THE WATCH WAS MADE TOGETHER WITH RÖJDIVERS AND IS MALMS' FIRST DIVING WATCH. IT IS A ROBUST DIVING CARTRIDGE EQUIPPED WITH AN ANALOGUE DEPTH GAUGE AND DEVELOPED TO WITHSTAND MILITARY DIVING REQUIREMENTS.
The Röjdikarklockan project began in the fall of 2019 and is based on an ambitious initiative between MALM and members of the 44. Röjdikadivisionen in Skredsvik, belonging to the 4e Naval Battle Flotilla. The mission is to produce a solid and reliable Swedish diver's watch, which has been fully developed based on the needs of Swedish clear divers and experience from the toughest possible diving missions.
Clear diving as a function was introduced in the Swedish Navy in the 1950s under the leadership of Captain Rolf Hamilton. Initially, the purpose of this elite unit was to conduct national mine and ammunition clearance operations at sea. Today, the operation is broader than that with the majority of international mine clearance missions on land, in the border area between land and water and under the water surface.
The name FROGDIVER 44 refers to the concept of 'Frogman', the English word for clear diver and the number 44 refers to the size of the watch in diameter and 44. The Clear Diver Division. FROGDIVER is, in addition to the Swiss movement from Sellita, designed and developed from the ground up by clearing divers and MALM. The watch combines details from current and previous diving equipment with a performance and user-friendliness demanded by the clearing divers themselves. Shapes, colors and materials are carefully selected to be able to be used in cold, dark Swedish waters where instruments and equipment are exposed to great stress.
ANALOG DEPTH GAUGE
The principle of using Boyle-Mariotte's law through so-called capillary meters is historically a well-proven method for reading what depth you are at while diving. The capillary meter has no moving parts but consists of a pipe/tube/channel that has an opening at one end and is closed at the other. During diving, water enters the tube and forms an air bubble that moves along a scale with the pressure change that occurs during descent.
In the Frogdiver, such a capillary meter has been installed in the construction of the diver's watch. At the 9 o'clock position, water is led down into the capillary tube via a hole drilled through the thick sapphire glass. When the watch is exposed to the pressure change that occurs during descent, the air bubble moves clockwise along the tube. Next to the tube is a scale against which the air bubble is read and which shows the depth the diver is at. This innovative and analogue solution has been developed by MALM in consultation with Röjdykarna as a complement to modern and digital diving equipment.
The dial in FROGDIVER uses several different components and colors to facilitate legibility in daylight and darkness. The dark background of the dial provides a clear contrast against white seconds markings in luminescent blue. Raised indices have been coated with white BGW9 luminous compound with a mounting bridge for tritium rods.
In the dial there is a round mirror loop that enhances readability against the clock's minute and second hands. The mirror also reflects the light effect from the tritium rods and the BGW9 printed indices in the dark. The inspiration for the mirror comes from measuring instruments in the recompression chamber "Gullan" which are used when divers are exposed to diving sickness.
LUME & TRITIUM
In order for an analogue, mechanical watch to be easy to use in the dark and cloudy diving waters found in Sweden, the best possible legibility is required. The solution is usually to use some form of luminescent material that has been printed or glued to the clock face. Light masses come in a variety of shapes, colors and shades and perform at varying levels in strength, effect and length. Common to all light masses, regardless of design, is that they need to be charged by a light source. Sometimes sunlight or daylight is enough, or a strong, close light from, for example, a flashlight is required for the luminous mass to light up.
In order not to impair the diver's sensitive night vision with the glare from a flashlight, one is careful to shine the flashlight close to the body and eyes. When the luminous mass has fallen and stopped shining, this can be a problem for the diver. As an alternative, so-called tritium rods are available. Tritium is a radioactive isotope of hydrogen (hydrogen with two extra neutrons) and is known in the watch world for its usefulness and luminous effect in the dark as it glows of its own power. Tritium is (usually) manufactured and exists in a relatively unstable gaseous form that strives to reach a more stable gaseous form, in this case an isotope of helium. It is this process of decay from hydrogen to helium that creates the energy used to drive a light effect.
Tritium used for wristwatches is encapsulated in small tubes/rods of sealed glass. On the inside of the glass is placed a surface with phosphorescent paint that has the ability to absorb the energy emitted by tritium and emit it as light. Phosphorescent paint comes in different variants and looks, so you can choose different colors for the lighting effect. Furthermore, there are varying qualities of tritium tubes, where higher tritium qualities usually mean that the glass tubes contain a greater amount of tritium. Since you cannot see the decay of the tritium substance, you are dependent on the phosphorescent paint's capacity to take advantage of the extra amount of energy that using a larger amount of tritium means. In this way, the amount of tritium and the quality of the color are linked in order to achieve a strong lighting effect.
The ability of tritium tubes to glow for a long time in the dark makes them very popular and useful in an analog diving watch. It is important to bear in mind that the capacity/light effect deteriorates over time because the tritium substance continuously decays - somewhere after about 5-8 years the deterioration is considered to be noticeable. As a rule, you don't replace the tritium tubes or "fill them up", but in that case the entire dial is replaced with a new one. All handling of tritium, from manufacturing, assembly, storage and sale, requires permission from the Swedish Radiation Safety Authority and must be handled very carefully by an approved radiation protection expert function.