The movement may lie hidden within the case, but it makes its presence felt in very palpable ways, from the functions available to the dial’s layout and the pushers’ tactility. Variations abound, but some options are definitely preferred over others here.
Switching and transmission
For a start, there’s the familiar stomping ground of a chronograph’s actuation and coupling to consider. Actuation refers to the “switch” that controls the chronograph. Cam actuation uses the eponymous component, which is fairly easy to produce and assemble, but has a drawback of uneven tactility – the initial force required to start the chronograph is noticeably higher than what’s needed to stop or reset it. A column wheel, in contrast, is more difficult to manufacture and finish than a cam, but promises a smoother pusher feel akin to what gun enthusiasts describe as “snapping a glass rod” when they talk about a trigger’s tactility.
The coupling system determines how the chronograph mechanism is powered by the base movement. In horizontal coupling, a wheel swings horizontally and engages with the base movement to allow the chronograph to draw energy from the gear train. This engagement can be precisely adjusted, since it’s a system of levers that can be visually inspected by the watchmaker. It has its disadvantages though. For one, the connection puts an additional load on the mainspring all of a sudden. This reduces the energy sent to the balance and hence its swing amplitude, which affects isochronism. The meshing of wheels also causes wear and tear, and leads to a chronograph seconds hand that’s prone to flutter and backlash when the chronograph is first started. The vertical clutch does not have these problems, as the chronograph mechanism is constantly engaged with the base movement, and started by frictional meshing of two discs pressing into each other vertically. It’s considered a better solution but does, however, demand more skill in regulation and adjustment.
A movement’s beat frequency typically runs from 2.5Hz (18,000vph) to 5Hz (36,000vph) in modern calibres. All else being equal, a movement with a higher beat rate will be more accurate, as the balance gives more “readings” per second, which averages out any erroneous beat’s timing to a greater extent. This is why quartz movements, whose crystals vibrate at 32,768Hz, are far more accurate than mechanical ones. A chronograph’s resolution corresponds to its beat rate – a 4Hz movement can measure elapsed time down to 1/8th of a second, while a 5Hz one goes to 1/10th of a second. Taken to the extreme, this can yield mindboggling results like TAG Heuer’s Carrera Mikrogirder, which beats at 1,000Hz to give a resolution of 1/2000 second.
Flyback and rattrapante/split-seconds chronographs are variants on the simple chronograph. The flyback function allows a chronograph’s reset pusher to be actuated while the chronograph is running. This makes all its hands “fly back” to zero and continue running without lag – useful for timing consecutive events such as the legs in a plane’s navigation pattern. The rattrapante chronograph has two chronograph seconds hands. Actuating a third pusher stops one of them to allow an intermediate timing to be read, and pushing it again snaps it forward to catch up with the other instantaneously.
|| THE VERDICT ||
The ideal movement for the ultimate sports chronograph should have the following: a column wheel for smooth and confident actuation, vertical coupling for greater accuracy and a precise start to the chronograph second hand, high frequency that’s both more accurate and capable of measuring smaller units of time, and split-seconds functionality to time simultaneous events that will arguably see more use than a flyback function.
Parmigiani Fleurier’s PF361 has all of the above, but is limited to just 50 pieces, and is constructed in gold. Relax the requirements, however, and more options present themselves. There’s Zenith’s El Primero, which remains the only high-beat chronograph movement in mass production, but it uses horizontal coupling and is a simple chronograph. Rolex’s Calibre 4130 is both column wheel-actuated and vertically coupled, but beats at 4Hz and lacks a split-second functionality. The list goes on.
Rolex’s Calibre 4130 with column wheel and vertical clutch TAG Heuer Carrera Mikrogirder Parmigiani Fleurier’s PF361 calibre in the Tonda Chronor Anniversaire. Note the two column wheels