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Special Type 3 Internal Fire Boat Ka-Chi

The Japanese Navy produced in 1942 the special type 2 fire boat (Ka-Mi vehicle), which was the first full-scale amphibious tank. But the Ka-Mi vehicle was based on the Army 95-type light tank (Ha). Being a developed vehicle, the fighting ability never left the light tank range, and was too weak to compete against the powerful US-UK tanks. To this end, the Navy planned to develop more powerful amphibious tanks based on the Type-1 medium tank, which was the latest tank of the Army at that time.

This new amphibious tank has been developed with the secret name of "Ka-Chi vehicle", but Ka-Chi vehicle adopts the set of 47mm tank gun with high initial speed as the main gun like Chi-he vehicle, and the front of the body is also Chihe It had the same 50mm size, and had the highest level of firepower and defense among the Japanese tanks at that time. However, unlike the time of the Ka-Mi vehicle, there was no movement to adopt the Ka-Chi vehicle in the army.

The Ka-Chi vehicle was too specialized - the navy planned submarine raid operations, while the Army's expected amphibious tank is a light reconnaissance tank equivalent to a light tank. It was not a medium tank for a full-fledged anti-tank battle that the Navy aimed at. As apparent from the appearance, it was assumed that the Ka-Chi vehicle would be transported by submarines.

However, the internal mechanism of the Ka-Chi vehicle is generally refined compared to the Ka-Mi vehicle, and the screw at the rear of the vehicle body, which was a drop-off type for the Ka-Mi vehicle, is a flip-up type for the Ka-Chi vehicle, ensuring clearance from the ground. The floats mounted on the front and back of the vehicle were able to separate at the same time with one handle. In addition, the engine of the Ka-Chi vehicle is housed in a cylindrical pressure-resistant hull of 3 m in diameter, and the time and effort of mounting the engine in the vehicle before landing is saved as in the case of the Ka-Mi vehicle.

For this reason, the time taken to prepare for launch from a submarine that has surfaced was reduced from 30 minutes to 10 minutes. In addition, the safety depth of the pressure resistant hull of the Ka-Chi vehicle is set to 100m, and it was possible to dive to the safety depth of the submarine which is the mother ship. However, there is also a reflection on the design side that such a structure was low in productivity and somewhat overly heavy.

The outer left and right sleeves of the pressure resistant hull section were watertight sections that vehiclery buoyancy during floating navigation (opened during diving transport and free to move in and out of seawater), but the cylindrical pressure resistant section is exposed at the rear of the vehicle body. It had a unique shape as a tank.

Since the engine, transmission system, driver's seat, etc. are inside the pressure hull, it was necessary to open the circular hatch fixed with bolts at the top of the pressure hull in order for the crew to get in after the submarine is lifted. The hatch was accessed from the rear of the turret. For this reason, the turret rear hatch of the Ka-Chi vehicle was designed to be able to open widely.

The installed 47mm tank gun that is the main gun of a Ka-Chi vehicle had a height of 2,450 mm, a muzzle initial velocity of 810 to 832 m / sec, a firing speed of 10 shots / min, armor penetration penetration force when using a complete armored shell bullet was 65 mm at 500 m and 50 mm at 1,000 m. The 47mm shell for the main gun was equipped with 121 shots like the Chi-he vehicle. Thirty shots were six-in-a-row containers with 30 left and right behind the gunner, 30 right on the rear of the turret, 12 on the right of the vehicle seat, 7 on the left and aft of the turret, and 42 in the battle compartment placed under the floor.

As with the Ji-he vehicle, it was equipped with a 97-type in-vehicle heavy machine gun (7.7 mm caliber) on the front left side of the battle compartment and the left rear face of the turret. There were 5,000 7.7 mm bullets carried, with the hull machine gun mounted in front of the gun seat and the turret machine gun mounted on the right rear of the turret. The turret's turn and the main gun's elevation were manually operated using the steering wheel, and the turret was equipped with three drivers, a gunner and a loader.

The vehicle body and turret of the Ka-Chi vehicle were welded with rolled ballistic-proof steel plate in the same manner as the base vehicle Chi-he, and the armor thickness of each part is basically the same as the one. As for the armor thickness of the vehicle, the vehicle body is 50 mm in front, 25 mm in side, 20 mm in back, 10 mm on top / bottom, the front is 50 mm in front, 25 mm on side / rear, 12 mm on top. So it boasted the highest level of defense.

