Author: Soukoudragon, Daigensui Hello everyone, today we have another article from Soukoudragon, (revised by Daigensui) this time about (sort of confirmed) Japanese tier 10 tank. Enjoy! After the culmination of many tested core components, the STB-1 was completed in 1969. The STB-1 was the first of two development phases in the development of the Type 74. Despite its technical and rather unimposing name, the first phase was an ambitious and successful creation while the second phase was largely about taking a katana to the cost of the tank while improving endurance and reliability. The STB-1 is indeed an imposing tank and would be a very competitive tier 10 tank in World of Tanks. Historical Background In the early 1960s, in the mists of the cold war, European, American, and Soviet tanks were progressing from the M48, T-55, and Centurion 3 class of tanks to the M60, Leopard 1, T-62 class of tanks. The incapability of Japan’s Type 61 tank to match these newer tanks prompted a heated debate. They debated over either improving the Type 61 (Type 61 Kai) or designing an entirely new tank. Whichever the decision was going to be, the key feature would be a 105mm cannon. Japanese tank engineer Kondo pointed out that not only a 105mm cannon but also mobility, target acquisition, and rate of fire must all be good for the sake of combined arms operations. In 1965, the decision was made to design an entirely new tank which launched the STB program. Naming Convention In the code name STB, the ST represents tank. And the B represents the Type 74 development program. So in the case of the Type 61, its code was STA. The developers actually wrote it by separating it with a hyphen like ST-A and ST-B. “Tank A” and “Tank B” if you will. But when the tank entered the hands of the testers, they removed the hyphen for whatever reason, making just STA and STB. The number that comes after is the cordial number for the prototype vehicle. So the 1 in STB-1 indicates the first prototype vehicle. The STB-2 was virtually identical to the STB-1. Both were tested at the same time. After their success, the second phase began and consisted of the STB-3, STB-4, STB-5, and STB-6 prototypes. Development History Prior to the 1965 decision to design an entirely new tank, some technologies which would later be used in the STB-1 were already in development independently in Japan. These were a new and stronger engine, a hydro pneumatic suspension, and a coaxial gear steering device which would improve the transfer of engine power. By March 1965, an air cooled 700 horse power class engine has been developed. Research on the hydro pneumatic suspension began as soon as the Type 61 tank was completed in 1961. Actual testing of it using a Type 60 APC prototype called the SU began in 1962. For fire power, they opted for a license on the NATO standard Royal Ordnance 105mm cannon. The part that Japan imported for license production was only the barrel. They built their own breech, recoil system and mantlet around the cannon. The full length of the cannon, including all parts just mentioned, was 5,592mm long and the total weight was 2,800kg. The Japanese final version resembled the US M68 105mm version the most. From 1966 until 1967, firing tests were carried out. In the picture below, the end part is the breech and the segment between that and mantlet is the recoil system. A prototype turret was completed when the 105mm cannon was mounted on it in 1966. In 1967 and 1968, aiming and turret rotation tests were carried out. A load assisting device was also introduced into the turret. This device maneuvered the rounds close to the breech of the cannon to enable the loader to reload faster. The coaxial gear steering, hydro pneumatic suspension and the 700 horsepower class engine have started testing together on a test bed called the ST-T in March 1966. The ST-T alone weighed 21 tons but fully rigged, it weighed 35 tons. Length was 6.64m, width was 3.06m, and height was 1.95m. Top speed on roads was 51km/h. In August 1967, the 10ZF engine replaced the prototype engine. The 105mm cannon was later loaded onto the ST-T hull and conducted firing test. Finally, the prototype turret was mounted on top of the ST-T and again conducted firing test. The ST-T finished its testing by April 1969. Having run about 5,500 km, it has contributed tremendously to the STB program. During the ST-T period, a mock-up was completed finally giving the first true look of the completed tank. Building of the STB-1 started in April 1968 and finished in June 1969 with its twin, the STB-2 being finished in September of the same year. During the STB-1s testing period the engine it mounted, the 2200kg 750 horse power 10ZF-21WT had some reliability issues. It would later be replaced in the Type 74 with the 2220kg 720 horse power 10ZF-22WT engine. By May 1971 Engineer Kondo stated that the “STB-1/2 passed all qualifications including top speed, acceleration, and shown excellent mobility. That it had good results in accuracy, stabilization, secondary armaments, and protection. To further improve its endurance and reliability, the STB program is ready to move to the second phase.” With phase 2 of the program, several systems have either been simplified or cut in order to increase reliability and/or to cut cost. The tank was actually very expensive so cost cutting was important. One feature cut was the remote controlled 12.7 machine gun at the top of the turret and replaced with a typical manual MG. The skinny stick poking up from the middle of the turret was a remote controlled periscope for the remote controlled MG. Before the STB-1 was built, Kondo preferred a manual MG because he argued that aiming at fast moving targets like aircraft would be impractical. However the remote controlled MG was installed in the STB-1 anyway only to be removed in the second phase. Stats In this section, some of the stats are actually coming from Type 74 sources however, those stats would very much happen to have been the same or extremely similar for the STB-1 otherwise they would not be listed here. Data Crew: 4 Full length: 9.423m Hull length: 6.7m Width: 3.18 Height: 2.25m Ground Clearance (±hydro pneumatic suspension) 400mm±200mm Track width: 550mm Ground Pressure: 0.86kg/cm2 Weight: 38 tons Engine: 750 HP/2200rpm Mitsubishi 10ZF-21WT Top Speed: 53km/h Transmission: Mitsubishi MT-57T (6 forward 1 reverse) Horse Power per Ton: 18.95 Turret Traverse speed: 24°/sec (historically the same as Leopard 1 and M48) Armor Continue reading →

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