The openworked Royal Oak has been around for years, but the originator of this line couldbe 2010’s 15305. Then, we saw in 2012 and 2014 respectively, the traditional 39 mm Jumboget “openworked” in platinum and rose gold. Now, we see the current 41 mm Royal Oak, reference 15400 openworked for the first time, but with a brand new double-balance wheel escapement that is a world’s first!
Now AP has produced a few very high-end watches in the past that used two balance springs, but not two balance wheels. They include the Millenary Quadriennium and Millenary Minute Repeater with AP Escapement. The thinking here is that having two balance wheels creates an oscillator with more mass, ensuring great stability – why, for example, you see huge oscillators in marine chronometers. In previous watches, the two balance springs would counteract the effects of gravity on the balance itself. Basically whenever the balance spring contracts, it tends to push the sides of the balance staff against the sides of the cap jewels. That extra friction affects rate, and it does so to a different amount depending on the position of the watch. Theoretically, the double balance springs should cancel out each other’s rate errors in the vertical position as well.
This new Royal Oak takes things one step further and in fact features not only two balance springs, but two entire balance wheels. As you can see above, they are set against each other and should not only provide much greater mass but also work against each other to self-regulate. Very cool.
Now the other thing this watch offers is truly high end openworking and component finishing. The entire caliber is completely hand finished, and the interior angles that we see all over this movement are the product of nothing but the human hand. Like the most recent open worked RO’s, the 15407 features a stunning deep grey dial and gun-metal treatment that make the entire look far less ornate and old than traditional skeletonized watches. The golden balance bridge lets you know that there is a little something special going on there, too.
The Audemars Piguet Royal Openworked Double Balance Wheel is sized at 41 mm in diameter, features a 45-hour power reserve thanks to the thin 5.57 mm caliber 3132. It is available in both stainless steel and rose gold, both non-limited.