The Indianapolis race track was constructed in 1909 as an automobile industry test and development facility. Indianapolis was chosen rather than Detroit because in the early part of the 20th century, Indianapolis was the motor capital of America; until 1905, more cars were built there than in Detroit.
Although the four-kilometre track was completed in 1909, the first Indy 500 mile race was not held until 1911. The original surface was tar-and-gravel, and in some pre-500 races, the dangers from punctured tires, flying stones and poor traction indicated an urgent need for a better surface.
Concrete was considered, but bricks were chosen for their superior durability, giving the track its famous 鈥淏rickyard鈥� nickname. They were replaced with asphalt in 1936.
The banking was 16.6 degrees, rising to 36 degrees for the outer three metres in the turns to direct cars away from the wall. Turns were designed for speeds of 129 to 145 km/h.
The first Indianapolis 500 race was won by Ray Harroun driving a Marmon Wasp with a new device known as a rear-view mirror. Racers were little more than regular road cars stripped of fenders, headlights, running boards, etc., and tuned for a bit more speed. Finishing was a significant accomplishment, and a victory or high finish generated wonderful publicity. Purpose-built racers gradually evolved.
The Indianapolis 500 soon became famous enough to attract a wide variety of American and European cars. But there was one common factor: they all had the piston engines, usually gasoline fuelled, found in regular road cars.
This status quo was finally challenged in the 1960s when a new powerplant shook the conservative Indy racing establishment to its roots.
The interloper was the gas turbine, the engine 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 breathes normally.
In a gas turbine, a high-speed rotary compressor pumps huge volumes of air into a combustion chamber, where fuel is injected and ignited. The resulting gas flow drives both this compressor and a series of turbines geared to an output shaft. There is no reciprocating motion as in piston engines.
A gas turbine has several advantages. It is lighter for a given power, a steep torque curve eliminates the need for a conventional transmission and it burns cheaper, less sophisticated fuel.
Some Indy car racers tried turbines in the 1950s and early 鈥�60s without success. Then car owner Andy Granatelli (of STP engine additive fame) gave it a try. He had been attempting to introduce the Ferguson four-wheel-drive system to Indy cars, but decided he needed a turbine鈥檚 extra power.
The United States Auto Club (USAC) had no rules for turbines, so officials arbitrarily set a limit of 161.3 square centimetres (25 square inches) on the air inlet. Turbines need lots of air, so USAC thought this would keep piston engines competitive.
Granatelli had a new four-wheel-drive car designed around the turbine. Its backbone frame had the driver and engine positioned amidship on each side of this 鈥渟pine.鈥� The Pratt & Whitney-designed ST6 aircraft gas turbine, manufactured by United Aircraft of sa国际传媒, had a maximum of 540 horsepower. Its 141.3 square centimetre inlet easily met USAC鈥檚 limit.
The STP turbine racer entered the 1967 race driven by racer Parnelli Jones, winner of the 1963 Indy. Wary of USAC鈥檚 reaction to turbines, Granatelli instructed Jones to use only the power necessary to win. Jones qualified on the second row, and when the flag dropped sped easily into the lead which he held for 197 of the 200 laps.
Jones would have won had a $6 transmission bearing not failed on lap 197, giving a piston-engine car victory. There was much consternation along pit row, and piston-engine car owners mounted a strong lobby. USAC caved in and lowered the turbine air intake area to 103.2 square cm (16 square inches).
In spite of this, Granatelli returned with three all-new turbine cars for 1968 built by Lotus Cars of England. These wedge-shaped racers had the driver seated forward with the engine behind. The smaller air intake rule caused some loss of power.
The turbine鈥檚 performance was now about equal to piston engines. Two STP turbines retired with fuel-pump failures, and the third smacked the wall. USAC had accomplished its goal of apparently neutralizing the turbine鈥檚 superiority. But under continuing piston-engine lobbying, USAC further reduced the air intake to 77.4 square cm (12 square inches) for 1969, effectively ending the turbine era at Indy.
