At 98 mm in diameter and 50.55 mm thick, you probably would not want to put the Vacheron Constantin Reference 57260 in your pocket. Why is it that the more complicated a watch is, the thicker it is? The answer reveals a lot about movement architecture and design.
Like building architecture, movement architecture relies on certain critical elements to keep everything working well. Tall buildings depend on elevators to quickly move people from floor to floor. Comparatively, a complicated watch movement is built around the rotation of the center and fourth wheels. These wheels rotate at once per hour and once per minute, respectively. The wheel axes or arbors are used to power the complications connected to them, arranged in a level-by-level fashion, similar to floors in a tall building.
For the most part, calendar complications use the length of a day to show their information. If we know how long one day is we also know the length of months and years. Fortunately, the center wheel makes one rotation per hour. A reducing gear train on the dial side of the movement at a ratio of 24:1 gives us exactly one day, and enables the calendar complication to function. From the tall building metaphor, we now have two floors. The ground floor is the movement’s basic gear train, dividing time and transmitting power to the escapement. The second level is the calendar, using the center wheel arbor as its input.
Next, we will consider the chronograph complication. Because chronographs record small segments of time, they are driven by the fourth wheel. (The fourth wheel makes one rotation per minute.) This again adds to our movement architecture, and we are now on the third level.
Dial-side of the Vacheron Constantin Reference 57260
Finally, we will consider the repeater complication. It too uses the center wheel arbor for input, in addition to the fourth wheel arbor. A snail cam is mounted on each arbor, to indicate the hours and minutes that should be struck via the hammers and gongs. That gives us four levels to deal with, all stacked upon each other and depending on the same inputs.
The Vacheron Constantin Reference 57260 has 57 complications; it should now be quite obvious why the watch is so thick. And now, the Armillary Tourbillon with spherical balance spring begins to make a lot of sense. In any other watch, this tourbillon would add a large amount of thickness to the movement. In the Reference 57260, it looks completely appropriate, and adds three dimensional motion to this fascinating movement.