Alessandro Anzani developed the first two-row radial from his earlier 3- cylinder Y engine by merging two onto the same crankshaft with a common crankweb.

By December 1909 Anzani had a 3-cylinder air-cooled true radial engine running, developed from the earlier 3-cylinder fan configuration engines (semi-radials) that had powered Bleriot across the Channel. By about March 1910 he had completed the first two-row radial engine, a 6-cylinder unit made by merging two 3-cylinder units together, one slightly behind the other and at an angle of 60°. The engine therefore had a lot in common with the early 3-cylinder motors: cylinders were a single iron casting with built-in valve cells and ribs, and pistons were steel with cast-iron rings. The early versions were side-valve engines with automatic (atmospheric pressure opened) inlet valves and exhaust valves mechanically operated via cams in the crankcase. By the end of 1912, as with the smaller engines the exhaust valves were moved to the cylinder heads and operated by push-rods and rockers. The exhaust valves were at the front of the engine, with the fuel inlet manifold at the rear. A prominent pair of 150° exhaust tubes were fitted. Plugs were mounted in the cylinder sides, in the plane of the engine and on the upper side to minimise plug fouling by lubricant.

The crankcase was an aluminium casting and in later models contained a fuel mixing chamber. These later versions also used long bolts to attach the cylinders to the crankcase. The engine used a single, kinked crankweb, coupled to slim but broad connecting rods in order to minimise the axial displacement between the two rows. This was less than in more recent double row radials, the rear face of the front row falling on the centre plane of the back row. The engine was not strictly a radial, as the crankweb geometry slightly offset the centres of the two rows, an arrangement best seen from the back of the engine, where the superimposed inlet tubes and push-rods of the later engine highlight the cylinder centre lines. Such an offset between cylinder centre line and crankshaft is often termed désaxé.

The earliest of the 6-cylinder radials had with a bore of 90 mm and stoke of 120 mm giving a displacement of 4.58 litres (280 cu in) and an output of 34 kW (45 hp) at 1,300 rpm. Its weight was 70 kg (154 lbs). A later version produced 45 kW (60 hp) from 6.33 litres (380 cu in).

Variants:

45 hp (34 kW)
Anzani’s first two-row radial developed 34 kW (45 hp) from 4.58 L (230 cu in) displacement.

60 hp (45 kW)
Larger cylinders gave 45 kW (60 hp) at 1,300 rpm from 6.23 L (379 cu in ) displacement.

TNCA Aztatl
A direct copy of the 60 hp 6-cylinder Anzani, produced in Mexico by TNCA (Talleres Nacionales de Construcciones Aeronáuticas – national aviation workshops).

Applications:

Aeromarine EO
Austin Whippet
Caudron Type N
Farman Scout
Perry Beadle T.2
Westland Woodpigeon II

Specifications:

60 hp overhead valve
Type: 6-cylinder double row air-cooled radial
Bore: 105 mm (4.13 in)
Stroke: 120 mm (4.72 in)
Displacement: 6.23 litres (379 cu in )
Dry weight: 91 kg (200 lb)
Valvetrain: automatic inlet valves, mechanical exhaust valves driven by crankcase can operated pushrods and rockers. One inlet, one exhaust per cylinder
Fuel system: carburettor, mixing chamber in crankcase.
Oil system: splash lubricated
Cooling system: air-cooled, finned cylinders
Ignition: single magneto, one plug/cylinder
Power output: 45 kW (60 hp) at 1,300 rpm
Power-to-weight ratio: 0.49 kW/kg (0.30 hp/lb)

Anzani was aware of the weight cost of the counterweight in the fan configuration and by December 1909 he had a symmetric 120° three-cylinder radial engine running. One example was a 3.1 litre (186 cu in) unit producing 22 kW (30 hp) at 1,300 rpm. Although termed the Y engine after its symmetric cylinder arrangement, it ran in an inverted Y position so that the plugs, mounted on the upper in-plane side of the two lower cylinders were less than 30° below the horizontal and less prone to oiling than one serving a piston at 180° from upright. Radials are smoother running than the less symmetric fan engines as well as lower weight but with the low power available from their three cylinders they had limited applications. They led, however, to Anzani’s two-row radial engines, beginning with the 6-cyl radials, two Ys on a common crankshaft.

Applications:
Blériot XI
Caproni-Pensuti triplane
Deperdussin Type A
Sikorsky BIS-2
Perry Beadle T.1

Survivors
The restored and flyable Blériot XI, registry number N60094 at Old Rhinebeck Aerodrome uses one of these Anzani three-cylinder “true radial” engines for its straight-line, short distance “hop” flights. Another Blériot XI, with British registration G-AANG, is allowed to fly similar short ‘hops’ at the Shuttleworth Collection. Its original “fan-type” Anzani three-cylinder engine is thought to be the oldest airworthy aircraft engine in the world. A 1910 Deperdussin monoplane that is also restricted to straight ‘hops’ uses a ‘Y’ type Anzani engine.

Specifications:

Channel flight engine
Type: 3-cylinder air-cooled fan
Bore: 100 mm (3.94 in)
Stroke: 150 mm (5.90 in)
Output: 30 hp
Displacement: 3.53 litres (216 cu in)
Dry weight: 65 kg (143 lb)
Valvetrain: Automatic inlet valves, mechanical exhaust valves driven from three separate cams in crankcase. One inlet, one exhaust per cylinder
Fuel system: Gronville and Arquembourg carburettor, mixing chamber in crankcase.
Oil system: Splash lubrication
Cooling system: Air, ribbed cylinders
Ignition: Battery ignition, one spark plug per cylinder

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 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.

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,[8] 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.

Brownback built a 20hp three-cylinder radial licensed version of the Anzani as the Brownback Tiger Kitten.

Variants:

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)