Opposed-piston engine

[[File:Opposite piston engine.gif|framed|right|Schematic of a supercharged opposed-piston engine

1. Intake for fuel-air mixture

2. Supercharger

3. Airbox

4. Boost relief valve

5. Outlet crankshaft

6. Inlet crank mechanism

7. Cylinder with inlet and outlet slots

8. Exhaust

9. Water cooling jacket

10. Spark plug]]

Compared to contemporary two-stroke engines, which use a conventional design of one piston per cylinder, the advantages of the opposed-piston engine are:

• Eliminating the cylinder head and valve-train, which reduces weight, complexity, cost, heat loss, and friction loss of the engine.{{cite book |last1=Pirault |first1=Jean-Pierre |last2=Flint |first2=Martin |title=Opposed Piston Engines: Evolution, Use, and Future Applications |date=2010 |publisher=SAE International|isbn=9780768018004 |url=https://books.google.com/books?id=vVQIQgAACAAJ |access-date=20 November 2019 }}{{cite book|last=Foster|first=D.|chapter=Thermodynamic Benefits of Opposed-Piston Two-Stroke Engines|year=2011|publisher=SAE International|location=PA|chapter-url=http://papers.sae.org/2011-01-2216/|author2=Herold, R. |author3=Lemke, J. |author4=Regner, G. |author5= Wahl, M. |doi=10.4271/2011-01-2216|title=SAE Technical Paper Series|volume=1}}{{cite web |title=Start-Ups Work to Reinvent the Internal Combustion Engine |url=https://www.nytimes.com/2011/03/31/business/energy-environment/31ENGINE.html |website=New York Times|access-date=29 November 2019 |date=30 March 2011 }}
• Creating a uniflow-scavenged movement of gas through the combustion chamber,{{cite web |title=Opposed-Piston |url=http://achatespower.com/our-formula/opposed-piston/ |website=AchatesPower.com |date=22 July 2018 |access-date=29 November 2019 }}{{cite web |title=TROPE : Toroidal Opposed Piston Engine |url=https://www.youtube.com/watch?v=AM335uWoYBQ |archive-url=https://ghostarchive.org/varchive/youtube/20211221/AM335uWoYBQ |archive-date=21 December 2021 |url-status=live |website=YouTube.com | date=19 December 2010 |publisher=frankydevaere |access-date=29 November 2019 }}{{cbignore}} which avoided the drawbacks originally associated with the crossflow-scavenged designs of early piston-engines.
• A reduced height of the engine

The main drawback was that the two opposing pistons had 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).{{cite web |title=OPRE: Opposed piston Pulling Rod Engine |url=http://www.pattakon.com/pattakonOPRE.htm |website=Pattakon.com |access-date=29 November 2019 }} The Koreyvo, Jumo, and Napier Deltic 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.

File:Atkinson Opposed Piston Engine.gif

File:Jumo205 cutview 02.jpg diesel aircraft engine]]

One of the first opposed-piston engines was the 1882 Atkinson differential engine,{{cite book | last = Gingery | first = Vincent | title = Building the Atkinson Differential Engine | publisher = David J. Gingery Publishing | isbn = 1878087231 | year = 2000 }} which has a power stroke on every rotation of the crankshaft (compared with every second rotation for the contemporary Otto cycle engine), but it was not a commercial success.{{cite web |title=Atkinson Differential Engine Replica - Gas Engines |url=https://www.gasenginemagazine.com/gas-engines/atkinson-differential-engine-replica-zm0z18amzhur |website=GasEngineMagazine.com |date=13 March 2018 |access-date=22 November 2019 }}

In 1898, an Oechelhäuser two-stroke opposed-piston engine producing {{convert|600|hp|kW|0|abbr=on}} was installed at the Hoerde ironworks.{{cite journal |title=Large Gas Engines on the Continent |journal=Page's Weekly |date=23 June 1905 |pages=1336–1337 }} 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.{{cite conference |last1=Stokes |first1=Jason W. B. |last2=Cunningham |first2=Jason |title=The Oechelhauser Gas Engine in Great Britain: Paper Read Before the Glasgow University Engineering Society |date=11 November 1909 |url=https://books.google.com/books?id=mZB8MQAACAAJ |publisher=William Beardmore & Company }}

In 1901, the Kansas City Lightning Balanced Gas and Gasoline Engines were gasoline engines producing {{convert|4|-|25|hp|kW|0|abbr=on}}.{{cite web |title=Struck by Lightning: The Kansas City Hay Press Co. - Gas Engines |url=https://www.farmcollector.com/gas-engines/kansas-city-hay-press-co-engines |website=FarmCollector.com |date=April 1999 |access-date=26 November 2019 }}

