The symmetrical movement architecture of the Constant Force Tourbillon movement pays tribute to Arnold & Sons' historic marine chronometers. At the top, two visible mainspring barrels and the constant force device provide optimal power to the tourbillon at the bottom of the dial.
|Constant Force Tourbillon: Exclusive Arnold & Son mechanical movement A&S5119, hand-wound, anthracite open dial, 18-carat red gold case, diameter 46 mm © Arnold & Son|
Constant force is an essential element in the quest for higher precision because it is difficult regulating a consistent output, e.g. isochronal time when the power input from the mainspring is constantly changing. 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.
While the constant force mechanisms optimize precision with the movement in stable positions, the 60-second tourbillon averages out gravitational errors on the escapement by constantly rotating it through 360°. The difference between the rotating tourbillon and rotating constant force device is that the former turns continually while the latter steps in increments of one second.
Model: Constant Force Tourbillon, Royal Collection
Limited edition: 28 timepieces
Calibre: A&S5119, Exclusive Arnold & Son mechanical movement, hand-wound, 39 jewels, diameter 36.8 mm, thickness 6 mm, power reserve 90 h, double barrel, 21,600 vibrations/h
Functions: hours, minutes, true beat seconds, tourbillon, constant force
Movement decoration: nickel-silver and steel movement, palladium treated bridges and NAC grey treated main plate with Haute Horlogerie finishing: hand-chamfered bridges with polished edges and brushed surfaces, screwed gold chatons, screws with bevelled and mirror-polishedheads
Tourbillon cage: mirror-polished with hand-chamfered polishededges and circular satin-finished surfaces
18-carat red gold, diameter 46 mm, cambered sapphire with antireflective coating on both sides, see-through sapphire case back, water-resistant to 30 m
Anthracite open dial
Hand-stitched brown bottier alligator leather with patina