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Movement Complications (Video) from PIAGET: part 4 – Perpetual Calendar

Piaget Complicated Movements: part 4 – Perpetual Calendar

Piaget is one of the rare fully integrated Haute Horlogerie manufacturers. 

In-house, Piaget has created 35 movements, including 11 complications in the last 14 years. Piaget has mastered 4 of the 5 classic major complications – Automatic Tourbillon, Chronograph, Perpetual Calendar and Minute Repeater – with the added complication of being ultra-thin.

This series of articles will trace the Piaget Path through Complicated Movements.

I was puzzled for years why Piaget did not have an in-house perpetual calendar in their modern catalogue.

This was particularly noticed as we held a series of global Perpetually PuristS events on 28th February each year. There were no Piaget watches at those events. When asked, Piaget people gave enigmatic smiles, as if to signify something was in the works.

Perpetual Calendar Algorithm.
A major factor relevant to the perpetual calendar algorithm is the peculiar and variable length of February. February used to be the last month of the year with the first 11 months (March through January) having a five-month repeating pattern of days: 31, 30, 31, 30, 31, ...,

For a more detailed treatise on 'Calendar Watches', please read the excellent article by Prof Marcus Hanke by clicking the following URL Link:
http://home.watchprosite.com/?show=forumpost&fi=17&pi=4127896&ti=656186&s=

Piaget 855P movement back

Piaget 855P movement side 

How does a perpetual calendar mechanism work?  (Simple explanation version)

The principal part of the mechanism is the perpetual lever which pivots. It returns to resting position by the action of a spring and usually pushes against the perpetual cam. A small 'finger' completes one turn per day when it drags the lever at the midnight hour. In practice, this is usually adjusted between 23:00h and midnight.

Day change.
The perpetual lever has two pawls (allowing one-directional movement of the gear wheel, like ratchets), that are moved by two independent springs. Each day, around midnight, the lever moves a seven-pointed day-star forward by one day.  Five times a year, when the date changes from the 30th to the 1st (except Leap years: from February 28 to 29), one pawl causes the hand to move from 30 to 1 (or from February 28 to March 1).

Month change.
For the month change, a lever moves the month-star from February to March.
The perpetual lever at rest, pushes against the perpetual cam. This cam is the 'memory' for the perpetual calendar. It has seven ridges corresponding to the months with 31 days, four dents that correspond to the months with 30 days and a movable rectangle for February.

The cam thus determines the three levels of rest for the perpetual lever: 31-day months vs 30-day months vs 28/29 day February. The pawl of the perpetual lever can occupy one of three different levels. For the months of February, the lever pushes on one side of the rectangle allowing the pawl to move the date from February 28 or 29 directly to March 1.

Year change.
The Leap year mechanism is a small movable rectangle with three sides equidistant from a centre of rotation; a fourth side is positioned higher than the others. This mechanism only rotates one-quarter of a turn each year so that once every four years, the highest side pushes on the lever. For that Leap year, the pawl will only act on the 29th of February.
 

Piaget Emperador Coussin Perpetual Calendar Two Time Zone: perpetual mastery of time.

Following on from the mechanisms developed for the flying tourbillon, the tourbillon relatif and the chronograph, Piaget pursued the quest for horological complications by presenting the Manufacture Calibre 855P with perpetual calendar in 2008.

With this perpetual calendar development, Piaget achieved the third pillar of haute horlogerie movements.

2008 Perpetual Calendar 855P: 

Mechanically programmed to cope with the irregularities of the Gregorian calendar up until the year 2100, the perpetual calendar is one of the major complications of the watchmaking art, as well as one of the most widely used.

Measuring only 5.6 mm thin, the Manufacture Piaget Calibre 855P self-winding movement was designed, developed and produced entirely in-house. It displays the hours, minutes, small seconds at 4 o’clock, month and leap years at 12 o’clock, along with retrograde day of the week and date displays at 9 and 3 o’clock respectively.

