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Holman Projector
The Holman Projector was an anti-aircraft weapon used by the Royal Navy during World War II, primarily between early 1940 and late 1941. The weapon was proposed and designed by Holmans, a machine tool 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 or high pressure steam 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 attacks by Heinkel He 111s or skip-bombing attacks by Focke-Wulf Fw 200 Condor) 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 h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Porthtowan
Porthtowan ( kw, Porth Tewyn, meaning ''cove of sand dunes'') is a small village in Cornwall, England which is a popular summer tourist destination. Porthtowan is on Cornwall's north Atlantic coast about west of St Agnes, north of Redruth, west of Truro and southwest of Newquay in the Cornwall and West Devon Mining Landscape, a World Heritage Site. Porthtowan is popular with surfers and industrial archaeologists; former mine stacks and engine houses dot the landscape. Geography Porthtowan lies along the Godrevy Head to St Agnes heritage coast, which is located on the north Cornwall coast of the Celtic Sea in the Atlantic Ocean. It lies between Godrevy Head (with the Godrevy Towans) and St Agnes Head, north of the village of St Agnes.Ordnance Survey: Landranger map sheet 203 ''Land's End'' ''St Agnes Herita ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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, but are usually discussed as a separate category. In an open valve, fluid flows in a direction from higher pressure to lower pressure. The word is derived from the Latin ''valva'', the moving part of a door, in turn from ''volvere'', to turn, roll. The simplest, and very ancient, valve is simply a freely hinged flap which swings down to obstruct fluid (gas or liquid) flow in one direction, but is pushed up by the flow itself when the flow is moving in the opposite direction. This is called a check valve, as it prevents or "checks" the flow in one direction. Modern control valves may regulate pressure or flow downstream and operate on sophisticated automation systems. Valves have many uses, including controlling water for irrigation, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fishing Trawler
A fishing trawler is a commercial fishing vessel designed to operate Trawling, fishing trawls. Trawling is a method of fishing that involves actively dragging or pulling a trawl through the water behind one or more trawlers. Trawls are fishing nets that are pulled along the bottom of the sea or in midwater at a specified depth. A trawler may also operate two or more trawl nets simultaneously (double-rig and multi-rig). There are many variants of trawling gear. They vary according to local traditions, bottom conditions, and how large and powerful the trawling boats are. A trawling boat can be a small open boat with only 30 horsepower (22 kW) or a large factory ship with 10,000 horsepower (7457 kW). Trawl variants include beam trawls, large-opening midwater trawls, and large bottom trawls, such as "rock hoppers" that are rigged with heavy rubber wheels that let the net crawl over rocky bottom. History During the 17th century, the British developed the Dogge ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Naval Trawler
Naval trawlers are vessels built along the lines of a fishing trawler but fitted out for naval purposes; they were widely used during the First and Second World Wars. Some—known in the Royal Navy as "Admiralty trawlers"— were purpose-built to naval specifications, others adapted from civilian use. Fishing trawlers were particularly suited for many naval requirements because they were robust vessels designed to work heavy trawls in all types of weather, and had large clear working decks. A minesweeper could be created by replacing the trawl with a mine sweep. Adding depth charge racks on the deck, ASDIC sonar below, and a or gun in the bow equipped the trawler for anti-submarine duties. History Armed trawlers were also used to defend fishing groups from enemy aircraft or submarines. The smallest civilian trawlers were converted to danlayers. Contemporary Some nations still use armed trawlers for fisheries protection and patrol. The Indian Navy used naval trawlers for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Steam Engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid. The steam engine uses the force produced by steam pressure to push a piston back and forth inside a cylinder. This pushing force can be transformed, by a connecting rod and crank, into rotational force for work. The term "steam engine" is generally applied only to reciprocating engines as just described, not to the steam turbine. Steam engines are external combustion engines, where the working fluid is separated from the combustion products. The ideal thermodynamic cycle used to analyze this process is called the Rankine cycle. In general usage, the term ''steam engine'' can refer to either complete steam plants (including boilers etc.), such as railway steam locomotives and portable engines, or may refer to the piston or turbine machinery alone, as in the beam engine and stationary steam engine. Although steam-driven devices were known as early as the aeolipile in the f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Wren And Holman Projector 1943 IWM A 20405
