ESA 9162/4

These movements are the "Rolls-Royce" of tuning fork watches, and were designed by Max Hetzel, who had left Bulova a few years previously. Hetzel was also the brains behind the Accutron 214. The 9162/4 and 9210 were known as the "Swissonic" line of movements. They were manufactured under licence to Bulova by Ebauches S.A., who, up until then, made several models of electronic balance wheel watches. The index wheels for the ESA tuning fork watches were made by Bulova. These movements are superbly made, and were used by Omega (known as the f300, cal.1250 and 1255) Certina f300, Movado (Zenith cal. 50.0 variation) Longines (Ultronic), IWC and others. Most watches using these movements were tested to Chronometer grade and sold as such. The design of the tuning fork in these watches is slightly different from that of Accutrons(see pics below). The tines of the fork were extended back from the mounting point and balanced with the main tines. These additional arms on the fork are attached close to the magnets. This design gave them superior performance, as their errors due to position were nil. The Esa 9162 version had a date function, the 9164 having both day and date. The Esa 9210 is a chronograph version of the 9164.

Accutron 218 tuning fork	ESA 9162 tuning fork

These watches are constucted in a modular form. The first module, called the "mechanism module", is comprised of the pillar plate, date mechanism, minute-work, and final reductions of the gear train. The second module, called the "oscillator module", comprises the back plate, tuning fork, electronic circuits, index wheel and first reduction. Do not attempt to remove one of these movements from its case without following the correct procedure, or damage to the index mechanism will occur if the second-hand is accidentally moved.

Oscillator Module - click to enlarge	Mechanism Module - click to enlarge

Esa 9162/4 Index wheel life explained

A rumour has been circulating that these movements "chew up" index wheels, and it is due to the shorter index and pawl fingers that these movements have. Is this true? Firstly, it is true that index wheels are more often replaced in these watches than in Accutrons. Secondly, it has nothing whatsoever to do with the length of the index and pawl fingers "placing increased pressure on the index wheel" as some repairers would have us believe. In fact, the index and pawl fingers in a 9162/4 are only a fraction of a millimeter shorter than those in a 214 or 218 Accutron.

The cause of the problem lies within the Mechanism Module, and specifically, the Setting Clutch (see pic below). This is a slipping clutch that allows the hands to be moved seperately from the actual watch train, for setting the time. This clutch has - for want of a better term - a design problem such that when the oil in the clutch either slowly evaporates or goes thick with age, it can transmit too much torque to the watch gear train when setting the watch. The effect of this extra torque is to cause the index wheel to unlock from the fingers, and spin. Not so bad if occurs in the normal direction of rotation, but if it is allowed to spin backwards, the index wheel teeth are eventually shaved off by the index and pawl jewels.

Can anything be done about this?

Yes, the problem can be minimised. Firstly, make sure the watch gets serviced regularly (every 5 years) by someone who knows what they are doing. This clutch can be lubricated without totally dismantling the watch, or upsetting the index adjustment. Also, when setting your watch, minimise the amount of backward movement of the hands. Use the fast date corrector to reset the date. Check the page on setting these watches (here) if you are not sure.

Click to enlarge

It is interesting to note that the circuit for these watches is virtually identical to the Accutron 214. No surprise really, since they were both designed by Max Hetzel, and ESA were licensees to Bulova anyway. The R-C network and the feedback coil have been interchanged compared to the 214. This would have been done simply to allow for the different construction of this watch. Electrically, it is no different.