Finally, this week at Baselworld 2015 we were able to work on our hands-on review of the new Arnold & Son Constant Force Tourbillon unveiled pre-Baselworld a few weeks ago. This time, Arnold & Son pushes precision chronometry ever further with the Constant Force Tourbillon, featuring a patented constant force device with 60-second tourbillon and true beat seconds. 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. The Constant Force Tourbillon has two symmetrical barrels in series, visible dial side on its anthracite open dial at 10:30 and 1:30, tourbillon at 4:30 and constant force mechanism with built-in dead beat seconds at 7:30. This elegant complication is fitted with a massive 46 mm 18K red gold case —that surprisingly doesn't wear too big, perhaps because of its double-step bezel—, satin brushed finished lug sides, equipped with a beautiful light brown alligator strap with double folding buckle and a display case back.

The Constant Force Tourbillon is part of the Royal Collection and, like every other model from Arnold & Son, features an in-house mechanical movement. John Arnold (1736-1793) was constantly searching for higher precision in his timepieces, as the more accurate the chronometer, the more precise the calculation of longitudinal —east/west— position at sea. Arnold and his son were the first to develop and produce technically superlative —but reasonably priced— marine chronometers in significant quantities. 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. Imagine trying to drive a car at a consistent speed with an engine that continually varies its power output.

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. Just as if the front of the watch wasn't impressive enough, the back is extremely beautiful and a real treat for the eyes. The exclusive Arnold & Son manual wound calibre AS5119 powering this timepiece has 39 jewels and provides a power reserve of 90 hours when fully wound.

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. 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.

On the wrist, as mentioned earlier on this post, the watch doesn't wear as big as its actual size. With outstanding wrist presence this is one magnificent timepiece with one of the best finishes and looks screaming pure 'haute horlogerie'. The new Arnold & Son Constant Force Tourbillon is available in a limited edition of 28 timepieces

Sticker Price $197,500 USD. For more info on Arnold & Son click here.