Indy gets a Classy New Chassis

June 6, 2012
The newly designed Dallara DW12 chassis gets  elivered to IndyCar teams complete with a transmission and suspension.

Authored by:
Cathy Hein
Contributing Editor
Key points:
• Safety was a key point of focus in the new design.
• Race crews expect cars based around the new chassis to hit 225 mph.
For links to our features covering Indy through the past 10 years

For the first time in nearly a decade, IZOD IndyCar teams spent much of the winter months testing, thanks to this year’s introduction of the series’ next-generation race car. After years of design and development, the Dallara DW12 chassis made its official debut on March 25 in a road-course event, the Grand Prix of St. Petersburg in Florida, and will take to its first oval track in the crown jewel of IndyCar racing, the Indianapolis 500, on May 27. To the untrained eye, the DW12 looks a lot like its predecessor, the IR-05. Both use monocoque construction with loads supported by a carbon-fiber skin. However, the new chassis sports dimensional changes and a different weight balance, among other things, that pose significant engineering challenges that require changes, along with testing, testing and more testing.

IndyCar announced last July that a new chassis and driver-safety cell, made by Italian chassis manufacturer Dallara Automobili, would replace the existing chassis (also a Dallara model) as the basis of all IndyCar race cars in 2012.

Dallara was one of the original three constructors when the Indy Racing League debuted its own chassis formula in 1997. Dallara’s first model year was named the IR7, and the IR-05 chassis was introduced in 2007 and has been used through the 2011 season.

The decision to continue racing with a Dallara chassis was made by the seven-person Iconic (Innovative, Competitive, Open-Wheel, New, Industry-Relevant, Cost-Effective) Advisory Committee, consisting of engineers, IndyCar officials and former drivers. Over several months, the committee analyzed chassis designs from BAT Engineering, Dallara, Delta Wing, Lola, and Swift Engineering.

IndyCar’s objectives for the new chassis were that it was to be “safe, raceable, cost effective, American-made, more efficient, feature relevant technology, have a modern look and be ‘green.’” In the end, the Dallara chassis was chosen mostly because it delivered on safety and cost-containment objectives, but Dallara also promised to build the chassis at a new plant in Speedway, Ind.

“The new car is cost effective and it positions the series for tremendous growth and enhances the series’ relevancy to future automotive technology,” said IndyCar CEO Randy Bernard last July. “This car puts everything our stakeholders want on the racetrack: safety, competition on and off the track, diversity, efficiency, and more.”

What’s new
The general design philosophy for the new chassis centered on boosting performance by reducing overall weight and aerodynamic drag.

Dallara’s design features a rolling chassis, essentially a universal car that will be delivered to IndyCar teams complete, minus tires, driver seat, and steering wheel. It includes the transmission and suspension, which teams will no longer build in-house. IndyCar teams will fit the chassis with different body coverings for different tracks, including road courses and oval tracks.

According to IndyCar, the new chassis improves safety components, such as side-intrusion panels and wheel tethers. The cockpit is also longer and wider than the IR-05, which lets teams add padding underneath and behind the driver. The chassis’ lower profile and raised nose improves the driver’s position and gives him better sight lines, compared to the IR-05.

Although overall chassis length remains the same at 202.7 in., the wheelbase was reduced from 122 in. to between 118 and 121 in. Total weight of the chassis dropped 185 lb to 1,380, with a minimum weight determined once variables with suppliers, such as engine weight, were finalized.

The new chassis carries a direct-injected twin-turbo 2.2-liter V6 fueled by E85 gasoline (no longer E98), replacing the 3.5-liter aspirated V8s used since 1997. The engines are tuned to generate between 550 and 750 hp to suit different racetracks on the IndyCar Series schedule. An overtake-assist subsystem gives drivers a time-limited boost of up to 100 hp.

One of three manufacturers will supply engines: Chevrolet, Honda, or Lotus. It’s the first time the IndyCar Series has permitted several engine manufacturer to compete since 2005.

