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58-410: The T-70 was armed with a 45-mm L/46 gun Model 38 with forty-five rounds carried, and a coaxial 7.62-mm DT machine gun . The tank was operated by a driver and a commander who loaded and fired the gun. Armour thickness on the turret front was 60 mm, turret sides and rear: 35 mm, hull front and sides: 45 mm, roof and bottom: 10 mm. By 1942, light tanks were considered inadequate by

116-420: A body in space is defined by six parameters. Three of the parameters define the origin of the moving reference frame relative to the fixed frame. Three other parameters define the orientation of the moving frame relative to the fixed frame. A linkage is a collection of links connected by joints. Generally, the links are the structural elements and the joints allow movement. Perhaps the single most useful example

174-503: A coaxial machine gun mounted to fire along a parallel axis to the main gun. Coaxial weapons are usually aimed by use of the main gun control. It is usually used to engage infantry or other "soft" targets where use of shots from the main gun would be dangerous, ineffective or wasteful. Some weapons such as the M40 recoilless rifle and the Mk 153 Shoulder-Launched Multipurpose Assault Weapon have

232-486: A frame, fasteners, bearings, springs, or lubricants; Various machine elements , such as splines, pins, or keys. German scientist Franz Reuleaux defines machine as "a combination of resistant bodies so arranged that by their means the mechanical forces of nature can be compelled to do work accompanied by certain determinate motion". In this context, his use of machine is generally interpreted to mean mechanism . The combination of force and movement defines power , and

290-413: A heavier mounting referred to as a pedestal , and even larger guns a turntable platform: a pedestal mount may be directly manipulated, but larger guns typically require the use of mechanical handwheels or hydraulic / electric actuator assistance for traversing and elevation adjustments. Very large mounts might also include seats for the crew fixed to the gun cradle or the floor of the turntable. Unlike

348-473: A limited-traverse gun mount: typically, this takes the form of either a gun mounted through a fixed armour plate (typically seen on tank destroyers and assault guns ) or a mount consisting of a partial cylinder of armour "sandwiched" between plates at the top and bottom (as with the sponson guns of early tanks and the secondary armament of Dreadnought-era battleships). A coaxial mount , pioneered on T1 Light Tank in late 1920s and widely adopted by late 1930s,

406-504: A link are assumed to not change as the mechanism moves—that is, the link does not flex. Thus, the relative movement between points in two connected links is considered to result from the kinematic pair that joins them. Kinematic pairs, or joints, are considered to provide ideal constraints between two links, such as the constraint of a single point for pure rotation, or the constraint of a line for pure sliding, as well as pure rolling without slipping and point contact with slipping. A mechanism

464-409: A mechanism manages power to achieve a desired set of forces and movement. A mechanism is usually a piece of a larger process, known as a mechanical system or machine . Sometimes an entire machine may be referred to as a mechanism; examples are the steering mechanism in a car , or the winding mechanism of a wristwatch . However, typically, a set of multiple mechanisms is called a machine. From

522-460: A monopod integrated into their stock, providing the effect of a tripod when it is combined with a frontal bipod. A bipod has two legs and provides stability along the left-to-right coordinate axis of motion. The bipod permits the operator to rest the weapon on the ground, a low wall, or other object, reducing operator fatigue and permitting increased accuracy. Bipods can be of fixed or adjustable length, and can either be an accessory mounted to

580-445: A shot from somewhere other than the prone position. Prior to their introduction, snipers had only shooting sticks or jury-rigged setups to use. Shooting sticks are portable weapon mounts used by field shooters, like hunters, snipers and metallic silhouette black-powder rifle shooters . They can be anything from purpose-built rests to constructions made from actual sticks, and have between one and three legs. They have existed since

638-423: A skeleton diagram that emphasises the joints and reduces the links to simple geometric elements. This diagram can also be formulated as a graph by representing the links of the mechanism as edges and the joints as vertices of the graph. This version of the kinematic diagram has proven effective in enumerating kinematic structures in the process of machine design. An important consideration in this design process

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696-468: A smaller caliber spotting rifle mounted in coaxial fashion to the barrel or launch tube. These weapons fire special cartridges designed to mimic the ballistic arc of the host weapon's ammunition, using tracer or point-detonating rounds so that a gunner can easily determine where a shot will land in order to place fire accurately. Due to the adoption of more advanced systems such as laser rangefinders, they are rarely used on modern weapons. A fixed mount

