Early RFC/RAF Open Gun Mountings

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Robert Hurst
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Early RFC/RAF Open Gun Mountings

Post by Robert Hurst » 02 Apr 2003 14:01

Hi

The Scarff Mounting

The Scarff ring was the first British attempt to provided the air gunner with an observer's gun mounting giving 360 degrees traverse and an assisted elevation system. A similar gun ring had been patented in December 1915, but Warrant Officer F.W.Scarff of the Admiralty Air Department designed a gun ring which was to remain in service for many years, being adopted by several air forces before being replaced by enclosed turrets in the late 1930s. The 'Scarff No.2 Ring', as it was officially known, entered service in July 1916, giving gunners a much-improved field of fire and enabling guns to be trained with far less physical effort.

The Scarff ring consisted of two steel rings, one fixed to the top longerons of the aircraft structure, and the other being supported on the fixed ring by ball bearings, and free to rotate. A tubular arch-shaped gun support tube was fitted to the upper moving ring, each end of which was joined to the ring by a hinged bracket, allowing it to move up and down. The Lewis gun was clipped into a socket at the top of the support tube allowing free travel of the gun. The arched support tube could be locked into any position of elevation by the operation of a lever fitted under the top centre. The lever operated a Bowden cable which engaged pins into slots cut into quadrant plates on both sides.

The gun and support arch were counter-balanced by strong rubber cords which, when the lever was operated, carried the arch upwards to whichever position gave the gunner a suitable line of sight, giving an immediate and weightless means of elevation. The cords, known as 'Sandow Cords'. were usually disconnected when the ring was not in use.

The Scarff ring was sometimes fitted with twin Lewis guns to improve the rate of fire. This mounting, known as the 'Huntley and Palmers' (after a well known brand of biscuits) was effective, but manipulation was more difficult. When not in use the gun could be lowered and locked into position along the top of the fuselage, allowing free movement for the observer's other duties.

The text and drawings were taken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke. The photo was taken from "Armament of British Aircraft 1909-1939", by H.F. King.

Regards

Bob
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Robert Hurst
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Post by Robert Hurst » 02 Apr 2003 15:02

Hi

In the late 1920s some aircraft manufacturers fitted gun rings of their own design, which were usually more compact than the Scarff ring, and featured several new ideas. One of these companies was the Fairey Aviation Co. Ltd, Hayes, Middlesex.

The Fairey High-Speed mount

The following description of the Fairey high speed gun mounting was taken from "Armament of British Aircraft 1909-1939", by H F King.

The Lewis gun is carried over the rear cockpit on a Fairey high speed gun mounting. This is a complete detachable component which fits over the rear part of the of the gunner's cockpit. The main support is given by the top longerons, each of which provides two connections. The main member of the mounting is a transverse steel tube which spans the longerons and has its ends held by clips. At each end of the tube is a quadrant and arm which lie inside and parallel to the longeron to which the arm is attached at its rear end. Between the quadrants an outer tubular member is placed over the transverse support tube on which it can rotate and can be fixed in any one of several positions by spring-loaded pins that engage holes in the quadrant framework. The ends of the outer tube are joined by a semi-circular ring which swings with the tubular member and is drilled with a series of holes. The position of the ring will therefore be determined by the pins that engage the side quadrants. At the centre of the transverse member an arm is pivoted, the arm lying against the semi-circular ring along which it is constrained to move by a slidnig bearing. The position of the arm on the ring may be fixed by a spring-loaded pin that enters one of the holes of the ring. The arm is continued beyond the ring and its free end carries the Lewis gun, with the standard pin connection. Between the gun and the swinging ring a hand-grip is fitted to the arm. with a finger guard on one side and a release lever on the opposite side of the grip. The operation of the lever releases the locking pin in the ring and by means of cables inside the arm and transverse tube, it also releases the pin in the quadrants, thus freeing the mounting.

The weight of the gun is counterbalanced by springs housed inside the mounting members. The spring for the elevating movement lies within a tube which forms the lower part of each quadrant arm, and the azimuth movement operates a spring inside the transverse tubular member. Each spring is adjustable for tension by turning a nut by a box spanner inserted in the ends of the spring housings.

When the mountings are erected by the manufacturer, the springs are balanced and set to the correct tension. If it is necessary to alter this setting, both springs of each pair must be altered by the same amount, which may be judged from the number of turns given to the adjusting nuts. The spring loads will tend to centralise the gun arm transversely and cause it to pass to its foremost position, ie, the arm will swing from rear to front in elevation. When the mounting is in any other position the hand-grip release must not be operated unless there is a gun on the mounting. The ammunition is carried in six Mk II No.2 magazines, each holding 97 rounds, five of the magazines being accommodated on pegs in the rear cockpit, with the remaining one on the gun. On the starboard side four pegs are arranged; the other peg will be found on the bulkhead separating the two cockpits.

