Monochrome Watches
An online magazine dedicated to fine watches

Logical One by Romain Gauthier

| By Frank Geelen | 6 min read |

Romain Gauthier is one our favorite watchmakers and belongs to the few very best watchmakers of our little blue planet. And now he comes with something that tickles us in many ways: a new constant force mechanism. 

Romain Gauthier’s new timepiece, Logical One, is one that will not only tickle us, but I’m sure many people who’re fond of real Haute Horlogerie will just LOVE this. Logical One features a flat chain-and-fusee style constant force system with ruby chain links, ergonomic push button winding system, dial-side visible balance, mainspring barrel with sapphire inserts, plus a 60-hour power reserve indicator. That’s a moth-full… so let’s take a closer look.

Romain Gauthier Logical One

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If you’ve followed Monochrome, you know we just love constant force mechanisms. The Tensus made by Heritage Watch Manufactory is just one example, another example by Girard-Perregaux will be launched at Baselworld. But what is all this talk about constant force?

The vast majority of machines run on constant force: Cars and planes don’t start running slower as fuel runs low and machines receive the same voltage no matter how much electricity is produced. Yet the power that runs and regulates the vast majority of mechanical timepieces varies greatly according to the tension of the mainspring.

Romain Gauthier: “Coming from an engineering background, it appeared strange to have a high precision machine forced to run at varying power levels. So I started with the premise that it would be better to have constant energy.”

Constant force is one of the holy grails of horology and with Logical One, Romain Gauthier has reinvented the chain-and-fusee − one of the oldest and most traditional methods of supplying constant force to a watch/clock movement − making it both more reliable, more effective and more constant.

Chain and fusee

One of the most traditional ways to achieve constant force is the chain and fusee. A fusee (‘fusée’ is French for cone) is a cone-shaped pulley wound with a cord or chain that is attached to the mainspring barrel. The complicated construction was used mainly in the high-precision marine chronometers as well as in the scientific pocket chronometers.

When the mainspring is fully wound and thus exerts great force, the chain pulls at the smaller radius of the fusée where the leverage is smaller. As the spring’s tension diminishes, the chain pulls at the larger radius with the higher leverage. Thus, regardless of the state of wind of the mainspring, the same amount of torque is delivered to the escapement, resulting in improved rate accuracy.

According to Romain Gauthier, the traditional chain and fusee has two problems:

  1. The multiple layers of chain (often eight turns) on the fusee mean that the individual links have to be small, which means that they are relatively weak.
  2. The chain is often transmitting force between the fusee and mainspring barrel at an angle, which is both inefficient and adds stress.

Romain Gauthier solved both problems by replacing the fusee with a slowly rotating snail cam. Because the snail cam and mainspring barrel are on the same level, the force is always transmitted in a straight line and, as only one short line of chain is needed, the links can be bigger and stronger.

Romain Gauthier Logical One

To further improve efficiency, Romain Gauthier has taken full advantage of the larger chain links by making the links in low-friction hard-wearing synthetic rubies.

Both other watch models from Romain Gauther, the HM that he launched in 2007 and the HMS that was launched in 2010, feature a winding wheel placed in the case-back. A push button in the left caseband functions as an ergonomic winding system. Romain Gauthier makes it possible to wind the Logical One by simply pushing the push button.

Romain Gauthier Logical One

A traditional crown is relative small with a fine (relatively fragile) stem that has to transmit the force 90° between the crown to the mainspring barrel. The pusher to wind Logical One transmits force to the barrel on the same plane.

Another improvement cannot be seen, because it’s inside the main spring barrel. Sapphire plates are placed above and beneath between the mainspring and the inside of the barrel.

As the mainspring unwinds in a traditional brass barrel, the metal of the spring scratches the metal, even when freshly greased. Over time, grease clots, scratches get rougher, the barrel sticks to the spring and does not rotate smoothly. The sapphire disks have the ideal properties a low coefficient of friction with steel (a reason why watch movements have ruby bearings) and is highly scratch resistant.

Romain Gauthier Logical One

As I said in the first lines of this article, Romain Gauthier belongs to the very best watchmakers in the world. The design of the movement is sublime and the details are simply jaw-droppingly beautiful. To name just a few details:

  • Bespoke gear wheels with graceful circular arms for maximum rigidity
  • Special power-process hand frosted bridges
  • High efficiency gear teeth profile (patent pending)
  • Polished screw heads with distinctive S-slot for more length/less slip
  • Balance wheel with curved arms and calibrated eccentric weights
  • Triangular pallet lever (Romain Gauthier invention) for improved rigidity.

The movement for Logical One was entirely conceived, developed, designed, produced, decorated, assembled and regulated by Manufacture Romain Gauthier. Highly polished sharp internal bevelled angles in the movement plates and bridges; this finishing can only be done by (a very skilled) hand because, to date, machines are not capable of milling and polishing sharp internal bevels. With Logical One, Romain Gauthier has gone a step further still in creating double-angle bevels (two parallel bevels) with sharp internal angles, which give the effect of border.

Romain Gauthier Logical One

Just look at these detail… the stunning double-angle bevels, the customs wheels, the polished balance wheel with its calibrated eccentric weights, the ruby chain links and I can go on… so gorgeous!

Romain Gauthier Logical One

The Logical One comes in either red gold or platinum and measures 43 mm in diameter and 14.2 mm in height. The movement offers 60 hours of autonomy, when fully wound. Winding is done by a push button in the left side of the case and setting is done by a crown, with sapphire cabochon, that is located at the 2 o’clock position. Three patents are pending.

Logical One – Technical Specifications

  • Features: hours, minutes, small seconds, 3-day power reserve, push-button winding and innovative chain-and-fusee style constant force system
  • Movement plates and bridges: titanium, stainless steel, brass
  • Number of jewels: 30 in movement, 34 for chain
  • Number of components: 333
Balance frequency: 28,800 bph / 4Hz
Highest level haute horlogerie finishing, including hand polished screws and jewel countersinks; hand bevelled and polished bridges and plates.

Romain Gauthier Logical One

For the price, please contact Romain Gauthier through his website or ask at one of the authorized dealers. Here’s a link to Romain Gauthier’s website. And if you like to read more about the history and functioning of the traditional chain and fusee, I can recommend to read this page at Wikipedia.

This article is written by Frank Geelen, executive editor for Monochrome Watches.

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