Favre-Leuba Bivouac 9000
Bivouac 9000 is a wristwatch by Favre-Leuba.
The expedition watch from 1962
1962 Favre-Leuba launches the first model of the Bivouac, the world’s first mechanical wristwatch with aneroid barometer, for altimetry and air pressure measurement. The Bivouac achieves one of its first missions on the wrists of the Swiss national parachuting team during the 1962 World Cup in the United States. The Italian mountaineer Walter Bonatti wears a Bivouac in 1964 when he and the Genevan Michel Vaucher successfully ascend the north face of Pointe Whymper (4,196 m) in the Grandes Jorasses for the first time and when he conquers the north face of the Matterhorn on the most direct route. The young Michel Darbelley from Wallis undertakes his first solo ascent of the Eiger in 1963 with his watch from the workshops of Favre-Leuba, which reliably shows him what altitude he has already scaled and whether a change in weather is imminent. The well-known French polar explorer Paul-Emile Victor relies on his Bivouac on numerous expeditions to the endless ice.
2017 the Bivouac 9000 is presented as re-edition, which can now indicated heights till 9,000 meters. Thus all summits which mountain climbers can ever reach are within its range.
Functional description
The red central hand indicates the altitude on the bidirectional rotating bezel, which carries a scale divided into 50-meter steps, up to 3,000 meters. One full clockwise rotation of the red central hand thus indicates a climb in altitude of 3,000 meters. During a climb, the small red hand of the subdial located at 3 o’clock continues to turn too, until, after three full rotations of the central hand, it arrives at its final destination of 9,000 meters above sea level. The bezel is held securely in place by a two‑way ratchet mechanism that prevents it from being unintentionally moved to a different position.
The heart of the barometer is an airtight capsule made from a special alloy. The capsule expands when the air pressure drops as the wearer climbs and contracts when the air pressure rises during the descent. The expansion and contraction of the capsule triggers a linear movement, which is then converted into a rotational movement to indicate the altitude. The altitude is made visible by the red hands on the stone-gray dial. The atmospheric air that is required to measure the altitude enters the chamber containing the barometer capsule through a three‑millimeter opening in the case, which is protected by a perforated membrane.
The Bivouac 9000 is also capable of displaying any changes in air pressure at the same altitude. The hectopascal (hPa) scale on the subdial located at 3 o’clock displays the current air pressure on a scale ranging from 1,013 to 300 hPa. If the climber sets the watch to the correct height of the Matterhorn base camp on the evening before the ascent, the small red air-pressure hand opposite the altimeter hand will be pointing to approximately 680 hPa – the average air pressure at this altitude. Should the air pressure drop during the night, the central hand will turn clockwise and the small air-pressure hand will be pointing to a lower value the next morning. This means the ambitious climber is now in an area of low pressure – the weather has worsened. In extreme weather conditions, for example if a storm is approaching, the difference between the actual and average air pressure can be as much as 150 hPa. However, if the central hand has turned anticlockwise and the small air-pressure hand is pointing to a higher value than it was the previous evening, this indicates an area of high pressure with improved weather conditions surrounding the Matterhorn. With its ability to provide such information, the Bivouac 9000 is an important instrument that helps climbers decide whether or not they should attempt the dangerous ascent or postpone it until another day.