Radial engine
Four-stroke radials have an odd number of cylinders per row, so that a consistent every-other-piston firing order can be maintained, providing smooth operation.
As with most four-strokes, the crankshaft takes two revolutions to complete the four strokes of each piston (intake, compression, combustion, exhaust).
Motorenfabrik Oberursel made licensed copies of the Gnome and Le Rhône rotary powerplants, and Siemens-Halske built their own designs, including the Siemens-Halske Sh.III eleven-cylinder rotary engine, which was unusual for the period in being geared through a bevel geartrain in the rear end of the crankcase without the crankshaft being firmly mounted to the aircraft's airframe, so that the engine's internal working components (fully internal crankshaft "floating" in its crankcase bearings, with its conrods and pistons) were spun in the opposing direction to the crankcase and cylinders, which still rotated as the propeller itself did since it was still firmly fastened to the crankcase's frontside, as with regular umlaufmotor German rotaries.
[citation needed] In the United States the National Advisory Committee for Aeronautics (NACA) noted in 1920 that air-cooled radials could offer an increase in power-to-weight ratio and reliability; by 1921 the U.S. Navy had announced it would only order aircraft fitted with air-cooled radials and other naval air arms followed suit.
[7] Wright employed Giuseppe Mario Bellanca to design an aircraft to showcase it, and the result was the Wright-Bellanca WB-1, which first flew later that year.
The J-5 was used on many advanced aircraft of the day, including Charles Lindbergh's Spirit of St. Louis, in which he made the first solo trans-Atlantic flight.
[10][11] 125,334 of the American twin-row, 18-cylinder Pratt & Whitney R-2800 Double Wasp, with a displacement of 2,800 in3 (46 L) and between 2,000 and 2,400 hp (1,500-1,800 kW), powered the American single-engine Vought F4U Corsair, Grumman F6F Hellcat, Republic P-47 Thunderbolt, twin-engine Martin B-26 Marauder, Douglas A-26 Invader, Northrop P-61 Black Widow, etc.
[citation needed] The Guiberson T-1020, a 9-cylinder radial diesel aero engine, was used in the M1A1E1, while the Continental R975 saw service in the M4 Sherman, M7 Priest, M18 Hellcat tank destroyer, and the M44 self propelled howitzer.
Verner Motor of the Czech Republic builds several radial engines ranging in power from 25 to 150 hp (19 to 112 kW).
The National Advisory Committee for Aeronautics studied the problem, developing the NACA cowling which further reduced drag and improved cooling.
The first radial-configuration engine known to use a twin-row design was the 160 hp Gnôme "Double Lambda" rotary engine of 1912, designed as a 14-cylinder twin-row version of the firm's 80 hp Lambda single-row seven-cylinder rotary, however reliability and cooling problems limited its success.
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.
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.
[citation needed] Examples include the Bristol Centaurus in the Hawker Sea Fury, and the Shvetsov ASh-82 in the Lavochkin La-7.
[citation needed] For even greater power, adding further rows was not considered viable due to the difficulty of providing the required airflow to the rear banks.
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 turboprops such as the Armstrong Siddeley Python and Bristol Proteus, which easily produced more power than radials without the weight or complexity.
An example is the 5-ton Zvezda M503 diesel engine with 42 cylinders in 6 rows of 7, displacing 143.6 litres (8,760 cu in) and producing 3,942 hp (2,940 kW).
[citation needed] 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 in3 (127 L) of displacement and a power output of 5,000 horsepower (3,700 kilowatts).
Two major advantages favour diesel engines — lower fuel consumption and reduced fire risk.
[citation needed] Packard designed and built a 9-cylinder 980 cubic inch (16.06 litre) displacement diesel radial aircraft engine, the 225 horsepower (168 kW) 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.
[23] 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] The Nordberg Manufacturing Company of the United States developed and produced a series of large 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.
[26][independent source needed] A number of radial motors operating on compressed air have been designed, mostly for use in model airplanes and in gas compressors.
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.
Pistons are in gold and valves in pink, master rod in pale purple, slaved connecting rods in blue, crankshaft / counterbalance in gray and timing ring and cams in red.