An early opposed-piston car engine was produced by the French company Gobron-Brillié around 1900. On 31 March 1904,{{cite book |editor-last=Berghaus |editor-first=Günter |date=2009 |title=Futurism And The Technological Imagination |publisher=Rudopi |location=Amsterdam & New York |page=8 |isbn=978-90-420-2747-3 |url=https://books.google.com/books?id=MOIzDwAAQBAJ&pg=PA8 |via=Google Books |access-date=9 October 2024}}{{cite web |url=http://www.racingcampbells.com/content/world.land.speed.record.asp |title=World Land Speed Records |publisher=RacingCampbells.com |archive-url=https://web.archive.org/web/20070831073900/http://www.racingcampbells.com/content/world.land.speed.record.asp |archive-date=31 August 2007 |access-date=8 October 2024}} 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 {{convert|152.54|km/h|mph|0|abbr=on}}.{{cite journal |title=Nice Automobile Week: Third, Coupe Henri de Rothschild |journal=The Automotor Journal |date=9 April 1904 |page=426 }} On 17 July 1904, the Gobron-Brillié car became the first to exceed {{convert|100|mph|km/h|0|abbr=on}} for the flying kilometre.{{cite web |url=http://www.uniquecarsandparts.com.au/lost_marques_gobron_brillie.htm |title=Gobron-Brillie history |website=UniqueCarsAndParts.com.au |archive-url=https://web.archive.org/web/20130825070116/http://www.uniquecarsandparts.com.au/lost_marques_gobron_brillie.htm |archive-date=25 August 2013}} 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 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.{{cite journal |title=The New Arrol-Johnston Petrol Car – Part II |journal=The Automotor Journal |date=25 November 1905 |pages=1467–1469 }}{{cite journal |title=The New Arrol-Johnston Petrol Car – Part III |journal=The Automotor Journal |date=2 December 1905 |pages=1495–1496 }} The engine was a four-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 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.{{cite journal |title=A Horizontally Opposed Two-stroke Engine |journal=The Motor Cycle |date=6 August 1914 |page=204 }} 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.{{cite web |title=Index Doxford site |url=http://users.telenet.be/doxford-matters/ |website=Telenet.be |access-date=26 November 2019 }} This diesel engine used a single crankshaft at one end of the cylinders and a crosshead for the opposing piston.{{Cite web |url=http://www.oldengine.org/members/diesel/Marine/doxford.htm |title=Marine Engines – Doxford |website=OldEngine.org |archive-url=https://web.archive.org/web/20131202224409/http://www.oldengine.org/members/diesel/Marine/doxford.htm |archive-date=2 December 2013 }}{{cite web |title=PatOP: Single-Crankshaft Opposed-Piston Engine |url=http://www.pattakon.com/pattakonPatOP.htm |website=Pattakon.com |access-date=29 November 2019 }} 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 {{convert|20000|hp|kW|0|abbr=on}}. Production of Doxford engines in the UK ceased in 1980.{{Cite web|url=http://www.doxford-engine.com/ |title=Doxford Engines 1878–1980 |website=Doxford-Engine.com |access-date=28 March 2006 |archive-url=https://web.archive.org/web/20161224093713/http://www.doxford-engine.com/ |archive-date=24 December 2016 }}

Later opposed-piston diesel engines include the 1932 Junkers Jumo 205 aircraft engine built in Germany, which had two crankshafts, not using a design similar to the 1900–1922 Gobron-Brillié engines.{{cite book |last=Setright |first=L. J. K. |title=Some unusual engines |date=1975 |publisher=Mechanical Engineering Publications for the Institution of Mechanical Engineers|isbn=9780852982082 |url=https://books.google.com/books?id=pqhTAAAAMAAJ |access-date=20 November 2019 }}

{{clear right}}

File:OechelhäuserEngine.jpg|1898 Oechelhäuser gas engine

File:Gobron engine (Autocar Handbook, Ninth edition).jpg|1900 Gobron-Brillié opposed-piston engine with overhung yoke

File:Opposed piston engine 1.jpg|Fairbanks Morse 38 8-1/8 diesel engine on the {{USS|Pampanito|SS-383|6}} submarine

File:The Tank Museum (2383).jpg|Leyland L60 as used in the Chieftain tank

The Fairbanks Morse 38 8-1/8 diesel engine, designed in Germany in the 1930s, was used in U.S. submarines in the 1940s and 1950s, and in boats from the 1930s-present.{{cite web |title=Fairbanks-Morse 38D8 Diesel Engine |url=http://www.psrm.org/roster/diesel/fm/index.html |website=PSRM.org |archive-url=https://web.archive.org/web/20060526222933/http://www.psrm.org/roster/diesel/fm/index.html |archive-date=26 May 2006 }} It has been used in locomotives since 1944.

