Jaguar D-Type

1955

 

 

The Jaguar D-Type, like its predecessor the C-Type, was a factory-built race car. Although it shared the basic straight-6 XK engine design (uprated to 3.8 litres) with the C-Type, the majority of the car was radically different. Perhaps its most ground-breaking innovation was the introduction of a monocoque chassis, which not only introduced aircraft-style engineering to competition car design, but also an aeronautical understanding of aerodynamic efficiency. The D-Type was introduced purely for competition, but after Jaguar withdrew from racing, the company offered the remaining, unfinished chassis as the roadgoing Jaguar XKSS, by making changes to the racers: adding an extra seat, another door, a full-width windshield and primitive folding top, as concessions to practicality. The Jaguar D-Type, like its predecessor the C-Type, was a factory-built race car. Although it shared the basic straight-6 XK engine design (uprated to 3.8 litres) with the C-Type, the majority of the car was radically different. Perhaps its most ground-breaking innovation was the introduction of a monocoque chassis, which not only introduced aircraft-style engineering to competition car design, but also an aeronautical understanding of aerodynamic efficiency. The D-Type was introduced purely for competition, but after Jaguar withdrew from racing, the company offered the remaining, unfinished chassis as the roadgoing Jaguar XKSS, by making changes to the racers: adding an extra seat, another door, a full-width windshield and primitive folding top, as concessions to practicality.

 

The new chassis followed aircraft engineering practice, being manufactured according to monocoque principles. The central tub, within which the driver sat, was formed from sheets of aluminium alloy. To this was attached an aluminium tubing subframe carrying the bonnet, engine, front suspension, and steering assembly. The rear suspension and final drive were mounted directly onto the monocoque itself. Fuel was carried in deformable bags inside cells within the monocoque; another aircraft innovation.

 

The highly efficient, aerodynamic bodywork was largely the work of Malcolm Sayer, who joined Jaguar following a stint with the Bristol Aeroplane Company during World War II. Although he also worked on the C-Type, the limitations of the conventional separate-chassis did not allow full expression of his talent. For the D-Type, Sayer insisted on a minimal frontal area. To reduce its height, Haynes and former-Bentley engineer Walter Hassan developed dry sump lubrication for the XK engine. By also canting the engine over by 8° (resulting in the trademark, off-centre bonnet bulge) the reduction in area was achieved. Care was taken to reduce drag due to the underbody, resulting in an unusually high top speed; for the long Mulsanne Straight at Le Mans, a large vertical stabiliser was mounted behind the driver's head. For the 1955 season, factory cars were fitted with a revised, long-nose version of the bodywork, which increased top speed even further.

 

Mechanically, many features were shared with the outgoing C-Type. The ground-breaking disc brakes were retained, as was the XK engine. Apart from the new lubrication system, as development progressed during the D-Type's competition life the engine was also revised. 1955 saw the introduction of larger valves, and an asymmetrical cylinder head design within which to accommodate them. The Jaguar D-Type was the second racing car to have Dunlop disk brakes. The Citroën DS, introduced a year later, was the first production car with disk brakes in Europe. The Crosley Hotshot was the first American automobile with disk brakes, in 1949.

 

1955, Jaguar D Type Long Nose


The D-Type was produced by a team, led by Jaguar's race manager Lofty England, who always had at least one eye on the 24 Hours of Le Mans, the most prestigious endurance race of the time. As soon as it was introduced to the racing world in 1954, the D-Type was making its presence felt. For the 1954 24 Hours of Le Mans the new car was expected to perform well, and perhaps even win. However, the cars were hampered by sand in their fuel. After the fault had been diagnosed and the sand removed, the car driven by Duncan Hamilton and Tony Rolt quickly got back on the pace, finishing less than one lap down on the winning Ferrari.

 

Ironically, after Jaguar had withdrawn from motorsport at the end of the 1956 season, 1957 proved to be the D-Type's most successful year. In the 1957 Le Mans race D-Types took five of the top six placings; Ecurie Ecosse (with a large degree of support from Jaguar, and a 3.8L engine) again took the win, and second place. This was the high-water mark in the car's career however.

 

 

For 1958, the Le Mans rules were changed, limiting engine size to 3 liters for sports racing cars, thus ending the domination of Jaguar's D-Type with 3.8 liter XK engine. Jaguar developed a 3-liter version of the XK engine, which powered D-Types in the 1958, 1959 and 1960 Le Mans races. However, the 3-liter version of the XK engine was never reliable and by 1960 was not producing enough horsepower to be competitive.

With ever decreasing factory support and increasingly competitive cars from rival manufacturers, the D-Type's star waned. Although it continued to be one of the cars to beat in club- and national-level races it never again achieved a podium result at Le Mans, and by the early 1960s had disappeared into obsolescence.

 

Jaguar D-Type

 

The new chassis followed aircraft engineering practice, being manufactured according to monocoque principles. The central tub, within which the driver sat, was formed from sheets of aluminium alloy. To this was attached an aluminium tubing subframe carrying the bonnet, engine, front suspension, and steering assembly. The rear suspension and final drive were mounted directly onto the monocoque itself. Fuel was carried in deformable bags inside cells within the monocoque; another aircraft innovation.

 

The highly efficient, aerodynamic bodywork was largely the work of Malcolm Sayer, who joined Jaguar following a stint with the Bristol Aeroplane Company during World War II. Although he also worked on the C-Type, the limitations of the conventional separate-chassis did not allow full expression of his talent. For the D-Type, Sayer insisted on a minimal frontal area. To reduce its height, Haynes and former-Bentley engineer Walter Hassan developed dry sump lubrication for the XK engine. By also canting the engine over by 8° (resulting in the trademark, off-centre bonnet bulge) the reduction in area was achieved. Care was taken to reduce drag due to the underbody, resulting in an unusually high top speed; for the long Mulsanne Straight at Le Mans, a large vertical stabiliser was mounted behind the driver's head. For the 1955 season, factory cars were fitted with a revised, long-nose version of the bodywork, which increased top speed even further.

 

Jaguar D type Cockpit Detail