Ref. 5204 - Ron DeCorte
"Ref. 5204" - Ron DeCorte
Anticipation can be agonizing, especially when we have a notion of what’s to come. However, calm your nerves, the wait is over! Patek Philippe has rounded out its chronograph collection with the new in-house manual wind, horizontal clutch, split second chronograph with perpetual calendar: Ref. 5204P.
First, lets have a quick look at what makes the Ref. 5204P tick. The caliber CHR 27-70 has been retired as the caliber CHR 29-535Q takes the field. At 32 mm diameter the CHR 29-535Q is 2 mm larger than its predecessor and a bit slimmer in terms of thickness. The Gyromax® balance now oscillates at 4 Hz compared with 2.5 Hz, and the chronograph minute indication is now instantaneous.
Split second chronographs employ two seconds hands, each having its own purpose. During general operating conditions these two hands are in direct unison. Engaging the split function instantly stops the split hand so the intermediate time can be recorded. When released, the split hand will rejoin the chronograph hand in unison. These two hands play a mechanical game called catch up. In order to play this game there is a heart cam, follower lever, and a ruby roller that follows or traces the perimeter of the heart cam. Patek Philippe has addressed these important functions via two new innovations in the new caliber CHR 29-535Q.
Now the fun begins. The Octopus as it was fondly known is now gone. What was it and why has it been retired? The Octopus was part of the isolation system that completely isolates the two chronograph hands when the split seconds hand is employed. With the new patented Swan's Neck isolation system, the split seconds lever is completely isolated from the chronograph wheel heart when the split seconds mechanism is engaged. This allows it to turn without friction or irregular drag, like other split seconds chronographs. Retiring the “Octopus” was a simple matter: the Octopus was complex and difficult to adjust by the watchmakers.
Meet the Swan’s Neck isolation system. Instead of eight arms, each requiring individual adjustment, there is only one arm and spring. Indeed the isolation system is a horizontal clutch mechanism. An isolation wheel “A” rotates in synchronization with the split seconds hand. When the split seconds is activated two things happen in a very precise order. Firstly, the split hand is instantly stopped via two clamping arms “B” while simultaneously the isolation lever “C” engages the isolation wheel “A” advancing it about 30 degrees which via a protruding pin disengages the follower cam arm “D”. Isolation of the still-rotating chronograph hand and the split seconds hand is accomplished. It is imperative that these two functions happen harmoniously, otherwise the split function will not be accurate.
When the split function is released the split hand must re-join the chronograph hand in perfect unison. Firstly, the isolation system must disengage. Isolation wheel “A” releases its hold on the follower cam-arm “B” and the two clamping arms “D” release the split hand. Secondly, the follower cam-arm must return the split hand to its neutral position as shown in detail “E”.
Returning the split hand to 'perfect' unison (realignment) has always been a tricky proposition. The comparative proportions of the split seconds heart cam, follower arm and ruby roller must be very small, especially when contained within a wristwatch. Hence the split hand has traditionally been a bit narrower than the chronograph hand to hide any discrepancy in alignment.
In order to eliminate any possible alignment discrepancy Patek Philippe has completely redesigned the split seconds heart cam, and follower arm. The heart cam now has broader shoulders and the follower arm has a totally different shaped foot to rest on these shoulders. Of course a ruby roller is still employed to follow the heart cam to its neutral point, but instead of the roller being totally responsible for perfect alignment of the split hand, the flanks on either side of the roller rest firmly on the heart cam shoulders. This assures perfect realignment every time.
The topic of return-to-zero also falls under the description of realignment. In order for any chronograph to be completely accurate, all functions and hands must start at a zero mark. Returning to this zero mark after being in function has been an issue for watchmakers and the user alike. The answer is now at hand. They are called hammers but look more like two feet, which in conjunction with their associated heart cams bring the chronograph back to zero.
Traditionally, these two hammers where made from a single piece of steel. This construction technique has always presented a problem. If one of the hammers sits a bit heavy on its heart cam the other hammer will sit too lightly on its cam allowing misalignment with the zero markers. Articulating hammers that act as one until the last moment was the Patek Philippe solution. Think of it as your legs. They are joined at the hips and work in unison until you encounter an uneven surface such as a step. At that point they can move independently and adjust their respective movements and motions accordingly.

To produce a new complicated movement that respects its heritage as well as bringing innovations is not an easy task. After years of development the Patek Philippe Ref. 5204P is a classic example of visual understatement with its mechanical innovations quietly concealed within its platinum case.