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Here's the story:
lllustrated Corvette Series No. 53 - 1973 XP-895 All-Aluminum
Experimental Corvette
Despite
the dark clouds on the automotive horizon in the early '70s, it was a
heady time in the Corvette R&D group. The all-aluminum Corvette
was the third fully functional prototype to show up in '73.
Before carbon fiber, aluminum was the darling of high-tech automotive
development. After all, aluminum was the material of cutting-edge jet
aircraft and space craft. An aluminum bodied car wasn't a new idea,
since many European exotics had aluminum bodies, as well as Shelby's
Cobra. But an aluminum "production" car is another matter.
Like aircraft and space craft, weight was the motivator for this
feasibility study. Since the early '60s Detroit had been offering
"off-road" aluminum parts intended for NASCAR and drag racing, but
these were limited to bumpers, fenders, hoods, doors, and mounting
hardware. Mass producing an entire car body would require many assembly
and durability considerations. But the prospect of reducing body weight
by 40 percent was very appealing.
Using the same chassis and basic body shape of the 2-Rotor Corvette
prototype, Reynolds Aluminum used their new 2036-T4 allow to make this
all-aluminum Corvette. Except for the bumpers, tires, and interior
parts everything else is aluminum. Chevrolet supplied stress analysis
and Reynolds sorted out everything else. The main constraint was that
the body would have to be spot-welded like a production car. To
compensate for aluminum's lower modulus of elasticity, many of the
parts and attaching flanges had to be thicker. Two-part epoxy was also
used for added strength and to eliminate crevices that would trap salts
and dirt.
The Reynolds car had minor body differences from the 2-Rotor prototype
and used a 400-cid small-block mated to a Hydro-Matic automatic
transmission. Side-by-side, the Reynolds car weighed over 400 pounds
less than the steel bodied 2-Rotor prototype. But weighed against the
Corvette's sales success of the early '70s, GM was in no mood to make
an aluminum Corvette.
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