Up to 1927, Hispano-Suiza’s many engine types, of various layouts and cylinder numbers, were all recognisable developments of the World War I V-8 Hispano-Suiza 8. 1927-8 saw the introduction of four completely new engines, two V-12s designed by Marc Birkigt, and two with six cylinders inline. The Hispano-Suiza 12N, known by the manufacturers as the Type 61, was the larger of the V-12s, with a displacement of 36.0 L (2,197 cu in), the other being the 27.0 L (1,648 cu in) 12M. Apart from capacity and power, these two engines had much in common. The 12M first ran in 1927 and the 12N a year later.
Both 12M and 12N were 60° V engines with carburettors, inlets and exhausts on the outer faces. There were three carburettors per bank, each charging a pair of cylinders. Much of the new technology was in the cylinder design: these types introduced wet liners, an Hispano automobile engine innovation which brought the cooling water into direct contact with the steel cylinder barrel rather than by screwing it into an aluminium water jacket. This improved cooling, simplified assembly and allowed larger cylinder bores without increasing their separation. The cylinder barrels were open at top and bottom and threaded for screwing into the block only near the top, with valve seats ground into the aluminium cylinder head. The lower end of the barrel extended into the crankcase, simplifying both manufacture and assembly. Block and crankcase were bolted together.
The 12M and 12N engines were the first to use the gas nitriding surface hardening process on the cylinder walls, which reduced both wear and oil consumption. They also used a novel, complicated but effective method of main bearing cooling, enhancing the local lubricant flow without requiring high overall oil pump speeds. The unit cost in 1931 was 250,000 FF.
Both types were designed so that Epicyclic gearing could be added or removed quickly; some earlier Hispano-Suiza engines offered gearing but as a permanent fixture on a specific sub-type. The gears added 45 kg (99 lb) to the weight. In 1935 the 12Ner variant was fitted with an in-flight- electrically operated variable pitch propeller.
The 12N series was developed into the 12Y (Type 73) supercharged engine, first run in 1932.
A Hispano-Suiza 12Nb powered the Breguet XIX Point d’Interrogation on the first non-stop flight from Paris to New York in September 1930. This was the first east to west flight between Europe and the USA, rather than to the North American continent.
In the early 1930s, 12N engines powered the flying boats operating the French Atlantic and African routes.
The Swiss government, in the form of the KTA (Kriegstechninischen Abteilung or War Technical Department) purchased construction licences for the 12Nb and in 1932 eighty units were built at the Saurer lorry factory.
Variants:
12Nb/650
Compression ratio 6.2, maximum power 560 kW (750 hp) at 2,100 rpm.
12Nbr/650
Compression ratio 6.2, maximum power 550 kW (740 hp) at 2,100 rpm. Gearing ratio of 2:1 or 1.61:1.
12Ns
Compression ratio 7, nominal power 670 kW (900 hp) at 2,200 rpm. For Schneider Cup 1928.
12Nsr
Compression ratio 10, nominal power 745 kW (1,000 hp) at 2,400 rpm. For Schneider Cup 1931. Farman compressor.
12Nc
Compression ratio 6.2, nominal power 533 kW (715 hp) at 2,000 rpm. For Ford 14A Trimotor.
12Ncr
12Ndr
Electrically controlled pitch propeller, anti-clockwise turning (1935).
12Ner
As 12Ndr, modified with articulated connecting rods.
12Nfr
As Ndr, clockwise turning.
12Ngr
As Ner, clockwise turning.
Applications:
Amiot 140
Avia B-34
Bernard H.V.41
Bernard H.V.42
Bernard 80 & 81
Blériot 5190
Breguet XIX Point d’Interrogation
Breguet 330
CAMS 58.3
Couzinet 70
Farman F.302
Latécoère 28
Latécoère 290
Latécoère 300 and 301
Latécoère 381
Latécoère 440
Latécoère 490
Latécoère 521
Letov Š-616
Levasseur PL.14
Levasseur PL.15
Lioré et Olivier LeO 25.8
Westland Wapiti IV (uncertain if completed with 14N)
Specifications:
12Nbr/650
Type: V-12, water cooled
Bore: 150 mm (5.90 in)
Stroke: 170 mm (6.69 in)
Displacement: 36.0 L (2,197 cu in)
Dry weight: 520 kg (1146 lb)
Reduction gear: 2:1
Power output: (normal) 550 kW (740 hp) at 2,000 rpm
Compression ratio: 6.2
