In 1891 a Pneumatic Dynamite Gun (Aerial Torpedo Thrower) was purchased by the British Government for evaluation as a coast defence weapon. It had been under construction at Cold Spring for two years. It had been patented by Mr. George H. Reynolds in New York, and British patents, covering every detail of its construction, had been secured by Mr. Henry Eichbaum, in No. 6869, of 1889, and later specifications.
An 8in. experimental dynamite gun was fired in America in 1887 and that model had proved to be most erratic in its performances. Dynamite guns of 15in. calibre were also fitted to the cruiser USS Vesuvius, and another 15in. pneumatic gun, built for the Italian Government and mounted at Spezzia, were not altogether regarded as successes. The 16inch version bought by the British Government for a large sum of money was manufactured by the West Point Foundry, at Cold Spring-on-Hudson, in the United States.
It was hoped that it would prove to be an excellent investment. More especially, too, in view of the possibility of a further grant being required from Parliament for the purchase of similar guns. The gun was initially mounted at Shoeburyness testing grounds on the River Thames. Following these tests it was moved to Dale Point Fort at Milford Haven for further trials.
Figs. 1, 2, 8, and 4, show the 16inch version of the British dynamite gun, as designed and patented by Mr. George H. Reynolds in America, and Mr. Henry Baum in England; together with sections of the yoke, pintle and hollow trunnions, by which the compressed air is conveyed to the interior of the barrel.
The gun is 50ft. long, with a calibre of 15in. Its great length is necessary in order to insure that the full pressure of the compressed air shall be exerted upon the base of the projectile before it leaves the muzzle. The passage of the shell through the barrel only occupies from 1/10 to 1/50 of a second; and in this brief space of time the compressed air has to be introduced through the firing valves, and has to develop its expulsive power. This process is not nearly so rapid as that of the development of powder gas upon the discharge of a powder gun. The full-calibre projectile weighs from 9001b. to 1000 lb., and contains from 500lb. to 600lb. of high explosive as a bursting charge. The main tube or barrel, instead of being hung or supported, as has hitherto been the ease, at the breech end, is supported upon trunnions a considerable distance from the breech, but not so near the muzzle as to interfere with the preponderating weight of that end of the tube which is required for the satisfactory working of the gun. The air pressure is contained in a series of reservoirs disposed underneath the gun-carriage, and which consists of twelve tubes, two of which are shown in our engraving of the elevation of the gun, closed at one end, and communicating with the main channel or pipe by which the compressed air is conveyed to the gun. These reservoirs are placed in opposing sets, the object being to balance them as completely as possible. The gun carriage is pivoted upon a hollow centre or pintle, Fig. 3, closed at both ends, the hollow interior communicating with the reservoirs, the inlets through which are arranged opposite each other, again with the object of balancing the pressure, shocks, or strains. Peripheral openings or ports are provided in the upper part of the pintle at the sides, so as to obviate lifting, through which the air passes into an annular chamber around. This chamber resolves itself into the two hollow arms of a yoke, conveying the compressed air through hollow trunnions to the side tubes of the gun, each of which carries at one end a trunnion, and terminates at the other, near the breech of the gun, in a valve box. The trunnion boxes are carried upon brackets disposed upon the gun carriage in the ordinary manner.
