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47-587: 750 cc OHV light alloy Straight-4 The Reliant TW9 (i.e., Three-Wheeler 9), also known as the Reliant Ant , is a small, front-engined, rear-drive, three-wheeled truck that was produced from 1967 to 1987 by Reliant Motors in Tamworth and then by BTB Engineering in Leeds , England. Designed and built as a business utility vehicle, it was produced in a number of different versions for various needs. After

94-456: A DOHC configuration gradually increased after World War II, beginning with sports cars. Iconic DOHC engines of this period include the 1948–1959 Lagonda straight-six engine , the 1949–1992 Jaguar XK straight-six engine and the 1954–1994 Alfa Romeo Twin Cam inline-four engine. The 1966-2000 Fiat Twin Cam inline-four engine was one of the first DOHC engines to use a toothed timing belt instead of

141-464: A DOHC engine was built in 1910. Use of DOHC engines slowly increased from the 1940s, leading to many automobiles by the early 2000s using DOHC engines. In an OHC engine, the camshaft is located at the top of the engine, above the combustion chamber . This contrasts the earlier overhead valve engine (OHV) and flathead engine configurations, where the camshaft is located down in the engine block . The valves in both OHC and OHV engines are located above

188-431: A camshaft as with typical OHV engines. The exhaust valve(s) were driven by a camshaft, but were located in the engine block as with side-valve engines. The 1894 prototype Diesel engine used overhead poppet valves actuated by a camshaft , pushrods and rocker arms , therefore becoming the first OHV engines. In 1896, U.S. patent 563,140 was taken out by William F. Davis for an OHV engine with liquid coolant used to cool

235-608: A fully enclosed-drivetrain), the American Liberty L-12 V12 engine, which closely followed the later Mercedes D.IIIa design's partly-exposed SOHC valvetrain design; and the Max Friz -designed; German BMW IIIa straight-six engine. The DOHC Napier Lion W12 engine was built in Great Britain beginning in 1918. Most of these engines used a shaft to transfer drive from the crankshaft up to the camshaft at

282-449: A large cylinder head to accommodate the camshaft or an extra set of valves to increase the volumetric efficiency , so that with the same displacement as an OHV engine, the OHC engine will end up being the physically larger of the two mostly due to the enlarged cylinder head. The other main advantage of OHC engines is that there is greater flexibility to optimise the size, location and shape of

329-487: A large margin. In the early 21st century, several pushrod V8 engines from General Motors and Chrysler used cylinder deactivation to reduce fuel consumption and exhaust emissions. In 2008, the first production pushrod engine to use variable valve timing was introduced in the Dodge Viper (fourth generation) . OHV engines have several advantages compared with OHC engines: Compared with OHC engines, OHV engines have

376-646: A long production run as the Reliant TW9, the vehicle was renamed the "Ant" by BTB engineering who continued to build it under license until 1986. Orders were usually plentiful for the little truck as the Ant was much favoured by municipal councils in the UK and Ireland. "Ant" was the most popular nickname for the TW9 and the truck was eventually marketed under that name. It used a pressed steel chassis designed by Press Mouldings and

423-403: A single windscreen wiper. "Despite its apparent simplicity the cabin design incorporated gentle curves and creases to enhance structural strength. The rear wheels drove the vehicle to a maximum speed of 54 mph (86 km/h)" and delivered fuel consumption of "around 28 mpg". The Ant was not known for being a particularly comfortable vehicle. Commercial Motor magazine noted in a 1967 road test that

470-407: A total of two camshafts (one for each cylinder bank). Most SOHC engines have two valves per cylinder, one intake valve and one exhaust valve. Motion of the camshaft is usually transferred to the valves either directly (using a tappet) or indirectly via a rocker arm . A dual overhead cam , double overhead cam , or twin-cam engine has two camshafts over each bank of the cylinder head, one for

517-531: Is possible. The first known automotive application of timing belts to drive overhead camshafts was the 1953 Devin-Panhard racing specials built for the SCCA H-modified racing series in the United States. These engines were based on Panhard OHV flat-twin engines, which were converted to SOHC engines using components from Norton motorcycle engines. The first production car to use a timing belt

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564-457: Is that the system used to drive the camshaft (usually a timing chain in modern engines) is more complex in an OHC engine, such as the 4-chain valvetrain of the Audi 3.2 or the 2 meter chain on Ford cammers. Another disadvantage of OHC engines is that during engine repairs where the removal of the cylinder head is required, the camshaft engine timing needs to be reset. In addition, an OHC engine has

