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Corvette From the Inside
Corvette From the Inside

by David R. McLellan
Price: $49.95

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(10 page excerpt)

The Corvette is Born1
The ZR-1 was made for French roads. Winding and twisting through historic valleys, many of these same roads are used for the Monte Carlo Rally. ALL TOO QUICKLY, THE STEEP CANYON carved out of the French Alps opened up and we were in the quaint bobsled resort village of Villard-de-Lans. In a blink we were out its other side and heading down into the Gorges de la Bourne. Clinging to the face of the mountain, the ZR-1 twisted and turned down another wild road, a road that in the dead of winter is used for the Monte Carlo Rally. My exploration of first and second gear acceleration, braking and handling seemed to go on forever as the gorge continued mile after mile.
The date was March 8, 1989, and I was on the new car press introduction of the 375hp, 180mph ZR-1 Corvette en route from the Geneva auto show to Carcassonne, in the South of France. The earliest production cars had been completed just in time for the introduction and subsequent press trips. Even though I was Corvette Chief Engineer, this was my first real drive of the car that I will always think of as "King of the Hill." It was also one of my best memories of my 17 years as Chief Engineer.
The Heritage Of The Corvette
Every production Corvette that followed the 1953 Motorama car has been evolutionary, building on the version that came before it. One year might see minor adjustments to the body or chassis, while another year would see the introduction of an all-new engine. Not only was the ZR-1 a major refinement and development of the 1984 Corvette, it owed its very existence to each Corvette that preceded it. Even today’s C5, which reached production after my tenure as Corvette Chief Engineer, owes much to both the ZR-1 and its antecedents.

The Corvette was originally introduced as part of General Motors Although my personal Corvette journey began in 1974, to put the tale in context I have to start at the beginning--to even before the Motorama show car took center stage in 1953.
The production Corvette was released just 68 years after the invention of the automobile. In those intervening years, between 1885 and 1953, the automobile developed from buggy to serious transportation. Roads that hardly existed at the turn of the twentieth century evolved into intricate networks, and automobile technology advanced to produce road racing cars capable of 200 mph.
The heart of the XK120 Jaguar was the 160bhp 3.4 liter, six-cylinder double overhead cam engine that became the basis for the C and D Type race cars and the E Type sports car. In the beginning, all automobiles were sports cars by default. To go anywhere by automobile was a great adventure. As roads, the infrastructure and automotive technology developed over the next two decades, the automobile became a dominant mode of personal transportation, and the sports car became a specialized product. The advancing technologies transferred from auto racing, aircraft racing, and military aircraft design served to redefine the sports car. So by 1953, enthusiasts who were steeped in the mystique of the sports car and who saw the first Corvette on the Motorama stage, questioned whether an American sports car, particularly one produced by Chevrolet, could meet their expectations. Knowing what the sports car enthusiast knew and what the expectations for a sports car were in 1953 will help us to understand what happened when the Corvette was introduced. The MG TC was the quintessential traditional sports car. Its roots are to be found in the first cars of the twentieth century with their flexible frames, stiff suspensions and modest performance.
When the Corvette was first shown to the public, it was instantly subject to comparison to the leading contemporary sports cars--the Jaguar XK120 and the MG TC. These two cars were vastly different in both performance and appearance, but they were both great fun to drive and exciting to look at. To some degree though, the Corvette was at a disadvantage because the United States had very little heritage of nimble, responsive sporting automobiles, without harking back to the Edwardian days of American motoring with cars such as the Stutz Bearcat and Mercer Race-A-Bout. But in 1953, very few drivers or automobile enthusiasts in the United States had experience with these two legendary automobiles.
The 646bhp Mercedes-Benz W.125 was nearly invincible during the 1937 Grand Prix season, and it either introduced or included virtually all of the important elements of the modern sports car.
Without a recent past of small sporting cars capable of carrying two passengers, American automakers and designers had no choice but to look across the Atlantic. In Europe, marques such as Mercedes-Benz, Alfa Romeo, Aston Martin and scores of others had a history of building fast, responsive and exciting automobiles, some of which were equally at home on road or track. Detroit was slow to copy such innovations as double-overhead cam engines, fully independent suspensions and disc brakes. But at General Motors, styling chief Harley Earl was more than willing to pay close attention to European trends and specific designs.
