Toyopet Corona Model ST10

On July 1, 1957, the first-generation Toyopet Corona Model ST10 was launched. The model used the S engine introduced 10 years earlier.

When the S engine was developed in 1947 and installed in the Model SA passenger car and the Model SB truck, its maximum output was 27 hp at 4,000 rpm (Table 1-31). The S engine was subsequently improved to feature an output of 33 hp at 4,500 rpm when it was installed in the Corona Model ST10 in 1957. Incidentally, the engine's torque was also improved from 5.9 kilogram-m at 2,400 rpm to 6.5 kilogram-m at 2,800rpm.

Table 1-31. Improvement of the S Engine (1947-1957)

Maximum Output
Vehicles Using the Engine
1947
27 hp/4,000 rpm
Model SA passenger car, Model SB truck
1951
28 hp/4,000 rpm
Model SF passenger car, Model SG truck
1954
30 hp/4,000 rpm
Model SKB truck
1957
33 hp/4,500 rpm
Model ST10 Corona

The Toyopet Corona Model ST10, as described previously, was designed and manufactured by Kanto Auto Works, and became the first Toyota car to use a monocoque body. The "S" in the vehicle model signified the S engine, the "T" signified the T body, and "10" signified a standard sedan of the first model. In other words, the model was the first-generation Corona standard sedan equipped with the S engine. This vehicle model specification method had been adopted beginning with the first-generation Masterline Pickup (Model RR16) and the Masterline Light Van (Model RR17) launched in November 1955.

The Model ST10 was a compact four-seater passenger car designed by utilizing immediately available existing parts. These included the S engine; various parts used in the Model RS Crown, such as the suspension, powertrain, brakes, and steering; as well as body parts of the Model RR Master. Table 1-32 shows the specifications of the Model ST10.

Table 1-32. Specifications of the Model ST10 First-Generation Toyopet Corona (1957)

Item
Description
Engine
Model S (995 cc, 33 hp)
Length
3,912 mm
Width
1,470 mm
Height
1,518 mm
Vehicle weight
960 kg
Maximum speed
90 km/h
Source:
Toyota Engineering Society's, Toyota Technology, P.2, December 25, 1957

At that time, Toyota Motor Co., Ltd. was developing a new 1,000-cc engine and a new compact passenger car. The new engine was completed as the P engine1 and was installed in the Corona Model PT10 in October 1959, two years after the announcement of the Model ST10. Then in March 1960, the Corona was completely redesigned and the second-generation Model PT20 debuted.

Shotaro Kamiya, then President of Toyota Motor Sales Co., Ltd., gave the following explanation for why Toyota developed the Model ST10 instead of waiting to complete its new compact passenger car:

The development of the Corona ST10 had hit a roadblock because some of the people on the design team did not necessarily agree with the way it was being created. In the end, being the person responsible for sales, I insisted that we put it out on the market and ask the public to judge it, and so we decided to go ahead with the production of the Corona.2

Because Toyota Motor Co., Ltd. (which was in charge of manufacturing) had already been working to develop a new compact passenger car, it can be safely assumed they were reluctant to manufacture a car based on a amalgam of available parts from other vehicles. President Kamiya overruled this objection and the decision was made to subcontract designing and manufacturing to Kanto Auto Works.

Meanwhile, 48 Toyopet dealers, responsible for selling Toyota vehicles, were set up by June 1, 1957, completing Toyota's nationwide sales network. Three kinds of commercial vehicles (the small truck Model SKB, which was named the Toyoace, the Masterline pickup Model RR16, and the Light Van Model RR17) were sold through this network, but there was no passenger car sold that could be seen as a pillar. It was probably for this reason that President Kamiya strongly insisted on developing the Corona Model ST10, out of concern for the Toyopet dealers.

In addition to this situation, production of the Master Model RR at Kanto Auto Works had been terminated in November 1956, after a cumulative production volume of 7,403 units. The Master Model RR was a passenger car for use as a taxi that had been designed by Kanto Auto Works and launched at the same time as the Crown in 1955. Manufacturing of the Corona Model ST10, a smaller, modified version of the Master Model RR, gave Kanto Auto Works an opportunity to make up for the termination of the Master Model RR production.

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