Watches are all about oscillations and oscillators. A watch needs to have something inside it that moves in a way that can mark time. Since the fourteenth century, this has been a balance wheel, mounted on pivots and powered by a spring. The ‘tick, tick, tick…’ you hear when you hold a watch to your ear is the balance wheel swinging round, getting caught by the escapement and swinging back.
The more oscillations the wheel can make in a second, the more accurate the watch, by and large. As watchmakers and metallurgists have got cleverer, so balance wheels have got faster. The fastest mechanical watches today usually beat at around 36,000 beats per hour – around 10 per second – with a few specialist movements going a whole lick quicker.
But there’s only so fast a wheel can rotate before physics gets in the way. So watchmakers started looking for better, faster, oscillators. And that’s how they arrived at watches with a tiny piece of quartz as their oscillator.
Today, if you have a quartz watch on your wrist, the tiny quartz crystal tuning fork sealed in a vacuum inside is beating at 32,768 times a second. Get yourself a Grand Seiko quartz with a 9F movement and it’s so accurate you only need to set it when the clocks change.
But there was a stage between balance wheel and quartz that often gets forgotten – tuning fork watches.
In 1953, sixteen years before Seiko’s first quartz watch, Arde Bulova and Max Hetzel collaborated to file the patent on a movement that used a tuning fork. This is the watch that became the Bulova Accutron. When the tuning fork vibrates in an Accutron, it moves a tiny ruby-tipped escapement that allows a 2.4mm diameter wheel to rotate, tooth by minute tooth. The second hand sweeps, rather than ticks, around the dial. And, rather than ticking, an Accutron hums.
With just 12 moving parts and a battery for power, the Accutron not only never needed winding, it was as accurate as its name suggests. A battery meant there was no decay in power each day as the spring lost tension. The tuning fork was practically impervious to positional errors.
Although the watch was accurate to just two seconds a day, this wasn’t that remarkable. There were already mechanical watches running at this sort of rate. But accurate watches had always been expensive, maintenance-intensive and relatively fragile. What marked the Accutron out as different was its price, its freedom from the need for regular maintenance and its ease of use. Accuracy had become democratic.
Accutrons have bounced along the bottom of the watch market since they fell out of favour in the 1970s. As quartz took over, the Accutron and its heirs, the Omega Megasonic cal. 1220 and 1230, the Swissonic and the HiSonic, became little more than curiosities. Now, they’re starting to become collectable in the mainstream. The skeleton Spaceview, the Astronaut and gold-cased models are beginning to fetch serious prices. Best not hang around if you want something historic in the watchbox that hums.