Instead of uploading everything in chronological order, I'll release random sections, to try to cover a wider range of interests. I'm too lazy to pull out my helmet covers to illustrate this, so add your photos as you like.
Development of helmet covers for the type 90 helmet (1933-1938)
The wearing of helmets used to be an exception rather than the norm, but as the helmet became a part of the uniform soon after the start of the Manchurian Incident, it became more of a constant presence on the soldier’s head, and with it came the headaches and other discomforts. A problem that required addressing was the heat buildup within the helmet being baked under the sun.
Some form of heat insulation had to be provided and this led to the Army’s adoption of a cotton padded helmet cover on June 1st, 1938 through Army memo no. 31 (陸達第３１号). Though that was the timing it was officially adopted and entered regular supply, units in China had been wearing them as prototype items since the summer of 1933 when the first batch of 3,100 sets arrived at the headquarters of the Army stationed in China.
The troops in China tried them out that summer of 1933 from July 5th until September 15th and the official evaluation report was sent to the Minister of the Army, Sadao Araki in the name of the commander of the troops in China, Lt. General Kotaro Nakamura.
This report attests to the effectiveness of the cover in preventing heat buildup inside the helmet, saying that even after a 3 hour march under a sweltering sun the surface of the helmet under the cover showed only moderate heat and did not cause discomfort to the wearer. It also mentions three other side benefits. Firstly, that it contributes to concealment from the enemy by not reflecting the sun or light at night. Secondly that it prevented the steel helmet from damaging their guns by working as a cushion. Thirdly, its noise muffling qualities ensured stealth in night time operations, and also prevented wind noise made by the vent holes of the helmet in strong wind, which interfered with communication.
However, Nakamura also pointed out some improvements that required to be made to the prototype covers. He mentions that the covers were too heavy and caused excessive fatigue in extended wear, and that the base cloth needed to be waterproof to prevent it from sucking up water and becoming even heavier during rain. Lastly, he says the covers are too small for the corresponding helmet size and required to be more generous in fit and that the draw string should be made to be tied at the middle of the visor.
Between the summers of 1934 and 1935, helmet covers became part of a large scale tropical uniform development program, and like the last big tropical uniform development tests of 1921, it took place in Taiwan. In July 1934 the 2nd Taiwan Infantry Regiment received 160 samples each of three different helmet covers for testing.
The difference between the three was the heat insulation material used. Type A (甲) used cotton and weighed 100 grams, Type B (乙) used plant sponge from the Japanese gourd and weighed 155 grams and Type C (丙) used felt and weighed in heaviest at 175 grams. When the temperature inside the helmet was compared after a march in the sun, the felt model proved between one and two degrees centigrade cooler than the cotton version with the plant sponge version scoring in the middle. Despite the better cooling effect of the felt, the light weight and pliable, easy to handle properties of cotton made it the choice of the troops in the jungle. The other tropical items tested at the same time went through another round of tests in 1937 and 1938, but the helmet cover did not join that round as the matter was already settled.
It is not clear on what basis the covers were supplied after the summer of 1935 when the test in Taiwan ended and before they got standardized in 1938, but even before the second year of testing in Taiwan was over, a large shipment going out this time to the Kwantung Army and the 4th Infantry division, in June of 1935, included 5,000 covers along with 5,500 helmets, rounding out a cycle of testing that started out in China in 1933 and travelled to Taiwan in 1934 and now to the troops in the northern part of the continent.
As a sideline, apart from the development of the cover, the Army’s Scientific Research Institute had been conducting studies on the shell itself to find means of achieving better heat insulation for the helmet, which led to the granting of a patent on July 2, 1938 titled “Heat proofing of steel helmets (patent no.125576)”. The three researchers who applied for the patent found out that the rougher the inner surface of the helmet, the more intense the buildup of heat became inside, due to the larger surface area the roughness brought. For them the key was to obtain a smoother surface within the top part of the inner dome, and the patented idea consisted of plating the inner top surface of the helmet, for instance with chrome and to coat the lower part with saw dust or silk fiber mixed in shellac or other adhesive solutions. Their experiments showed that this method lowered the internal temperature by as much as 10 degrees centigrade more than in an untreated helmet. As the difference achieved in the helmet cover testing in Taiwan was a mere 1-2 degrees, 10 degrees is indeed a massive improvement factor, but one can easily imagine, that such an exotic method did not lend itself to mass production in terms of production time and cost.
