Rattrapante
A split-seconds chronograph; two independent timing hands
What it is
A rattrapante (French: "catch-up") is a split-seconds chronograph that carries two coaxial seconds hands. Both normally move together. Pressing the split pusher freezes the split hand while the main seconds hand continues running; allowing the operator to read an intermediate time or lap time without stopping the main count. Pressing the split pusher again releases the frozen hand, which flies forward to rejoin the main hand.
History
The rattrapante was developed in the 19th century primarily for timing horse races with multiple competitors finishing in rapid succession. It is widely considered by watchmakers to be more mechanically complex than a minute repeater. Patek Philippe's reference 5004 (1994, perpetual calendar rattrapante) and A. Lange & Söhne's Double Split (2004, which extends the split function to split-minutes and split-hours as well as seconds) are the acknowledged peaks of the complication.
How it works
A second chronograph seconds hand rides coaxially on the first, on a separate arbor. Both advance together under normal chronograph operation. Pressing the split pusher activates the rattrapante coupler; a spring or clamp that grips the split-hand arbor and holds it stationary while the main seconds hand continues. Reading the split hand gives the intermediate time. A second press on the split pusher releases the clamp, and the split hand flies forward under spring pressure to catch up with the main hand.
Parts required
Two coaxial seconds-hand arbors on one axis, rattrapante coupling spring or clamp, split pusher and its stem, and a return mechanism to advance the split hand during the catch-up phase
What makes it difficult
Two concentric arbors must rotate independently without binding; a miniaturisation problem with extremely tight tolerances. The coupling spring must hold the split hand precisely frozen without creating any drag on the main seconds hand. The return must be instantaneous: a slow or stuttering catch-up indicates wear or insufficient spring force. Fewer than a handful of manufacturers in the world can produce a reliable rattrapante mechanism in a wristwatch-sized movement.
In the catalog
Related
- Chronograph: A stopwatch complication; start, stop, reset
- Flyback chronograph: Stops, resets, and restarts in a single pusher press