The Series originally expected a handful of manufacturers to design the aerodynamic kits for IndyCar’s new chassis — essentially the sidepods, engine covers, and front and rear wings. But initially only Chevrolet and Lotus signed on. Then, rising costs and a compressed timetable forced IndyCar to put off using several suppliers until next year. So for 2012, all teams will run Dallara’s oval and road-course aero kits.

IndyCar limited the cost for the new aero kit to a maximum of $70,000. With costs of the new chassis fixed at $385,000, representing a 45% drop from last year’s IR-05, Series officials estimate the complete rolling-chassis/engine- lease package will cost less than $1€million.

Testing, testing — and rising concerns
The chassis was unveiled to the media last May and examples of the chassis in the Dallara aero kit were on display in Indianapolis for fans to admire at last year’s Indy 500.

IndyCar driver Dan Wheldon took the first official test drive of the new chassis (outfitted with a twin-turbo 2.2-liter Honda V6) at the Mid-Ohio Sports Car Course last August. The road-course test was the first of 12 days of evaluation on three road courses and three ovals, including Indianapolis Motor Speedway.

Wheldon had high praise for the new car, citing its maneuverability and handling. “The car doesn’t necessarily drive differently, but it’s very reactive,” he said. “I think that’s because of the weight, and perhaps where it’s positioned. It feels nimble, light, and agile.”

However, as testing expanded, other drivers differed with Wheldon’s assessments, particularly on oval tracks. Concerns began to arise about the chassis’ handling and weight distribution after engine manufacturers began testing in early October at Mid-Ohio.

Last November, veteran IndyCar drivers Dario Franchitti (Honda) and Tony Kanaan (Chevy) returned to Indianapolis for two days of testing. While the Dallara chassis showed promise on the Ohio road course, handling on Indy’s high-speed oval proved problematic. Top speeds for Franchitti and Kanaan fell between 208 and 216 mph. But last year’s Indy qualifying speeds ranged from 227 mph down to around 215 mph, and race day speeds were between 218 and 225 mph.

Franchitti and Kanaan both noted that the new chassis was loose (oversteer) entering corners, and headed for the track wall when coming out of the corners (understeer).

Following another round of testing on an oval — Auto Club Speedway in Fontana, Calif. — IndyCar driver Scott Dixon commented that the chassis was “a bit of a pig,” meaning he was concerned about the rear-weight distribution and excessive aerodynamic drag that hurt handling.

Dallara immediately began making modifications. A subsequent test showed modest handling improvements, thanks to a lightened gearbox. Nearly 9 lb were shaved by transmission manufacturer Xtrac, Indianapolis. And weight distribution was fine-tuned by adding 26 lb of lead ballast to the front of the car.

After this last test, all parties involved in the chassis’ development — IndyCar, Dallara, Chevrolet, Honda, and Xtrac — began a concerted effort to address handling issues before the 2012 season. Led by Will Phillips, IndyCar vice president of technology, the group listened to feedback from IndyCar drivers and engineers who suggested using a rearward-swept suspension to shift chassis weight forward.

Originally expected to weigh 1,380 lb, the new Dallara chassis tipped the scales at close to 1,500 lb. because vendor-supplied items were above their specified weights. This led to the new chassis’ unexpected rearweight bias.

IndyCar agreed to shift the car’s 41/59% (front/rear) weight distribution closer to 43/57. And Dallara agreed to design and build a new suspension, which moved the front wheels back by 2 in. and the rear wheels back by an inch, helping make the car more stable. To address excess drag and low speeds, Dallara started working on a new oval aero package which would change the floor, sidepods, and wings.

Full testing and more tweaks
The first of the new generation of IndyCar race cars shipped from Dallara’s $7 million motorsports facility to teams in midDecember 2011, with the original suspension components. The updated suspension was not available in time. Though the chassis was first called the IndyCar Safety Cell, Dallara renamed it the DW12 in late 2011 in honor of twotime Indy 500 champion Wheldon. He had spent much of the summer of 2011 honing the race car and then died from head injuries sustained in a 15car pileup in the October 2011 IndyCar finale in Las Vegas.

