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Aviation History
1940
1940 - 0537.PDF
FLIGHT, February 22, 1940 a POWER- OPERATED GUN TURRETS A Review of Their Development by One Who Has Played a Leading Part V By A. FRAZER-NASH, M.I.A.E., A.M.I.Mech.E. IEWING the aircraft in service to-day, and more particularly the long-range bombers brist- The first Nash and Thompson power-driven gun turret was installed in a Hawker -• Demon. The gunner's shield was of "lobster shell " construction. ling with mechanically operated gun mountings, it seems the lowest possible drag on the aircraft. Unfortunately,almost incredible that when the designs of the modern gun turret were submitted to the British Government in 1932 it was not considered that there was any serious necessity for anything better than the old wartime ring mounting carrying a single free gun. During the last few years the speeds at which aerial engagements are fought have risen to such an extent that it has become quite impossible to lay and manoeuvre guns by hand, except in very limited fields of fire. Further, it is essential with these higher speeds to pro- tect the gunner from the air stream, and if a cupola is provided to do this, it must be so shaped that it imposes cupola shapes which have this low-drag characteristic usually need a high torque to turn them into positions for beam firing, and the combination of this torque and the torque due to the air drag on the guns themselves may amount to several hundred lb. /ft. With the multi- plication of armament or the use of larger guns, the forces are correspondingly greater still. This problem was becoming apparent in 1931, when the Hawker " Hart " type of machine was already show- ing that something better than a hand-mounting, with unprotected gunner, was necessary. As the heavy bombers were still incapable of speeds much in excess of 100 m.p.h., the only machine appearing to need serious alteration to its armament was the two-seater fighter. The speed of this type of aircraft had reached a point where the rear gunner was experiencing difficulty in laying his gun accurately, particularly when on the beam shot. There was also difficulty being experienced in that sudden acceleration due to aerobatics was liable to cause the gunner to injure himself unless he could remain seated at all attitudes of firing. I therefore started the development of power-operated gun turrets for this type of aircraft. An early decision that had to be made was the type of motive power to be used. The requirements were that the control should be accurate and sensitive, and require a minimum of effort to operate ; the apparatus had to be light in weight and have a consider- able reserve of power. It also had to be capable of instantaneous, smooth and con- tinuous speed, and of variation from full speed in one direction to full speed in the other; also, for any speed control setting, maintain more or less constant speed under great variations for even reversals) of mechanical load. Controls had also to be de- vised which would allow smooth and simul- taneous but independent movements in both the vertical and horizontal direction. The next stage in the development of the Nash and Thompson power-driven gun turret can be seen in this picture of the tail of a Handley Page Harrow. Flight " pi
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