Author: Soukoudragon Development history Japan expected that a new generation of tanks capable of tank engagements would be needed later in the war. In 1942, three medium tank classes were initiated. A 47mm cannon class, a 57mm cannon class, and a 75mm cannon class. These three classes were called Kou, Otsu, Hei respectively (something like A, B, C). It was soon considered that the 47mm cannon class medium would be obsolete before completion thus it was upgraded to a 57mm cannon class tank. The other 57mm cannon class medium merged with the 75mm cannon class tank. Thus these two, the 57mm cannon class tank and the 75mm cannon class tank, were respectively the Chi-To and the Chi-Ri tanks. In the beginning plans were for a 20 ton tank with 50mm of armor with new features like an electrically driven turret. By February 1943, plans changed to 75mm armor, the 57mm cannon and top speed of 45kph. For a bigger tank, a new engine started development by Mitsubishi and AL in 1943. The result was a air-cooled diesel 412 horsepower at 1800 rpm. Multiple types of suspensions were examined such as the staggered road wheel layout from Germany (Chidori) and torsion bars. but the Japanese settled with what they were familiar with, the coil springs. The 57mm cannon prototype was completed in March 1944. It completed testing and was officially named the Chi-To in May 1944. 57mm Chi-To prototype below. In the very same month, the Chi-To received the requirement to mount a high velocity 75mm cannon. The cannon would come for the Chi-Ri tank program. The single tray loader would be removed and the cannon was named the “model 2″ and was used for the Chi-To. There were delays in getting the new cannon on which eventually happened in early February 1945. A new turret and hull was designed and planned to enter production beginning in August 1945 (the “production version”). Plans were written up to create 170 Chi-To tanks by the end on 1945 Armor Turret front: 75 Turret side: 50/35 Turret rear: 35 Hull front: 75 Hull side: 35/25 Hull rear: 35 Source: 日本の戦車 Japanese Tanks Hara 1978 グランドパワー Ground Power October 2012 Daigensui’s additional data on Chi-To: Penetration Data/Expectation of Tank Guns Used in Service 75 mm Gun Type 3 Shell Weight: 6.615 kg Muzzle Velocity: 668 m/s Kinetic Energy: 1476 kj Historical Pen: 90 mm (100 meters), 65 mm (1,000 meters) Expected Pen: 103 mm 75 mm Gun Type 5 Shell Weight: 6.615 kg Muzzle Velocity: 821 m/s Kinetic Energy: 2229 kj Historical Pen: 75 mm (1,000 meters) goal (met), 80 mm (1,000 meters) expected Expected Pen: 130 mm + (137 mm possible) Prototype Chi-To’s effective frontal armor is like this: Upper frontal plate: 90 mm Lower frontal plate: 80 mm Production Chi-To’s effective frontal armor is like this: Upper frontal plate: 106 mm Lower frontal plate: 80 mm Prototype on the left, production version on the right Production schematics of Chi-To: Chi-To prototype:

More...