Anzani 10-cylinder - Design and Development

Design and Development

In the first decade of the 20th century Anzani developed his upright 3-cylinder 'W' type motorcycle engine, which powered Bleriot's successful Channel crossing flight of 1909, into a three-cylinder symmetric or 'Y' radial, and from that to a 6-cylinder double-row radial engine.

By 1912 he had built the Anzani 10, a 10-cylinder engine, air-cooled like its predecessors, which, like other Anzani engines, was made with different size cylinders. One of the more powerful versions produced about 110 hp (82 kW) from 12.1 litres, a British-built Anzani 10 was rated at 125 hp and a smaller version with a displacement of 8.27 litres produced 80 hp (60 kW). It was a double row engine, built with two rows of five cylinders separated along the crankshaft by about a cylinder radius, giving the engine a slimmer profile than other contemporary two-row radial engines. Each half had its own crankpin, 180° apart, with the connecting rods,of chrome nickel steel, broad and flat to bring the two halves close together. Cylinder heads and pistons were made of cast iron, the latter machined inside and out and fitted with a pair of rings. Oil was forced through the crankshaft to the crankpins, then moved under centrifugal force to the cylinders and pistons from inside the crankcase which was a single light alloy casting.

Both inlet and exhaust valves were in the cylinder heads. The automatic inlet valves of earlier Anzani engines, opened by atmospheric pressure and closed by valve springs were retained, but fuel was fed from a mixing chamber in the crankcase via inlet tubes placed at the rear of the engine to avoid cooling of the mixture by the oncoming airflow. This arrangement placed the exhaust valves at the front of the engine, where they were operated from a cam in the rear of the crankcase via push rods and rockers. A single carburettor fed the crankcase chambers from below. Some versions used a single Gibaud magneto, running at 3,000 rpm, though others built by British Anzani had a pair of Bosch magnetos, running slower. Plugs (K.L.G. for the British variant) were mounted in the sides of the cylinder heads, sloping upwards to avoid plug fouling by lubricating oil. The exhaust was collected by a prominent pair of semi-circular rings.