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Type 87 Chi-I

The first Japanese medium tank was called 2587 "Chi-i" (sometimes it was called the "medium tank number 1") In 1927, the Osaka Arsenal revealed to the world the first Japanese tank of its own design. The machine had a combat weight of 18 tons and was armed with a 57-mm cannon and two machine guns. Armament mounted in two separate turrets. It is obvious that the first experience of the independent creation of armored vehicles was not crowned with particular success. Tank "Chi-I" was, in general, not bad. But not without so-called. childhood diseases, which was excusable for the very first design.

In 1917, the Imperial Japanese Military Motor Vehicle Investigation Committee dispatched Captain Mizutani Yoshiho to the United Kingdom to purchase a Mark.IV Female tank for research in Japan. Thus, Japan’s first tank would arrive in Yokohama port on October 24, 1918. Japan had also purchased 22 French Renault FT-17 and 4 British Whippet tanks, which were imported to Japan in 1920.

On May 1, 1925, the so-called “Ugaki disarmament” was executed, and to replace the four Japanese divisions being abolished, a tank corps of one squadron was newly established in Chiba and Kurume. However, since Japan at the time had not yet begun domestic production of tanks, the tanks deployed in these units were the old French Renault FT light tanks purchased for research in 1919-20, and the British-made Mk.A Whippet medium tank.

Therefore, the Ministry of Army dispatched a tank purchasing team led by Lt. Gen. Ogata, director of the Science Research Institute, to countries in the US and Europe, aiming to import the latest tanks from Europe and the United States. However, the prospects of the purchasing group were altered, and negotiations with the US designer of the Christie tank, designer JW Christie, and Vickers Armstrong in the United Kingdom, were not concluded. Of the surplus stock from the Great War from France, Ogata was only offered second-hand Renault FT light tanks. As there is nothing else to buy, the purchasing team asked to buy a large number of Renault FT light tanks.

On the other hand, the Army Technology Headquarters Vehicle Group, which completed Japan's first 3T traction vehicle in August 1923, was confident in the domestic production of tanks. And as a result of making a request to the Army Minister, the first domestic tank development was approved, and the mass purchase of Renault FT light tanks was postponed. However, the Army Ministry demanded completion of the prototype by the end of March 1927, as it could not delay the modernization of the Army by taking time to develop tanks.

The only vehicles that the Technology Headquarters had built so far were the Mitaka tow truck tracked development vehicle and the Four- wheeled freight carrier with a speed of 24 km/h. In addition, the domestic automobile industry at that time was extremely small and fragile, and its technological ability was low, and there were also few factories that had machine tools for cutting large parts of automobiles in Japan. But the Mitaka towing vehicle built in 1924 (Taisho 13) exhibited a top speed of 14 km/h, which was superior to Renault FT's 8 km/h.

The design procedure was studied from the beginning of 1925, and on 26 February 1925, the technical headquarters instructed the concrete performance and specifications of the tank to be developed.

• total weight kept around 12/15 tons
• occupying a crew of 5
• total length of 6 meters, the dimension of which would not hinder the placement on railway transport
• width was to consider the inland railway transportation (width 2.2 m)
• armor capable of withstanding an oblique shot of a 37mm infantry gun, from 500-600 meters
• a central rotating turret housing a 57mm caliber primary cannon
• two machine guns placed in a front and rear separate turret
• engine output of 120 horsepower
• maximum speed of 25 kmh
• trench crossing ability of 2.5 meters
• climbing radius of 43° degrees

Under the strict schedule, members of the technical headquarters vehicle group were devoted to the development of the tank led by Daisuke Hara (later junior general). The design was started in June 1925, and design drawings had risen to more than 10,000 elements in about a year. Production of prototypes was started at the Osaka Artillery Factory from 26 May 1926.

At that time Osaka Artillery Factory was the largest weapon factory in Japan, but the existing machine tools lacked the ability to make tanks, and one part was made using Kobe Steel and other private factories in the Hanshin area. They made one and proceeded with the work while solving any problems.

The development of the first trial-made tank seems to have been a series of trials and errors, since the development of the tank was the first experience for Japanese engineers. Although the required specification was 12t of the vehicle body weight, it was 16t by design weight because the arming was strengthened, and the body weight of the prototype car increased to 18t because safety was seen in the strength of each part.

The prototype was completed in February of 1927, two months before the expiration date of the projec, and could be operated inside the plant. This was a short period of one year and nine months. In June 1927, the operation test of the trial-made No. 1 tank was conducted, but because the weight greatly exceeded the planned value, the maximum speed on the road remained at about 20 km/h. However, when compared with the old Renault FT light tank (maximum speed 8 km/h on the road) and the Mk.A Whippet medium tank (maximum speed 14 km/h on the road) owned by the tank group at the time, the revolutionary power plant was impressive. There were no problems with climbing, and it was judged to be suitable for practical use. Armor was made of mild steel due to lack of technology for tank bulletproof steel plates. At that time there was no development of welding technology in Japan or in power, and rivets were used all over the joints of armor .

