In the 2875 calibre, the entire movement was enlarged by about a third, with the
everyday performance of the movement taking precedence over the record size.
Enlarged in turn, the platinum/iridium weight (7.62 g.) was fitted with a jewel
bearing and losses due to friction were reduced to a minimum.
The movements of the weight, which oscillates in one direction and then the other,
depend on the activity of the wearer on the one hand, and terrestrial attraction on
the other hand (see figures below). The weight is stopped at the end of travel over
a few tenths of a millimetre and slowed by a spring. This stoppage, however, causes
watch vibration and a slight noise perceptible to the wearer.
Important: The speed of movement of the weight, which can be increased by a
sudden movement of the wearer, determines the intensity of these phenomena.
The weight is positioned near 1 pm, for three reasons:
1. Due to its optimum position on the wrist, where to-and-fro arm movements
are most frequent (see figure below), the platinum/iridium weight ensures very
effective winding with just the slightest movements.
2. The tourbillon cage should always be designed as large as possible to ensure
highly accurate operation.
3. The aim being to obtain a thoroughly clear view of the tourbillon, its interior
had to be concealed by no part of the winding mechanism.
2.3 Power reserve
The power reserve indicates the efficiency of the automatic winding mechanism and
the time at which the watch will stop if not wound up.
The 2875 calibre has a 54-hour power reserve, which gives a virtually flat power
curve and good operating accuracy.
Summary of Contents for Calibre 2875
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