Aviation Engines

Allison

The Allison Engineering Company was a large and well-established precision engineering shop, formed basically to build and support racing cars competing on the Indianapolis speedway. It had little in the way of regular production sales, although it did produce a range of precision steel-backed lead-bronze bearings and a range of gears for high-power engines. Experience of marine engine building and conversion of the Liberty engine to designs from the Army and Navy had given Allison a background for it to be awarded a Navy contract for a two-stroke diesel airship engine, trials of which were successful although the engine was not subsequently used.

Other contracts were pursued, but the position of Curtiss as the Army and Navy preferred engine builder prevented Allison from getting further work. After the death of James Allison in 1929, the company was bought by the Fisher Brothers Investment Corporation, and on the instructions of Lawrence P. Fisher, Allison's then general manager N.H. Gilman designed a small six-cylinder liquid cooled engine using a cylinder design that the company had worked on the previous year while pursuing Army contracts. The engine was continued with later in the year when Fisher Brothers sold Allison to General Motors. The depression of 1929-1933 forced the project to be dropped, but Gilman had also sketched out a larger 12-cylinder engine which was aimed at a far higher output of 750hp, quite high for that period.

Gilman wanted to use turbo-supercharging in this engine, which lent itself well to this form of output boosting as it was liquid-cooled. GM were sceptical about the whole project, as both Wright and P&W were in full production of air-cooled radials which were the current preferred engine of both the Army and Navy. Gilman persisted, and GM allowed him to proceed with what was to become the V-1710 engine, the only engine that Allison were to be associated with.

Allison V1710-F Type Aero Engine

Allison V1710-F Type Aero Engine

The Army refused to have anything to do with the Allison design, as it believed that the Curtiss successor, Curtiss-Wright Corpn., would continue with development of the Curtiss liquid-cooled engines, and an improved design would ultimately be forthcoming. It also doubted whether Allison had the resources to develop a high-powered engine in this class. Other considerations were the need, felt by Army engineers, for individual cylinders taher than a monobloc construction, this leading on to the development of the Continental engine.

Allison were asked to contact the Navy, who were working with the Hall Aluminium Aircraft Co on a flying boat, the XP2H-1. The Navy did talk with Allison on this project, but another angle was to emerge during these talks, that of the power units for airships. The Navy wanted an all-american engine available to replace the German Maybach power plants being used at the time. It gave Allison a contract for a single V1710-A engine, to develop 650hp at sea level. Ultimately, the airship engine supply position was not to materialise as the Macon was lost on the 12th February 1935, and with it went the Navy's airship programme.

Allison V1710-C15 Type Aero Engine

Allison V1710-C15 Type Aero Engine

The Army meanwhile were hedging their bets, as Continental were taking a long time to develop their new engine, and wanted to ensure that they had a 1000hp engine available, if possible before the Continental engine was ready. They ordered a V1710-C1 engine in 1932, and in 1934 it passed its 50-hour test at 800hp @ 2400rpm. In March 1934, the Army ordered another V1710 for testing, followed by ten engines, two with carburettors and eight with Marvel fuel injectors. General Motors saw that there was going to be some potential in the engine, and started to put substantial money behind the division. A further test at the Army's instigation in 1935 saw 1000hp on a 50-hour test, although a full type-test was not completed due to the different conditions used for the tests.

Allison V1710-C15 Type Aero Engine

Allison V1710-C 15 Type Aero Engine Rear View

A new engineer, R.M. Hazen was then put in charge of the engine development, and the output began to rise, with over 140 hours of the type test passed at 1000hp in the sedcond half of 1936, and the V1710-C8 passed its full type test at 1000hp @ 2600rpm in March 1937. The weight of the engine was 1230 lbs.The Rolls-Royce Merlin at the same time was passing its own tests at 990 hp @ 2600rpm for a weight of 1335 lbs.

Allison V1710 Aero Engine Crankshaft & Pistons

Allison V1710 Aero Engine Crankshaft & Pistons

GM only recovered its investment after the start of volume production, although the actual amount put into the V1710 was still less than half that which P&W put into the R-2800 before it went into production.

Following successful trials in the Curtiss P-36 Hawk fighter, the Allison was also fitted to the XP-38 Lockheed Lightning and the Bell XP-39 Airacobra. Orders from the Government in 1939 for over 1000 engines made the V1710 the largest-selling engine of that period, and the largest engine order placed by the Govt to date. Over 6000 engines were delivered by the end of 1941, with larger quantities to come in the later war years.

Allison V1710 Aero Engine Sectional Views

Allison V1710 Aero Engine Sectional Views


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