Rotonde de Cartier perpetual calendar chronograph
The Rotonde de Cartier perpetual calendar chronograph watch offers a rare luxury: it combines the measurement and display of short periods of time with a mechanism whose gears possess the ability to compensate for the irregularities of the Gregorian calendar.
The Master watchmakers of the Cartier Manufacture have daringly incorporated these essentially urban features into a carefully restrained yet precious model in white or pink gold. Its overall diameter of 42 mm and its alligator-skin strap are entirely in tune with the expectations of city dwellers who want an instrument fitted with two 100% Cartier complications that are among the most highly appreciated in the marketplace. The first is the perpetual calendar that continuously indicates long periods of time; the second is a new column-wheel chronograph calibre that, on demand, measures much shorter periods, such as brief events, with great precision.
Measuring the long periods of life
Ever since the earliest days of watchmaking, craftsmen have strived to master time in two distinct areas: long periods and short periods. From the invention of the first pendulum clocks, the makers have tried to create mechanisms that cope with the problems of the Gregorian calendar in order to display not only the time but the calendar information as accurately as possible. A long series of improvements led to the production in the early 19th
century of watches able to display calendar information that not only took account of 30- and 31-day months but added an extra day to February in every leap year. This ingenious development, designed to compensate for the irregularity of the Gregorian calendar, requires a delicate, complex mechanism of cams and snails. At its heart is a wheel that completes one revolution every four years, with 48 indentations of varying depths on its circumference that indicate, via a feeler, whether the current month comprises 30, 31, 28 or 29 days. This module also incorporates a retrograde hand, indicating days of the week at 6 o’clock, as well as a specific mechanism for displaying the date, which is indicated by a hand on the edge of the dial. The three calendar displays are controlled by rapid correctors incorporated into the case middle. These enable the wearer to easily reset the information on the dial in case this entirely new Manufacture automatic chronograph calibre stops.
A manufacture chronograph calibre
This delicate mechanical assembly already existed in the Cartier collection and is often simply called ”the Module” by the watchmakers. It has been adapted to the completely new Manufacture calibre 1904-CH MC. This self-winding mechanical chronograph movement incorporates a number of technical innovations intended to increase its precision and power. This mechanical heart is carefully hand-finished to the highest standards of fine watchmaking, including an openwork oscillating weight, and it is powered by two barrels in order to raise its torque and give it a power reserve of 48 hours. Another important innovation in this model is an in-line, flexible lever that reduces stress on the bearings of the hand shafts when the displays are reset to zero. And because it is essential today to ensure accuracy in short-period timing, the watchmakers of the Cartier Manufacture at la Chaux-de-Fonds have chosen to use the latest generation of vertical clutch that allows timings to start with no hand jump and to operate without affecting the torque of the calibre.