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Watches in Depth - Oddball Complications

by Jason 13 février, 2012 Voir les commentaires

(Cet article n'est pas disponible en Français)

IWC Deep One with Depth GuageIWC Deep One dive watch, which featured a Bourdon Tube depth mechanical depth gauge.

So far in the Watches in Depth series I’ve given coverage to the most important and most popular forms of complication – chronographs, tourbillons, calendars, and repeaters. These complications are well served in the current market. What about the odd complications, the one offs, the rarities that never became widespread? This feature is to highlight the forgotten complications that are often overlooked and under served in the modern market.


Some complications had their heyday in the past, but haven’t translated well into the modern era of watchmaking. One of the best examples is the dead-beat seconds mechanism (also called “sauterelle” or secondes mort). The dead-beat mechanism leaves its children and doesn’t provide support payments… No wait, it translates the usual smooth sweep of a mechanical seconds hand into a quartz-like one-tick-per-second. It does so by placing a spring-loaded gear between the escapement and the seconds wheel; the gear loads up and releases at a steady interval based on the beat of the movement, so if it beats 5 times per second the gear will release every 5th beat. Back in the good ol’ days, this was a prized complication that offered precise timing, particularly for doctors who needed to time pulse intervals with their watch, or in chronometers and clocks where to-the-second accuracy was paramount. Why did it fall out of favour? Well, when you see a ticking seconds hand, do you think “haute horlogerie” or “Timex”?

 Rolex Tru BeatRolex Tru Beat with the dead-beat mechanism exposed in the centre (the automatic rotor has been removed to show the detail)

The rise of inexpensive quartz movements that all feature a dead-beat seconds function effectively killed the demand for mechanical dead-beat mechanisms. People associate it with a “cheap” watch and aren’t keen to have an expensive watch that at first glance would look like a knockoff with a quartz movement. The odd thing is that early quartz calibres had a sweeping seconds hand – it was, after all, what people were used to seeing in a watch up until that point. The problem was battery life – with constant motion it drained the power much more quickly than if they designed it to only jump once per second. Hence why dead-beat became the norm in quartz watches. There are still a few brands that build mechanical dead-beat seconds in one form or another, but it is far from common. The most famous is the Rolex Tru-Beat, a model made for a brief period in the 1950s. It was marketed to doctors but never achieved much success – and the majority had their dead-beat mechanisms removed later on to restore the classic sweep! Original Tru-Beats with unmolested movements command a premium today due to their rarity.

 Girard Perregaux Annual CalendarGirard Perregaux Annual Calendar with equation of time indicator (between 4 and 5 o'clock on the lower right of the dial)

So you have your late-on-child-support seconds, now how about a minute hand that is only correct four times a year? That would be the equation of time, something that today is only found on some of the most complicated watches on the market (it’s something of a “we need more complications, lets use some of the obscure ones” add-on in super-complex designs). What the equation of time does is show the difference between mean time (the standardized time we all use) and solar time (the local time based on the movement of the sun). Depending on the time of year the variation can be as much as 16 minutes; it only coincides with mean time four days a year – April 15th, June 13th, September 1st and December 25th.

 Sandford FlemingSir Sandford Fleming, the Canadian man who devised standardized time.

This complication dates back to the beginning of standardized time. Before governments regulated time (yes, they control time as well as taxes), each town would set the local time according to the movement of the sun. That meant that there were variations even across relatively short distances, something that became a major problem when the railroad sped up travel across country (our modern Greenwich Mean Time was the brainchild of Canadian Sandford Fleming as a way to regulate local timezones for railway schedules, because each stop would be using a different local time). When central observatories began “setting” the time and broadcasting it to multiple regions (either by a system of telegraph wires or by literally carrying a chronometer around to set the time in different towns) the old solar time became redundant – but some folks still wanted to track the difference between the two. The equation of time adds an indicator, or a second minute hand, that runs faster or slower than the mean time based on the equation of time calculation (tied to a calendar mechanism). Depending on the time of year it will be either slower or faster than the mean time. Today it is not a common complication by any means, being reserved for the highest level of watchmaking (the super-complicated designs that crams as many functions into a watch as possible). You won’t see much in the way of a simple watch with a EoT mechanism, it is usually combined with an annual calendar at the minimum. The most recent watch to incorporate a solar time display is the new IWC Portugiese Sidereal Scafusia (which also track sidereal, or astronomical, time - an even more esoteric complication).

 IWC Sidereal

IWC Sidereal Scafusia. Sidereal time is indicated on the subdial at 12 o'clock. Solar time is shown on the back of the watch.

