WatchTime - August 2012

turns to zero, the complexly shaped tip of the minutes-counter
lever dips into this indentation so that the hand can neither become
deformed nor slip on its staff. After a little leftward swing,
the hand returns to the 12 o’clock position without the slightest
wagging. Also new: the balance oscillates at 4 hertz (28,800 vph)
instead of the previous rate of 2.5 hertz (18,000 vph).
Patek Philippe is acknowledged as a pioneer in the development
of perpetual calendars for wristwatches. Its expertise is evident
in Reference 5270, the chronograph with perpetual calendar
introduced in 2011. Caliber CH 29-535 PS Q uses the CH
29-535 PS as a base, with the addition of a perpetual calendar.
This, too, is a new construction. The calendar unit wasn’t simply
installed on top as a module; it required modifications in the
chronograph. Patek Philippe’s technicians repositioned both the
subdial for the seconds and the elapsed-minutes counter slightly
downward toward the 6 to make room for larger disks indicating
the day and the month. They also equipped this 1.65-mmthick
mechanism with a rotating cam that “tells” the calendar’s
mechanism how long each month should be in each ordinary
year and each leap year until the year 2100. The moon-phase indicator
underneath the little date display does its job with admirable
precision, too: its error will amount to one full day’s deviation
only after 122 years and 45 days. Should this display require
adjustment before then, the user need only press the little
button on the side of the watch’s case.
WITH REFERENCE 5204, Patek Philippe went a step further
and added a split-seconds function to its CH 29-535 PS Q
movement, thus rounding out its collection of in-house chronograph
calibers.
Two unconventional details in its construction distinguish
this newcomer from the older rattrapante caliber CH 27-70/150
that Patek Philippe used in Reference 5004. The first difference
has to do with the isolator. Patek Philippe’s design engineers analyzed
the older isolator, which connoisseurs called the “octopus,”
and found a way to improve it. The new version relies on
a bidirectional spring installed as a kind of covering plate above
the split-seconds column wheel. The construction is ingeniously
simple: the push-button mechanism (the button is on top of the
crown) and the isolator-spring’s end (the latter is cut with socalled
“wolf’s teeth”) move the likewise wolf-toothed isolator
wheel just far enough so that a prong, affixed to the wheel, can
lift both the split-seconds lever and its roller for the interval during
which the split-seconds heart is stopped.
The second innovation, which can only be seen through a
watchmaker’s loupe, is to be found next to the ruby roller on the
patent-protected split-seconds lever. The roller itself has remained
unchanged. Due to the system used in previous constructions,
slight pendular motions were almost impossible to
prevent when the roller rests in the notch of the split-seconds
heart. But the new caliber solves this problem with two little
supportive surfaces, one positioned to the left and the other to
The dial side
of Caliber
CHR 29-535 PS Q
Caliber CHR 29-535 PS Q: the chronograph
mechanism with split-seconds
capability is visible from the back.
August 2012 WatchTime 53