![Simpson's Balanced 2-Stroke of 1914 high-res animation](https://upload.wikimedia.org/wikipedia/commons/3/30/Simpson%27s_Balanced_2-Stroke_of_1914_high-res_animation.gif)
An opposed-piston engine is a
piston engine in which each
cylinder
A cylinder (from ) has traditionally been a three-dimensional solid, one of the most basic of curvilinear geometric shapes. In elementary geometry, it is considered a prism with a circle as its base.
A cylinder may also be defined as an infin ...
has a
piston at both ends, and no
cylinder head
In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber.
In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ...
. Petrol and diesel opposed-piston engines have been used mostly in large-scale applications such as ships, military tanks, and factories. Current manufacturers of opposed-piston engines include
Fairbanks-Morse
Fairbanks, Morse and Company was an American manufacturing company in the late 19th and early 20th century. Originally a weighing scale manufacturer, it later diversified into pumps, engines, windmills, coffee grinders, radios, farm tractors, fee ...
,
Cummins
Cummins Inc. is an American multinational corporation that designs, manufactures, and distributes engines, filtration, and power generation products. Cummins also services engines and related equipment, including fuel systems, controls, air ...
and
Achates Power
Achates Power is an American developer of opposed-piston, two-stroke, compression ignition engines for use in commercial and passenger vehicles. Based in San Diego, California, the company was founded in 2004 by James U Lemke.
According to Achat ...
.
Design
![opposite piston engine](https://upload.wikimedia.org/wikipedia/commons/8/8f/Opposite_piston_engine.gif)
Compared to contemporary two-stroke engines, which used a conventional design of one piston per cylinder, the advantages of the opposed-piston engine have been recognized as:
* Eliminating the
cylinder head
In an internal combustion engine, the cylinder head (often abbreviated to simply "head") sits above the cylinders and forms the roof of the combustion chamber.
In sidevalve engines, the head is a simple sheet of metal; whereas in more modern ...
and valvetrain, which reduces weight, complexity, cost, heat loss, and friction loss of the engine.
* Creating a
uniflow-scavenged movement of gas through the combustion chamber, which avoided the drawbacks associated with the contemporary
crossflow-scavenged designs (however later advancements have provided methods for achieving uniflow scavenging in conventional piston engine designs).
* A reduced height of the engine
The main drawback was that the power from the two opposing pistons have to be geared together. This added weight and complexity when compared to conventional piston engines, which use a single
crankshaft as the power output.
The most common layout was two crankshafts, with the crankshafts geared together (in either the same direction or opposing directions). The Koreyvo, Jumo, and
Napier Deltic
The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were disp ...
engines used one piston per cylinder to expose an intake port, and the other to expose an exhaust port. Each piston is referred to as either an intake piston or an exhaust piston, depending on its function in this regard. This layout gives superior scavenging, as gas flow through the cylinder is axial rather than radial, and simplifies design of the piston crowns. In the Jumo 205 and its variants, the upper crankshaft serves the exhaust pistons, and the lower crankshaft the intake pistons. In designs using multiple cylinder banks, each big end bearing serves one inlet and one exhaust piston, using a forked connecting rod for the exhaust piston.
History
1880s to 1930s
![Jumo205 cutview 02](https://upload.wikimedia.org/wikipedia/commons/0/05/Jumo205_cutview_02.jpg)
One of the first opposed-piston engines was the 1882
Atkinson differential engine, which has a power stroke on every rotation of the crankshaft (compared with every second rotation for the contemporary
Otto cycle
An Otto cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. It is the thermodynamic cycle most commonly found in automobile engines.
The Otto cycle is a description of what hap ...
engine), but it was not a commercial success.
In 1898, an Oechelhäuser two-stroke opposed-piston engine producing was installed at the Hoerde ironworks. This design of engine was also produced under licence by manufacturers including Deutsche Kraftgas Gesellschaft in Germany and
William Beardmore & Sons in the United Kingdom.
In 1901, the Kansas City Lightning Balanced Gas and Gasoline Engines were gasoline engines producing .
An early opposed-piston car engine was produced by the French company
Gobron-Brillié
Gobron-Brillié was an early French automobile manufactured from 1898 to 1930.P. Roberts (1973). ''A Picture History of the Automobile'', Ward Lock Ltd, London, UK. The original company, ''Societé des Moteurs Gobron-Brillié'', was founded by t ...
around 1900. In April 1904, a Gobron-Brillié car powered by the opposed-piston engine was the first car ever to exceed 150 km/h with a "World's Record Speed" of . On 17 July 1904, the Gobron-Brillié car became the first to exceed for the flying kilometre.
The engine used a single crankshaft at one end of the cylinders and a crosshead for the opposing piston.