If you read my previous feature on chronographs you will know I am a fan of the rattrapante, a chrono that splits the second hand in twain at the touch a button to allow you to take split times. It’s a very complex and delicate mechanism that is not particularly cheap. There was, however, a form of quasi-rattrapante that was developed in the 1940s called “Index-Mobile”, a split-seconds chrono for the masses.

 Dubey Index MobileDubey & Schaldenbrand Index Mobile chronograph. Note the spring in the centre of the dial.

The Index-Mobile was produced by Dubey & Schaldenbrand and was based on a Landeron or Venus manual-wind chronograph calibre. It featured a split seconds hand with a large hairspring connecting the two hands together visible on the dial. You would start the chronograph as per usual and when you pressed the split button (the third button separated from the start/stop and reset pushers) a lever would push against the shaft of the split hand, stopping it in place while the main seconds hand kept running. Unlike a rattrapante, you had to keep pressing the button to hold the hand in place – when you release it, the hand snaps back into position via the hairspring and joins the still-moving seconds counter. The advantage was split timing with a very simple and inexpensive mechanism that could be installed on an existing movement. The disadvantage was that you could only hold the button for maximum of 58 seconds before the spring would become too tight (a rattrapante split time can be run indefinitely).

Dubey Index MobileAnother Dubey Index Mobile that clearly shows the distinctive hairspring linking the split hands together. The button on the crown is held down to activate the split time, and released to sync the hands again.

Dubey went the way of the dodo after the Quartz Crisis of the 70s. The company continued making Index-Mobile movements for a few other brands (including Breitling) but by the 80s the party was over. D&S was revived in the 1990s with a re-edition of the Index-Mobile that used new-old-stock movements; that was the last instance of the peculiar complication, with its distinctive hairspring floating over the dial. Dubey still produces watches today but no longer make any Index-Mobiles, a shame because it was one of their most distinctive pieces and a great conversation piece. The Index-Mobile was produced back when a rattrapante was an extremely expensive complication that was a real challenge to produce and adjust. Some have compared the task of building a rattrapante to that of building a minute repeater – which is to say, really frigging complicated. Today several companies mass produce reliable rattrapante mechanisms, including one based on the ubiquitous Valjoux automatic chronograph, that are far more “cost effective” than they were back in the 1940s (they are still not cheap, but they are more accessible today than they once were). As a result the Index-Mobile became a curiosity of another age.

 Breguet Tourbillon a FuseeBreguet Tradition Tourbillon a Fusee. The fusee chain and cone-shaped barrel is visible below the dial. The mainspring is opposite the fusee assembly.

A problem that plagued early watch and clock designs was the variation of torque through the mainspring as it unwound. The force applied through the movement would vary considerably as the spring tension released, and the amplitude (beat) of the movement would change as a result, affecting accuracy. There were several solutions to this issue that became common on high-precision movements such as chronometers and observatory clocks. There was the constant-force escapement; in watches it was a device that would build power in a secondary spring connected to the mainspring before releasing it at regular intervals into the escapement, keeping the flow of torque consistent through the mediating mechanism. There was also the fusee chain system, where a secondary cone-shaped barrel was connected to the mainspring barrel via a tiny link chain. You wound the mainspring via the fusee, which would pull the chain and rotate the barrel. As the mainspring unwound the chain would wrap around the barrel while varying the tension (the cone shape of the fusee barrel would apply more tension as the mainspring unwound).

 Lange 31 EscapementThe Lange 31 constant force escapement. The device is to the left of the balance wheel, with the visible hairspring. The mechanism loads up and releases every 10 seconds.

Nowadays torque variation affecting the amplitude isn’t so much of a problem. Advancements in metallurgy and tolerances allow a much more consistent flow of power, even in inexpensive movements. Automatic winding keeps the mainspring wound at a consistent level while you are wearing the watch. Double or triple sequential barrels can smooth out the flow of power in manual wind movements. So a constant-force device isn’t really needed to ensure accuracy – but that doesn’t stop some manufacturers from making them, for the sake of complication. Breguet produces a fusee-chain system in their Tradition Tourbillon Fusee. F.P. Journe has a constant force escapement in their Tourbillon Souverain, as does A. Lange & Sohne in their Lange 31 (which has a 31-day power reserve! The constant-force device is needed to regulate the torque of the massive mainspring). Another solution in multi-day movements is a stopwork that stops the movement when the spring nears the end of its wind. The IWC 7-day movement could actually run 8-9 days, but automatically stops after 7 to ensure that the amplitude stays consistent.     

 Breguet Montre a TactBreguet Montre a Tact. The mechanism is visible on the right side photo.

