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| Test equipment in Oguchi's laboratory at Shibaura Institute of Technology. The development team's research made real progress, thanks to the drum-type bench tester. |
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At the Sixth Research Block of the Wako R&D Center, Shoichi Sano and Osamu Furukawa were deep in discussion as to how they should approach the concept identified in the brainstorming session.
The idea, after all, had not yet been approved as an official project theme, so the financial and human resources available to them were quite limited. Moreover, several projects were running concurrently at the time, making a proper development team even harder to come by. Data, too, was hardly sufficient, given the uniqueness of such a concept. For example, although they wanted to modify existing models in order to construct test cars, they didn't even know whether the front and rear wheels should turn in the same direction or in opposite directions. There were so many questions, due to the fact that a steering system based on four wheels would allow considerable flexibility in control. The key question was where to start.
Sano and Furukawa decided to build a theoretical model for the four-wheel steering system, believing it would help define the fundamental concept before the actual research started.
"It was interesting just mulling over ideas in my head, simply because it was such a new system," Furukawa recalled. "Nobody had ever driven a car with such a system before. I had fun just imagining myself driving it. I have to admit, it was something of an obsession. I was always thinking about the 4WS system, even when I wasn't working."
The theoretical model created at this stage eventually led the pair to the basic mechanisms, providing a dramatic motivation in the development of the 4WS system.
Four-wheel steering, however, wasn't an unknown concept.
Daimler-Benz had already developed four-wheel drive, four-wheel steering vehicles for the Forest Service. Their rear wheels were designed to turn in the opposite direction to the front wheels so that the vehicle could make sharp turns along narrow mountain roads. However, the specification had yet to be adapted for use in mass-production units. Even though it was effective in mountain driving, maneuverability was less than perfect elsewhere. Consequently, these cars occasionally had stability problems while being driven on Germany's famed Autobahn.
A special committee under Japan's Ministry of Transport once examined the merits of a vehicle whose rear wheels could turn in the direction opposite that of the front wheels, as part of discussions regarding the safety of large trucks. There was mounting public concern at the time regarding the danger of transport vehicles, particularly in instances where wide left turns were called for. The committee, too, concluded that a vehicle with four-wheel steering would be less stable at high speeds.
Furukawa's theoretical model substantiated these concerns, concurrently defining a direction as to how Honda should proceed. The fundamental principle identified by his model was that the front and rear wheels should turn in the same direction at high speeds and opposite directions at low speeds.
"We used figures to express an ideal car," Furukawa said. "It was one that could make quick, sharp turns, for which we made the proper calculations. And this was the answer we came up with."
The ideal control method for the four wheels was examined from a broader perspective, and those findings were then reflected in a concrete, theoretical model. This approach successfully outlined a 4WS system that was unlike anything before it. The principle mechanism won a basic patent in 1978, which further propelled Honda's development of the 4WS system. |
