The Renault 12F is a family of liquid-cooled 22 L (1,300 cu in) 50 deg V12 aircraft engines that saw widespread use during World War I and the 1920s.
The 12F series was developed from Renault's 8G engines with the two series sharing the same cylinder bore and stoke. 12F series engines were built in Renault's factories in France, Russia and the United Kingdom.
Renault designated early engines in the series by their nominal output of 220 hp (160 kW). The engines were progressively improved with the introduction of aluminum pistons allowing for increased power and reduced weight. These progressive improvements eventually lead to the development of a 300 hp (220 kW) variant which was designated as the 12Fe by the Service Technique de l'Aéronautique (STAe) while being known, and marketed, as the 300 CV (cheval-vapeur) (French: "horsepower”) by Renault.
Design and development
In 1914, Renault began building their first water cooled V8 aircraft engines which became known as the 8G series. In 1915, Renault's engineers added two more cylinders to produce a V12 engine with the same bore, stroke and bank angle as the 8Gs. The series became known as the 12F.[1]
Engines in the series are V12s with a 50 degree angle between two rows of cylinders each of which has a single overhead camshaft. The crankshaft is carried on four plain bearings with master-and-slave connecting rods allowing corresponding cylinders in each row to be arranged directly opposite each other. Cylinders have a bore of 125 mm (4.92 in), a stroke of 150 mm (5.91 in) and are built in pairs with water circulated in welded liners.[2][3]
All engines in the series have ignition systems with 100% redundancy. Two spark plugs per cylinder and four magnetos (two per cylinder bank).[4][5]
Brochure image of an early 12F variant with radial starter motor
The early 12F engines were often supplied with an aluminium six-cylinder radialpneumatic starter motor which was mounted on the back of the engine.[4][6] The pneumatic motor allowed the engine to be restarted mid-flight or on the ground without assistance from ground crew. The starter motor was fed from a pressurised vessel with enough air for ten starts.[4] The device was not included in later models.[2][5][6]
In late 1915 the 220 hp (12Fa) model used cast iron pistons. The engines were progressively improved with the introduction of aluminum pistons allowing for increased power output and reduced weight.[2]
In 1917, the 12Fe model was homologated with a nominal rating of 300 hp (224 kW) (later increased to 320 hp (239 kW)).[7] The 12Fe became the standard powerplant for the Breguet 14[8] and accounted for the vast majority of engines built from the series.[7]
12F series engines were exported to the United States[8] and produced in the United Kingdom.[9]
In Russia, Renault 12F engines were assembled from imported parts by the Russian Renault Society in Petrograd.[10][11] A total of 98 engines were assembled from July 1916 to September 1917. All the engines assembled were early 12F models with cast iron pistons. In 1921 the 12F was re-designated as the M-3 under a new Soviet numbering system which included the M-1 (RBVZ-6) and the M-2 (Le Rhone 9J).[11]
Variants
Publications often refer to the 12Fe as the Renault 300 hp with earlier engines in the series referred to as the Renault 220 hp.[6] Post WW1 the 12Fe engine was marketed as the 300 CV (cheval-vapeur) (French: "horsepower”).[12]
12Fa
(1915) Rating of 220 hp (164 kW) at 1300 rpm.[7][8] Used on the Breguet 14s and Henry Farman HF.35 prototypes.[7] The HF.35 made its first flight in December 1915.[13]
Used on early model Bréguet 14s. 12Fcx (250 hp (186 kW) at 1500 rpm) and 12Fcy (280 hp (209 kW) at 1600 rpm) sub-variants. In US service 12Fc engines were all rated at 300 hp (224 kW).[8]
Rated for 300 hp (224 kW) at 1600 rpm. Main production variant in the series and the standard power-plant in the Breguet 14 from early in 1918 onwards.[8] The names 12Fe and 300 CV / hp (cheval-vapeur / horsepower) are used interchangeably in post war technical documentation.[15] Some of these engines were fitted with early experimental Rateauturbochargers.[16]
12Ff
Sometimes used to describe a small number of engines produced with increased bore (128 mm) and stroke (160 mm). Rated for 350 hp (261 kW) at 1,600 rpm. These engines were fitted to a few late production Breguet 14s.[16]
Applications
12Fa, 12Fb and 12Fc
Breguet 5 powered by a single Renault 12Fb engine (1916)
^ abKotelnikov, Vladimir (2010). Отечественные авиационные поршневые моторы. 1910–2009 [Domestic aircraft piston engines. 1910–2009] (in Russian). Litres. pp. 54–63. ISBN978-5-91244-017-5.
^Hatry, Gilbert (1984). Renault et l'aviation [Renault and aviation] (in French). Editions JCM. pp. 32–41 – via Safran.
^Liron, J (1984). Les Avions Farman (in French). Docavia / Editions Lariviere. p. 46.
^Treadwell, Terry (2011). "Société des Avions Louis Breguet". British and Allied Aircraft Manufacturers of the First World War. United Kingdom: Amberley. ISBN9781445620091.
^Type 14 A2. Model 1921(PDF). Notice technique de l'avion Breguet (Report). Ministere de la guerre. 24 April 1922.
^ abBruce, J.M; Noel, Jean (1967). The Breguet 14. 157. United Kingdom: Profile Publications. ASINB0007JXD5I.
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