Helmets Perform in the Lab First, Then on the Track
by Jennifer M. Faye
Anticipating the possibility of a serious crash and protecting the driver from potential danger has become a familiar part of motorsports. Race car drivers at all levels of competition are susceptible to injuries mainly from impact and fire. To lessen the shock to their bodies from hard blows, drivers tightly strap themselves in their cars with strong five, six, or even seven-point, 3-inch wide harnesses and are surrounded by impact-absorbing seats and roll bar padding.
In the frightening event of a fire, time to escape is extended a few precious seconds by wearing insulating Nomex suits, gloves, and shoes. The driver’s helmet, arguably the most important element of the safety personal equipment ensemble, can protect the driver’s head from both impact and fire.
Helmets are comprised of different components, each with its own purpose. The hard outer shell provides the primary defense against impact. It is filled with Energy Absorbing Material (EAM), sometimes called the liner, that absorbs impact energy and reduces trauma to the head. The helmet’s padding is sometimes confused with the liner. Unlike the liner, the padding does not absorb energy. The padding is intended for sizing and comfort only. The padding and EAM are covered by a fire retardant lining which is the only part of the helmet that comes in contact with the wearer’s head.
On full face helmets, the clear shield provides facial protection while allowing the driver to see the track ahead. Then there is the retention system which is made up of the straps and hardware that secure the helmet to the driver’s head.
Most manufacturers construct these components with state-of-the-art composite materials that make the helmets light and comfortable to wear. Of course, the intended function of the helmet is much more important than a comfortable fit. Reputable manufacturers ensure that their helmets provide the necessary protection in a crash by submitting samples of their products for performance testing and by participating in a quality assurance certification program.
One such program for helmets is administered by the SFI Foundation, Inc. (SFI). SFI has long been recognized as a leader in setting minimum performance standards in the automotive aftermarket and motorsports industries for all kinds of driver protective equipment and automotive performance parts.
Helmets that are certified by the manufacturer to an SFI Quality Assurance Specification have passed a set of strict testing procedures that were developed by a committee of experts in the helmet industry. There are two types of SFI specifications that pertain to helmets: flame resistant (FR) and non-flame resistant (non-FR.) The FR specification is designated SFI Spec 31.1, Flame Resistant Motorsports Helmets. The non-FR helmet spec is 41.1, Motorsports Helmets. Each Spec (31.1 and 41.1) includes both open-face helmets and full-face helmets.
The two helmet specifications require the same criteria for impact protection, however, since Spec 41.1 helmets are non-FR, they are primarily used in motorcycle applications. However, some santioning bodies may permit the use of these helmets in various auto racing classes. It is always best to check sanctioning body rules to determine exactly which helmet Spec you’re required to use for your race class.
Over the past few years, the SFI helmet specs have gone through a couple of nomenclature revisions. You might recall that helemts used be certified under SFI Specs 31.1A and 31.2A. Both were for FR motorsports helmets, with the only difference being that 31.1A was for open-face helmets and 31.2A was for closed-face helmets. For simplicity, the two specs were merged into one Spec 31.1. This is also true for Specs 41.1A (open face) and 41.2A (closed face) which were merged into Spec 41.1.
On the certification labels, the “A” was dropped in lieu of showing the year 2005. The technical requirements of the specs were not changed, but only the nomenclature in an effort to make the spec designations easier to understand and to have fewer labels to look for during tech inspection at the track.
You might also have a helmet with an SFI 31.1, 31.2, 41.1, or 41.2 label on it without the A designation or any year. These labels are from prior to 2002. In 2002 the specs were revised to include a shell penetration test and the labels were changed to 31.1A, 31.2A, 41.1A and 41.2A to reflect the spec revision. While there was no year on the SFI label itself, the date of manufacture could either be traced by the serial number found on the SFI label, or the date itself should be marked on the helmet by the original manufacturer.
Beginning in 2005, we have the year designated on the SFI label itself to aid in tech inspection and determining the age of the helmet. The year on the labels will be changed every five years (2005, 2010, 2015, etc.). This is similar to the labeling system used by the Snell Foundation.
It may also be helpful to know which SFI Spec numbers (past and present) and Snell Specs are comparable in testing and certification requirements. SFI Specs 31.1, 31.2, 31.1A, 31.2A and 31.1/2005 are comparable to Snell SA. SFI Specs 41.1, 41.2, 41.1A, 41.2A and 41.1/2005 can be compared to Snell M.
It should be noted that SFI also has a Spec 24.1 for Youth Helmets (see the May, 2003 news article, SFI Helmet Specs Update, on this website’s News Archives page for more information about the youth helmet spec.)
The changing SFI helmet labels has been a little confusing, but now that SFI has what it thinks is a simpler identification system, it should remain in place for years to come.
Helmets tested to the SFI specs are required to resist the elements that they would be exposed to in normal use. They include low and high temperatures, and moisture. Besides environmental considerations, helmets must resist fluids used in and around motor vehicles which which they may come in contact.
Helmets exposed to these environments are then subjected to a series of impact attenuation tests. Impact attenuation is the ability of a helmet to absorb the energy of an impact, thus reducing the force to the wearer’s head. In these tests, helmets are fitted on metal headforms and the helmet/headform assemblies are dropped on several steel anvils of various shapes. The anvils simulate different surfaces that a helmet could come in contact with during a crash. The impacts are guided free falls dropped from controlled heights on a testing apparatus.
The headform is equipped with a transducer to record peak acceleration, measured in g’s. Peak acceleration is the amount of energy transferred to the test headform when it impacts the test surface. For a helmet to pass, the headform must receive no more than 300 g’s of energy for any given drop. Additionally, the peak acceleration for the average of all drops for a single helmet may not exceed 275 g’s.
Since the purpose of a helmet is to protect a racer from both impact and fire, the SFI specs include flame resistance tests. A 790°C propane flame is applied to the shell, trim, and face shield (on a full face helmet). The exact time that the flame is applied to the samples varies depending on the component. For example, the required thermal load for the trim is 15 seconds while the face shield is subjected to flame for 45 seconds.
Any flames that develop on the helmet components must self-extinguish and the time it takes for the flames to go out is measured. This is called after-flame time. The after-flame time must be less than a given time for each component (all under 20 seconds or less) if the helmet is to pass this portion of the spec.
The lining is subjected to a radiant heat test in addition to the direct flame test. This is the same Thermal Protective Performance (TPP) test that is required in the SFI Specification 3.2A for Driver Suits. In fact, the helmet liner must meet the same criteria as a 3.2A/1 driver suit, or a TPP of 6.0 or greater.
The face shield also undergoes a number of specialized tests in the SFI specifications for helmets. The fastening mechanism must keep the shield latched to the helmet in the event of an impact. Also, the shield must notallow penetration from either a dropped projectile or a steelball that is fired at the shield during penetration testing.
Other tests required by the helmet specs are visual clearance of the facial opening, chin strap strength, and a chin bar impact test (full-face helmets only.) It is reassuring for racers to know that they are protected by helmets that have undergone very extensive and thorough testing.
The SFI Quality Assurance Program also requires the manufacturers to retest their helmets periodically. This ensures that their products meet the specification requirements on an ongoing basis. Manufacturers who participate in the SFI Program and certify their helmets to the SFI specifications will display conformance labels on the inside of their helmets. The SFI label is proof to consumers that they are purchasing a quality-assured product that has been tested in a continuing effort to improve motorsports safety.
