O-I Super Heavy Tank (Type 100)
In 1939, the Japanese army began the study of a program of experimental super-heavy tanks, named O-I. This program takes the concept of multi-turreted tanks very popular in the thirties. Type 100 OI, weighing about 100 tonnes, was equipped with a main turret armed with a 105 mm (104.9 mm real caliber) gun, derived from the Type 92 model, having an initial velocity of 900 m/s. This gun fired projectiles with separate loads (16 kg shell and 30 kg cartridge), capable to pierce 150 mm of armor at 1000 m. Two secondary turrets, in charge of the close defense, were placed in front of the main turret, both armed with a 37 mm Type 1 gun. The armament was completed by three 7.7 mm Type 97 machine guns (two at the front and one at the back of the turret). The ammo carry includes 60 rounds for the 105 mm gun, 100 rounds for the two 37 mm rounds and 7470 rounds for the machine guns. With a 200mm frontal armor, the Type 100 shielding would have brought about defeating the vast majority of enemy anti-tank guns. To move the 100 tons of the monster, the assembly of two gasoline engines of 12 cylinders each, developing both 550 hp at 1500 rpm, was chosen. However, they would have a hard time to provide to the tank notable performances and it could hope to reach only 25 km/h on the road or flat ground. According to one of the engineers of the program, two prototypes (including a Type 120) could be assembled before the end of the war, but these words remain to be taken in the conditional.