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Liberty engine

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Liberty engine

See also Liberty L-8 for the eight-cylinder prototype
Liberty L-12
Liberty L-12 aircraft engine
Type Piston aero engine
National origin United States
Manufacturer Ford, Packard, Marmon, Buick
Designed by Jesse G. Vincent and Elbert J. Hall
First run about 1917
Number built 20,748
Variants Liberty L-4, Liberty L-6, Liberty L-8

The Liberty L-12 was a 27-litre (1,649 cubic inch) water-cooled 45° V-12 aircraft engine of 400 horsepower (300 kilowatts) designed both for a high power-to-weight ratio and for ease of mass production.


In May 1917, one month after the US had declared war on Germany, a Federal task force known as the Aircraft Production Board summoned top engine designers Jesse G. Vincent (of the Packard Motor Car Company of Detroit) and E.J. Hall (of the Hall-Scott Motor Co. of Berkeley, California) to Washington D.C. They were given the task of designing as rapidly as possible an aircraft engine that would rival if not surpass those of Great Britain, France, and Germany. The Board specified that the engine would have a high power-to-weight ratio and be adaptable to mass production. The Board brought Vincent and Hall together on 29 May 1917 at the Willard Hotel in Washington, where the two were asked to stay until they produced a set of basic drawings. After just five days, Vincent and Hall left the Willard with a completed design for the new engine.[1]

In July 1917, an eight-cylinder prototype assembled by Packard's Detroit plant arrived in Washington for testing, and in August, the 12-cylinder version was tested and approved. That fall, the War Department placed an order for 22,500 Liberty engines, dividing the contract between the automobile and engine manufacturers Buick, Ford, Cadillac, Lincoln, Marmon, and Packard. Hall-Scott in California was considered too small to receive a production order. Manufacturing by multiple different factories was facilitated by its modular design.[2] Cadillac was asked to produce Liberty engines but William Durant was a pacifist who did not want General Motors facilities to be used for producing war material. This led to Henry Leland leaving Cadillac to form the Lincoln company to make Liberty engines. However, Durant later changed his mind and both Cadillac and Buick produced the engines.[3]

Ford was asked to supply cylinders for the new engine, and rapidly developed an improved technique for cutting and pressing steel which resulted in cylinder production rising from 151 per day to over 2,000, Ford eventually manufacturing all 433,826 cylinders produced, and 3,950 complete engines.[4] Lincoln constructed a new plant in record time, devoted entirely to Liberty engine production, and assembled 2,000 engines in 12 months. By the time of the Armistice with Germany, the various companies had produced 13,574 Liberty engines, attaining a production rate of 150 engines per day. Production continued after the war, for a total of 20,478 engines built between July 4, 1917 and 1919.[5]

Lincoln production

As the United States entered World War I, the Cadillac division of General Motors was asked to produce the new Liberty aircraft engine, but William C. Durant was a pacifist who did not want General Motors or Cadillac facilities to be used for producing war material. This led to Henry Leland leaving Cadillac to form the Lincoln Motor Company to make Liberty engines. He quickly gained a $10,000,000 government contract to build 6,000 engines.[6] Subsequently the order was increased to 9000 units, with the option to produce 8000 more if the government needed them.[7] Other manufacturers in the program included Packard, Ford and Marmon. Lincoln had delivered 6500 of the 400 hp, V-12, overhead camshaft engines when production ceased in January 1919.[8] Although it is widely reported otherwise, a few Liberty engines did see action in France as power for the American version of the DeHaviland DH4.[9]


The Liberty L-12 was a modular design where four or six cylinders could be used in one or two banks. A single overhead camshaft for each cylinder bank operated two valves per cylinder, in an almost identical manner to the inline six-cylinder German Mercedes D.III and BMW III engines, and with each camshaft driven by a vertical driveshaft that was placed at the back of each cylinder bank, again identical to the Mercedes and BMW straight-six powerplants. Dry weight was 844 lb (383 kg). Fifty-two examples of a six-cylinder version, the Liberty L-6, which very closely resembled the Mercedes and BMW powerplants in overall appearance, were produced but not procured by the Army. A pair of the 52 engines produced were destroyed by Dr. William Christmas testing his so-called "Christmas Bullet" fighter.



An inverted Liberty 12-A was referred to as the V-1650 and was produced up to 1926 by Packard — exactly the same designation was later applied, due to identical displacement, to the World War II Packard-built version of the Rolls-Royce Merlin.[10]

Nuffield Liberty

The Nuffield Liberty tank engine was produced in World War II by the UK car manufacturer Nuffield. It was a 27 L (1,649 in3) engine with an output of 340 hp (250 kW), which became inadequate for the increasing vehicle weights as the war progressed, and it suffered numerous problems with cooling and reliability.[11] It was replaced in later British tanks by the Rolls-Royce Meteor, based on their Merlin aero engine.

