Cal 1040 Challenge (Picture Heavy)

As I work my way through my project list, I came to the Cal 1040 which has been accused of being Omega's most complicated chronograph and wasn't made for long. It is certainly the most complicated watch I have yet serviced.

The front and back of the dial:

... and what it looks like from the dial side

With the date ring removed

This is where I encountered the first problem. The screw in the middle of the small wheel, next to the day/night indicator, was broken off and had been glued back on. This struck me as strange because it is not expensive to replace a screw. The more eagle-eyed will see the end of the screw, still in the plate in this next photo that also shows the complicated date change mechanism.

It was seized solid and nothing I could do would shift it. Luckily, a used plate came up on eBay and with the very generous help of a forum member in the US, I was able to get hold of it. This is an obsolete part so it could have been catastrophic. So, that's a new screw to order.

At least I'm through to the dial side of the chronograph mechanism.

Here it is with the operating mechanism removed

We'll come back to this later because the central of the three copper coloured parts was stuck to the plate. This is where I made the mistake of thinking it was a screw holding it down where it is actually an eccentric and it freed up as i was trying to unscrew it.

Now we can start on the main chronograph

A lot of this looks familiar if you know the 861.

Here is a picture of the underside of the auto winder bridge

The chronograph starts to come apart

With the chronograph removed, the train bridge is next

This was where I encountered another broken screw but fortunately, this one came out without any trouble.

The underside of the bridge


All that is left is the train


As you can see, there is no shortage of parts


Re-assembly is, of course, the opposite of the dis-assembly.

The basic watch, back up and running - well it wasn't quite as simple as that. I ended up chasing my tail as the amplitude was originally very low and as I adjusted one jewel, it led to the need to adjust another.... and so on. Still, I got there in the end.

Just like the 861, you have to assemble the hour recorded to get the watch running because the runner is driven directly by the barrel assembly and the bridge for the runner supports the barrel arbour.


So onto the chronograph. This side went together without any trouble:


You'll remember that I tried unscrewing that eccentric so let's have a look at how the mechanism for locking the sweep minute recorder works:

When the chronograph is not running, the minute recording driver "D" is locked in position by the two clamps "A". Starting the chronograph, a lever pulls on the eccentric "C" mounted on the Valet for Minute Recorder Clamp "B", moving it downwards and forcing the clamps apart, thus allowing the minute recorder to rotate. Stopping the chronograph moves the valet back upwards, letting the clamps back in against the runner. Now, here is the clever bit; when you push the reset, the runner has to be free to move so the clamps are forced apart just before the reset hammer strikes the heart mounted on the runner. That was a real pain to adjust just right but needless to say, I got there in the end......



..... well nearly.

When I had put the dial back on, last weekend, I discovered that the pipe on the minute recording hand was split but a replacement hand was easy to get and yesterday, I rebuilt the stack of hands and finished the job.


The last thing is to put the oscillating weight back on.


So there we have it, the over engineered, expensive to make and complicated to maintain, Omega Cal 1040.

It is little wonder that they didn't make it for long and replaced it with the 1045, using the DD module mounted on a plastic plate.

Having said that, I love the movement and have really enjoyed the journey - frustrating but hugely rewarding.

Impressive number of parts there, Stewart. I'd like one of these as they're a heck of a lot of watch but, I keep passing on them due to the movement complexity so, nice to know you got there in the end. This makes the ETA 6498 that I've got apart at the moment look almost trivial.

Cheers, Chris

Fascinating stuff. Well done! 👍

Very impressive work.

Amazing to see what you've been up to behind those net curtains of yours😉

Interesting thread, I find the complexity fascinating.

I'm sure I've read about watchmakers dissolving stubborn stuck screws - was that not an option here?

I agree. While I am certainly a fan of cal. 1045, I really love cal. 1040 and find it to be the more interesting of the two. Of course it was the first Omega self-winding chronograph and was more expensive to build and maintain, but for me the design element is equally important. The asymmetrical dial layout of the 1040 is very "of its time" and as easily recognizable on the wrist as any movement, maybe ever. Also, Omega was a little more experimental with cal. 1040 and put it in a wider array of cases and with more colorful dial variants than 1045, which was almost only found on black-dialed Speedmasters.

There is a thoughtful design feature associated with the 24 hour indicator, especially for the watchmaker. If you look at the fourth photo, you will see a vertical line on the date indicator guard, just above the 24 hour indicator. As the 24 hour indicator has to be mounted before the dial is replaced it shows where to set the indicator for midnight, You wind the crown (in hand setting mode) until the date clicks over - this indicates that it is midnight - and then press on the indicator. Replace the dial, put the hands on at 12:00 and it is ready to go.

Impressive post... Thanks for your work. 👍

What Al describes was exactly the problem. The thread, into which the offending screw fits is a steel tube pressed into the plate.