Stingray – From Design to Reality

Corvette Stingray Design
By Peter Cheney, Globe and Mail
You have to be a certain type of person to spend years obsessing over the design of a carbon fibre torque tube or a ducted fender vent. Fortunately, Tadge Juechter is that type of person. So is Harlan Charles.
When the new Corvette C7 Stingray won Car of the Year this past month, few realized how many hours Juechter, Charles and their fellow engineers on the Corvette team had put into the car, starting when George W. Bush was still president. Behind the Stingray were sleepless nights, money troubles, wind tunnel sessions, paper sketches, clay mockups and a clapped-out 1970s motorhome known as The Fish Bowl.
Although we think of modern car design as a bloodless, computer-driven process, the old-fashioned, entirely analogue process that is human judgment still plays a critical role. Hence The Fish Bowl, a wheezing, sun-bleached old RV with oversized windows kluged onto its sides.
Parked behind GM’s design centre in Warren, Mich., The Fish Bowl serves as a viewing station when designers and engineers want to view their new creations outdoors in the cold light of day – like countless cars before, the C7 concepts were rolled out into an area known as The Patio, then studied from The Fish Bowl to see how they looked. “It won’t do more than a few miles an hour,” says Charles of The Fish Bowl. “But it does keep you from freezing to death.”
The birth of a car begins long before its public unveiling. The roots of the new C7 can be traced back to 2007, as GM suffered through its darkest hour. The company lost $38.7-billion that year, crippled by falling sales and staggering costs. More than 70,000 workers went on strike. Bankruptcy loomed.
Even as GM sank, Juechter, Charles and the design team had to focus on the future, and on creating a car that could help resurrect the company they loved. “It was a scary time,” says Charles, who has spent more than two decades at GM. “But the economic problems got us focused – we knew there was no margin for error.”
The Stingray began as a series of discussions and sketches. GM designers and artists from around the world sent in ideas about how the new car could look. Juechter and his engineering team, meanwhile, began framing the outlines of a chassis with features that would make the C7 excel on both the racetrack and the highway – a high-powered V-8 motor, rear-mounted transmission and a shining aluminum frame that looked like something out of a Terminator film.
By late 2009, the team had built a series of 33-per-cent-scale mockups that allowed them to see what the various styling concepts looked like. Then a handful of the best designs were rendered as full-scale mockups. In the old days, mockups were hand-carved from clay, in an industrial version of the process that Michelangelo had used to shape his statues. But the Corvette team had new technology: The designs it made on its computer screens were sent to digitally-controlled, multiaxis milling machines that carved the new car’s body out of hard foam blocks with precise accuracy. The foam was finished with a film of clay, smoothed, and painted to simulate a real car’s surfaces.
“Seeing it in three dimensions is still magical,” says Charles. “You see it emerging, like a sculpture.”
Good automotive design calls for a masterful blend of form and function. The new Corvette had to look good, but it also had to meet a set of key performance parameters – the body had to fit around the mechanical components, develop downforce for the race track and fit two full-sized human beings and luggage. Plus, the top had to be removable, which demanded a super-strong frame design to cope with the loss of a key structural element.
“The Corvette is a hard car to design,” says Charles. “It needs to have credibility. It can’t just be a design exercise.”
Juechter and his team spent months working on details like cooling ducts for the massive rear brakes, and the torque tube, a shaft that transmits power from the V-8 engine to the Stingray’s transmission, which is mounted in the rear to optimize weight distribution (this also enables the forward frame members to take a shorter path around the motor, reducing weight and strengthening the suspension).
Hundreds of suppliers were called in to fine-tune details like computer-controlled shock absorbers, carbon-ceramic brakes and the all-important interior. Although previous Corvettes had been known for their stupendous performance, they had also been criticized for afterthought interiors that resembled something from a rental car. The C7 team had to change that.
Some of the details were bedevilling. To improve fuel economy, the team installed a cylinder deactivation system that shut off fuel and spark to some of the cylinders when they weren’t needed. Although it worked well, the deactivation mode introduced resonance issues that forced them to redesign the C7’s central frame tunnel. The hood angle was tweaked to get the right combination of streamlining and traction-enhancing downforce. The team had to fight to get the steering wheel it wanted (GM had several off-the-rack models, but the C7 designers battled to get a new one tailored just for their car).
The end result of the team’s labours was presented at the 2012 Detroit car show – an executive whipped the cover off the new C7 as a rock guitarist played on the stage beside it. The crowd roared. The car was a hit. And now it’s the car of the year.
“We’re happy with it,” says Charles. “We went back and forth a lot of times, but in the end we had a great design.”
It is a great design. And all it took was six years, a few million hours of computer calculations, and a lot of inspired decisions by a team of obsessed car nuts with engineering degrees and oil in their veins. Then there was that old motorhome with the extra windows – a great car needs soul, after all.