Misplaced Pages

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101-542: It is an externally-powered, chain-driven, single-barrel weapon that may be fired in semi-automatic, burst, or automatic modes. It is fed by a metallic link belt and has dual-feed capability. The term chain gun derives from the use of a roller chain that drives the bolt back and forth. The gun can destroy lightly armored vehicles and aerial targets (such as helicopters and other slow-flying aircraft). It can also apply suppression fire against exposed troops, dug-in positions, and occupied built-up areas. The standard rate of fire

202-433: A diesel engine ; modern technology, including the use of turbo-charging , helps to overcome the lower power-to-weight ratio of diesel engines compared to petrol. Gas turbine (turboshaft) engines offer a very high power-to-weight ratio and were starting to find favour in the late 20th century – however, they offer very poor fuel consumption and as such some armies are switching from gas turbines back to diesel engines (i.e.

303-447: A main battle tank will normally be designed to take hits from other tank guns and anti-tank missiles , whilst light reconnaissance vehicles are often only armoured "just in case". Whilst heavier armour provides better protection, it makes vehicles less mobile (for a given engine power), limits its air-transportability, increases cost, uses more fuel and may limit the places it can go – for example, many bridges may be unable to support

404-494: A turret or cupola. The greater the recoil of the weapon on an AFV, the larger the turret ring needs to be. A larger turret ring necessitates a larger vehicle. To avoid listing to the side, turrets on amphibious vehicles are usually located at the centre of the vehicle. Grenade launchers provide a versatile launch platform for a plethora of munitions including, smoke , phosphorus, tear gas , illumination, anti-personnel, infrared and radar-jamming rounds. Turret stabilization

505-512: A "dry" PTFE spray, which forms a solid film after application and repels both particles and moisture. Chains operating at high speeds comparable to those on motorcycles should be used in conjunction with an oil bath. For modern motorcycles this is not possible, and most motorcycle chains run unprotected. Thus, motorcycle chains tend to wear very quickly relative to other applications. They are subject to extreme forces and are exposed to rain, dirt, sand and road salt. Motorcycle chains are part of

606-744: A British Army engineer. They were very popular with smaller countries. Some saw some combat (with limited success) in World War II. However, the vulnerability of their light armour eventually caused the concept to be abandoned. However, the German Army uses a modern design of air-transportable armoured weapons carriers, the Wiesel AWC , which resembles the concept of a tankette. The term "super-heavy tank" has been used to describe armoured fighting vehicles of extreme size, generally over 75 tonnes. Programs have been initiated on several occasions with

707-513: A March 2011 contract to add a directed energy weapon to the Mk 38 Mod 2 gun mount, known as the Mk 38 Mod 2 tactical laser system . The TLS combines a Boeing-designed solid-state laser with the existing BAE-manufactured Mk 38 mount to deliver high-precision accuracy against fast surface and air threats including speed boats and unmanned aerial vehicles (UAVs). Laser power levels can be adjusted depending on

808-763: A Vickers QF-1 "Pom-Pom" gun of 40 mm. The Germans fielded the Sd.Kfz. 10/4 and 6/2, cargo halftracks mounting single 20 mm or 37 mm AA guns (respectively) by the start of the war. Rocket launchers such as the Soviet Katyusha originated in the late 1930s. The Wehrmacht fielded self-propelled rocket artillery in World War II – the Panzerwerfer and Wurfrahmen 40 equipped half-track armoured fighting vehicles. Many modern multiple rocket launchers are self propelled by either truck or tank chassis. The level of armour protection between AFVs varies greatly –

909-439: A bicycle with derailleur gears can snap (or rather, come apart at the side-plates, since it is normal for the "riveting" to fail first) because the pins inside are not cylindrical, they are barrel-shaped. Contact between the pin and the bushing is not the regular line, but a point which allows the chain's pins to work its way through the bushing, and finally the roller, ultimately causing the chain to snap. This form of construction

1010-562: A broad one. Chains built up with a uniform type of link, narrow at one and broad at the other end, can be made with an odd number of links, which can be an advantage to adapt to a special chainwheel-distance; on the other side such a chain tends to be not so strong. Roller chains made using ISO standard are sometimes called "isochains". https://www.leonardodigitale.com/en/browse/Codex-atlanticus/0987-r/ Armored fighting vehicle An armoured fighting vehicle ( British English ) or armored fighting vehicle ( American English ) ( AFV )

1111-444: A camshaft inside an internal combustion engine) operate in clean environments, and thus the wearing surfaces (that is, the pins and bushings) are safe from precipitation and airborne grit, many even in a sealed environment such as an oil bath. Some roller chains are designed to have o-rings built into the space between the outside link plate and the inside roller link plates. Chain manufacturers began to include this feature in 1971 after

