A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders each but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft. Since each cylinder bank is a straight-six, by itself in both primary and secondary balance, a V12 inherits perfect primary and secondary balance no matter which V angle is used, therefore it needs no balance shafts. A four-stroke 12 cylinder engine has an firing order if cylinders fire every 60° of crankshaft rotation, so a V12 with cylinder banks at a multiples of 60° will have firing intervals without using split crankpins. By using split crankpins or ignoring minor vibrations, any V angle is possible; the 180° configuration is referred to as a "flat-twelve engine" or a "boxer" although it is in reality a 180° V since the pistons can and do use shared crankpins. It may be written as "V-12", although this is less common; these engines deliver power pulses more than engines with six or eight cylinders, the power pulses have triple overlap which eliminates gaps between power pulses and allows for greater refinement and smoothness in a luxury car engine, at the expense of much greater cost and friction losses.
In a racing car engine, the rotating parts of a V12 can be made much lighter than a V8 of similar displacement with a crossplane crankshaft because there is no need to use heavy counterweights on the crankshaft and less need for the inertial mass in a flywheel to smooth out the power delivery, each piston can be smaller and with a shorter stroke. Exhaust system tuning is much more difficult on a crossplane V8 than a V12, so racing cars with V8 engines use a complicated "bundle of snakes" exhaust system, or a flat-plane crankshaft which causes severe engine vibration and noise; this is not important in a race car. Since cost and fuel economy are important in luxury and racing cars, the V12 has been phased out in favor of engines with fewer cylinders. Engines are designed around cylinder units of a certain designed size and speed; these are used as the working base of an engine of 6 cylinders. If more power is needed, it is easier to add more cylinders to increase displacement, without having to design a newer, larger cylinder and head for each engine size.
Thus locomotive and marine engines like the EMD 567 come in V6 to V24 versions, all sharing the same 567 cubic inch cylinder displacement and cylinder heads. Engines are limited by the size of the cylinder bore and stroke. While one can increase the size of an engine by increasing the bore and/or stroke of the cylinder, a too-large bore hurts efficient combustion, makes for a heavy reciprocating piston mass, which limits maximum engine speed and thus power output. In a similar vein, increasing the stroke means the piston speed must be increased to match the same revolutions per minute, this limits the maximum size of an engine in a given weight/size range; these factors make it more feasible to build an engine of 12 cylinders and 40 liters displacement than an engine of 6 cylinders and the same size, which would have pistons too large and a stroke too long to meet the same RPM and power requirements. In a large displacement, high-power engine, a 60° V12 fits into a longer and narrower space than a V8 and most other V configurations, a problem in modern cars, but less so in heavy trucks, a problem in large stationary engines.
The V12 is common in locomotive and tank engines, where high power is required, but the width of the engine is constrained by tight railway clearances or street widths, while the length of the vehicle is more flexible. It is used in marine engines where great power is required, the hull width is limited, but a longer vessel allows faster hull speed. In twin-propeller boats, two V12 engines can be narrow enough to sit side-by-side, while three V12 engines are sometimes used in high-speed three-propeller configurations. Large, fast cruise ships can have six or more V12 engines. In historic piston-engine fighter and bomber aircraft, the long, narrow V12 configuration used in high-performance aircraft made them more streamlined than other engines the short, wide radial engine. During World War II the power of fighter engines was stepped up to extreme levels using multi-speed superchargers and ultra-high octane gasoline, so the extreme smoothness of the V12 prevented the powerful engines from tearing apart the light airframes of fighters.
After World War II, the compact, more powerful, vibration-free turboprop and turbojet engines replaced the V12 in aircraft applications. The first V-type engine was built in 1889 to a design by Wilhelm Maybach. By 1903 V8 engines were being produced for motor boat racing by the Société Antoinette to designs by Léon Levavasseur, building on experience gained with in-line four-cylinder engines. In 1904, the Putney Motor Works completed a new V12 marine racing engine—the first V12 engine produced for any purpose. Known as the "Craig-Dörwald" engine after Putney's founding partners, the engine mounted pairs of L-head cylinders at a 90 degree included angle on an aluminium crankcase, using the same cylinder pairs that powered the company's standard two-cylinder car. A single camshaft mounted in the central V operated the valves directly; as in many marine engines, the camshaft could be slid longitudinally to engage a second set of cams, giving valve timing that reversed the engine's rotation to achieve astern propulsion.
