Ford GAA engine

Development

After the start of World War II, the UK was looking to manufacture complicated parts — notably the crankshafts — of the Rolls-Royce Merlin aircraft engine in the United States, but negotiations with Packard stalled because the company insisted on making complete engines. In June 1940 production drawings arrived in North America and were seized by the United States Department of the Treasury, providing an opportunity for Ford engineers to copy them and soon derive a version simplified for mass-production at Ford's factories. However, the prior text, provided without citation, is misleading and may be false. Ford was asked by the British Government to produce true Merlin engines, not a revised mass production version as the prior text claims, at their factories in England, and delivered 30,400 bomber engine variants of the Merlin by war's end. However, Henry Ford balked at producing the Merlin in Detroit and instead preferred to produce a fresh design, with the ambitious goal of 2000 hp. Although this design had the same bore and stroke as the Merlin, it shared no parts in common and differed substantially in several fundamental ways, such as having four overhead cams instead of the Merlin's two. This engine, called the XV-1650, was never produced, however, because the US Navy had no interest in water cooled engines in that power range and the US Army was obliged and loyal to Allison at the moment, and because of Henry Ford's tainted pre-war cooperation with Germany (Sources: Graham White, Allied Piston Aircraft Engines of World War II, 1995, and Herschel Smith, A History of Aircraft Piston Engines, 1981).

It was a 60 degree V-12 of 1,650 cubic inch displacement, with the cylinder bore and stroke matching the Merlin, using an aluminum block and head; dual overhead camshafts, and four valves per cylinder. The intention of this design was to help Ford break into the anticipated large market for aircraft engines. This engine was built to typical aircraft standards: it was light, high performance, and highly reliable. Everything was safety-wired or staked, with close attention to detail on every part. Available information suggests this design performed well.

However, it never went into production as an aircraft engine due to the United States Navy's decision to only use radial engines for its aircraft and the Army's contractual commitments to existing manufacturers.

With the approach of war, increasing orders for M4 Sherman tanks were causing supply issues with the 9-cylinder radial Wright R-975 Whirlwind engine used. The U.S. Army decided it needed to establish additional engine suppliers, choosing a version of the Ford GAA cut down from twelve cylinders to eight for various vehicle applications.

In 1942 after the British Tank Mission visit to America in April, there was some pressure from British car and commercial vehicle manufacturers to use the new Ford V8 tank engine designed by Larry Sheldrick in British tanks, rather than the Meteor then under development by Rolls-Royce from the Merlin aero engine, as they believed that an adapted aero engine "would not be suitable as a rugged tank engine". The Ford engine prototype had a few hundred hours test-bed running by that time. It was a liquid-cooled Vee similar to the Meteor, but two-thirds the size and Rolls-Royce executive W. A. Robotham doubted its reliability at 600 bhp. The 600 bhp Meteor was designed to fit in the same space in the Crusader tank as the Nuffield Liberty L-12 engine of 340 bhp output. The Ford V8 developed only 500 bhp, and had problems that were not overcome until after the Normandy landings in 1944.

Production

• The GAA was used in the M4A3 (1,690), M4A3(75)W (3,071), M4A3(76)W (1,400), M4A3 (105) (500), M4A3E2 (254), M4A3(76)W HVSS (3,142), M4A3(105) HVSS (2,539), M10A1 (1,413), and M7B1 (826).
• The GAF powered the M26 (2,222), M26A1, T28/T95 (2), and M45 (185).
• The GAN powered the T23 (248) and M4A3E2 (254).
• In order to meet the need for a larger engine, Ford resurrected the V-12 version as the GAC, which produced 770 hp and powered the T29, and T32 (6).
• A number of M74 armored recovery vehicles were rebuilt from M4A3s, which used the GAA.

Notes

References

• Berndt, Thomas. Standard Catalog of U.S. Military Vehicles. Iola, WI: Krause Publications, 1993. .
• Aircraft Engine Historical Society.Aircraft Engines in Armored Vehicles
• Hunnicutt, R. P. Firepower: A History of the American Heavy Tank. Novato, California: Presidio Press, 1988.

References

1. Berndt, Thomas. ''Standard Catalog of U.S. Military Vehicles'' (Krause Publications, 1993), p.193.
2. Berndt, p.190.
3. Berndt, pp.190 & 193.
4. Berndt, p.193.