The November 2021 version of the Fairbanks-Morse 38 8-1/8, the FM 38D 8-1/8 Diesel and Dual Fuel, retains the same extra-heavy-duty design and has a rated in-service lifespan of more than 40 years, but now can burn dual fuels (gaseous and liquid fuels, with automatic switchover to full diesel if the gas supply runs out).{{Cite web |url=https://www.fairbanksmorse.com/38d-8-1/8 |title=Fairbanks-Morse FM 38D 8-1/8 Diesel and Dual Fuel }}

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.{{Cite web |url=http://www.oldengine.org/members/diesel/technical/TS3.htm |title=Rootes-Lister – TS3 Horizontally Opposed Piston Engine |website=OldEngine.org |archive-url=https://web.archive.org/web/20080225131409/http://www.oldengine.org/members/diesel/technical/TS3.htm |archive-date=25 February 2008 }}

File:Napier Deltic Animation.gif

Also released in 1954 was the Napier Deltic 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 and British Rail Class 23 locomotives and to power fast patrol boats and Royal Navy mine sweepers. Beginning in 1962, Gibbs invited Mack Trucks 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.{{Cite web |url=https://www.firerescue1.com/fire-products/fire-apparatus/articles/the-greatest-fire-pumper-the-world-has-known-TrMsI86bXHcXv1iq |title=The Greatest Fire Pumper the World Has Known (Fire Rescue 1) |date=8 January 2016 }}

In 1959, the Leyland L60 {{convert|19|L|cuin|0|abbr=on}} six-cylinder diesel engine was introduced. The L60 was produced in the United Kingdom for use in the Chieftain tank.{{cite web |website=AchatesPower.com |title=Engine Design Timeline |url=http://www.achatespower.com/engine-design-timeline.php |archive-url=https://web.archive.org/web/20130513130430/http://www.achatespower.com/engine-design-timeline.php |archive-date=13 May 2013 }}

The Soviet T-64 tank, produced from 1963–1987, also used an opposed-piston diesel engine {{Not translated|5TD|uk|5ТД}} developed by Malyshev Factory in Kharkiv. After the dissolution of the Soviet Union Malyshev Factory continued development and production of opposed-piston engines for armored vehicles, such as the three-cylinder {{Not translated|3TD|uk|3ТД}} used in BTR-4 Butsefal, various upgrades of the 5TD and the six-cylinder {{Not translated|6TD|uk|6ТД}} for T-64BM2, BM Oplot etc.

In 2014, Achates Power published a technical paper citing a 30% fuel economy improvement when its engine was benchmarked against a next-generation diesel engine equipped with advanced technologies.

Volvo filed for a patent in 2017.{{Cite web |url=https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=2017122199A1&KC=A1&FT=D&ND=3&date=20170504&DB=&locale=en_EP# |title=Two-stroke Opposed Piston Internal Combustion Engine |website=Espacenet |access-date= 20 November 2019 }}

The Diesel Air Dair 100 is a two-cylinder {{convert|100|hp|kW|0|abbr=on}} diesel aircraft engine, designed and produced by Diesel Air Ltd of Olney, Buckinghamshire for use in airships, home-built kitplanes, and light aircraft.{{cite press release |title=Diesel Air pamphlet |location=Olney, Buckinghamshire, United Kingdom |publisher=Diesel Air |date=2002 }}

In July 2021, Cummins was awarded an $87M contract by the United States Army to complete the development of the Advanced Combat Engine (ACE), a modular and scalable diesel engine solution that uses opposed-piston technology.{{Cite web |url=https://www.cummins.com/news/releases/2021/07/30/us-army-awards-cummins-inc-87m-contract-deliver-advanced-combat-engine |title=U.S. Army Awards Cummins Inc. $87M Contract to Deliver the Advanced Combat Engine |website=Cummins }}

{{Main|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.{{Citation needed|date=May 2024}}

• Junk head
• Michel engine
• Split-single engine

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{{Piston engine configurations}}

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Category:Opposed piston engines

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