The Ka-Chi vehicle's armor plate was provided by the navy, and it seems that the ship's NVNC steel plate or CNC steel plate series was probably used. According to Navy officials, Army officials were surprised to show good bulletproof performance regardless of the shooting angle in the bulletproof test. The Navy had long experience in manufacturing NVN steel plates as homogeneous steel plates used for underwater protection etc. and steel plates of 75 mm or less, and also researches CNC steel plates (a low cost steel plate that suppresses the amount of nickel addition) the navy had been continuing research. On the other hand, the floats mounted on the front and back of the vehicle of the Ka-Chi vehicle are made of 3 mm thick mild steel plate and the inside was divided into a number of compartments so that they will not lose their buoyancy immediately in the event of a bullet hit.

The Ka-Chi vehicle engine, like was an air-cooled diesel engine. The number of cylinders of a Ka-Chi vehicle was a maximum of 12. With a cylinder diameter of 120 mm, a piston stroke of 160 mm, and a pre-combustion type output of 240 hp, it boasted the maximum output as a diesel engine for Japanese tanks at that time.

However, the Ka-Chi vehicle had a basic body extended compared to the Chi-he vehicle, and it had a weight of 10 tons or more compared to the Chi-he vehicle. The floats equipped on the front and back of the vehicle body and various equipment for waterborne navigation made it heavy, and this engine was underpowered, giving the maximum speed on the road remained at 32 km / h.

Basically, the base of the Ka-Chi vehicle is extended by using the one of the Chi-he vehicle, and in the case of the Chihe vehicle, the central four wheels are connected by two bogies and suspended by the sideways coil spring. The vehicle was equipped with two sets of this suspension on one side. Therefore, the number of rolling wheels was eight on one side, and the number of upper supporting wheels was also increased from three to four on one side of the vehicle.

The Ka-Chi vehicle, like the Ka-Mi vehicle, was equipped with a distributor that switched the powertrain to the actuating wheel in front of the vehicle body or a screw provided on the vehicle rear panel. When sailing on the water, power to the track was cut off, and two screws were rotated by two shafts passing from the distributor to both sides of the engine.

The distributor also played the role of a bilge pump that drains water into the vehicle. The intake and exhaust of the engine are performed from the upper surface of the engine room, and when traveling on the water, the ventilating cylinder is raised to secure the intake. The direction change on the water was done by operating the two rudders mounted on the float mounted at the rear of the vehicle body using a cable.

The water navigation speed of the Ka-Chi vehicle was 10.5km / h, which was slightly higher than that of the Ka-Mi vehicle despite the increase in size of the vehicle body. After landing, the floats on the front and back of the vehicle were cut off, and the screw was separated along with the float.

The tactical vehicle, which was formulated as a "special power boat" in 1943, was not put into battle, but 19 units were produced by Tokyo Heavy Industries, Ltd. of Mitsubishi Heavy Industries from 1943 to 1945. By the end of the war it is said that the number had been deployed along with about 20 vehicles in the 16th Special Land Squadron Unit 2 in the Yokosuka Guards District.

As for the reason why the vehicle has not been launched, production had not progressed as the Navy prioritized the production of ships and aircraft, and since mid-1944 the battlefield has worsened, and a surprise attack from a submarine that required this vehicle landing operations had become unrealistic. The completed vehicles were preserved in preparation for the mainland battle.

Type 3 Ka-Chi
total length 10.30M (with float)
total width 3.00 m
Height 3.82M
gross weight 26.45T (no float), 28.75t (with float)
occupants seven
Engine Control type one hundred formula Four-stroke V-type 12-cylinder air-cooled diesel
Maximum output 240hp / 2,000rpm
Maximum speed 32km / h (floating 10.5km / h)
Range 320km (floating 140km)
  • Type 48 caliber 47mm tank gun 1 (121 shots)
  • 97-type vehicle 7.7 mm heavy machine gun 2 (5,000 shots)
  • armor thickness 10 to 50 mm

    Type 3 Ka-Chi Type 3 Ka-Chi Type 3 Ka-Chi Type 3 Ka-Chi Type 3 Ka-Chi
    Type 3 Ka-Chi

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    Page last modified: 14-06-2019 18:16:39 ZULU