Anzani 3-cylinder

Anzani 3-cylinder
72° Anzani fan engine, Shuttleworth Collection
Type	Three-cylinder air-cooled
National origin	France
Manufacturer	Anzani
Designed by	Alessandro Anzani
Major applications	Blériot XI

From 1905 to 1915, Alessandro Anzani built a number of three-cylinder fan and radial engines, one of which powered Louis Blériot's 1909 cross-channel flight. An Anzani three-cylinder engine that powers a Blériot XI based in England is thought to be the oldest airworthy engine in the world.

Alessandro Anzani began building motorcycle engines in France around 1905. Unusually, his motors were air- rather than water-cooled, making them light. His first designs were two-cylinder V-engines, and he rode machines powered by them to records and race success in 1905 and 1906. In the same period he had developed a three-cylinder version, more powerful than the twins. As the image shows, the engine fitted neatly into the cycle frame. Engines with cylinders arranged radially but only in the upper half-circle were termed fan type, or semi-radials; by about 1910 other manufacturers were building e.g. five-cylinder fan engines, most notably R.E.P. Three-cylinder fans were alternatively known as W or W-3 engines. The appeal of the fan configuration was that, because all the cylinder were above the horizontal there was little danger of the plugs being fouled by the lubricating oil. The disadvantage, particularly for an aircraft engine, was the extra weight required to counterbalance the pistons.

In response to the growing interest in aviation in France after the Wright brothers' visit in 1908, Anzani produced the first of a series of three-cylinder fan flight engines. The cylinders were each a single iron casting and the one-piece crankcase was aluminium. Pistons were steel with cast rings. In most of these the outer cylinders were at 60° to the central one, though a contemporary diagram shows one, described as the cross channel engine, with a 55° angle. They were all air-cooled side-valve engines; each exhaust valve was controlled from below by a cam in the crankcase. Each was mounted in a cell to the side of the cylinder, with the automatic, atmospheric pressure -driven spring-loaded inlet valve immediately above it, partly to minimise volume and partly to help cool the hot exhaust valve. Most contemporary and pre-1921 sources agree that the bores of these early engines were between 100 and 105 mm (3.93 and 4.13 in), but strokes between 120 and 150 mm (4.72 and 5.90 in) are quoted. Most put the output of these engines at about 18 kW (24 hp) at around 1,400–1,600 rpm.

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