 o’clock. This function indicates the current time of day acoustically, to the minute. The number of low-pitched tones is the hour count. Double tones stand for quarter-hours and high ones for minutes.
The tweaking and tuning process: The grande sonnerie mechanism is especially challenging for the watchmaker. He is responsible not only for precisely adjusting the switching sequences of all individual parts but also for the richness of the sound. Tuning requires acute hearing and is performed exclusively by hand to achieve sonority and reverberation of both gongs separately and perfect harmony in unison.
The rattrapante-chronograph functions
The chronograph function: The chronograph button in the upper right-hand case flank is used for stopwatch measurements. When the button is actuated, the measurement begins; the stopped time is displayed when it is actuated a second time. The small blued hand in the upper subsidiary dial indicates the measured minutes, the gold-plated chrono sweep-seconds hand the seconds. The flying seconds hand in the lower subsidiary dial stops fractions of a second to an accuracy of one-fifth of a second. All chronograph hands jump back to zero when the button is actuated a third time.
The rattrapante function: The rattrapante button in the upper left-hand case flank expands the stopwatch functionality. If it is actuated during an ongoing measurement, the blued rattrapante sweep-seconds hand stops to display an intermediate time. The gold-plated chrono sweep-seconds hand, concealed beneath the blued hand until that instant, continues to run. When the rattrapante button is pressed again, the rattrapante sweep-seconds hand catches up with the chrono sweep-seconds hand and then runs synchronously with it again. This function can be repeated as often as required. It allows the determination of intermediate times and comparative times.
The flying seconds: The flying seconds is a mechanical rarity. Every second, this hand performs a full revolution in five jumps. A specially designed escapement assures that the hand can perform its movements in a flash, so to speak, and with the utmost precision. The energy needed for this rare additional chronograph function is so considerable that a separate spring barrel is needed to deliver it.
The perpetual calendar functions
The precision of the perpetual calendar: On its dial, the perpetual calendar of the GRAND COMPLICATION indicates the date, the day of the week, the month and the leap-year cycle. All calendar indications are designed to advance instantaneously. The mechanism knows how many days each month has in the course of a year and is also aware of the fact that February has 29 days in leap years. The duration of each month is coded into a 48-step cam with recesses that are mechanically sampled by a lever. The shorter the month, the deeper the recess. Additionally, the watch features a moon-phase display.
The correction in the year 2100: The calendar displays must be corrected by one day but not until 2100. In that year, the Gregorian calendar omits the 29th of February according to the rule that leap years are skipped in secular years which are not divisible by 400. The adjustment is performed with correctors. All calendar displays can be advanced by one day with the main corrector at 12 o’clock. Once the watch has stopped after being set aside for a lengthier period of time, the displays can be conveniently updated with two additional correctors that can separately advance the day of the week and the month. The moon-phase display is always adjusted separately with the corrector located at 5 o’clock.