For all their advances, mechanical watches haven't changed fundamentally in over 340 years. Now Swiss watchmaker Zenith has broken new ground by creating an "oscillator" that replaces the conventional spring escapement with a precisely engineered silicon disc. Zenith claims this makes its Defy Lab the world's most accurate mechanical watch.
Though portable mechanical clocks have been around since the early 16th century, it wasn't until 1675 that it was possible to build what we would now recognize as a watch.
A couple of decades prior, in 1656, the Dutch scientist and inventor Christiaan Huygens came up with the first precision timepiece when he invented the pendulum clock, which uses the period of a swinging weight against a toothed escapement wheel to regulate the fall of a weight. This was so precise that more advanced versions were the standard for timekeeping until the 1930s.
The problem was that pendulum clocks are the exact opposite of portable. The first portable timepieces made in Germany in the 1530s used a coiled mainspring for power, but the use of tiny chains wrapped around a spiraled cone was so imprecise that these contraptions only had an hour hand.
Then, in 1675, the prolific Mr. Huygens struck again when he created the modern spring balance escapement – the heart of almost every mechanical watch built today. The modern variants use a balance wheel, balance spring, escape wheel, and pallet that turns the energy of the mainspring into a series of precise pulses.
Looking at the Zenith Defy Lab watch, it's obvious that something else is at work. Instead of the conventional spring balance, the movement visible behind the dial seems to vibrate like some powerful machine that's on the verge of exploding into bits. That's because the spring balance has been replaced by Zenith's new oscillator.
Unlike a conventional balance mechanism made of about 30 components, the new oscillator is a single, monolithic skeletal disc 0.5 mm thick. It's made of monocrystalline silicon coated with a layer of silicon oxide worked to tolerances finer than a human hair by Deep Reactive Ion Etching (DRIE), which uses plasma make deep, precise etchings.
Zenith is a bit coy about exactly how the oscillator works, but Hackaday says that the geometry of the disc is broken up into a pattern of vanes and springs along with two tiny teeth that transfer forces back and forth between the oscillator and the rest of the movement. Three blades act as springs while shorter blades create the rotational force that turns the watch's gears. Meanwhile, another set of blades dampens any vertical motion.
The makers of the Defy Lab say that, unlike a balance, the oscillator needs no lubrication, balancing, or calibration and is insensitive to temperature gradients, gravity, and magnetic fields. It beats at 15 Hertz with an amplitude of +/- 6 degrees (opposed to a conventional movement's 300 degrees) providing an accuracy of within 0.3 seconds per day. For comparison, a chronometer certification requires an accuracy of 10 seconds per day.
This frequency is so fast that the watch has a permanent-running seconds hand and, despite the high frequency, the movement has a 60-hour power reserve and it remains accurate even with 95 percent of the mainspring expended. In addition, the Defy Lab has chronometer certification by the International Bureau of Weights and Measures, meets the ISO-3159 thermal standards, and ISO-764 magnetic criteria to 1,100 Gauss.
The Defy Lab uses the 148 component, 18-jewel Zenith Oscillator Calibre ZO 342 movement powered by an oscillating weight adorned with the "Côtes de Genève" motif. The dial has a simple display of hours, minutes, and central seconds, and the movement is visible through the anti-reflective sapphire crystals on the front and reverse.
The case for the Defy Lab is also worthy of comment. Instead of the usual metals, it's made of Aeronith – the world's lightest aluminum composite material. Though it looks like solid metal, it's actually an aluminum sponge filled with a UV-resistant polymer that makes it 2.7 times lighter than titanium and 10 percent lighter than carbon composites. The result is a light, strong case water resistant to 5 ATM. It's secured by a black rubber strap with alligator leather coating and a titanium double folding clasp.
If you're looking to buy a Defy Lab, you're out of luck. Only ten of the US$30,000 units were made in ten different versions, but these were all pre-sold before the watch's September debut. However, Zenith says that it is working on serial production with a new design.
The video below introduces the Zenith Defy Lab.