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1212-432: A chain (other than that of a bicycle) to wear until it breaks, since a worn chain leads to the rapid onset of wear on the teeth of the sprockets, with ultimate failure being the loss of all the teeth on the sprocket. The sprockets (in particular the smaller of the two) suffer a grinding motion that puts a characteristic hook shape into the driven face of the teeth. (This effect is made worse by a chain improperly tensioned, but

1313-743: A competitive development in 1972 simultaneously at Ford 's Aeronutronic Division with the PFB-25 (self-powered weapon) and the Hughes Helicopters ' Ordnance Division (externally-powered,) under the Summa Corporation as the Vehicle Rapid-Fire Weapons System-Successor , or VRFWS-S . This was essentially a power-driven gun firing similar 20 mm ammunition to the HS.820, the power-driven mechanism

1414-551: A high wear application (for instance if it is just transmitting motion from a hand-operated lever to a control shaft on a machine, or a sliding door on an oven), then one of the simpler types of chain may still be used. Conversely, where extra strength but the smooth drive of a smaller pitch is required, the chain may be "siamesed"; instead of just two rows of plates on the outer sides of the chain, there may be three ("duplex"), four ("triplex"), or more rows of plates running parallel, with bushings and rollers between each adjacent pair, and

1515-435: A highly mobile and protected fighting unit has been around for centuries; from Hannibal 's war elephants to Leonardo 's contraptions , military strategists endeavoured to maximize the mobility and survivability of their soldiers. Armoured fighting vehicles were not possible until internal combustion engines of sufficient power became available at the start of the 20th century. Modern armoured fighting vehicles represent

1616-608: A larger breech assembly, a high efficiency muzzle brake , longer recoil , an integral round counter, an extended life firing pin and spring, and a triple-spring drive clutch. Upgraded weapons were first put to use on the M2A3 Bradley, the fourth version of the M2 Bradley fighting vehicle. In 1977, the U. S. Navy realized that it needed a replacement for the Oerlikon 20 mm Mk 16 series of guns . In 1986, this requirement

1717-542: A larger manual fire control panel, an offset mode specifically for firing warning shots, and a surveillance mode where the gun can be pointed away from a target but the EO sensor remains pointed in the target direction. Although it has a high degree of commonality and has the same footprint as previous models, the upgrade is 20 percent heavier due to the greater ammo load. Roller chain Roller chain or bush roller chain

1818-445: A length of chain and a joining link (with horseshoe clip) will be provided as a spare. Changes in motorcycle suspension are tending to make this use less prevalent. Common on older motorcycles and older bicycles (e.g. those with hub gears ) this clip method cannot be used on bicycles fitted with derailleur gears, as the clip will tend to catch on the gear-changers. In many cases, an endless chain cannot be replaced easily since it

1919-892: A newer version, the Typhoon Weapon System designated Mk 38 Mod 2 , which is remotely operated and includes an electronic optical sight, laser range-finder, FLIR, and a more reliable feeding system, enhancing the weapon system's capabilities and accuracy. In 2006 the Sri Lanka Navy added the M242 to its fleet of fast attack craft . The system is also in use by the Republic of Singapore Navy 's Formidable -class frigates and Endurance -class landing platform dock ships and were deployed as part of coalition forces' port security efforts in Iraq as well as anti-piracy roles in

2020-467: A tank being first deployed as a medium tank, but in later years relegated to light tank roles. Tanks were also classified by roles that were independent of size, such as cavalry tank , cruiser tank , fast tank , infantry tank , "assault" tank, or "breakthrough" tank. Military theorists initially tended to assign tanks to traditional military infantry, cavalry, and artillery roles, but later developed more specialized roles unique to tanks. In modern use,

2121-414: A tank chassis. During World War II, most major military powers developed self-propelled artillery vehicles. These had guns mounted on a tracked chassis (often that of an obsolete or superseded tank) and provided an armoured superstructure to protect the gun and its crew. The first British design, "Bishop" , carried the 25 pdr gun-howitzer in an extemporised mounting on a tank chassis that severely limited

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2222-450: A very large movable siege tower, the helepolis , as early as 340 BC, and Greek forces used such structures in the Siege of Rhodes (305 BC). The idea of a protected fighting vehicle has been known since antiquity. Frequently cited is Leonardo da Vinci 's 15th-century sketch of a mobile, protected gun-platform ; the drawings show a conical, wooden shelter with apertures for cannons around

2323-488: A wide variety of both ground targets and air targets. Despite significant advances in anti-tank warfare , it still remains the most versatile and fearsome land-based weapon-systems of the 21st-century, valued for its shock action and high survivability . A tankette is a tracked armed and armoured vehicle resembling a small "ultra-light tank" or "super-light tank" roughly the size of a car, mainly intended for light infantry support or scouting . Tankettes were introduced in

2424-414: Is 200 rounds per minute. The weapon has an effective range of 2,000 metres (6,600  ft ), depending on the type of ammunition used. With over 11,000 units sold worldwide, it is one of the most successful modern autocannons. Unlike most automatic firearms , the M242 does not depend on gas or recoil to actuate its firing system. Instead, it uses a 1 hp (0.75 kW) DC motor , positioned in