Development of helmet covers for the type 90 helmet (1933-1938)
The wearing of helmets used to be an exception rather than the norm, but as the helmet became a part of the uniform soon after the start of the Manchurian Incident, it became more of a constant presence on the soldier’s head, and with it came the headaches and other discomforts. A problem that required addressing was the heat buildup within the helmet being baked under the sun.
Some form of heat insulation had to be provided and this led to the Army’s adoption of a cotton padded helmet cover on June 1st, 1938 through Army memo no. 31 (陸達第３１号). Though that was the timing it was officially adopted and entered regular supply, units in China had been wearing them as prototype items since the summer of 1933 when the first batch of 3,100 sets arrived at the headquarters of the Army stationed in China.
The troops in China tried them out that summer of 1933 from July 5th until September 15th and the official evaluation report was sent to the Minister of the Army, Sadao Araki in the name of the commander of the troops in China, Lt. General Kotaro Nakamura.
This report attests to the effectiveness of the cover in preventing heat buildup inside the helmet, saying that even after a 3 hour march under a sweltering sun the surface of the helmet under the cover showed only moderate heat and did not cause discomfort to the wearer. It also mentions three other side benefits. Firstly, that it contributes to concealment from the enemy by not reflecting the sun or light at night. Secondly that it prevented the steel helmet from damaging their guns by working as a cushion. Thirdly, its noise muffling qualities ensured stealth in night time operations, and also prevented wind noise made by the vent holes of the helmet in strong wind, which interfered with communication.
However, Nakamura also pointed out some improvements that required to be made to the prototype covers. He mentions that the covers were too heavy and caused excessive fatigue in extended wear, and that the base cloth needed to be waterproof to prevent it from sucking up water and becoming even heavier during rain. Lastly, he says the covers are too small for the corresponding helmet size and required to be more generous in fit and that the draw string should be made to be tied at the middle of the visor.
Between the summers of 1934 and 1935, helmet covers became part of a large scale tropical uniform development program, and like the last big tropical uniform development tests of 1921, it took place in Taiwan. In July 1934 the 2nd Taiwan Infantry Regiment received 160 samples each of three different helmet covers for testing.
The difference between the three was the heat insulation material used. Type A (甲) used cotton and weighed 100 grams, Type B (乙) used plant sponge from the Japanese gourd and weighed 155 grams and Type C (丙) used felt and weighed in heaviest at 175 grams. When the temperature inside the helmet was compared after a march in the sun, the felt model proved between one and two degrees centigrade cooler than the cotton version with the plant sponge version scoring in the middle. Despite the better cooling effect of the felt, the light weight and pliable, easy to handle properties of cotton made it the choice of the troops in the jungle. The other tropical items tested at the same time went through another round of tests in 1937 and 1938, but the helmet cover did not join that round as the matter was already settled.
It is not clear on what basis the covers were supplied after the summer of 1935 when the test in Taiwan ended and before they got standardized in 1938, but even before the second year of testing in Taiwan was over, a large shipment going out this time to the Kwantung Army and the 4th Infantry division, in June of 1935, included 5,000 covers along with 5,500 helmets, rounding out a cycle of testing that started out in China in 1933 and travelled to Taiwan in 1934 and now to the troops in the northern part of the continent.
As a sideline, apart from the development of the cover, the Army’s Scientific Research Institute had been conducting studies on the shell itself to find means of achieving better heat insulation for the helmet, which led to the granting of a patent on July 2, 1938 titled “Heat proofing of steel helmets (patent no.125576)”. The three researchers who applied for the patent found out that the rougher the inner surface of the helmet, the more intense the buildup of heat became inside, due to the larger surface area the roughness brought. For them the key was to obtain a smoother surface within the top part of the inner dome, and the patented idea consisted of plating the inner top surface of the helmet, for instance with chrome and to coat the lower part with saw dust or silk fiber mixed in shellac or other adhesive solutions. Their experiments showed that this method lowered the internal temperature by as much as 10 degrees centigrade more than in an untreated helmet. As the difference achieved in the helmet cover testing in Taiwan was a mere 1-2 degrees, 10 degrees is indeed a massive improvement factor, but one can easily imagine, that such an exotic method did not lend itself to mass production in terms of production time and cost.
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