An X engine is a

piston engine A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common feat ...

with four banks of cylinders around a common

crankshaft A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecti ...

, such that the cylinders form an "X" shape when viewed from front-on. The advantage of an X engine is that it is shorter than a

V engine A V engine, sometimes called a Vee engine, is a common configuration for internal combustion engines. It consists of two cylinder banks—usually with the same number of cylinders in each bank—connected to a common crankshaft. These cylinder ...

of the same number of cylinders, however the drawbacks are higher weight and complexity as compared to a

radial engine The radial engine is a reciprocating type internal combustion engine configuration in which the cylinders "radiate" outward from a central crankcase like the spokes of a wheel. It resembles a stylized star when viewed from the front, and is ...

. Therefore the configuration has been rarely used. Several of the X engine designs were based on combining two

Examples

Only two examples of X engines are known to have reached production. The first was the 1939–1942

Rolls-Royce Vulture The Rolls-Royce Vulture was a British aero engine developed shortly before World War II that was designed and built by Rolls-Royce Limited. The Vulture used the unusual " X-24" configuration, whereby four cylinder blocks derived from the R ...

, a X-24 aircraft engine which was built using two Rolls-Royce Peregrine V12 engines. The Rolls-Royce Vulture was briefly used in the

Avro Manchester The Avro 679 Manchester was a British twin-engine heavy bomber developed and manufactured by the Avro aircraft company in the United Kingdom. While not being built in great numbers, it was the forerunner of the famed and vastly more successful ...

heavy bomber, before engine failures caused it to be replaced by the Avro Lancaster (powered by the Rolls-Royce Merlin V12 engine). The other production X engine is the ChTZ Uraltrac 12N360 X-12 engine, first produced in 2015, and used in the Russian Armata tank platform. Several prototype 24-cylinder X engines for military aircraft were developed during World War II, including the Daimler-Benz DB 604, Rolls-Royce Exe and Isotta Fraschini Zeta R.C. 24/60, along with the 16-cylinder

Napier Cub The Napier Cub was an unusual and very large experimental 16-cylinder 'X' pattern liquid-cooled aero engine built by the British engine company D. Napier & Son. The Cub was the only Napier 'X' engine design. First flown on 15 December 1922 ...

. Other prototype X engines include a 1920s Ford X-8 automotive engine, which was investigated during the development process of the Ford Flathead V8 engine. During the 1960s, Honda is said to have experimented with an X-32 engine configuration for their Formula One racing efforts, but abandoned the design as being too complex and unreliable. From 2006 to 2010, the ''Revetec X4v1'' and ''Revetec x4v2'' X-4 experimental petrol engines were developed by an engine research company, followed in 2013 by the ''Revetec X4-D1'' experimental petrol engine.

References

{{Piston engine configurations Piston engine configurations Engines by cylinder layout

Examples

See also

References