The Nakajima Ki-44 Shōki was a single-engine fighter aircraft used by the Imperial Japanese Army Air Force in World War II. The type first flew in August 1940 and entered service in 1942; the Allied reporting name was "Tojo". It was less maneuverable than its predecessor, the nimble Ki-43, pilots disliked its poor visibility on the ground, its higher landing speed, severe restrictions on maneuvering. Nonetheless, as a combat aircraft the Ki-44 was superior overall to the Ki-43; as an interceptor it could match Allied types in climbs and dives, giving pilots more flexibility in combat and greater pilot confidence than the Ki-43. Moreover, the basic armament of four 12.7mm machine guns or two 12.7mm guns and two 20 mm cannons was far superior to the older Ki-43's two 12.7mm machine guns. These characteristics made the fighter, despite performance restrictions at altitude, a useful B-29 Superfortress interceptor and one of the Japanese High Command priorities during the last year of war. However, like most Japanese aircraft flown in the last part of the war, the low availability of properly trained pilots made them easy targets for experienced and well trained Allied pilots flying superior aircraft.
Nakajima began development of the Ki-44 in 1940 as a pure interceptor with emphasis being placed on airspeed and rate of climb rather than maneuverability. The Japanese Army Air Force specification called for a maximum speed of 600 km/h at 4,000 m, to be attained in five minutes. A set of Ki-43-like "butterfly" combat flaps was fitted for improved maneuverability. Armament consisted of a pair of 12.7 mm machine guns. The engine selected for the new interceptor was Nakajima's Ha-41 14-cylinder double-row radial intended for bomber aircraft. Although the Ha-41 was not the ideal choice due to its large-diameter cross section, the design team was able to marry this engine to a much smaller fuselage with a narrow cross section. At 1,260 mm in diameter, the Ha-41 was 126 mm larger in diameter than the 1,144 mm Nakajima Sakae. However, the Sakae was only 27.8L in displacement and 1,000 hp, while the Ha-41 was 37.5L and made 1,260 hp. In any case, since the Sakae wasn't powerful enough, the only alternative available was the Mitsubishi Kinsei, smaller than the Ha-41 in diameter, five liters smaller in displacement, was less powerful.
This was in demand for many other aircraft, so the Ha-41 was chosen as the best powerplant. In order to achieve its design goals, the wing area was small leading to a high wing loading and a comparatively high landing speed that could be daunting to the average Japanese pilot, more used to aircraft with a low wing loading like the Ki-44s predecessors, the Ki-43 and Ki-27; the first Ki-44 prototype flew in August 1940 and the initial test flights were encouraging, with handling considered acceptable considering the high wing loading. Problems encountered included a high landing speed and poor forward visibility during taxiing due to the large radial engine. A second pre-production batch of 40 aircraft were ordered, which featured four 12.7mm machine guns, a relocated air cooler and main gear doors. The Nakajima Ki-44 at one point equipped 12 sentai of the Imperial Japanese Army Air Force: 9, 22, 23, 29, 47, 59, 64, 70, 85, 87, 104 and 246 Sentai; the Manchukuo Air Force operated some Ki-44s. Pre-production Ki-44 aircraft and two of the prototypes were turned over to the Army for service trials on 15 September 1941.
The type commenced operations when nine aircraft were received by an experimental unit, 47th Chutai "Kawasemi Buntai", commanded by Major Toshio Sakagawa at Saigon, Indochina in December 1941. The Ki-44 saw significant action with 87th Sentai in the air defense role, while based at Palembang, Sumatra. Other units equipped with the Ki-44 during the early part of the war were stationed in China, The Philippines and Korea. In the war, the type saw action in an air defense role over the home islands – around Japan's large industrial cities. 47 Chutai, after it was transferred to air defense roles in Japan, was expanded to become 47 Sentai. The Ki-44-II Otsu could be armed with a Ho-301 40 mm autocannon. While this was a high-caliber weapon, it used caseless ammunition with a low muzzle velocity and short range, effective only in close attacks; some of these aircraft were used against USAAF bombers by a special Shinten Seiku Tai, comprising at least four aircraft, part of 47th Sentai, based at Narimasu airfield in Tokyo.
