Our discussion of KIF, Breguet Overcoil, Parachrom, Parallax and other Rolex patents and technologies illustrates how there is no one specific component that insures Rolex accuracy but rather a mixture of components that work together. Another example of Rolex’s belief in building it right rather than building it easy is in the design and function of the Rolex balance and regulation system.
As we discussed in previous posts, the Rolex balance wheel is the mechanical heartbeat of the watch and keeping its oscillations] consistent are key to accurate timekeeping. The balance wheel contains the Parachrom balance spring, and held in place by jewels and Parachrom shock springs. The balance wheel is held in place by a full balance bridge spanning both sides of the balance wheel -a feature not followed by many brands who utilize a balance-cock or spur spanning only half the balance wheel. A full balance bridge holds the balance wheel steady, similar to holding the main center post of camping tent -the more ropes spanning the main tent post the more steady the tent is. Additionally, Rolex utilizes two star-nuts that secure the balance bridge. Unlike a balance-cock that is held in place by one screw, the star nuts are adjustable compensating for end-shake in the balance staff. Old time watchmakers used to account for end-shake by bending the balance-cock, but not so in a Rolex and yet another example of Rolex’s ethos of designing it right rather than designing it easy.
Another departure from traditional Swiss watch design is that the Rolex balance is “free sprung” versus being “regulated”. Regulated balances mechanism are typically found in conventional Swiss ETA movements whereby regulation is with a sliding spring inhibitor that straddles the balance spring making it effectively longer or shorter. Changing the spring length effectively makes the balance wheel travel at a wider or narrower arch. Rolex (and Patek Philippe) utilizes nothing to inhibit the balance wheel. The balance wheel oscillates freely and thus “free-sprung.” A free-sprung balance combined with a Breguet overcoil allows the balance spring to breath naturally without anything mechanical to impede it.
For regulating a free-sprung balance, Rolex utilizes two-pair of weighted nuts mounted inside the balance wheel to adjust the balance wheel’s inertia. Other companies who use a free-spring design mount the screws in the outside of the balance wheel, but Rolex mounts Microstella screws on the inside to make it easier to adjust and the balance wheel can be larger in diameter making it less sensitive to changes in inertia and g-forces when worn. Microstella screws inside the balance wheel also make the balance wheel more aerodynamic because there is less turbulence caused by the screws when they whip through the air at 28,000 oscillations per hour. Although there is no method for performing DIY adjustments like with regulated balances, Rolex’s free sprung balance wheel is extremely precise when adjusted by a Rolex certified watchmaker who possesses the tools, the timing machines, experience, and the patience for making precise adjustments.
The Rolex free sprung balance and Microstella adjusting screws are just some of the technologies that set Rolex apart from the rest of the Swiss watch industry.
– Sheldon Smith