The state of the art
The year 1972 must be regarded as the year of the Eagle at Indianapolis, for clearly no other car had greater impact on the 2.5-mile Indianapolis Motor Speedway than the latest model Eagle from Dan Gurney’s All American Racers in California.
Although a single yard of cobblestone bricks to mark the start/finish line are all that remain of the millions that paved the original “brickyard”, Indianapolis is still bound by traditions that go back to the first 500-mile race in 1911. This, however, is not true in the area of design. Until a few years ago, Indianapolis was tightly insular. This is no longer so, for the latest in Indy design also shows the latest influences of the aircraft industry plus a close relationship with Formula One and Can-Am design trends.
As pole-sitter and pace-setter for Indy’s month long pre-race preparations, Bobby Unser driving Dan Gurney’s Olsonite-sponsored ’72 Eagle powered by a four Cylinder 2.65-litre turbo-charged Drake Offy fully represented the state of the Indy art and close study of Unser’s car was high on the priority list of the opposition.
One would be very hard pressed to see any truly outstanding design advancements or innovations on the Eagle for it is in virtually every way a contemporary 1972 car. But it is in the execution of every detail that Gurney’s team have been able to gain, just a little bit so that the cumulative effect is one of superiority in the best terms measurable— speed.
The Eagle is the product of a compact design team with Gurney as the head and Gurney’s former draftsman Roman Slobadynskyj as designer. The basis of the design is a low, wide monocoque chassis, not unlike the trend-setting M16 McLaren which set Indy on its ear in 1971. Like the McLaren, the new Eagle has conventional top rocker/lower wishbone front suspension with inboard coil spring and shock absorber units. At the rear, suspension is also quite conventional with twin radius rods, top link and lower parallel links. An important area of development for the Gurney car is the use of a hydraulically operated driver controlled adjustable rear anti-roll bar which permitted Unser to adjust the rear swaybar to account for changing track conditions or the change in handling experienced as the 75 gallons (US) fuel load lightened five times during the race.
Unlike the M16 McLaren which showed the obvious influence of Maurice Phillipe’s Lotus 72 with it’s side-mounted water radiators just ahead of the rear wheels, Slobadynskyj located the rads further forward, just aft of the front wheels. Where the McLaren’s lightweight aluminum rads took air from the front and permitted the hot air to spill out to the rear, the Eagle’s brass rads took air from the front but then shot the spent air out to the side of the car.
But, the fantastic speed increases this year which saw Bobby Unser secure the pole starting position with a four lap average speed of 195.940 m.p.h., over three m.p.h. faster than his nearest opposition Peter Revson’s works Gulf McLaren M16B, and which saw the entire 33-car starting line-up qualify over the 1971 pole position winning average speed of 178.696 m.p.h. set by Peter Revson’s M16 McLaren, did not come from such things as chassis construction, suspension design and radiator placement. Instead, the greatest speed increase in a single year in Indy history came from advancements in aerodynamics, tyre developments and engine performance improvements.
This year, USAC loosened up a previously tough line on wings. For the first time wings as such were permitted under the rules and in fact they are now quite liberal. Last year’s “aerodynamic surfaces” had to be an integral part of the bodywork. This year, Formula One style rear wings overhanging up to 42 in. from the wing’s trailing edge to the centre line of the rear wheels keep the rear end of the car on the ground. Maximum wing height from the lowest point on the chassis was increased from 28 to 32 inches which in effect puts the rear wing up in clean air above the car. At the front, canard fins as used in Formula One are the common form but like the rear wing, they have increased in their effect due to the easing of the rule which limited bodywork width from 3 in. out from the inside line of the front wheels to the centre line connecting the front and rear wheels. This in effect permits an increase in wing width of up to 12 in., for a very substantial improvement.
Both Goodyear and Firestone regard the Indy 500 as the most important event in the world and as a result, the amounts of money and manpower devoted to Indy tyre development easily explain the estimated 5 m.p.h. in average speed gained by tyres alone. The superiority of such Goodyear shod teams as Gurney’s Eagles and the McLaren teams of Penske and the works, indicates on which side of Akron the most work was done over the winter of 1971-1972.
Better use of aerodynamic downforce and better tyres without doubt produced better cornering power and nothing emphasizes this more than the fact that the speeds on the straights this year are approximately the same as last year at 215 m.p.h. In fact, some cars with this year’s greater wing drag are slower on the straights so that the 17 m.p.h. jump in the pole speed must come from better cornering. Unser’s Eagle was reported at 187 m.p.h. in the first turn so that at his slowest point on the track he is above the previous pole average speed.
