Wristwatch restoration, servicing and repair

Posts Tagged ‘Eterna’

Eterna Automatic (Eterna Cal. 1076H)…

Cutting quite a dash on the blog is this dress watch from Eterna.

(Click pictures to enlarge)

Time has certainly been kind to this watch as an inscription on the caseback dates it to 1947, making it a sprightly 65 years old.  Removing the caseback and taking a look inside revealed an Eterna Cal. 1076H – a style of movement that I’ve yet to talk about on the blog, a ‘bumper automatic’.

Bumper automatics were the first self-winding wristwatches, and were initially developed by John Harwood, a watch repairer from Bolton, who patented his invention in 1923. Harwood’s system uses a pivoting weight which swings back and forth as the wearer moves, transferring power to the mainspring.

The motion of the winding rotor is restricted to an arc of around 300 degress, at which point the rotor bumps against one of two stops, each protected by a spring. This abrupt halt can be felt when wearing (or holding) the watch, hence the name ‘bumper automatic’.

Another feature of bumper automatics is that they only wind the mainspring in one rotor direction. In the return direction, the mechanism simply ‘freewheels’ back to the starting position.

Below is an image showing the two extremes of the winding action. At the heart of the mechanism is a ratchet and pawl. If you look at the (gold coloured) ratchet lever you will see that it moves back and forth with the movement of the rotor. It’s this action that transfers power to the mainspring barrel.

Although something of a breakthrough in its day, it was a relatively inefficient mechanism and the design was soon surpassed by ‘full rotor automatics’ in which the winding rotor is free to rotate 360 degrees left or right. Depending on the design, power can be transferred to the mainspring as the rotor rotates in either one or both directions. Rolex pioneered full rotor automatics, releasing their first Oyster Perpetual model in 1931 – the ‘Perpetual’ part of the model name denoting the perpetual movement of the winding rotor.

Ok, back to business. The watch arrived in running order but was loose inside the case. In the first movement picture you may have noticed an ugly piece of bent metal sticking up from the centre. As the winding rotor occupies almost all the space inside the case there is no room for a traditional ring/spacer to hold the movement in place. To overcome this problem, a casing spring is attached to the top of the movement and as the caseback is tightened, the spring is compressed, securing the movement inside the case.

The original spring had obviously been lost or broken during the last service, and the watchmaker attempted to make a replacement spring from any old piece of metal that was handy – it looks like part of an old train bridge to me. It didn’t work, and it was not the most aesthetically pleasing solution anyway, I’m sure you’ll agree.

To put things right I made a new casing spring from a thin piece of steel which I shaped to fit and then drilled at one end to secure it in place. With that problem solved, the movement was then given a full service to bring it back up to scratch.

The owner asked me if I thought the dial had been re-finished as its condition is near perfect – something you don’t often see in a watch of this age. Inspecting the dial and hands with a microscope it is clear to see that the hands and dial markers have been re-lumed at some point, but whether the dial has been re-finished too I couldn’t say for sure – given its condition it would be easy to assume that is has, but if so then it was extremely well done.

Re-finished dial or not, the watch is certainly attractive, and I’m sure it could find a place in anyone’s collection.


** Many thanks to Neil Clarke for letting me feature his watch on the blog. **

Eterna Chronograph (Valjoux Cal. 726)…

Another top quality vintage chronograph on the blog, this time from Eterna.

(Click pictures to enlarge)

The movement inside this watch is a Valjoux Calibre 726 which is derived from one of Valjoux’s most recognised and respected calibres, the Calibre 72.

Changes were made the original Calibre 72 in 1974 to upgrade the escapement, namely decreasing the size of the balance and raising the beat rate from 18,000 to 21,600 bph. The higher beat rate increases accuracy, as a smaller, faster moving balance wheel is less affected by changes of position or knocks. Comparing the two movements you can see that the balance wheel is considerably smaller on the 726.

Although running on arrival, the watch was gaining around 5 minutes per hour, which immediately pointed to potential escapement problems.

With the caseback removed, the cause was immediately obvious. The whole movement was covered in a film of oil which had eventually found its way onto the hairspring, sticking two of the coils together. This drastically reduces the amplitude and causes a significant time gain.

