By: Norm Goyer
The Liberty V-12 liquid cooled engine was designed in 1917 by a group of American auto manufacturers. It was the first engine designed for mass production methods for aircraft engines.
Our thanks to Wikipedia for the facts about the Liberty, NG
There is little doubt that one of sweetest sounds in the field of aviation is the roar of a Mustang with a Packard V-12 Merlin, swinging a four-bladed prop, roaring over the field in a low level pass. Almost as good as you know what. The Merlin dominated the air battles of Europe during World War II. An almost twin, the Rolls Royce Merlin, was right alongside propelling Spitfires, Hurricanes and Mosquitoes. Lockheed P-38 Lightings, Curtiss P-40 Warhawks and Bell Airacobras were using a another sibling, the Allison V-12. The only hold out opting for a radial air-cooled engine was the outstanding Republic P-47 Thunderbolt. It’s Pratt & Whitney twin row R-2800-59 radial engine was one of the most dependable engines of the entire war. The Allies most capable foe was the German Messerschmitt Bf.109, you guessed it with a V-12 liquid cooled Daimler-Benz DB 605A-1 very similar to the Merlins. In fact Spain used Rolls Merlins in their post war fleet of Bf.109s, an almost direct swap. It would be hard to find another engine that seemed built for the aircraft of World War II. Unfortunately that would be incorrect.
The engine was installed in a Douglas DT torpedo bomber. The Liberty produced about 400-hp.
The mighty Merlin, Allison and Rolls owe their heritage not to World War II but to World War I, that’s right, 1917, was the year it all started. With America about to enter the war it was deemed necessary for America not to produce fighting planes, but to mass produce engines to power the coming larger aircraft. England and France both said that they had the capability of building the airplanes, but desperately needed larger dependable engines. America had many firms capable of building engines, unfortunately automobile engines, and not airplane engines. A new design was needed, one that was capable of being mass produced, and versatile enough to produce different sizes, using the same components. Auto engines use mostly a cast iron block with the cylinder holes bored after the block was cast. In other words, four, 6, 8 and 12 cylinder car engines have no interchangeable main parts other than pistons, rods and other smaller components. The British SE.5, German Albatros and Fokker D-VII used automobile engines from Hispano-Suiza, , Mercedes and BMW. An engine designed just for aircraft was needed as fast as possible.
The Liberty was also used in the four-engine Curtiss NC-4 aircraft that was first to fly the Atlantic. Shown is the first NC, which only had three Liberty engines.
A group of auto makers including Packard, Hall-Scott, Buick, Ford, Cadillac and Marmon were asked to design and produce a new series of engines. All signed on but Cadillac who opted out as the company did not want to produce weapons of war. That prompted their designer to bail out and form the Lincoln Automobile company and promptly joined the group. The resulting 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 a similar manner to the inline six-cylinder German Mercedes engine. Dry weight was 844 lb. 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. An inverted Liberty 12-A was referred to as the V-1650 and was produced up to 1926 by Packard the exact same designation was later applied, due to identical displacement, to the World War II Packard-built Rolls-Royce Merlin. 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 capacity.
The Packard Merlin V-1650 which was installed in the famous P-51 Mustang was a direct descendent of the Liberty V-12 engine.
The Liberty started the trend which dictated that aircraft engine cylinders should be individually bolted to the crankcase for easy replacement. The Liberty engine had a great reputation and was installed in the Curtiss NC series of seaplane which were the first to fly across the Atlantic Ocean. Liberty engines were also installed in the Douglas DT bomber, and the Douglas Mail Plane. Another great accomplishment due to the needs of war.
Technical:
- Type: 12-cylinder liquid-cooled V piston aircraft engine
- Bore: 5 in
- Stroke: 7 in
- Displacement: 1,649.3 in³
- Dry weight: 845 lb
Components
- Valve train: One intake and one exhaust valves per cylinder operated via a single overhead camshaft per cylinder bank
- Cooling system: Liquid-cooled
Performance
- Power output: 449 hp at 2,000 rpm (takeoff)
- Specific power: 0.27 hp/in³
- Power-to-weight ratio: 0.53 hp/lb