To maximize power consistency in the Constant Force Tourbillon, Arnold & Son began at the beginning, i.e. the mainspring barrel, as this is the source of the movement's power. Instead of using just one mainspring barrel, which would produce significantly different amounts of torque between fully wound and nearly empty, the Constant Force Tourbillon has two symmetrical barrels in series, visible dial side at 10:30 and 1:30. The first mainspring barrel alone powers the gear train, while the second barrel tops up the first whenever its torque output drops below optimal. This ensures that the power to the regulator flows as constantly as possible.
The Constant Force Tourbillon features a patented constant force mechanism. Instead of power from the mainspring feeding directly to the escapement/tourbillon, it charges a small hairspring which in turn releases a consistent amount of power to the escapement/tourbillon once each second. The device also drives the true-beat seconds hand (also known as jumping seconds or dead seconds), a highly cherished Arnold & Son complication. When the power from the mainspring drops below that required by the constant force mechanism, the movement stops rather than running at lower precision. The constant force device rotates once per minute in increments of one second, visually mirroring the rotation of the constantly rotating tourbillon cage. The bridges supporting the constant force regulator and tourbillon are also symmetrical, both horizontally with each other and vertically with the barrel bridges.
Exclusive Arnold & Son mechanical movement, hand-wound
diameter 36.8 mm
thickness 6 mm
power reserve 90h double barrel
Tourbillon cage: mirror-polished with hand-chamfered polished edges and circular satin-finished surfaces.
18-carat red gold case, diameter 46 mm, cambered sapphire with anti-reflective coating on both sides, see-through sapphire case back