Section 3. Research and Development of Basic Technology
Item 2. Researching Casting Technology
Not long after Toyoda Automatic Loom Works began operations in 1927, the company installed a 1.5-ton electric arc furnace, as instructed by Kiichiro. The furnace was used to melt cast iron. Cast iron produced by an electric furnace was harder and had greater tensile strength than that produced by a cupola furnace; in other words, the cast metal exhibited superior mechanical properties. Later, in 1930, alloy cast iron produced by the electric furnace was used in parts for the spinning machines.1
According to Umeji Harada, who had been a foundry worker at Toyoda Automatic Loom Works since its earliest days, the company was the first in Japan to produce cast iron using an electric furnace.2 Later, in 1933 when the company placed an order with Daido Electric Steel Manufacturing Co., Ltd. (now Daido Steel Co., Ltd.) for a 800 kVA 3-ton electric arc furnace, it is said that Daido responded by saying that they don't manufacture electric furnaces to melt cast iron. At the time, producing cast iron using an electric furnace was unknown territory even for electric furnace manufacturers.
In conjunction with the installation of the Daido electric furnace at Toyoda Automatic Loom Works, Kiichiro instructed the R&D personnel to conduct further research into electric furnace-produced cast iron. The purpose was to create alloy cast iron for cylinder blocks. The R&D personnel analyzed the composition of the cylinder blocks from a Chevrolet engine, and based on the results of their analysis created prototype molds using the electric furnace. They then analyzed the composition of the prototype molds, repeating the whole process as necessary. In order to do this, someone capable of analyzing the alloy cast iron composition was deployed to the foundry. These efforts resulted in the R&D personnel being able to replicate cylinder blocks for the A Engine of the same special composition (nickel-chromium cast iron) as the Chevrolet cylinder blocks.
Subsequently, in May 1934, the research laboratory began making prototype cylinder block molds. Earlier in March that year, Director Risaburo Oshima had returned to Japan from the United States and brought with him some oil cores no larger than one's little finger, allowing the R&D team to manufacture oil cores for use in casting the Type A Engine cylinder blocks. But the core-making had its own difficulties.
The R&D team had gained some knowledge about oil cores from U.S. casting-related journals such as Foundry and Foundry Trade Journal, but it was the first time that they had seen the real thing. The team procured tung oil, which is applied to paper lanterns and umbrellas to waterproof them, from a paper umbrella maker in Gifu, to use as the drying oil to be mixed in with the sand. The oil was mixed in with sand taken from a beach on the Chita Peninsula in Aichi Prefecture. The oil-sand mix was then put into a wooden mold, and fired in a ceramics kiln. The ratio of oil to sand, firing temperature and time were all individually adjusted until the team gained a good understanding of how to make the oil cores. Furthermore, because the single oil core for the hollow portion of the three cylinders and crank room was so large and heavy, and because it was so difficult to make, it was separated lengthwise into two in the direction of the cylinder arrangement.3
A mold for the cylinder block was finally completed in August 1934. However, when machine boring the inside of the cylinders, small pits4 were forming, making the cylinders unfit for use. After turning out ten cast cylinder blocks, only one or two were making it through the machining process. A similar problem occurred at around the time the Model G1 truck was launched in November 1935.
The team discovered that by further machining away the inside of the cylinders the pits would disappear. After asking the research laboratory of the Steelmaking Department to perform some materials tests, the team determined that by significantly increasing the amount of cutting stock, they could almost completely eliminate the number of defect molds. It was through this kind of repeated trial and error that the Automotive Department's research laboratory developed the basic technology necessary for manufacturing automobiles.
The company initially outsourced production of malleable parts for the chassis and drive system, but later changed to in-house production. The composition of malleable cast iron differs from regular cast iron, and because there was no quick way to analyze the composition, adjusting it was very difficult. Specialized knowledge was necessary to determine the composition of melted samples, so the company brought in an experienced foundry worker from another company, allowing it to make the changeover to internal production.
In 1937, Kiichiro instructed the R&D team to investigate Ford's cast steel crankshaft. The team conducted tests at a steel foundry, pouring melted steel from a high-frequency induction furnace into molds. But creating steel crankshafts was an extremely difficult task, due to the fact that cast steel is highly viscous when melted (so it is difficult to make it run throughout the mold) and because it also contracts considerably when it solidifies, which gives rise to pitting.
After the Koromo Plant was completed, while forged crankshafts made by Toyoda Automatic Loom Works' Kariya Plant were used, research continued into steel crankshafts made at the No. 2 Special Foundry for cast steel. However, manually filling in the pits created during machining of the steel crankshafts was very laborious (one particular crankshaft had 60 pits that required filling). In the end, the R&D team failed to develop a satisfactory cast steel crankshaft, so had to use the forged crankshafts made at the Kariya Plant's steel foundry instead.
Developing the technology to create a cast crankshaft had to wait until after World War II. In January 1953, the Automotive Department installed ductile cast iron (DCI) technology, and with the launch of the (Model) P Engine, which employed a DCI crankshaft, in October 1959, the company finally realized its long-awaited goal of commercializing a cast crankshaft.