Patek Philippe

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

 

the chrono second hand can run continuously and DOUBLE as a second hand because of the lack of friciton in the 28-520 and evenly distributed energy to the chrono modual and time keeping, BUT does not replace or act as the real second hand.  Internally, the seconds, minutes and hours are moving forward regardless of whether the chrono is running or not. 

The chrono second hand would never be able to measure time because the purpose of the chrono is to stop and start so in any chrono, the seconds that count the hours and minutes are seperate, regardless of whether they are displayed on the dial.

I'm not a watch maker nor have I put together or taken apart the movement of a 28-520 but this is just my opinion/assumption.  I hope it helps you chintu.

Bests,

Rob

Thanks very much. 

Hi,

Indeed the 5980 (and 5960) doesn't have a permanent seconds hand. Time is indicated only by hour and minute hands.

Due to the construction of the calibre you can let the chrono engaged permanently if you want, meaning also that you can use the central seconds chrono hand as a "temporary" permanent seconds hands. But that also means the chrono is engaged (no problem with that) and the chrono hour and minute counters are running.

If you use the chrono seconds hand as a seconds hand for the time, you just need to start again the chrono (it's a flyback chrono) if you want to measure an elapsed time with the chrono. The chrono indicators will be immediately reset and the chrono counters will indicate teh measured time without any imprecision.

If you want to use the chrono seconds hand as a seconds hand you just need to start again the chrono when you consider that a new minute of the time is beginning.

That doesn't provoke any imprecision in running, time or chrono measures, just in the position of the seconds hand.

I hope I'm clear.

Cheers

Dje

I did not say that the watch will become inaccurate. I agree that even when the chrono functions are engaged , the time-keeping minutes hand will continue to keep its accurate time, however the seconds hand when reset from chrono-seconds to timekeeping-seconds, will start all over from zero. Thus in my example the actual seconds elapsed in real time and the apparent seconds read-off the timekeeping seconds hand will be incorrect. In my example the real seconds elapsed is 25 seconds but because of the timekeeping seconds hand restarting from zero, the wearer will now read the seconds lapsed as zero when it should actually resume at 25 seconds. Thus if the time  is 10:10:25 in reality, the reset of chrono-seconds to once again become the time keeping seconds will cause the time to now show 10:10:00. This is not welcome at all. Perhaps this is the very reason that no one tries to mix up the chrono-seconds counter with timekeeping-seconds counter ( normal seconds hand).

regds/narsi

If the chrono-seconds hand is left running as a permanent timekeeping-seconds hand, then it would also lead to the chrono-minute  hand and the chrono-hour hand ( in the sub dial at 6' O clock) running continuously.  This leads to the following questions

1. Does this have an effect on the power reserve of 55 hours stated ( is this without the chrono running).

2. What is the impact on the accuracy of time-keeping itself as a result of the chrono-seconds being used as a time-keeping seconds permanently since this will engage the chronograph also.

3. Will the watch perform better when the chrono-seconds is resting ( without it being operated as a chrono or as a permanently running time-keeping seconds) ?

4. What is the risk of mechanical wear and tear to the watch as we are now dealing with a permanently running chrono along with normal timekeeping. I appreciate that the rotor is winding around zirconium ball bearings etc and that very little lubrication is needed. It still does not take away the level of wear and tear on the parts overall if the wearer chooses the option of a permanently running seconds hand.

 

regds. narsi

 

It should have 8 scalings per second as it beats with 28.800 A/h, and not 5.

This is with possibly all (?) Patek chronos.

It looks like a dream chrono, but if you approach your dream closer and pay attention to details, with a clear mind: it showes faults.

BUT: never mind!

A Patek is not soemthing that measures itself with the mundane world ...

"Dreams are my reality, the only kind of real fantasy. Illusions are a common thing ..." Richard Sanderson ( La boom) , ... for Horo ;-)


Regards

Moritz
This message has been edited by COUNT DE MONET on 2011-11-30 12:38:54