The Haute-Rive Honoris I Is A Flying Tourbillon With A 41 Day Power Reserve

Haute-Rive was founded in 2023 by Stéphane von Gunten, who before he went out on his own, was the research and innovation director at Ulysse Nardin; he was also, from 2005 to 2007, part of the team that developed the Spiromax balance spring at Patek Philippe. Haute-Rive’s first watch was released in September of that year and it was and is a remarkable piece of work – a flying tourbillon, bezel-wound, with an incredible 41 day power reserve, coming from a single mainspring barrel in a case just 42.5mm in diameter, and 7.75mm thick.

To understand why this is such a big deal, it helps to look at how very long power reserves typically happen in mechanical wristwatches. Generally, and there’s usually no way around it, to get a longer power reserve, you have to have a bigger mainspring. Beyond a certain point, however, using a single mainspring starts to present a major technical problem, which is that torque doesn’t stay even over a longer running time – an extra long mainspring will generate too much torque at the beginning of its power reserve, and too little at the end. (In modern watches with a running time of three or so days, this is usually not an issue as modern mainspring alloys deliver a pretty flat torque curve over that amount of time, and if it’s an automatic watch, the winding system acts as a sort of constant force mechanism anyway). However, if you really want to go for longer running times – a week, or even longer, you basically have two choices. One of them is to use a constant force mechanism like a fusée and chain, or, more likely, a remontoir (a fusée and chain take up a lot of room in a movement and for long running times you’re usually better off with a remontoir) which is what Lange does in the Lange 31.

The other solution is to use more than one mainspring barrel. Mainspring barrels can be mechanically linked in one of two ways: in parallel, where both discharge at the same time, or in series, where they run down one after the other. The first is usually used in watches which require more energy at the escapement, or which have power-intensive complications; the latter is usually used in watches where a longer power reserve is required. (There’s an excellent discussion of the differences over at the always reliable SJX). Lange actually uses two mainspring barrels running in series as well as a remontoire in the Lange 31. Watches with such long power reserves often have four or more mainspring barrels; the Quenttin Flying Tourbillon, which came out in 2006 (from, of all people, Jacob & Co.) was a flying tourbillon with seven mainspring barrels. It was also huge – 47mm x 56mm x 21.5mm – and until the Honoris came out, it looked like you were basically stuck with making a massively big watch if you wanted a very long power reserve at all.

The Honoris is a very different kettle of fish. It was inspired by the work of an ancestor of von Gunten’s; Irénée Aubry was a watchmaker who, in the 1880s, developed pocket watch movements with eight and 40 day power reserves. Honoris uses a single, three meter long mainspring which takes up the entire diameter of the case, and ordinarily, this would mean a very thick watch, but the gear train arrangement in the Honoris is designed to keep thickness to a minimum.

The tourbillon, escapement, and balance are driven by a great wheel at 12:00, which sits on top of a planetary differential; the wheel is turned by the keyless works to wind the watch and rotates in the opposite direction to drive the going train. The great wheel is driven in turn, off a transmission wheel on the back of the watch (which also has the power reserve) which is directly driven by the mainspring barrel.

This is a cutaway diagram of the Honoris. The lower half of the case is entirely taken up by the mainspring, and the upper layer contains the differential, great wheel, and going train. If you look closely, you’ll see that the gear driving the tourbillon carriage is actually at an angle, which allows the tourbillon to sit lower than it would otherwise in the movement.

Chronometry over the 41 day power reserve is a consideration, of course; when I first met von Gunten in Geneva in 2023, he said that Nivaflex mainspring alloys as well as the shape of the spring, in his view would make for satisfactory balance amplitude over 41 days, although he did note that some changes had to be made to the shapes of gear teeth in the going train to strengthen them against the considerable force the mainspring generates.

It’s without question, a fascinating watch from a technical standpoint (I would give a lot to monitor its performance over 41 days). It’s certainly set a record for power reserve in a flying tourbillon and it also has one of the longest power reserves in any wristwatch of any kind; currently, it’s exceeded only by the Hublot La Ferrari, which has a 50 hour power reserve, delivered by eleven mainspring barrels.

However, where the Honoris stands alone, is in its achievement of such a long power reserve in a watch that doesn’t feel like a clock on a strap, or like it was inspired by science fiction; instead, it’s a watch of real elegance, and made only using traditional watchmaking methods and materials. There are many watches with very long power reserves; there are far fewer that feel classically beautiful in the hand and on the wrist as well.

The Honoris I 41 Day Flying Tourbillon: Cases, 18k white gold, with openworked grand feu enamel dial; 30M water resistance, 42.5mm x 11.95mm. Sapphire crystals, AR coated, front and back. Movement, HR01 caliber, hand wound via a rotating bezel with single mainspring barrel with 3 meter long mainspring; flying tourbillon rotating once per minute; lever escapement, variable inertia balance wheel; 38.45mm x 7.75mm, running at 18,000 vph in 35 jewels. All bevels hand finished in the traditional fashion with gentian wood from the Jura. Matching 18k gold pin buckles. View the watch at The1916Company.com.