Editing Radial engine (section)

==Other types of radial engine==

===Multi-row radials===
[[File:Pratt & Whitney R-4360 Wasp Major 1.jpg|thumb|The [[Pratt & Whitney R-4360 Wasp Major|Wasp Major]], a four-row radial]]
Originally radial engines had one row of cylinders, but as engine sizes increased it became necessary to add extra rows.  The first radial-configuration engine known to use a twin-row design was the 160&nbsp;hp Gnôme "Double Lambda" rotary engine of 1912, designed as a 14-cylinder twin-row version of the firm's 80&nbsp;hp [[Gnome Lambda|Lambda]] single-row seven-cylinder rotary, however reliability and cooling problems limited its success.

Two-row designs began to appear in large numbers during the 1930s, when aircraft size and weight grew to the point where single-row engines of the required power were simply too large to be practical. Two-row designs often had cooling problems with the rear bank of cylinders, but a variety of baffles and fins were introduced that largely eliminated these problems. The downside was a relatively large frontal area that had to be left open to provide enough airflow, which increased drag. This led to significant arguments in the industry in the late 1930s about the possibility of using radials for high-speed aircraft like modern fighters.{{Citation needed|date=October 2014}}

The solution was introduced with the BMW 801 14-cylinder twin-row radial. [[Kurt Tank]] designed a new cooling system for this engine that used a high-speed fan to blow compressed air into channels that carry air to the middle of the banks, where a series of baffles directed the air over all of the cylinders. This allowed the cowling to be tightly fitted around the engine, reducing drag, while still providing (after a number of experiments and modifications) enough cooling air to the rear. This basic concept was soon copied by many other manufacturers, and many late-WWII aircraft returned to the radial design as newer and much larger designs began to be introduced.{{Citation needed|date=October 2014}} Examples include the [[Bristol Centaurus]] in the [[Hawker Sea Fury]], and the [[Shvetsov ASh-82]] in the [[Lavochkin La-7]].{{Citation needed|date=October 2014}}

For even greater power, adding further rows was not considered viable due to the difficulty of providing the required airflow to the rear banks. Larger engines were designed, mostly using water cooling although this greatly increased complexity and eliminated some of the advantages of the radial air-cooled design. One example of this concept is the [[BMW 803]], which never entered service.{{Citation needed|date=October 2014}}

A major study{{which|date=October 2014}} into the airflow around radials using [[wind tunnel]]s and other systems was carried out in the US, and demonstrated that ample airflow was available with careful design. This led to the [[Pratt & Whitney R-4360|R-4360]], which has 28 cylinders arranged in a 4 row ''[[corncob]]'' configuration. The R-4360 saw service on large American aircraft in the post-[[World War II]] period. The US and [[Soviet Union]] continued experiments with larger radials, but the UK abandoned such designs in favour of newer versions of the Centaurus and rapid movement to the use of [[turboprop]]s such as the [[Armstrong Siddeley Python]] and [[Bristol Proteus]], which easily produced more power than radials without the weight or complexity.{{Citation needed|date=October 2014}}

Large radials continued to be built for other uses, although they are no longer common. An example is the 5-ton [[Zvezda M503]] diesel engine with 42 cylinders in 6 rows of 7, displacing {{convert|143.6|L|cuin}} and producing {{convert|3942|hp|kW|abbr=on}}. Three of these were used on the fast [[Osa class missile boat]]s.{{Citation needed|date=October 2014}} Another one was the [[Lycoming XR-7755]] which was the largest piston aircraft engine ever built in the United States with 36 cylinders totaling about 7,750 in<sup>3</sup> (127 L) of displacement and a power output of 5,000 horsepower (3,700 kilowatts).

===Diesel radials===
[[File:Packard DR-980 USAF.jpg|thumb|Packard DR-980 diesel radial aircraft engine]]
[[File:Nordberg radial engine 648.JPG|thumb|A [[Nordberg Manufacturing Company]] two-stroke diesel radial engine for power generation and pump drive purposes]]

While most radial engines have been produced for gasoline, there have been diesel radial engines. Two major advantages favour [[diesel engine]]s — lower fuel consumption and reduced fire risk.{{Citation needed|date=October 2014}}

;Packard
Packard designed and built a 9-cylinder 980 cubic inch (16.06 litre) displacement diesel radial aircraft engine, the {{convert|225|hp|kW}} [[Packard DR-980|DR-980]], in 1928. On 28 May 1931, a DR-980 powered [[Bellanca CH-300]], with 481 gallons of fuel, piloted by [[Walter Edwin Lees]] and [[Frederick Brossy]] set a record for staying aloft for 84 hours and 32 minutes without being refueled.<ref>[http://www.enginehistory.org/Diesels/CH1.pdf Chapter 1: Development of the Diesel Aircraft Engine"] {{webarchive|url=https://web.archive.org/web/20120212213152/http://www.enginehistory.org/Diesels/CH1.pdf |date=2012-02-12 }} Aircraft Engine Historical Society — Diesels p.4 Retrieved: 30 January 2009.</ref> This record stood for 55 years until broken by the [[Rutan Voyager]].<ref>[http://www.aerofiles.com/chrono.html Aviation Chronology] Retrieved: 7 February 2009.</ref>