Having spotted that problem I thought that it would be plain sailing from here on in… but no. On rebuilding the watch after cleaning, the wheel train was not running freely and had a noticeable tight spot. Further investigation revealed that the mainspring barrel had been damaged at some time in the past and was no longer running true – the teeth were visibly rising and falling as it rotated.

Rather than replacing the mainspring barrel when it was damaged, the previous watchmaker had tried to ‘work around’ the problem by bending the mainplate in several places to give the barrel more room – a big mistake!

As you can see in the picture below, the chronograph hour register and its reset hammer are located on the dial side of the movement opposite the barrel, so consequently, bending the mainplate had an effect on these parts too.

The tolerances for these parts is minimal even with a perfect mainplate, so it was no surprise that the reset hammer was dragging on the mainplate and the hour register was also binding. Not good.

After ordering a new mainspring barrel and mainspring, the required ‘adjustments’ could be made to the mainplate. Obviously, with the parts all in place it isn’t possible to make the required tweaks, so the watch had to be disassembled each time, making it a time consuming operation.

My patience paid off and the problems were resolved eventually, so with everything working again I could complete the rest of the rebuild.

From a cosmetic point of the view the watch was in pretty good shape, but the lume had deteriorated over the years. The dial also had a thin film of oil over it and several marks in the subdials. With careful cleaning and a relume things were much improved, but I couldn’t do anything about the scratches in the hour subdial.

The hands were relumed too and the case cleaned before reassembly. Quite a bit of effort to get this one back in order, but well worth it I’m sure you’ll agree.


** Many thanks to Simon Fox for letting me feature his watch on the blog. **

Eterna KonTiki Super (Eterna Cal. 1489K)…

Here’s a cool vintage diver, an Eterna KonTiki Super from the 1970’s.

(Click pictures to enlarge)

Founded in 1856 by Dr Josef Girard and Urs Schild, the company initially specialised in producing pocket watches with alarms, but as the demand for watch movements of all kinds continued to rise, a subsidiary company “ETA SA” was created in 1896 to supply good quality calibres to other Swiss watch manufacturers. The name of the founding company was changed from Schild Fréres to Eterna in 1905.

Eterna had a number of technical achievements over the years, but their most significant innovation was undoubtedly the “Eterna-Matic” – an automatic winding mechanism featuring a ball-bearing rotor system which increased efficiency and reduced wear.

The Eterna-Matic was first fitted to a production watch in 1948 and was subsequently used in the majority of their watches. The mechanism was such a success that the layout of the five ball-bearings in the rotor became the logo for the brand.

The KonTiki range was created in the 1950’s as a tribute to the trans-Pacific voyage taken by the Norwegian writer and adventurer Thor Heyerdahl. Inspired by old drawings made by the Spanish Conquistadors, Heyerdahl and his team travelled to Peru and constructed a pae-pae raft from balsa wood and other native material, which he named “KonTiki” after the pre-Inca sun god.

On April 28th 1947, Heyerdahl and a crew of five set sail aboard KonTiki attempting to cross the Pacific Ocean. After 101 days and a journey of over 4,300 miles the raft crashed into a reef on August 7th off the Tuamotu Islands in French Polynesia. The crew all survived, and the adventure declared a success. (See here for more information).

Though Heyerdahl had no involvement in Eterna’s KonTiki range (you may read that Heyerdahl and his team all wore Eterna watches during the trip – it isn’t true), they proved to be very successful for the company, and are still in their collection today. As well as diver’s watches, the range also included dress watches, these two vintage KonTiki 20 models being typical examples;

On the caseback of every KonTiki model is an image of the KonTiki raft with the Eterna logo on the sail. Being a much softer metal than the stainless steel back, the medallions can wear smooth with extensive wear, and that is the case with the watch in this post.

Inside the watch is an Eterna Cal. 1489K which of course features an Eterna-Matic winding mechanism with the trademark five ball-bearing rotor system.

The watch was losing a significant amount of time when worn, but needed no more than a service to bring it back into line.

Another thing to notice about this watch is the bezel markings. Rather than the usual ‘countdown’ bezel used to time the length of a dive, this watch is an example with the rarer ‘decompression’ bezel.

In case you have trouble finding a vintage model, Eterna re-issued a version of the Super diver in 2010 to commemorate the original – albeit in a limited edition run of just 1,973 units. (Full details here)


** Many thanks to David Brenchley for letting me feature his watch on the blog. **