01
The 47 Rotary Samurai
At the wish of company president Tsuneji Matsuda, Yamamoto was told to devote himself to developing the rotary engine, and the following month became head of the Rotary Engine Development Department. The 47-member development unit that gathered called itself the "47 Rotary Samurai," after the 47 ronin of Ako. Behind it was a sense of crisis that, under the Ministry of International Trade and Industry's plan to reorganize the auto industry, Toyo Kogyo might be swallowed up by another company. Even as his health suffered to the point of a perforated stomach ulcer and teeth falling out, he did not give up on development, and four years later, in May, the company launched the Cosmo Sport, which put the Wankel rotary engine into practical use.
02
The devil's claw marks
When the prototype rotary engines were run, wavy wear appeared on the inner wall of the rotor housing. These "chatter marks," known as the "devil's claw marks," came from the apex seals rubbing against the housing. As materials from cow bone to precious metals were tried without making them go away, Yamamoto suspected the seals' natural frequency was the cause and came up with "cross-hollow" seals, with holes drilled through them lengthwise and crosswise. Still not satisfied, the team joined with Nippon Carbon to complete a seal made of carbon powder impregnated with aluminum, and the chatter marks disappeared completely. The Cosmo Sport's 10A went into the world with these seals.
03
A single design sketch
The Cosmo Sport's shape began with a single design sketch drawn by Heiji Kobayashi, then a young in-house designer. President Tsuneji Matsuda is said to have liked it and ordered, "Go with this." Because the body was so flat, there was no room to fit a conventional suspension, so the rear wheels used an unusual De Dion setup. The body panels were welded at the seams and then smoothed by hand, finished as if made from a single sheet.
