Patek Philippe

chintu
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A technical question on Caliber 28-520 and 5980/5960

The following technical question would merit an interesting discussion.

Caliber 28-520 used in Patek 5980 and 5960 has a central seconds hand that is used as a timekeeping seconds hand that can be kept permanently running ( even when the chronograph functions are not started).

Here is the problem. Let us assume that the central seconds hand is currently running as a timekeeping seconds hand and is say; at 15 seconds marker.

Patek says that the chronograph can be started without the zero reset . This means the following, When the chrono start pusher is pressed, logically the  running seconds hand will return from 15 to zero and immediately start as a chrono-seconds counter now instantly.

Let the chrono seconds now reach say 25 seconds. Now press the stop. All chrono functions will cease and the chrono seconds hand will rest on 25. ( till this moment in reality the total elapsed seconds are 40 if there was another normal timekeeping seconds hand that was present)

When the reset is pressed, then the central seconds ( which is the chrono seconds) hand should return to 60 ( i.e. zero).

 In reality, a total of 15 + 25 seconds=40 seconds have passed . If the chrono seconds hand is to once again commence its role as a timekeeping seconds hand, then the watch will no longer show accurate time since the seconds hand does not resume at 40  or such other higher elapsed time as would represent the actual seconds that have passed.

 If the chrono had two seconds hands . One for the chrono function and another as a permanently running seconds hand, then the starting and stopping of the chrono will have had no negative effect on the timekeeping function accuracy.

 Am I correct in my above assumptions?

If yes, then both 5980 and 5960 will be inaccurate between 1 and 60 seconds  in respect of the normal time keeping function, for each time the chrono is used.

regds/narsi