Sunday, January 09, 2005

Volume 1, No. 7
edited and published by Victor Cuvo

A Brief History of the Bulova Accutron

It has been said by others that the Accutron watch was developed by the Bulova Watch Company as a response to a perceived requirement by the American Army for a better time standard. I don't know whether that is true or not.

Bulova Technical Documentation states quite clearly that the watch was developed entirely as a consumer item, with no funding from any outside source. Still, it might be fair enough to imagine that the potential military applications hadn't gone unnoticed by Bulova management. The CEO of Bulova at the time was Omar Bradley, 5 Star General, US Army, Retired. All research undertaken was performed by Bulova engineers in their own labs.

Although the tuning fork concept had been had been previously demonstrated in clocks, they were never mass produced, let alone miniaturized to watch-size. Work began on the development of a Tuning Fork watch in 1953 by the engineer Max Hetzel.

The first protype watches were produced in Switzerland in 1955. In 1959, Max Hetzel and William Bennett further developed the Bulova Accutron at the Bulova Headquarters in New York, based on Hetzel's previous research in Switzerland.

The first Bulova Accutrons were offered for sale to the public in November 1960. These were the Accutron Model 214.

Production of tuning fork Accutrons ceased in 1977, with Bulova directing their efforts to producing quartz watches. The name "Accutron" is still used by Bulova on some of their quartz watches. These watches bear no relationship at all to Tuning Fork watches.

To learn more about Max Hetzel, the inventor of the Bulova Accutron, and a more detailed history on the early development of the Accutron, I recommend you visit Barbara Young-Hetzel's site ACCUTRON - Max Hetzel, the Man behind the Invention.

Tom Mister of Dashto Horological Services has put together an excellent history of Accutron watches, depicted by their adverts over the years. Click Here to visit his site.

The seven Bulova Watch Factories - 1966
bfny.jpg - 13.34 K Bulova Headquarters, Bulova Park, Long Island, New York
bfwny.jpg - 17.10 K Woodside, New York
bfsh.jpg - 17.39 K Sag Harbor, N.Y
bfpri.jpg - 11.99 K Providence, R.I.
bftc.jpg - 12.80 K Toronto, Canada
bfbs.jpg - 14.02 K Bienne, Switzerland
bfns.jpg - 13.69 K Neuchatel, Switzerland

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The Bulova Accutron was the
first electronic wrist watch and marked a revolution in horology in the early 1960s. It was entirely different in principle from traditional timepieces. The greatest difference between the Accutron and conventional watches was the use of the tuning fork as the time standard instead of the traditional balance wheel and hairspring which had been used for over 300 years.

To listen to an interview with Max Hetzel, Click Here to visit the page on this site.

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Astronaut Scott Carpenter with his wife on
the cover of the 9 June 1962 Paris Match issue.

Scott is wearing an Accutron Astronaut.

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The following article by Mike Richards published in Popular Electronics, December 1960 explains how a tuning fork watch works.

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A 1960 Accutron Model 214 featuring
a battery hatch and a setting
handle at the back.

Transistorized Watch
"Tickless timepiece"
controlled by electromagnetic tuning fork
boasts minute-a-month accuracy

A new sound of time - a "microsonic" tone to replace the centuries-old ticking sound is given off by a new Bulova Watch Company timepiece called the "Accutron". Guaranteed accurate to plus or minus one minute per month, this transistorized device is about ten times as accurate as a conventional fine-quality wristwatch.

From the outside, the Accutron looks like a conventional watch, except that there is no winding or setting stem. Instead, on the back of the case, there is a recessed handle for setting the hands and a removable cap for mercury cell replacement.

On the inside, there is the power cell, a set of drive coils, a transistor switching circuit, and an electromagnetic tuning fork - it's the latter that gives off the barely-audible 360 cycle tone.

Drive coils. A pair of drive coils mounted near the tuning-fork tips keep the fork vibrating. A sensing coil picks up pulses from the fork and triggers the transistor to deliver current to the drive coils. One of the drive coils has 8000 turns of very fine wire, the other has 6000 turns, with the remaining 2000 turns making up the sensing coil.

Attached to one of the tuning fork tines is a tiny index spring. A jewel on the tip of the spring engages ratchet teeth on an index wheel which is moved forward one tooth for each cycle of the tuning fork. To prevent the index wheel from moving backwards and returning to its original position, a pawl finger rests on the wheel's teeth. The wheel which turns the gear train connected to the Accutron's hands, is 0.095" in diameter (about the size of a pin head); its 300 precisely-machined teeth are separated by one-thousandth of an inch about one-third the diameter of a human hair!

In operation, the voltage induced in the phase sensing coil is added to the powercell voltage to charge a capacitor (see schematic). A resistor slowly discharges the capacitor. The recharging pulses from the phase sensing coil cause the base circuit to conduct, allowing a driving pulse to flow in the drive coils.

Amplitude Control. An important feature of the circuit is that it will return the tuning fork's amplitude to normal after any disturbance. The proper amplitude is maintained by controlling the size of the drive pulses.

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Tuning fork, drive coils, and electronic components (see circuit below ) are located at
rear of Accutron (above, left); regulator on dial side (above, right) enables jeweler to adjust
the fork's frequency. Max Hetzel, Bulova's chief physicist, is the Accutron's inventor.

