When racecars whiz across the finish line, it’s usually the winning driver that gets all the praise. But sometimes the glory can come from knowing why drivers are able to secure the win. Engineers at Dallara Automobili S.p.a. in Parma, Italy, would agree. Behind the scenes, they are always devising new methods to make their racecars milli-seconds faster, ultimately contributing to a win.
Building Indy Racing League (IRL) cars since the league’s inception in 1997, Dallara designs cars that are renown across the globe for their advanced design and engineering, facets that continually raise the benchmarks for safety, speed, and performance at the world’s most prestigious racetracks.
Dallara’s mission is to constantly improve the aerodynamics, frame, and structure of its racecars, to ensure they remain a top choice for IRL race teams worldwide. This means each component of an auto racing chassis must be carefully designed to optimize overall performance.
Revisiting the past. In the late 1980’s, racecar designers abandoned a pull-rod suspension for a push-rod suspension. This meant that all of the road loads were transferred to the spring and dampers through a very stiff beam (the push-rod) that connected the lower end of the upright to the top of the monocoque (the main chassis structure). This made it very easy to change a spring or a damper setting in a design, and also introduced what became known as “high nose” cars.
In 2002, Dallara engineers considered returning to the pull-rod suspension model. There was evidence that the pull-rod suspension may have certain advantages over the push-rod. Namely, the pull-rod layout moves the mass of the front suspension downward, which is always a benefit for racecars. In addition, wind tunnel and Computational Fluid Dynamics engineers thought the pull-rod layout would fit nicely with the bodywork of the car.
For Dallara, the main challenge involved in making this change was to engineer the pull-rod style suspension in a way that still included a car’s key features. They needed to keep the cars simple, light, and stiff, while passing rigorous front crash tests and remaining cost effective. What’s more, Dallara engineers found that a big cut out at the bottom of the tub that houses the spring and damper assemblies could potentially weaken the main chassis structure serving as a crack generator during an impact; the pull-rod suspension model had revealed a weakness in the monocoque, an area that is highly stressed during crash tests.
Design and simulation in one native design environment. Using Pro/ENGINEER, Dallara design engineer, Mauro Dondi, and structural engineer, Mario Saccone, worked together to create and test the chassis design. Mauro, a superuser and champion with Pro/ENGINEER, produced 15 different design models in less than two weeks, and Mario gave him real time feedback on features like stiffness and robustness.
The suspension stiffness was an important element of the design. The new suspension, although inherently less stiff than the old one, had to be just as strong without a weight increase. The Dallara engineering team worked together to analyze eight different layouts putting each design through a series of indoor static tests.
Luca Pignacca, chief designer at Dallara, explains, “The design environment with Pro/ENGINEER is fantastic. You can have two designers - a structural engineer and a design engineer - playing with the shape. The designer can have multiple ideas and can get immediate feedback from the structural engineer because they’re both working on the same model at the same time. The structural engineer can tell the design engineer immediately if something is going to work or not.”
Passing the test. The criteria involved in an IRL front crash test is complex. First, the complete monocoque assembly is filled with ballast, reaching 1,982 pounds. Then it is launched against a solid steel wall two times, one immediately after the other, at a speed of 12 m/sec (first impact) and 8.5 m/sec (second impact). During the test, the deceleration must not exceed the required figures (40 g average, 80 g maximum for a maximum of 10 milliseconds), and the monocoque must not be damaged during the test. The accuracy of the simulation and analysis results from Pro/ENGINEER give Dallara the confidence its cars will pass the safety tests with flying colors.
“We realize it’s a bit risky because sometimes it’s difficult to see all the potential problems,” says Pignacca. “But with Pro/ENGINEER, we’re sure we won’t have any problems. For example, we make a virtual prototype of a suspension wishbone that we’re going to make 40 of, because we know they won’t clash during the suspension stroke, or break under load, and so forth. The structural analysis generated by Pro/E assures us that we’re going to pass the tests and gives us the assurance to move forward with manufacturing.”
During a race, spectators watch with excitement to see who will pull ahead in the final seconds. The driver may ultimately emerge with the win, but the people behind the scenes feel the satisfaction too. Engineers at Dallara spend countless hours ensuring IRL drivers not only win, but cross the finish line safely too. In 2002, eight of the top ten finishers in the Indy 500 were driving a car built by Dallara. By using Pro/ENGINEER, Dallara can be sure their cars will be sitting in the winner’s circle in races well into the future.
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