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The Holman Projector was an
anti-aircraft Anti-aircraft warfare, counter-air or air defence forces is the battlespace response to aerial warfare, defined by NATO as "all measures designed to nullify or reduce the effectiveness of hostile air action".AAP-6 It includes surface based, ...
weapon used by the
Royal Navy The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against F ...
during
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
, primarily between early 1940 and late 1941. The weapon was proposed and designed by Holmans, a
machine tool A machine tool is a machine for handling or machining metal or other rigid materials, usually by cutting, boring, grinding, shearing, or other forms of deformations. Machine tools employ some sort of tool that does the cutting or shaping. All m ...
manufacturer based at Camborne, Cornwall. A number of models were produced during the war years, but all worked on the principle of a pneumatic mortar, using
compressed air Compressed air is air kept under a pressure that is greater than atmospheric pressure. Compressed air is an important medium for transfer of energy in industrial processes, and is used for power tools such as air hammers, drills, wrenches, and o ...
or high pressure
steam Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization ...
to fire an explosive projectile at enemy aircraft. Intended primarily as a stop-gap defensive weapon for British merchant ships, which had been suffering heavy losses from Luftwaffe aircraft flying anti-shipping missions, the low altitude at which such strikes often took place (such as during
torpedo A modern torpedo is an underwater ranged weapon launched above or below the water surface, self-propelled towards a target, and with an explosive warhead designed to detonate either on contact with or in proximity to the target. Historically, su ...
attacks by
Heinkel He 111 The Heinkel He 111 is a German airliner and bomber designed by Siegfried and Walter Günter at Heinkel Flugzeugwerke in 1934. Through development, it was described as a "wolf in sheep's clothing". Due to restrictions placed on Germany after th ...
s or skip-bombing attacks by
Focke-Wulf Fw 200 Condor The Focke-Wulf Fw 200 ''Condor'', also known as ''Kurier'' to the Allies (English: Courier), was a German all-metal four-engined monoplane originally developed by Focke-Wulf as a long-range airliner. A Japanese request for a long-range maritime p ...
) meant that a weapon of such limited range and velocity could throw up an effective screen of fire over a vessel, even if only to create a distracting or deterrent effect, obliging the enemy to bomb from greater heights which reduced bombing accuracy. While ineffective against normal bombing attacks from higher altitudes, the weapon was far cheaper, easier to build and install in great numbers than conventional anti-aircraft artillery. Holmans specialised in producing
gas compressor A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can transp ...
s and pneumatic equipment and its owner, Treve Holman, conceived a way that his firm could aid in the war effort beyond the production of tools. Recalling the
World War I World War I (28 July 1914 11 November 1918), often abbreviated as WWI, was one of the deadliest global conflicts in history. Belligerents included much of Europe, the Russian Empire, the United States, and the Ottoman Empire, with fightin ...
-era Stokes Mortar and its successor, the
Ordnance ML 3 inch Mortar The Ordnance ML 3-inch mortar was the United Kingdom's standard mortar used by the British Army from the early 1930s to the late 1960s, superseding the Stokes mortar. Initially handicapped by its short range compared to similar Second World Wa ...
, Holman believed that it would be possible to produce a version powered by compressed air. Preliminary tests showed that the idea was feasible, with an early prototype throwing an eighteen-pound steel weight nearly .


Mk I

The design eventually settled on for the Mk I featured a 4½ foot unrifled steel barrel. Rounds were dropped down the barrel from the muzzle and the pneumatic system triggered instantly upon the round striking the base. The rounds themselves were made from an open-topped metal container, holding a
Mills bomb "Mills bomb" is the popular name for a series of British hand grenades which were designed by William Mills. They were the first modern fragmentation grenades used by the British Army and saw widespread use in the First and Second World Wars. ...
fitted with a 3.5 second
fuse Fuse or FUSE may refer to: Devices * Fuse (electrical), a device used in electrical systems to protect against excessive current ** Fuse (automotive), a class of fuses for vehicles * Fuse (hydraulic), a device used in hydraulic systems to protect ...
. High-pressure air bottles were able to supply enough power to fire fifty rounds each, with a maximum height during trials of around . The rate of fire could reach thirty rounds per minute in the hands of an experienced crew. More appealing yet to the armed forces was the fact that the weapon could be produced using only
cast iron Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
and
mild steel Carbon steel is a steel with carbon content from about 0.05 up to 2.1 percent by weight. The definition of carbon steel from the American Iron and Steel Institute (AISI) states: * no minimum content is specified or required for chromium, cobalt ...
, both of which were in fairly ready supply at this stage of the war. An official trial of the Mk I Projector took place in February 1940 with resounding success. An order was placed by the Royal Navy for 1,000 of the Mk I models and the weapons proved just as successful in action; the first confirmed success was reported only three weeks after the initial batch was sent out when a Heinkel aircraft was damaged. While direct hits were rare, the bombs fired by the projector displayed an unexpected property — the explosion would leave a large puff of black smoke, absent from ground-based explosions from similar grenades. Firing a large number in quick succession gave the impression to incoming ''
Luftwaffe The ''Luftwaffe'' () was the aerial-warfare branch of the German ''Wehrmacht'' before and during World War II. Germany's military air arms during World War I, the ''Luftstreitkräfte'' of the Imperial Army and the '' Marine-Fliegerabtei ...
'' pilots that the target vessel was armed with something far more deadly than the Holman Projector, deterring or disrupting attacks, or convincing the aircraft's crew an attack at greater range would be prudent, with a commensurate decrease in accuracy.


