Aflat-twelve engine,also known as ahorizontally opposed-twelve,is a twelve-cylinderpiston enginewith six cylinders on each side of a centralcrankshaft.
Flat-twelve engines are less common thanV12 engines,but they have been used in various racing cars during the 1960s and 1970s, and in mid-engined Ferrari road cars from 1973 to 1996.
Design
editUnlike most flat-twin, flat-four, and flat-six engines, flat-twelve engines typically use the crankshaft configuration of a 180°V engine.Instead of theboxer enginedesign of each piston having its own crankpin, flat-twelve engines have each pair of pistons sharing acrankpin,and thus are flat, but not true boxers.
Compared with a V12 engine, a flat-twelve has a lowercenter of gravity,but because a flat-twelve is wider they are rarely used in front-engined cars.
Racing cars
editFormula One
editThe first known flat-twelve engine was built by Porsche in 1947 for the abandonedCisitalia Grand Prixracing car. The engine, known as the Porsche Typ 360, was supercharged and had a displacement of 1.5 L (92 cu in).[1]One engine was built and the car conducted top speed testing, but it never competed in any races.[2]
In 1964–65, theFerrari 512 F1competed in several Formula One races.[3]The 512 F1 was powered by a 1.5 L (92 cu in) flat-twelve engine and raced alongside the V8-engined Ferrari 158 upon which it was based. Ferrari returned to using flat-twelve engines in 1970, when theFerrari 312Bswitched from the V12 engine used by its predecessor. Its successor, theFerrari 312T,was introduced in 1975 and won the Formula One constructors championships from 1975 to 1979.[4][5]The success of the Ferrari 312T led other Formula One teams to build flat-twelve engines, such as the 1979Alfa Romeo 177.
In 1990, theSubaru 1235flat-twelve engine was built for Subaru's unsuccessful attempt to compete in Formula One as an engine manufacturer.
Sports car racing
edit
In 1969, thePorsche 917sports prototype racing car introduced an air-cooled flat-twelve engine. This flat-twelve engine was based on the previous flat-eight engine, but it used a V12 crankshaft configuration instead of theboxerconfiguration used by the flat-eight. The domination of the Porsche 917 probably influenced Ferrari, because they switched from V12 engines to flat-twelve engines (using a boxer configuration) for theFerrari 312 PB,which competed from 1971 to 1973. Alfa Romeo also used flat-twelve engines in the 1973-1976Alfa Romeo 33TT12andAlfa Romeo 33SC12sports prototype racing cars.
For the 1991 sports-prototype racing category, Mercedes-Benz switched from a twin-turbo V8 engine to a naturally-aspirated flat-twelve engine for in theMercedes-Benz C291racing car. This engine employed a cylinder-head design with exhaust ports where the intake ports would normally be (on top of the engine, pointing upwards). The intake ports are between the intake and exhaust camshafts, just above the spark-plugs, pointing at an outward angle from the vertical. This was done to allow the engine to be installed lower in the chassis. The C291 was unsuccessful and Mercedes withdrew from sports-prototype racing after the 1991 season.
Production cars
editFrom 1973 to 1996, Ferrari used flat-twelve engines in various production models: the 1973-1976Ferrari 365 GT/4 BB,the 1976-1981Ferrari 512 BB,the 1981-1984Ferrari 512 BBi,the 1984-1991Ferrari Testarossa,the 1991-1994Ferrari 512 TRand the 1994-1996Ferrari F512 M.
Other uses
editDuring World War II, the BritishCovenantertank was powered by aMeadowsD.A.V flat-12, 340 hp (250 kW) and theChurchillby a 350 hp (261 kW) Bedford engine flat 12.[6]Another military vehicle usage was thePanhard EBRarmored cars during the 1950s.[7]
During the 1940s, theFranklin Engine Companyin the United States produced a flat-twelve aircraft engine called the O-805-2.[8]
References
edit- ^"Cisitalia Grand Prix (Porsche type 360)".www.stuttcars.com.Retrieved6 October2019.
- ^"Cisitalia 360 Grand Prix Car"(PDF).stevemckelvie.files.wordpress.com.Archived fromthe original(PDF)on 27 February 2015.
- ^"1964 - 1965 Ferrari 1512 F1 - Images, Specifications and Information".www.ultimatecarpage.com.Retrieved5 October2019.
- ^"Niki Lauda".www.formula1.com.Retrieved5 October2019.
- ^"Jody Scheckter".www.formula1.com.Retrieved5 October2019.
- ^Fletcher, David(1983) [1944].Churchill Tank(Reprint of original WW2 operating manuals ed.).HMSO/The Tank Museum.pp. vii, 9(3), 29(19).ISBN978-0-11-290404-5.
- ^Ogorkiewicz, R.M.AFV Weapons Profile 039 Panhard Armoured Cars.Profile Publications.
- ^"Aircooled Motors (Franklin) O-805-2, Horizontally-Opposed 12 Engine".www.airandspace.si.edu.20 March 2016. Archived fromthe originalon 8 October 2019.Retrieved8 October2019.