Liberty (engine)
_USAF.jpg)
The Liberty ( English for freedom ) was an American aircraft engine that was developed during the First World War and built in 1917. The engine, which in the end - instead of the planned four-cylinder banks - was mass-produced with only six-cylinder banks in one version as a 45 ° -V12 under the name Liberty L-12 , developed around 400 HP (294 kW), which was an enormous value at the time depicted. There was also a hanging cylinder version called the Liberty L-12A or, for military use, the Packard V-1650 . The Liberty was considered a successful design and was trend-setting for many aircraft engines of the 1920s and 1930s.
history
prehistory
This aircraft engine was developed by Jesse G. Vincent , chief designer of Packard Motor Car Co. , and Elbert J. Hall , one of the two chiefs of the Hall-Scott Motor Car Company , on behalf of the government. From the outset, a complete engine series with 4- and 6 - cylinder in - line engines as well as 8- and 12- cylinder V-engines was planned in order to counter the existing performance deficit of the previous US-American engines and not only to use imported aircraft engines from Europe such as being instructed by Renault or Sunbeam .
development
The engines were named Liberty L-4 , Liberty L-6 , Liberty L-8 and Liberty L-12 . According to official information, the engine was designed within six days. The Liberty aircraft engine is one of the first modular engines and has been optimized from the outset for the most efficient production possible. So two four- cylinder banks or cylinder heads could be used for a V8 engine, correspondingly two six-cylinder banks and cylinder heads resulted in a V12 engine. A special feature of the Liberty V engines was the relatively narrow cylinder angle of 45 °, which was chosen in order to keep the dimensions of the engine more compact and thus to reduce the frontal area and thus the aerodynamic drag of the aircraft to be propelled . In order to achieve high engine output as required, were based on the construction of racing car an overhead engines cam shaft ( overhead camshaft ), light metal - piston , water cooling and a hemispherical combustion chamber is provided. The cylinder bore and stroke were uniformly 127 mm (5 in ) × 178 mm (7 in) in all versions , the displacement per cylinder was 2253 cm³ (137.49 in³ ), an overhead camshaft for each cylinder bank actuated two valves per cylinder. The total cubic capacity of the individual versions was 9013 cm³ (549.94 in³) for the L-4 , 13,519 cm³ (824.92 in³) for the L-6 , 18,026 cm³ (1099.89 in³) for the L-8 and 27,039 cm³ (1649, 86 in³) for the L-12 . The take-off power of the L-12 was given as 448 PS (330 kW) at 2000 rpm, the climb performance at 400 PS (294 kW) at 1700 rpm and the continuous power in cruise at 340 PS (250 kW) at 1400 rpm. With these performance values, the Liberty L-12 was one of the most powerful aircraft engines of that time.
In 1919, a Packard - Lepère -Doppeldecker with a turbocharged engine Liberty with a height of 28,500 ft (about 8690 m ) to a new world altitude record for airplanes.
Series production of the L-12
The first prototype , a V8, was put to the test on July 3, 1917 . The performance data were so convincing that production of initially 100 V8 engines was ordered immediately. However, it was soon recognized that the 8-cylinder variant would not be able to meet the performance requirements for long, mainly because of the increased weight of the newer aircraft, so the US Congress soon approved $ 240 million for the production of 45,250 V12 engines at Packard , Ford , Marmon , Buick , Cadillac , Lincoln and Marmon , a subsidiary of the mill builder Nordyke Marmon & Company . Until production of the Liberty L-12 was discontinued in 1919, which was ultimately the only mass-produced version, 20,478 of these engines had been built, 6000 of which were installed in aircraft. The remaining engines were initially intended as spare parts and were sold after the war.
Use after 1919
Numerous redundant Liberty L-12s then went on sale and were often used in civil aviation or in motorsport .
However, production of the engine continued in Europe after Great Britain had acquired a license for the L-12 and manufactured it as a tank engine at Nuffield as Nuffield Liberty until 1943 .
Variant L-12A (Packard V-1650)
A variant of the V12 engine with the crankshaft positioned upwards and hanging cylinders was called the Packard V-1650 or, for civilian use, the Liberty L-12A (also called Liberty 12-A in the literature ) and was built until 1926.
