What Urwerk put together in the AMC project

Clock-and-watch set raises timekeeping to a new level

LIKE most developments in haute horlogerie, one of Urwerk’s latest creations was inspired by an Abraham-Louis Breguet work. Urwerk co-founder Felix Baumgartner’s AMC, while virtually sci-fi in both design and operation, is apparently based in principle on Breguet’s Pendule Sympathique — the dozen known examples of which the watchmaker produced between the late 1700s and the1820s.

The Sympathique (it is thought that Breguet himself had coined the term) combines a clock and a pocket watch, with the latter wound and regulated by the former via a complex system. To do these, the watch is placed on a cradle on the clock. It is then paired to the clock via a stem. This stem, a part of the clock, comes out as the clock strikes midnight.

When the two are connected, the watch’s mechanism is checked against the rate of the clock’s regulator. After which it is reset to match the clock, and is also wound during the process. Accounts have it that it takes about an hour or so to do all this. And the aim, of course, was to make a watch more precise than any other during the era.

With the AMC, Urwerk is pursuing the same goal while employing contemporary technologies. Instead of the clock-and-pocket watch combo of the Sympathique though, the AMC pairs an atomic clock with a mechanical wristwatch. As Urwerk puts it, it brings together two branches of watch making in one hybrid device.

The first part of the system is the Atomolith, an atomic clock Urwerk developed with SpectraTime. It relies on rubidium, and is housed in an aluminum case sized about the same as a computer. It’s the Atomolith that serves as the time reference for the AMC system.

And what accuracy rate this clock provides; Urwerk reckons the Atomolith will keep time to within one second in 317 years. This is possible, too, even if the clock must contend with factors that may disrupt its performance, such as temperature changes, power supply fluctuations, and even the aging of the atomic timing package itself.

URWERK AMC

The second component of AMC is the wristwatch designed specifically to work with the atomic clock. Unmistakably an Urwerk piece — meaning it tells time in a completely innovative way — it is fitted with brand-typical features like a unique power reserve indicator, two mainspring barrels stacked on top of one another (these allow a power reserve of four days), and an oil-change indicator that shows when the movement should be serviced. On the wrist, its accuracy is largely dictated by its balance mechanism — just like any mechanical timepiece.

But it has something else no other watch, Urwerk or not, has; a mechanism that lets it connect to a “base unit,” or the Atomolith atomic clock. When docked to this base unit, the clock will wind the wristwatch, set it to the correct time and adjust its rate if necessary.

Winding the watch is the most straightforward between the three functions; a shaft simply extends from the atomic clock, which then winds the watch’s crown.

Setting the wristwatch’s minutes and seconds display to match that of the atomic clock is slightly more fiddly; a pusher, similar to a chronograph’s, is triggered by the atomic clock, which then causes two sprung levers within the watch to press against the eccentric heart cams that spin the minute and second hands. These heart cams are calibrated in a way that when they come in contact with their levers, will set the hands to their respective positions.

URWERK AMC
URWERK AMC

The most technically challenging operation is adjusting the oscillation rate of the watch, which is controlled by a regulator. In mechanical timepieces, this usually involves a mechanism that can alter the effective length of the balance spring. Changing the length can speed up or slow down the rate at which the balance spins, adjusting the watch’s timekeeping accuracy.

In the AMC system, the clock activates a pusher on the wristwatch, triggering a sensor in the watch that detects any positive or negative deviation in time — measured in seconds — between the clock and watch. This sensor consists of a pair of calipers that close around a half-moon cam rotating co-axially with the seconds hand. The differing positions of the caliper jaws around the half-moon cam prompt a peg to move along a preset arc. Because this peg is connected to the device that alters the length of the balance spring, it can effectively change the oscillation rate of the balance mechanism. To what degree the peg does this is determined by the movement of the cam and calipers.

Now, the more frequent the AMC clock and watch are synchronized, the closer the watch comes to taking the same rhythm as that kept by the atomic clock. This synchronization, by the way, can be activated manually up to once every hour if so desired, or through a preset automated schedule.

Really, Urwerk is not kidding when it says a mechanical oscillator is not perfect — and perhaps will never be — but that in the AMC it is already self-perfecting. Mr. Breguet should be proud.