Pilots from such units attempted to shoot down B-29s and, once their ammunition was expended, to ram them – a suicide attack. While the concept appeared straightforward, ramming a B-29 at high altitudes was difficult to achieve in practice. By the end of the war, Ki-44 variants were being replaced by the Nakajima Ki-84 Hayate, regarded as vastly superior – in aspects other than maintenance and reliability. During 1946–49, both sides in the Chinese Revolution operated Ki-44s surrendered or abandoned by Japanese units. Air units of the People's Liberation Army obtained aircraft belonging to 22 and 85 Sentai, which had disbanded in Korea; some of these aircraft were flown by Japanese veterans. Within the Republic of China Air Force 18th Squadron was equippe
The Kawasaki KH-4 was a light utility helicopter produced in Japan in the 1960s as a development of the Bell 47 that Kawasaki had been building under licence since 1952. The most visible difference between the KH-4 and its forerunner was its enlarged cabin; this was enclosed and provided seating for three passengers side-by-side on a bench seat behind the pilot's seat. The helicopter was provided with a new control system, revised instrumentation, larger fuel tank. A total of 211 KH-4s were built, including four; the vast majority of these were bought by civil operators, although some were purchased by the military forces of Japan and Thailand. JapanJapan Ground Self-Defense Force - 14 Japan Maritime Self-Defense Force Maritime Safety Agency - six ThailandThai Air Force Data from Jane's All The World's Aircraft 1966–67General characteristics Crew: One pilot Capacity: 3 passengers Length: 9.93 m Main rotor diameter: 11.32 m Height: 2.84 m Main rotor area: 100.6 m2 Empty weight: 816 kg Gross weight: 1,293 kg Powerplant: 1 × Lycoming TVO-435-B1A horizontally opposed six cylinder, 200 kW Performance Maximum speed: 169 km/h Cruising speed: 140 km/h Range: 400 km Endurance: 4 hours 6 min Service ceiling: 5,640 m Rate of climb: 4.3 m/s Armament Related development Agusta A.115 Bell 47 Bell 47J Ranger Meridionali/Agusta EMA 124Aircraft of comparable role and era Canadian Home Rotors Safari Hiller OH-23 Raven Hughes TH-55 Osage Sikorsky S-300 Andrade, John.
Militair 1982. London: Aviation Press Limited. Taylor, John W. R.. Jane's All The World's Aircraft 1966–67. London: Sampson Low, Marston & Company. Taylor, Michael J. H.. Jane's Encyclopedia of Aviation. London: Studio Editions. P. 557. Simpson, R. W.. Airlife's Rotorcraft. Ramsbury: Airlife Publishing. Pp. 123–25
A Warren truss or equilateral truss is a type of engineering truss. It was patented in 1848 by Willoughby Theobald Monzani; the Warren truss consists of longitudinal members joined only by angled cross-members, forming alternately inverted equilateral triangle-shaped spaces along its length. This gives a pure truss: each individual strut, beam, or tie is only subject to tension or compression forces, there are no bending or torsional forces on them. Loads on the diagonals alternate between compression and tension, with no vertical elements, while elements near the centre must support both tension and compression in response to live loads; this configuration combines strength with economy of materials and can therefore be light. The girders being of equal length, it is ideal for use in prefabricated modular bridges, it is an improvement over the Neville truss. A variant of the Warren truss has additional vertical members within the triangles; these are used when the lengths of the upper horizontal members would otherwise become so long as to present a risk of buckling These verticals do not carry a large proportion of the truss loads.
