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Aviation History
1938
1938 - 1041.PDF
APRIL 14, 1938. FLIGHT. A 20 mm. Oerlikon canon (or, as Flight prefers to Anglicise it, shell-gun) on the new mounting. FOR FREE devices actuated by oil pressure, air pressure, and electricity. Fig. 1 represents the main features of the oil pressure device. The electric motor i drives an oil pressure pump which feeds the traversing and elevating mechanism. The traversing device is actuated by the oil pressure pipes A and B leading from the pump to the oil pressure motor 2 which works for- ward or in reverse, according to whether the oil enters by A or B. The return pipe is marked C. On the axle of the motor is a drive for the pinion 3; when this latter is brought into contact with the teeth on the fixed ring traversing takes place. Elevation is controlled by the pipes D and E, which lead to both sides of the piston 4 in the cylinder 5. The piston rod 6 is, of course, linked tt> the gun cradle, providing the up and down motion. Operation of the control marked 7 meshes the traversing pinion and at the same time connects pipes D and E to the pump. On the horizontal control board is a lever which the gunner holds in his right* hand and which is the central control for traversing and elevating. This lever controls the oil pressure SHELL-GUNS An Oerlikon Aircraft Mounting with Electrical Drive JIE difficulties occasioned by the mounting of fixed shell- guns on aircraft are rather overshadowed at the moment by problems associated with " free," or movable, in- stallations. Various armament concerns have been wrestling with these problems, and details of a mounting de- veloped by Werkzeugmaschinenfabrik Oerlikon, Zurich- Oerlikon, Switzerland, for the FFS model of 20 mm. gun have lately been released. Essentially, the mounting comprises a fixed ring, mounted on or in the aircraft structure, on which revolves a second ring. Fig. 1. Traversing and elevation. T Fig. 2. Firing controls. supported by ball bearings. The revolving ring has two ver- tical walls which carry the gun cradle. Also associated with the revolving ring are the gunner's control board and his seat. A pinion, hydraulically driven, revolves the ring; the elevating gear is essentially a piston and hydraulic cylinder. The entire traversing mechanism works on the revolving ring and comprises pump through the intermediate gear marked ia on Fig. 1; movement to the left or right revolves the ring in .the appro- priate direction, while easing it forward or backward lowers or raises the muzzle. The compressed air device for cocking and firing is shown in Fig. 2. This has a three-fold purpose: if the gunner opens the valve 1 compressed air fills the cylinder 2, the piston of which cocks the recoil spring of the gun; if he presses with his thumb on the button on the main control lever, compressed air oper- ates the trigger, and at the same time the blocking mechanism marked 3 comes iofo operation, so that any movement of the ring is arrested during firing. The cradle is also locked. The electric moto: (24 volts) is started by an auxiliary lever on the main control handle, so that the gunner's fist grips it automatically.' In critical moments a special button can be pressed which, causing the motor to revolve faster, accelerates the traversing and elevating movements. Data on the mounting (which, of course, is intended to have a turret top) are: Elevation range, —10 to + 90 degrees; traversing range, 360 degrees; weight of turret without gun, 1.87 cwt.: electric current consumption at 24 volts, 15 to 20 amps.; maximum speed of traverse, 36 degrees a second; maximum speed of elevation, 25 degrees a second. A BOOK ON ELEKTRON ELEKTRON," a finely produced and illustrated text bookhas been compiled by the producers, suppliers and manufacturers of Elektron magnesium alloys. Extensive data on the composition and properties of eafn alloy are contained in the book, and chapters deal with the "rigin, development and actual applications. The frontis- piece is a photograph of the D.H, Albatross, in which Elektron >s used extensively. The price of the book, which may he obtained from the producers of the alloys, is 10s. 6d. Elektron alloys are in the hands ol seven firms: Magnesium Elektron, Ltd., of Clifton Junction, Manchester, are sole pro- ducers; F. A. Hughes and Co., Ltd., are suppliers; and Sterling Metals, Lid., Coventry ; J. Stone and Co., Ltd., of Deptford, London; and the Birmingham firms, James Booth and Co., Ltd ; Birmingham Aluminium Casting Co., Ltd.; and Birmetals. Ltd., are licensed manufacturers.
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