Helmets are 37 percent effective in preventing motorcycle deaths and 67 percent effective in preventing brain injuries caused by motorcycle accidents. Furthermore, the American Academy of Neurology states that football helmets reduce the risk of skull fracture by 60 to 70 percent and reduce focal brain tissue bruising by 70 to 80 percent.
However, research shows that helmets can significantly reduce the severity of injuries sustained from head trauma. A helmet has a hard, plastic shell on the outside and foam on the inside. If you hit your head, the materials in your helmet will help to dissipate the force and energy of the impact, which reduces the force applied to the skull.
The foam works to cushion the blow to the head, while the smooth, plastic outer shell allows your head to safely skid across the surface of impact without jerking your neck. Essentially, if you do hit your head, your helmet will take the brunt of the impact, reducing the amount of energy that collides with your head.
No helmet is concussion-proof. A concussion is the result of internal jostling of the brain, so a helmet cannot prevent a concussion from happening. This has led many to believe that helmets are ineffective. However, a helmet can reduce the amount of force applied to the brain and protect against severe cuts, skull fractures and broken facial bones.
Some are just hard shells with a suspension headband that provides the fit and keeps some space inside for air to circulate. Construction helmets are of this type, and do a fine job when somebody drops a brick on your head or you bump hard against an overhanging steel beam. Just don't fall off a bicycle with one, since they will not handle the impact of falling on pavement.
The foams in some helmets are crushable but do not ever recover. If you crash a bike helmet made with the usual expanded polystyrene foam, the foam is trashed and you can't use it again. If the helmet is made for hockey or skateboarding it has a slow-rebound squishy foam called butyl nitrate foam, or perhaps expanded polypropylene foam. Either will recover slowly after a blow and can be reused. Construction helmets are ok as long as the shell is not cracked and the suspension is not damaged.
Different types of helmets seem indistinguishable to most consumers, and you can't test the impact protection unless you have a lab and are willing to destroy the helmet. So the industry uses standards to designate performance levels.
What are helmet standards? Standards define laboratory tests for helmets that are matched to the use intended. If a helmet can pass the tests for a sport or activity, it provides adequate impact protection. A construction helmet will not pass the more severe bicycle helmet tests.
A bicycle helmet will not pass the more severe motorcycle helmet tests. None of them provides the protection against shrapnel that is required of a military helmet. Standards also define other tests for such parameters as strap strength, shell configuration, visor attachments, and the head coverage that must be provided, depending on the activity. Standards are developed and published by various standards-setting organizations.
There are military specifications for helmets for infantry, pilots and lots of others. There is a NASA standard for astronaut helmets. There are standards from a number of sports organizations for helmets related to their sport. A typical standard specifies impact tests, strap tests, characteristics of materials to be used, required coverage, labeling and other requirements.
Some have tests to simulate low temperature performance, hot performance, wet performance and sunlight ageing. Test equipment is described as well as the severity of the testing. For a look at a complete helmet standard, check out the Snell Memorial Foundation site , where their standards are all available. For a look at a point-by-point comparison of bicycle helmet standards, check out our short comparison or our more detailed long comparison. How is testing done? There are various types of tests included in most standards.
For impact testing , the typical test apparatus consists of a rig that drops a helmeted headform in a guided freefall to an anvil on the floor. You strap the helmet on the headform, turn it upside down so the helmet hits the anvil first and drop it onto the anvil. The helmet is oriented before each drop to test it's most vulnerable areas. The variables in the test include the drop height and the shape of the anvil: flat, round, ridge-shaped, pointy or in one case a shape that simulates a horseshoe.
Instruments inside the headform register how much shock the headform experienced. The unit of measurement is normally the g, for gravity. We have put up a page explaining g's. This is why at HelmetGeeks. The law of conservation of energy applies in the event an opposing force stops your motion during a crash.
This law states that energy can neither be created nor destroyed. When you come to an abrupt stop, your kinetic energy the energy of our motion on your motorcycle simply changes form. It interacts with the force the ground is exerting, and the kinetic energy becomes a part of the force that hurts us.
The hard outer shell of the helmet stops nearly instantly when it hits the ground. Your head keeps moving within the outer shell of the helmet as it stops. This is because of the padding as well as how a well-fitting helmet holds your head.
Your head takes longer to stop. Because the force of the impact is distributed over the area of the helmet you are less likely to suffer a broken skull. Motorcycle helmet shape and design play the biggest role in protection. The EPS foam in your helmet compresses on impact, which allows your head to come to a stop more slowly than it otherwise would have.
This dramatically reduces your acceleration. Since force is equal to mass times acceleration, it drastically reduces the force. The curved shape of most helmets distributes the force around its hard surface, rather than just at the point of impact. Whereas the laws of physics cannot be broken, wearing a motorcycle helmet when you ride can mitigate them. Many things are strong enough to bring your motion to a complete and sudden stop in case of a crash.
Helmets can take that force and minimize it by spreading the impact over your helmet surface. They also increase the time it takes your skull to stop because the foam condenses and disperses the energy. Motion always involves physics. Helmets can factor positively into the physics in play when you crash. Helmets Work in Two Ways.
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