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Aviation History
1932
1932 - 0068.PDF
FLIGHT, JANUARY 22, 1932 The Savage Projector f—[|p^ HOSE in close touch with aero- (^ I nautical matters have known lor III many months that the new type of light projector being produced by Maj. Savage would, when the details of it were published, cause quite a stir, not only in aviation circles, but also among the tacticians of the Navy and War Office. That it would be such an advance over existing projectors, as it has turned out to be, was hardly anticipated. Maj. Savage is, however, not the type of man to stand still, and we have little doubt that, revo lutionary as it is, the present form of the projector is by no means the last word he will have to say on the matter. With the question of its use for adver tising by projecting the name of a com modity on the clouds we are not greatly concerned. That subject has already proved a Godsend to persons who make a habit of filling the correspondence columns of the general Press. It looks as if it might easily replace the older method of sky-writing by smoke emission if only on the score of weather, and for Naval and Air Defence uses there is not the slightest doubt about its utility. Naturally the apparatus may not be described in detail, but a brief description is now permissible. The model which we were recently privileged to examine was a mobile unit, and it is this type which would appear to have most uses for Air Defence. The unit consists of a Tilling-Stevens petrol-electric chassis upon which is mounted the projector. The engine and generator of this being of sufficient capacity to supply all the current that is necessary both for working the light and for driving the unit. It is thus completely self-contained and highly mobile. The chassis and the generating side of the outfit are standard, and, therefore, need no further description. The projector is most ingenious in every detail. As will be seen from the illustrations it consists of a barrel, the front end of which contains the source of light, while the rear end is purely the projector. The light is pro duced by a straightforward automatic arc lamp set in front of a very large parabolic reflector. The lamp, as would be expected, has many detail refinements which, together with the projecting part of the apparatus, accounts for the fact that candle-power available is 3,000,000,000, thus making it undoubtedly the largest projector in the world. The mirror reflects the rays parallel to the major axis of Major Jack Savage standing at the controls of his Projector. (FLIGHT Photo.) the barrel and towards the rear where they meet the image- plate, carrying on its face a large number of optical flats. These flats, in turn, alter the course of the light rays through 90 deg. so that they are extruded at right angles to the complete outfit. The flats form one of the most interesting points of the whole projector, for it is through them that the rays may be so emitted as to form a beam of any desired cross-section. Furthermore, the plate has flats on each side and can, by a very ingenious mechanism, be rapidly reversed, thus allowing the use of beams of either of two cross-sections within a short space of time. Readers will have already realised that the whole secret lies in the ability of this projector to extrude the main beam in a series of parallel rays. Moreover, the degree of divergence of this beam is obtained mechanically without loosing the parallelism of the individual rays. This means that the beam always maintains its maximum intensity and does not suffer through loss of illumination as does a projector where the divergence is obtained by optical means. Actually the total loss of light does not amount to 7 per cent., while, due to their parallel nature, the rays give a far greater range than is normally obtained. The barrel is mounted on roller bearings and may readily be trained by electrical means. In a similar fashion the projection end of the barrel may be rotated for elevation. The light can thus be directed at any desired spot. Due to the careful mounting of both parts of the barrel, the power required to turn them is very small indeed, and is On the left is the remote control box by means of which the beam may be turned in any direction. On the right it will be seen that the barrel comprising the lamp and projector has been trained round. (FLIGHT Photos.) 68
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