Motorcycle Helmets Knowledge

1.Why use a helmet?

Helmets are useful as safety gear to prevent injuries in an uncontrolled environment. If you can't prevent a crash or impact, but you know it will occur, a helmet can prevent or minimize injury to the head and brain.

We can not emphasize enough that the first step in preventing injury is to minimize the probability of crashing or being impacted. Not hitting something hard is infinitely better than hitting with a helmet on!

2. How does a helmet work?

Human brains can be injured by impact, of course, or by exceptionally violent rotation of the head, when the brain remains stationary, giving blood vessels and nerves a yank. Internal blood vessels and nerves yank parts of the brain around too in different ways, straining the vessels and nerves in the process.

Helmets designed to handle major crash energy generally contain a layer of crushable foam. When you crash and hit a hard surface, the foam part of a helmet crushes, controlling the crash energy and extending your head's stopping time by about six thousandths of a second (6 ms) to reduce the peak impact to the brain. Rotational forces and internal strains are likely to be reduced by the crushing.

In a lab test graphs of the impact energy the brain sees look like this, with a smooth curve extending over 6ms for the good helmet (on the left below), and a huge spike for a bare head (right).Somewhere about half way up that spike is where permanent brain damage begins.

Thicker foam is better, giving your head more room and milliseconds to stop. If the foam is 15mm thick it obviously has to stop you in half the distance of a 30mm thick foam. Basic laws of physics result in more force to the brain if the stopping distance is shorter, whatever the "miracle" foam may be. Less dense foam can be better as well, since it can crush in a lesser impact, but it has to be thicker in order to avoid crushing down and "bottoming out" in a harder impact. The ideal "rate sensitive" foam would tune itself for the impact, stiffening up for a hard one and yielding more in a more moderate hit.

If the helmet is very thick, the outer circumference of the head is in effect extended. If the helmet then does not skid on the crash surface, that will wrench the head more, contributing to strain on the neck and possibly to rotational forces on the brain. In short, there are always tradeoffs, and a super-thick helmet will probably not be optimal. It will also fail on consumer acceptance.

If there are squishy fitting pads inside the helmet they are there for comfort, not impact. The impact is so hard and sharp that squishy foam just bottoms out immediately. In most helmets a smooth plastic skin holds the helmet's foam together as it crushes and helps it skid easily on the crash surface, rather than jerking your head to a stop. In activities that involve forward speed on rough pavement, rounder helmets are safer, since they skid more easily. The straps keep the helmet on your head during the crash sequence. A helmet must fit well and be level on your head for the whole head to remain covered after that first impact.

Helmets designed for lesser impacts do not necessarily have foam inside. 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. 

3.What are helmet standards?

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.

DOT Helmet Standard:  

This stands for “Department of Transportation,”  but the standard is FMVSS 218, the Federal Motor Vehicle Safety Standard #218, Motorcycle Helmets, and it is applicable to helmets sold in the U.S. for on-road use.

In an effort to make counterfeit labeling of non-compliant helmets more difficult and legally risky to those who do it, the DOT label displayed on the back of the helmet must now include, in order from top to bottom:

The manufacturer’s name
Model number or name
“DOT” below the manufacturer’s name
“FMVSS 218” centered below DOT
The word “Certified” below FMVSS 218

ECE 22.05 Helmet Standard:  

ECE stands for “Economic Commission for Europe,” which was created under a United Nations agreement in 1958.  The 22.05 part refers to the specific regulation that the standards for testing are described in.

The ECE standard, which is accepted in 47 countries, is similar to the DOT standard in several ways, for example: like the DOT standard, peripheral vision through an arc of 105° from the helmet mid-line is required.  Also, environmental conditioning of helmets to be tested is required similar to the DOT standard and certain labeling requirements apply, as well.

Impact absorption testing is performed in a manner very similar to the DOT standard, involving a drop test from a fixed height on a steel anvil with a head form fitted inside to measure the energy transmitted.  Peak acceleration energy at the head form allowed to pass the test is 275 G.  Impact absorption and rotational forces are also tested at points where any surfaces or parts project from the shell of the helmet.

Snell (Snell Memorial Foundation M2010) Helmet Standard:  

The Snell Memorial Foundation is a private, non-profit organization formed in 1957 dedicated to improving helmet safety.
Snell goes beyond the governmental standard-setting approach and is available to assist manufacturers with helmet development by offering prototype testing.
The Snell label identifies the type of application the helmet is certified for, using letter codes:

M=motorcycle
SA=special application
SAH=special application, frontal head restraint system
K=karting
CMR=children’s Motorsports restricted

CMS=children’s Motorsports standard

4.How is Helmet  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 head-form in a guided free fall to an anvil on the floor. You strap the helmet on the head-form  turn it upside down so the helmet hits the anvil first and drop it onto the anvil.

There are various tests conducted for helmets safety standard. Below link will give you more details about Helmet Testing.

http://www.smf.org/testing

5. Correct choice of Helmet

As you all know, wearing a helmet is really important. It can reduce the risk of a serious head injury or even save your life. This is why we want to inform you better on choosing the right helmet for you.

SIZE & FIT: Size and fit are the most important features you should look for in a helmet. Avoid buying/wearing a helmet that is not the right size for you. You can make the fit more custom using pads and straps that would keep the helmet in place.

ADJUST THE STRAPS: While riding the straps should always be locked, there is no point on using a helmet if you are not locking it. The straps should never be too tight or too loose on your chin. Make sure it “clicks” correctly and holds pressure properly – you’ll have to replace it if it doesn't.

CORRECT POSITION: Helmet right position it’s approximately an inch above the eyebrows, any other position might be dangerous upon impact.

WEIGHT: Helmet weight is also important, helmets which are too heavy may cause neck injuries and be so uncomfortable that you wouldn't want to wear it.

CERTIFIED HELMETS: Although certification shouldn't be an obstacle for you to buy your helmet, we highly recommend to look for helmets that have been tested and certified, in sum a helmet that fulfills all the above requirements.

FULL FACE HELMETS: For higher speeds it is highly recommended to use a helmet that covers your entire head.