I remember them being called 'Tuning Fork Watches'.
Yes that's correct, the watch uses a tuning fork as its prime moving element. It is a well understood physical principle that the faster your initial reference the more accurate your time keeping will be. The most accurate clocks nowadays use the vibrations of a caesium atom as their reference. In the 1950s the best mechanical watches could rely on a prime moving element with a frequency of around 2 Hz (That is two 'beats' per second). Max Hetzel an engineer employed by the Bulova Watch Company of Bienne Switzerland designed an electrically excited tuning fork movement with a a frequency of 360 Hz. Bulova claimed an accuracy of 2sec per day or 1 min per month. This was the only movement capable of the accuracy demanded by spaceflight. Accutrons were used as time references in many satellites and also to control some of the Apollo moon experiments.The Tuning Fork Movement is absolutely unique in operation emitting a distinctive hum and featuring a sweep seconds hand. Here's a reproduction of an advertisement produced by Bulova in the early 1960s.
Accutron calibers and marques.
The first successful accutron caliber (1960 on) was designated 214 and was available as a standard or 'hack' movement (a hack feature stops the second hand whilst the watch is being set). This movement was utilized in many marques including 'rail road approved' types and most famously the see through 'Spaceview'. The now much sought after Spaceview (as above) affords a view of the tuning forks, electromagnets and control circuitry. The 214 movement can be identified by the setting device which is located at the back of the watch. There is no setting crown ! The 214 was followed by the 218 which again was used in many marques but never a Spaceview. Most 218 movements are set by a crown located at the 4 O'Clock position (some variants have two crowns at 2 and 4 O'Clock).
The Accutron, especially the Spaceview captured the 'Zeitgeist' of the 1960's absolutely. Man's first foray into space, the birth of the electronics industry, the first useable digital computers and eventually the Apollo program; heady times indeed ! The Accutron is a worthy icon of this epoch. Later calibers included the 219, 230 and 231 which offered different geometries of both tuning fork and electromagnets.
Max Hetzel was also the creative engineering force behind both the Swissonic (never sold due to patent infringement) and the Omega Megasonic, a design that took micro-machinary to a level which is to this day stunning.
Some Accutron Facts (Engineers take note this was achieved
Sean's "How It Works" Page
Here we will undertake take a step by step explanation of how an Accutron functions. I will assume a very basic knowledge of electro-magnetics (about 'O' Level for us Brits or Grade ?? for our American friends). If you always hated physics at school don't click here .
Sean's "My Accutron's" Page
Sean's "Latest Accutron acquisition" Page
Click here to see my latest Accutron acquisition
Accutron Links Page
Here are some links that address
some very common questions such as "Where can I get my Accutron fixed
?" and "What's all this about batteries ?" I have leant heavily
on Rob Bercavicius site "Down Under" and Tom Mister's site in the USA
Please email me with any comments, I can be contacted