High-Frequency Movements – PART II Chronographs
HIGH FREQUENCY – TIME DIVIDED TO THE MAX
As presented in our first article, frequency has a crucial influence on the precision of watches. Because they divide time in smaller fractions, high-beat watches also allow for higher-resolution measurement… which is crucial for chronographs.
DIVIDING TIME DOWN TO A CERTAIN LEVEL
For chronographs, the question of the relevance of high frequency takes on a different dimension. Since the escapement wheel of a mechanical movement rotates in discrete steps, a chronograph can divide time and display seconds with only a certain degree of accuracy. The seconds hand of a 4Hz movement can only display 1/8th of a second; a 5Hz movement, 1/10th of a second. This is why higher beat watches have smoother second hands… So using high frequencies is not just a matter of precision over time but also a matter of dividing time down to a certain level.
Historically, high-frequency stopwatches were crafted to time events with impeccable precision. Referring to the examples mentioned in the first part of this article, back in the early 19th century, the Louis Moinet Compteur de Tierces (used in the pre-decimal era, the tierce is a 1/60th of a second) ran at 30Hz. In 1916, Longines, Heuer (with the Mikrograph) and Minerva were crafting stopwatches using a 50Hz frequency and capable of timing 1/100th of a second.
Several high-frequency chronograph wristwatches have been developed. It's natural that the automatic 5Hz Zenith El Primero immediately comes to mind, but many other 5Hz chronographs followed. For example, at Blancpain and Parmigiani Fleurier recently.
DISCONNECTING OPERATIONS - DUAL ARCHITECTURE CHRONOGRAPHS
But increasing the frequency higher is no small challenge. Unlike stopwatches, wristwatch chronographs are smaller and work two-fold: they display the time of the day, and they can time events. Traditionally, these rely on a timekeeping 'motor' on which a second gear train engages to drive the chronograph. Watchmakers have started to design chronographs with two independent "sub-movements", one to keep track of the time and the other to time events – each sub-movement is composed of one energy source, one gear train and one regulator.
With these dual architectures, there is no clutch, hence no interaction between the timekeeping indication and the chronograph function. This allows watchmakers to achieve high frequency or ultra-high frequency for the chronograph (that is used occasionally only) while doing away with some of the drawbacks of using ultra-high frequency permanently; in particular, the use of a smaller balance wheel, a shorter power reserve, accelerated wear and tear or more frequent maintenance.
As mentioned in our previous article, we have seen several of these chronograph concepts at TAG Heuer. The La Chaux-de-Fonds manufacturer presented the Calibre 360, the Mikrograph, the Mikrogirder or the Mikrotimer Flying 1000 concept watch. The two movements of the latter beat at 4Hz and 500Hz (thanks to a patented high-frequency spiral with no balance wheel), and it was capable of timing events to the 1/1000th of a second. However, the power reserve for this ultra-high frequency chronograph was of 150 seconds only.
In 2012, Montblanc released the Timewriter II Chronograph Bi-fréquence with two balance wheels running at 2.5Hz and 50Hz. When fully wound, the chronograph mechanism's barrel could ensure 45 minutes of running time.
Presented in 2015 by Breguet, the Tradition 7077 runs at 3Hz and 5Hz with power reserves of 55 hours and 20 minutes, respectively. In 2017, Zenith unveiled the Defy El Primero 21 with a timekeeping sub-movement running at 5Hz and a chronograph sub-movement beating at 50Hz. The latter allows the chronograph to display 1/100th of a second. But with this impressive frequency, the function can only run for about 50 minutes.
In 2022, Jacob & Co. released the insanely complex Jean Bugatti (with its unique central chronograph display). It also relies on a dual architecture with a chronograph sub-mechanism paced by a 5Hz balance wheel (2 hours of power reserve, while the time of the day is displayed on the dial's periphery.