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AN OVERVIEW OF SOME MUCH LOVED COMPLICATIONS
Within this page we will be looking closer into some of watchmaking's finest complications in an informative, and inspiring way.
Moonphase
Moonphase
One of Horology’s most romantic complications, the Moonphase, visually describes the luminous part of the Earths orbiter we see in the night sky giving the viewer an accurate representation of the current phase. A common method of display is by physically hiding the section of the moon in darkness behind the aperture, and as the lunar cycle progresses, the mechanism behind the dial progresses the moon disk each passing day.

The orbit precisely takes 29 days, 12 hours, 44 minutes and 2.9 seconds. In terms of gearing and how it mechanically works, each day would count for a tooth on a driving wheel, but having half a tooth (the 12 hours) is not really feasible, so it is simplified by a 59 tooth wheel, allowing for two sets of 29.5 days. The moon disk is mounted to this toothed wheel.

Because of the imperfect number of days in the lunar month, inaccuracies arise. With a 59 tooth wheel, after two years, seven and half months, the cycle will be out by a full day. This doesn’t seem like much, but in world driven by precision and accuracy, it’s simply not good enough. With further advancements, higher toothed wheels are used to greatly improve the accuracy, some of which will only need to be adjusted by one day in 577.5 years.
Double Moon
Mechanically similar to the single moonphase, the double moonphase, or bi-hemispheric moonphase, shows the wearer the current phase in both the North and South hemisphere at the same time, by having two shaped apertures, revealing the moon disk below.

Potentially not the most useful of complications, but it adds a layer of beauty to the dial and allure to the already romantic complication.
Chonograph
Chronograph
The Chronograph. A complication often strongly linked IWC given their ties to motorsport and aviation, and this is because of its use. We use a chronograph to record an elapsed amount of time by means of a series of sub dials with hands that can be started, stopped, and reset via pushers or buttons. A stopwatch essentially. A typical chronograph will of course have the standard time telling minute and hour hand, with a running second hand in a subsidiary dial. There is a central second hand that is used to accurately read the elapsed time after the pusher has been pressed, along with another sub-dial that tracks the elapsed minutes. In some cases, there will be a third sub-dial that tracks the hours also.

Below dial is where the magic really happens. With the press of a button to start, a host of levers, cams, wheels and springs all work in complete unison to engage a separate train of wheels that are attached to the hands seen above dial starting the chronograph function. By pressing the start button, the column wheel is pulled round one tooth allowing a transmission wheel to come into contact with the chronograph wheel, shown above dial by the start of the chronograph seconds hand.

With a press of the stop button, a similar set of interactions occur, but this time the column wheel has been driven round again, pulling the transmission wheel out and the brake comes into engagement with the chronograph wheel keeping it stationary, thus stopping the hands also.

Two pusher chronographs can then be started again, but in order to reset, a push of the reset button pulls the column wheel round a further one tooth, lifting the brake out of engagement, and moving in the aptly named fly back lever to come into contact with the heart cams. A spring acting on the fly back lever ensures enough force is applied to the heart cams so they are forced round to the lowest point, and the wheels reset to zero as indicated by the hands.
Tourbillon
Tourbillon
In a standard mechanical watch train, power from the mainspring is transferred through each wheel and pinion to the escapement.

In a movement containing a tourbillon, the power is sent through the train as normal, but between the train and escapement this time, is the cage or carrousel which houses the escapement. Beneath the cage is a pinion that meshes with the last turning gear train, which enables the cage or carrousel to rotate on a central point. The tourbillon sits on top of a fixed wheel which meshes with the pinion on the escape wheel, which then travels around this fixed wheel.

This is where Breguet's idea that rotating the escapement would reduce the effects of gravity acting upon it came into play.

Then it's business as usual in terms of the escape wheel interacting with the pallets and so the balance wheel.
Retrograde
Retrograde Date Display
Retrograde Definition: To move back in position or time.

Within watches, we are used to seeing the standard cyclical motion of hands moving around the dial, which is one reason a Retrograde display becomes so special and has its place amongst much loved complications, as simple as it may look dial side. The Retrograde display is arc shaped and as time passes, an indicator follows this arc, but once reaching the end, jumps back in position to the start to resume its path along the arc once more.

This form of showcasing a passing time can be applied to any elapsing time be it seconds, minutes, hours, but in the case of this Portofino Tourbillon Retrograde, the date is what is being indicated in this manner.

The mechanics of this system can be seen in image 2. A complex combination of a date finger that progresses a snail cam and so a rack system that steps the time indicator along after each passing day. At the end of the month, the rack tail drops off the snail, causing the meshed gear to rotate anti-clockwise, sending the date indicator back to the beginning of the arc. This final process is assisted by a perfectly tensioned spring that as the month progresses, becomes less tense, and so allowing for this movement back on the 31st. This IWC system also allows for the date to be changed via the crown without needing to change the time.

I think it’s fair to say that a complication that follows a simple path above dial, below is much more of a mechanical task.
Timezoner
Image credit - Justin Hast
Timezoner
For a brand synonymous with aviation and the Pilots watch, teamed with a rich history of engineering, it makes sense that IWC have a patented mechanism that allows for the logical changing of time when entering one of the 24 different time zones.

With the latest release of the “Le Petit Prince” Timezoner, lets take a look at what sits beneath the midnight blue dial.

Ingeniously to stop accidental changing of time zones, with a slight push down on opposing sides of the bi-directional bezel, the bezel can be rotated so that the city of reference for the time zone you need is at the 12 o’clock position. This movement of the external/internal bezel rotates a series of gears that adjusts the hour wheel, 24 hour display, and the date wheel, in unison without stopping the movement below, maintaining the watches accuracy. To achieve this, an exact number of teeth on each wheel are needed to create the perfect ratio to keep them all in sync.

The Timezoner gives the wearer the ability to view the time on the opposite side of the world all with a simple twist of the bezel.