Liberty L-12

Liberty L-12
Liberty L-12 aircraft engine
Type	Piston aero engine
National origin	United States
Manufacturer	Lincoln, 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 an American 27-litre (1,649 cubic inch) water-cooled 45° V-12 aircraft engine of 400 hp (300 kW) designed for a high power-to-weight ratio and ease of mass production. It was succeeded by the Packard 1A-2500.

Development

Ford Liberty 12

Details of the later pattern SOHC Mercedes D.III valvetrain, adopted almost unchanged for the Liberty L-12 and its derivatives

Closeup of a Liberty L-12's valvetrain details, almost matching the later D.IIIa design

In May 1917, a month after the United States had declared war on Germany, a federal task force known as the Aircraft Production Board summoned two top engine designers, Jesse G. Vincent (of the Packard Motor Car Company of Detroit) and Elbert J. Hall (of the Hall-Scott Motor Co. in Berkeley, California), to Washington, D.C. The two left their positions at the Fageol Motors Co., putting an end to the short production of the most luxurious automobile of the period. 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, which had adopted, almost unchanged, the single overhead camshaft and rocker arm valvetrain design of the later Mercedes D.IIIa engines of 1917-18.

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 factories was facilitated by its modular design.

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. 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.

Although it is widely reported otherwise, a few Liberty engines did see action in France as power for the American version of the Airco DH.4.

Lincoln production

Liberty Engine 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. Subsequently the order was increased to 9,000 units, with the option to produce 8,000 more if the government needed them. More than 16,000 Liberty engines were produced during the calendar year 1918. To November 11, 1918, more than 14,000 Liberty engines were produced. Lincoln had delivered 6,500 of the 400 hp, V-12, overhead camshaft engines when production ceased in January 1919. Durant later changed his mind and both Cadillac and Buick produced the engines.

Design

The Liberty engine 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 William Christmas testing his so-called "Christmas Bullet" fighter.

Variants

V-1650

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

Nuffield Liberty

Major Henry H. "Hap" Arnold with the first Liberty V12 engine completed

The Nuffield Liberty tank engine was produced in World War II by the UK car manufacturer Nuffield and it was used in the Crusader and Centaur tanks. It was a 27 L (1,649 in³) engine with an output of 340 hp (250 kW), which was eventually to become inadequate for the increasing vehicle weights as the war progressed, and it suffered numerous problems with cooling and reliability. In later British tanks such as the Cromwell it was replaced by the Rolls-Royce Meteor, an engine based on the Rolls-Royce 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. (4​⁵⁄₈"x7"=1,411 cuin)

Liberty L-6

Main article: Liberty L-6

A 6-cylinder version of the Liberty L-12, nicknamed the "Liberty Six", consisted of 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°. (1099.6 ci / 18.02L)

Applications

• Airco DH.4
• Airco DH.9A
• Breguet 14 B2 L
• Caproni Ca.60
• Curtiss H-16
• Curtiss NC
• Curtiss Carrier Pigeon
• Airco DH.10
• Douglas C-1
• Douglas DT
• Douglas O-2
• Felixstowe F5L
• Fokker T.II
• Handley Page H.P.20
• Witteman-Lewis XNBL
• RN-1 (Zodiac)
• Babs (land speed record car)
• White Triplex (land speed record car)

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.

Survivors

• A 12A is on display at the New England Air Museum at Bradley International Airport in Windsor Locks, Connecticut.
• An operable Liberty V-12 on a static test stand trailer is often run for demonstrations at Old Rhinebeck Aerodrome's weekend airshow events.

Specifications (Liberty L-12)

Data from Janes's All the world's Aircraft 1919

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)

Components

• 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

Performance

• 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

• BMW VI

Related lists

• List of aircraft engines
• List of Ford engines

References

Bibliography

• 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
• Old Rhinebeck Aerodrome's operable Liberty V-12 engine run video