754-404: A standardised set of locking lugs to which many different types of armament can be affixed. Fixed traverse mounts capable of only elevation are common on larger self-propelled guns, as well being the mounting method used by virtually all railroad guns. A pintle mount is a swiveling mount that allows the gun to be freely traversed or elevated, while the base of the mount is still fixed keeping

812-425: A subset of compliant mechanisms that produce a geometrically well-defined motion (rotation) on application of a force. A cam and follower mechanism is formed by the direct contact of two specially shaped links. The driving link is called the cam and the link that is driven through the direct contact of their surfaces is called the follower. The shape of the contacting surfaces of the cam and follower determines

870-491: A turret, this type of mount typically has little or no armour protection, usually at most a frontal gun shield . This is a power-assisted mounting on the outside of whatever it is mounted on, usually bolted down to the surface and with only the control wires crossing the armour. Such mountings are typically used on armoured fighting vehicles for anti-personnel weapons to avoid exposing a crewmen to return fire, and on naval vessels for self-contained CIWS systems. A swing mount

928-421: Is a fixed mount that allows a far greater and more flexible arc of fire than the simple pintle mount system. Utilising a system of one or two articulated arms the gunner can swing the weapon through a wide arc even though the gunner's position is fixed relative to the mount. These systems vary in complexity from a simple arm, to a double arm with the ability to lock the weapon in any firing position. A mobile mount

986-442: Is a two degree-of-freedom joint. It is possible to construct a mechanism such that the point trajectories in all components lie in concentric spherical shells around a fixed point. An example is the gimbaled gyroscope . These devices are called spherical mechanisms. Spherical mechanisms are constructed by connecting links with hinged joints such that the axes of each hinge pass through the same point. This point becomes centre of

1044-503: Is a weapon mount that is portable or can be transported around by infantry . Large weapons that cannot easily be lifted by infantry require a platform that can be moved around when mobility is needed. Wheels are typically used to allow maneuverability, although skids are sometimes preferred in cold climates where icy/snowy surfaces become problematic for wheels, and some particularly heavy guns have historically used unpowered tracks . Small carriages can be pushed/pulled by hands in

1102-403: Is an assembly or mechanism used to hold a weapon (typically a gun ) onto a platform in order for it to function at maximum capacity. Weapon mounts can be broken down into two categories: static mounts and non-static mounts. A static mount is a non-portable weapon support component either mounted directly to the ground, on a fortification, or as part of a vehicle. A gun turret protects

1160-432: Is an extremely small sub-turret or sub-sub-turret mounted on a cupola turret. Typically the gun is fixed on its horizontal axis and rotated by turning the turret, with trunnions on the gun used to allow it to elevate. Alternatively, in an oscillating turret the entire upper section of the turret moves to elevate and depress the gun. A casemate is an armoured structure consisting of a static primary surface incorporating

1218-485: Is an ideal joint that has surface contact between the pair of elements, as in the following cases: Higher pairs: Generally, a higher pair is a constraint that requires a line or point contact between the elemental surfaces. For example, the contact between a cam and its follower is a higher pair called a cam joint . Similarly, the contact between the involute curves that form the meshing teeth of two gears are cam joints. A kinematic diagram reduces machine components to

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1276-405: Is incapable of horizontal movement (traverse), though not necessarily incapable of vertical movement (elevation). The entire mounting must be moved in order to change direction of fire. Fully fixed mounts (no traverse or elevation) are most commonly found on aircraft, and most commonly direct the weapon forward, along the aircraft's vector of movement, so that a pilot can aim by pointing the nose of

1334-402: Is modelled as an assembly of rigid links and kinematic pairs. Reuleaux called the ideal connections between links kinematic pairs . He distinguished between higher pairs , with line contact between the two links, and lower pairs , with area contact between the links. J. Phillips shows that there are many ways to construct pairs that do not fit this simple model. Lower pair: A lower pair

