In 1938, the Japanese Military began looking for a replacement for the ageing Type 95 Ha-Go light tank. High ranking members of the military had a preference for more lightly armored infantry support vehicles. As such, two medium tank projects were put forward, with specific guidelines set.
These were: a maximum weight 10 tonne, 20mm maximum armour thickness, 3 man crew, maximum speed 27 km/h (17 mph), trench crossing capability of 2200 mm upgraded to 2400mm with a ditching tail and armament consisting of a 57 mm gun and one machine gun.
Under the working name of Medium Tank Project Plan 2, The Type 97 Chi-Ni (試製中戦車 チニ Shisei-chū-sensha chini) was submitted by Osaka Army Arsenal. It was a low cost alternative to its competition, the Type 97 Chi-Ha, made by Mitsubishi Heavy Industries.
The Chi-Ni was envisioned as a smaller, lighter alternative to the Chi-Ha, and was easier and cheaper to produce. The prototype was completed early 1937, taking part in trials against the Chi-Ha soon after.
It featured a number of cost-cutting features. It was of mostly welded construction, Its drive wheels, idler wheels and tracks were the same as those used on the Type 95 Ha-Go. For a time it was tested with the Ha-Go’s suspension, but it was soon apparent that it did not support the longer chassis well enough.
A side shot of the Chi-Ni prototype. (Source: – live.warthunder.com)
The hull was designed with a streamlined silhouette to protect from shell damage, and was of a monocoque design. Also known as structural skin, monocoque is a French word for “single hull”’ and is a structural system where loads are supported through an object’s outer layers.
This method is also used on some early aircraft and in boat building. Because of this, the tank was mainly of a welded construction, an unusual design choice for Japanese tanks of the era, which were mostly riveted onto a skeletal framework. The rear of the hull also featured the somewhat archaic feature of a ditching or “tadpole tail” to help it cross trenches. This was a removable feature.
A rear view of the Chi-Ni, showing the removable ditching tail.
The Chi-Ni was a 3 man vehicle, compared to the 4 of the Chi-Ha. The commander of the vehicle was positioned in the turret, which was off-set to the left of the tank. The turret was so small, he also had to act as loader and gunner to the Type 97 57mm tank gun. It’s primary ammunition was HE (High-Explosive) shells and HEAT (High-Explosive Anti-Tank) rounds.
The gun kept the Japanese tradition of excellent depression. In the Chi-Ni’s case, this was a negative 15 degrees over the front and left side. Depression over the right and engine deck would have have been slightly limited by at least 5 degrees.
The depression suited the tank’s infantry support role like a glove, able to fire High Explosive shells at close range on advancing enemy infantry, or down into occupied trenches. Like the Chi-Ha, the Chi-Ni’s turret ring was made as large as possible, to allow for any future turret upgrades.
This image shows just how off-centre the turret is. (Source: – www.weaponsofwwii.com)
Directly below and slightly in front of the commander sat the driver. With no room in the turret for a coaxial machine gun, the third crew member sat on the driver’s right. He would operate the ball mounted 7.7 × 5.8mm Arisaka Type 97 machine gun. These two crew members would’ve been relatively well protected.
Though the armor was only 20mm thick, it was extremely well angled. The driver’s position was encased in a semi-hexagonal box, in front of him was the flat bow, leading to a negatively angled lower-glacis.
The tank shared the same bell crank suspension as the Ha-Go, but it was slightly different. At the end of each bogie were 2 small road wheels, making 8 per side. The bell crank suspension is somewhat of a constant in Japanese tank design of World War II.
The forward mounted drive wheels were powered by a Mitsubishi 135 hp diesel engine that would propel the vehicle to a blistering 27 km/h (17 mph). It was also tested with the 120 hp Mitsubishi A6120VDe air-cooled diesel engine from a Type 95 Ha-Go.
A top down view of the Chi-Ni showing the engine deck.
Losing to the Chi-Ha
At the time of its conception, the Chi-Ni was considered the better tank, as it was so much lighter and cheaper to build. However, while the Chi-Ni and Chi-Ha trials were in progress, the Marco Polo Bridge Incident of July 7th 1937, the start of the Second Sino-Japanese War, occurred.
Peacetime budgetary limitations evaporated with the outbreak of these hostilities with China. With this, the somewhat more powerful and expensive Type 97 Chi-Ha was accepted for development and service as the Imperial Japanese Army’s new medium tank. It would go on to become one of Japan’s most highly produced tanks.
Only one Chi-Ni prototype was ever built, it’s fate is unknown. It is likely that it was broken down and recycled with its parts put back into circulation. It’s safe to say it was one of the strangest looking AFVs of the period.
Type 97 Chi-NI
|Dimensions||17 ft 3 in x 7 ft 4 in x 7 ft 8 in (5.26 m x 2.33 m x 2.35 m)|
|Crew||3 (driver, commander, machine-gunner)|
|Propulsion||135hp Mitsubishi diesel engine|
|Speed||17 mph (27 km/h)|
|Armament||Type 97 57mm Tank Gun
7.7×58mm Arisaka Type 97 machine gun
|Armor||8-25 mm (0.3 – 0.9 in)|
|Total production||1 Prototype|