2525-531: Is a simple, reliable, and efficient means of power transmission. Sketches by Leonardo da Vinci in the 16th century show a chain with a roller bearing . In 1800, James Fussell patented a roller chain on development of his balance lock and in 1880 Hans Renold patented a bush roller chain. There are two types of links alternating in the bush roller chain. The first type is inner links, having two inner plates held together by two sleeves or bushings upon which rotate two rollers. Inner links alternate with

2626-622: Is a tank fulfilling the role of a main battle tank, but using only anti-tank surface-to-surface missiles for main armament. Several nations have experimented with prototypes, notably the Soviet Union during the tenure of Nikita Khrushchev (projects Object 167, Object 137Ml, Object 155Ml, Object 287, Object 775), A flame tank is an otherwise-standard tank equipped with a flamethrower , most commonly used to supplement combined arms attacks against fortifications , confined spaces, or other obstacles. The type only reached significant use in

2727-399: Is also known as "cottered chain", which allows the length of the chain to be adjusted. Half links (also known as "offsets") are available and are used to increase the length of the chain by a single roller. Riveted roller chain has the master link (also known as a "connecting link") "riveted" or mashed on the ends. These pins are made to be durable and are not removable. A horseshoe clip is

2828-445: Is an armed combat vehicle protected by armour , generally combining operational mobility with offensive and defensive capabilities. AFVs can be wheeled or tracked . Examples of AFVs are tanks , armoured cars , assault guns , self-propelled artilleries , infantry fighting vehicles (IFV), and armoured personnel carriers (APC). Armoured fighting vehicles are classified according to their characteristics and intended role on

2929-430: Is an important capability because it enables firing on the move and prevents crew fatigue. Modern AFVs have primarily used either petrol (gasoline) or diesel piston engines. More recently, gas turbines have been used. Most early AFVs used petrol engines , as they offer a good power-to-weight ratio . However, they fell out of favour during World War II due to the flammability of the fuel. Most current AFVs are powered by

3030-426: Is distinguished by its high level of firepower, mobility and armour protection relative to other vehicles of its era. It can cross comparatively rough terrain at high speeds, but its heavy dependency on fuel, maintenance, and ammunition makes it logistically demanding. It has the heaviest armour of any AFVs on the battlefield, and carries a powerful precision-guided munition weapon systems that may be able to engage

3131-584: Is for the chain load to not exceed a mere 1/6 or 1/9 of the chain's tensile strength, depending on the type of master links used (press-fit vs. slip-fit) . Roller chains operating on a continuous drive beyond these thresholds can and typically do fail prematurely via linkplate fatigue failure. The standard minimum ultimate strength of the ANSI 29.1 steel chain is 12,500 x (pitch, in inches) . X-ring and O-Ring chains greatly decrease wear by means of internal lubricants, increasing chain life. The internal lubrication

M242 Bushmaster - Misplaced Pages Continue

3232-499: Is inserted by means of a vacuum when riveting the chain together. Standards organizations (such as ANSI and ISO ) maintain standards for design, dimensions, and interchangeability of transmission chains. For example, the following table shows data from ANSI standard B29.1-2011 (precision power transmission roller chains, attachments, and sprockets) developed by the American Society of Mechanical Engineers (ASME). See

3333-423: Is linked into the frame of the machine (this is the case on the traditional bicycle, amongst other places). However, in some cases, a joining link with horseshoe clip cannot be used or is not preferred in the application either. In this case, a "soft link" is used, placed with a chain riveter and relying solely on friction. With modern materials and tools and skilled application this is a permanent repair having almost

3434-411: Is necessary because the gear-changing action of this form of transmission requires the chain to both bend sideways and to twist, but this can occur with the flexibility of such a narrow chain and relatively large free lengths on a bicycle. Chain failure is much less of a problem on hub-geared systems since the chainline does not bend, so the parallel pins have a much bigger wearing surface in contact with

3535-674: Is standard equipment on the U. S. Army M2 and M3 Bradley fighting vehicles; it is also in use on the LAV-25 . Before the project was cancelled, the Mk44 Bushmaster II 30 mm chain gun (a successor to the M242) was used on the Marine Corps' Expeditionary Fighting Vehicle (EFV). The M242 is also a popular choice of primary armament for armored fighting vehicles manufactured around the world, such as Singapore's Bionix AFVs and as

3636-409: Is the quality of steel used to manufacture the chain, the heat treatment of the chain components, the quality of the pitch hole fabrication of the linkplates, and the type of shot plus the intensity of shot peen coverage on the linkplates. Other factors can include the thickness of the linkplates and the design (contour) of the linkplates. The rule of thumb for roller chain operating on a continuous drive

