Historically inspired: jumping seconds from A. Lange & SöhneSIHH 2018: The 1815 Homage to Walter Lange
In general, mechanical timepieces can be recognised by their "creeping seconds" hand. Depending on the balance frequency, the hand advances from second to second in five to ten steps. In short-time measurements, however, where seconds count in the literal sense, constant progression sometimes makes it difficult to pinpoint the beginning and the end of an event.
Conversely, there is a horological complication that allows the exact measurement of the smallest unit of time: the "jumping seconds".
The 1815 "Homage to Walter Lange" masters both chronometric disciplines. The small seconds hand in the subsidiary dial at 6 o'clock maps the frequency of 21,600 semi-oscillations per hour by performing six small steps as it advances from marker to marker. However, the blued centre seconds hand performs precise jumps from second to second. It can be allowed to run continuously or immobilised if needed. A pusher at 2 o'clock starts and stops it. This is useful for heart rate measurements, for instance.
The jumping centre seconds hand with the start/stop function was especially significant for Walter Lange. This is because it dates back to an 1867 invention of his great-grandfather, Ferdinand Adolph Lange. It was first implemented in a masterpiece crafted by his grandfather, Emil Lange. One of Germany's first patents was granted to A. Lange & Söhne in 1877 for the enhanced design of a mechanism mounted on the three-quarter plate, and was referred to as a "one-second movement with a jumping hand".
In the 1815 "Homage to Walter Lange", the seconds jump is controlled according to the flirt-and-star principle, as was originally the case in the historic mechanism. After each full second, one of the six tips of the star liberates the tensioned lever arm, which watchmakers refer to as the "flirt". It then swiftly rotates by 360 degrees before it is stopped by the next tip. This motion sequence causes the seconds hand to advance by one marker. The ratchet wheel located above the three-quarter plate has a dual function: It stores the power needed for the seconds jump, and at the same time causes the centre seconds hand to stop.
An 1815 with jumping seconds likely corresponds to what Walter Lange would have deemed the perfect watch. It is totally reduced to the essence while impressing the enthusiast with a puristic yet technically exciting complication. The blued steel hands contrast well against the argenté-coloured dial with the classic railway-track minute scale. The newly developed movement has a special calibre designation: L1924. It refers to Walter Lange's birth year. Additionally, the first three digits of the reference number, 297, recall his date of birth, 29 July.
With a case diameter of 40.5 millimetres, the 1815 "Homage to Walter Lange" comes in three editions: 145 watches in white gold, 90 in pink gold and 27 in yellow gold. These uncommon numbers are derived from important milestones of the Lange family's history. From 7 December 1845, when Ferdinand Adolph Lange originally established the company, exactly 145 years elapsed until 7 December 1990, the date on which Walter Lange registered Lange Uhren GmbH. Precisely 27 years will have passed between this date and 7 December 2017, the day on which the new model that pays tribute to Walter Lange is being unveiled.