The 1938 Y-job show car incorporated elements from contemporary icons and art deco design, melding them into a car that would signal the next wave of design trends from GM.
Motorama Madness
Every year since 1949, a road show extravaganza called Motorama traveled around the United States, showing off the future as envisioned by GM. In each of those years, GM Styling had contributed show cars to the Motorama stage. Most of those cars were larger than life and were an evolution of Earl’s 1938 Y-job, which incorporated influences from such styling icons as the Auburn speedster and the Cord 810. GM’s stylists were always working to make their cars look long, low, and sleek.
The Le Sabre show car drew its inspiration from the military jet planes developed after World War II.
GM’s show cars of the late 1940s and early 1950s drew their inspiration from the military airplanes of World War II and the early jet planes being developed. These cars sported tail fins and intake and exhaust nozzles, themes that the designer used to express speed, power, and aggression. The trend was exemplified by show cars such as the Buick XP 300 and the Le Sabre. Looking back, it is clear that they were a product of their time, not a portent for the future.
Harley Earl, GM’s first head of styling, was himself larger than life. Tall and imposing, he drove his stylists with tactics of fear and intimidation. As Vice President of GM Styling, he watched his own boys grow up taking a strong interest in the sports cars of the 1950s such as Jaguars and Ferraris. It struck him that he could design sports cars too. Early in 1952, Earl decided that his next Motorama show car would be a sports car. He made some sketches of what he thought it should look like and then tapped young engineer-designer Bob McLean--just hired from Cal Tech--to flesh out his ideas and turn them into a real car. Earl’s original sketches have been lost, so we don’t know exactly what he defined for McLean, but we do know what they produced--the first Corvette.
Trained in his family coach building business, in his three decades as head of GM’s Art and Color Section--later GM Styling--Harley Earl turned GM into a design powerhouse. Bob McLean was later described by Chuck Jordan, who worked for him and later went on to be Vice President of GM Design Staff, as "very creative and interested in the architecture of the automobile--he knew engineering." McLean later contributed to the Sting Ray Corvette and was responsible for the radical turbine-powered Firebird concept cars.
Earl organized the Corvette project in absolute secrecy, even keeping it away from his other stylists. He set up his studio on the third floor of Plant 8, an old Fisher Body factory about a mile from the General Motors Building where his other studios were located. To deflect the curious he gave the car the code name Opel, the name of GM’s German subsidiary.
Bob McLean, fresh from California, was very familiar with the sports car racing scene that was already developing there and knew what it took to make a sports car. He turned his assignment and Harley Earl’s sketches into what he thought a real sports car should look like. As the project developed, he and Earl saw an opportunity to produce a show car that could become a sports car for sale to the public.
The car they designed broke the pattern of the larger-than-life show cars that had been coming from Earl’s studios. McLean’s car was scaled to the people who rode in it and to the mechanical components that would make it a real car. It was at least a foot lower than contemporary cars. With the top down, its form was a simple "one box" design dominated by its flowing fender, its low and wide grille, and a hood that started lower than the fender.
The unsung hero of the Corvette, Bob McLean, designed the car under Harley Earl’s direction. McLean was also responsible for the radical turbine-powered Firebird concept cars.
Conventional wisdom credits the XK120 Jaguar, first shown in 1948, as being the inspiration for Earl’s new show car. It was certainly the inspiration for the chassis, but it couldn’t have been the inspiration for what Earl’s car would look like. The XK120 Jaguar was itself a design in transition from the classic sports car. The dominant form of the Jaguar was still its long, tall hood which flared into the cockpit and then fell to the road at the end of a long sloping trunk. The flowing cutaway fenders were still tacked onto the body. The influences behind Was the XK120 Jaguar the design inspiration for Earl and McLean’s new car? I don’t think so. The Jaguar evolved from designs of the 1930s, which had yet to eliminate separate fenders attached to a body. Harley Earl and Bob McLean’s new car are to be found elsewhere.
