Audemars Piguet Royal Oak Extra Thin Selfwinding Flying Tourbillon

In order to fit the tourbillon cage into a Jumbo case, AP had to change several elements of the tourbillon cage from the classic version used in the caliber 2950 in the standard Audemars Piguet Royal Oak Selfwinding tourbillons. The caliber 2950 has an overcoil balance spring, while the newer caliber 2968 has a flat balance spring (most ultra-thin watches don’t have overcoil balance springs as the overcoil adds height). The balance in the 2968 has timing weights on the inside of the balance rim (in the 2950 they’re traditional weights on the outside of the rim) set flush with the rim. The balance arms have steps milled into them, which form a sort of recess that lets the balance spring sit closer to the balance – another height-saving measure.
One other notable difference is that while the 2950 uses conventional screws to fix the upper part of the tourbillon cage in place, the 2968 uses spline bolts, which usually take up less room than screws (although I’m not sure if this is the purpose here as I don’t have the dimensions for the bolts vs. the screws available). There are also cut-outs in the pillars of the tourbillon cage, which provide extra clearance for the balance rim, allowing AP to use a larger balance (this is also one of the benefits of the internal flat-rim weights). Finally, the tourbillon cage is driven via gear teeth on its outer edge. This is a so-called peripherally driven tourbillon. A traditional tourbillon carriage is driven via a pinion on the underside of the cage. Driving the cage directly from its edge produces a savings in height as well.
As we’ve said, the caliber 2968 is not the world’s flattest automatic tourbillon, but at 3.4mm thick, it’s pretty damned flat for a full rotor automatic tourbillon – to get any thinner than that you have to start using either a micro-rotor or a peripheral rotor. Before Bulgari’s Octo Finissimo automatic tourbillon came along, the thinnest automatic tourbillon (after the AP 2870) was the Breguet Classique Tourbillon Extra-Thin Automatic 5377, whose movement has a peripheral rotor and is 3mm thick (and again, it’s very wide at 36.10mm). Looked at in context, AP’s ability to make a full rotor automatic flying tourbillon which is only 0.4mm thicker than a much wider recent record-holder with a peripheral rotor starts to look a lot more interesting.
And aesthetically? What can I tell you, it’s a Jumbo, 39mm x 8.1mm, with that lovely Bleu Nuit, Nuage 50 dial. The only classic Jumbo element missing from the RD#3 Jumbo Tourbillon is the AP logo at six o’clock, but it seems a reasonable thing to lose if you’re going to have an open dial flying tourbillon. If you like the Jumbo, you’re probably going to like the Audemars Piguet Royal Oak Selfwinding Flying Tourbillon Extra-Thin RD#3, unless the idea of an open dial flying tourbillon is just not your brand of vodka. Comparing Audemars Piguet ultra-thin automatic tourbillons can be a little tricky – it helps to know the history of the complication and it also helps to understand that a full rotor movement compared to a peripheral rotor movement is fair on one hand, but on the other hand it’s also a little bit of an apples-to-oranges comparison. Seen from that perspective, RD#3 is a beautiful, very well-thought-out piece of contemporary watchmaking.