Napier Lion

The Lion was a 12 -cylinder Y- flight engine from Napier. As a " Y motor " he had three banks of four cylinders. It was in 1917 designed and produced from 1918 until the 1930s. Because many advanced features, he was the most powerful engine of its time and thus as a drive for various racing airplanes, boats and cars very popular.


Napier began at the beginning of the First World War to build aircraft engines other companies under license. However, Napier was not satisfied with the strange constructions and decided in 1916 to design its own motor. It should be a distinctive high-performance engine with low weight and high reliability. Thus, a 12-cylinder engine has been constructed which should not be a V-type engine having two cylinder banks but but a Y motor with three. This engine was very advanced, because it had 4 -valve cylinder heads with dual overhead camshafts, which were driven by bevel. Furthermore, it had two spark plugs per cylinder, and the cylinder block was machined from a piece of aluminum.

The engine was called the Lion, and the first prototypes were running in 1917. After the initial difficulties had been overcome, he went in 1918 in production. The first version of Lion -I reached ( even without charging) 450 horsepower from 24 liters capacity. He took over the role of the " most powerful aircraft engine in the world" by the American Liberty L -12, who was also an excellent design with an output of 400 hp.

As the world's most powerful aircraft propulsion (especially supercharged and turbocharged 1922 ), the Lion was a great commercial success. He was practically ubiquitous during the years between the world wars by its great popularity. At this time the Lion drove around 160 different aircraft types. Napier hardly built another, and there was hardly a thought wasted because the Lion replace with a new design. In 1925 the car production was abandoned in favor of motor manufacturing.

In uprated racing versions of the Napier Lion achievements reached up to 1375 hp, so many world records were broken with him, altitude, flight speed, long-haul flights, speeds seas ( 160 km / h in 1933 ) and in the country (Sir Malcolm Campbell's record - cars such as the 400 km / h Bluebird from 1932 and John Cobb's 634 km / h fast Railton Mobil Special 1947). Even the prestigious Schneider Cup of Lion in 1922 and 1927 could help you to victory. 1933 built and drove Hubert Scott - Paine 's Miss Britain III, which was also powered by a Napier Lion and set a world speed record for single-engine boats.

In the 1930s a new generation of larger and more powerful engines such as the Bristol Hercules or the Rolls- Royce Merlin, the repressed the Lion from his place as the strongest engine aircraft appeared.

Napier consequently began to design new engines, including the Cub ( a water-cooled X16 engine with 1000 hp ), which is also 16- zylindrige Rapier ( an air-cooled H- engine with 400 hp) and an additional air-cooled H engine - the 24 - zylindrige Dagger with 1000 hp. Later still, the excellent water cooled H24 engine Sabre, the Nomad and the Deltic and various turboprop engines ( Naiad, Eland ) were added.

Technical data ( Lion VIID, 1929)

  • Type: Water-cooled 12-cylinder engine with supercharging Y
  • Stroke: 130.2 mm ( 5.125 inch)
  • Bore: 139.7 mm (5.5 inch)
  • Displacement: 23.94 liters
  • Compression: 10:1
  • Mass: 438 kg
  • Control: 4 valves per cylinder ( two for intake and two for exhaust); royal shaft-driven, dual, overhead cam (DOHC )
  • Cooling: water
  • Power: 1320 hp ( 970 kW) at a speed of 3500 rpm
  • Specific power: 55 HP / liter ( 41 kW / liter)
  • Power to weight ratio: 0.33 kg / hp (0.45 kg / kW)