The Disappearing Gun

By
Jim Mathews

In the 1860s, with the rise of the ironclad ship and the general improvement in shipboard armament, the coast defenses of the world had been extensively overhauled in an attempt to keep pace.  At the beginning of this period the standard method of deploying coast guns was in open batteries, but the advent of armor and powerful guns on ships led to the adoption of armored forts in which guns were protected by casements with enormous thickness of iron and granite to protect them.  This was a very expensive method of construction; a single armored casemate for one gun, together  with it's necessary magazine arrangements, cost over 3800 Pounds (British Pounds Sterling), without the cost of the gun being considered.  Further, the slowness of the rate of fire of the heavy Rifled Muzzle-Loading (RML) guns demanded the development and construction of large fortifications with numerous guns to swamp the enemy with gunfire. Picklecombe Fort in Plymouth Sound, for example, was prepared with forty-two armored casements, an expense of 160,000 Pounds, before the guns were installed. By way of comparison, the Moncrief carriage and it's pit cost a mere 1345 Pounds, a considerable saving.  A second problem of the day, as with the Naval Ordnance Engineer, was that of controlling recoil in confined spaces.

As early as 1835, Colonel DeRussey of the American army had suggested mounting a gun on a form of standing carriage in which the wheels were mounted eccentrically so that as it rolled back, it would descend behind the fort's parapet for concealment.  On the face of it, this was a fairly sound idea, but one which was difficult to put into practice, largely due to the difficulty of running the gun back into it's normal firing position.

All of the above problems and related factors were reconciled in the design of a gun carriage put forward in late 1860s by Captain Moncrief of the Edinburgh (Militia) Artillery. 

Alexander Moncrief (1829-1906) was the son of an Officer in the Madras Army (Presidency of Madras in India -- British East India Company).  He was born in Edinburgh , and after studies in the ancient universities of Aberdeen and Edinburgh , he spent some time in a civil engineer's office, but did not settle to a profession, at that time.  On April 16, 1855 , he was commissioned into the Forfar and Kincardine Artillery (Militia) and promptly went off on leave to the Crimea , where he watched the Russian guns being knocked out in the Mamelon Fort on July 6, 1855 .  The damage done by the shots put through the embrasures of that fortification, inspired him to design a disappearing artillery carriage in 1868. 

A previous design of a counterpoise carriage was proposed about 1860. While theoretically sound the Buffington Carriage would have been difficult to make up into an operational weapon, and it had to wait for significant improvements before it would prove it's worth.  This design is shown below.

Moncrief's proposal was in the form of a counterbalanced gun carriage. In 1871 twenty of these were issued.  The gun, a 7 inch RML, was mounted in a light carriage and this was connected to the top of a pair of curved arms which could roll back on a lower carriage.  The rear of this gun carriage had two wheels which ran in an inclined plane.  Thus, when the gun was fired, the recoil forced it back so that the curved arm rolled and allowed the wheels to run down the plane, bringing the gun below the level of the parapet.  A large counterweight was fitted to the bottom of the curved arms to resist the force of the recoil, and this together with the curved face of the arm brought the gun to rest where it was retained by a pawl.  Loading was now carried out under cover and then the pawl was released allowing the counterweight to swing the gun up over the parapet into the firing position:

This provided a gun which was invisible from the sea until the time came to fire, and which protected the crew while loading and serving the piece was accomplished.  The lower carriage could be moved to provide traverse, and an arc and screw on the top carriage controlled elevation. The only snag lay in the sights, which were still of the direct fore-sight and back-sight type, which meant that the gunlayer had to leap up on the platform and expose himself to lay and fire the gun. This was a small drawback though, and the Disappearing Carriage (as this class came to be called) rapidly caught the fancy of every nation looking for a suitable gun mounting. 

This carriage design had three advantages:

1.It gave the gun crew protection from direct fire by enabling the carriage to raise the gun to shoot over a solid parapet from a lower position which was convenient for loading;

2.It stored the force of the recoil so that it could be used to raise the gun back from the loading to the firing position;

3.The interposing of a moving fulcrum between the gun and it's platform lessened the strain on the latter and allowed it to be of lighter construction. 

In Moncrief's first model a sub-carriage was used to keep the gun at a constant angle as it disappeared.  The counterweight at the foot of the rolling arms was an iron box filled with several hundred-weight of gravel.