Another early opposed piston car engine was in the Scottish
Arrol-Johnston
Arrol-Johnston (later known as Arrol-Aster) was an early Scottish manufacturer of automobiles, which operated from 1895 to 1931 and produced the first automobile manufactured in Britain. The company also developed the world's first "off-road" v ...
car, which appears to have been first installed in their 10 hp buckboard c1900. The engine was described and illustrated in some detail in the account of their 12-15 hp car exhibited at the 1905 Olympia Motor-Show. The engine was a 4-stroke with two cylinders (with opposed pistons in each) with the crankshaft underneath and the pistons connected by lever arms to the two-throw crankshaft.
The first diesel engine with opposed pistons was a prototype built at
Kolomna Locomotive Works
The Kolomna Locomotive Works (Kolomensky Zavod) is a major producer of railroad locomotives as well as locomotive and marine diesel engines in Russia. The plant started production in 1869 with a freight steam locomotive, one of the first in Russia ...
in Russia. The designer, Raymond A. Koreyvo, patented the engine in France on 6 November 1907 and displayed the engine at international exhibitions, but it did not reach production. The Kolomna design used a typical layout of two crankshafts connected by gearing.
In 1914, the Simpson's Balanced Two-Stroke motorcycle engine was another opposed-piston engine using a single crankshaft beneath the centre of the cylinders with both pistons connected by levers. This engine was a crankcase compression design, with one piston used to uncover the transfer port, and the other to open the exhaust port. The advantage of this design was to avoid the
deflector crowns for pistons used by most two-stroke engines at that time.
Doxford Engine Works in the United Kingdom built large opposed-piston engines for marine use, with the first Doxford engine being installed in a ship in 1921. This diesel engine used a single crankshaft at one end of the cylinders and a crosshead for the opposing piston.
After World War I, these engines were produced in a number of models, such as the P and J series, with outputs as high as . Production of Doxford engines in the UK ceased in 1980.
Later opposed-piston diesel engines include the 1932
Junkers Jumo 205
The Jumo 205 aircraft engine was the most famous of a series of aircraft diesel engines produced by Junkers. The Jumo 204 first entered service in 1932. Later engines of this type comprised the experimental Jumo 206 and Jumo 208, with the Jumo 2 ...
aircraft engine built in Germany, which had two crankshafts, not using a design similar to the 1900–1922 Gobron-Brillié engines.
File:OechelhäuserEngine.jpg, 1898 Oechelhäuser gas engine
File:Gobron engine (Autocar Handbook, Ninth edition).jpg, 1900 Gobron-Brillié
Gobron-Brillié was an early French automobile manufactured from 1898 to 1930.P. Roberts (1973). ''A Picture History of the Automobile'', Ward Lock Ltd, London, UK. The original company, ''Societé des Moteurs Gobron-Brillié'', was founded by t ...
opposed-piston engine with overhung yoke
File:Opposed piston engine 1.jpg, Fairbanks Morse 38 8-1/8 diesel engine
The Fairbanks-Morse 38 8-1/8 is a diesel engine of the two-stroke, opposed-piston type. It was developed in the 1930s, and is similar in arrangement to a contemporary series of German Bombers aircraft diesels. The engine was used extensively in US ...
on the submarine
File:The Tank Museum (2383).jpg, Leyland L60 as used in the Chieftain tank
The FV4201 Chieftain was the main battle tank of the United Kingdom during the 1960s–1990s.
A development of the Centurion, the Chieftain introduced the supine (reclining) driver position to British design allowing a heavily sloped hull with r ...
1940s to present
The
Fairbanks Morse 38 8-1/8 diesel engine
The Fairbanks-Morse 38 8-1/8 is a diesel engine of the two-stroke, opposed-piston type. It was developed in the 1930s, and is similar in arrangement to a contemporary series of German Bombers aircraft diesels. The engine was used extensively in US ...
, originally designed in Germany in the 1930s, was used in U.S. submarines in the 1940s and 1950s, and in boats from the 1930s-present. It was also used in locomotives from 1944.
The latest (November 2021) version of the Fairbanks-Morse 38 8-1/8 is known as the FM 38D 8-1/8 Diesel and Dual Fuel. This two-stroke opposed-piston engine retains the same extra-heavy-duty design and has a rated in-service lifespan of more than 40 years, but now the optional capability of burning dual fuels (gaseous and liquid fuels, with automatic switchover to full diesel if the gas supply runs out) is available.
The
Commer TS3 three-cylinder diesel truck engines, released in 1954, have a single crankshaft beneath the centre of the cylinders with both pistons connected by levers.
