Raider Bathy 120 MemoDepth

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Raider Bathy 120 MemoDepth  - Favre-Leuba
3 minutes read
Tried and tested technique - and plenty of character

Imagine a misted-up dial, rusty gears and accuracy about as good as that of a raft on the high seas… Humidity is the sworn enemy of watchmakers, striking far more terror into them than even the bloodiest scenes in Jaws. Despite all that, in 1968 Favre-Leuba equipped its Bathy with a depth gauge that let seawater into the case. In 2018, the Raider Bathy 120 MemoDepth celebrated the 50th anniversary of this historic model and in doing so enlisted the many technical innovations achieved in the meantime. As a result, the MemoDepth can withstand pressures of up to 20 bar/200m while providing accurate measurement of depths down to 120m. And as a bonus, Favre-Leuba has added a new function to its ‘bathymeter’: memorising and displaying the lowest depth reached. 

From one extreme to the other 

The MemoDepth is one of the striking creations to have resulted from Favre-Leuba’s revival in the mid-2010s. Founded in 1737 (or even as early as 1718 according to some sources), the firm was family-owned for eight generations. It was subsequently severely battered by the quartz crisis, changing hands several times until 2011, when it was acquired by the Tata Group. Five years later, it was back in the limelight with decidedly sporty models. First of these was the Bivouac 9000, drawing inspiration from the Bivouac produced by Favre-Leuba in 1962, the first wristwatch to be fitted with an altimeter. Amongst others, it had graced the wrist of Junko Tabei, the first woman to conquer Everest. The watch featured an integrated aneroid barometer. Invented in 1844, this is a standard device in which atmospheric pressure distorts a sealed metal compartment containing a partial vacuum — but its inclusion in a wristwatch was both innovative and practical for mountaineers and aviators. Its contemporary version fitted to the Bivouac 9000 measures altitude and atmospheric pressure up to 9,000 metres, well above the Himalayas! In a move from top to bottom, the Bivouac 9000 was followed by the MemoDepth, featuring a depth gauge based on a similar mechanism. While they are at first sight opposites, the two watches share the same challenges: keeping the timepiece properly sealed and thus preserving the movement’s reliability, whilst at the same time intentionally using pressure from air and water — both of which are sources of humidity.

Raider Bathy 120 Memodepth

And yet it works 

There are indeed are apertures that let water in on the back of the MemoDepth — but not any old how. The liquid enters an ‘antechamber’, exerting pressure on a copper membrane fitted into the back of the case, while the membrane itself is fully watertight. The pressure distorts the membrane temporarily, increasingly so as the depth increases. This distortion is recorded by means of a mechanical contact sensor and passed on to the blue hands indicating the depth on the dial. The system ensures both the apparently contradictory properties of the watch are preserved: letting water in to measure pressure, without any unwanted flooding taking place. The measurements have been found to be perfectly accurate at depths down to 120 metres, whereas the original Bathy could go no further than 50 metres. The scale of the first 30 metres, a crucial range for decompression, provides more detailed readings, with red markers at 5 and 10 metres. There’s also is a device to protect the mechanism in the event of the diver going lower than 120 metres. The MemoDepth features another innovation required to calculate decompression stages, too, and it’s one that’s quite rare on dive watches: a display recording the maximum depth reached. This can be reset using a pusher at 4 o’clock. 

While the retro-futurist design of the MemoDepth is a nod to the Bathy of the late 1960s, that doesn’t stop it seeking to be effective as well. Form very definitely follows function here, as is notably evident in the generous 48mm diameter of the grade 5 titanium case, fit to withstand abyssal depths. The unidirectional rotating bezel is absolutely up to spec, too. Similarly, the display focuses on ensuring all the necessary information is as readable as it should be on a model with a ‘dive watch’ pedigree. Powerful luminous markings come into play if things get a little too dark. Who could ask for more when venturing into Neptune’s kingdom?

This year GMT Magazine and WorldTempus have embarked on the ambitious project of summarising the divers watch since 2000 in The Millennium Watch Book - Divers watch, a big, beautifully laid out coffee table book. This article is an extract. The Millennium Watch Book - Divers watch is available in both French and English here:

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