Patek Philippe

About the mysterious chronograph hands problem.... (att. Giorgio)

 

Hi all,
some time ago, in a 5960 related thread, Giorgio reported some problems he had with the hands of his 5960.

click here for original thread

Obviously some rumours were around of a mysterious "problem with the hands", but as it's often with rumours, it's almost impossible to understand or even analyze the possible reasons.

While attending the product launch of the new Nautilus line in Geneva I was glad to have the opportunity to discuss this mysterious problem.

I'll try to describe the history of this story, in my oppinion it's exemplary for similar issues happening in the world of micromechanics. An apparently "simple" problem which soon reveals to be to be quite complex - and after the root of the problem is found, it's nothing more than a simple problem again

As I was told some, very few, of the first ref. 5960 owners reported "faulty" hands. The minute hands showed some tiny scratches/marks.
After receiving those pieces back in Geneva, the watchmakers also found the hands scratched and with tiny marks and thaught it was a quality control issue.
As a logical consequence, those watches were serviced and of course received a new set of hands.
To their great surprise (I'm sure that was a rather bad experience) one of those watches was returned after a short time again and exposing similar scratche/marks again, even more heavily this time.

Now the real mytery began - now it was obvious that it couldn't have been a quality control issue again. And also it was more than possible that there was a potentially principal problem.
So the watchmakers at PP started to research the problem. Among all availlable movements and after extremely serious testing - again some very few only experienced the same problem. But still it wasn't easy to see the reasons for this behaviour.

Finally and only with the help of a super high speed camera, the source of the problem was apparent.

Here's a picture of one of the first ref. 5960 photographed during the product launch of this model:

As said, the problem was found through observation in super slow motion - the critical time frame is reported to be 5 milliseconds only!

During resetting, which mechanically can be a quite harsh treatement to the chrono seconds hand, some hands showed a more or less ovbious resonance behaviour.
More precisely those hands not only "vibrated" laterally (as is more or less normal during reset, sometimes even visible to the nake eye)they also moved up/down.
Those three dimensional vibrations of the chrono seconds hand , forced parts closed to the tip of the minute hand/chrono seconds hand to come into contact - and also getting scratched. (As Giorgio showed in one picture the chrono seconds hand of his watch even got bent!)

The solution for this problem was found in a redesign of the seconds hand.

A close look at the new Nautilus chronograph will reveal the solution chosen by PP's watchmakers and engineers:





The attentively observer possibly has found the main difference already. But, in case you didn't see, here are some pointers to the more interesting parts.



Normally hands are made by suppliers, and re designing and manufacturing new parts takes time - in those cases as decribed above time always is a major factor.
Therefore PP decided to manufacture the new hands in house and it should be noted that one reason that something like this is possible is thanks to the today availlable CNC machinery. The new hand is completely milled, compared to the standard process of stamping which is the usual way seriallly produce hands.

I've tried to do a quick sketch of the difference new to old design below:



As you see the new hands (it may also be visible on the pictures above) have three different level in thickness.
This prevents the larger part of the hand to move uncontrollable (specifically up/down). More precisely, the "resonance" of the possible vibrations is changed and any self damaging effects are avoided.

Personally I find this to be a very fascinating story and it shows once again that even simple things can be quite complicated and unpredictable.

Of course I also can understand the disappointement when beeng an owner of such a piece - but it may also explain a bit how difficult it can be to find the reason for such a problem.

Hope the longish story wasn't to boring though

Best regards
Suitbert