3737-415: Is the type of chain drive most commonly used for transmission of mechanical power on many kinds of domestic, industrial and agricultural machinery, including conveyors , wire - and tube - drawing machines, printing presses , cars , motorcycles , and bicycles . It consists of a series of short cylindrical rollers held together by side links. It is driven by a toothed wheel called a sprocket . It

3838-453: Is unavoidable no matter what care is taken). The worn teeth (and chain) no longer provides smooth transmission of power and this may become evident from the noise, the vibration or (in car engines using a timing chain) the variation in ignition timing seen with a timing light . Both sprockets and chain should be replaced in these cases, since a new chain on worn sprockets will not last long. However, in less severe cases it may be possible to save

3939-415: Is used in food processing machinery or other places where lubrication is a problem, and nylon or brass are occasionally seen for the same reason. Roller chain is ordinarily hooked up using a master link (also known as a "connecting link"), which typically has one pin held by a horseshoe clip rather than friction fit, allowing it to be inserted or removed with simple tools. Chain with a removable link or pin

4040-997: The Canadian Army , the Royal Canadian Navy , the Australian Army , the Royal Australian Navy , the Israeli Navy , the Philippine Navy , the Philippine Army , the Singapore Army , and the Republic of Singapore Navy as well as several others, including since 2023 the Armed Forces of Ukraine . The wide usage has resulted in several variations and modifications on the standard M242 weapon system. The M242

4141-531: The Gulf of Aden . Aside from that, the Singapore Police Coast Guard 's new coastal patrol craft (NCPC) has adopted the system as its main armament. The Mod 3 updates electronics and adds a coaxial 7.62 mm machine gun with a 570-round-per-minute rate of fire. Turkish made Aselsan STOP stabilized weapon station can be fitted with an M242 Bushmaster. BAE and Boeing teamed together after

M242 Bushmaster - Misplaced Pages Continue

4242-754: The Hispano-Suiza HS.820 20 mm autocannon. During the testing phase, the Army eventually rejected the XM701 and started work on a newer design known as the XM723. Soon after the XM800 was also rejected. This led to the combination of the two programs, moving the scout role to the cavalry version of the XM723. At the same time, the M139 proved to be disappointing and a contract for a new weapon to replace it started as

4343-755: The Hussite Wars . These heavy wagons were given protective sides with firing slits; their heavy firepower came from either a cannon or from a force of hand-gunners and crossbowmen , supported by light cavalry and infantry using pikes and flails . Heavy arquebuses mounted on wagons were called arquebus à croc . These carried a ball of about 3.5 ounces (100 g). By the end of World War II , most modern armies had vehicles to carry infantry, artillery and anti-aircraft weaponry . Most modern AFVs are superficially similar in design to their World War II counterparts, but with significantly better armour, weapons, engines, electronics, and suspension. The increase in

4444-607: The MOWAG Piranha , originally designed as an APC, has been adapted to fill numerous roles such as a mortar carrier , infantry fighting vehicle, and assault gun. Armoured fighting vehicles began to appear in use in World War I with the armoured car, the tank, the self-propelled gun, and the personnel carrier seeing use. By World War II, armies had large numbers of AFVs, together with other vehicles to carry troops this permitted highly mobile manoeuvre warfare . The concept of

4545-1128: The NATO equivalents thereof. Primarily though, it fires six types of rounds: the M791, M792, M793, M910, MK210, and M919. The M242 is currently in use by the United States Army , the United States Navy , the United States Marine Corps , the United States Coast Guard , the New Zealand Army , the Royal New Zealand Navy , the Norwegian Army , the Spanish Army , the Sri Lanka Navy , the Swiss Army ,

4646-497: The Rafael Overhead Weapon Station-25 mounted on upgraded M113A2 Ultra IFVs . Work on an upgraded weapon began in 1990. In the upgrade program, all three major systems and seven minor systems were improved. The modifications began with introducing a chrome-lined barrel, an enhanced feeder, and an enhanced receiver. The weapon systems also received minor upgrades such as quick-detachable link covers,

4747-776: The Russian Marines with the PT-76 , the British Army with the Scimitar , and the Chinese Army with the Type 63 . Modern main battle tanks or "universal tanks" incorporate recent advances in automotive, artillery, armour, and electronic technology to combine the best characteristics of the historic medium and heavy tanks into a single, all-around type. They are also the most expensive to mass-produce. A main battle tank

4848-484: The Second World War (1939–1945). The armoured personnel carrier, designed to transport infantry troops to the frontline, emerged towards the end of World War I. During the first actions with tanks , it had become clear that close contact with infantry was essential in order to secure ground won by the tanks. Troops on foot were vulnerable to enemy fire, but they could not be transported in the tank because of

4949-597: The Second World War , during which the United States, Soviet Union , Germany , Italy , Japan and the United Kingdom (including members of the British Commonwealth ) all produced flamethrower-equipped tanks. Usually, the flame projector replaced one of the tank's machineguns, however, some flame projectors replaced the tank's main gun. Fuel for the flame weapon was generally carried inside

