The Jaguar D-Type is a sports racing car produced by Jaguar Cars Ltd. between 1954 and 1957. Although it shares the basic straight-6 XK engine and many of its mechanical components with the C-Type, its aviation industry influenced structure was radically different. Innovative monocoque construction and an aeronautical approach to aerodynamic efficiency brought aviation technology to competition car design
Engine displacement began at 3.4 litres, was enlarged to 3.8 L in 1957, and reduced to 3.0 L in 1958 when Le Mans rules limited engines for sports racing cars to that maximum. Jaguar D-Types won the Le Mans 24-hour race in 1955, 1956 and 1957. After Jaguar temporarily retired from racing as a factory team, the company offered the remaining unfinished D-Types as XKSS versions whose extra road-going equipment made them eligible for production sports car races in America. In 1957 25 of these cars were in various stages of completion when a factory fire destroyed nine of them.
Total D-Type production is thought to have included 18 factory team cars, 53 customer cars, and 16 XKSS versions.
The structural design, revolutionary at the time, applied aeronautical technology. The "tub", or cockpit section, was of monocoque construction, mostly comprising sheets of aluminium alloy. Its elliptical shape and comparatively small cross-section provided torsional rigidity and reduced drag. To the front bulkhead was attached an aluminium tubing subframe for the engine, steering assembly, and front suspension. Rear suspension and final drive were mounted to the rear bulkhead. Fuel was carried in the tail and the designers followed aviation practice by specifying a deformable Marston Aviation Division bag in place of a conventional tank.
The aerodynamic bodywork was largely the work of Malcolm Sayer, who had joined Jaguar following a stint with the Bristol Aeroplane Company during the Second World War and later worked on the C-Type. For the D-Type, he insisted on a minimal frontal area. To reduce the XK engine's height, Jaguar's chief engineer, William Haynes, and former Bentley engineer, Walter Hassan, developed dry sump lubrication, and it has been said that the car's frontal area was also a consideration in canting the engine at 8�� from the vertical (which necessitated the offset bonnet bulge). Philip Porter, in his book Jaguar Sports Racing Cars, says that "[a] more likely reason was to provide extra space for the ram pipes feeding the three twin-choke Weber carburettors." Reducing underbody drag contributed to the car's high top speed; for the long Mulsanne Straight at Le Mans, a fin was mounted behind the driver for aerodynamic stability. For the 1955 season, factory cars were fitted with a longer nose, which lengthened the car by 7� inches and further increased maximum speed; and the headrest fairing and aerodynamic fin were combined as a single unit that smoothed the aerodynamics and saved weight.
Mechanically, many features were shared with the outgoing C-Type. Its front and rear suspension and innovative all-round disc brakes were retained, as was the XK engine. Apart from the new lubrication system, the engine was further revised as development progressed during the D-Type's competition life. Notably in 1955 larger valves were introduced, together with asymmetrical cylinder heads to accommodate them.
Elements of the body shape and many construction details were used in the Jaguar E-Type.
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