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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.
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Development
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.
Production
In the fall of 1917, 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
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, with the cylinders designed as individual units, each with their own water jacket.
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.
V-1650
An inverted Liberty 12-A referred to as the V-1650 was produced up to 1926 by Packard.
The same designation was later applied to the Packard V-1650 Merlin, an engine with nearly identical engine displacement. This was a World War II Packard produced version of the Rolls-Royce Merlin, and is not to be confused with the earlier Liberty-based version.
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
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)
Nuffield Liberty
The Nuffield Liberty tank engine was licensed and produced in World War II by the UK car manufacturer Nuffield. It was used in early Cruiser tanks, the Crusader, the Cavalier, and finally 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.
The Nuffield Liberty ran through multiple versions:
Aircraft
The primary use of the Liberty was in aircraft.
The engine was also used in the RN-1 (Zodiac) blimp.
Automobile
Based on aircraft use the engine provided a good power-to-weight ratio. This made it ideal for use in land speed attempt vehicles.
It was selected for two land speed record attempts.
Both attempts set new records, although Babs crashed during a further attempt, resulting in the death of its driver.
Tank
As early as 1917 the Liberty showed good potential for use in tanks as well as aircraft. 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. One hundred 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.
Inter-war, J. Walter Christie combined aircraft engines with new suspension, producing a rapid and highly mobile tank. Using Christie's concept, Russian forces selected and copied the Liberty in the BT-2 & BT-5 Soviet interwar tank (at least one reconditioned Liberty was installed in a BT-5). Demonstration of this tank was witnessed by the British, and Christie's design characteristics were licensed and incorporated into the British A13 design specification.
As World War II loomed, Nuffield, producing British Cruiser tanks, licensed and re-engineered the Liberty for use in the A13 (produced as the Cruiser Mk III) and later Cruiser tanks. In later British tanks it was replaced by the Rolls-Royce Meteor, an engine based on the Rolls-Royce Merlin aero engine, offering greater engine power.
Nuffield Liberty engines were used in the:
Survivors
A number of Liberty engines survive in restored operational and static display vehicles. Displays of the engine itself include:
Specifications (Liberty L-12)
Data from Janes's All the World's Aircraft 1919