It was what was going on under the hood that wrote the headlines. Rolex’s relationship with Zenith ended with the arrival of the Cal. 4130; a barebones, stripped back movement entirely of Rolex’s own creation—and one now recognized as possibly the finest mechanical chronograph caliber ever made.
Taking their love of minimalist efficiency to new heights, the Cal. 4130 is made up of just 201 separate parts, a 60% drop on the El Primero, giving it the fewest components of just about any modern chronograph movement.
To achieve it has taken a huge amount of creativity. While the Daytona’s exterior may retain a familiar look, the differences between the old and new calibers are legion. Elements such as the minute and hour stopwatch functions, controlled by two individual mechanisms in the Zenith movement, have been combined into a single module on the Cal. 4130. In doing so, it has freed up space for a larger mainspring, giving an uprated power reserve from 50 to 72 hours. It also means it can be adjusted with just one screw as opposed to five. In fact, in the entire unit, Rolex has only needed to use 12 screws rather than 40.
Additionally, the ref. 116520 received new cutting-edge materials, with the antimagnetic Parachrom hairspring earning its debut. A niobium and zirconium alloy, it is impervious to temperature variations and offers up to 10 times the shock resistance of standard hairsprings. In 2005, it was upgraded again with a thicker oxide coating to protect its surface, one which reacts with the air and turns the distinctive color that saw it renamed the Parachrom Bleu.
Ceramic ball bearings were used for the first time in the self-winding system too, seeing a 68% increase in winding efficiency.
But the most revolutionary aspect came with Rolex’s use of a vertical clutch. The El Primero, along with just about every other mechanical chronograph movement, uses a horizontal coupling system to control the starts and stops of its stopwatch functions. With the Cal. 4130, Rolex arranged a pair of discs one on top of the other, running in a constant mesh with the drive train. Engaging and disengaging them with a clutch eliminates ‘backlash’, the tendency with horizontal systems for the chronograph hands to judder as they fight to gain purchase, giving a smoother and more exacting performance.
It also means the stopwatch can be run for longer without it affecting the accuracy of the watch’s timekeeping, and it has the rare advantage of being removable, meaning it can be serviced to ensure its continued reliability.
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