How do you make a monster gun disappear?

In the second half of the 19^th Century advances in metallurgy allowed an unprecedented increase in the size and weight of artillery pieces for applications in which mobility by land was not a concern. This applied to weapons mounted either in fixed fortifications, or on ships. The speed of development was amazing. In the early 1860s the heaviest weapon afloat was the 68-pounder muzzle-loading cannon, an oversize version of the guns carried by Nelson’s Victory six decades earlier. It weighed some four tons, and was standard armament even on ships which were revolutionary in themselves, such as HMS Warrior. By 1867 however, 11-inch and 12-inch weapons of 25 tons were coming into service, firing 600-pound projectiles and yet larger weapons were to follow in the coming years.

68-pounder replicas on HMS Warrior (1860) – scaled-up versions of Nelson’s weapons at Trafalgar

These guns had a slow rate of fire and protecting them against enemy fire during their laborious loading sequences was a vital concern. One obvious solution was to place them behind protective barriers – earth or masonry fortifications on land, armour at sea. An additional protection was however to expose them to enemy view for the shortest possible time so that they would be visible only in the brief interval of firing, returning to cover immediately thereafter.

The solution to this was “the disappearing mount”. The gun-barrel was mounted on hinged arms which, when in the lowered position, supported it in a horizontal position behind a protective barrier, invisible to an observer outside it. In this position it could be loaded in safety, the short range capabilities of the period precluding plunging fire, and when ready the hinged arms would carry the barrel up above the barrier. It would remain exposed only until fired. Its recoil would sweep the weapon back down to the loading position again, braked by a counterweight which in due course would be used to hoist the gun for the next firing. In later years hydraulic systems were used to supplement, or replace, the counterweight.

The system saw only limited use at sea – as discussed later – but it reached its highest level of sophistication in land fortifications, some such weapons remaining in use up to WW2. The principle is best illustrated by reference to a land-based weapon, shown in the photographs below. Taken around 1905, these show a French “Canet” weapon of 9.4-inch calibre under test, before being disassembled and hereafter reassembled in a coast-defence fortress. The large circular disc is an armoured shield which will lie flush with the top of a concrete pit and has a rectangular opening in the top through which the gun-barrel will emerge. The first photograph shows the weapon in its lowered position, ready for loading, while in the second the gun has been raised to the firing position. The entire assembly, including the top shield, could be rotated through for aiming.

Canet 9.4-inch weapon, shown under test, in lowered position (1905)
The unit will later be located in a  circular concrete pit
The circular armoured roof will lie flush with the surrounding ground

The Canet 9.4-inch raised from cover for firing. It will sink out of sight thereafter.

Details of the hinging system varied from one design to another, and hydraulics were increasingly used not just to manage the forces involved, but to allow accurate adjustments in azimuth and elevation and to facilitate loading. The illustration below shows an American 12-inch mounting of mid-1890s vintage. Similar mounting were used for 14-inch guns in American coastal fortification from the early 1900s and two 16-inch weapons were employed to defend the Panama Canal until at the end of WW2.

Preserved 8-inch disappearing gun of the South Battery, Devonport, New Zealand

Use at sea of disappearing mountings was of much shorter duration. The mechanisms involved were complex and operation was not helped by a ship’s rolling and pitching. The Royal Navy only employed such mountings on a single capital ship, HMS Temeraire, launched in 1876. Four 11-inch 25-ton guns weapons were carried on Moncrieff mountings (so called after their inventor), two forward, two aft, in pear-shaped armoured redoubts. The layout can be seen below and it will also be noted that Temeraire also had 10-inch weapons mounted amidships inside an armoured central battery. The experiment of using disappearing mounts was not repeated in any Royal Naval capital ship due to the weight and space demands – the latter being obvious from the drawing.

HMS Temeraire, hull plan and elevation
Note the pear shaped armoured protection fore and aft

HMS Temeraire at sea, the forward mounting just visible
She was the largest brig ever built and, not surprisingly, slow under sail

HMS Temeraire’s forward mounting being trained

An unusual use of a ship-mounted disappearing mount for heavy guns was in the bizarre Russian Popovka-type coast defence ships. Readers of my novel “Britannia’s Wolf” will already have made an acquaintance with these monsters. A dual 12-inch mounting can be seen below on a Popovka inside its encircling armoured wall, that on the right raised for firing, her sister on the left dropped back below cover for reloading.

The other main application of disappearing mounts was in “Flatiron” gunboats, also called Rendels after their inventor. These were small shallow-draught vessels, very manoeuvrable, and carrying a single enormous gun, usually in the 8-inch to 12-inch range. This was fixed to fire forward along the craft’s axis and was aimed by aiming the entire vessel. In their heyday, from about 1867 to 1880, more than 40 were built for the Royal Navy, including units for Australia, and large numbers by most other navies, including minor ones. They were seen primarily as coast and estuary-defence vessels and were expected to operate in groups. As such their role was superseded by the arrival of the fast torpedo boat and they were quickly relegated to other duties. Several Rendel designs, including the 20-unit Ant class for the Royal Navy, employed disappearing mountings.

HMS Toad and her disappearing gun – heroine of Britannia’s Reach (Click here)

A Rendel unit with a sophisticated hydraulically-operated disappearing mount  – HMS Toad,  originally ordered from a British yard by the Greek Navy, but taken over by the Royal Navy when Greece could not pay for her – plays a central role in my novel “Britannia’s Reach”. As such, she is almost a character in her own right.

Chinese Rendel Gunboat Delta 
Note 12.5-inch 38-ton Armstrong muzzle-loader forward

The Imperial Chinese navy also made extensive use of Rendels, some participating in the Sino-French War of 1884 (2 lost) and in the Sino-Japanese War of 1895 (12 sunk or captured). Almost all were constructed in Britain and carried sailing rig – as in the illustration below – during the delivery voyage but are likely to have dispensed with it in normal service.

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