Please give me advise can I leave the second hand running on my 3510.50

 

Why not, you could be timing a day....

 

There is no reason that on a properly serviced movement that you can't leave the chrono running at all times.

If you consider the movement train from the mainspring to the escape wheel, those wheels/pinions and pivots are under torque from the mainspring at all times, and as long as the watch is running, which it does 24 hours a day, these parts are under stress.

Now compare the movement train to the chrono module, in the chrono module there is no stress being applied from the mainspring, only a rotational turning force is applied to the chono module wheels/pinions and pivots, and as long as they are clean and properly lubricated, there should not be any wear.

I just completed a servicing on this Cal 3220 movement, including of course complete teardown of the Dubois Duprez chrono module, and as proof of the light load on the pivots, only 9010 and 9020 oils are used throughout, the same oil for the 4th and escape and balance pivots on the base movement.

www.roberthoran.eu

 

Yes

 

Good evening Rob

Out of interest, and bearing in mind that I have never looked at this calibre, I've read before that a horizontally coupled chronograph (such as an 86x series) should not be run all the time but a vertically coupled one such as my Seiko UFO (I forget the calibre) may be run continuously.

I've taken that to be because of the way the drive is transmitted. Here's a picture of my 865 Chronostop that I serviced earlier this year and I'm talking about the transmission through the coupling wheel on the fourth wheel to the idler and then to the wheel that the chrono second hand is mounted on (the one with the heart for those who are not as aware of these details as Rob). It's the last wheel with it's very small teeth that I'm thinking might wear.



Genuinely, just interested to hear if this Dubois module works in this way and what you think about leaving an 86x running all the time.

Cheers, Chris

 

Hello Chris,

The short answer would be that any component can/will wear out if it's exposed to the right conditions: abrasives, friction, torque, lack of lubrication, etc.

But to answer your question, what do I think about running a horizontal chrono at all times? If you want it running, do it...

I have serviced dozens and dozens of horizontal coupled chrono's over the years, and not one of them showed any signs of wear on the teeth. Some had broken and damaged teeth, but that was a result of botched work or mishandling, not wear from running.

These wheels are under no force or torque, they simply rotate and only have to overcome the weak friction in the pivots, and slightly more friction of the wheel teeth engagement.

If you look at the photo below, you can see that the 4th wheel drive wheel is permanently engaged with the transmission wheel and as long as the movement is running, these two "V" toothed wheel spin and turn together.



If anything was going to wear I would expect these two gear to be the ones, but they don't. So why should the chrono second wheel wear out, simply due to the smaller size of the teeth? I am not convinced and my bench experience confirms it.

The biggest problem I see with all chrono's is the mis-adjustment of the eccentric screws for the depthing etc.

The chrono seconds hand can be "jumpy" due to the slow beat, and the designed backlash between the gears, and the fact that there is no force going through the chrono seconds gear. I see many movements where the required depths of 2/3 and 1/3 engagement is wrong and adjusted to 3/3 and 3/3, all in the aim of curing the "jumpy" hand. This is done by watchmakers (I use that term loosely) who don't understand the principles behind the design. I would expect that this could possibly cause wear over time because of the increased friction from to deep a depth and dirt between the teeth.

No doubt someone will disagree with my experience, and that's fine, what I am sharing is what I have seen during servicing, and what my horological training and library tells me, there is nothing anywhere that I can find suggesting or recommending not running a horizontal coupled chrono. It has to be maintained and serviced correctly, and the chrono seconds wheel should always be cleaned with a glass fibre brush, and of course the eccentrics have to be set right.

Hope this helps...

Rob

www.roberthoran.eu

 

I don't believe this is true, can you provide confirmation/proof of these statements? Not only is it very costly and wasteful to throw away a complete module, there isn't an infinite supply of modules available. If this was the case, why bother servicing anything at all? Throw everything away and replace it with new.

Also, why would Omega go to the trouble of producing Technical Guide TG-19-024E, Calibre 3220, "Assembly - Chronograph Module" including oiling, adjusting, parts list, testing, etc, if they were throwing the modules in the trash? Doesn't make a lot of sense to produce an overhaul document, keep spares, produce special tooling, etc only to dump the modules in the garbage.

I wanted to post the Technical Guide but Photobucket is down at the moment, when it's up I will update.

 

Thanks for the link dsio. I guess the Omega approach varies by country.

Photobucket is up today, so here is what I was trying to show yesterday.

I do all the work in-house. I love the technical challenge that servicing chrono's presents, this particular module has a number of variations and is used in many different watches over a long time period, and being able to service it is a benefit to my customers.

Here is a photo of a recent service with the module and movement disassembled and ready for cleaning. Not much to it once it's in pieces...



And here's the Omega overhaul instructions.

 

Hello Rob,
I can assure you that Omega approach does not vary by country. I have possibly serviced hundreds of these chronographs since the very late Eighties and I have also acted as an instructor at SGRIT for a short while.
The chronographs modules are intended to be routinely disassembled and serviced.
By the way, as you are certainly aware, these modular are excellent calibers and, if properly serviced, run smoothly and very accurately.
What you read on fora about them are mostly urban legends.
Regards,
Maurice

 

Thanks Rob.

Yes, the eccentric adjustments are critical as you say and with the few chrono calibres I've worked on, one was screwed in tight with almost 100% engagement. When I corrected that, it still ran fine so perhaps the previous person to have it open didn't have sufficient magnification? Luckily, all teeth were fine but I can see how having too little or too much engagement could cause damage.

I take your point about not seeing damage in this area and will bear it in mind.

Regards, Chris

 

Hello Maurice,

Thank you for the follow on details and your experince.

I agree, the modules are very well made and to high quality, as good or better than the quality of the movement that is attached to it.

I really enjoy working on them, quality always makes the job easier, do the work to the standard and you are rewarded with a find running module.

@ChrisN

Understood, ecentrics are critical as is a good loup or better yet a microscope. I find that it's easier to judge depth with the wheels stopped, then of course put it in motion and monitor engagement for the complete rotation of each wheel to ensure they are not out of round.

As a follow up I did a quick check of some references: Ensemble O'Graph manuals, Complicated watches deCarle, DLC, WOSTEP manual, and didn't find anything other than what I already mentioned.

All the best
Rob