Mk II

The Mk II Projector was developed after a request from the Royal Navy for a version that could be fired using
steam Steam is a substance containing water in the gas phase, and sometimes also an aerosol of liquid water droplets, or air. This may occur due to evaporation or due to boiling, where heat is applied until water reaches the enthalpy of vaporization ...
in place of compressed air, since the steam-engined
trawlers Trawler may refer to: Boats * Fishing trawler, used for commercial fishing * Naval trawler, a converted trawler, or a boat built in that style, used for naval purposes ** Trawlers of the Royal Navy * Recreational trawler, a pleasure boat built t ...
(both
fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment, but may also be caught from stocked bodies of water such as ponds, canals, park wetlands and reservoirs. Fishing techniques inclu ...
and minesweeping) had the former in plentiful supply. The Stokes design of the Mk I needed to be abandoned for this, since the harsh weather experienced by the trawlers invariably rusted the
valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...
s of the pneumatics. When steam was used in such a system, the water would condense in the pipes and prevent firing of the weapon. To solve this, a firing trigger was added, in place of the Stokes design in which the round would be fired automatically. The new version was fitted to a wide variety of ships, from
destroyer In naval terminology, a destroyer is a fast, manoeuvrable, long-endurance warship intended to escort larger vessels in a fleet, convoy or battle group and defend them against powerful short range attackers. They were originally developed in ...
s to minesweepers and motor gun boats: to demonstrate the weapon's versatility, a trial was arranged in Aldershot, Hampshire before
Prime Minister A prime minister, premier or chief of cabinet is the head of the cabinet and the leader of the ministers in the executive branch of government, often in a parliamentary or semi-presidential system. Under those systems, a prime minister is not ...
Winston Churchill Sir Winston Leonard Spencer Churchill (30 November 187424 January 1965) was a British statesman, soldier, and writer who served as Prime Minister of the United Kingdom twice, from 1940 to 1945 Winston Churchill in the Second World War, dur ...
. No Mills rounds were brought, as it was assumed that some form of ammunition would be provided by the
British Army The British Army is the principal land warfare force of the United Kingdom, a part of the British Armed Forces along with the Royal Navy and the Royal Air Force. , the British Army comprises 79,380 regular full-time personnel, 4,090 Gurk ...
, who were overseeing the trials but these were overlooked and the trial was set to be delayed until one officer thought to bring out the bottles of beer that were to have been served at lunch: the smooth bore of the Projector allowed even these irregular projectiles to be fired successfully, with all striking the target with an explosion of glass and foam. The Prime Minister commented on the weapon afterwards, describing it as "A very good idea, this weapon of yours. It will save our
cordite Cordite is a family of smokeless propellants developed and produced in the United Kingdom since 1889 to replace black powder as a military propellant. Like modern gunpowder, cordite is classified as a low explosive because of its slow burni ...
". (This was prophetic: while possibly apocryphal stories of projectors mounted on trawlers being used to fire 'spuds' (potatoes) at low-flying German aircraft for the want of Mills bombs led to the nickname 'potato thrower'. 'spud gun' etc.) Regardless of the successful trial results the Mk II proved to be highly inaccurate when fired at distant moving targets: only a dozen or so aircraft were confirmed to have been downed by the weapon in its first year of service but it succeeded in convincing many more aircraft that the target vessel was more heavily equipped with more effective weapons, confirmed by the large number of reports were made about Luftwaffe aircraft turning away from an attack after salvos from ship-mounted Holman Projectors. Within the
Admiralty Admiralty most often refers to: *Admiralty, Hong Kong *Admiralty (United Kingdom), military department in command of the Royal Navy from 1707 to 1964 *The rank of admiral *Admiralty law Admiralty can also refer to: Buildings * Admiralty, Traf ...
, the perception was that the Projector was a useful stop-gap weapon in the early years of the war, when other more effective anti aircraft weaponry, such as the
Oerlikon 20 mm cannon The Oerlikon 20 mm cannon is a series of autocannons, based on an original German Becker Type M2 20 mm cannon design that appeared very early in World War I. It was widely produced by Oerlikon Contraves and others, with various models emplo ...
, were in short supply.