Exactly the same name Packard V-1650 was used again during the Second World War from 1941 on the British aircraft engine Rolls-Royce Merlin, which was again built under license by Packard as Packard V-1650 due to the identical displacement configuration of 1650 in³ (27.038.66 cm³) standing cylinders are used.
variants
With standing cylinders
- Liberty L-4 - 4-cylinder in-line engine, not built in series
- Liberty L-6 - 6-cylinder in-line engine, only three engines made
- Liberty L-8 - 8-cylinder V-engine, only produced in small series of 100 engines
- Liberty L-12 - 12-cylinder V-engine, main production version, a total of 20,478 manufactured
With hanging cylinders
- Liberty L-12A or Packard V-1650 - Packard- made version of the L-12 with hanging cylinders
Applications
Liberty L-6
The only three built six-cylinder in-line Liberty L-6 engines were not adopted by the Army Air Corps, but by the designer Dr. William Christmas used for test flights of his " Christmas Bullet " called hapless (and therefore not mass-produced) hunting machine, whereby two of the six-cylinder in-line engines were destroyed when this test machine crashed.
Liberty L-8
The approximately 100 built eight-cylinder Liberty L-8 engines were mainly installed and tested in De Havilland DH4 and other machines, but these proved to be insufficiently powerful and were replaced by the L-12 .
Liberty L-12
The North American made De Havilland DH4, Douglas M-2 and the Curtiss Falcon were equipped with Liberty L-12 engines . The first Atlantic flight was carried out with a Curtiss NC , which was also equipped with Liberty L-12 engines.
In addition, many Liberty V12 engines were used for marine use in racing boats after the First World War . The engine was still installed in the “Centaur” medium tank during World War II because Rolls-Royce was unable to deliver its 600-hp Meteor engine in sufficient numbers.
Packard V-1650
The Packard V-1650 version with hanging cylinders was used, for example, in the Loening OL amphibious aircraft .
License versions
- Great Britain : Licensed construction as Nuffield Liberty , used as a tank engine , but the engine turned out to be not powerful enough for this purpose, except for light tanks, and also not always reliable.
- USSR : Licensed construction from 1924 to 1932 as M-5 in Moscow Plant No. 24 in 2725 copies, used as a flight and tank engine mainly in the multi-purpose R-1 aircraft .
Technical specifications
Liberty L-12 (production version)
- Type: four-stroke gasoline engine
- Cooling: water, forced circulation
- Cylinder arrangement: V12, cylinder angle 45 °
- Valve control : one overhead camshaft per cylinder bank (OHC)
- Valves: two per cylinder
- Displacement: 27,038.66 cm³
- Bore: 127 mm
- Stroke: 178 mm
- Power:
- Continuous output: 340 hp at 1400 rpm
- Climbing power: 408 hp at 1700 rpm
- Take-off power: 448 hp at 2000 rpm
- Power-to-weight ratio : 0.87 kW / kg (0.53 hp / lb)
- Weight (dry): 383 kg
Liberty L-8 (100 copies only)
- Type: four-stroke gasoline engine
- Cooling: water, forced circulation
- Cylinder arrangement: V8, cylinder angle 45 °
- Valve control : one overhead camshaft per cylinder bank (OHC)
- Valves: two per cylinder
- Displacement: 18,009 cm³ (18 l or 1099 in³)
- Bore: 127 mm
- Stroke: 178 mm
- Power:
- Continuous power:?
- Climb rate:?
- Take-off power: 290 hp at 1700 rpm
- Power-to-weight ratio: 1 kg / hp
- Weight (dry): 290 kg (638 lb)
See also
- Packard V-1650 (licensed by the British Rolls-Royce Merlin)
- List of aircraft engines
- Liberty Truck
Web links
Individual evidence
- ↑ turbolader.net: The history of the turbocharger . Retrieved June 17, 2012
- ↑ Ulf Gerber: The great book of Soviet aviation 1920–1990. Development, production and use of the aircraft. Rockstuhl, Bad Langensalza 2019, ISBN 978-3-95966-403-5 , p. 349