Wrens are a family of brown passerine birds in the predominantly New World family Troglodytidae. The family includes 88 species divided into 19 genera. Only the Eurasian wren occurs in the Old World, where, in Anglophone regions, it is commonly known simply as the "wren", as it is the originator of the name. The name ''wren'' has been applied to other, unrelated birds, particularly the New Zealand wrens (Acanthisittidae) and the Australian wrens (Maluridae). Most wrens are visually inconspicuous though they have loud and often complex songs. Exceptions include the relatively large members of the genus ''Campylorhynchus'', which can be quite bold in their behaviour. Wrens have short wings that are barred in most species, and they often hold their tails upright. Wrens are primarily insectivorous, eating insects, spiders and other small invertebrates, but many species also eat vegetable matter and some eat small frogs and lizards. Etymology and usage The English name "wren" derive ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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-Fliegerabteilung'' of the Imperial Navy, had been disbanded in May 1920 in accordance with the terms of the 1919 Treaty of Versailles which banned Germany from having any air force. During the interwar period, German pilots were trained secretly in violation of the treaty at Lipetsk Air Base in the Soviet Union. With the rise of the Nazi Party and the repudiation of the Versailles Treaty, the ''Luftwaffe''s existence was publicly acknowledged on 26 February 1935, just over two weeks before open defiance of the Versailles Treaty through German rearmament and conscription would be announced on 16 March. The Condor Legion, a ''Luftwaffe'' detachment sent to aid Nationalist forces in the Spanish Civil War, provided the force with a valuable testing grou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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, molybdenum, nickel, niobium, titanium, tungsten, vanadium, zirconium, or any other element to be added to obtain a desired alloying effect; * the specified minimum for copper does not exceed 0.40%; * or the maximum content specified for any of the following elements does not exceed the percentages noted: manganese 1.65%; silicon 0.60%; copper 0.60%. The term ''carbon steel'' may also be used in reference to steel which is not stainless steel; in this use carbon steel may include alloy steels. High carbon steel has many different uses such as milling machines, cutting tools (such as chisels) and high strength wires. These applications require a much finer microstructure, which improves the toughness. Carbon steel is a popular metal choic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 impurities which allow cracks to pass straight through, grey cast iron has graphite flakes which deflect a passing crack and initiate countless new cracks as the material breaks, and ductile cast iron has spherical graphite "nodules" which stop the crack from further progressing. Carbon (C), ranging from 1.8 to 4 wt%, and silicon (Si), 1–3 wt%, are the main alloying elements of cast iron. Iron alloys with lower carbon content are known as steel. Cast iron tends to be brittle, except for malleable cast irons. With its relatively low melting point, good fluidity, castability, excellent machinability, resistance to deformation and wear resistance, cast irons have become an engineering material with a wide range of applications and are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fuse (explosives)
In an explosive, pyrotechnics, pyrotechnic device, or military munition, a fuse (or fuze) is the part of the device that initiates function. In common usage, the word fuse is used indiscriminately. However, when being specific (and in particular in a military context), the term ''fuse'' describes a simple pyrotechnic initiating device, like the cord on a firecracker whereas the term ''fuze'' is used when referring to a more sophisticated ignition device incorporating mechanical and/or electronics, electronic components, such as a proximity fuze for an M107 projectile, M107 artillery shell, magnetometer, magnetic or acoustic signature, acoustic fuze on a sea mine, spring-loaded grenade fuze, pencil detonator, or anti-handling device. History Documented evidence suggests that the earliest fuses were first used by the Song Chinese between the 10th and 12th centuries. After the Chinese invented gunpowder, they began adapting its explosive properties for use in military technology ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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. Development William Mills, a hand grenade designer from Sunderland, patented, developed and manufactured the "Mills bomb" at the Mills Munitions Factory in Birmingham, England, in 1915. The Mills bomb was inspired by an earlier design by Belgian captain Leon Roland, who later engaged in a patent lawsuit. Col. Arthur Morrow, a New Zealand Wars officer, also believed aspects of his patent were incorporated into the Mills Bomb. The Mills bomb was adopted by the British Army as its standard hand grenade in 1915 as the No. 5. The Mills bomb underwent numerous modifications. The No. 23 was a No. 5 with a rodded base plug which allowed it to be fired from a rifle. This concept evolved further with the No. 36, a variant with a detachable base ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