;Bristol
The experimental [[Bristol Phoenix]] of 1928–1932 was successfully flight tested in a [[Westland Wapiti]] and set altitude records in 1934 that lasted until World War II.{{Citation needed|date=October 2014}}

;Clerget
In 1932 the French company Clerget developed the 14D, a 14-cylinder [[two-stroke diesel engine|two-stroke diesel]] radial engine. After a series of improvements, in 1938 the 14F2 model produced {{convert|520|hp|kW|abbr=on}} at 1910 rpm cruise power, with a power-to-weight ratio near that of contemporary gasoline engines and a [[Brake specific fuel consumption|specific fuel consumption]] of roughly 80% that for an equivalent gasoline engine. During WWII the research continued, but no mass-production occurred because of the Nazi occupation. By 1943 the engine had grown to produce over {{convert|1000|hp|kW|abbr=on}} with a [[turbo-supercharger|turbocharger]]. After the war, the Clerget company was integrated in the [[SNECMA]] company and had plans for a 32-cylinder diesel engine of {{convert|4000|hp|kW|abbr=on}}, but in 1947 the company abandoned piston engine development in favour of the emerging turbine engines.{{Citation needed|date=October 2014}}

;Nordberg
The [[Nordberg Manufacturing Company]] of the United States developed and produced a series of large [[two-stroke engine|two-stroke]] radial diesel engines from the late 1940s for electrical production, primarily at [[aluminum]] smelters and for pumping water. They differed from most radials in that they had an even number of cylinders in a single bank (or row) and an unusual double master connecting rod. Variants were built that could be run on either diesel oil or gasoline or mixtures of both. A number of powerhouse installations utilising large numbers of these engines were made in the U.S.<ref>{{cite web|publisher=OldEngine|url=http://www.oldengine.org/members/diesel/Nordberg/Nordmenu.htm|title=Nordberg Diesel Engines|access-date=2006-11-20|archive-date=2018-09-19|archive-url=https://web.archive.org/web/20180919132942/http://www.oldengine.org/members/diesel/Nordberg/Nordmenu.htm|url-status=dead}}</ref>

;EMD
[[Electro-Motive Diesel]] (EMD) built the "pancake" engines 16-184 and 16-338 for marine use.<ref>{{cite web|url=https://oldmachinepress.com/2014/08/17/general-motors-electro-motive-16-184-diesel-engine/|title=General Motors / Electro-Motive 16-184 Diesel Engine|first=William|last=Pearce|date=18 August 2014|work=oldmachinepress.com|access-date=30 May 2016}}</ref>

;Zoche
[[Zoche aero-diesel]]s are a prototype radial design that have an even number of cylinders, either four or eight; but this is not problematic, because they are [[two-stroke engine]]s, with twice the number of power strokes as a four-stroke engine per crankshaft rotation.<ref>{{cite web|url=http://www.zoche.de|title=zoche aero-diesels homepage|work=zoche.de|access-date=30 May 2016}}</ref>{{third-party inline|date=November 2023}}

===Compressed air radial engines===
A number of radial motors operating on compressed air have been designed, mostly for use in model airplanes and in gas compressors.<ref>{{cite web |url=http://www.bock.de/en/Product_overview.html?ArticleSizesGroupID=169 |title=Bock radial piston compressor |publisher=Bock.de |date=2009-10-19 |access-date=2011-12-06 |archive-date=2011-10-08 |archive-url=https://web.archive.org/web/20111008145502/http://www.bock.de/en/Product_overview.html?ArticleSizesGroupID=169 |url-status=dead }}</ref>

===Model radial engines===
A number of multi-cylinder 4-stroke [[model engine]]s have been commercially available in a radial configuration, beginning with the Japanese [[O.S. Max]] firm's FR5-300 five-cylinder, 3.0 cu.in. (50&nbsp;cm<sup>3</sup>) displacement "Sirius" radial in 1986. The American "Technopower" firm had made smaller-displacement five- and seven-cylinder model radial engines as early as 1976, but the OS firm's engine was the first mass-produced radial engine design in [[Flying model aircraft|aeromodelling]] history.  The rival Saito Seisakusho firm in Japan has since produced a similarly sized five-cylinder radial four-stroke model engine of their own as a direct rival to the OS design, with Saito also creating a series of three-cylinder methanol and gasoline-fueled model radial engines ranging from 0.90 cu.in. (15&nbsp;cm<sup>3</sup>) to 4.50 cu.in. (75&nbsp;cm<sup>3</sup>) in displacement, also all now available in spark-ignition format up to 84&nbsp;cm<sup>3</sup> displacement for use with gasoline.<ref>[http://www.saito-mfg.com/e-book/_SWF_Window.html Saito Seisakusho Worldwide E-book catalog, pages 9, 17 & 18]</ref> The German Seidel firm formerly made both seven- and nine-cylinder "large" (starting at 35&nbsp;cm<sup>3</sup> displacement) radio control model radial engines, mostly for glow plug ignition, with an experimental fourteen-cylinder twin-row radial being tried out - the American Evolution firm now sells the Seidel-designed radials, with their manufacturing being done in India.{{Citation needed|date=October 2014}}