5050-406: The receiver to drive the chain and dual-feed system. This system uses sprockets and extractor grooves to feed, load, fire, extract, and eject rounds. A system of clutches provides for an alternate sprocket to engage and thus allows the gunner to switch between armor-piercing and high-explosive rounds . The weapon assembly consists of three parts: the barrel assembly, the feeder assembly, and

5151-514: The Russian T-80 used a gas turbine engine, whereas the later T-90 does not). The US M1 Abrams is a notable example of a gas turbine powered tank. Notable armoured fighting vehicles extending from post-World War I to today. The tank is an all terrain AFV incorporating artillery which is designed to fill almost all battlefield roles and to engage enemy forces by the use of direct fire in

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5252-487: The U-shaped spring steel fitting that holds the side-plate of the joining (or "master") link formerly essential to complete the loop of a roller chain. The clip method is losing popularity as more and more chains are manufactured as endless loops not intended for maintenance. Modern motorcycles are often fitted with an endless chain but in the increasingly rare circumstances of the chain wearing out and needing to be replaced,

5353-600: The aim of creating an invincible siegeworks / breakthrough vehicle for penetrating enemy formations and fortifications without fear of being destroyed in combat. Examples were designed in World War I and World War II (such as the Panzer VIII Maus ), along with a few in the Cold War . However, few working prototypes were built and there is no clear evidence any of these vehicles saw combat, as their immense size would have made most designs impractical. A missile tank

5454-401: The application was invented by Joseph Montano while working for Whitney Chain of Hartford, Connecticut. O-rings were included as a way to improve lubrication to the links of power transmission chains, a service that is vitally important to extending their working life. These rubber fixtures form a barrier that holds factory applied lubricating grease inside the pin and bushing wear areas. Further,

5555-400: The battlefield. The classifications are not absolute; two countries may classify the same vehicle differently, and the criteria change over time. For example, relatively lightly armed armoured personnel carriers were largely superseded by infantry fighting vehicles with much heavier armament in a similar role. Successful designs are often adapted to a wide variety of applications. For example,

5656-409: The bottom of the hull. Weaponry varies by a very wide degree between AFVs – lighter vehicles for infantry carrying, reconnaissance or specialist roles may have only a autocannon or machine gun (or no armament at all), whereas heavy self-propelled artillery will carry howitzers , mortars or rocket launchers. These weapons may be mounted on a pintle , affixed directly to the vehicle or placed in

5757-413: The bush. The hub-gear system also allows complete enclosure, a great aid to lubrication and protection from grit. The most common measure of roller chain's strength is tensile strength . Tensile strength represents how much load a chain can withstand under a one-time load before breaking. Just as important as tensile strength is a chain's fatigue strength. The critical factors in a chain's fatigue strength

5858-484: The capacity of transport aircraft makes possible and practicable the transport of AFVs by air. Many armies are replacing some or all of their traditional heavy vehicles with lighter airmobile versions, often with wheels instead of tracks. The first modern AFVs were armed cars, dating back virtually to the invention of the motor car . The British inventor F. R. Simms designed and built the Motor Scout in 1898. It

5959-425: The chain and provided rolling contact with the teeth of the sprockets resulting in excellent resistance to wear of both sprockets and chain as well. There is even very low friction, as long as the chain is sufficiently lubricated. Continuous, clean, lubrication of roller chains is of primary importance for efficient operation, as is correct tensioning. Many driving chains (for example, in factory equipment, or driving

6060-424: The chain. The roller chain design reduces friction compared to simpler designs, resulting in higher efficiency and less wear. The original power transmission chain varieties lacked rollers and bushings, with both the inner and outer plates held by pins which directly contacted the sprocket teeth; however this configuration exhibited extremely rapid wear of both the sprocket teeth and the plates where they pivoted on

6161-627: The circumference. The machine was to be mounted on four wheels which would be turned by the crew through a system of hand cranks and cage (or "lantern") gears . Leonardo claimed: "I will build armoured wagons which will be safe and invulnerable to enemy attacks. There will be no obstacle which it cannot overcome." Modern replicas have demonstrated that the human crew would have been able to move it over only short distances. Hussite forces in Bohemia developed war wagons – medieval horse-drawn wagons that doubled as wagon forts – around 1420 during

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6262-414: The cycle or motorcycle user, is to attempt to pull the chain away from the larger of the two sprockets, whilst ensuring the chain is taut. Any significant movement (e.g. making it possible to see through a gap) probably indicates a chain worn up to and beyond the limit. Sprocket damage will result if the problem is ignored. Sprocket wear cancels this effect, and may mask chain wear. The lightweight chain of

6363-410: The drive train to transmit the motor power to the back wheel. Properly lubricated chains can reach an efficiency of 98% or greater in the transmission. Unlubricated chains will significantly decrease performance and increase chain and sprocket wear. Two types of aftermarket lubricants are available for motorcycle chains: spray on lubricants and oil drip feed systems. If the chain is not being used for