The Warren truss is a prominent structural feature in hundreds of hastily constructed aircraft hangars in WW2. In the early parts of the war, the British and Canadian government formed an agreement known as the British Commonwealth Air Training Plan which used newly constructed airbases in Canada to train aircrew needed to sustain emerging air forces. Dozens and hundreds of airfields, aprons and ground installations were constructed all across Canada. Two characteristic features were, indeed many still remain in service, are a triangle runway layout and hangars built from virgin British Columbia timbers with Warren truss configuration roofs. Warren truss construction has been used in airframe design and construction, for substantial numbers of aircraft designs. An early use was for the interplane wing struts on some biplanes; the Italian World War I Ansaldo SVA series of fast reconnaissance biplanes were among the fastest aircraft of their era, while the Handley Page H. P.42 was a successful airliner of the late 1920s and the Fiat CR.42 Falco fighter remained in service until World War II.
The Warren truss is sometimes used for fuselage frames, such as in the Piper J-3 Cub
Internal combustion engine cooling
Internal combustion engine cooling uses either air or liquid to remove the waste heat from an internal combustion engine. For small or special purpose engines, cooling using air from the atmosphere makes for a lightweight and simple system. Watercraft can use water directly from the surrounding environment to cool their engines. For water-cooled engines on aircraft and surface vehicles, waste heat is transferred from a closed loop of water pumped through the engine to the surrounding atmosphere by a radiator. Water has a higher heat capacity than air, can thus move heat more away from the engine, but a radiator and pumping system add weight and cost. Higher-power engines generate more waste heat, but can move more weight, meaning they are water-cooled. Radial engines allow air to flow around each cylinder directly, giving them an advantage for air cooling over straight engines, flat engines, V engines. Rotary engines have a similar configuration, but the cylinders continually rotate, creating an air flow when the vehicle is stationary.
Aircraft design more favors lower weight and air-cooled designs. Rotary engines were popular on aircraft until the end of World War I, but had serious stability and efficiency problems. Radial engines were popular until the end of World War II, until gas turbine engines replaced them. Modern propeller-driven aircraft with internal-combustion engines are still air-cooled. Modern cars favor power over weight, have water-cooled engines. Modern motorcycles are lighter than cars, both cooling fluids are common; some sport motorcycles were cooled with both oil. Heat engines generate mechanical power by extracting energy from heat flows, much as a water wheel extracts mechanical power from a flow of mass falling through a distance. Engines are inefficient, so more. Internal combustion engines remove waste heat through cool intake air, hot exhaust gases, explicit engine cooling. Engines with higher efficiency less as waste heat; some waste heat is essential: it guides heat through the engine, much as a water wheel works only if there is some exit velocity in the waste water to carry it away and make room for more water.
Thus, all heat engines need cooling to operate. Cooling is needed because high temperatures damage engine materials and lubricants and becomes more important in hot climates. Internal-combustion engines burn fuel hotter than the melting temperature of engine materials, hot enough to set fire to lubricants. Engine cooling removes energy fast enough to keep temperatures low; some high-efficiency engines run without explicit cooling and with only incidental heat loss, a design called adiabatic. Such engines can achieve high efficiency but compromise power output, duty cycle, engine weight and emissions. Most internal combustion engines are fluid cooled using either air or a liquid coolant run through a heat exchanger cooled by air. Marine engines and some stationary engines have ready access to a large volume of water at a suitable temperature; the water may be used directly to cool the engine, but has sediment, which can clog coolant passages, or chemicals, such as salt, that can chemically damage the engine.
Thus, engine coolant may be run through a heat exchanger, cooled by the body of water. Most liquid-cooled engines use a mixture of water and chemicals such as antifreeze and rust inhibitors; the industry term for the antifreeze mixture is engine coolant. Some antifreezes use no water at all, instead using a liquid with different properties, such as propylene glycol or a combination of propylene glycol and ethylene glycol. Most "air-cooled" engines use some liquid oil cooling, to maintain acceptable temperatures for both critical engine parts and the oil itself. Most "liquid-cooled" engines use some air cooling, with the intake stroke of air cooling the combustion chamber. An exception is Wankel engines, where some parts of the combustion chamber are never cooled by intake, requiring extra effort for successful operation. There are many demands on a cooling system. One key requirement is to adequately serve the entire engine, as the whole engine fails if just one part overheats. Therefore, it is vital.
