clock & barometer repairs
01277 658800   Billericay


Atmos bellows refill & repair

Atmos clocks by Jaeger LeCoultre (Image 1) represent the highest standard of horological engineering; so much so that service intervals can be as long as 25 years. Because these clocks run so slowly (120 beats per hour), wear is minimal and very few parts require lubrication, so pivot holes do not clog up as quickly. Hence, servicing is often restricted to a routine strip and clean of the movement and mainspring; it is not usually necessary to remove the balance unless you suspect the suspension id damaged by mishandling; such is the importance of locking the balance before moving the clock. Otherwise, the only parts replaced are normally cosmetic (glass, for example).

One vital part that can fail after many years, however, is the bellows, which is housed inside the large container or "motor" (Image 2) on the back of clocks after the ATMOS I (which was virtually a prototype). Made from thin folded stainless steel and brass, the bellows contains chloroethane (ethyl chloride), which has a low boiling point (12.3C) so the bellows expand and contract with changes in temperature. A heavy compression spring inside the bellows helps control the thermal range of expansion so variations from 16C to 24C continually wind the mainspring (Image 3). The mainspring is designed to run the clock for up to 12 months so failure of the bellows will not result in the instant failure of the clock; in fact, it might be another year before the clock stops although it will begin to lose time long before that.

A good bellows can be recharged but it's vital to use the right amount of chloroethane; too much and the bellows will be overstressed when expanded and/or remain expanded at cooler room temperatures; too little and it might not expand at all against the force or the compression spring. Both mean that there will be too little lateral movement so the clock will not wind itself.

But recharging alone is not always enough; bellows sometimes fail because the gas escapes, and repairing a leakage poses additional challenges. Just tracing the leak can bel difficult since air pressure and underwater testing simply will not reveal slow or tiny leaks. Repairing a leak has added problems. A failure of the joint between the brass and stainless steel parts (like the fill pipe) is usually repairable by re-soldering. Chloroethane contains a corrosive halogen but the self healing qualities of stainless steel when exposed to air may mean that there is no discernible reason for a collapsed bellows when air-pressure tested. Stress fractures, corrosion pitting and failure of the welded seam in the side of the bellows will often be beyond a solder repair and many a bellows has been declared unrepairable for that reason. I am currently working on a solderless solution but it's not yet reliable and needs further work so if you have an "unrepairable" bellows, please feel free to donate it to help me with further trials.

So why bother to repair at all? Well a new bellows would probably cost £500 depending on the model. I say 'probably' because you'd be hard-pressed to get one at any price, as Jaeger won't sell them to you. And they will terminate their contract with an Agent if they think the Agent is selling you one. Some bellows may not even be available at all for the older calibres. Used bellows from scrapped clocks come up from time to time but if you're thinking of buying one, you MUST first check that it is the correct one for your clock's calibre and that it has not already part-collapsed (Image 4) or been filled with air instead. Expect to pay a hefty price, too; a while back, one American Atmos repairer offered me a repaired one for USD450 trade, "to help me out". Once you factor in Import Duty and VAT, that's almost £500! and it came with no guarantee whatsoever so I declined. Image 5 shows a solder-repair to the steel part of another bellows; it's not pretty (and it's NOT one of mine) - it failed after a refill as it could not take the pressure. So a money back guarantee when you're spending that much is essential.

Now, there are only a handful of repairers worlwide and none operate with Jaeger approval; most will only supply one if you have the clock serviced by them at the same time. I only know of one specialist offering a refill service and he's also in the US but because of the distance and interference from Customs at both ends, it can be slow. And it's difficult to post anything 'Signed For' because he uses a PO Box address. The one time I tried him myself, the parcel came back "undelivered" after three weeks, so it's not the perfect solution. I resent it and when it was finally repaired, it was overfilled so had limited capability.

I don't know of anyone in the UK currently offering a similar service (please let me know if you hear of one) but I am now able to refill most bellows for £125 including return postage within the UK. There are no postal delays, no Customs interference or international transit risks of loss or damage, and a turnround of three to four weeks is quite possible (subject to workloads and holidays).

This does not include any repairs so first your bellows need to pass a 48 hour pressurised leakage test. If a leak is revealed, and I think it might be repairable, I will tell you the additional cost before proceeding but it will probably be around £50. My solderless procedure is still under trial and even when perfected, I doubt that I will be able to repair every bellows. Hence, if there is a leak that cannot be fixed, the empty bellows will be returned for just the postage cost plus £50 for testing unless you're happy to donate it to the solderless trials programme. Otherwise, I might have a spare bellows I can fit instead.

Please bear in mind that I do not have the resources of Jaeger LeCoultre - this is, after all, just an extended hobby. But if you check my feedback on Google+ and elsewhere you will see that all my reviews are five-star, nothing less. So you can be reassured that I will do my best to provide a reliable and cost-effective service.

As always, please do NOT post or bring anything to me without contacting me first.


  • A fairly common Jaeger LeCoultre Atmos 'Living On Air' clock 528 calibre with square dial powered by gas-filled bellows on the back
  • The Atmos 'Motor' from a 528 calibre, comprising container, cover heavy spring and bellows to keep the mainspring wound
  • The mainspring barrel from an Atmos 528 calibre, dismantled to show the mainspring
  • Two Atmos bellows at room temperature, the one on the left having completely collapsed.
  • Another repairer's solder repair found on an Atmos bellows, ugly but nonetheless effective, having lasted for years