611-399: The 1994 Indianapolis 500 motor race, Team Penske entered a car powered by the custom-built Mercedes-Benz 500I pushrod engine. Due to a loophole in the rules, the pushrod engine was allowed to use a larger displacement and higher boost pressure, significantly increasing its power output compared to the OHC engines used by other teams. Team Penske qualified in pole position and won the race by

658-551: The Duesenberg Model J , which was powered by a DOHC straight-eight engine. The 1931–1935 Stutz DV32 was another early American luxury car to use a DOHC engine. Also in the United States, the DOHC Offenhauser racing engine was introduced in 1933. This inline-four engine dominated North American open-wheel racing from 1934 until the 1970s. Other early SOHC automotive engines were the 1920–1923 Wolseley Ten ,

705-537: The 1903 Marr Auto Car SOHC engine built in the United States. The first DOHC engine was a Peugeot inline-four racing engine which powered the car that won the 1912 French Grand Prix . Another Peugeot with a DOHC engine won the 1913 French Grand Prix , followed by the Mercedes-Benz 18/100 GP with an SOHC engine winning the 1914 French Grand Prix . The Isotta Fraschini Tipo KM — built in Italy from 1910–1914—

752-427: The 1925-1948 Velocette K series , the 1931-1957 Norton International and the 1947-1962 Norton Manx . In more recent times, the 1950-1974 Ducati Single , 1973-1980 Ducati L-twin engine , 1999-2007 Kawasaki W650 and 2011-2016 Kawasaki W800 motorcycle engines have used bevel shafts. The Crosley four cylinder was the last automotive engine to use the shaft tower design to drive the camshaft, from 1946 to 1952;

799-417: The 1928-1931 MG 18/80 , the 1926–1935 Singer Junior and the 1928–1929 Alfa Romeo 6C Sport . Early overhead camshaft motorcycles included the 1925–1949 Velocette K Series and the 1927–1939 Norton CS1 . The 1946–1948 Crosley CC Four was arguably the first American mass-produced car to use an SOHC engine. This small mass-production engine powered the winner of the 1950 12 Hours of Sebring . Use of

846-506: The 701cc unit in 1972 and the price of a cab-and-chassis rose to £582 the same year. Early versions of the Ant used Reliant's 701cc engine, which had "a claimed 27.5 bhp (20 kW) of power" but the 1972 engine capacity increase to 748cc brought power up to 32 bhp (23.5 kW). Performance benefitted and it is possible that newer 848cc Reliant engines may have been retro-fitted in some vehicles. Another source indicates that after 1975 Reliant itself fitted its 848cc, 45 bhp engine, giving

893-517: The U.S. until the mid-to-late 1950s, when they began to be phased out for OHV engines. The first overhead camshaft (OHC) engine dates back to 1902, in the Marr ; however, use of this design was mostly limited to high-performance cars for many decades. OHC engines slowly became more common from the 1950s to the 1990s, and by the start of the 21st century, the majority of automotive engines (except for some North American V8 engines) used an OHC design. At

940-732: The UK, councils in England, Wales and Scotland bought large numbers of Ants as roadsweeps in the 1970s and 1980s, along with other versions of the truck. The Dublin Corp. in Ireland purchased 60 Ants for various municipal duties. Some 1888 Ants were built in the UK: 1229 between 1967 and 1971, and another 659 from 1972 (when the larger engine was fitted) to 1987, the year domestic production ceased. An unstated number of additional Ants were built in Greece after

987-519: The block, and were known as "tower shafts". An early American overhead camshaft production engine was the SOHC straight-eight engine used in the 1921–1926 Duesenberg Model A luxury car. In 1926, the Sunbeam 3 litre Super Sports became the first production car to use a DOHC engine. In the United States, Duesenberg added DOHC engines (alongside their existing SOHC engines) with the 1928 release of

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1034-576: The cab, the "sensibly placed" switches and gear-change lever, and found the Ant to be "very manoeuvrable" and simple to park. The first 200 trucks were left-hand drive and built for "the Greek market". By 1972, Reliant's partner in Greece, MEBEA , was building the vehicle under license. The overseas Ant offered a load capacity of 500 kg (1100 lbs) and was intended to compete in Mediterranean countries with vehicles such as Piaggio Ape . For

1081-415: The camshaft. Timing belts are inexpensive, produce minimal noise and have no need for lubrication. A disadvantage of timing belts is the need for regular replacement of the belt; recommended belt life typically varies between approximately 50,000–100,000 km (31,000–62,000 mi). If the timing belt is not replaced in time and fails and the engine is an interference engine , major engine damage

