Minute and hour hands only starting up after a few minutes?!

[Shadaar]

Hi all,

I'm currently working on a Omega Seamaster Cosmic 2000 166.128. Cleaning, lubrication and reassembly all done. All parts inspected and no broken/worn teeth on the gears. On the Timegrapher the movement runs excellent. Around 0 to -4 sec/d depending on position and amplitude between 245 and 275. Beat error 0.1 to 0.2. Lift angle correct at 52 degrees. I did multiple test rounds to make sure it is all good. 

After testing I started wearing the watch and then noticed a weird phenomenon that I have not experienced before. After setting the time and pushing the crown back in, the seconds hand starts running Immediatly and correctly. I timed this for 20 mins with a stopwatch to make sure and still perfectly on time after this period, what you would expect from the reading on the Timegrapher. But, the minute hand (and I believe the hour hand as well) only start moving around 5 to 10 mins later. I checked it under a microscope and you can clearly see the minute hand does nothing and then suddenly starts up. After that it seems to run on time again, but ofcourse the watch is running 5-10 mins behind at that point.

 

I have tested if the hands run freely and this is the case. It also displayes the issue in different postitions of the hands, so I think this can be ruled out.

 

I then tried to read up on this problem and I believe I found two possible issues that could be responsible:

1. Minute hand is (too) loose.

2. Cannon pinion is too loose.

 

Before trying to fix either of these and due to the werid behaviour of starting later, but then running ok, I hope someone here knows what could cause this specific issue. If it's likely either one of the above issues or something else?

 

Hope someone can help!

 

Regards, SJ

[rjenkinsgb]

With both hour and minute hands affected, I'd first look at the cannon pinion.

[Shadaar]

Thanks for the reply! In your opinion, could a loose cannon pinion explain the late startup of the hands? I can't explain why they don't slip continuously.

[Shadaar]

Just found another piece of the puzzle. I compared the friction I felt when setting the time with another Cosmic 2000, and there is a BIG difference. That one takes a lot more ' force' to turn the hands. This also points to the cannion pinnion being loose, so I will attack that first.

 

Any good tips how to do this job without the special tool for a staking set? I don't own that (yet)... 

 

[Nucejoe]

 Dull a used nail clipper to make your own tool as shown bellow. 

Control over tightening is regulated by micrometer action of the two screws.

Good luck

[watchweasol]

Hi. I made a similar device to the one Joe pictured . Works ok.

[Nucejoe]

 Make sure to dull the  nail clipper's cutting edge,       (  see photo )

 I cut two  half holes on cutting edges, so to secure the canon pinion in place,  Magnify the photo to see complete  hole the two half make when joined. 

Then forum member canthus  added screws to the my design, considerably improving  it.

Here is a photo of the original one I made.

 

So,  go with canthus version, and file the two half holes on cutting edge, dull cutting edges. You furthure improve the design.

You get micrometer action by tightening the only screw on my gadget buy no preset limit on how much you tighten.  

Good luck 

 

[Shadaar]

Thanks all for the great advice and the pictures!

 

I did the job yesterday and it worked out great. There was already a small indent on the cannon pinion, which made it easier to position the nail clipper. For now inserted a screw driver of the correct diameter to make sure I couldn't tighten it too much. The hands are no longer slipping and the watch is running perfectly!

 

Another new job learned in the watchmaking journey

 

Thanks again everyone!