Since the late 1930s, the Italian bodybuilders had been experimenting with new aerodynamic forms for the sports car. In 1937, Touring designed the special-bodied BMW 328 that would become the inspiration for the XK120. In a series of unplanned steps, cars in general--and sports cars in particular--were becoming lower and wider, with the fender line gradually becoming totally integrated into the form of the body.
The final expression of this search for a new form was the Cisitalia 202. The initial body design came from aeronautical engineer Giovanni Savonuzzi in 1947, with limited production coupe, convertible, and spider designs refined and built by Pinin Farina. Although production was limited, it is likely that Harley Earl saw a Cisitalia 202 early in its life. If he hadn’t seen the Cisitalia at a major European salon or through his friendship with Batista "Pinin" Farina, it is likely he would have seen one in the United States, where it was imported by Max Hoffman. Earl also would have been aware of the car’s inclusion in the "Eight Automobiles" exhibit at New York’s Museum of Modern Art in 1951.
The low, integrated form of the Cisitalia set it apart from its contemporaries and warrants a detailed comparison with the Corvette. One good look clearly supports the theory that the Cisitalia Spider Nuvolari roadster influenced Earl and Bob McLean as they worked out the lines of their first Corvette. Both the Cisitalia and the Corvette were low and wide and featured low hood lines and a fender line fully integrated into the body. Both had front fender lines, which fell only slightly as they The design similarity between the 1947 Cisitalia 202 Nuvolari roadster and the Corvette (conceived in 1951) are striking even down to the toothed oval grille and the stone guards over the headlights. Two features added by Earl and McLean were the wrap-around windshield and fully-disappearing top. defined the door and then flowed into the rear fender that kicked the line back up again. Other similarities included wide, oval radiator grilles comprised of multiple vertical bars and head lamps integrated into the leading edges of the fenders and protected behind mesh grilles. Though often shown with wire wheels, the Cisitalia 202 also had a streamlined wheel cover detailed with radial slits--similar to the one later used on the Corvette.
GM powerhouse Ed Cole was the consummate engineer--even as president of the giant automaker.
Cole Adopts The Corvette
Cadillac, GM’s luxury car division, had recently been transformed by its Chief Engineer, Ed Cole, who led the development of the new V-8 engine, automatic transmission, power steering, and air-conditioning. Souped-up versions of Cadillac’s new V-8 engine were finding their way into Allards and early Cunninghams. Ed Cole often drove to work in his Cadillac-powered Allard or in his XK120 Jaguar. Unfortunately for Cadillac, Cole had just moved to Chevrolet and was in the midst of the most monumental task of his career, turning around GM’s low-price, high-volume division. Chevrolet was the most staid and old-fashioned of GM’s car divisions. Yet Chevrolet was a famous name with a stellar past. William Durant, ousted as GM President, started Chevrolet with racing driver Louis Chevrolet in 1912. The intention was to produce a car to compete with GM’s low priced entries, but Durant was so successful that he was able to buy GM and, together with Chevrolet, form the modern General Motors Corporation. By the late 1920s, Chevrolet had overtaken Ford to lead the low-price market. But by the early 1950s, Chevrolet was in decline and due for an overhaul.
Ed Cole was well on his way to turning Chevrolet around when Harley Earl showed him his Project Opel in May 1952. Cole was excited and wanted the car to help to create a new youth and performance image for Chevrolet. The renaissance Cole was planning for 1955 was still a year and a half away from its public unveiling. But if he could assemble this sports car quickly, using available Chevrolet components, he could get out in front of the new 1955 V-8-powered Chevrolets by at least a year.
Cole convinced his boss, Chevrolet General Manager Tom Keating, that they should produce the car. Together with Harley Earl, they tried to convince GM President Harlow "Red" Curtice that their show car should be produced. Curtice was not so easily convinced. He told them not to go ahead with the production project until they had public feedback from the Motorama show, which was still six months away.
Maurice Olley’s work on suspension and handling and Chevrolet R & D’s development of the plastic car body formed the basis for the first Corvette. Confident he would get a positive public response, Ed Cole wasn’t about to wait for the Motorama presentation to start the production design. Ever the risk-taker, Cole ignored Curtice’s cautious direction and forged ahead. In any case, Cole knew he could hide the details in his massive Chevrolet budget, at least until he had to pay for major tools.