1128-470: The combustion chamber; however an OHV engine requires pushrods and rocker arms to transfer the motion from the camshaft up to the valves, whereas an OHC engine has the valves directly actuated by the camshaft. Compared with OHV engines with the same number of valves, there are fewer reciprocating components and less valvetrain inertia in an OHC engine. This reduced inertia in OHC engines results in less valve float at higher engine speeds (RPM). A downside

1175-466: The crankshaft and the camshaft is commonly used in diesel overhead camshaft engines used in heavy trucks. Gear trains are not commonly used in engines for light trucks or automobiles. Several OHC engines up until the 1950s used a shaft with bevel gears to drive the camshaft. Examples include the 1908–1911 Maudslay 25/30 , the Bentley 3 Litre , the 1917-? Liberty L-12 , the 1929-1932 MG Midget ,

1222-445: The cylinder head, but no working model was built. In 1898, bicycle manufacturer Walter Lorenzo Marr in the United States built a motorised tricycle powered by a single-cylinder OHV engine. Marr was hired by Buick (then named Buick Auto-Vim and Power Company ) from 1899–1902, where the overhead valve engine design was further refined. This engine employed pushrod-actuated rocker arms, which in turn opened poppet valves parallel to

1269-569: The following disadvantages: Overhead camshaft An overhead camshaft ( OHC ) engine is a piston engine in which the camshaft is located in the cylinder head above the combustion chamber . This contrasts with earlier overhead valve engines (OHV), where the camshaft is located below the combustion chamber in the engine block . Single overhead camshaft (SOHC) engines have one camshaft per bank of cylinders . Dual overhead camshaft (DOHC, also known as "twin-cam" ) engines have two camshafts per bank. The first production car to use

1316-432: The intake and exhaust ports, since there are no pushrods that need to be avoided. This improves the gas flow through the engine, increasing power output and fuel efficiency . The oldest configuration of overhead camshaft engine is the single overhead camshaft (SOHC) design. A SOHC engine has one camshaft per bank of cylinders, therefore a straight engine has a total of one camshaft and a V engine or flat engine has

1363-715: The intake valves and another for the exhaust valves. Therefore there are two camshafts for a straight engine and a total of four camshafts for a V engine or a flat engine. A V engine or flat engine requires four camshafts to function as a DOHC engine, since having two camshafts in total would result in only a single camshaft per cylinder bank for these engine layouts. Some V engines with four camshafts have been marketed as "quad-cam" engines, however technically "quad-cam" would require four camshafts per cylinder bank (i.e. eight camshafts in total), therefore these engines are merely dual overhead camshaft engines. Many DOHC engines have four valves per cylinder. The camshaft usually operates

1410-535: The pistons. Marr returned to Buick in 1904 (having built a small quantity of the Marr Auto-Car , with one of the first known engines to use an overhead camshaft design), the same year that Buick received a patent for an overhead valve engine design. In 1904, the world's first production OHV engine was released in the Buick Model B . The engine was a flat-twin design with two valves per cylinder. The engine

1457-502: The right-hand drive domestic market, a payload of 800 kg (1760 lbs) was envisaged, but with only 700cc's on tap, the Ant struggled to handle such a large load even with a very low rear axle ratio of 6.5:1. Nonetheless, Commercial Motor 's test of an Ant pickup, fully laded with 800 kg of sandbags, found that on a 15-mile motorway round trip the truck averaged 48.5 mph but was capable of 68 mph downhill and 57 mph on flat stretches of road. The magazine asserted that

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1504-454: The rights to the Crosley engine format were bought by a few different companies, including General Tire in 1952, followed by Fageol in 1955, Crofton in 1959, Homelite in 1961, and Fisher Pierce in 1966, after Crosley closed the automotive factory doors, and they continued to produce the same engine for several more years. A camshaft drive using three sets of cranks and rods in parallel

1551-419: The seats took "the form of fixed cushions with the backrests attached to the back of the cab, offering no adjustment whatever". The magazine said that bucket seats, "with a certain amount of adjustment for drivers of varying heights, could be fitted" and that "modifications could be made" to the cab to make the interior more spacious. On the other hand, Commercial Motor complimented the low levels of noise inside

1598-431: The speeds "did not prove a hindrance to other road-users" but pointed out that "the engine laboured quite a bit" on "even slight inclines". However, Commercial Motor did not see this as a significant problem as "it must be remembered that the model was not intended for long-distance work, but for local deliveries". "The price for a chassis and cabin was quoted as £451" upon its introduction in 1967. A 748cc engine replaced

1645-675: The starting point for both Mercedes' and Rolls-Royce's aircraft engines. Mercedes created a series of six-cylinder engines which culminated in the Mercedes D.III . Rolls-Royce reversed-engineered the Mercedes cylinder head design based on a racing car left in England at the beginning of the war, leading to the Rolls-Royce Eagle V12 engine. Other SOHC designs included the Spanish Hispano-Suiza 8 V8 engine (with