Around this time, the Japanese Army purchased a state-of-the-art Mk. C medium tank from Vickers of the United Kingdom, and conducted various tests on the premise that it was equipped as a main tank, but the trial manufactured No. 1 tank had unexpected high performance. Because it was demonstrated, the Army withdrew its introduction policy of foreign-made tanks, and the maintenance policy of domestic-made tanks was decided.

However, it was decided to develop a lighter main tank (later type 89 medium tank), as it is too heavy to be adopted as the main tank. The trial made with the first tanks also had the advantage that it was difficult to throw away, so the policy was decided to improve them and make them a supporting heavy tank, and the technical requirements were added to the research headquarters's research policy.

This improved tank (test-made No. 2 tank) is the same as the first made-to-order tank that is an infantry support tank with a maximum speed of 22 km/h on the road, which uses a 57 mm gun as its main gun. It is noted that in consideration of ship transportation, it was emphasized that the weight of the main turret and secondary turret except for easy disassembly could be kept within 16 tone. The second trial tank was remodeled in April 1930. By reducing the weight of each part to 16t and increasing the engine output by adopting an aluminum piston and changing the valve timing, designers achieved improved mobility and easy maneuverability. The main gun was initially equipped with a 57 mm stub gun, similar to the first trial tank, but was later converted to a 70 mm gun.

The apparent change from the prototype 1st tank is that the cupola for the main turret's length is lowered, the exhaust pipe muffler moves from the rear of the car body onto the fender, and the improvement of the super levee ability of the guiding ring. The position is raised and the like. Due to this modification, the second trial tank largely achieved the originally planned goal. However, it is said that the Technology Headquarters intended to make a complete new design if mass production could be done in the future.

Test Armor No. 1 is armed with a 57 mm tank gun on the main turret mounted on the battle room in the center of the car body, and 7.7 mm machine guns on the secondary turret mounted on the front and rear of the battle room I equipped them one by one. The caliber and placement of this armament was similar to that of British tanks at the time. The design of the main gun, 57 mm, was launched in March 1926 and completed in October of the same year. It was then remodeled and mounted on the first manufactured tank in July 1927, and it was formalized in 1930 to become a "90-type 5.7 cm tank gun". This gun was also adopted as the main gun of the Type 89 medium tank (I). The performance of the gun was 350m / s, the initial velocity of the muzzle, and the maximum range was 5,700m. The prototype 2 was originally equipped with a 90-inch 5.7 cm chariot gun on the main turret, but was later converted to a 70 mm chariot gun.

Test armor No. 1 tank armor thickness of the main part was 17 mm, otherwise it is 8 to 10 mm, the bottom plate was 6 mm. This was the only armor thickness that could withstand a 37 mm shell, but it was impossible to strengthen the armor any more, as the weight had increased significantly above the planned value. In addition, since Japan had no manufacturing technology for tank bulletproof steel plates at that time, the trial-made No. 1 tank was not made of bulletproof steel plates but mild steel plates. In the case of the prototype No. 2 tank, the thickness of the main armor was reduced to 15 mm in order to reduce the weight, so that the weight could be reduced to the original planned value of 16 t, and the mobility was slightly improved.

The engine of the first prototype tank was designed for the domestic 155mm self-propelled gun in 1923, but it was diverted to this car because the plan of the self-propelled gun was stopped on account of the above It is reported that it was done. The engine was mounted at the center of the vehicle body, and was provided with an engine inspection space that also served as a communication passage for the front and rear sub turrets.

The steering system was a combination of a planetary gear type shift / steer and a clutch / brake. The suspension system of the trial-made No. 1 tank is a combination of leaf springs in a parallelogram, aiming for stability during shooting while traveling, but it is said that its weight was large and its buffer performance was poor. As for the wheel, one with a small diameter is also used on one side, with 32 guide wheels in front and an activation wheel in the rear. The trial production No. 2 tank has improved the mobility and maneuverability by increasing the engine output by adopting the aluminum piston and changing the valve timing.

Even the individuals who were against tank production were now all for it. The trials of the tank were very successful, but the tank was never adopted into military service. The problem with the Experimental I was that the Army's weight requirement was 12 tons, the weight of the tank in the design phase was 16 tons.

Taking into account the experience of testing and trial operation in the troops, four years later another tank of the same mass was created. "Type 91" was equipped with three turrets, in which there were 70-millimeter and 37-millimeter cannons, as well as machine guns. It is noteworthy that the machine-gun turret, being designed to defend the machine from the rear, was located behind the engine compartment. The other two turrets were located in the front and middle of the tank. The most powerful weapon was installed on a large middle turret.

The Japanese used this weapon scheme and layout on their next medium tank. The Type 95 appeared in 1935 and was even built in a small series. However, a number of design and operational features ultimately led to the abandonment of multi-turret systems. All further Japanese armored vehicles were either equipped with one turret, or costing chopping or armored machine gunner.