Liberty L-12 Aviation Models
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    In May 1917, one month after the United States had declared war on Germany, the Aircraft Production Board requested engine manufacturers to create a latge light-weight aircraft engine for the war effort. The assignment went to Jesse G. Vincent of the Packard Motor Car Company and E. J. Hall of the Hall-Scott Motor Company. An engine design was needed as soon as possible and the two engineers came up with a solution in only five days. The War Department placed an order for 22,500 engines and the order was split up between Buick, Ford, Cadillac, Lincoln, Marmon and Packard.
    The Liberty L-12 was a 400 hp (298 kw) 12-cylinder, water-cooled, V-12 aircraft engine. The crankcase was cast aluminum and split horizontally at the main bearing centerline. The cylinders were forged steel with cooling jackets welded to the cylinders as was common at the time. Each cylinder bank had a single overhead-camshaft that would operate both intake and exhaust valves. The camshaft was driven by vertical rods, driven off the crankshaft, and placed at the back of each cylinder row. It had a 7 bore and 5 stroke and a direct drive to the propeller. It used an automotive Delco ignition system and a Zenith carburetor.
    Production during the war totaled 13,574 engines with continued production after the war for a total production of 20,478 engines. Other versions of the Liberty engine available were the V-8, 6-cylinder inline, and a 4-cylinder inline.

Specifications:
Liberty L-12
Date: 1917
Cylinders: 12
Configuration: Liquid-cooled, Vee
Horsepower: 400-420 hp (298-313 kW)
RPM: 1,800
Bore and Stroke: 5.00 in. (127 mm) x 7.00 in. (179 mm)
Displacement: 1,649 cu. in. (27 liters)
Weight: 845 lbs. (383 kg)

Endnotes:

1. Herschel Smith. A History of Aircraft Piston Engines. Manhattan, Kansas: Sunflower University Press, 1993. 103.
2. Howard Mingos, ed. The Aircraft Year Book for 1929. New York: Aeronautical Chamber of Commerce of America, Inc., 1929. 86.

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© Larry Dwyer. The Aviation History On-Line Museum. All rights reserved.
Created October 12, 2013.