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The collector circuit conducts at the instant the induced voltage in the drive coils is at a maximum and opposite in polarity to the power-cell voltage. If the tuning fork's amplitude is high and the induced voltage equals the power-cell voltage, no current will flow and the amplitude will drop. If the fork's amplitude is low - more current will flow in the drive coils and bring the amplitude up to normal.

The specially designed mercury cell will power the timepiece for at least one year before replacement is necessary - the Accutron requires only about eight-millionths of a watt for operation.

Mike Richards

Who is Max Hetzel?

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Max grew up in a happy family where curiosity in science was encouraged. His father taught him how to build things and together they often explored the natural world in the forests and hills around Muttenz in Switzerland. It was his father who later insisted that he attend the Mathematical and Natural Science College, as Max himself did not particularly like school and wanted to become a radio technician.

During his youth, there was often not enough money available to buy the things he longed for, so he went to the dumps of his home town and looked for items he could use, as he loved to tinker with mechanical objects. One day when he was about 10 years old, he found an old dynamo. He mended this treasure and fixed it to his old bicycle. As he did not own a lamp he used an old tin with a little bulb attached on the inside. At nightfall pedalled very fast and, leaning over the handlebars, he was able to see a faint light. This experience had a very strong impact on Max and from this moment on he knew he wanted to become an engineer.

Now he needed a steady supply of electrical components. A friend of his whose father owned an electrical supply store let him go through the storage rooms filled with old junk. Every time Max found a treasure he wanted he had to pay his friend with a tadpole, frog or the like as he did not have any pocket money.

Max always wanted to know how things worked. As a boy his curiosity in science often got him into trouble. When he was eleven he received an old pocket watch from a relative and while at Sunday School the following day his curiosity got the better of him. Also, he found Sunday School rather boring. He just had to have a look inside the watch to find out how this wonderful thing worked. So he opened the back of the watch with his Swiss army knife and looked at the movement with amazement. Of course the Sunday School teacher caught him and punished him severely for not paying attention to the lesson!

After that he built a variety of radios and a simple telephone. To be able to speak to someone he had to give his younger brother a treat so that he would agree to talk to him on the phone for a few minutes.

After primary school he went to the Mathematical and Natural Science College in Basel. His primary school teacher in Muttenz told him he did not think he would succeed in this elite school and that he had better buy a return ticket home. Max was hurt by this remark, but he was also determined to succeed. He did not want to disappoint his father who believed in him.

Often his science hobbies were so tempting that he forgot to concentrate on school. When he was in high school he was very interested in astronomy. Lacking the funds to buy a telescope, he decided to grind his own powerful lens and build a telescope. This labor of love cost him over 720 hours of painstaking grinding. The result was that he almost had to repeat a year in school because he fell behind with his studies. Nevertheless, his telescope was a great success and he finished high school with the best results in his class.

After serving in the army he was able to enrol at the ETH, the Federal Institute of Technology in Zurich. He loved mathematics and physics and worked hard to earn his masters degree in Electronics. His degree thesis "Electromechanical frequency filters for telegraphy channel transmission" received the University's Silver Medal Award for outstanding achievement. This paper contained the mathematical basis for the calculation of tuning fork watches. But at this stage Max Hetzel did not recognize this important fact. Nevertheless, his thesis later influenced him when he was looking to reinvent watchmaking.

After university Max first worked for Hasler in Berne where he invented radio-television devices using tuning forks. When he asked to receive royalties for his invention Hasler refused. But Max and his family could not live on the modest salary he received and so it was time to look for a new employer. Bulova Watch Company in Biel advertised that they were looking for a talented engineer and that they were offering an interesting and well-paid job.

Although Max knew very little about watches, he was interested in the job and so he and his family moved to Biel, where he later invented the first electronic tuning fork watch.

To read about the development of this amazing watch please go to "Development of the Accutron".

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I firmly believe that if Max had not invented the Accutron he would have made some other great discovery. He has over 100 patents to his name and not just in the watchmaking field. Once he left the watchmaking industry in his late fifties he invented and patented a computerized tapping machine. Why a tapping machine? Because he used to get frustrated with the conventional tapping machines during his watchmaking years! In the early eighties he taught himself computer science and built and programmed his own computer in order to produce this precision tapping machine. Even today at the age of 78 he still reads books on physics the way you and I might read a novel.
Who is Max Hetzel? He is a scientist and inventor par excellence, driven by the desire to learn and to find new ways of doing things.

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1972 Advertisement for Ladies Accutron

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The Armed Forces chess champ was to receive this Spaceview for the victory. Interesting picture tells price and shows box style from 1972.

OFT 765
Click Photo
This is a great looking Accutron Spaceview, model N0, (1970) Swiss Case. Handsome, minty condition, SOLID STAINLESS STEEL, featuring A Stainless Colored Movement, White luminous hands and white sweep, gorgeous silver hour chapter ring all make this a wrist watch to have. Watch measures 34.5mm in width and 39.6mm lug tip to lug tip in length, & has been fitted with an "OFT SIGNATURE GATOR" Strap. Professionally serviced, running well and keeping good AccuTime.
Warranty on this GREAT WATCH!
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Current ad for Accutron Spaceview