Japan (1938)

Experimental Medium Tank – 1 built

Chi-Ha’s Competition

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.

Development

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.

Design

Hull

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 meaning “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.

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 this was the flat bow, leading to a negatively angled lower glacis.

Armament

The main armament consisted of the Type 97 57mm. Its primary ammunition was HE (High-Explosive) shells and HEAT (High-Explosive Anti-Tank) rounds. This was the same gun as found on the initial models of the Chi-Ha. The gun kept the Japanese tradition of excellent depression. In the Chi-Ni’s case, this was 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 because it was able to fire High Explosive shells at close range on advancing enemy infantry, or down into occupied trenches. Furthermore, like the Chi-Ha, the Chi-Ni’s turret ring was made as large as possible, to allow for any future turret upgrades.

Mobility

The tank shared a similar bell crank suspension to the Ha-Go – this being a near constant of Japanese tank designs of the epoch. The difference was that in the case of the Chi-Ni, at the end of each bogie were 2 small road wheels, making 8 per side.

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.

Crew

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 offset to the left of the tank. The turret was so small that he also had to act as loader and gunner to the 57mm gun. 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 who would operate the ball mounted 7.7 × 5.8mm Arisaka Type 97 machine gun. These two crew members would have been relatively well protected from enemy fire.

Losing to the Chi-Ha

At the time of its conception, the Chi-Ni was considered the superior tank as it was so much lighter and cheaper to build. However, whilst the Chi-Ni and Chi-Ha trials were in progress, the Marco Polo Bridge Incident occurred on July 7th 1937, marking the start of the Second Sino-Japanese War.

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 and its fate is unknown. It is likely that it was broken down and recycled with its parts put back into circulation.

Originally Published November 27th 2016

Illustration of the Type 97 Chi-Ni by Andrei ‘Octo10’ Kirushkin, funded by our Patreon Campaign.

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

Sources

Chi-Ni on www.weaponsofwwii.com

Japanese Tank Development

AJ Press, Japanese Armor Vol. 2, Andrzej Tomczyk

Osprey Publishing, New Vanguard #137: Japanese Tanks 1939-45.

Profile Publications Ltd. AFV/Weapons #49: Japanese Medium Tanks, Lt.Gen Tomio Hara.

Bunrin-Do Co. Ltd, The Koku-Fan, October 1968