The top photo wa staken from "British Aircraft Armament Vol.1: RAF Gun Turrets", by R Wallace Clarke.

The bottom photo was taken from" Armament of British Aircraft 1909-1939", by H F King.

Regards

Bob
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Robert Hurst
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Post by Robert Hurst » 03 Apr 2003 10:55

Hi

Another aircraft manufacturer to venture into the field of designing their own gun mounting, was the firm of H G Hawker Engineering Co. Ltd, Kingston, Surrey.

The following description of the Hawker ring-mounting is taken from "Armament of British Aircraft 1909-1939", by H F King.

The Lewis Mk III gun is carried over the rear cockpit on a special gun ring of the manufacturer's own design. This consists of a rotating ring carrying ten vertical and ten horizontal rollers which run on a second ring fixed to the cockpit decking. Both rings are aluminium-silicon castings. The rotating ring is formed with a varying depth of section so that its bottom surface provides a cam contour on which run two spring-loaded rollers. The rollers are deflected to their lowest positions and the spring consequently fully compressed when the gun is in its aftermost position, and the cam contour is so formed that as the gun ring is rotated either way from due aft the rollers exert on it a progressively greater deflecting force which serves to balance the air forces on the gun due to the slipstream. The adjustment of the spring tension should not be interfered with as a very small reduction in its effective length would cause blocking of the spring and consequent failure of the tension rod.

The gun elevation gear consists of a tubular steel arch hinged to the rotating ring and located in the desired position by stop pins engaging with quadrants. The stop pins are actuated by the normal type of lever on the arch through Bowden wires to a cam and tappet mechanism, which also operates the locking pins for the rotating ring. The weight of the gun is balanced by elastic cord loops. The ammunition is carried in eight Mk.II No.2 magazines (97 rounds), seven of the magazines being accommodated on pegs in the rear cockpit and the remaining one on the gun.

Another manufacturer to design a ring mounting was the firm of Barr & Stroud. Only the manufacturer's drawings for this design are available.

The two photos were taken from "Armament of British Aircraft 1909-1939", by H F King.

Regards

Bob
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Korbius
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Post by Korbius » 03 Apr 2003 12:35

Great info Robert, thanks for sharing

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Robert Hurst
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Post by Robert Hurst » 14 May 2003 11:04

Hi

The Westland Westbury, Rotating Front Gun Mounting

The Westland Westbury had two gun stations with provision for a 37 mm (1.46 in)* (see notes) Coventry Ordnance Works (C.O.W)+ (see notes) gun, the gun in the nose being on a special Westland (later Vickers-Westland) rotating mounting which allowed all-round training.

The gun was mounted at the apex of a pyramidal structure formed of tubes comprising a tetrahedron, the base tubes of which were connected at their apices to a central pivot by radial members, the apices being constrained to rotate about the pivot by shoes guided on a fixed base-ring.

The mounting could be fixed in any position of training by a brake pad which was urged into engagement with the ring by a spring operating to rotate an eccentric shaft carrying the brake pad. The pad was released to free the mounting by depressing a pedal.

The sight was carried on a crank which was mounted on a shaft passing through a tube and geared by a chain with a fixed central sprocket which kept the direction of the crank fixed, notwithstanding the rotation of the mounting. Training was effected by a hand-gear operating on a pinion engaging internal teeth on a base-ring.

The mounting was provided with a rotary platform for the gunner and a fixed cylindrical shield carried by the ring. The front nose section, with gun and mounting, was built on a spruce frame covered with three-ply and attached to the centre portion of the fuselage at three points, permitting easy replacement.

In 1933, two Blackburn Perth flying-boats were fitted with the 37 mm C.O.W gun on a manually operated mounting in the bow. The mounting for this gun was also of the Vickers-Westland type.

Another Blackburn flying-boat that was fitted with the 37 mm C.O.W gun was the Iris (S1593). Initially the bow section of this boat was different from that of the later Perth and the Vickers-Westland mounting did not appear to have been initially installed.

The above text and top photos were taken from "Armament of British Aircraft 1909-1939", by H F King. The bottom photo was taken from "British Aircraft Armament Vol.2: Guns of the RAF", by R Wallace Clarke.

Regards

Bob

Notes:

* Earlier the calibre of this weapon was denoted as either the 1 pdr or 1 1/2 pdr gun.

+ In the twenties the armament firm of Vickers bought the rights for this weapon from the Coventry Ordnance Works
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