6464-649: The first Self-propelled artillery , was fielded in 1917. It was based on the first tank, the British Mark I , and carried a heavy field-gun. The next major advance was the Birch gun (1925), developed for the British motorised warfare experimental brigade (the Experimental Mechanized Force ). This mounted a field gun, capable of the usual artillery trajectories and even anti-aircraft use, on

6565-438: The frontal assault role. Though several configurations have been tried, particularly in the early experimental "golden days" of tank development, a standard, mature design configuration has since emerged to a generally accepted pattern. This features a main tank gun or artillery gun , mounted in a fully rotating turret atop a tracked automotive hull, with various additional secondary weapon systems throughout. Philosophically,

6666-438: The gun from weather and allows for easier access to internal components through large access panels. The upgrade mounts a larger Alliant Techsystems Mk44 Bushmaster II 30 mm cannon for a 500-meter range increase, as well as a coaxial .50 caliber M2 heavy machine gun . Elevation is increased to +75 degrees for engaging UAVs and helicopters, and ammunition storage is greater at 420 30 mm rounds. Other features include

6767-690: The gun's performance. It was replaced by the more effective Sexton . The Germans built many lightly armoured self-propelled anti-tank guns using captured French equipment (for example Marder I ), their own obsolete light tank chassis ( Marder II ), or ex-Czech chassis ( Marder III ). These led to better-protected tank destroyers, built on a medium-tank chassis such as the Jagdpanzer IV or the Jagdpanther . The Self-propelled anti-aircraft weapon debuted in WWI. The German 88  mm anti-aircraft gun

6868-400: The heavy tank has fallen out of favour, being supplanted by more heavily armed and armoured descendant of the medium tanks – the universal main battle tank . The light tank has, in many armies, lost favour to cheaper, faster, lighter armoured cars ; however, light tanks (or similar vehicles with other names) are still in service with a number of forces as reconnaissance vehicles , most notably

6969-498: The individual vehicle too, depending on the role of the vehicle and the likely direction of attack. For example, a main battle tank will usually have the heaviest armour on the hull front and the turret, lighter armour on the sides of the hull and the thinnest armour on the top and bottom of the tank. Other vehicles – such as the MRAP family – may be primarily armoured against the threat from IEDs and so will have heavy, sloped armour on

7070-515: The intense heat and noxious atmosphere. In 1917, Lieutenant G. J. Rackham was ordered to design an armoured vehicle that could fight and carry troops or supplies. The Mark IX tank was built by Armstrong, Whitworth & Co. , although just three vehicles had been finished at the time of the Armistice in November 1918, and only 34 were built in total. Different tank classifications emerged in

7171-792: The interwar period. The tankette was conceived as a mobile, two-man model, mainly intended for reconnaissance. In 1925, Sir John Carden and Vivian Loyd produced the first such design to be adopted – the Carden Loyd tankette . Tankettes saw use in the Royal Italian Army during the Italian invasion of Ethiopia (1935–1936), the Spanish Civil War (1936–1939), and almost everywhere Italian soldiers fought during World War II . The Imperial Japanese Army used tankettes for jungle warfare . The British Gun Carrier Mark I ,

7272-546: The larger of the two sprockets, since it is always the smaller one that suffers the most wear. Only in very light-weight applications such as a bicycle, or in extreme cases of improper tension, will the chain normally jump off the sprockets. The lengthening due to wear of a chain is calculated by the following formula: % = ( ( M − ( S ∗ P ) ) / ( S ∗ P ) ) ∗ 100 {\displaystyle \%=((M-(S*P))/(S*P))*100} M =

7373-424: The last digit being 0 for standard chain, 1 for lightweight chain, and 5 for bushed chain with no rollers. Thus, a chain with half-inch pitch is a No. 40 while a No. 160 sprocket has teeth spaced 2 inches apart, etc. Metric pitches are expressed in sixteenths of an inch; thus a metric No. 8 chain (08B-1) is equivalent to an ANSI No. 40. Most roller chain is made from plain carbon or alloy steel, but stainless steel

7474-400: The length of a number of links measured S = the number of links measured P = Pitch In industry, it is usual to monitor the movement of the chain tensioner (whether manual or automatic) or the exact length of a drive chain (one rule of thumb is to replace a roller chain which has elongated 3% on an adjustable drive or 1.5% on a fixed-center drive). A simpler method, particularly suitable for

7575-502: The load capacity. The more sprockets at the rear wheel (historically 3–6, nowadays 7–12 sprockets), the narrower the chain. Chains are sold according to the number of speeds they are designed to work with, for example, "10 speed chain". Hub gear or single speed bicycles use 1/2 x 1/8 inch chains, where 1/8 inch refers to the maximum thickness of a sprocket that can be used with the chain. Typically chains with parallel shaped links have an even number of links, with each narrow link followed by

