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| A sketch of the NSX’s exterior, with its sleek profile based on an F16 fighter
jet. |
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Prototype I was completed in mid-1986, representing
the team’s first construction using the Milky Way diagram. At this stage,
they were considering both sheet steel and aluminum as potential body materials.
Of the two, steel sheet was less favored, since it would make the target running
performance of a midrange, F-1 class car more difficult to achieve. Moreover,
to counter the added weight a larger, heavier engine would have to be used, thus
pushing the car right out of the midrange category. Sheet steel would also be
a liability in terms of the car’s purpose, which was to break from the conventional
image of a sportscar as a compromise in comfort and safety for the sake of superior
slalom statistics. Of course, the team was planning to furnish the car with cutting-edge
accessories and devices such as power windows, full-automatic air conditioning,
traction control and antilock brakes systems (ABS). To accomplish this, however,
the weight of the vehicle would have to be minimized. Thus, it was decided that
the NSX would have the world’s first all-aluminum, monocoque body.
No other atuomaker had yet to build a car primarily of aluminum, however, even
though the material was pollution-free and in abundant supply. It is said that
among the mineral resources the amount of estimated aluminum reserves is three
times that of iron. Moreover, aluminum has one-third the specific gravity of iron,
is resistant to corrosion, and is much easier to recycle. Despite such powerful
advantages, the material has several drawbacks, particularly a high cost and proportionately
higher technical requirements in molding and welding. But the development team’s
greatest hurdle was the need to build a dedicated plant simply to produce the
car’s aluminum body.
The project required that the development team make frequent trips between the
R&D centers at Tochigi and Wako. During one such trip, aboard the Shinkansen,
they realized that the bullet train was itself made of aluminum.
Aluminum has proved very adaptable to the Shinkansen, in fact. So, the team members
saw no reason why it couldn’t be used for the body of a sportscar. And though
there might be problems along the way, they made a promise then that they wouldn’t
shy away from the challenge of creating a car for the new era.
Kobe Steel and other material suppliers appeared somewhat perplexed at the development
team’s request that they collaborate in the creation of an all-aluminum car
body. Because aluminum is prone to buckling during stamping work and is difficult
to weld, its use in mass-production cars was limited to a relatively small assortment
of parts. The suppliers were confused by the team’s decision to make the
entire body out of aluminum, and doubted the seriousness of Honda’s intentions.
However, the staff offered their earnest explanation to the skeptics, saying they
needed an aluminum body to build their new sportscar. It was the kind of honest
enthusiasm that eventually led the suppliers to wonder, why not?”
Various types of aluminum were considered, but the suppliers selected the 5000
and 6000 series. The former was already being used in the automotive industry,
while the latter had relatively high strength despite its lower formability. Still,
various enhancements would have to be performed. The supply company personnel
in charge of development spent many days anguishing over the situation, working
feverishly to meet a series of conditions stipulated by Honda in order to ensure
productivity in stamping, forming, welding, coating and other processes. In fact,
the hours were so long and arduous that toward the end of development they would
often spend the night right in their factory.
Problems inevitably arose, and with them came headaches and delays. In particular,
processing of the side sill was proving difficult, since aluminum, unlike iron,
wasn’t suitable for deeply drawn press work. Therefore, a new forming process
was devised whereby the aluminum was heated to 600 degrees, poured into dies,
and extruded from the dies while it was being drawn. But this system created a
super-strong, highly rigid honeycomb frame, and this technique ultimately became
the assurance that their all-aluminum body would satisfy the rigors of high performance
on the open road.
A selection of five aluminum alloys was eventually incorporated into the vehicle.
This thorough attention to detail—along with numerous other efforts—soon
led to a body-weight reduction of 140 kg and nearly 200 kg for the entire car,
as compared to a steel-bodied equivalent. It was quite an achievement in the eyes
of the material suppliers, too, who were amazed to see just how much of a car
could be made with aluminum.
Concurrent with the material development of mid-1986, the development team collaborated
with the Suzuka factory in building an aluminum-bodied prototype CR-X. Performance
tests were conducted with the prototype, then the results and problems they identified
were examined to determine whether it would be practical to build a car with an
aluminum body. Next, the team studied the basic frame structure of an aluminum
body for a midship sportscar using Prototype I. Several test drives and crash
tests were carried out using the prototype, in order to obtain thorough verifications
covering everything from rigidity to repair techniques. The results were reflected
in Prototype II, which was much closer to a final product. With Prototype II,
interior accessories, equipment, passenger comfort and environmental adaptability
were considered as part of the car’s overall performance picture. |