Moncrief, in 1877, produced an improved version of his mounting; the Mark II carriage for the 7 inch (17.8 cm) or 7 ton RML, (shown below).  This modification dispensed with the top carriage and slung the gun directly on top of the "elevators" as the curved arms are now known. The recoil pushes the gun on it's curved elevators back and downward to the loading position, the energy of the recoil being used to raise a heavy, cast-iron counterbalance weight, which can be used to return it to the firing position.  This improved carriage did away with the sub-carriage, and the counterweight was made of massive iron blocks.  Over eighty of these were taken into service, and installed in British fortifications all over the world.  Later "disappearing" carriages employed hydro-pneumatic or hydraulic recoil buffers.

In the USA , Captain (later General) Crozier of the Ordnance Department had taken an early idea attributed to General Buffington, in which the gun was mounted on a parallelogram, modified it and added hydraulic cylinders and a counterweight to produce the Buffington - Crozier Disappearing Carriage.  This modification was the zenith of this kind of unit, Guns of 14 inch caliber were commonly mounted on this carriage and the last and biggest were two 16 inch guns mounted at Panama during the First World War and dismantled late in the Second World War. 

Moncrief transferred to the Edinburgh Artillery (Militia) in 1863, became a Major in 1872 while attached to the Royal Arsenal Woolwich, and was made Colonel in 1878.  He was elected a Fellow in the Royal Society in 1871, and knighted in 1890.

The diagram below shows a British 13.5 inch Disappearing Gun. This is the largest British gun to be mounted on a disappearing carriage.  Three were emplaced in the 1890s but they proved to be too complicated and were withdrawn and scrapped in 1911.

The following illustration shows a diagram of a British Hydro-Pneumatic Mounting. The Elswick Ordnance Company married the hydro-pneumatic recoil buffer to the Moncrief principle and produced this mounting which became the standard British pattern.  Protected by a nine-foot deep pit and an overhead shield, they were emplaced in British defenses from London River to Hong Kong .

The next diagram illustrates the Buffington-Crozier Mounting.  This was the acme of disappearing carriage design, the American coast defenses mounted everything up to and including the 16 inch naval rifle on these carriages.  Taking Buffington's idea, Crozier turned it into a practical device.  The gun arms lift a massive counterweight and are damped by hydraulic buffers at the pivot point, due to the gun arm pivots moving back.  The gun describes a complex path during recoil.

In the Royal British Navy in the 1880s another problem surfaced.  This was the problem of a balance of firepower on a ship between broadside and frontal firing guns.  An interesting attempt to solve the problem was the "HMS Temeraire" completed in 1877 at the Chatham Naval Yard south of London , England .  The design utilized in "Temeraire" was a central battery structure, but in addition mounted two pivot guns, one at each end of the ship.  The pivot gun, had by this date fallen into disrepute due to the difficulty of protecting it, but in the "Temeraire" this was solved by adopting a device which had been originally developed for Coast Defense; the disappearing carriage.  It was this hydraulic carriage which was now adapted to naval service in "Temeraire"; two carriages, each mounting a 12 inch RML gun were used, one in each pivot gun position.  Instead of the "pit" of a land gun, these were protected by armored "barbettes", armor- plated  circular structures within which the guns could be worked and over the top of which they were fired, recoiling down and behind the protection between shots.  Thus all-around fire was secured with protection.  However the "Temeraire" was never repeated; the hydraulic disappearing carriage was a temperamental device at the best of times, cosseted by artificers in fortress applications and undoubtedly prey to every defect that salt and water could devise in a naval application.  Further what the shifting balance of a heaving ship would have done to the sensitive geometry of the carriage is something about which the naval records are strangely silent.

The disappearing carriage had two drawbacks which were insurmountable. One was the restricted elevation available -- the greatest elevation ever managed by one of these designs was a mere 20 degrees and that was not good enough for the new and powerful guns which were coming into service at the end of the 1890s.  The other drawback was the slow rate of fire due to the time taken for the gun to swing up and down and be reloaded.  In the early days of coastal gunnery, shooting was a leisurely affair, but the improvement in the speed of warships demanded an increased rate of firing and the disappearing carriage was at a disadvantage compared with a gun which stayed in position.  Such a gun could be laid continuously on the target while loading and firing went on.  Another advantage of the stationary gun was that the demand for protection was not now so great, since the more powerful guns could keep enemy ships out at a range where they could hardly see the shore weapons, particularly if some intelligence was applied to the matter of concealment and camouflage.

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