In addition to the latter retrograde indications, this Calibre 855P stands out from most ordinary perpetual calendars by the addition of a double-hand dual time-zone display appearing in a sub-dial at 8 o’clock. The self-winding Piaget Calibre 855P beats at 21,600 vibrations per hour and is endowed with an approximately 72-hour power reserve.

The case of the Piaget Emperador Coussin Perpetual Calendar was inspired by a vintage model. The subtle curve of the 46 mm case enables it to adapt to all wrists and imparts a particularly elegant profile. Piaget wanted to make horological complications with user-friendliness; the case middle carries a mention of the function of each of the four correctors for the month, date, day of the week and second time zone.

Subtly alternating polished and satin-brushed surfaces on the case middle, bezel and inner bezel ring, the case of the Piaget Emperador Coussin Perpetual Calendar is fitted with a sapphire crystal back providing views of the movement finishes.

The plate and bridges are circular-grained, bevelled and drawn out with a file. The decorative features such as circular Côtes de Genève and blued screws match the brand’s aesthetic signature codes, while the oscillating weight is adorned with the Piaget coat-of-arms.

All the decoration and finishing, along with the casing up, are performed in Piaget’s La Côte-aux-Fées workshops which are entirely dedicated to horological complications. The complex nature of the movement powering the Piaget Emperador Coussin Perpetual Calendar explains its restricted annual production. The case of each timepiece is engraved with the year of production and the number of watches produced.

A highly exclusive Haute Horlogerie model, the Piaget Emperador Coussin Perpetual Calendar is available in an 18K pink gold version on a brown leather strap complete with 18K pink gold pin buckle, along with a version in 18K white gold.

18K pink gold case
Blue dial, satin-finished counters, applied 18-carat pink gold hour-markers, case-back fitted with sapphire crystal revealing the movement
Manufacture Piaget 855P mechanical self-winding perpetual calendar movement
Functions: Hour, minute, small seconds (at 4 o'clock), dual time (at 8 o'clock), month/leap year (at 12 o'clock), day (retrograde indicator at 9 o'clock) and date (retrograde indicator at 3 o'clock)
Movement thickness: 5.60 mm
Casing dimensions: 28.4 mm
Number of jewels: 38
Cadence: 21,600 vph
Approximately 72-hour power reserve
Finishing: circular Côtes de Genève, circular-grained plate, bridges bevelled and drawn with a file, blued screws, oscillating weight engraved with Piaget coat-of-arms
18-carat pink gold pin buckle
Brown alligator leather strap
Ref.G0A33019

Interesting side-note  

The 1,000,000th Piaget watch ever produced was a special Emperador Coussin Full-set Perpetual Calendar .

In addition to the usual form and function of the regular model, this special watch had the following extra gem-setting specifications. The movement was designated 856P to account for the different rotor.

18K white gold case set with 314 brilliant-cut diamonds (approx 2,5 cts), 60 baguette-cut diamonds (approx 5 cts)

Dial set with 263 brilliant-cut diamonds (approx 1.2 cts), guilloche and satin-brushed counters, applied 18K white gold hour-markers, case-back fitted with sapphire crystal revealing the movement

Crown set with 12 baguette-cut diamonds (approx 0.4 ct)

Manufacture Piaget 856P mechanical self-winding perpetual calendar movement with retrograde day and date display, and dual time zone.  Oscillating weight set with 25 brilliant-cut diamonds (approx 0.2 ct)

18-carat white gold pin buckle set with 7 baguette-cut diamonds (approx 0.6 ct)
Ref.G0A35020

Fitting the case back with sapphire crystal.

PIAGET Path through Complicated Movements series   

Piaget Complicated Movements: part 1 – Tourbillon hand wind (Click the following URL link):
piaget.watchprosite.com

Piaget Complicated Movements: part 2 – Tourbillon automatic (Click the following URL link): 
piaget.watchprosite.com

Piaget Complicated Movements: part 3 – Chronograph (Click the following URL link): 
piaget.watchprosite.com

Piaget Complicated Movements: part 4 – Perpetual Calendar (Click the following URL link):

piaget.watchprosite.com  

Dr M. Teillol-Foo (2013)

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