The breech of the gun is closed by a sliding breech shutter, Fig. 12, having a slot with which a projection upon a hand lever engages. By this lever it is operated. The projectile is brought up by a small carriage or truck running upon a circular railroad accomplished by means of an hydraulic cylinder pivoted to the carriage, and having a plunger or piston-rod pivoted to the truss or framing supporting the gun barrel. The arrangements for training and elevation are modified in the Victorian gun, which may be worked either by hand or by an electric motor, as will be seen further on. The elevating truss or girder also is acted on differently. Some of the more important features of this invention relate to the valves, Figs. 5 and 6, for regulating the admission of the compressed air to the gun barrel, and to the packing of the joints. The air pressure, as already described, is conveyed by the side tubes to the valves, Figs. 7, 8, and 9, at the breech of the gun, and it will be understood that the pressure, being very severe, generally a thousand pounds to the square inch, and the valve, which is of considerable dimensions proportionate to the requirements of the gun, requiring to be opened a certain distance, but also to be closed so quickly as to be open for an almost inappreciable length of time-say from the 1/10 to the 1/50 of a second- it will be understood that the proper action and complete regulation of the firing valve is of the utmost possible importance to the working of the gun. It is manifest that the opening and shutting of the valve could not be accomplished directly by hand-power, however rapidly applied even if a sufficiently powerful lever could be employed. In providing, then, a valve possessing the necessary requirements, it is essential to have two valves, one the large firing valve proper, and the other a smaller valve to operate the larger one, which we shall hereafter call the controlling valve. In the gun now under consideration two firing-valves are employed, one on each side of the breech, so as to neutralise the shock of the rush of air from them into the barrel. One of the patents provides an annular valve for this purpose, with peripheral openings. The firing valves are hollow, having a cylindrical body externally smaller in diameter than the valve face at one end and the disc at the other, and this disc acts as a piston in a recess of the casing. Part of the interior of the valve is filled with soft packing, for the purpose of deadening the shock when the valve lifts, and when the valve is wide open this packing comes in contact with a atop projecting into the interior of the valve, and adjustable by means of a screw passing through the exterior of the cuing, and turned by a spindle carrying an indicator, Figs. 5, 6, and 9, so that the stop may be adjusted. Thus, the opening and shutting of the valve are regulated to a nicety. The valve piston is in its normal condition =Neat to equal air pressure upon both aides, and is of slightly greater area than the face of the valve ; ordinarily, therefore, the valve will remain upon its seat. But if the pressure at the opposite end of the piston is withdrawn, the valve will rise. The object, then, to be attained in operating this valve is to withdraw or diminish the pressure upon the back of the piston momentarily, and as quickly to replace it. This is accomplished by means of the auxiliary or controlling valve, Fig. 8.
The controlling valve, which appears in the main drawing upon the upper side of the gun’s breech is double, consisting of a cylinder and piston to cut off and restore the pressure behind the firing valve, also of a small hand valve in the same casing in communication with it, which can be operated with a hand lever. The piston of the larger cylinder is normally subject to pressure upon both sides ; one end carries the valve proper. The cylinder is provided with two annular recesses, one in connection with a constant supply of air pressure, and the other communicating with the back of the piston of the firing valve. When the controlling valve slides between the two recesses, their connection is cut off, and, consequently, the air pressure upon the firing valve ; so to lift the firing valve from its seat is accomplished by opening a communication between the second annular recess and the atmosphere, and this is done by allowing the controlling valve a sufficient travel. In its open position, therefore, the controlling valve stands between the two annular recesses, the second of which is open to the atmosphere. The hand valve, Fig. 8, which is hollow, terminates in a recess in communication with the constant pressure, and suitable holes are provided in it by which the pressure can pass from the interior of the valve to the back of the piston of the controlling valve. These openings in the hand valve are so arranged that they can be moved into the close-fitting portion of the casing, and are thereby closed. The operation is as follows:-Normally the hand valve rests upon its seat, held there by the air pressure. As, however, it is of small size, a moderate sized lever can force it back by hand. This movement effects two objects: Firstly, it moves the holes in the hand valve into the closed part of the casing, and cuts off communication between pressure and controlling valve ; and secondly, by removing the valve from its seat it opens direct communication between the back of the controlling closing is effected as follows :-The spindle of the hand valve has a trigger with a ring attached to the spindle of the controlling valve, and when the latter moves it this trigger releases the band valve from the control of the operator, the pressure instantly closes the hand valve, restoring the pressure to the back of the controlling valve ; the pressure on the back of the firing valve being likewise restored, and the valve closed in consequence.
The length of time during which the controlling valve remains open is determined by the position of a regulating cock, provided with an external indicator, by which its position can be determined ; the opening covered by this cock being carried to a point at one part, so that the amount of opening may be regulated to a nicety. If this cock be wide open, the controlling valve will return to its scat the very instant the trigger has slipped; if entirely closed, the controlling valve will never return to its seat at all ; therefore the movements of the controlling valve can be exactly adjusted. The trigger has a spring, to keep it always up to the top of the spindle of the controlling valve.
