The A-Type (also known as the A-Series) was a range of racing cars built by Connaught between 1952 and 1953. The A-Type was raced from 1952 until 1954.
The A-Series' four cylinder engine still shared its basic design with the Lea-Francis unit used in the L-Series. Connaught had redesigned the engine and made a few changes. For example the heavy cast-iron block was scrapped in favour of an alloy block that was developed in conjunction with Laystall Engineering. By boring out the cylinders, the displacement was brought up to the two-litre limit from the original 1767cc. The valve drive consisting of two camshafts mounted in the block on either side was retained from the original Lea-Francis design. They actuated the valves with short pushrods. Fuel was fed to the engine through modified motorcycle carburretors. Late in its life the Works cars used Hilborn-Travers Fuel Injection.
The chassis was designed from scratch with a focus on simplicity and making everything lightweight. It was a ladder frame constructed of two steel oval tubes. The first/test car featured independent wishbone all-round suspension. After a few races the rear wishbones were discarded and replaced with a more advanced DeDion axle. The power was transferred to the rear wheels through a close-ratio Wilson pre-selector gearbox. Hydraulically assisted drum brakes provided the stopping power. Covered in a thin aluminium skin, the A-Series or A-Type Connaught was exceptionally light weighing in at under 600 kg.
McAlpine first took to the track during tests at Silverstone. Sadly he damaged the car and it could not make its racing debut until October 1950. Still powered by the 1.8 litre version of the engine, McAlpine managed to finish second to Stirling Moss in a 2.5 litre race at Castle Coomb. The lessons learned in the brief 1950 season were incorporated in the car and other than the DeDion axle included an airbox with ram intake mounted on the Carburetors and revised headers. The revised suspension created some handling problems, but as soon as they were ironed out, the Connaught was among the fastest F2 cars on the British Isles. Bad luck and silly mistakes postponed McAlpine's first win until August 1951 when he won the F2 race at Ibsley.
Just as the Connaught A-Series was entering production, the sport's governing body announced that the 1952 world championship would be run for Formula 2 cars instead of Formula 1. After Alfa Romeo's withdrawal from racing, this was the only way to get full and above varied grids for the Grands Prix. The production cars were the first to feature the full two-litre engine and at the first major race the first chassis was also upgraded to two-litre spec. The Connaught was popular with the privateers, but it struggled against the newly developed four cylinder Ferrari 500, which won every Grand Prix of the season. In British events the Connaught was still highly competitive and several victories were scored in the 1952 season.
Hilborn-Travers Fuel Injection was introduced on the new 1953 Works cars, which also featured a slightly longer wheelbase. Again the Connaught struggled at international events, but were often victorious in minor races. Most of British finest drivers like Roy Salvadori, Stirling Moss and Tony Rolt raced the Connaught. For 1954 new Formula 1 regulations were introduced with a displacement limit of 2.5 litres for naturally aspirated engines. This spurred the development of the Connaught B-Type with a slightly larger version of the four cylinder engine. It finally brought international success to Connaught and Britain when Tony Brooks won the 1955 Syracuse Grand Prix.
Today many of the surviving A-Series Connaughts are regularly raced in historic events all over Europe.
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