Most of you don't recall the drama I had with a US clockmaker re my 1960s Atmos clock. You can find by search if you like but suffice to say it would not run properly once returned(10minutes/day fast). Basically it had been manually overwound when attempting to preset the mainspring for normal operation by the bellows.

Since it runs on 'air' the issue could take months or up to a year to resolve itself.

(Fun Fact: the Atmos clock runs on so little energy, 4 MILLION Atmos clocks would run on 1watt of energy.)

So I have been tweaking it for the last 2 years (everything about adjusting an atmos takes weeks to see results).

Now. Finally. It is running well. VERY well. The average for the last 3 months is -1.57secs/DAY

A 57 year old clock. Wow.

I was told they can be extremely accurate but take a lot of care to do so.

I'm excited to finally see it spot on so wanted to share the success.

Hooray!

Pic below of Atmos clock as it sits, with uber rare JLC wall mount.

 

Wonderful Clock, well done on fine tuning it so accurately.

 

Well done! I've always wanted to get one of these.

 

A month and a half later, it is better still!

From mid July to mid August, the accuracy avgd 0.6 seconds/day.

The last two weeks have been 0.15 seconds/day.

Yes, it lost only 2 seconds in TWO WEEKS.

WOW.

But people say these clocks are temperamental. THEY ARE.

It took 2 YEARS for me to get this fine of an accuracy, as it takes several days to weeks to stabilize after each adjustment.

Not bad for a clock built in 1962.

 

That's very cool.

 

@Wryfox what instruments/method are you using to time the clock?

 

I really like the capricious nature of those Watches, I missed a nice one last year for a great price.

 

I use an atomic clock app on my smartphone. I hold it up by the clock, and the unique nature of the clock being 120bph (2/minute) allows me to precisely measure the click of each half minute hand movement. The minute hand actually starts to move very slowly for several seconds and then clicks into place so it's easy to time when this happens.

So I have the time standard app up in front of the clock and when the minute hand clicks, I glance at the app time and there it is. Subtract clock time from real time, then subtract time difference from prior week measurement. Then divide by 7 for s/d.

I only measure once a week, at the same time of day.

I've got this process down now, having done it for two years.

 

My wife bought me the exact Atmos model the OP has, bought in 1973 where it had been in the small town South Dakota jewelry store's stock for many years. (The bellows are scratch marked 5-24-61 and still measure as 'good'. Some bellows will last a long, long time, others will fail after a relatively few years, it just depends if the bellows is completely air tight to keep the gas from escaping). She paid $125 for it which was the original MSRP cost when it was made, they never increased the price while they had it in stock. I just went through a very long ordeal getting it overhauled by one of the best Atmos guys in the business, but it took 28 months to get it done. (A crazy amount of time but it is what it is, he had some emotional issues with Donald Trump's election which caused him severe problems focusing on the repair business. True.)

Got it back in mid-March, the regulator was set in the 'neutral' position. Over the next 2 1/2 months it was running about 30 seconds per week fast so I moved the regulator one-half mark to the 'slow' side. Over the last 12 weeks it has gained 23 seconds, about 2 sec/wk, 0.25 sec/day. I don't get too fussed over accuracy on this clock, with a period of 30 seconds on the balance it is very challenging to get a real accurate rate, and the rate will drift a bit depending on temperature and state of wind. One thing is imperative, they must be on a shelf that is completely steady, they do not like being bumped around. My last overhaul (by the same repairer) lasted 12 years and he said it should have done better than that, so hopefully this one will last longer. These are interesting clocks, the older ones generally considered to have better movements than the newer ones.

 

I bought mine for $250 at an estate sale 2 yrs ago. Sent it off to a hack who claimed expertise with a fancy website etc, but it was actually his father who was the expert. Lesson learned. Got my money back after two months and had to fix it myself. Internet info is quite thin but the revelation for me was a technical paper written a few years ago on the technology of this clock. That one document equaled all the combined information on the internet.

If your a technical geek like me, the paper is at this link:
https://tigerprints.clemson.edu/mecheng_pubs/8/

Anyway, it is very true that temp and stable placement are CRITICAL to a well running Atmos. You'll never see one running on time at a JLC store or show. The conditions are too variable.