The packing arrangements for the various working joints are as follows. Take the pintle, Figs.10 and 11:- The yoke is provided with two annular recesses, one above and the other below the peripheral openings in the pintle already described; in each of these recesses, the bottom of which is rounded, is placed a hydraulic cup leather, upon which rests a perforated metallic distance ring. Upon this is a second cup leather packing ring reversed ; and upon this another ring recessed to receive the cup leather, and connected by suitable distance pieces with a similar ring in the second annular recess. This ring is also hollow and receives a cup leather, upon which is another perforated ring, and upon this again another inverted cup leather; the system of packing rings being made secure by a gland fitting into one of the annular recesses and secured by bolts. Each of these annular recesses is in communication with oil under pressure which is greater than the permanent air pressure, so that while the air is seeking to escape around this packing the oil is seeking to enter in an opposite direction still more vigorously, and the two forces neutralise one another. The appearance of the completed gun, its carriage, projectile, and loading arrangements, are so clearly set forth in the large engraving, page 500, that it is needless to describe them further. We shall, however, talk of projectiles later on. The 15in aerial torpedo thrower, now introduced as a British service weapon for coast defence, resembles in appearance a powder gun, having the axis of its trunnions at or near the centre of gravity of the barrel. The barrel is of cast iron, smooth bore, made in three sections, the walls being about 1.5in. in thickness. The breech plug or gate is simply a convex disc, with a tooth-shaped or interrupted flange. This is an unimportant deviation from the original design. The disc swings outwards on a hinge, and when closed is secured by turning it a small fraction of a revolution. In the rear of the trunnions there is an outer casing round the barrel, which conveys the air from the hollow trunnions, where it enters, to the breech. This also is a deviation. The casing replaces the two side pipes of the original design, and gives the weapon a more cannon-like appearance.
The main firing valve is at the breech, and of the annular nature already alluded to, being another deviation from the original design. It consists of a large sleeve sliding on the outside of the barrel in its closed position, covering six ports leading into the barrel, just in rear of the projectile. The movement of this large firing valve is controlled in precisely the same manner as by the process already detailed for the original design, viz., by a much smaller auxiliary or controlling valve upon the outside of the gun. It is shown in both of the engravings. To discharge the gun the auxiliary valve is opened with a lever, located in a convenient position at the left trunnion. After doing this, the operator has no further control over the valve, as it is entirely automatic in its action. The time regulation of the valve-in other words the cut-off-is governed by the time required for a fixed volume of air to flow through an orifice. The size of this orifice fixes the time, and this is adjusted by a micrometer screw, as already detailed in our description of the controlling valve. Thus, by simply turning a hand wheel, the range can be varied from a few hundred yards to several thousand without changing the pressure of the air or the elevation of the piece.
The carriage is box-form, built up of wrought iron plates, stiffened and fastened together by angle irons and other strengtheners. It is mounted on a circular bed-plate, and contains the traversing and elevating gear, sic. As already stated, the gun is traversed and elevated either by hand cranks at the side or by an electric motor. This motor is controlled by a rheostat and switch on the firing platform, at the hand of the officer sighting the gun. The gun can be traversed 360 deg. and elevated 35 deg.
The firing reservoir consists of six wrought iron tubes, 16in. in diameter and 25ft. long, three on either side. The air from them flows up through the central pintle, which has a large turning joint, to the trunnions, where it enters the casing about the barrel. These pipes and casing are under pressure all the time when the gun is being used. The air pressure is usually 1000lb. per square inch. In addition, air is stowed in reserve tubes, at a pressure of 2000lb. These are called the storage reservoir. Air is drawn from it after each shot to restore the pressure in the firing reservoir. Air is pumped in by a compound steam engine. The compression takes place in two or three successive stages, and the air is cooled between each stage as well as during compression.