1392-459: Is most commonly found on armoured vehicles , improvised fighting vehicles such as technicals , side gun stations on WW2 and earlier-era bomber aircraft , and the door guns of armed transport helicopters . Early single-shot examples referred to as swivel guns were commonly mounted on the deck rails of naval vessels in the Age of Sail to deter boarders at close range. Larger guns require

1450-496: Is mounted beside or above the primary weapon and thus points in the same general direction as the main armament, relying on the host weapon's ability to traverse in order to change arc. The term coaxial is something of a misnomer as the arrangement is strictly speaking paraxial (i.e., parallel axes, as opposed to the same axis ), though for ballistic purposes the axis is effectively the same in practical terms. Nearly all main battle tanks and most infantry fighting vehicles have

1508-432: Is mounted to the outside of the vehicle's armour) it is an installation. Turrets are typically used to mount machine guns , autocannons or large- calibre guns. They may be manned or remotely controlled. A small turret, or sub-turret on a larger one, is called a cupola . The term cupola also describes rotating turrets that carry no weapons but instead are sighting devices, as in the case of tank commanders. A finial

1566-449: Is often, though not always, used with a two-legged stand to elevate the barrel at a desired angle. A monopod has one leg and does not provide stability along the coordinate axis of motion. Monopods have the advantage of being light and compact although when used in firing mode it does not have enough stability to be used with large firearms. Monopods are typically used on short-barreled, precision-fire firearms. Many sniper rifles feature

1624-538: Is that the follower moves slightly and helps to rotate the cam six times more circumference length with 70% of the force. The transmission of rotation between contacting toothed wheels can be traced back to the Antikythera mechanism of Greece and the south-pointing chariot of China. Illustrations by the Renaissance scientist Georgius Agricola show gear trains with cylindrical teeth. The implementation of

1682-467: Is the degree of freedom of the system of links and joints, which is determined using the Chebychev–Grübler–Kutzbach criterion . While all mechanisms in a mechanical system are three-dimensional, they can be analysed using plane geometry if the movement of the individual components is constrained so that all point trajectories are parallel or in a series connection to a plane. In this case

1740-506: Is the planar four-bar linkage . There are, however, many more special linkages: A compliant mechanism is a series of rigid bodies connected by compliant elements. These mechanisms have many advantages, including reduced part-count, reduced "slop" between joints (no parasitic motion because of gaps between parts ), energy storage, low maintenance (they don't require lubrication and there is low mechanical wear), and ease of manufacture. Flexure bearings (also known as flexure joints ) are

1798-492: Is used to mount a weapon beneath the barrel of a larger one, using either special mounting equipment or an accessory rail. This allows the user to have two weapons ready in hand and a simple change of grip is all that is needed to fire the accessory weapon. It is most commonly used to mount a single-shot grenade launcher to a rifle or a cut-down shotgun to breach doors. Various forms of weapon mounts have existed for individual use, or experimented with for military trials to ease

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1856-425: The involute tooth yielded a standard gear design that provides a constant speed ratio. Some important features of gears and gear trains are: The design of mechanisms to achieve a particular movement and force transmission is known as the kinematic synthesis of mechanisms . This is a set of geometric techniques which yield the dimensions of linkages, cam and follower mechanisms, and gears and gear trains to perform

1914-582: The Red Army, unable to keep up with the T-34 medium tank and unable to penetrate the armour of most German tanks, but they could be produced by small factories that were unable to handle the large components of medium and heavy tanks. The T-70 was an attempt to remedy some of the shortcomings of the T-60 scout tank, which had very poor cross-country mobility, thin armour, and an inadequate 20-mm gun. It also replaced

1972-570: The T-80 light tank was designed, a more robust version of the T-70 with a two-man turret . But there was enough lend-lease equipment available to fulfill the reconnaissance role of the light tanks, and armoured cars were better suited for light scouting and liaison. All light tank production was cancelled in October 1943, after only about 120 T-80s were built. No further light tanks would be built during

2030-526: The aircraft at the target. Some aircraft designs used different concept of fixed mounts, as found in Schräge Musik or AC-47 Spooky . The Stridsvagn 103 is an unusual turretless main battle tank with a fixed main gun that is aimed using the tank's tracks and suspension. Military aircraft also often used fixed mounts called hardpoints or weapon stations to attach disposable stores such as missiles, bombs and external fuel tanks: these devices mount

