Eagle Mk1 - Design

Design

A highly successful motor racing driver in many disciplines, Dan Gurney had been driving in Formula One since the late 1950s. While driving for the Brabham works team, he joined with a group of prominent motor racing figures and financial backers in the United States, including Carroll Shelby, to found All American Racers. This effort was largely backed by the Goodyear Tire & Rubber Company, in an effort to challenge Firestone's longtime dominance of American open-wheel racing. Inspired by the performance of Jack Brabham and Bruce McLaren's own teams, AAR decided to enter Grand Prix racing. Then as now, the main engineering hub for Formula One manufacturers was in the United Kingdom, so AAR set up a subsidiary team known as Anglo American Racers which, while registered and based in the USA, was named in deference to the cars' British Weslake engines.

To achieve AAR's dual aims of winning in both Formula One and Champ Car formulae, AAR hired ex-Lotus designer Len Terry to work for the American outfit. His brief was to create a chassis that could be used both for the twisting road course circuits of the F1 series, as well as the broad ovals of the North American series. Terry was ideally placed to be able to fulfill such a brief, having just completed the 1965 Indianapolis 500-winning Lotus 38 for Colin Chapman's team.

The design of the Mk1, and its Indy sister design the Mk2, closely followed the 38, with a riveted aluminium monocoque central section, carrying an unstressed engine mounted behind the driver. The lines of the chassis were remarkably clean and elegant, and the car sported a distinctively beaked radiator opening at the front. Suspension components were mounted directly on to this monocoque, and consisted of a comparatively conservative lower wishbone and single top link for each wheel which also served as a rocker for the inboard-mounted spring/damper package. The Mk1 was designed around the forthcoming Aubrey Woods-designed Weslake V12 engine while the Mk2, essentially the same chassis design, was designed to accept the quad-cam Ford V8 that had powered the previous year's Indy 500 winner (Jim Clark, in the Terry-designed Lotus 38).

While driving for the BRM Formula One team in 1960, Gurney became acquainted with BRM engineer Aubrey Woods, who then moved to Weslake Engineering. Through Woods, Gurney became aware of a Weslake engine research project funded by Shell Oil. This two-cylinder, 500-cc test engine produced impressive horsepower, and Gurney extrapolated the test engine's output to a 3-liter, V12 Grand Prix engine, potentially putting out up to 450 horsepower, and he commissioned Weslake to build the engine.

While five Mk2 chassis, complete with four-cam Ford V8s, qualified for the 1966 Indianapolis 500, the Weslake V12 was not available for the start of the Formula one season. The first Mk1s took to the track with old 2.7-liter Coventry Climax inline-4 FPF engines in their place. Once the Weslake was ready, however, the car proved to be highly competitive, if unreliable. The high-revving V12 had been constructed using surplus machine tools dating from World War I, so tolerances and parts interchangeability were poor. Nevertheless, when running the Weslake was an immediately arresting engine, with a distinctive V12-scream, and developed 360bhp even in its earliest development phase. By the end of the 1967 season this figure was over 400bhp, easily competing with the Ferrari and Honda V12s, and the newly-introduced Cosworth DFV V8. One mechanical flaw that limited the engine's power output involved a design mistake in the oil scavenging system. This problem -- discovered too late in the development process to correct -- caused oil to pool in the engine's sump, slightly reducing power. Gurney described the effect as "taking the edge" off the engine after three or four laps of a race.

Three Mk1 chassis were produced with the original aluminium construction, but the fourth incorporated advanced and exotic metal alloys. This included extensive use of titanium for many of the componentry, and a high percentage of magnesium sheet in the monocoque panelwork. Owing to its novel construction materials this car, chassis number 104, was referred to as the Ti-Mag Car. Gurney was well aware of the risks involved in driving a car made from such flammable materials. After witnessing Jo Schlesser's death in a magnesium-fuelled fireball during the 1968 French Grand Prix, Gurney compared racing in 104 to "driving a Ronson cigarette lighter".