Four Score

Also from Issue 40

  • 2009 C6 ZR1 debut
  • 1965 big block at Goodwood Revival
  • Comparison Test: 2007 vs. 2008 Z06
  • 2009 Indy Pace Car
  • Saddle Tan Split-Window
  • Rare Aztec Gold 1998 coupe
  • Market Report: C4
  • CRC’s C1-look C5 convertible
  • Callaway B2K at Bloomington
  • How-To: C2 radiator support repair
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While on the subject of crash testing, Jaeger pointed out another area where computing power helped shaped the nascent C4. "Most of the impact energy of a front barrier crash has to be taken by the front frame rails. We ended up making these of HSLA, but very early in the program we started with a special state-of-the-art computer analysis which, unlike finite element modeling, can deal with large-scale, non-linear deflections of the metal and can predict the crush modes of complicated shapes, like the front rails. In essence, the analysis told us where these rails would bend in a crash, how they’d crush, and at what (loads) the crushes would take place. Furthermore, the computer was telling us how much energy was being absorbed along the way.

“We followed up this work with a program using half-scale models. We’d barrier-crash them to confirm what the computer was telling us, (running) these tests with actual half-sized Corvettes. They were accurate in every significant structural detail. By testing various de­signs this way, we could get the basic barrier performance where we wanted it before we ran our first test with a full-sized prototype.”

NEW SUSPENSIONS AND BODIES

The next major task, again with the heavy use of computer modeling, was developing the new car’s suspension. Brian M. Decker was in charge of the model’s chassis, which Chevy defined to include the suspension and driveline. “One of the suspension system’s key features,” he explained at the time, “was the aluminum content. Both front and rear suspensions are all-aluminum, which is new for GM. We’d never done anything like it before. In fact, neither had any other domestic passenger-car manufacturer, so far as I know. There are a few imports, like the Porsche 928, that have suspension parts made of aluminum, but most of those parts are cast. We didn’t want to cast ours because we feel castings really aren’t pro­per for suspension components. Clearly forgings are better. They have more ductility.”

The production ‘84 Corvette would contain about 375 pounds of aluminum—mostly the alloy 6061-T6—versus 200-odd in the ’82 model. Decker noted that "…the reason for all this aluminum…is that we were going after light weight. The ’84 front suspension represents a 58% weight saving over the ’82 Corv­ette’s. Less unsprung weight improves not just ride but wheel control and handling as well.

“We wanted maximum performance out of the 1984 car, and certainly weight is important for that. We wanted the lightest vehicle we could come up with. We wanted a car on the road, even with the V8 engine, that weighed under 3000 pounds.”

Simultaneously, Robert A. Vogelei was creating the technology behind the body that would ride on the uniframe and suspension. Vogelei joined the Corv­ette engineering team on April Fool’s Day ’63 and had taken part in developing the car ever since. By the time I first talked to him, in February ’82, he was responsible for all Corvette body engineering, and his expertise had earned him the affectionate nickname “Mr. Plastic.”

A number of points would differentiate the new Corvette’s body from those found on previous models. Its panels would be made out of non-shrinking, low-profile plastic resin, not conventional fiberglass; there’d be no more ex­posed bonding joints, part of an effort to give better perceived quality and reduce assembly time; the bonding adhesives would be urethane-based, not polyester-based; and all outer panels would get molded-urethane coatings for smoothness and durability.