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The Aston Martin DBR4/250, commonly referred to simply as the DBR4, is a Formula One racing car, designed by Ted Cutting for the sports car manufacturer Aston Martin. Following notable successes in sports car racing during the mid- to late-1950s — culminating in winning the 24 Hours of Le Mans endurance race and the World Sportscar Championship title in — the DBR4 was intended to repeat this success in the highest tier of open-wheel racing. The DBR4 was largely based on the DB3S sportscar, and borrowed that vehicle's basic chassis and engine layout. Although it was tested as early as 1957, the DBR4 did not make its World Championship debut until the 1959 Dutch Grand Prix, driven by Roy Salvadori and Carroll Shelby. However, its long gestation period meant that by the time it finally entered competition much of its concept and technology had been superseded, and the car was not a success. The DBR4 was replaced by the lighter Aston Martin DBR5/250 in early 1960, but when that car also failed to provide competitive results Aston Martin abandoned Formula One to concentrate on their more successful sports car projects. ==Design== A potential open-wheeled Aston Martin racing car had been discussed as early as 1955, and a hastily-constructed prototype was tested in the Australian and New Zealand races in early 1956, driven by Reg Parnell. Following successes in this Antipodean experiment, and despite the majority of Aston's racing department being fully occupied with the sports car program, Aston Martin decided to pursue a Formula One entry in earnest. However, the company's emphasis on sports car competitions meant that attention was often diverted from the Formula One program, and development delays were common almost from the outset. Building on Aston Martin's established road car and sports racer template, the chassis of the DBR4 was a conventional spaceframe structure, skinned with aluminium bodywork. Beneath the skin the DBR4's basic design was closely related to the DB3S sports car of 1956, but with its ancillary components more tightly packaged to enclose them in the smaller, single-seater body. Although some manufacturers had started to use wind-tunnel testing for racing cars, such as the Bristol 450, aerodynamics as a science was still in its infancy where road vehicles were concerned. As a result of this, although the DBR4's bodywork appeared svelte and streamlined, the effect was ruined by the decision to mount a large air intake on the side of the bonnet, and to install a relatively tall, near-vertical windscreen. Suspension was handled by double wishbones with coil springs and telescopic dampers at the front, and a de Dion tube system with torsion bar springs at the rear. While this arrangement had been state-of-the-art in the early years of the 1950s, by the time that the DBR4 made its first public appearance most racing car manufacturers were moving to all-round independent suspension, offering better handling, traction and road-holding than the older system employed at the rear of the Aston. The DBR4 was the last new Grand Prix car to use the de Dion system. This same suspension system would be adapted to the DBR3 sports car which was being developed at the same time as the DBR4, but would be abandoned less than a year later when the DBR3 was considered a failure. To bring the car to a halt, Girling disc brakes were fitted all round. The DBR4 also shared the basic double overhead camshaft straight-6 Aston Martin engine design with its brethren, but sleeved to reduce its capacity to 2.5 litres. Although Tadek Marek's design was a reliable and powerful unit in its 3.7 litre road car form, the reduced capacity racing motor was hard-pressed to cope with the heavy chassis and poor aerodynamics, and frequent engine failures blighted the DBR4's brief racing career. Aston Martin claimed a output for the DBR4's engine. However, it was common practice at the time to overquote engine power, and a more realistic value is closer to . This value is still higher than that provided by the Coventry Climax ''FPF'' straight-4, used by contemporary manufacturers such as Lotus and Cooper, but the Aston Martin engine weighed appreciably more. The engine drove the rear wheels through a proprietary David Brown gearbox, provided by Aston Martin's owners. A total of four Aston Martin DBR4/250s were built between 1957 and 1959, with three surviving to date. Recognising their failings, the Aston Martin race team reworked the DBR4 into the DBR5 for the season. The DBR5 was smaller and lighter, and engine modifications meant that the power output was finally close to the figure originally claimed by the Aston Martin workshop. The DBR5 also boasted all-independent suspension, but results did not improve from those of the DBR4 and both DBR5s were eventually broken up. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Aston Martin DBR4」の詳細全文を読む スポンサード リンク
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