Two types of projectile are now used, in various sizes, known as full calibres and sub - calibres. The full calibre, which fills the bore of the gun completely, consists of a light, strong case, containing the explosive, fuse, &c., with a small tube in rear, supporting the rotating blades or vanes. The body consists of a steel or iron tube, fin. to 3/16in. thick, closed at the front end by a brass conoidal-shaped head, and at the rear by a hemispherical base casting of bronze. The base casting has a socket in the centre to attach the small tube that supports the rotating blades. Eight blocks of vulcanised fibre on each end of the shell centre it in the bore of the gun, and prevent the metal parts of the shell from touching the bore, thus avoiding friction. Shells for a 13in. gun are about 10ft. long over all, the body being about 7ft. and the rear extension 3ft.; total weight when filled 10001b., containing 5001b. of high explosive. The fuse is placed either in the point or base, according to the design. The sub-calibre projectiles -one of which is engraved-are smaller in diameter than the bore of the gun, and have no rear extension carrying rotating blades. The blades are attached directly to the body, near the rear end. They occupy a portion of the space between the body of the shell and the bore of the gun, at the same time serving to centre the rear end of the shell in the bore. The front end is centred by four wooden blocks, which drop off as soon as the shell leaves the muzzle. They are held in place dining movement through the bore by pins entering into the shell. A wooden disc or gas check is placed in rear of the projectile, filling the bore completely and preventing any escape of air. The body of the projectile is made up similar to the full calibre, except that the charge only fills about three-fourths of it, the remaining space at the rear being left empty. This is done to maintain steadiness in flight. Sub-calibre shells are as follows:
The range of the gun depends upon the pressure, the point of cut-off, the elevation of the piece, and the kind of projectile used. With 1000 lb. pressure per square inch, a maximum cut-off, and an elevation of 35 deg., the range of a full-calibre projectile, weighing 1000 lb., is about 2700 yards, or 11 miles ; that of a 10in. sub-calibre, weighing 500 lb. is about 4000 yards, or 21 miles ; and that of an 8in. sub-calibre, weighing 3001b., is about 5000 yards, or 2) miles. The muzzle velocity of these shells varies, of course, under different conditions, but it usually lies between 450ft. and 800ft. per second.
The projectiles are not designed for penetration, but at Shoeburyness a 10in. sub-calibre, weighing 500 lb., was fired into a butt of sand, situated 600 yards from the gun, and it penetrated 47ft.
The accuracy of fire is very remarkable indeed. The following is a record of ranges and deviations obtained at Shoeburyness on the 21st and 30th January, 1891:
A News report 10 December 1892 noted:
"The great American pneumatic gun is described by a visitor to Shoeburyness as capable of throwing a shell having a charge of 600lb of dynamite. it resembles a huge telescope, pointing upward, at an angle of 30 degrees and is 70ft long. The shots discharged by the gun, it is added, were carried a mile and a half, and every one is described as having fallen within the space of the floor of a large public hall."
Dale Fort Entrance
Remains of Dynamite Gun
After initial testing at Shoeburyness the gun was moved to Dale Fort, Milford Haven defences for further tests. As the trials continued work on the projectiles and alterations required by the installation were undertaken at Shoeburyness.
The President of Ordnance Annual Reports noted that:
On 4th January 1894, the Superintendent of Experiments forwarded a progress report on the departmental trials of projectiles made at the Ordnance Factories. The hard frost that prevailed had frozen the water pipes, the lift for raising the projectiles, and the liquid used for the moving joints. Under the circumstances, the Inspector of Ordnance Machinery had extreme difficulties to contend with in raising the necessary pressure in the gun. Two rounds were fired at 15 degrees elevation, with 8inch dummy projectiles, a range of 2,880 yards being obtained. Both shells were steady in flight. After the first round, a leak broke out in the left trunnion; this was temporarily stopped, but after the second round became unmanageable.
Commanding Royal Engineer forwarded certain proposals connected with the Committee’s programme which were concurred with.
The Deputy Adjutant-General, Royal Artillery, 2nd February 1894, asked if the Royal Artillery were to take over everything connected with this experimental gun. The Committee recommended that the General Officer Commanding should make his own arrangements while the gun was in an experimental state. Further rounds were fired, 7th February 1894, with 15-inch, 10-inch and 8-inch dummy projectiles. The gun worked satisfactorily. The 15-inch projectiles did not do well, they were unsteady in flight and revolved end for end. the 10-inch and 8-inch projectiles were satisfactory.
The Director-General of Ordnance Factories proposed to alter three of the Committee’s 15-inch projectiles, which was agreed to.
On receiving a joint report from the Officer Commanding Royal Artillery, Pembroke and Severn District, and Commanding Royal Engineer South Wales, on the preliminary practice, containing full information with recommendations as to the installations at Dale Point, the Committee pointed out that no unnecessary expenditure should be incurred until the gun was adopted into the service. They were of the opinion that the existing arrangements, though imperfect, would suffice for the experiments.
Programme No. 874 was begun on 20th September 1894. Full details of the results, and recommendations of the Committee are given in reports Nos. 1,015 and 1,021.
