Also, for the composite bottom of the cockpit tub, instead of balsa wood, there’s now a lighter and stiffer foam-core sandwich. While none of these changes amounted to much individually, taken together they began to add up quickly to those 57 and 99 numbers, in a form of “cascade engineering.”
What role do the carbon-nano panels play here? Again, GM engineers found a way to decrease weight while enhancing stiffness. Normally a decrease in poundage (by lowering the panels’ density) might make them more flexible, Moss acknowledges, but not so in this case.
The carbon-nano clay’s smaller particles interlock better, “like platelets,” he says. When used in various ratios with resin and glass, the specific gravity drops from 1.5 to 1.2, while the carbon maintains about the same strength and stiffness.
03] As noted, the new Stingray chassis is nearly 100 pounds lighter than the previous desi
04] Varying the thickness of the frame allowed the engineers to concentrate stiffness wher
05] The floor panels now use a foam-core sandwich construction, which is both lighter and
Stepping back from the engineering details for a moment, it’s important to realize that GM engineers function as a “basket-weave organization,” Bailey points out, alluding not only to the team effort required, but also the interlocking design demands. Aristotle’s phrase about the whole being greater than the sum of its parts applies here, considering how individual components have to serve several different masters.
For instance, there’s one big change in the front cradle, a 5x3-inch rectangular frame that supports the control arms and shock absorbers, among other components. It also plays a role in crash protection and body structure. In the ’14 Stingray, however, this key component is made of hollow members, with solid “nodes” used where stressed components are attached.
While this innovative approach is not entirely new, it didn’t appear on Corvette until around 2005 in the magnesium cradle of the ’06 Z06, Bailey points out. Unlike casting a solid beam, hollow castings require a vacuum and a low-pressured, assisted permanent mold. The extra tooling and manufacturing required (done at DMI, an outside vendor) is well worth the extra effort, as it allows for creating intricate profiles that result in a performance payoff.
To be specific, in addition to the functions already noted, “It allows us to move more mass outboard,” Bailey explains. “If you took all of the mass on the C6’s [solid] cradle, and moved it outboard, you’d end up with too much stiffness.”
06] In a break with past practice, all ’14-up Corvette frames will be assembled in-house a
Another change involved the lower control arms, which are also now hollow, saving about 9 pounds. Besides weight reduction, there’s another benefit to this configuration. On the C6, the control arms’ bushings tended to migrate outward in high-load situations, typically during hard cornering of braking. The switch to hollow arms, along with the addition of cams, holds in the bushings more securely.
Interestingly, even though the track width on the C7 is slightly wider, the Michelin Pilot Super Sport tires are narrower than on the C6. The effect is less wind resistance, along with no penalty to (and in fact a slight increase in) lateral grip.
As for the brakes, lessons learned from the C6.R racing program were applied. The Stingray features a new “dual cast” rotor, with an inner aluminum web and an outer cast-iron rotor body. (For an in-depth look at the C7’s new binders, see “Area Z51,” in our Aug. ’13 issue.) This configuration allows for independent thermal expansion of the rotor, so it doesn’t affect hub geometry.
Also new is the elimination of drilled holes in the rotors, which can produce cracks over time. Even so, the base rotors have less mass than did the C6 units, and they feature arched slots, like those of the C6.R’s competition brakes. The calipers are now fixed instead of floating, for more-even wear, less drag, and better modulation through the pedal.
Although the base brakes are slightly smaller overall, they have 35 percent more swept area. The Z51 package has bigger front rotors, enlarged 1 inch in diameter. All of which means the stoppers on the new Stingray can bring it to a clenching halt at least 10 feet shorter than the C6.
In addition, the steering system is now at least four times stiffer (not five times, as previously reported elsewhere), largely for better feel. Bailey says these parts, taken together, tend to function like a torsional spring, causing a loss of input. By creating a more rigid connection between the column, coupling, intermediate shaft, and cradle components, the feel and response markedly improve.
07] The new BG chassis facility is truly state-of-the-art. Here, a worker uses a laser sca
As for the composite monoleaf transverse springs, those haven’t changed in a material sense, but they are now longer due to the C7’s wider track (73.9 inches, versus 72.6 on the C6). That means they also have a slightly different rate and frequency, along with a modified mounting.
“We designed the car to not take the spring loads in the shock attachment, but into the cradle instead,” Bailey explains. That’s because, as already noted about the cradle, the monoleaf springs serve multiple functions, such as providing a lower center of gravity, serving as a stabilizer bar, setting trim height, and reducing mass.
The Magnetic Selective Ride Control—what Bailey calls “Mride shocks” for short—can’t be installed in the race car, due to rules restrictions, but that’s obviously not an issue on the street. They optimize the damping of roll and pitch, especially on “low body vertical speed events.” (This expression doesn’t refer to vehicle velocity, but to the body-versus-wheel motion in a slalom situation.) “The Mride puts the body where you want it to be,” Bailey says.
Another key component that the race cars don’t get is the ELSD (Electronic Limited Slip Differential). This unit improves the traction effort of the rear tires and greatly enhances high-speed control when cornering. Basically it prevents the inside wheel from getting all the power, routing some of it to the outside wheel instead. We’ll be covering that high-tech feature in more detail in a later installment on the Stingray driveline, so stay tuned. We still have way more insider material to reveal in upcoming issues.