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Aviation History
1922
1922 - 0052.PDF
JANUARY 26, 1922 AERIAL LIGHTHOUSES 1,000,000,000-c.p. Lighthouse WE are able this week to give some brief particulars of the interesting aerial lighthouse that is being erected at Dijon in order to provide a suitable guiding light for the aerial routes between Paris and Algiers, Italy and Switzerland. This light, which is the largest and most powerful one in existence, was made by the famous French optical firm of Barbier, Bernard and Turenne of Paris, whose British representative is Major J. P. Ashley Waller of Audrey House, Ely Place, London, E.C.1. The range of this light in normal northern weather conditions will be about 65 miles, and in clear weather will be not less than 130, and more probably about 200 miles at a height of 6,000 ft. or thereabouts. The source of illumination is from powerful electric arcs, automatically adjusted and formed between horizontal carbons, which are surrounded by eight lenses, each composed of seven dioptric (refracting) and ten catadioptric (refracting and reflecting) parts. These lenses are so arranged that they divide into two groups of four, the axes of the two groups being opposed, and the beams from each group converge to form one large beam. This arrangement of lenses will be seen from the accompanying •diagram. A special point to be noted is that the lenses are split vertically at the centre. This splitting is a patented This particular light is intended for the present to give flashes at regular intervals, but, as it might be necessary to change this later on and to provide intermittent flashing of irregular periods, cams have been fitted which can be brought into play at any time to vary the length of flash and the intervals between flashes. The electric arc has been selected by the French Government for this Dijon light, as the necessary current is available in this case, but filament lamps could equally well have been fitted, with a considerable reduction in current consumption for the same intensity of light Powerful as this light is, we understand that the makers have full designs prepared for lights of even greater range, such as would be necessary for lighting desert routes when the number of lights employed should be kept down to a minimum. Where electric current is not available, as in the above case or Central Africa, etc., either acetylene gas or paraffin vapour would form the source of illumination, whilst automatic devices would be fitted which enable the lights to operate unattended over periods of many months. This automatic device, which is fitted on many marine lights erected all over the world by Messrs. Barbier. Bernard and Turenne, automatically fights and extinguishes the lamp at The Barbier, Bernard and Turenne Portable Flashing Aerial Beacon (4th Order). -device of the designers to enable the beam of light to take a greater speed vertically than horizontally, in order that the light may be visible outside and above the main beam. The arcs and lenses are carried on two platforms, two lenses of each group being on the top platform and the remaining pairs on the second. Below these platforms is a third, carrying a set of stand-by lamps, together with the necessary apparatus for bringing these into action and focus when required. All three platforms are connected, and, together with all the mechanism, revolve on a vertical shaft to which they are keyed. This shaft is mounted on ball bearings and stepped in a cast-iron socket which rests on a concrete base. An electric motor with reduction gear is fitted under the lower platform and serves to revolve the whole. Surrounding all the above is an 18-ft. diameter " house," the upper portion, opposite the lights, consisting of a double tier ventilated lantern; inner and outer galleries, with ladders, are provided for the crew. All the controls are fitted on the lower platform, whence every lamp can be inspected by means of special reflecting prisms, and its focus adjusted. any predetermined times, and is operated by the combined action of a clockwork motor and the flow of gas leading to the bye-pass—or an electrical device where electric light is employed. The whole gear is extremely ingenious, but lack of space will not, at present, permit a full description here. Briefly, however, it is composed of a clockwork movement with anchor release carrying a timing-box and timing disc divided into 24 hours, the last making one revolution per day. The timing disc carries two circular slots which engage two levers suitably disposed which open and close a valve controlling the gas supply. Winding of the spring is' effected by a gas motor driven by the gas leading to the bye-pass and working a ratchet driving the drum containing the spring. A gas pocket regulates the pressure and feed to the bye-pass. Gas from the main supply enters a valve beading to the burners, thence to the gas motor. The latter consists of a box containing a membrane, which is raised by the pressure of the gas, and in so doing operates a ratchet gear, which in turn winds the spring drum—a friction slipping device being, of course, provided. 5*
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