Ford P68

Background

At the end of the 1967 season the FIA redrew the rules for sports car racing. Engine capacity was limited to 3 litres for the lightest, most advanced Group 6 sports prototype class, while a new 5 litre Group 4 Sports Car class was introduced for vehicles of which at least 50 examples had been built. Ford's American headquarters organisation withdrew from sports car racing at the end of 1967, leaving those teams committed to running the aging GT40 without factory support. While some teams, such as JWA, decided to go down the Group 4 Sports Car route and began work on updating the GT40, Alan Mann Racing decided to build a brand new prototype car around Ford's recently introduced 3.0L DFV V8 Formula One engine.

Raising sponsorship from Ford, as well as Burmah-Castrol and Goodyear, AMR procured the services of leading Ford aerodynamicist Len Bailey, who had designed much of the GT40's bodywork, to work on their new car.

Design

The car was built to Group 6 regulations, with an open two-seat bodywork design. This was perhaps rather liberally interpreted, with only a small hatch in the otherwise enveloping roof being left open to the elements. The hatch also allowed the driver to see the centrally mounted rear-view mirror.

One major advantage of the open prototype regulations was that they permitted a much lower roofline than otherwise would have been possible. Bailey used this to create an extremely low, long, curvaceous, aerodynamically efficient design. With a C_d of only 0.27 and a frontal area of 14 ft² the 3.0L engine was sufficient to push the P68 to over 350 km/h, faster than contemporary Formula One cars. However, former driver Frank Gardner has criticised Bailey's pursuit of aerodynamic efficiency at the expense of driver comfort. In order to keep the P68 on the road, Bailey incorporated a patented, vortex-generating tail scoop, intended to create downforce without adding to drag. However, although the car has since been shown to produce moderate downforce at speed, this is mostly over the front wheels. The resultant high-speed instability led to both John Surtees and Jack Brabham refusing to drive the car. Over the following months the P68 sprouted ever larger rear spoilers, and small chin spoilers to stabilise the car.

Underneath the curvaceous bodywork, the chassis was a riveted, aluminium monocoque, with steel bulkheads onto which the suspension components were mounted. The DFV engine was supported in an aluminium cradle behind the driver. Unlike the Lotus 49 for which the DFV had been designed, the engine was not used as a structural chassis member. In contrast, the suspension layout was almost a direct copy of contemporary F1 practice. Contemporary observers commented on the oversized front hub components, potentially allowing the car to be converted to four-wheel drive at some point. The radiator was mounted in the nose, although later enhancements to cooling resulted in a wider opening being incorporated from mid-season. Fuel was stored in two deformable cells, one in each sill.

Following poor results, during the winter of 1968 Len Bailey adapted the P68's monocoque to fully exploit the open-roof regulations. A fully open spyder prototype was produced with almost completely new bodywork panels; even lower and wider, it also included a dramatic reduction in length. Mechanicals were carried over from the P68 in almost unchanged form. This new car was numbered the P69, although differences with the P68 were only skin deep. In an attempt to cure the same stability problems that afflicted the P68, the P69 had an innovative system of interconnected, hydraulically-controlled, partially automatic, adjustable aerofoil wings. However, following several accidents with similar systems during Formula One races, the wings were swiftly banned by the FIA early in the season. Without wings, AMR judged that the car would require a complete redesign, subsequently the P68/P69 project was not continued after this point.

Race history

The first batch of cars was ready for the European season-opening BOAC 500 race, at Brands Hatch on 7 April 1968. Even this early in its career, the P68 had started to grow spoilers and air dams at its front and rear. Two cars were entered, for Bruce McLaren and Denny Hulme, and Jochen Rindt and Mike Spence. However, the two cars were relatively untested, with one actually being brand new, and teething troubles beset the weekend. Although initially slow during practice, gradual tuning and tweaking meant that by the end of qualifying McLaren had managed to put in a lap fast enough to take second place on the grid, splitting the works Porsche 907s. Unfortunately, the Rindt/Spence car had suffered an engine mount failure and failed to qualify. Spence, something of a Brands Hatch specialist, was substituted into the lead car for the race, and was at the wheel, leading the race, when a rubber joint in the transmission failed, putting the car out. Although neither car had finished, the pace and performance while running looked to be promising better for the future.

With Mike Spence's death during practice for the 1968 Indianapolis 500, fellow Brit Chris Irwin was drafted in for the P68's next race: the 1968 1000km Nürburgring. He was lucky to escape death when he lost control of his car at the Flugplatz during practice, although his injuries were severe enough for his career to be ended. The car was destroyed. One tantalising highlight occurred when Frank Gardner, who performed much of the P68's limited developmental testing, took pole position at the 1000km Spa race.

For 1969 AMR intended to replace the P68 with its sister car, the P69. However, by the time of the 1969 BOAC 500 race only one P69 was ready. After trying the P69, prior to qualifying, a whimsical Jack Brabham flatly refused to drive the car in fear. That left only a year-old P68 to carry the AMR flag, in the hands of Hulme and Gardner. A large, high-mounted wing was attached directly to the tops of the rear suspension towers, which went some way to reducing rear-end lift at speed. The final competition outing for the Ford 3L prototype was at the AMOC Martini Trophy meeting at Silverstone.