7676-716: The majority of armored vehicles it is likely to encounter, up to and including some light tanks , including an encounter during the war in Ukraine where a Russian T-90M main battle tank was forced to be abandoned. The ammunition used in the M242 may also be used in a variety of weapons such as the GAU-12 Equalizer , the French Giat M811 , or the Swiss Oerlikon KBA weapon system. It has the capability to fire U.S. manufactured ammunition as well as

7777-483: The mid-1920s as a reconnaissance vehicle and a mobile machine gun position They were one or two-man vehicles armed with a machine gun. Colloquially it may also simply mean a "small tank". Tankettes were designed and built by several nations between the 1920s and 1940s following the British Carden Loyd tankette which was a successful implementation of "one man tank" ideas from Giffard Le Quesne Martel ,

7878-515: The muddy, pocked terrain and slit trenches of the Battle of the Somme . The tank eventually proved highly successful and, as technology improved, it became a weapon that could cross large distances at much higher speeds than supporting infantry and artillery . The need to provide the units that would fight alongside the tank led to the development of a wide range of specialised AFVs, especially during

7979-484: The opposing force who can often hear and even feel their arrival. Tanks were classified either by size or by role. Classification by relative size was common, as this also tended to influence the tanks' role. Over time, tanks tended to be designed with heavier armour and weapons, increasing the weight of all tanks, so these classifications are relative to the average for the nation's tanks for any given period. An older tank design might be reclassified over time, such as

8080-416: The pins. This problem was partially solved by the development of bushed chains, with the pins holding the outer plates passing through bushings or sleeves connecting the inner plates. This distributed the wear over a greater area; however the teeth of the sprockets still wore more rapidly than is desirable, from the sliding friction against the bushings. The addition of rollers surrounding the bushing sleeves of

8181-527: The realization of an ancient concept – that of providing troops with mobile protection and firepower. Armies have deployed war machines and cavalries with rudimentary armour in battle for millennia. Use of these animals and engineering designs sought to achieve a balance between the conflicting paradoxical needs of mobility, firepower and protection. Siege engines , such as battering rams and siege towers , would often be armoured in order to protect their crews from enemy action. Polyidus of Thessaly developed

8282-490: The receiver assembly. The three-part structure makes it possible for a two-person team to install or remove the system (under ideal conditions) despite its considerable total weight. The M242 weapon system has both electrical and manual fire control and can be operated electrically or manually. The gunner can choose from three rates of fire: The Bushmaster project started as an offshoot of the US Army 's MICV-65 program that

8383-426: The references for additional information. For mnemonic purposes, below is another presentation of key dimensions from the same standard, expressed in fractions of an inch (which was part of the thinking behind the choice of preferred numbers in the ANSI standard): A typical bicycle chain (for derailleur gears ) uses narrow 1 ⁄ 2 -inch-pitch chain. The width of the chain is variable, and does not affect

8484-595: The rubber o-rings prevent dirt and other contaminants from entering inside the chain linkages, where such particles would otherwise cause significant wear. There are also many chains that have to operate in dirty conditions, and for size or operational reasons cannot be sealed. Examples include chains on farm equipment , bicycles, and chain saws . These chains will necessarily have relatively high rates of wear. Many oil-based lubricants attract dirt and other particles, eventually forming an abrasive paste that will compound wear on chains. This problem can be reduced by use of

8585-403: The same number of rows of teeth running in parallel on the sprockets to match. Timing chains on automotive engines, for example, typically have multiple rows of plates called strands. Roller chain is made in several sizes, the most common American National Standards Institute (ANSI) standards being 40, 50, 60, and 80. The first digits indicate the pitch of the chain in eighths of an inch , with

8686-413: The same strength and life of the unbroken chain. The effect of wear on a roller chain is to increase the pitch (spacing of the links), causing the chain to grow longer. Note that this is due to wear at the pivoting pins and bushes, not from actual stretching of the metal (as does happen to some flexible steel components such as the hand-brake cable of a motor vehicle). With modern chains it is unusual for

8787-445: The second type, the outer links, consisting of two outer plates held together by pins passing through the bushings of the inner links. The "bushingless" roller chain is similar in operation though not in construction; instead of separate bushings or sleeves holding the inner plates together, the plate has a tube stamped into it protruding from the hole which serves the same purpose. This has the advantage of removing one step in assembly of

8888-439: The tank is, by its very nature, an offensive weapon. Being a protective encasement with at least one gun position, it is essentially a pillbox or small fortress (though these are static fortifications of a purely defensive nature) that can move toward the enemy – hence its offensive utility. Psychologically, the tank is a force multiplier that has a positive morale effect on the infantry it accompanies. It also instills fear in

8989-613: The tank, although a few designs mounted the fuel externally, such as the armoured trailer used on the Churchill Crocodile . Flame tanks have been superseded by thermobaric weapons such as the Russian TOS-1 . The idea for this tank was developed during World War I by British and French. The infantry tank was designed to work in concert with infantry in the assault, moving mostly at a walking pace, and carrying heavy armour to survive defensive fire. Its main purpose

