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Part One, the Development Story of the Type 90 Helmet

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    Part One, the Development Story of the Type 90 Helmet

    The Type 90 is a fairly big theme with lots to write about, so I will cut it up in several threads in order to keep them readable. This is part one covering the development story.

    The Development of the Type 90 helmet

    The development project for the Type 90 helmet was launched within the Army’s Technical Headquarters on January 10, 1927.
    The cherry blossom helmet, which had been adopted as a provisional standard in June 1922 had revealed some drawbacks that they sought to address. It had, according to the official Type 90 development report, a “complex shape not easy to produce, was heavy and inconvenient for use, particularly when shooting in a prone position, as the rear of the helmet got caught against the backpack, hindering movement during combat”. It is interesting that the developers of the Type 90 regarded the cherry blossom helmet as heavy, as in fact, they are lighter than the Type 90. Perhaps they meant it was heavy for the level of protection it gave. Or it could also be possible that the third design of the cherry blossom helmet, which would have been the starting point of the Type 90 development and which the author has not examined in person was indeed heavier.

    Development Objectives
    They set up the following four objectives as goals in the study.

    1. A shape that is easy to manufacture.
    2. By keeping protective qualities to a certain limit, minimize weight
    3. Attributes of economy that allow self-sufficiency of production
    4. Use of a metal that satisfies the above three conditions

    Benchmarking against foreign examples
    In order to set up a benchmark study, the Army started collecting helmets of various western armies from April 1927. Prototyping studies were launched at the arsenal, and they also got hold of an example of the helmet produced by the Army on the occasion of the “Siberian Incident” of 1918 for comparison.
    The foreign helmets used for bench-marking were German, Swedish, Swiss, Danish, Dutch, British, French and American. ( Though, the official report claims that comparison studies with foreign helmets started in 1927, the Army medical school had actually been collecting foreign helmets at least for the last 3 years, as they wrote to the Army arsenal in April 1924 for a sample of the latest Japanese version to add to their comparative studies.)

    Development progress (1927-1929)
    In May 1927, a joint study was launched with the arsenal to develop a suitable alloy, and in June a rifle modified to shoot shrapnel shell pellets at variable velocities was completed along with a designated firing range for testing the helmets.
    The foreign helmets that started to arrive and the prototypes from the arsenal numbered 160 in total, and tests on these helmets were conducted between November 1927 and January 1928 at the range, where the anti-penetration qualities, alloy makeup, weights, thickness, shape, etc of the samples were studied and compared in detail.
    And in February 1928, anti-shrapnel testing was done at the Tomitsu Range located at the tip of a cape that juts out into Tokyo Bay. There the helmets were exposed to fire by real shrapnel rounds from a Type38 75mm Field Gun, Type 10 grenades and high explosive rounds fired from the Type 38 Field Gun.
    Based on these test results, a finalized design was devised, and in October of 1928 an order was placed with the arsenal for a large and small size. These preproduction samples were delivered in March of 1929 and tested to verify that their weight, anti-penetration qualities, shape and material all met the initial objectives laid out.

    Field evaluation and improvements (1929-1930)
    From July 1929, field evaluations were carried out to check wear comfort and portability. For this, the Army Infantry, Cavalry, Field Artillery and Heavy Artillery, as well as Field Engineer Schools were requested to participate and provide improvement suggestions.
    The prototype helmets supplied to the schools were different from the finalized Type 90s in two major respects. They had no ventilation holes on top and had a different chinstrap system.
    Ventilation holes were added to the Type 90 in response to requests from the Cavalry and Field Artillery Schools who wanted “grommet vents like in their visor caps”.

    The chinstrap system was different from the final system in that it was shorter, had a metal buckle closure and was a one-piece construction rather than the two-piece system finally employed in the Type 90.
    At 65 centimeters in length, the chin strap was found to be too short for wearing the helmet in conjunction with a gas mask, and the Cavalry School suggested extending the length to 70 centimeters.
    The buckle closure employed was deemed cumbersome by the infantry and engineers, who suggested a simpler open-faced buckle design like that of the waist belt. The Cavalry as well as the Heavy artillery Schools further suggested using rubber straps as per gas masks, particularly for the back strap, and it was the Heavy Artillery School that suggested, making the front and rear straps into two separate straps that could be tied under the chin.

    The idea of rubber straps was not incorporated, because of the poor durability that rubber straps would have had, but the straps were lengthened, made into two separate straps and a buckle system was discarded altogether in favor of a simple tie string arrangement under the chin.

    The infantry school still complained that, though better than the cherry blossom helmet, the rear of the helmet still came into contact with the backpack, but developers ruled against trimming the rear any further and compromising protection.

    Regarding the carry method when not worn, the infantry and engineers suggested attaching to the back pack flap, while the Heavy Artillery School came up with the idea of hanging it in front, on the left chest, for which they requested a slit (5mm by 25mm) to be added to the bottom of the rear skirt of the helmet. They also preferred to have the helmet’s front plane to drop straight down in a perpendicular way rather than slop forward, but both of these shell changes were rejected, due to poor deflection, strength and manufacturing considerations.

    Official introduction
    After incorporating these improvement suggestions, the helmet was deemed ready for adoption by the Army. On March 31st, 1930, The Army Technical Headquarters released the documentation, titled “Type approval of Close Combat Equipment, Type 90 steel helmet” in the name of its chief, Toyohiko Yoshida, requesting type approval by the Minister of the Army, Kazunari Ugaki. This document got its final stamp of approval on October 28, 1930, and the cherry blossom design introduced in 1922 was superseded and discontinued

    Official description at the time of introduction

    Purpose: To be worn during combat when required.
    Structure and function
    The Type 90 helmet consisting of the shell, leather liner and chin strap. The shell is formed from a single sheet of special steel plating and has the liner and strap installed inside. It is available in the two sizes of large and small, where large corresponds to the visor cap sizes 1 to 5, and small corresponding to 6 to 10.
    Fit to the individual’s head is achieved by adjusting the volume of the liner padding. Weight is 1 kilogram for the large helmet and 0.95 kilogram for the small size.
    Before wearing the helmet, the liner padding is to be adjusted to achieve best fit to the individual, after which it is to be secured by tying the chin straps.

    The Type 90 in comparison with the Type 1922, Cherry Blossom
    Attached Files
    Last edited by Nick Komiya; 11-15-2011, 12:23 PM.

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