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The Birth of Patek Philippe’s First Direct Seconds Movement: Caliber 27SC – Part 2
In 1939, Patek Philippe sought to incorporate a central seconds hand into their watches, a feature not common at the time. To achieve this, they collaborated with Victorin Piguet to develop an indirect center seconds mechanism, resulting in the caliber 12-120 SC (seconde centrale).
This movement was utilized in models such as the references 96, 565, and 570.
The Patek Philippe caliber 12-120 SC with indirect center seconds, despite its innovative approach to integrating a central seconds hand, it presented several technical limitations.
The primary drawback stemmed from the indirect drive mechanism, which relied on an additional secondary gear train to transfer motion from the fourth wheel (which traditionally drives the small seconds in a standard movement) to the centrally positioned seconds hand.
This intermediate transmission introduced increased friction and energy loss making the system less efficient compared to a direct-drive seconds mechanism.
This is also known as “parasitic drag”, caused by the extra gear required to transmit motion to the center seconds hand. This additional gearing absorbed part of the energy intended for the escapement, potentially affecting amplitude and overall rate stability.
The higher friction and increased number of moving parts meant that lubrication was more critical, and any degradation of lubricants over time could lead to erratic seconds hand motion, known as fluttering or stuttering.
Unlike a direct-drive system where the seconds hand receives constant, uninterrupted power from the fourth wheel, the indirect mechanism introduced a degree of play in the gear train, which sometimes caused an uneven sweep of the seconds hand.
It is also important to note that, given the exceptional quality of these Patek Philippe movements, the issue is more of a theoretical possibility rather than a frequent occurrence.
Another inherent weakness of the 12-120 SC was reduced shock resistance.
Because the additional gears were smaller and less robust than the primary gear train components, they were more susceptible to wear, misalignment, and displacement due to external shocks.
Additionally, the power transfer inefficiencies meant that even a well-adjusted caliber 12-120 SC could struggle with long-term consistency in precision, as minor variations in friction could influence the rate of the movement.
These challenges ultimately led to the pursuit of a direct center seconds solution, which Patek Philippe achieved with the development of the caliber 27 SC, eliminating the inefficiencies of indirect transmission and providing a more reliable, energy-efficient, and precise mechanism in 1949 it replaced the 12-120 SC.
This caliber represented a significant technical evolution from caliber 12-120 SC, primarily due to its direct center seconds drive and improved energy efficiency.
Measuring 27mm in diameter, this manual-winding movement has an advanced gear train architecture that eliminated the inefficiencies of the indirect seconds transmission found in the 12-120 SC
Unlike its predecessor, which relied on a secondary gear train to transfer motion from the fourth wheel to the central seconds hand, the 27SC was designed with a direct-drive seconds system.
This meant that the fourth wheel was repositioned in the center of the movement, directly engaging the escapement wheel without the need for an auxiliary transmission wheel. By eliminating unnecessary gearing, this construction reduced energy loss and friction, allowing for a more stable amplitude and improved chronometric performance.
The bridge layout and gear positioning were also revised for enhanced shock resistance and servicing accessibility as one shock absorber leaf-spring was placed over the center seconds, one over the balance wheel. (and one below). Additionally, the movement incorporated refinements in lubrication channels, ensuring more efficient oil retention on high-friction components such as the escapement and gear pivots. From a practical standpoint, the direct-drive center seconds also eliminated the stuttering effect occasionally observed in indirect seconds systems, as there was no intermediate gear that could introduce backlash or erratic motion.
This resulted in a smoother, uninterrupted sweep of the seconds hand, improving both aesthetic appeal and timekeeping precision. The caliber 27SC was a milestone in Patek Philippe’s movement evolution, setting the foundation for modern direct center seconds calibers while reflecting the brand’s dedication to engineering efficiency, precision, and reliability with improved timekeepingso that it remained in production until 1970. The caliber 27 SC’s implementation in various models, including the Calatrava series, solidified its place in horological history. Its development marked a significant milestone in Patek Philippe’s journey toward technical mastery and set a standard for future movement innovations.
