Anzani Fan / W / W-3
Anzani Military Model Fan (W-) type
Alessandro Anzani began building motorcycle engines in France around 1905. His motors were air-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. 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 diagramshows 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.
It was an engine of this sort that famously powered Louis Blériot's Type XI monoplane across La Manche (the English Channel) on 25 July 1909. Contemporary sources differ on its bore, stroke and swept volume. The first description of the successful machine in Flight describes the engine as having dimensions of 100 × 150 mm, or a capacity of 3.53 litres. However, a few months later they printed the engineering drawing of the 55° engine, which has dimensions of 103 x 120 mm marked on it, clearly captioned as "used ... in the cross-Channel flight". If their identification was right, then Bleriot used a 3.00-litre engine. A head-on photograph of the cross-channel aircraft also shows a 55° engine.
Even before the channel flight, Anzani was selling more powerful versions with larger bores: a 120 mm bore, 4.4-litre (269 cu in) variant produced 26 kW (35 hp) and a 135 mm bore, 6.4-litre (390 cu in) engine gave 36 kW (45 hp). These fan engines remained in production until at least 1913, though there were important improvements. The exhaust valve was moved to the cylinder head and operated by rockers via push rods, and a mixing chamber was arranged in the crankcase. The 1913 three-cylinder Anzani fan engine had a cylinder separation of 72°, presumably to lighten the counterbalance. By this stage it had its inlet manifold at the rear of the engine to minimise airflow cooling of the fuel air mixture.
Anzani 3-cylinder fan engines
10-12 hp (7.5-9 kW)
Bore x Stroke: 3.35 in × 3.35 in (85 mm × 85 mm)
Capacity: 88.5 cu in (1.45 lt)
12-15 hp (9-11 kW)
Bore x Stroke: 3.35 in × 3.94 in (85 mm × 100 mm)
Capacity: 104 cu in (1.70 lt)
25-30 hp (19-23 kW)
Bore x Stroke: 4.13 in × 5.12 in (105 mm × 130 mm)
Capacity: 206 cu in (3.38 lt)
40-45 hp (30-34 kW)
Bore x Stroke: 5.32 in × 5.92 in (135 mm × 150 mm)
Capacity: 393 cu in (6.44 lt)
45-50 hp (34-38 kW)