Mk III

In 1941, production of the Mk III Holman Projector began. This version was semi-automatic, and capable of firing multiple projectiles in a single salvo to a height of around . The Admiralty placed an order for a further one thousand units, to be fitted to coastal gunboats and other light craft, where the light
recoil Recoil (often called knockback, kickback or simply kick) is the rearward thrust generated when a gun is being discharged. In technical terms, the recoil is a result of conservation of momentum, as according to Newton's third law the force requ ...
of the weapon had proven useful. Morris Oram, from Camborne, lead the development and was later presented by W. Churchill with a commemorative picture after successful trials of the Mk III at Portsmouth. He worked for over 50 years at Holman Brothers. Plans were drawn up for a Mk IV version of the Projector to fill this niche more readily, with a shorter barrel and swivel base but when these were ready the war had progressed, more advanced weaponry was available and that made the Projector obsolete. A number of the earlier model Projectors remained in service and discouraged attacks in the
Mediterranean The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western and Southern Europe and Anatolia, on the south by North Africa, and on the e ...
by some smaller
submarine A submarine (or sub) is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term is also sometimes used historically or colloquially to refer to remotely op ...
s, and a small number were adapted to fire
grapnel A grappling hook or grapnel is a device that typically has multiple hooks (known as ''claws'' or ''flukes'') attached to a rope; it is thrown, dropped, sunk, projected, or fastened directly by hand to where at least one hook may catch and hol ...
s for
commando Royal Marines from 40 Commando on patrol in the Sangin">40_Commando.html" ;"title="Royal Marines from 40 Commando">Royal Marines from 40 Commando on patrol in the Sangin area of Afghanistan are pictured A commando is a combatant, or operativ ...
cliff assaults. In total around 4,500 Holman Projectors were put into active service during World War II, and several can still be found in
museum A museum ( ; plural museums or, rarely, musea) is a building or institution that cares for and displays a collection of artifacts and other objects of artistic, cultural, historical, or scientific importance. Many public museums make these ...
s in the United Kingdom.


Effectiveness

While Holman Projector had limited success with one cargo ship's crew shooting down two airplanes, it became better known for its other uses. Since it had a wide barrel, the projector could shoot nearly anything that could fit inside it; the most popular makeshift ammunition was
potato The potato is a starchy food, a tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial in the nightshade family Solanaceae. Wild potato species can be found from the southern Unit ...
es.How the Humble Potato Cannon Served the Allies in World War Two
Popular Mechanics, Retrieved April 4, 2017.


Ammunition

File:Holman projectile HE diagram.jpg, File:Holman projectile illuminating diagram.jpg,


See also

*
Northover Projector The Projector, 2.5 inch—more commonly known as the Northover Projector—was an ''ad hoc'' anti-tank weapon used by the British Army and Home Guard during the Second World War. With a German invasion of Great Britain seeming likely after ...
, another World War II grenade throwing device * AA Mine Discharger, a Japanese anti-aircraft mortar. *
Unrotated Projectile The Unrotated Projectile (UP) was a British anti-aircraft and ground-bombardment rocket of the Second World War. A 7-inch version was developed for the Royal Navy by Alwyn Crow of the Projectile Development Establishment of the Ministry of Supp ...
, another Royal Navy anti-aircraft weapon. * Steam cannon, other steam-powered missile launchers


References


Notes


General references

* * *
Central Office of Information The Central Office of Information (COI) was the UK government's marketing and communications agency. Its Chief Executive reported to the Minister for the Cabinet Office. It was a non-ministerial department, and became an executive agency and a ...
, ''British Coaster, 1939-1945'',
HMSO The Office of Public Sector Information (OPSI) is the body responsible for the operation of His Majesty's Stationery Office (HMSO) and of other public information services of the United Kingdom. The OPSI is part of the National Archives of the Un ...
, 1947. * Ministry of Information, ''Merchantmen at War: The Official Story of the Merchant Navy, 1939–1944'',
HMSO The Office of Public Sector Information (OPSI) is the body responsible for the operation of His Majesty's Stationery Office (HMSO) and of other public information services of the United Kingdom. The OPSI is part of the National Archives of the Un ...
, 1944.


External links

{{WWIIBritishCommNavalWeapons Naval anti-aircraft weapons Grenade launchers of the United Kingdom Pneumatic mortars Military history of Cornwall Anti-aircraft guns of the United Kingdom World War II naval weapons of the United Kingdom British Merchant Navy Ingersoll Rand Weapons and ammunition introduced in 1940