In Detail: The Royal Oak's Cal. 3120 Manufacture Movement
Update
Audemars Piguet have launched their new website for SIHH 2012 and they've captured the essence of the Royal Oak quite splendidly!
Introduction
The RO features an in-house AP 3120 caliber manufacture movement that runs at 21,600 vibrations per hour (vph) / 3600 = 6 beats per second. Accounting for the change in direction of the balance, its operational frequency is 6/2 = 3 Hz.
A few days after purchasing my Royal Oak, I noticed how its seconds hand seemed 'float' less smoothly in comparison to my Rolex DateJust (and other Rolexes I've owned in the past). The reason for this is that current-production Rolex movements operate at a higher rate of 28,800 vph (8 bps/4 Hz) — hence, allowing the seconds hand to 'float' far smoothly.
Important: My use of the word 'smoothness' in the prior paragraph refers to the how one visually interprets the motion of the seconds hand; it carries no baring on the quality of the movement and/or its finishing and/or functional operation. The human eye integrates such movement into a continuous flow; you may have experienced moments of noticing AC powered lighting to flicker (especially in third-world countries) — this is because mains electricity has a frequency ~50 Hz.
I took a 1-second time-lapse photograph to verify the 6 beats per second movement of the seconds hand on the RO, as seen above.
The movement has 40 jewels, 278 parts and a 22-carat gold rotor — boasting a power reserve of 60 hours.
Note: in fact, the cal. 3120 possesses 45 jewels, but because the jewels under the date wheel, by industry protocol, are not included in the final published jewel count, the "official" jewel count is "only" 40)
Image Source: ThePuristS.com - http://www.p178host.com/apgallery/3120/
Apart from the unusually higher power reserve, resulting from the lower-beat rate, the movement also features a balance-stop mechanism on pulling out the crown to ensure the seconds hand can be precision set. Another interesting feature prevents one from damaging the date-setting mechanism if the quick-set date is accessed between the 8 pm - 2 am 'window'.
Quoting the article at ThePuristS,
Some points maybe of interest for the future owners of a watch with this movement: it should be impossible to damage or do any harm to the date mechanism whenever or however the date quick set is used. If set through hand-setting, it will work clockwise while counterclockwise nothing happens. If the quickset is used in the period between 8:30 pm and midnight, the usual date switch is missed, but it is impossible to damage anything by setting/quick-setting at the wrong "time window".
Finishing
Ignore the casing specification below, as the finishing details have been taken from a different AP with the same movement. The Royal Oak is 39 mm in diameter.
Royal Oak and its 22k Gold AP Rotor
The 22k gold rotor on the cal. 3120 is quite striking considering its unusual 'bell' shape and surface engravings.
Here are a few closeup images shot at f/2.0 — the resulting shallow depth-of-field (DOF) compensated with hand-shake due to the tricky task of shooting the movement with the bracelet attached to the watch casing.
Looking Through the Caseback
The Horse
The Castle
References
The reference listed below is highly recommended for its movement tear-down on a functional basis although one should bare in mind the article is from 2004 and focused on a 'pre-series' movement.
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