1968 Lotus 56 4WD turbine Indy racer. Click image to enlarge
Article and photo by Bill Vance
The Indianapolis race-track was constructed in 1909 as an automobile industry test and development facility. It was located in Indianapolis rather than Detroit because in the early part of the twentieth century, Indianapolis was the motor capital of America. Until 1905 more cars were built in Indianapolis than in Detroit.
Although the 4-km (2.5-mile) track was completed in 1909, the first Indy 500-mile race was not held until 1911. The original track surface was tar-and-gravel, and in pre-500 races the dangers from punctured tires, flying stones and poor traction demonstrated the need for a better surface.
Although concrete was considered, bricks were chosen for their superior durability, giving the track its famous “Brickyard” nickname. The track’s banking was 16.6 degrees, rising to 36 degrees for the outer 3,048 mm (10 feet) in the turns to direct cars away from the wall. Turns were designed for speeds of 129 to 145 km/h (80 to 90 mph).
The first Indianapolis 500-mile (805 km) race was won by Ray Harroun, driving a Marmon Wasp fitted with a new device known as a rear-view mirror. Indy racers were little more than regular road cars stripped of fenders, headlights, running boards, etc., and tuned for a little more speed. Finishing was a significant accomplishment, and a good showing generated wonderful publicity for manufacturers, and it wasn’t long before purpose-built racers evolved.
The Indianapolis 500 soon became famous and was contested by a wide variety of American and European cars. But there was one common factor: they were all powered by the type of piston engine, usually gasoline fuelled, found in regular road cars.
This status quo was challenged in the 1960s when a new powerplant shook the conservative Indy racing establishment to its roots.
The interloper was the gas turbine, the power that had revolutionized the aircraft industry. Although related to a turbocharger, they should not be confused. In turbocharging, an exhaust driven turbine drives a supercharger that increases power by pumping more air into an engine than it would breathe normally.
In a gas turbine, a high speed rotary compressor pumps huge volumes of air into the engine. When fuel is injected into this air and ignited, the resulting gas flow drives both the compressor and a series of turbines geared to an output shaft. There is no reciprocating motion as in a piston engine.
A gas turbine has several advantages. It is lighter for a given power; its fast rising torque curve eliminates the need for a conventional transmission; and it can burn cheaper, less sophisticated fuel.