2088-412: The carriage can be completely dismantled and split into a series of loads for transport over rough terrain, typically by mules . Typically used by infantry mortars , this is a flat plate mounted to the weapon directly or using a ball joint . The plate is usually square, rectangular or circular, and designed to spread out the weapon's recoil force to prevent it from being piledriven into the ground: it

2146-432: The commanders were kept busy acquiring targets, loading and firing the main gun and machine gun, and commanding their drivers. The infantry tank role was already considered obsolete. The SU-76 self-propelled gun was better suited for infantry support, its 76.2-mm gun capable of firing a larger high explosive shell . Industrial resources could be redirected from light tanks to building SU-76s. In an attempt to compensate,

2204-409: The concentric spherical shells. The movement of these mechanisms is characterised by the group SO(3) of rotations in three-dimensional space. Other examples of spherical mechanisms are the automotive differential and the robotic wrist. The rotation group SO(3) is three-dimensional. An example of the three parameters that specify a spatial rotation are the roll, pitch and yaw angles used to define

2262-455: The conical turrets on early-production machines were replaced with new welded turrets. The end of the T-70's production run was built with two 85-hp GAZ-203 engines, a Mark 4 commander's periscope replacing a vision slit, and other improvements. The T-70 remained in service until 1948. The one-man turret of the Soviet light tanks made co-ordinating a tank platoon nearly impossible, because

2320-406: The crew or mechanism of a weapon and at the same time lets the weapon be aimed and fired in many directions. A turret is a rotating weapon platform, strictly one that crosses the armour of whatever it is mounted on with a structure called a barbette (on ships) or basket (on tanks) and has a protective structure on top (gunhouse). If it has no gunhouse it is a barbette, if it has no barbette (i.e., it

2378-446: The days of early arquebusiers , when they would typically be a long thin stake with a U-shaped rest at the top, referred to as a fork rest. On firearms , shooting sticks are commonly used on rifles to provide a forward rest and reduce motion. Shooting sticks permit the operator to rest the weapon on the ground, a low wall, or other object, reducing operator fatigue and permitting increased accuracy. This type of infantry weapon mount

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2436-507: The disadvantage of being heavy and bulky, but provide far superior stability and do not require the user to exert any force in order to keep the mount balanced. Tripods are typically used on support weapons such as heavy machine guns, repeating grenade launchers, recoilless rifles and large infantry anti-tank missiles systems such as BGM-71 TOW . These tripods are often much larger than the weapon itself and may have mechanical elevation and traverse controls for indirect fire. The tripod permits

2494-517: The first tanks were issued. It was quickly redesigned as the T-70M (although it continued to be referred to as just T-70 ), with the engines in-line on the right side of the tank and a normal transmission and differential. The conical turret was replaced by one more easily welded out of plate armour, and moved to the left side of the hull. Curiously, even after the T-70's production line was redesigned, SU-76 self-propelled guns started to be built with

2552-501: The handling of heavy weapons and reduce fatigue on the battlefield. An example is the affusto d'assalto ( assault carriage ) or "bari mount" that was devised by the 139° e 140° Reggimento Fanteria Brigata "Bari" in 1917 and used on the Villar Perosa aircraft submachine gun for walking fire tactics. This allowed the user not only to fire the spade grip weapon but also throw grenades at the same time during combat. The Bari mount

2610-414: The manner of a small cart or wheelbarrow , while larger ones require traction by animals or vehicles. Large weapons often use a deployable base to make them easier to transport and more stable in their firing position: split-trail mounts (where two long "trails" can be brought together to make a towing bar) and cruciform bases with two folding legs are examples. "Pack howitzers" are a special case where

2668-412: The movement of the mechanism. In general a cam and follower mechanism's energy is transferred from cam to follower. The camshaft is rotated and, according to the cam profile, the follower moves up and down. Nowadays, slightly different types of eccentric cam followers are also available, in which energy is transferred from the follower to the cam. The main benefit of this type of cam and follower mechanism

2726-460: The operator to rest the weapon on the ground and thus the gun feels lighter to the shooter and accuracy is increased. A shooting saddle typically uses a tripod head but, instead of mounting the weapon directly to the tripod, the saddle is mounted to the tripod head and the rifle is cradled within the saddle. These saddles began to appear in the late 2000s as a solution to provide a stable shooting platform for snipers and marksmen who may need to take

