Random objects: Spaceview

I am not a wristwatch nerd, but I am fascinated by the history of things. Whether I’m chronicling the collapse of currencies or flipping through old comic books, I feel more connected to the bygone era than when I’m reading a history book.

The evolution of watchmaking always registered in the periphery of my interests, but it did not strike me as particularly significant. Still, there was one artifact I simply had to get my hands on. Meet the Bulova Accutron 214 Spaceview:

Accutron 214 movement, microscope photo by author

Made in the 1960s, the watch wasn’t merely some footnote in the annals of watchmaking. It was the harbinger of the era of portable electronics.

The Accutron is often described as the first electronic watch, but that’s not entirely accurate: the title belongs to a handful of obscure battery-powered designs that cropped up in the late 1950s. The early “electric” watches employed a traditional mechanical movement, but replaced the mainspring with a switch and an electromagnet that delivered synchronized impulses to the balance wheel.

Because of the inherent reliability issues of mechanical switches, the electric watches performed poorly and never gained much of a market share. The Accutron did things differently. First, it made use of a newfangled piece of technology - the transistor - to implement a solid-state sensing mechanism:

A point-to-point transistor circuit inside the watch, photo by author

The Bulova design also dealt away with the balance wheel as the timing reference. Instead, the designers employed a precision-machined tuning fork that, when periodically nudged by the electromagnets, resonated at a frequency 360 Hz. The fork is prominently visible in the front view, extending throughout the height of the watch.

To convert the vibrations into useful motion, the Accutron relied on a hair-thin ratcheting pawl mechanism that pushed on an extremely fine-toothed gearwheel; in effect, the tuning fork served both as the timing source and as a stepper motor of sorts.

The Accutrons delivered unparalleled accuracy and reliability; they even went into space. Their reign ended with the advent of the quartz watch in the 1970s. Quartz watches employed more sophisticated circuitry to operate a high-frequency crystal oscillator - and then use electronic signals to control a stepper motor or an LCD, dealing away with the bulk of the mechanical components of a watch.

Today, crystal oscillators are ubiquitous as a source of timing signals in digital circuits. Curiously, they still rely on mechanical vibrations, and some are still shaped like a miniature tuning fork. But because they resonate at much higher frequencies, gone are the days of that soothing 360 Hz hum on your wrist.