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A 100% in-house made movementCalibre 2897 is a selfwinding movement entirely developed and produced by Audemars Piguet. It combines a tourbillon and a column-wheel chronograph. Its architecture is a tribute to the past. The rounded cut-out of the bridges, the S-shaped lever, the curves of the minutes-counter bridge and the characteristic toothing of the column wheel: everything about this mechanism displays consummate artistry, to the point of making us almost forget the functional aspect.
The finishing of the various parts is also loyal to the grand traditions of Fine Watchmaking. Several surfaces shine with a perfect polish, known as a mirror or specular polish, which catches the light and results in exceptional optical effects achieved by various polishing operations involving a succession of files, buffs, burnishers and various abrasives. On all the interior and external corners, the sharp edges between the surface and the flanks are cut down to form polished bevels. This is the meticulous operation known as bevelling or chamfering, and which is entirely performed by hand on all parts. The bridges and mainplate are rhodiumed, bevelled, circular-grained, beadblasted and hand-drawn with file strokes. After each of the parts is finished and decorated, the watchmaker performs a first “trial” assembly in order to set them into motion. Everything is then dismantled and each part is meticulously cleaned, before proceeding to final assembly and casing up. It takes around 15 days to produce a finished movement, which is then subjected to a number of different tests.
The peripheral oscillating weight, an efficient and elegant solutionAutomatic winding is ensured by a peripheral oscillating weight in 950 platinum, mounted on ball bearings. This choice serves to shift the weight of the rotor to the outer edge of the movement, thereby improving winding speed. A recess has been made in the case middle so as to ensure that this 180° oscillating weight can rotate a full 360°. It is also worth specifying that this large 180° segment is optimally sized to enhance the efficiency of the automatic winding. Moreover, because of its position on the periphery of the movement, it does not increase the overall thickness, which enables the movement to maintain a slimmer profile. It also offers the additional aesthetic advantage of entirely freeing up the reverse side of the movement and thus providing full views of the mechanism, and particularly its column wheel, through the transparent back of the watch.
The tourbillon, the most entrancing of all horological complicationsVery few watch brands are capable of making their own tourbilllons. An acknowledged member of this select circle, the Manufacture Audemars Piguet has become a master in the art of defying the effects gravity and has over 16 movements equipped with a tourbillon. In 1986, it was already the first brand to offer an ultra-thin selfwinding tourbillon wristwatch.
Representing watchmakers' response to the laws of gravity, this invention serves to cancel out the disturbing effects of gravity on the movement's most sensitive organs - the balance and spring assembly and the escapement - and to thereby achieve enhanced timing precision. To compensate for these disturbances, these organs are housed within a tiny feather-light mobile carriage that spins on its axis once a minute.
The tourbillon with its blackened titanium bridge is visible through a dial cut-out at 6 o'clock. Setting this tourbillon into motion represents a formidable technical challenge. A weight of just 0.017 grams serves to balance the carriage weighing a mere 0.45 g. Meanwhile, in terms of the lightness of the regulating organs themselves, the escapement weighs just 0.12 g. The experienced watchmaker devotes almost three days to assembling its 85 parts, while the overall movement takes over 15 days.
The chronograph, a constantly perfected mechanismCalibre 2897 reveal its column wheel, an attribute of the finest mechanical movements and which serves to coordinate the start, stop and reset phases. An ingenious coupling yoke principle has been developed in order to avoid the chronograph hand jerking when the timing begins, a characteristic flaw of this type of mechanism. The development engineers have added a hook to the coupling yoke which thereby displays enhanced shock resistance when the chronograph is activated. The meticulous assembly and adjustment operations are entirely performed by hand and require particular care. The activation of the chronograph functions is thus carried out progressively in order to enable gentle and accurate tactile perception.
TECHNICAL DATAS :
Royal Oak Offshore Selfwinding Tourbillon ChronographReference26550AU.OO.A002CA.01
Forged carbon case; bezel, crown and pushpieces in black ceramics; pushpiece-guards and fastening studs in titanium
MovementSelfwinding Calibre 2897 with tourbillon and column-wheel chronograph
Total diameter: (15_ lignes)
Casing diameter: 31.40 mm
Thickness: 7.75 mm
34 jewels
335 parts
65-hour power reserve
Cadence of the balance: 21,600 vibrations per hour (3 Hz)
Variable-inertia balance with screws and balance-spring with Phillips terminal curve
Finishing: all parts finely hand decorated; bridges and mainplate rhodiumed, circular-grained, beadblasted and hand-drawn with file strokes; polished angles, bevelled screw rims and slots
Peripheral oscillating weight in circular satin-brushed 950 platinum
CaseDiameter : 44 mm
Thickness : 14 mm
Sapphire crystal caseback with Royal Oak Offshore engraving
DialBlack with exclusive “Méga Tapisserie” motif, silver-toned counters. Applied and facetted white gold hour-markers with luminescent coating. Black flange. White gold facetted hour and minute hands with luminescent coating.
StrapBlack rubber, adorned with two grooves. Titanium pin buckle.
FunctionsHours and minutes
Small seconds at 9 o'clock
Chronograph with central sweep-seconds hand, 30-minute counter (at 3 o'clock)
Tachometric scale on the flange
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