In light of Weldon’s tragic end, the safety of the DW12 received a greater focus. So from the outset, the chassis was designed for driver safety, with more room for the driver and padding in the bottom of the car that better positions and protects a driver’s head, legs, and back. Ironically, though, the car’s wider floor and sidepods that extend to the outer edge of the rear tires were among the factors contributing to the chassis’ handling problems and instability.

Another significant safety change from Dallara’s IR05 is the DW12’s wheel interlock that lets cars run side by side, yet limits the risk of wheels locking and sending the car airborne, which is what happened to Wheldon’s car in Las Vegas.

With a little more than two months before the start of the 2012 season, IndyCar Series teams took to central Florida’s Sebring International Raceway in January for the first real DW12 roadcourse tryout. Eleven drivers, running Chevrolet, Honda, and Lotus power, took to the 1.8mile, 10turn track to continue development of the chassis.

“Everyone was down on the car and worried about speed the first couple of months,” said Ben Bretzman, team engineer for Sam Schmidt Motorsport. “It’s just been so long since we’ve had new cars. There are a lot of people in IndyCar that never had a new car. So we’re all learning about the new car and what it takes to get up to speed. Everyone will be learning all year because the fundamentals of this car are much different than the old car.”

The mid-January test was the first time teams could run their own cars because the testing blackout was lifted,” Phillips said. “Dallara was there to support the tests and take feedback. It will take teams a while to get used to the switch from steel to carbon brakes in particular.”

“Everybody has questions about the new car,” said Target team owner Chip Ganassi. “I think teams have to remember that after the previous car was developed, it took two or three years to get it right. With a new car, you don’t set new lap records right out of the box.”

Also, in mid-January IndyCar and Dallara participated in two days of full-scale wind-tunnel tests at Windshear in Concord, N. C., to collect data on ways to boost aerodynamic performance on ovals. The results were encouraging and showed that the DW12 can and should meet last year’s speeds in the 2012 Indy 500, the DW12’s first true test on an oval track in race conditions.

“We showed that aerodynamically the car was limited to 218.4 mph, so the drivers and teams did a good job of reaching its potential,” Phillips said. “We then compared the production car, which differs slightly from the prototype in that it has different mirrors, rear-wheel fairings, and chassis construction, and better integration of the Zylon side-intrusion panels.

“Basically, the car is more slipperier through the air. That lifted the speed as the car was run,” he says. “We then looked at how we could improve the car’s aerodynamic forces. We improved the aero set-up, rebalanced the car, and then put on some aero-development parts. Using a nominal assumed horsepower of 575, the car is easily capable of 225 mph. Mechanical changes that have been carried out will need to be proven in practice, but we expect to hit the targeted speeds.”

At the February “State of IndyCar” address, drivers continued to weigh in on car development.

“We’ve had the same car for six or more years,” said Dixon. “So it’s nice to have something new, sit in something different. It reacts totally differently. There were a few teething problems here and there, but that’s to be expected. The engineers and teams have had to work a little bit harder because there’s a lot of unknowns. But for all of us, it’s very exciting. And with three new engine manufacturers, I think it will be exciting racing.”

IndyCar conducted two more open tests for all teams in March at Sebring and at Texas Motor Speedway. Further development was left to individual teams and their engineering staffs, leading up to the season-opening Honda Grand Prix of St. Petersburg on March 25.

DW12’s first oval-track race will be the Indianapolis 500. When asked about oval-track results of the car’s windtunnel tests, reigning IndyCar champion Franchitti was still a bit skeptical.

“We’re going to have to go on the track and back that up,” he said.

“No one can claim we haven’t made mistakes along the way. We have,” said Bernard. “But our only goal every single day with IndyCar is to improve it and make it stronger. We have fantastic drivers, we have outstanding teams, and partners willing to invest millions into the series to help it thrive and ensure IndyCar will be here for another century.”

© 2012 Penton Media, Inc.

About the Author

Jessica Shapiro

Jessica serves as Associate Editor - 3 years service, M.S. Mechanical Engineering, Drexel University.

Work experience: Materials engineer, The Boeing Company; Primary editor for mechanical and fastening & joining.

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