I will say this, the JLC store reps love this clock. It's sort of the faberge egg of their business. 2017 Retail was $8,100 new. No kidding. The Swiss govt still gives these out to visiting dignitaries.

 

Our model is actually quite rare(Model 5903 w/528-6 movement). It is larger and heavier than the std model. The only downside is the lift off case vs the front door version used in the other 99% of Atmos clocks.

To be honest am so relieved it is now so accurate because I no longer have to lift the heavy glass case up and off and then back on. If you don't do it VERY VERY slowly and carefully, you upset the balance and time is affected until it restabilizes.

 

Thanks for that link, will take a bit of reading through but looks a very good resource
Cheers
tim

 

That wall mount gives me anxiety! I have an Atmos clock that's approximately the same age I am. My grandfather gave it to my grandmother as a anniversary present almost 40 years ago.

 

Update: Average for the last 4 months is -0.25 seconds/day. Again, a 57yr old clock. Amazing.

Now that the season is changing, its starting to be a bit cooler and drier so we'll see if it can maintain its stability. Fluctuations in room temperature keep it wound, but changes in absolute temperature affect the timekeeping ever so slightly. We'll see how much!

 

I just checked mine........138 days since I last set the time, avg rate is +1.6 sec/day. Close enough for me, I don't fool with adjusting the rate since I have it in a bookcase and I can't take the top off without stopping it and taking it down from the shelf. I might stop it for an hour next month when DST ends and start a new run. Still running with the same bellows marked May 1961......58 years old. It is quite remarkable that the technology for these clocks dates from the 1920's and that they can be made to run within pretty close tolerances with a beat rate of only 120/hr vs a wristwatch at 21,600, 28,800 or even 36,000 per hour and relying on slight changes in air temperature to keep the mainspring wound.

 

I just saw one of these in an antique shop in northern California for a few hundred dollars. I thought 'cool clock, I should get one of these some day.' Now I'm really regretting not snapping it up when I had a chance! May I ask how much servicing these typically costs?

 

Congratulations! to OP for successfully tuning the Atmos to such accuracy. I have several Atmos but none is exhibiting such fine time keeping. But that is not to say I am unhappy with them. I find the routine of making manual adjustment (for ~ 5 minutes drift) every few weeks kind of therapeutic . Feels nice to interact with the clock and reflect on the passing of time...

Here’s my Atmos bought a long, long time ago...

 

For worthy independent clock makers(there are maybe 6 in the country who can do a decent job), 600-800 plus parts. JLC has restricted parts for independents so most scavenge off trade ins. Parts are expensive. I think the basic JLC factory service is 1200. For comparison, a new Atmos is $8k.

Thankfully a service is rarely needed in normal operation due to the very slow movement. It's mostly needed due to contamination so you want to keep it in a very clean environment.

It was actually viewed as a mantle clock, but do not put it there as that is typically a drafty and dirty location.

Most used Atmos need a service due to people treating them like a normal clock, not a precision instrument.

Also be aware servicing can take months as the regulation process is very time consuming.

But, as you can see, a well running Atmos is a great source of pride, satisfaction, and beauty.

 

I see you have a lift off cover as well. You have to do this VERY carefully as any *minute* bumping of the movement or case while lifting off the cover can interrupt accuracy for several weeks. This *could* be the reason you are adjusting so often. Lift off very very slowly until you clear the movement, and the same replacing it. Trust me.

Otherwise, you can easily make a small adjustment with the lever on top, to the right for speeding up, to the left for slowing down. Each graduation *should be* 10 seconds/day, but my experience has shown it is quite variable. For ~5 minutes/month, start with half graduation, wait 3 weeks to stabilize THEN measure accuracy from that point forward. You will chase your tail if you check accuracy any sooner.

 

Thank you for the advice. You're probably right that I may be causing the fluctuation by the way i lift off the cover as I manually adjust it.
I will be perfectly happy to make no adjustment and let it go on. and on ..... however, it has almost become a habit, that I love, that I adjust it each time I notice it is going out of sync with the actual time. I guess interacting with mechanical timepieces is one of the attraction that draws me to collecting them. Thanks again for the good advice, I should pay heed to it.

By the way, I notice that the dial of my Atmos shows "LeCoultre" while that of Perseus is "ATMOS" and yours is unmarked. Is there any significance here?