Section 2. Automobile Prototypes

Item 3. Prototypes of the A Engine and Model A1 Passenger Car

In May 1934, the company began creating prototypes of the cast parts used in cylinder blocks and pistons for the Model A engine, which was based on sketches of the 1933 model Chevrolet sedan engine. Creating the core1 of the water jacket, through which cylinder block cooling water flowed, proved difficult. By referencing an oil core2 that Risaburo Oshima had brought back from the United States, a cast cylinder block was finally completed in August 1934 after repeated trial and error.

The first prototype engine was completed on September 25, 1934. The parts manufactured in-house were limited to cast parts including a cylinder head, cylinder block, and pistons, while imported Chevrolet parts were used for crankshafts, camshafts, valves, plugs and electrical components.

However, when fitted in a Chevrolet truck, the prototype engine was only able to produce 48-49 hp during a driving test compared to an output of 60 hp for the Chevrolet engine. After referencing overseas documents and redesigning the cylinder head to fit the swirl combustion chamber, the engine reached an output of 65 hp, exceeding that of the Chevrolet.

Table 1-1 shows the specifications of the A engine. Units in the catalog are expressed in yards and pounds using the imperial measurement system, in line with the engine on which it was modeled.

Table 1-1. Specifications of the A Engine (1934)

4-cycle, water-cooled, inline 6-cylinder, overhead valves
35/16 in (84.1mm)
4 in (101.6 mm)
Cylinder capacity
206.8 in3 (3,389 cc)
Actual hp
65 hp (3,000 rpm)
150 ft-lbs (at 1,300 rpm - 2,000 rpm)
The 1936 Toyoda Box-Type Passenger Car Specifications attached as reference to the Automobile Manufacturing Industry Law License Application prepared on July 23, 1934 states that the A engine has "torque of 19.4 kg-m (140 ft-lbs) (at 1,300 rpm - 2,000 rpm)".

Initial production targets for passenger cars were set at 200 units per month, and prototyping was commenced. The company purchased a 1934 model DeSoto sedan in April 1934, and a 1934 Chevrolet sedan in May, as design models. These were disassembled and sketched to design the chassis and the body, and in July that year a lofted drawing of the body was completed.

Kiichiro Toyoda gave roughly the following explanation regarding his decision to model the passenger car body on the Chrysler 1934 model DeSoto sedan. It would take at least three years to build a mold for body stamping parts, and if styling trends changed during this time all the company's efforts would be wasted. As a result of investigations into U.S. automobile styling trends, it was found that the styling of the 1934 model DeSoto was one or two years ahead of other vehicles, featuring a streamlined design that was completely different to conventional models. Kiichiro predicted that this design was ahead of its time, and hence used it to model his prototype on.

The rear panel design of the passenger car body was completed in November 1934, and manufacture of stamping molds began, with guidance provided by external contractors. However, it became apparent that the molds would take one and a half years to complete. The company decided to instead manufacture vehicle bodies by hand-forged sheet metal work under the guidance of the same contractors.

Through these efforts, the Model A1 passenger car prototype was completed in May 1935, in less than two years (from September 1933). However, in addition to the cast parts3 and forged parts4 manufactured in-house, the vehicle also incorporated many genuine Chevrolet parts.

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