The third choice is what Arnold & Son selected: it’s to use a remontoire. The watch has two mainspring barrels that are mounted in serial. One of them powers the gear train; the second provides a buffer store of energy. Any time the first barrel’s torque falls below a certain point of consistency, the second barrel tops it up. This keeps the rate consistent through the 90 hours of the Constant Force Tourbillon’s power reserve.
2. The constant-force mechanism is connected to the true-beat seconds hand.
Arnold & Son is proud of its use of the true beat, or deadbeat, seconds hand. This mechanism means that the seconds hand moves exactly once per second, starting and then stopping dead sixty times in a minute. It’s an old feature and a throwback to the days of John Arnold, the company’s namesake. But it also is very hard to accomplish. In 2013 I spoke to Arnold & Son’s technical director, Sebastien Chaulmontet, about the complexity of a deadbeat seconds hand, and why the brand frequently uses them:
“A deadbeat is always complicated. … What you have to imagine: while a quartz watch is very easy, it gets an impulse every second. But with [a mechanical watch] it’s very different, because you are stopping and starting something which is moving. … The bigger it gets, the more weight you have to accelerate and stop. And it beats 36 million times a year. So it’s really a tremendous wear-and-tear problem you have to solve. Because it’s functioning all the time. It’s jumping and releasing energy and braking every second. … Even a chronograph, once you push it, it just runs. But you’re not stopping and starting your chronograph every second all day long. But basically it’s what a deadbeat is doing. It’s stopping and starting itself all day long, and you cannot stop it.”
In the Arnold & Son Constant Force Tourbillon, the deadbeat is directly connected to the constant-force mechanism. The power off of the mainspring barrels doesn’t run directly to the escapement or to the tourbillon. Instead, it goes to a smaller hairspring, which supplies a fixed amount of power to the escapement once per second. This not only regulates the flow from the mainsprings to the balance: it also is the perfect rate to power the deadbeat seconds hand. That’s why you can see the seconds hand at 7:30: it sits directly atop the constant-force mechanism. Here’s what the mechanism looks like:
3. If you see a cosmetic resemblance to an earlier Arnold model, you’re not wrong.
The symmetrical, skeletonized layout of the Constant Force Tourbillon gives quite a view: you can see the two barrels at 10:30 and 1:30, the tourbillon at 4:30, and the constant-force mechanism at 7:30. Both the top and bottom pairings have matching palladium-treated bridges to hold them in place, with mirror-polished heads on the screws. For the discerning Arnold fan, this dial arrangement is a descendent of the TB88, which the brand first launched in 2011. That watch used manufacture caliber A&S 5003 and had a distinctly different set of characteristics, but the resemblance is definitely there. The two watches may even share a case: the TB88 and the Constant Force Tourbillon are among the few Arnold & Son watches with a sizeable 46-mm diameter. The Arnold & Son Constant Force Tourbillon comes in a rose-gold case.
The Arnold & Son Constant Force Tourbillon is a limited edition of 28 pieces, all in rose gold. It has sapphire windows on the front and back. Its movement, A&S 5119, is a new caliber for the brand. It is manually wound and beats at 21,600 vph. It has 39 jewels. The watch is water resistant and comes on a brown alligator strap. Each watch costs $197,500. We snapped a few photos of the Constant Force Tourbillon at our meeting with Arnold & Son at Baselworld. Below you can see the front, back, and what it looks like on the wrist.
This article was originally posted on March 24, 2015, and has been updated.