Liquid-cooled engines are able to vary the size of their passageways through the engine block so that coolant flow may be tailored to the needs of each area. Locations with either high peak temperatures or high heat flow may require generous cooling; this reduces the occurrence of hot spots. Air-cooled engines may vary their cooling capacity by using more spaced cooling fins in that area, but this can make their manufacture difficult and expensive. Only the fixed parts of the engine, such as the block and head, are cooled directly by the main coolant system. Moving parts such as the pistons, to a lesser extent the crank and rods, must rely on the lubrication oil as a coolant, or to a limited amount of conduction into the block and thence the main coolant. High performance engines have additional oil, beyond the amount needed for lubrication, sprayed upwards onto the bottom of the piston just for extra cooling. Air-cooled motorcycles rely on oil-cooling in addition to air-cooling of the cylinder barrels.
Liquid-cooled engines have a circulation pump. The first engines relied
Kawasaki Army Type 88 Reconnaissance Aircraft
The Kawasaki Army Type 88 Reconnaissance Aircraft was a Japanese single-engined biplane designed for Kawasaki by Richard Vogt. Known by its company designation KDA-2, it was accepted by the Imperial Japanese Army as the Type 88 Reconnaissance Aircraft; the Type 88 number was designated for the year the aircraft was accepted, 2588 in the Japanese imperial year calendar, or 1928 in the Gregorian calendar. The basic design was modified into the Type 88 Light Bomber that used in combat over China in the Second Sino-Japanese War; the Type 88 was built in large numbers and remained in service until 1940. The Army Type 88-1 Reconnaissance Biplane was designed by Richard Vogt as the Kawasaki KDA-2 to meet a Japanese Army requirement for a reconnaissance biplane to replace the Salmson 2. Three KDA-2 prototypes were built by Kawasaki Kōkūki Kōgyō K. K. in 1927. After flight testing, the aircraft was accepted and ordered into production as the Army Type 88-1 Reconnaissance Biplane; the aircraft was of all-metal construction, with a stressed skin forward fuselage, unequal-span wings and a slim angular fuselage, with cross-axle main landing gear. was powered by a 447 kW BMW VI engine.
The Type 88-II Was an improved version with a revised tail assembly. By the end of 1931, 710 had been built by both Kawasaki and Tachikawa, who had 187 of the total number. Between 1929 and 1932, a bomber version was built as the Type 88 Light Bomber, differing in having a strengthened lower wing and an additional pair of centre-section struts. Bomb racks were located under lower wings. A total of 407 were produced. A transport variant was developed as the KDC-2 with room for a pilot and four passengers in an enclosed cabin. Only two KDC-2s were built and one of was tested on floats. Both reconnaissance and bomber versions saw action with the Imperial Japanese Army Air Force during the Second Sino-Japanese War in Manchuria, a few were still in service in 1937 during fighting at Shanghai. KDA-2 Three prototypes in 1927. Type 88-I Reconnaissance Biplane. Production reconnaissance biplane. Type 88-II Reconnaissance Biplane Improved version of the 88-I, 707 built of both the 88-I and 88-II. Type 88 Light Bomber.
Light bomber able to carry 200 kg of bombs, 407 built. KDC-2 Transport variant, two built. JapanImperial Japanese Army Air Force ManchukuoManchukuo Imperial Air Force Data from Japanese Aircraft 1910-1941 The Illustrated Encyclopedia of Aircraft. Orbis Publishing. P. 2238. General characteristics Crew: 2 Length: 12.8 m Wingspan: 15.00 m Height: 3.40 m Wing area: 48 m2 Empty weight: 1,800 kg Gross weight: 2,850 kg Powerplant: 1 × BMW VI, 447 kW Performance Maximum speed: 221 km/h Endurance: 6 hours Service ceiling: 6,200 m Armament 2 × 7.7 mm machine guns The Illustrated Encyclopedia of Aircraft. Orbis Publishing. Pp. 2237–8. Mikesh, Robert C. Japanese Aircraft 1910-1941. London: Putnam. ISBN 0-85177-840-2. War Department TM-E-30-480 Handbook on Japanese Military Forces
In a fixed-wing aircraft, the spar is the main structural member of the wing, running spanwise at right angles to the fuselage. The spar carries the weight of the wings while on the ground. Other structural and forming members such as ribs may be attached to the spar or spars, with stressed skin construction sharing the loads where it is used. There may be more than one spar in a none at all. However, where a single spar carries the majority of the forces on it, it is known as the main spar. Spars are used in other aircraft aerofoil surfaces such as the tailplane and fin and serve a similar function, although the loads transmitted may be different from those of a wing spar; the wing spar provides the majority of the weight support and dynamic load integrity of cantilever monoplanes coupled with the strength of the wing'D' box itself. Together, these two structural components collectively provide the wing rigidity needed to enable the aircraft to fly safely. Biplanes employing flying wires have much of the flight loads transmitted through the wires and interplane struts enabling smaller section and thus lighter spars to be used at the cost of increasing drag.