Harley Earl’s vision was to create an affordable sports car. Once the layout was defined, Chevrolet would select components of proven reliability and modify them only as necessary to fit the styling theme. There was no time to do more.
Ed Cole was fortunate to have Maurice Olley heading Chevrolet’s Research and Development Department. Olley began his career at Rolls-Royce and in 1930 joined GM, where his seminal work on vehicle handling led to the adoption by GM of SLA (short-long arm) independent front suspensions on all its cars in 1935 and 1936. During World War II, Olley coordinated the manufacture of the Rolls Royce Merlin aero engine in the United States by the Packard Motor Car Company. Back at GM after the war, he was working on low-investment, inexpensive plastic body panel technology in addition to his favorite suspension projects. Cole asked Olley to work with Bob McLean at Styling and to design the production Opel.
Still without an official name, the Opel project was known within Chevrolet by its EX-122 experimental code. It was an opportunity for Maurice Olley’s R & D department to demonstrate its packaging skills, knowledge of ride and handling, and skill at fabricating a body in the new fiberglass reinforced plastic material with which they were experimenting.
To fit the Chevrolet’s six-cylinder engine under Bob McLean’s hood and to approach a 50/50 weight distribution, Olley moved the engine rearward, behind the front suspension cross-member, and lowered it to the ground-clearance line (an imaginary line six inches above the road). The Corvette’s hood was so low that the front of the engine’s valve cover had to be skived to clear it. Producing only 106 hp in production form, the straight-six was "hot-rodded" with three side-draft carburetors, a dual exhaust, increased compression ratio and a modified cam to produce 150 gross horsepower.
The production manual steering had to be modified, but there was still room to fit it under the engine. The standard Chevrolet drove the rear wheels through a three-speed manual transmission, which was shifted by levers and rods from a column-mounted lever. For the Corvette, the steering column was drastically lowered, bringing the manual shift linkage into hard interference with the engine. We do not know if Chevrolet attempted to get around this problem before they abandoned the manual transmission and went with only the Powerglide two-speed automatic--which was optional on other Chevrolet models. For both GM and the American public, the manual transmission was by now old technology, while the automatic transmission was new and high tech.
Bodied entirely in plastic, this 1952 Chevrolet convertible was GM’s first use of the new technology for automobile bodies. The body was left unpainted to expose the translucence of the fiberglass construction.
The original Corvette chassis was expeditiously produced from the Chevrolet passenger car parts bin.
The original Corvette chassis was expeditiously produced from the Chevrolet passenger car parts bin.
Packaging The Corvette
The low height of the car and the use of a conventional frame dictated a seating position with the driver sitting upright on a shallow cushion with his or her legs stretched out in front. Clearance to the driver’s seatback located the rear wheels and established the wheelbase. With the engine moved back and the axle moved forward, the much shorter distance between the back of the transmission and the axle negated the use of the Chevrolet sedan’s torque tube axle. A short U-jointed prop-shaft was used to connect the transmission to the Hotchkiss-drive rear axle, which was located by longitudinal leaf springs.
Triple carbs were the first step in transforming the 106 hp
The Corvette’s chassis was developed around a modified passenger car frame. The fiberglass body provided no structural rigidity, and was required to support only local loads such as the door hinge and lock system. The frame tied everything together and gave the car its torsion and beaming stiffness. Because the closed-body passenger car carried most of its stiffness in its steel body, the frame had to be heavily reinforced for the Corvette. The side rails were boxed and a massive cross-member was added to give the frame as much torsional stiffness as possible.