9090-452: The target and mission objectives. Originally, the system was armed with a 10 kW laser, but in April 2017 BAE announced they had increased power to 60 kW. In April 2012, BAE unveiled a potential version of the system mount, developed in collaboration with Rafael Advanced Defense Systems . It is visually distinctive from previous versions with its stealthy housing, which also protects

9191-407: The weapon, resulting in the enhanced 25 mm gun . To date, more than 10,500 weapons are in service. One of the major reasons for this popularity is the extremely reliable nature of the weapon. It has a rating of 22,000 mean rounds between failure (MRBF), much higher than many comparable devices. A wide range of ammunition has been developed for this weapon, providing it with the capability to defeat

9292-475: The weight of a main battle tank. A trend toward composite armour is taking the place of steel – composites are stronger for a given weight, allowing the tank to be lighter for the same protection as steel armour, or better protected for the same weight. Armour is being supplemented with active protection systems on a number of vehicles, allowing the AFV to protect itself from incoming projectiles. The level of protection also usually varies considerably throughout

9393-664: Was attempting to introduce a new infantry fighting vehicle to replace their existing M113 armored personnel carriers . Part of this program called for a new scout vehicle to replace the M114 , a parallel development taking place under the XM800 Armored Reconnaissance Scout Vehicle . Both the XM800 and the cavalry version of the XM701 MICV vehicles were armed with the M139 , a US-built version of

9494-442: Was equipped with a Hotchkiss machine gun , and with 7 mm armour for the gunner. Armoured cars were first used in large numbers on both sides during World War I as scouting vehicles. In 1903, H. G. Wells published the short story " The Land Ironclads ," positing indomitable war machines that would bring a new age of land warfare, the way steam-powered ironclad warships had ended the age of sail . Wells's literary vision

9595-607: Was powered by a four-cylinder 3.3-litre 16 hp Cannstatt Daimler engine giving it a maximum speed of around 9 miles per hour (14 kilometres per hour). The armament, consisting of two Maxim guns, was carried in two turrets with 360° traverse. Another early armoured car of the period was the French Charron, Girardot et Voigt 1902 , presented at the Salon de l'Automobile et du cycle in Brussels , on 8 March 1902. The vehicle

9696-645: Was realized in 1916, when, amidst the pyrrhic standstill of the Great War , the British Landship Committee deployed revolutionary armoured vehicles to break the stalemate. The tank was envisioned as an armoured machine that could cross ground under fire from machine guns and reply with its own mounted machine guns and naval artillery . These first British tanks of World War I moved on caterpillar tracks that had substantially lower ground pressure than wheeled vehicles, enabling them to pass

9797-521: Was satisfied with the introduction of the Mk 38 Mod 0 weapons system. A derivative of the M242 system, the Mk 38 consists of the M242 chain gun and the Mk 88 Mod 0 machine gun mount. It provides ships with defensive and offensive gunfire capability for the engagement of a variety of surface targets. Designed primarily as a close-range defensive measure, it provides protection against patrol boats , floating mines , and various shore-based targets. Recently, several US Navy platforms have been outfitted with

9898-582: Was the first armed, petrol-engine powered vehicle ever built. It consisted of a De Dion-Bouton quadracycle with a Maxim machine gun mounted on the front bar. An iron shield offered some protection for the driver from the front, but it lacked all-around protective armour. The armoured car was the first modern fully armoured fighting vehicle. The first of these was the Simms's Motor War Car , also designed by Simms and built by Vickers, Sons & Maxim in 1899. The vehicle had Vickers armour 6 mm thick and

9999-667: Was to ensure operation even in the case of a misfire. Progress on the VRFWS-S was slow, and eventually resulted in a switch to a much more powerful, 25 mm, round. Similar delays in the MICV program meant the ultimate vehicles descending from their efforts, the M2/M3 Bradley fighting vehicle, did not enter production until 1981, by which point the Bushmaster had matured. Since 1990, there have been several enhancements made upon

10100-507: Was to suppress enemy fire, crush obstacles such as barbed-wire entanglements, and protect the infantry on their advance into and through enemy lines by giving mobile overwatch and cover . The French Renault FT was the first iteration of this concept. The British and French retained the concept between the wars and into the Second World War era. Because infantry tanks did not need to be fast, they could carry heavy armour. One of

10201-567: Was truck-mounted and used to great effect against British tanks, and the British QF 3-inch 20 cwt was mounted on trucks for use on the Western Front . Although the Birch gun was a general purpose artillery piece on an armoured tracked chassis, it was capable of elevation for anti-aircraft use. Vickers Armstrong developed one of the first SPAAGs based on the chassis of the Mk.E 6-ton light tank/ Dragon Medium Mark IV tractor , mounting

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