In 1924, to compete with Moto Guzzi and Garelli racing machines, the chief designer Mario Baldi developed a 350 cc single-cylinder engine named "Freccia Celeste", which would grace the most successful racing motorcycles in the next five years. Baldi's design had several original features: the vertical single-cylinder 348 cc (74 x 81mm) engine had bevel-driven double overhead camshafts. Both the camshafts and the valve springs were hermetically enclosed, something unusual at that time. 90° valves were driven directly by the cams, the crankshaft had internal flywheels and the three-speed gearbox was mounted semi-block with the crankcase. Initially the engine developed 24 HP at 5000 rpm and with a compression ratio of 5.5 to 1 exceeded 140 km / h.
The team's riders, including the famed Tazio Nuvolari, scored almost one hundred victories in the 1920s winning the Italian Championship in 1926, 1928 and 1929 and five Nations GP consecutively won at Monza (1925 -29).
In 1925 Nuvolari set speed records at Monza for the 300 km at 125 km / h, for the 400 km at 121 km / h and for the 3 hours, also at 121 km / h.
Not only on the tracks was the marque successful; the six victories at the Circuito de Lario between 1925 and 1930 and the Tour de Italia in 1926 proved that the "Freccia Celeste" was both fast and reliable.
In its final stage of development, power approached 30 HP but even with a four-speed gearbox it was no longer competitive. Consequently Ing. Baldi designed in 1931 another racing engine, a 500cc DOHC single that was an enlarged version of the 350. With 33 HP at 5000 rpm and riden by the likes of Dorino Serafini and Alberto Ascari, Bianchi had success in long distance races (Circuito de Lario 1934/35 and Milano - Taranto 1936) and won the Italian Championship of 1936. However, Bianchi was finding it difficult to compete with the contemporary Nortons and Guzzi twins.
The appearance of the Gilera 4 Rondine in 1935 prompted Bianchi to entrust Baldi with the design of a four cylinder supercharged 500 cc DOHC. Unlike its rivals (Gilera and Benelli), Baldi's four-cylinder engine had a different camshafts drive and air cooling. It was supercharged using a Cozette compressor and delivered a respectable 75 HP at 9000 rpm.
Presented at the Milan Show in November 1939, Italy's entry into the war aborted the surely promising career of this machine.
Source: Sergio Scalerandi
Image caption: Tazio Nuvolari, Bianchi 1929 Freccia Celeste 350
http://cybermotorcycle.com/marques/bianchi/bianchi-frecia-celeste.htm
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