|From Fantasy to Reality: Completion of the 0X Engine
The team faced difficulties right from the start. In fact, they had to prove that oval pistons, cylinders, and piston rings could actually be made. They also had to find a manufacturer that could help them do it.
Finally, the team commissioned the production to an associate company, Honda Metal Technology, located in the city of Kawagoe, Saitama Prefecture. Development went forward there, but the process was not entirely free of problems. Since in an oval piston a semicircular curve has to merge into a straight line, continuous curvature could not be maintained and edges were created along the piston. This made machining very difficult. Similar problems were found in the honing of the cylinder's inner diameter, and many hours were spent in production.
The team members in charge of engine design had their own private concerns, but spirits were high in the NR Block, where team personnel worked eagerly to prove that their engine was more than a fantasy.
In July 1978, three months after the start of production, the NR team finally completed a dual-valve head, 125-cc single-cylinder engine prototype, which they named "K00." Contrary to the team's concerns, the engine turned properly on the bench tester. With renewed confidence, the NR Block continued its efforts and the following October completed an eight-valve head, water-cooled, single-cylinder engine, the K0. Each day was spent making a prototype, testing it, modifying the specifications, and testing it again. Repeated testing revealed that the oval-piston design would cause problems at speeds in excess of 10,000 rpm, due to poor machining accuracy and the loss of durability. Regardless, the team members knew they could not continue testing single-cylinder engines indefinitely.
The NR Block was in fact developing a 4-cylinder engine commensurate with the testing of single-cylinder units. In April 1979, they completed a 4-cylinder V-engine called the "0X," which was to become the heart of the NR500. During the bench test, the engine produced 90 horsepower, making it clear that they had not yet reached their target of 130 horsepower.
The NR Block had also formed a new materials group in order to study two key problems-machining accuracy and durability. The group leader was to be Yoshitoshi Hagiwara, then chief research engineer in HGA's Third Research Block, who had been collaborating with the development team since the early stages of development. One of the group's key responsibilities was to collect the engine parts broken during testing and investigate their causes of failure. It was a tedious task in which it was often necessary to go through the pieces of several parts one by one and divide them into rings, valves and so forth. The group even studied new materials such as carbon and complex high-tech materials, along with enhanced manufacturing techniques that might be used to build parts which could withstand high engine revolutions. Ultimately, these efforts were fruitful, producing notable improvements in durability.
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