When the Tag Heuer Monaco V4 project began to take shape in 2002, the design team followed the speedy rise in the popularity of the tourbillon and recognized that it still depended on channeling power from the barrel to the escapement through pinions and gears. After its primary brainstorming sessions, TAG Heuer’s design team had the chance to work with a few leading innovators in 3-D animation and particularly with lean-Francois Ruchonnet, whose specialization is micro-mechanics. The team fell in love with the thought of creating a movement patterned after a V4 engine, having four spring barrels and a rectangular winding mass that induces a linear movement. They considered that the traditional rotor that supplies the winding power for a lot of automatic watches conceals the movement. In their pursuit for innovation, the design team found as though they were creating a supercar engine. Rather than using gears and pinions to convey the power from the spring barrels, they chose to establish watch history by using toothed, V-shaped drive belts. To bring the V4 concept further they put on the four barrels in a V-shaped configuration, sloped at 13° to the main plate. Using the new concept it is possible through the case-back to view the barrels, the drive belts and the linear skidding weight that powers the watch. Being their practical function, these have also turned into a major design feature.
Throughout the development years the design team got together with a unique international network drawn from celebrated high-tech companies, research institutes and universities. The processes used in the design, prototyping and production of the V4 are similar as those utilized to design complex aerospace systems. Techniques, tools and expertise were derived from an eclectic merger of disciplines like the automobile and IT industries, chemistry, applied mathematics, climatology, micro-mechanical sciences and computer engineering. Mr. Linder explained “In 2004 we set up a big development team and its methodology was to create synergies between different specializations. We hired Guy Semon, a top engineer from the aircraft industry and a high-tech engineering team. When you make a watch you can produce a number of prototypes, but when you build a plane like an Airbus, it has to fly first time. Having put together this high-tech team, we rented a supercomputer to make endless calculations before making the first prototype. It had to solve 1,700 equations to resolve unknown factors. Things such as the size of the wheels and the weight of the winding mass were all calculated by the computer. “We decided that we needed micro-torque to operate the escapement with precision. The drive belts that we had decided to use presented the biggest challenge. The original belts we used were far too fat, because we wanted them to be a clearly visible design feature. The only major compromise from our original concept was that we had to reduce the thickness of the belts. The energy required to bend the belts needed to be much lower than the energy needed to drive the escapement.”
In time a number of belts of different thicknesses were utilized in the Tag Heuer Monaco V4: those closest the escapement had to be the most pliable – and thinnest – and those nearer to the power source have to be increasingly stronger, and so they had to be reinforced using steel. The belts used for the prototype were laser cut using a nanometer wavelength that takes away just molecules at a time. Computer calculations had outlined the dimension of each belt and the kind of material it should be created from. Linder explains, “There was only one material in the world with the properties we required – a type of polyamide. “The more molecules you add to the polyamide the more you change its properties.” “We use four different formulae to achieve the specific properties we require for each belt. The belts have very good friction properties and don’t need to be lubricated.” For the production models, the belts are done by a special micro injection molding procedure. To create toothed drive belts, a few of which are as thin as a human hair, the material has to be injected at really high pressure. The drive belts utilized in a Walkman or a CD player are ten times as thick compared to some of the belts inside the V4 movement “One bonus of using drive belts instead of wheels and pinions is that they provide extra resistance to shock. The Monaco V4 watch is extremely shock-resistant: it can withstand shocks up to 5,000G.” The employment of drive belts also brings out another phenomenon. In a motion that uses pinions and wheels, every wheel in the train turns in the opposing direction to adjacent wheels; using drive belts, linked wheels constantly turn in similar direction. The utilization of V-shaped drive belts has helped us to produce an innovative design that is indeed a work of art. We have polished up the wheels, but we haven’t used cotes-de-Geneve ornament on the bridges, to achieve a really modem look. “Another benefit of using drive belts is that they enable us to spread the movement out and allow for much more flexibility from a design point of view. Using drive belts makes it much easier to change the location of items such as sub-dials for instance than when using gears and pinions. The back of the movement has a fantastic shape: it is thinner at the edges than in the centre – similar to a V4 engine. The spring barrels are mounted in pairs and receive their energy from the linear sliding weight via a collector wheel.” One slight disadvantage of belts compared to traditional gears is that they cannot achieve de-multiplication at the same rate as gears because they cannot be bent too sharply, but the benefits of their shock-absorbing properties outweigh this disadvantage. The first prototypes, as shown in Basel in 2004, only ran for a short time and the drive belts extended as far as the balance wheel, but this was changed later. The belts on the first prototypes were used in different places compared with today’s finished models.”
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