Complications: Splitting Time with the Rattrapante

The chronograph often features at the top of people’s lists of the most loved or desired complication. Whether it’s timing laps at the track or contractions in the delivery room, most chronograph wearers cannot wait for the next excuse to press those pushers and set the gears in motion.

If the standard chronograph is much revered in terms of function, beauty, and engineering, then the split-seconds chronograph takes that to a whole new level. Commonly known as the rattrapante, but also referred to as a doppelchrono in German, a split-seconds chronograph introduces into the mix a second chronograph seconds hand that can be stopped, started, or set back to zero, allowing you to time multiple events at the same time.

For example, let’s say you want to time the total duration of a race. A simple chronograph is all you need for that. Now, let’s say you also want to be able to time one lap of the race while still measuring its total elapsed time. That’s when a rattrapante is ideal.

The complication was originally intended for use in timing sporting events. It was first seen in pocket watches towards the end of the 19^th century, with Swiss watchmaker Adolphe Nicole taking the credit for its development. Like most complications, the rattrapante eventually made its way into a wristwatch, and Patek Philippe led the race in the early 1920s. By the late 1950s, Venus calibers such as the 179 were widely used by the likes of Breitling (among others). And then, much later in the early 1990s, IWC’s Richard Habring engineered a rattrapante extension to the ETA/Valjoux 7750. Most modern and reasonably-priced rattrapante wristwatches are likely to use a derivation of the 7750.

From the wearer’s point of view, the complication is functionality through and through. The chronograph can be started, stopped, and reset as normal—usually via the pushers flanking the crown on the right-hand side of the case. The split-seconds function is actuated using an additional pusher, often on the other side of the case (note the pusher at 10 o’clock in the image above). With the chronograph running and both centrally mounted chronograph seconds hands advancing along the dial, pressing that additional pusher will cause the hands to “split” into two parts. The first, which is the main chronograph hand, will continue its track around the dial, measuring elapsed time from when the chronograph was first started. The second, additional hand stops dead. This allows the wearer to pause and record the elapsed time up to that point, such as the time taken for a lap, without disrupting the other measurement.

As you can see in the above video, pressing the additional pusher again will see the split-seconds hand catch up (or “rattraper” in French) to the main chronograph seconds hand, which has continued its merry journey. This sequence of actions can happen time and time again, enabling you to accurately and easily record each lap while also recording the total elapsed time.

The additional functionality on top of a regular chronograph isn’t all that advanced in relative terms, and it’s now often developed as a module that operates supplementary to the regular chronograph mechanism. Instead of one center wheel, which is connected to the chronograph seconds hand, there are two wheels, each of which is connected to one portion of the “combined” chronograph seconds hand.

As the wheel for the primary chronograph seconds hand rotates, it also drives the rattrapante seconds hand wheel, which rests in the heart-shaped cam of the first wheel. Under normal circumstances, its position is maintained by a spring pushing against it to keep it in that lowest point of the cam. The two wheels, and therefore both hands, travel in synchronized motion until the rattrapante pusher is actuated.

When the rattrapante pusher is actuated, the two arms that have been sitting poised in anticipation will effectively clamp the additional wheel in position, pausing the motion of the rattrapante seconds hand. At this point, the additional rattrapante wheel is unseated from its mounting within the heart-shaped cam of the first wheel while the main chronograph seconds wheel continues to turn. When the clamp is released, the spring jumps the rattrapante wheel and hand in line with the main chronograph hand.

Take a look at this nifty video from Lange for some perspective.

One of the reasons the rattrapante is uncommon below a certain price bracket is the precision that’s need to bring the whole thing together. The split-seconds hand needs to sit perfectly in line with the first hand, and it needs to snap back without issue. It also needs to have enough force from the spring to stay in sync as the two hands travel together around the dial, but not enough force to cause a stutter or slowing of the main seconds hand as the additional wheel is locked in place.

As I mentioned above, outside of rather expensive in-house calibers, the movement you are mostly likely to see featuring a rattrapante chronograph complication is a modified 7750. When IWC’s patent on the Doppelchronograph expired, Richard Habring seized the opportunity to use the same engineering in his Habring² brand, and the complication remains a focal point of his watches to this day. In their Doppel range, Habring² combines the complication with a two-register layout for a very clean design. The latest watch in the series, the Doppel 3, is limited to approximately 20 pieces per year with a price of 6,750 EUR.

With a relatively affordable solution now also more accessible to others, the rattrapante is no longer solely reserved for high-end chronographs, although it is still far from common and still commands a hefty premium above a more vanilla 7750 chronograph. One of the more recent examples of an ETA-based, split-seconds chronograph is Sinn’s 910 Anniversary Edition—a limited release of just 300 pieces retailing at $5,940.

In the world of one-upmanship that is the watch industry, the split-seconds chronograph was never going be the pinnacle of achievement in this territory. In 2013, A. Lange & Sohne created the world’s first “Double Split” chronograph, where it is not only the seconds hand that is capable of splitting (and re-catching), but also the minute totalizer. And if this weren’t enough (and it never is), 2018 saw the German horological powerhouse go a step further with the “Triple Split,” where the hours are now also included in the rattrapante function. Needless to say, it is unlikely that the triple-split chronograph will trickle down to the lower priced segment of the market any time soon.