According to GB 2811-2007 "helmet" in the definition, helmet refers to "the human head by falling objects and other factors caused by the injury to play a protective role in the cap". In the basic technical performance, the standard stipulates that the helmet by high temperature, low temperature, water immersion, ultraviolet radiation pretreatment to do impact testing, the force transmitted to the head mold does not exceed 4900N, the cap shell shall not have fragments off. After puncture test, the steel cone shall not touch the surface of the head mold, the cap shell shall not have fragments off. In addition, the helmet should have anti-static, electrical insulation, flame retardant and low temperature resistance and other properties.
Safety helmet protection principle is closely related to its shape. The cap shell is oval or hemispherical, smooth surface, when the object falls on the cap shell, the object immediately slide off, will not stay on the cap. And because of the approximate sphere, the object hit to the cap shell force will be transferred to the surrounding. According to statistics, through the cap liner buffer to reduce the force of up to 2 / 3 above. The standard also provides safety helmet in the impact test, the force transmitted to the head mold does not exceed 4900N, the cap shell shall not have debris off.
Safety helmet is for motorcycle, light ride, battery car and other vehicles drivers and riders to provide security. Under normal circumstances, the weight of a helmet in about 400 grams, a safety helmet weight to reach more than 1000 grams, this is because the safety helmet increases the head protection zone, goggles and other additional accessories, while the helmet is not. At the same time, the safety helmet is a 360-degree frontal and side protection for the head in all directions.
How to choose？
At present, the safety helmet worn by the driver of electric bicycles are mostly motorcycle passenger helmets and sports helmets. Among them, motorcycle passenger helmets for compulsory certification (CCC) products, according to the performance and use of the object can be divided into Class A helmets and Class B. Class A helmets are used for the total exhaust volume of 125 ml (including 125 ml) or more motorcycle occupants, the shape of the full helmet and half helmet. Class B helmets are used for the total exhaust volume of 125 ml or less motorcycle occupants, the shape of the half helmet. Helmets should be shell, cushioning layer, comfortable padding, wearing devices, goggles, etc. The shell is made of tough, water-resistant, heat-resistant, cold-resistant and can absorb more impact energy materials.
Sports helmets according to GB/T10000 and minors' head circumference size is divided into large, medium, small and very small four specifications, helmets for the shell, cushioning layer, comfort padding, wearing devices and other components, the shell using tough texture, with water, heat and cold resistant materials made [3] .
Bicycle helmets also have the corresponding national standards, namely the national standard GB 24429-2009 "sports helmets bicycle, skateboard, roller skating sports helmets safety requirements and test methods". There is no corresponding national standard for electric vehicle helmets, so consumers can buy motorcycle or bicycle helmets that meet the standard according to their needs