CHEVY’S POWERGLIDE AUTOMATIC TRANSMISSION GM had introduced the first Hydramatic, automatic transmission for Oldsmobile in 1939. The transmission consisted of a fluid coupling with four forward speeds automatically shifted by engaging planetary gears with clutches. This was the beginning of a major trend in GM toward automatic transmissions. These transmissions were well accepted by a driving public that was willing to pay a premium for them. Chevrolet’s version of the automatic transmission—the Powerglide—cost much less than the four-speed Hydramatic. The Powerglide used a torque converter with a complex planetary gear set that gave it two forward speeds and reverse with the torque converter effectively providing the additional ratio needed to launch the car. The front suspension was taken directly from the passenger car without changing spring rates, although the spring height was reduced to reflect the lighter weight of the vehicle. A large front stabilizer bar was added to reduce roll and to control the load transfer distribution as it affected limit-handling. The steering linkage was modified to connect with the steering box and the lowered steering column. Offered only with manual steering, the car was fitted with a big 17-inch steering wheel and slow steering--3.7 turns lock to lock--in order to make the low-speed turning effort acceptable.
With driver and luggage on board, the Corvette featured a 50/50 weight distribution, which left the car with virtually no inherent understeer. To provide the moderate amount of understeer necessary for safe and controllable handling, Olley used the rear axle. As he put it, he "gave tail to the arrow." The axle was located by its leaf springs, which were inclined in the side view so that as the car rolled into a turn, the axle yawed (steered) slightly in a direction that would straighten the car’s path or cause it to understeer. For every degree of body roll, the rear axle yawed 0.15 degrees (15 percent roll understeer). Ordinarily, this would have been way too much, but with its high roll stiffness the car kept this steer effect small enough to avoid yaw oscillation.
Standard Chevrolet brakes, completely shrouded by unventilated steel wheels and wheel covers, completed the chassis package. The car was never seriously tested as a sports car. If it had been put through trials, many of the problems inherent in the design, such as lack of brake-cooling, would have been found early and been fixed. As it was, the first attempts to race this new Chevrolet sports car ended prematurely with faded and failed brakes. Wire wheels were very popular on contemporary sports cars, not just because they looked good but because they allowed cooling air to surround and penetrate the drum brakes.
Harley Earl’s Project Opel was very secret, but not so secret that his other stylists didn’t get wind of it. Young Chuck Jordan was a summer student in one of the other Styling studios. Hearing that the studio containing the clandestine project was off-limits didn’t deter him. He stayed late one night and snuck into the Opel studio to see the car that everybody was talking about. What he saw blew him away. He was most impressed with the completely new way the fenders and the body were integrated. He particularly remembered the wire mesh headlamp detail, which caused the viewer’s eye to follow the surface of the fender rather than the notched opening of the headlight.
Chevrolet and GM Styling were excited about the car. The program was moving forward toward production even though they still had no authorization to do so. EX-122, the one-off Motorama show car, would get a plastic body. Olley’s Research and Development team also proposed fiberglass-reinforced plastic as the production body material. At the speed the team was moving, fiberglass would have to be used for at least the initial run of production bodies because steel tooling would take too long to produce.
The United States Rubber Company had been touring the automobile manufacturers trying to interest them in the use of a fiberglass and resin body-manufacturing process they were developing. Ed Cole, who always wanted to do things yesterday, agreed. By the time EX-122 arrived on the Motorama stage, it represented a fiberglass-bodied sports car that was being readied for production.
Was fiberglass ready for a production body application? Chevrolet would soon find out. There is real value in responding quickly to an idea car while the excitement of the new design is still fresh in the public’s mind. On the other hand, once the assembly line has started, one doesn’t want to stop production for a problem, particularly with the dealers primed and the public waiting with cash in hand.

NAMING THE CORVETTE

Both names and emblems are important to new cars. Chevrolet management and their advertising agency, Campbell-Ewald, got together to name the new car. After rejecting some 300 names, they gave up. Only afterward did one of the participants, Myron Scott, propose the name "Corvette." Corvette was the name of a class of fast naval pursuit ships. It also sounded good as the name for Chevrolet’s fast new car, and it started with the letter "C." Myron proposed the name to Ed Cole and the rest is history.
Until the day before the opening of the Motorama show, the Corvette emblem depicted crossed American and checkered flags. At the eleventh hour, GM lawyers rejected this commercial use of the American flag, and a flag with the fleur-de-lis was reluctantly substituted.

End of excerpt

We encourage visitors to link to this page if you’d like to share this information with others. Please do not copy this excerpt to other web sites. It is protected by copyright and represents significant resource investment by Bentley Publishers.