Also released in 1954 was the
Napier Deltic
The Napier Deltic engine is a British opposed-piston valveless, supercharged uniflow scavenged, two-stroke diesel engine used in marine and locomotive applications, designed and produced by D. Napier & Son. Unusually, the cylinders were disp ...
engine for military boats. It uses three crankshafts, one at each corner, to form the three banks of double-ended cylinders arranged in an equilateral triangle. The Deltic engine was used in
British Rail Class 55
The British Rail Class 55, also known as a Deltic, or English Electric type 5, is a class of diesel locomotive built in 1961 and 1962 by English Electric for British Railways. They were designed for the high-speed express passenger services on t ...
and
British Rail Class 23
The British Rail Class 23 were a class of ten Bo-Bo diesel-electric locomotives built by the English Electric Company (EE) in 1959. The power unit used was a Napier Deltic T9-29 9-cylinder engine of driving an EE generator, which powered the f ...
locomotives and to power fast patrol boats and
Royal Navy
The Royal Navy (RN) is the United Kingdom's naval warfare force. Although warships were used by English and Scottish kings from the early medieval period, the first major maritime engagements were fought in the Hundred Years' War against ...
mine sweepers. Beginning in 1962, Gibbs invited
Mack Trucks
Mack Trucks, Inc., is an American truck manufacturing company and a former manufacturer of buses and trolley buses. Founded in 1900 as the Mack Brothers Company, it manufactured its first truck in 1905 and adopted its present name in 1922. Mack ...
to take part in designing FDNY’s super pumper and its companion tender. DeLaval Turbine was commissioned to design a multistage centrifugal pump with a Napier-Deltic T18-37C diesel to power the pumps.
In 1959, the
Leyland L60 six-cylinder diesel engine was introduced. The L60 was produced in the United Kingdom for use in the Chieftain tank. The
Soviet T-64 tank, produced from 1963-1987, also used an opposed-piston diesel engin
5TDF
Volvo
The Volvo Group ( sv, Volvokoncernen; legally Aktiebolaget Volvo, shortened to AB Volvo, stylized as VOLVO) is a Swedish multinational manufacturing corporation headquartered in Gothenburg. While its core activity is the production, distributio ...
filed for a patent in 2017.
The
Diesel Air Dair 100
The Diesel Air Dair 100 is an opposed-piston diesel aircraft engine, designed and produced by Diesel Air Ltd of Olney, Buckinghamshire for use in airships, home-built kitplanes and light aircraft.Tacke, Willi; Marino Boric; et al: ''World Direc ...
is a two-cylinder
diesel
Diesel may refer to:
* Diesel engine, an internal combustion engine where ignition is caused by compression
* Diesel fuel, a liquid fuel used in diesel engines
* Diesel locomotive, a railway locomotive in which the prime mover is a diesel engin ...
aircraft engine, designed and produced by Diesel Air Ltd of
Olney, Buckinghamshire
Olney (, rarely ) is a market town and civil parish in the unitary authority area of the City of Milton Keynes in Buckinghamshire, England. At the 2011 Census, it had a population of 6,477 people. It lies on the River Great Ouse and is the n ...
for use in
airship
An airship or dirigible balloon is a type of aerostat or lighter-than-air aircraft that can navigate through the air under its own power. Aerostats gain their lift from a lifting gas that is less dense than the surrounding air.
In early ...
s,
home-built kitplane
Homebuilt aircraft, also known as amateur-built aircraft or kit planes, are constructed by persons for whom this is not a professional activity. These aircraft may be constructed from "scratch", from plans, or from assembly kits.Armstrong, Kenn ...
s, and
light aircraft
A light aircraft is an aircraft that has a maximum gross takeoff weight of or less.Crane, Dale: ''Dictionary of Aeronautical Terms, third edition'', page 308. Aviation Supplies & Academics, 1997.
Light aircraft are used as utility aircraft co ...
.
In July 2021,
Cummins
Cummins Inc. is an American multinational corporation that designs, manufactures, and distributes engines, filtration, and power generation products. Cummins also services engines and related equipment, including fuel systems, controls, air ...
was awarded an $87M contract by the
United States Army
The United States Army (USA) is the land warfare, land military branch, service branch of the United States Armed Forces. It is one of the eight Uniformed services of the United States, U.S. uniformed services, and is designated as the Army o ...
to complete development of the Advanced Combat Engine (ACE), a modular and scalable diesel engine solution that uses opposed-piston technology.
Free-piston engine
A variation of the opposed-piston design is the free-piston engine, which was first patented in 1934. Free piston engines have no crankshaft, and the pistons are returned after each firing stroke by compression and expansion of air in a separate cylinder. Early applications were for use as an air compressor or as a gas generator for a
gas turbine
A gas turbine, also called a combustion turbine, is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas generator or core) and are, in the directio ...
.
See also
*
Junk head
*
Michel engine The Michel engine was an unusual form of opposed-piston engine. It was unique in that its cylinders, instead of being open-ended cylinders containing two pistons, were instead joined in a Y-shape and had three pistons working within them.
These eng ...
*
Split-single engine
In internal combustion engines, a split-single design is a type of two-stroke where two cylinders share a single combustion chamber.
The first production split-single engine was built in 1918 and the design was used on several motorcycles and ca ...
References
{{Authority control
Locomotive parts
Two-stroke diesel engines
Opposed piston engines
Piston ported engines
Piston engine configurations