1692-447: The timing between each camshaft and the crankshaft. This affords better fuel economy by allowing a broader torque curve. Although each major manufacturer has their own trade name for their specific system of variable cam phasing systems, overall they are all classified as variable valve timing . The rotation of a camshaft is driven by a crankshaft . Many 21st century engines use a toothed timing belt made from rubber and kevlar to drive

1739-437: The top of the engine. Large aircraft engines— particularly air-cooled engines— experienced considerable thermal expansion, causing the height of the cylinder block to vary during operating conditions. This expansion caused difficulties for pushrod engines, so an overhead camshaft engine using a shaft drive with sliding spline was the easiest way to allow for this expansion. These bevel shafts were usually in an external tube outside

1786-607: The truck the ability to attain 50 mph and get a claimed 60 mpg. The Ant had a long production run because, at the time, no other vehicle offered as much variety in terms of vehicle configuration for so many jobs. "Target customers in the UK were mostly local government agencies". The Ant was often sold as just a cab-and-chassis, allowing customers to fit whatever body they wanted, such as flat-beds, closed delivery vans, small water tankers, refuse collectors, street drain cleaners, snow ploughs, road sweepers and articulated tractor units. Although originally intended to be sold only outside

1833-543: The valves at the top of the engine. However, some designs have the camshaft in the cylinder head but still sit below or alongside the valves (the Ford CVH and Opel CIH are good examples), so they can essentially be considered overhead valve designs. Some early intake-over-exhaust engines used a hybrid design combining elements of both side-valves and overhead valves. The first internal combustion engines were based on steam engines and therefore used slide valves . This

1880-414: The valves directly via a bucket tappet . A DOHC design permits a wider angle between intake and exhaust valves than in SOHC engines, which improves the air-fuel mixture's flow through the engine. A further benefit is that the spark plug can be placed at the optimum location, which in turn improves combustion efficiency . Another newer benefit of DOHC engine design is the ability to independently change/phase

1927-425: The vehicle went out of production in the UK. Overhead valve Although an overhead camshaft (OHC) engine also has overhead valves, the common usage of the term "overhead valve engine" is limited to engines where the camshaft is located in the engine block. In these traditional OHV engines, the motion of the camshaft is transferred using pushrods (hence the term "pushrod engine") and rocker arms to operate

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1974-520: Was one of the first production cars to use an SOHC engine. During World War I, both the Allied and Central Powers ; specifically those of the German Empire 's Luftstreitkräfte air forces, sought to quickly apply the overhead camshaft technology of motor racing engines to military aircraft engines. The SOHC engine from the Mercedes 18/100 GP car (which won the 1914 French Grand Prix) became

2021-420: Was styled by Ogle Design with a 701cc inline four-cylinder, four-stroke engine at the front, directly behind the single front wheel. It developed 27.5 bhp (20 kW) of power. The four-speed transmission had synchromesh only on the top three gears and the vehicle's unladen weight was 1200 lbs (545 kg). The glass-fibre cabin had space for two and the aerodynamic front had two round headlights and

2068-472: Was the 1962 Glas 1004 compact coupe. Another camshaft drive method commonly used on modern engines is a timing chain , constructed from one or two rows of metal roller chains . By the early 1960s most production automobile overhead camshaft designs used chains to drive the camshaft(s). Timing chains do not usually require replacement at regular intervals, however the disadvantage is that they are noisier than timing belts. A gear train system between

2115-410: Was the case for the first Otto engine , which was first successfully run in 1876. As internal combustion engines began to develop separately to steam engines, poppet valves became increasingly common. Beginning with the 1885 Daimler Reitwagen , several cars and motorcycles used inlet valve(s) located in the cylinder head, however these valves were vacuum-actuated ("atmospheric") rather than driven by

2162-474: Was used in the 1920–1923 Leyland Eight luxury car built in the United Kingdom. A similar system was used in the 1926-1930 Bentley Speed Six and the 1930-1932 Bentley 8 Litre . A two-rod system with counterweights at both ends was used by many models of the 1958-1973 NSU Prinz . Among the first overhead camshaft engines were the 1902 Maudslay SOHC engine built in the United Kingdom and

2209-471: Was very successful for Buick, with the company selling 750 such cars in 1905, and the OHV engine has powered almost all Buick automobiles since then. Several other manufacturers began to produce OHV engines, such as the 1906–1912 Wright Brothers Vertical 4-Cylinder Engine . In 1911, Chevrolet joined Buick in almost exclusive use of OHV engines. However, flathead "side-valve" engines remained commonplace in

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