HINDSIGHT – DIESELS AT INDY
Roots-type supercharger, and on the dyno figures of 340bhp at 4000rpm on 15psi boost pressure were recorded. California-based Frank Kurtis
Pole sitter, Freddie Agabashian, appears to be in the centre of the front row as the cars pull up for the start of the 1952 Indianapolis 500
the Speedway’s owner, Eddie Rickenbacker, he had been happy that it would last the distance but concerned that it might not have the speed to qualify. The former fighter pilot said that if it could compete four laps at over 80mph it would be included on the grid regardless. In the event, driver Dave Evans achieved an average of 96.871mph. During the race itself, Evans
went the full distance on 31 gallons of fuel (costing a total of $2.55), without having to make a single pit stop. While his Cummins engine averaged 16mpg, the other stock blocks were averaging around 10mpg. Evans’ riding mechanic, Thane Houser, did signal to the pits to enquire when they should come in as the water temperature was beginning to rise, but there was no answer so they kept plodding on. After the race, it was discovered that the crew member in charge of hand signalling had lost the piece of paper with the ‘key’ to those signals. The miscreant’s name was Jimmy Doolittle, already by then a well- known figure in air racing and later to lead the famed Doolittle Raid on Japan.
DURABILITY, NOT SPEED Twelve cars finished ahead of the diesel that day, but that was not the point. The objective of the exercise had been to prove the diesel’s durability, not its outright speed. The Duesenberg-Cummins was refurbished after the race and sent on a tour of Europe that included demonstration runs at
Cummins used one of its own trucks to transport its racecar to Indianapolis. Truck sales soared after the car’s blistering performance in qualifying
Brooklands and Montlhéry. Three years later, Cummins
entered two cars at Indy – one with an experimental two-cycle motor and supercharged, the other with a standard four-cycle engine. Debate was raging
the White River. The two-cycle engine disappeared forever, and no diesel of any kind would appear again until after the Second World War. In an attempt to encourage variety for 1950, the race
“Evans went the full distance on 31 gallons of fuel, without having to make a single pit stop”
within the company about the relative merits of the two technologies and this seemed a good opportunity to put them head to head. ‘Stubby’ Stubberfield finished the race in 12th place with the two- cycle, which suffered vibration problems, while Evans went out with transmission troubles. Immediately after the race, the two-cycle engine contracted and then seized as it cooled and legend has it that Clessie Cummins promptly ditched it into
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www.racecar-engineering.com • May 2012
organisers allowed diesels a large displacement advantage. Cummins was attracted back, this time using a six-cylinder JBS-600 truck engine, increased in size to 401ci with an 1/8-inch overbore so that it could be used with the original rods and crankshaft (the limit for diesels had been set at 402ci, supercharged or not). Efforts were made to lighten the engine by fitting an aluminium head, block and pistons, plus a magnesium crankcase. Use was also made of a large, gear-driven,
was contracted to build a chassis, extended by four inches to accommodate the larger engine. With Jimmy Jackson at the wheel, the green, rear-drive car qualified for the back row of the grid and dropped out of the race on the 52nd lap with supercharger drive failure. At this stage nobody was that impressed. But in September that year Jackson set six international records at Bonneville with the car, including the Flying Mile. The ‘Green Hornet’, as Jackson dubbed it, was converted into a dirt track Sprint Car before being restored and displayed at the Speedway’s Hall of Fame museum. Meanwhile, the company vice president in charge of engineering, Clessie’s brother, Don, went away to improve matters for 1952.
INNOVATIVE DESIGN The story of that year’s car is not just of its diesel engine, but of its overall concept. Kurtis built the new car with an innovative, low-slung design – probably the lowest at the Speedway – based on weight control and a desire to lower the c of g. The engine was completely on its side and an offset driveshaft not only assisted in reducing height but also enhanced cornering. This configuration was eventually embraced by the rest of the Indianapolis fraternity, but it has been said that the slippery 1952 Cummins made a very early impact on the science of aerodynamics at the Speedway. Wind tunnel testing was carried out at the University of Kansas, supervised by Agabashian, and this is thought to have been a first for an Indy car. Like its 1930s predecessors,
the red and yellow 1952 Kurtis-Cummins ‘roadster’ was frugal and could probably have completed the race on just 50 gallons. However, weight and subsequent tyre wear was a problem. The car weighed almost 2500lb (1114kg) compared to the 1600lb (726kg) of the leading Offy-powered cars. This
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