Atmos Repair

I received this beautiful, broken clock as a gift from my father in law, who knows I love clocks and fixing things. This particular clock is a Jaeger‑LeCoultre Atmos - named because it is powered by fluctuations in temperature and pressure. It has a lot more in common with a wristwatch than a clock - lots of delicate parts, jeweled pivots, and a need for a steady hand.

The inner workings are quite clever. At the back of the clock is the bellows, a sealed container of ethyl chloride that expands and contracts with atmospheric changes. The bellows winds the clock via a ratchet. Its analagous to how an automatic watch winds itself with the motion of your arm. The Atmos isn't technically perpetual motion, but I haven't had to wind mine since I got it in 2018.

My clock arrived in a non-working state. It wouldn't run. You could wind it up manually, but it would stop after a few minutes. After disassembling the bellows and taking some measurements, I was pleased to discover that it was in good shape. This meant I didn't have to send the bellows in to be refilled.

I decided to fix it myself. I purchased a service manual and a special tool to remove the hands. I carefully disassembled the clock (taking tons of photos along the way), ran every part through my ultrasonic cleaner, and reassembled it. Unlike most clocks, this one reassembles dry, with no lubrication on any of the pivots. Reassembly was very finnicky, but I got there.

Once cleaned, it ran perfectly, though a bit slow. I've been able to regulate the clock so that it only loses about five minutes a month, though it fluctuates with the season. I suspect this is due to thermal expansion of the pendulum, but I'm not sure.