2784-464: The orientation of an aircraft. A mechanism in which a body moves through a general spatial movement is called a spatial mechanism . An example is the RSSR linkage, which can be viewed as a four-bar linkage in which the hinged joints of the coupler link are replaced by rod ends , also called spherical joints or ball joints . The rod ends let the input and output cranks of the RSSR linkage be misaligned to

2842-456: The origin of a coordinate frame in F , and the angle measured from the x -axis in F to the x -axis in M . This is often described saying a body in the plane has three degrees of freedom . The pure rotation of a hinge and the linear translation of a slider can be identified with subgroups of SE, and define the two joints as one degree-of-freedom joints of planar mechanisms. The cam joint formed by two surfaces in sliding and rotating contact

2900-413: The point that they lie in different planes, which causes the coupler link to move in a general spatial movement. Robot arms , Stewart platforms , and humanoid robotic systems are also examples of spatial mechanisms. Bennett's linkage is an example of a spatial overconstrained mechanism , which is constructed from four hinged joints. The group SE(3) is six-dimensional, which means the position of

2958-569: The same unsatisfactory unsynchronized two-engine layout, and all of them were later recalled for factory rebuilding as SU-76Ms. T-70s were put into production in March 1942 at Zavod No. 37 , and along with T-60 production at GAZ and Zavod No. 38 . They completely replaced T-60 production in September 1942, although that tank remained in use until the end of the war. Production ended in October 1943, with 8,226 vehicles completed. In April 1942,

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3016-437: The system is called a planar mechanism . The kinematic analysis of planar mechanisms uses the subset of Special Euclidean group SE , consisting of planar rotations and translations, denoted by SE. The group SE is three-dimensional, which means that every position of a body in the plane is defined by three parameters. The parameters are often the x and y coordinates of the origin of a coordinate frame in M , measured from

3074-466: The time of Archimedes to the Renaissance , mechanisms were viewed as constructed from simple machines , such as the lever , pulley , screw , wheel and axle , wedge , and inclined plane . Reuleaux focused on bodies, called links , and the connections between these bodies, called kinematic pairs , or joints. To use geometry to study the movement of a mechanism, its links are modelled as rigid bodies . This means that distances between points in

3132-530: The very short production run of the T-50 light infantry tank, which was more sophisticated, but also much more complicated and expensive to produce. The T-70 was designed by Nicholas Astrov 's design team at Factory No. 38 in Kirov . The first batch of T-70s were built with a GAZ-202 automotive engine on each side of the hull, one driving each track . This arrangement was seen to be a serious problem, even before

3190-492: The war. In November 1943 Red Army tank units were reorganized: light tanks were replaced by the T-34 and the new T-34-85 variant, which started production the following month. Light tanks continued to be used in self-propelled artillery and some other units. The Soviets did start development work on an amphibious light tank in 1945, resulting in the post-war PT-76 , introduced in 1954. Coaxial weapon A weapon mount

3248-431: The weapon or integral to it. Those of higher quality can be tilted and also have their tilting point close to the bore central axis, allowing the weapon to tilt left and right a small amount, allowing a quick horizontal sight picture on uneven ground and keeping the operator close to the ground. A tripod has three legs and provides stability along the left-to-right and fore-and-aft coordinate axis of motion. Tripods have

3306-401: The whole system in one stable position: typically the mounting is either a rod on the underside of the gun (a pintle rod) that mates with a socket mechanism , or an intermediary cradle that mounts to the sides of the weapon's barrel or receiver. Due to the stability offered by the mount, the gun typically does not need a shoulder stock , with many modern examples using two-handed spade grips. It

3364-759: Was used in trench raids, and was integral to the doctrinal purpose of the so-called 'pistollettieri' sections who were effectively grenadier-submachine gunners. Another example is the Third Arm Weapon Interface System and REAPER weapon support system. Mechanism (engineering) In engineering , a mechanism is a device that transforms input forces and movement into a desired set of output forces and movement. Mechanisms generally consist of moving components which may include Gears and gear trains ; Belts and chain drives ; cams and followers ; Linkages ; Friction devices, such as brakes or clutches ; Structural components such as

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