Allison VG-1410

The Allison VG-1410 was an air-cooled inverted Liberty L-12, with a geared super-charger and Allison epicyclic propeller reduction gear and reduced displacement.[12] (458"x7"=1,411 cuin)

Liberty L-6

A 6-cylinder version of the Liberty L-12, and nicknamed the "Liberty Six":- a single bank of cylinders, with the resulting engine bearing a strong external resemblance to both the Mercedes D.III and BMW III straight-six German aviation engines of World War I.

Liberty L-8

An 8-cylinder V engine using Liberty cylinders in banks of four at 90°.


Tank applications

  • Tank Mark VIII, also known as the "Anglo-American" or Liberty World War I tank
  • BT-2 & BT-5 Soviet interwar tank (at least one reconditioned Liberty was installed in a BT-5)
  • Cruiser Mk III, British World War II tank - Nuffield Liberty Mk I
  • Cruiser Mk IV British World War II tank
  • Crusader tank British World War II tank - Nuffield Liberty Mk III or Mk IV
  • Centaur Tank, an early version of the Cromwell British World War II Tank

Anglo-American or Liberty Tank

The Anglo-American or Liberty Mark VIII tank was designed in 1917-18. The American version used an adaption of the Liberty V-12 engine of 300 hp (220 kW), designed to use cast iron cylinders rather than drawn steel ones. 100 tanks were manufactured at the Rock Island Arsenal in 1919-20, too late for World War I. They were eventually sold to Canada for training in 1940, except for two that have been preserved.


Specifications (Liberty L-12)

Data from Janes's All the world's Aircraft 1919[14]

General characteristics

  • Type: 12-cylinder liquid-cooled Vee piston aircraft engine
  • Bore: 5 in (127 mm)
  • Stroke: 7 in (178 mm)
  • Displacement: 1,649.3 in3 (27.03 L)
  • Length: 67.375 in (1,711 mm)
  • Width: 27 in (685.80 mm)
  • Height: 41.5 in (1,054.10 mm)
  • Dry weight: 845 lb (383.3 kg)


  • Valvetrain: One intake and one exhaust valves per cylinder operated via a single overhead camshaft per cylinder bank
  • Fuel system: Two duplex Zenith carburettors
  • Fuel type: Gasoline
  • Oil system: forced feed, rotary gear pressure and scavenge pumps, wet sump.
  • Cooling system: Water-cooled


  • Power output: 449 hp (334.8 kW) at 2,000 rpm (takeoff)
  • Specific power: 0.27 hp/cu in (12.4 kW/L)
  • Compression ratio: 5.4:1 (Army engines) 5:1 (navy engines)
  • Specific fuel consumption: 0.565 pt/hp/hour (0.43 l/kW/hour)
  • Oil consumption: 0.0199 pt/hp/hour (0.0152 l/kW/hour)
  • Power-to-weight ratio: 0.53 hp/lb (0.87 kW/kg)

See also

Comparable engines
Related lists



  • Bradford, Francis H. Hall-Scott: The Untold Story of a Great American Engine Manufacturer
  • Angelucci, Enzo. The Rand McNally Encyclopedia of Military Aircraft, 1914-1980. San Diego, California: The Military Press, 1983. ISBN 0-517-41021-4.
  • Barker, Ronald and Anthony Harding. Automotive Design: Twelve Great Designers and Their Work. SAE, 1992. ISBN 1-56091-210-3.
  • Leland, Mrs. Wilfred C. and Minnie Dubbs Millbrook. Master of Precision: Henry M. Leland. Detroit, Michigan: Wayne State University Press, 1996. ISBN 0-8143-2665-X.
  • Lewis, David L. 100 Years of Ford. Lincolnwood, Illinois: Publications International. 2005. ISBN 0-7853-7988-6.
  • "Lincolns." Lincoln Anonymous. Retrieved: August 22, 2006.
  • Vincent, J.G. The Liberty Aircraft Engine. Washington, D.C.: Society of Automotive Engineers, 1919.
  • Weiss, H. Eugene. Chrysler, Ford, Durant and Sloan: Founding Giants of the American Automotive Industry. Jefferson, North Carolina: McFarland & Company, 2003. ISBN 0-7864-1611-4.

External links

  • Contemporary technical description of the engine with drawings and photographs.
  • Recovery of a Liberty powered tank
  • Annals of Flight
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