The Director of Artillery, 28th November 1894 stated that he did not desire that any further serious expense should be incurred until it had been shown by actual practice under Service conditions that the gun offered some prospect of success as a weapon. Consequently the Committee will proceed with Programme No. 874, when the projectiles have been modified by the Director=General of Ordnance Factories.
In 1894, Major Kenyon published a book on Coast Defences. In it he stated:
Zalinski Pneumatic Gun.—Some form of this gun might be very valuable in special cases, but it has not yet been found practicable to adopt it for general purposes, and, in fact, it is at present rather a competitor with the dirigible torpedo than with the ordinary gun. The Zalinski can fire 15-inch, 10-inch, 8-inch, and 6-inch projectiles, with bursters of 500, 250, 100 and 501bs. respectively, but with the largest its fire has been very far from accurate. Its ranges are as follows for these calibres :—
With a burster of 50lbs. of high explosive .. 5,500 yards.
100lbs. ... 5,000
250lbs. ... 4,000
500lbs. ... 2,000
Its rate of fire is about one shell a minute for the first 10 rounds, after which eight minutes are required for each round. Its fuzes are electrical and can ignite either on a direct hit, or under water after suitable delay if direct hit is not obtained.
The President Ordnance Annual report for 1896 signed the end of the Zalinski Dynamite Gun as a possible Coast Defence weapon. The report noted:
(a) The air-compressing and storage apparatus: This is known to be inefficient. In carrying out Programme No. 1,132, 13 rounds were got off in about 4 hours; and, though the storage and loading arrangements might have admitted of the first 11 rounds being fired within an hour, the rate of fire would have been reduced to about 1 round per hour, so that no more than 14 rounds could have been fired in the above time. As a comparison, it may be noted that an item in the American trial, before referred to, consisted of a continuous endurance trial of 3 hours. Two abortive attempts were made, but on the third essay, no break down involving delay occurred; and in 3 continuous hours, 116 blank or ‘air’ rounds were got off from the three guns.
The possibility of a satisfactory installation depends upon the expense it is possible to incur, and the expert supervision and working that can be provided.
(b) The gun and mounting: These worked smoothly and well, but there is a defect in the fitting of the new breech bonnet.
(c) The ammunition: The fire was inaccurate; the behaviour of the projectiles in flight was such that gunnery became a matter of chance. The projectiles were of the same kind as had previously been successfully used, and were carefully made for this trial, but the fuze used at this trial had a projecting vane. If the tendency to gyration is not considered, the Committee believe that the inaccuracy of the practice was mainly due to the bad fitting of the breech bonnet, which caused the leather gascheck rings at the base of the projectiles to be torn off. The projectiles themselves were very efficient, the ‘mine’ effect being very noticeable. The fuzes acted very well, the design submitted by Director-General of Ordnance Factories, viz Royal Laboratory No.8992A, which is a new departure, being a complete success.
The Committee considered that compressed air could be employed on land for the propulsion of large charges of high explosive, but that, so far as present experience goes, a costly installation, and expert staff were required. They were, therefore, not prepared to recommend the adoption of pneumatic guns, unless it was considered, in any particular instance, that defences, suitable to local requirements, could not be provided for by methods at present familiar to the Service.
With regard to the installation at Dale Point, they did not consider it efficient in a military sense, and they believed it would cost more than the occasion warranted to make it so, having regard not only to the first outlay, but also to its maintenance and the expert staff required.
It was for consideration whether it should be maintained for experimental purposes only, in case, from motives of policy, or the failure of other means of propulsion, and installation of the kind should be contemplated elsewhere.
If permitted to do so, the Committee were prepared to take up the question of the propulsion of projectiles containing large charges of high explosive from guns or howitzers.
An engraving in Tony Hill's book 'Guns and Gunners at Shoeburyness' includes a copy of the following illustration, stating that it is of the Shoeburyness 15inch Dynamite Gun mounted just inside the western boundary of New Ranges 1890-91. However tthis is not correct. It is the American Sandy Hook gun. In America there were to batteries, each of three guns, mounting this version of the Zalinsky Dynamite Gun. They were not a success.
Three guns were also mounted on the USS Vesuvius, which also proved to be a failure during trials in 1889.
Other navies also tried an installation such as the Dynamite gun on the Brazilian ship, Nictheroy.