Mechanical watches have a certain relatable aspect that make them appeal to humans in a way that quartz watches cannot. If a screw is loose, we can understand how to tighten it. If debris is jamming a gear, we can imagine how to free it. That being said, most mechanical watches are designed following the movement's lead. What happens when you design a watch in the opposite direction, thinking about human interaction first? You get a Ressence watch, with no crown at all and an unbelievable, oil-immersed dial.
Ressence's founder Benoît Mintiens is not a watchmaker, rather he is an industrial designer with a particular focus on human interaction. Recently, we discussed the origins of the Ressence watch design, along with an in-depth look at how the time-indication module works.
Benoît and I discussed how shapes in nature are rarely flat, but instead are curved or rounded. The world is round and living creatures are never flat or square. The Ressence watch follows nature’s example with an organic case and dial that almost become one. The edges of the dial are curved, and the dial is curved as well. Flat surfaces can be analogous to “machine-made,” while rounded surfaces evoke a more “natural” feeling.
What is the quickest way for a human to read the time? An analog watch requires only a quick glance once you are trained, in comparison to a digital clock that needs to be read digit by digit. But watch hands overlap, making reading the time from a slight angle not ideal. Benoît’s idea was to let the dial’s hands all live on the same geometric surface level, for maximum legibility. But to do that, the hands could not overlap, yet they still had to rotate. The result is the fascinating dial that makes a Ressence watch so recognizable.
But how is that amazing dial really made? The vast majority of mechanical watches that we know and love are built using 2.5-dimensional architecture. Wheels overlap each other at different elevations, bridges hold things in place in a perfectly perpendicular fashion, and hands are anchored in the dial center at different heights in parallel layers. It is rare to see a mechanical watch with 3 dimensional architecture, mostly because it is difficult and complicated for watchmaking manufacturing equipment to produce true 3 dimensional shapes.
Ressence watches use a planetary gear system with eccentric bi-axial satellites, that allow even power transmission through a predetermined angle. (In this case, 3 degrees and 4.75 degrees.) Now what exactly is a planetary gear system with eccentric bi-axial satellites?
HODINKEE: What is beneath the dial of a Ressence watch that enables the dial to move in its unique way?
RESSENCE: In technical terms it is called a planetary gear system. You could describe it as set of gears rotating all together, in a similar way as planets would do in a solar system. They are powered by the rotation of the movement's center pinion. On a Ressence dial the different axles on which the gears are mounted are positioned with an angle. If you were to virtually stretch the axles of all the gears, they would meet at a common imaginary point 125 mm beneath the dial. The reason for this is that the dial is curved and the axles must be perpendicular to the curved surface. This imaginary point would be the center of the sphere if the dial was spherical.
HODINKEE: How are the different rotation speeds of the individual sub-dials achieved?
RESSENCE: To achieve the different time scales indicated by the dial (hours, minutes, days) the gears recalibrate time in other scales all driven by the minutes. The minutes “hand” is the leading hand on a Ressence dial. From there, the other time scales are generated
HODINKEE: How is the angular rotation of the planetary gear system done?
RESSENCE: The gears are produced like microchips for integrated circuits in electronics. They are molecularly built on silicium wafers using the LIGA process. The vertical walls of the gears have a slight angle due to the molecular build up process. When assembled the gears are positioned in such a way that the angle of the axle corresponds to the natural angle of the gears. In such a way the contact points between two gears is optimized.
HODINKEE: What was the design process for the planetary gear system like?
RESSENCE: It requires some brain exercise to calculate the planetary system. In fact the gears are continually compensating for the rotation generated by the minutes. For example to keep the indexes in a north-south position they need to compensate for 100% in the backwards direction. The weekday hand is compensated for 85.71% to obtain a relative forward movement of the hand induced by the minutes disc.
HODINKEE: Are there any particular challenges in assembling the mechanism?
RESSENCE: A Ressence Orbital Convex System (ROCS) has to be as light as possible. Components are milled in such a way they have a minimum mass by creating a 3D structure comparable to honeycomb. The assembly is a very delicate operation to make sure the jewels do not deform the thin walls. As all axles are under different angles, watchmakers need to work in three dimensions to do the assembly. This is somewhat unique in watchmaking. We created special tools to hold the components under precise angles when assembling.
Form follows function, and with Ressence watches functionality is built with humans in mind. My thanks to Benoît for the in-depth philosophical engineering discussion. Visit the Ressence website for more information on their unique watches.
Photographs courtesy of Andrew Morgan.