The latest in racing technology has made Indy an almost flat out exercise. Better brakes permit deeper running into the turns while wings and tyres permit higher cornering speeds to the point that the brakes are used only briefly in the first and third turns and the driver is flat out through the second and fourth turns.
With all the flat out running at Indianapolis the final and most important area of the racing car must still be the power unit, either the venerable Offy in its fiftieth year or the youthful Ford still in its first decade. Gurney’s Eagles like most ’72 Indy front runners use the latest version of the four cylinder Drake turbo-charged Offy. Offy parts are available from Drake Engineering and a variety of tuners and teams conduct their own engine development programmes. Similarly the four overhead camshaft Ford V8 is available from A. J. Foyt who acquired rights to the engine from Ford several years ago.
The contemporary Indy engine, Ford or Oily, burning pure methanol produces between 800 and 1,000 horsepower from its 2.65-litres, depending on how much turbo-charger boost is used. Engine life is strongly influenced by how much boost is used.
The Fords at Indy were clearly outclassed by the Offies while the Offies in turn were outclassed by Gurney’s “super-short stroke” Offies in Bobby Unser’s and Jerry Grant’s Eagles. The Eagle four cylinder engines built by Gurney’s engine specialist John Miller were the only ones to sound like V8s and the performance of the cars using them indicated some special form of superiority.
One final special item which Gurney placed a great deal of faith in was the American-built Weismann transaxle which replaced the ubiquitous Hewland LG in Unser’s pole winning car. Gurney said that it was lighter, stronger and that Pete Weismann’s shop was nearby in Santa Ana, California, the home of the Eagle. Weismann who has built his reputation on a special locker differential, supplied gearboxes to other Indy teams as well as the Can-Am Shadow team but none have been as successful as the 1972 Eagle.
The packaging of the Eagle into the most significant Indy car of 1972 began last year and this early beginning became one of the most important single success factors, probably even more important than several key design features. Unser began the first track tests of the Eagle last November. By Indy time in May, he had driven over 3,000 Goodyear tyre test miles including a lap of 196 m.p.h. at Ontario and one of 190 m.p.h. at Indianapolis in March. There was no question that when the Indianapolis Motor Speedway opened its gates at the end of April, the Gurney Eagle Was the most ready.
That the Eagle was the most significant Indy car however is not to say that there was nothing else of importance at the Speedway. McLarens produced a second generation of the successful 1971 M16 that was a little larger, took-advantage of the latest in technology (tyres), rules (aerodynamics) and the spur of faster competition. But the M16B McLaren development was not as advanced as the Eagle’s partly due to a spate of engine failures throughout practice which hit both the works and the Penske teams. Even so, Revson’s works car (192.885 m.p.h.) and Donohue’s Penske car (191.408 tri,p,h.) were sufficiently fast to outclass the rest of the opposition and secure the two remaining front row starting positions when Unser had done with his record breaking.
A. J. Foyes new Coyote, a project from his fertile mind which revealed itself as a clever cross between a McLaren and an Eagle was disappointing, possibly through newness or possibly through using a Ford engine. The Indy establishment which huddled in awe at the prospect of Maurice Phillipe’s new Offy powered Parnelli design for Mario Andretti, Al Unser and Joe Leonard, recovered from the shock that the Parnelli was not a world beater and went back about their business. In four months Phillipe carried his design from birth to a functioning automobile but in that same time he could not fully shake down the teething problems that his dart-shaped monocoque with dihedral front and rear wings encountered. The front dihedrals remained to enshroud the front suspension while the rear dihedrals disappeared and the oil rads that they contained were tacked onto the body sides.
The problem or balancing the handling with the dihedrals would not be accounted for so the more conventional rear overhanging format were adopted, at least for the time being but Phillipe must be among those who remember that it took a little extra effort and time to make the Lotus 72 a World beater.
Another famous name who suffered from too much advance and not enough development time was former Chaparral designer Don Gates whose Antares lost its “ground effects” devices before it hit the Speedway and became a conventional car without enough preparation.
Eric Broadly produced a pretty car along conventional Indy lines. The outstanding characteristic of the Ford powered Lola T-270 was its sportscar type bodywork but unfortunately the car arrived without substantial previous testing and practice was used for initial sorting rather than high speed development. The effectiveness of the Broadley concept was proven however when Art Pollard, after qualifying the car at a speed of 181 m.p.h., proceeded to increase his speed to above 185 m.p.h. Regrettably. Pollard crashed when a rear hub failed and his outstanding effort was missed. — F. D. S.
Mark Donohue won the race for Penske after passing Jerry Grant’s Eagle which picked up some debris in a tyre with less than fifteen laps to run, but McLaren works driver Gary Bettenhausen led the most laps while Bobby Unser retired early on.