History of the Atmos Clock and How it Works......

The following information comes from various LeCoultre catalogues and documents.

In 1928 a Neuchatel engineer called Jean-Leon Reutter built a clock driven quite literally by air. But it took the Jaeger-LeCoultre workshop a few more years to convert this idea into a technical form that could be patented. And to perfect it to such a degree that the Atmos practically achieved perpetual motion. In 1936 production of the Atmos began.

The technical principle is a beguiling one: inside a hermetically sealed capsule is a mixture of gas and liquid (ethyl chloride) which expands as the temperature rises and contracts as it falls, making the capsule move like a concertina. This motion constantly winds the mainspring, a variation in temperature of only one degree in the range between 15 and 30 degrees centigrade being sufficient for two days' operation.

This video shows how an Atmos Bellows works with Atmospheric Temperature changes to wind an Atmos Clock.

You can see that as the temperature drops the bellows contracts, pulling a chain, winding the clock.

For an Atmos Clock to wind itself and work perpetually without any human intervention, the Bellows has to work properly. If the Bellows is not working then the clock will fail to wind and will eventually stop.

The Bellows are filled with Ethyl Chloride, a liquid that boils around room temperatures. As the temperature in a room rises the Ethyl Chloride boils and converts from a liquid to a gas. A gas takes up more volume than a liquid and so this conversion process expands the Bellows. As the room cools the opposite happens, the Ethyl Chloride condenses back from a gas to a liquid. The liquid requires less volume and so the Bellows contract.

If the Bellows are working to factory specifications they only require a 1 degree change in room temperature to power the clock for a further 2 days. The energy stored when the Atmos clock is fully wound can power the clock for around 12 months. There are times when there may not be a change in room temperature to wind the clock and so it is reliant on the stored energy. This energy is stored in the mainspring. It is worth noting that this constant self winding process continues even when an Atmos Clock is locked and / or in storage.

Over decades the Ethyl Chloride can slowly leak to the point where there is not enough left in the Bellows to wind the clock. The Bellows will then either require regassing or replacement. Regassing a Bellows with Ethyl Chloride is a specialist task that most Clock Repairers are unable to complete. Every Atmos Clock that we sell has Bellows that have been checked, refilled by ourselves or replaced as required to ensure that the Atmos Clock works fully to the original manufacturer specifications.

To convert this small amount of energy into motion, everything inside the Atmos naturally has to work as smoothly and quietly as possible. The balance, for example, executes only two torsional oscillations per minute, which is 150 times slower that the pendulum in a conventional clock. So it's not surprising that 60 million Atmos clocks together consume no more energy that one 15-watt light bulb.

All its other parts, too, are not only of the highest precision, but also practically wear-free. An Atmos can therefore expect to enjoy a service life of a good 600 years, although with today's air pollution a service is recommended about every twenty years.

Admirers of advanced technology, however, aren't the only ones who get their money's worth. Connoisseurs of elegant forms, precious materials and traditional craftsmanship, do so as well. Because every Atmos is still made entirely by hand; and with some models a single clock takes a whole month to produce. Not counting the five weeks of trial and adjustment that every Atmos has to undergo.

Only then, were the Jaeger-LeCoultre master watchmakers happy enough with the state of things to confirm it with a signature and allow another Atmos to leave the workshop. After which, many end up in the very best homes, because for decades now the world's most celebrated watch-making country has been presenting its distinguished guests with this masterpiece of Swiss artistry.

The Atmos has had the honour to be associated with great statesmen, royalty, and other renowned people including John F. Kennedy, Sir Winston Churchill, General Charles DeGaulle, and Charlie Chaplin.

How to date an Atmos Clock......

You can contact Jaeger LeCoultre directly to establish the exact production date of your clock. They will charge you a fee of around £290 to do this.

client.relations.europe@jaeger-lecoultre.com

You can however work out the approximate date of your clock by other means.

Firstly identify you clock serial number. This is usually on the top of the clock where you can see it through the glass cover. However on some variation clocks which do not have a glass top you will need to remove the case. Early Atmos II's may have 2 serial numbers (on the top and front movement) and some special edition limited run clocks (eg Prestige) will be on a case plaque.

From the serial number you will be able to roughly determine the decade or production using the table opposite.

If your clock was made after 1950 with a 6 digit serial number you can also use the following calculation to determine its production year...

First 4 digits of the serial number divided by 10 eg

261450 would be 2614 / 10 = 261.4 (ie take the 1st 4 digits and move the decimal point one to the left)

abbreviated serial number x 0.051 + 1954 = year of production

eg 261.4 x 0.051 + 1954 = 1967

Please note that this is not an offical way to calculate the prodcution date and it does not always work but often it does.

Finally, you can also remove the bellows from the rear of the clock. All bellows where inscribed by hand with the date they where made and they where usually fitted to clocks within 3-6 months. This should only be done if you are experienced with maintaining an Atmos clock so it is usually done by an authorised repairer as part of a service ie they will note the bellows production date. However, bellows can fail over time and it is not uncommon for the bellows to be fitted to not be the original bellows. Refurbished bellows from another Atmos maybe dated considerably before or after the clock was made.