Some of the forces acting on a wing spar are: Upward bending loads resulting from the wing lift force that supports the fuselage in flight. These forces are offset by carrying fuel in the wings or employing wing-tip-mounted fuel tanks. Downward bending loads while stationary on the ground due to the weight of the structure, fuel carried in the wings, wing-mounted engines if used. Drag loads dependent on airspeed and inertia. Rolling inertia loads. Chordwise twisting loads due to aerodynamic effects at high airspeeds associated with washout, the use of ailerons resulting in control reversal. Further twisting loads are induced by changes of thrust settings to underwing-mounted engines; the "D" box construction is beneficial to reduce wing twisting. Many of these loads are reversed abruptly in flight with an aircraft such as the Extra 300 when performing extreme aerobatic manoeuvers. Early aircraft used spars carved from solid spruce or ash. Several different wooden spar types have been used and experimented with such as spars that are box-section in form.
Wooden spars are still being used in light aircraft such as its relatives. A disadvantage of the wooden spar is the deteriorating effect that atmospheric conditions, both dry and wet, biological threats such as wood-boring insect infestation and fungal attack can have on the component. Wood wing spars of multipiece construction consist of upper and lower members, called spar caps, vertical sheet wood members, known as shear webs or more webs, that span the distance between the spar caps. In modern times, "homebuilt replica aircraft" such as the replica Spitfires use laminated wooden spars; these spars are laminated from spruce or douglas fir. A number of enthusiasts build "replica" Spitfires that will fly using a variety of engines relative to the size of the aircraft. A typical metal spar in a general aviation aircraft consists of a sheet aluminium spar web, with "L" or "T" -shaped spar caps being welded or riveted to the top and bottom of the sheet to prevent buckling under applied loads. Larger aircraft using this method of spar construction may have the spar caps sealed to provide integral fuel tanks.
Fatigue of metal wing spars has been an identified causal factor in aviation accidents in older aircraft as was the case with Chalk's Ocean Airways Flight 101. The German Junkers J. I armoured fuselage ground-attack sesquiplane of 1917 used a Hugo Junkers-designed multi-tube network of several tubular wing spars, placed just under the corrugated duralumin wing covering and with each tubular spar connected to the adjacent one with a space frame of triangulated duralumin strips — in the manner of a Warren truss layout — riveted onto the spars, resulting in a substantial increase in structural strength at a time when most other aircraft designs were built completely with wood-structure wings; the Junkers all-metal corrugated-covered wing / multiple tubular wing spar design format was emulated after World War I by American aviation designer William Stout for his 1920s-era Ford Trimotor airliner series, by Russian aerospace designer Andrei Tupolev for such aircraft as his Tupolev ANT-2 of 1922, upwards in size to the then-gigantic Maksim Gorki of 1934.
A design aspect of the Supermarine Spitfire wing that contributed to its success was an innovative spar boom design, made up of five square concentric tubes that fitted into each other. Two of these booms were linked together by an alloy web, creating a lightweight and strong main spar. A version of this spar construction method is used in the BD-5, designed and constructed by Jim Bede in the early 1970s; the spar used in the BD-5 and subsequent BD projects was aluminium tube of 2 inches in diameter, joined at the wing root with a much larger internal diameter aluminium tube to provide the wing structural integrity. In aircraft such as the Vickers Wellington, a geodesic wing spar structure was employed, which had the advantages of being lightweight and able to withstand heavy battle damage with only partial loss of strength. Many modern aircraft use carbon fibre and Kevlar in their construction, ranging in size from large airliners to small h