Caffort 12Aa

12Aa
Type	12-cylinder, water-cooled, horizontally-opposed piston engine
National origin	France
Manufacturer	Anciens Etablissements Caffort Frères
First run	1926

Last updated May 08, 2019

The Caffort 12Aa was a 12-cylinder, horizontally-opposed, piston aircraft engine designed and built in France during the latter half of the 1920s.

Aircraft engine Engine designed for use in powered aircraft

An aircraft engine is a component of the propulsion system for an aircraft that generates mechanical power. Aircraft engines are almost always either lightweight piston engines or gas turbines, except for small multicopter UAVs which are almost always electric aircraft.

France, officially the French Republic, is a country whose territory consists of metropolitan France in Western Europe and several overseas regions and territories. The metropolitan area of France extends from the Mediterranean Sea to the English Channel and the North Sea, and from the Rhine to the Atlantic Ocean. It is bordered by Belgium, Luxembourg and Germany to the northeast, Switzerland and Italy to the east, and Andorra and Spain to the south. The overseas territories include French Guiana in South America and several islands in the Atlantic, Pacific and Indian oceans. The country's 18 integral regions span a combined area of 643,801 square kilometres (248,573 sq mi) and a total population of 67.3 million. France, a sovereign state, is a unitary semi-presidential republic with its capital in Paris, the country's largest city and main cultural and commercial centre. Other major urban areas include Lyon, Marseille, Toulouse, Bordeaux, Lille and Nice.

Design and development

Having produced automobile and aircraft engine parts under contract during WWI, the Caffort brothers set about the task of producing their own aircraft engine, under a licence from "Bertrand-Solanet", of whom there is very little known, leaving the Caffort 12Aa as a testament.^[1]

Built largely from cast Aluminium alloys the 12Aa was a geared engine with four Zenith carburetors supplying mixture to the lower intake valves. Four camshafts at the corners of the crankcase operated two intake valves and two exhaust valves per cylinder, also driving oil pumps and other accessories. The four magnetos were mounted on transverse shafts driven from the crankshaft at the front of the engine. A single water pump was mounted on the rear cover, driven directly from the crankshaft.^[2]

Aluminium alloy alloy in which aluminium is the predominant metal

Aluminium alloys are alloys in which aluminium (Al) is the predominant metal. The typical alloying elements are copper, magnesium, manganese, silicon, tin and zinc. There are two principal classifications, namely casting alloys and wrought alloys, both of which are further subdivided into the categories heat-treatable and non-heat-treatable. About 85% of aluminium is used for wrought products, for example rolled plate, foils and extrusions. Cast aluminium alloys yield cost-effective products due to the low melting point, although they generally have lower tensile strengths than wrought alloys. The most important cast aluminium alloy system is Al–Si, where the high levels of silicon (4.0–13%) contribute to give good casting characteristics. Aluminium alloys are widely used in engineering structures and components where light weight or corrosion resistance is required.

The Zenith Carburetter Company Limited was a British company making carburettors in Stanmore Middlesex founded in 1910. In 1965 they joined with their major pre-war rival Solex Carburettors and over time the Zenith brand name fell into disuse. The rights to the Zenith designs were owned by Solex UK.

Specifications (12Aa)

Data from Jane's all the World's Aircraft 1928^[2]

General characteristics

Type: 12 cylinder water-cooled horizontally-opposed piston engine
Bore: 145 mm (5.7 in)
Stroke: 150 mm (5.9 in)
Displacement: 29.73 l (1,814.24 cu in)
Dry weight: 550 kg (1,210 lb) dry

Components

Valvetrain: 4x camshafts operating inlet and exhaust valves via fully enclosed push-rods and rockers
Fuel system: 4x Zenith carburetors
Fuel type: Aviation gasoline
Oil system: Dry sump pressure system
Cooling system: water-cooled
Reduction gear: 0.53:1 two-stage spur gear to co-axial propeller shaft

A valvetrain or valve train is a mechanical system that controls operation of the valves in an internal combustion engine, whereby a sequence of components transmits motion throughout the assembly.

A propeller speed reduction unit is a gearbox or a belt and pulley device used to reduce the output revolutions per minute (rpm) from the higher input rpm of the powerplant. This allows the use of small displacement internal combustion automotive engines to turn aircraft propellers within an efficient speed range.

Performance

Power output: 370 kW (500 hp) maximum at 2,200 rpm
Specific fuel consumption: 0.335 kg/kW hour (0.55 lb/hp hour)

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References

↑ Vidal, Miguel Ricardo (2012). El Motor de Aviación de la A a la Z (in Spanish). Aeroteca. pp. 574–575. ISBN 978-84-612-7902-9.
1 2 Grey, C.G., ed. (1928). Jane's all the World's Aircraft 1928. London: Sampson Low, Marston & company, ltd. p. 26d.