Back in the days before artificial light, a major problem facing watch owners was how to check the time in the dark – without burning the house down. Rather than lighting a match or candle to check the time a few ingenious devices were invented – that’s how we ended up with repeaters. Nowadays we rely on luminescent compounds. But what if you want to check the time in the dark – and be discreet about it? That is where the montre-a-tact (“discreet watch”) comes in. Popular among Breguet’s customers, the montre-a-tact allowed the user to check the time without pulling the watch out of their pocket or sounding a chime. It had a large hand affixed to the outside of the case. A mechanism integrated into the cover allowed the hand to rotate counter-clockwise until it matched up with the hour hand on the dial, where it would stop. A series of ridges or bumps along the edge of the case indicated the hours. So by rotating the external hand into position and feeling for the hour markers, the wearer could get a rough estimate of the time without looking bored and embarrassing his/her host by pulling out the watch to check the time. Where a repeater or sonnerie was extremely expensive to produce, the montre-a-tact was easy to build and quite popular among the high society of the 19th century. It was marketed as a “night watch”, or a watch for the deaf who could not hear a repeater (there was also the “dumb” repeater design which would strike a block inside the case to make a dull thud that could be felt in the hand). While you won’t find any equivalents today, the montre-a-tact is considered the precursor of the brail-watch that allows the vision-impaired to open the crystal and feel where the hands are to check the time.   

 Breguet Montre a TactBregeut Montre a Tact with enamelled finish. Note the hour-indicator ridges, marked on this example with pearls.

Breguet Wandering Hours

Breguet Wandering Hours pocketwatch. The window rotates to indicate the minutes - it is indicating 10.12.

You’ve probably seen a watch featuring jump-hours (or even jump-minutes in a few rare cases). Digital displays on mechanical watches are very difficult to execute and are often featured in haute-complications. Jump-hours have been around for quite some time, but were not the only style of digital display. One interesting complication that has fallen out of favour is the wandering hour. Instead of having a fixed window for the hour display, the window rotates around dial. The position of the window indicates the minutes. It’s a rather complex mechanism that combines a jump hour with a mystery dial (where the dial itself rotates to indicate the time). Both discs (the dial, and the hour indicator) have to rotate together to keep everything lined up. Urwerk makes the best-known modern interpretation of the idea; the UR-203 uses a series of rotating spindles to show the hour as the spindle sweeps across an arc indicating the minutes, an advanced form of the concept.

 Urwerk UR-203The Urwerk UR-203, which modernizes the wandering hour concept. The spindles rotate to indicate the hours, the pointed tip indicates the minutes. So the watch here is showing 8.17.

Let’s say you are a professional diver. You want a high-spec diving watch that can give you on-the-fly depth readings. Nowadays you would buy a dive computer or a digital watch with diving functions (like the Tissot Sea-Touch), but at one time you could get a mechanical watch with a mechanical depth indicator. A few designs existed, but most operated on the same principle – a small button on the side of the case featured a spring-loaded piston attached to a flexible coiled tube, called a Bourdon Tube. When the pressure of the water pushed the piston into the case, the bourdon tube would flex and a lever system would move a hand on the dial to indicate the equivalent depth. Some had a max depth hand that would stop at the deepest point of the dive (it could be reset to zero afterwards with a pusher on the case). It’s a rather delicate mechanism that never achieved much success; it is hard to maintain water resistance when you have a button on the side of the case designed to push inward with increased external pressure. IWC still makes a mechanical depth gauge in its Aquatimer Deep Two (which was preceded by the Deep One a few years prior). Panerai cheated a bit with their PAM00193 by offering a battery-powered electronic gauge that displayed the depth on an analogue scale, with a separate automatic movement for timekeeping. In any case, it isn’t a complication you will see often, as it is a device usually reserved for professional dive computers, not expensive mechanical wristwatches that will likely never see use in water.

 Bourdon Tube

The Bourdon Tube mechanism. It's the same mechanism you will find in a mechanical pressure gauge.A similar design was used in the IWC Deep One.

The world of fine watchmaking is awash with odd functions, complications and devices, some of which become popular, and others that fell by the wayside. It may be because they are a product of their time, or something that doesn’t have widespread appeal. In any case, every year we see a slew of new and often weird complications as manufactures try to outdo each other and offer something other than the traditional chronograph/tourbillon/perpetual calendar/minute repeater variations. What I have covered here is just the tip of the iceberg when it comes to strange and unique complications. And just when you think you have seen everything, someone comes along and creates an oddball complication that bucks convention. Or better yet, takes all of the weird complications and combines them into one watch.


Jason Cormier

 IWC Deep TwoIWC Aquatimer Deep Two, which features a proprietary depth gauge design that can measure up to 60 metres of depth and record the max depth.

IWC Depth Guage

 IWC Depth gauge mechanism as found in the Deep Two. The blue hand indicates the current depth, the red stops on the scale to show the max depth.




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