In 2009, when Patek Philippe presented the caliber CH 29-535 PS, its then latest proprietary chronograph movement based on classic principles (manually wound, column wheel, horizontal clutch), it was already clear that someday, it would be followed by a caliber with the acronym CHR, which stands for CHronographe à Rattrapante, the French term for split-seconds chronograph. That debut took place in 2012: Patek Philippe launched the Ref. 5204 split-seconds chronograph with a perpetual calendar.
With the Ref. 5370, Patek Philippe also extended its range of pure split-seconds chronographs with a two-pusher model, a stopwatch with two pushers for the basic start, stop, reset functions and an additional on/off button in the crown for the split-seconds function. This contrasts against the ultra-thin Ref. 5959 monopusher split-seconds chronograph which has a single consecutive-action pusher for the basic start, stop, reset functions (3-phase column-wheel control) and an additional pusher for the rattrapante hand.
The caliber CHR 29-535 PS movement, developed and crafted in-house, has so far only been built as a version with a perpetual calendar. Now, to the delight of purists, it is available as a pure split seconds chronograph that melds tradition with innovation. Its traditional facet is the underlying concept of a manually wound movement with column-wheel control and a horizontal wheel clutch that remains the benchmark for many friends of mechanical watches.
To preserve this heritage in the 21st century, it was optimized in many respects and endowed with patented innovations that make this caliber the most progressive classic of its genre.
- Clutch wheels with patented tooth profiles boost efficiency in power transmission and reduce wear.
- The mesh depth of the clutch wheels is not adjusted with an eccentric next to the clutch lever; this is done much more precisely and easily with an eccentric column wheel cap at the outermost end of the clutch lever.
- Self-adjusting hammers in jewel bearings simplify the servicing procedure.
- The brake lever that stops the chronograph wheel is directly synchronized with the clutch lever.
- The slotted minute-counter cam coasts the chronograph and split-seconds hands to a stop rather than abruptly blocking them.
These new features of the mechanical chronograph are joined by innovations dedicated exclusively to the rattrapante function:
- When lap times are stopped, a newly designed isolator uncouples the split-seconds wheel from the chronograph wheel to eliminate unwanted friction and prevent a degradation of balance amplitude while the split-seconds hand is immobilized.
- The split-seconds lever that positions a ruby roller between two flat heart cam shoulders keeps the chronograph and split-seconds hands precisely aligned as long as they are superposed.
These mechanisms are not only ingeniously designed but also lavishly finished by hand as befits a Patek Philippe movement. Most steel parts are painstakingly chamfered and their surfaces straight grained; the split-seconds clamps are polished. The magnificent interplay of bright glossy and lustrous silky areas is enhanced with contrasting golden hues and sparkling red bearing jewels, showcasing watchmaking artistry that can be admired through the sapphire-crystal case back. This quality of finissage is expressly mandated by the Patek Philippe Seal, the watch industry's strictest set of directives, as is the extremely high degree of accuracy that only tolerates deviations ranging between +2 and -3 seconds per day.
The CHR 29-535 PS caliber comes in a platinum case of befitting stature. As the movement itself, it is crafted in-house all the way from the original design and the blueprints to the 60-ton cold-forming presses, after which it is deburred, ground, and polished in time-consuming finishing processes. In the end, as is customary for all of the manufacture’s platinum cases, a flawless Top Wesselton diamond is immaculately set in the case band at 6 o’clock.
Model: Split-seconds chronograph Ref. 5370
Caliber CHR 29-535 PS
Manually wound mechanical movement, split-seconds chronograph with two column wheels, horizontal clutch, and instantaneous 30-minute counter, sweep chronograph and split-seconds hands, subsidiary seconds
Dimensions: 29.6 mm
Height: 7.1 mm
Number of parts: 312
Number of jewels: 34
Power reserve: Min. 55 hours, max. 65 hours
Frequency: 28,800 semi-oscillations per hour (4 Hz)
Balance spring: Breguet
Balance spring stud: Adjustable
Functions: Two-position crown:
– Pushed in: To wind the watch
– Pulled out: To set the time
Center hour and minute hands
Sweep chronograph and split-seconds hands
30-minute counter at 3 o'clock
Subsidiary seconds at 9 o'clock
Chronograph start and stop at 2 o'clock
Chronograph reset at 4 o'clock
Split-seconds hand start and stop at 3 o'clock
Patek Philippe Seal
Platinum 950, sapphire-crystal display back and interchangeable solid platinum back, crown with split-seconds pusher, oval chronograph pushers at 2 o'clock (start/stop) and 4 o'clock (reset)
Top Wesselton diamond between the lugs at 6 o’clock
Water resistant to 30 meters (3 bar)
Case dimensions: Diameter: 41 mm
Length (lug to lug): 49.92 mm
Width (3 to 9 o'clock incl. crown): 45.62 mm
Thickness (crystal to display back): 13.56 mm
White gold with genuine black enamel
Applied Breguet numerals in 18K white gold
White printed scales (railway-track minute scale, tachymeter scale calibrated to 1000 meters, subsidiary seconds at 9 o'clock, and 30-minute counter at 3 o'clock)
Hours and minutes: Leaf-shaped hands in 18K white gold with
Subsidiary seconds: Leaf-shaped hand in 18K white gold
Chronograph and split-seconds hands: Sandblasted steel, rhodiumed
30-minute counter: Leaf-shaped hand in 18K white gold
Hand-stitched alligator leather with large square scales, shiny black, platinum 950 fold-over clasp