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Helmets.org

WABA Helmet Committee

The WABA Helmet Update

Vol. 3, No. 1 - April, 1985

Other issues





Time has flown, and this Update is long overdue. We will try to keep the intervals shorter in the future, since there is a lot going on in the bicycle helmet world.


ANSI and Snell Standards Published

We had said in the last Update that the ANSI and Snell standards would soon be available. Both took longer to be published than we had anticipated. A copy of the Snell standard is enclosed with this Update. The ANSI standard is only available from ANSI, since the organization will not allow it to be photocopied for circulation and we cannot afford the $7 per copy to send it out. To get a copy, send $9 (which includes $2 shipping charge) to:

    The American National Standards Institute
    1430 Broadway
    New York, NY 10018

Include a note asking for a copy of the "Z-90.4 American National Standard for Protective Headgear--for Bicyclists."

The ANSI standard provides that each helmet must absorb sufficient impact in a DOT/Snell laboratory test to meet the 300g standard used in those tests with a drop height of one meter. This is the height used by Snell as the initial screening drop for the WABA article which Bicycling published in March of 1983. In addition, the ANSI standard requires that in at least two of the four drops the helmet must impact on a rounded (hemispheric) anvil, which increases the loading on the shell at the smaller contact point dramatically, and is a much more difficult test than the flat anvil test. This will be the most critical requirement for most manufacturers, since any well-designed helmet should pass the flat anvil test easily at one meter.

The Snell standard is very similar to the ANSI Z90.4 standard, but is more difficult to meet. The drop height for the flat anvil test is two meters, and the drop for the hemispheric anvil test is 1.2 meters.

Both standards include a test of chin strap strength. The ANSI test requires that the strap withstand the jerk of a one-kilogram weight falling down a rod for a distance of one meter and hitting a fixed stop at the end of the rod. The jerk produced is probably equivalent to about 200 pounds of steady pull. The Snell standard specifies a 38 kilogram weight, dropped 70 cm., which is probably closer to the equivalent of a 300 pound steady pull. The two strap tests are consistent with the basic approach of the impact test standards, since the ANSI test should be easily met by even cheap plastic fasteners if they are of reasonable quality, but the Snell standard requires a somewhat stronger construction. Either test is easily exceeded with well made D-rings and the best quality plastic buckles.

The ANSI standard requires that one sample be immersed in water for four hours, while Snell uses a water spray to simulate riding in the rain. Both standards require that the helmet pass the tests after chilling to -10 degrees centigrade, and after warming to 50 degrees C. There are pages of technical specifications on the tests, particularly in the ANSI standard booklet.

We have already seen some results from the publication of the new ANSI standard. Several new helmets have been introduced which meet the new standard, including one from Brancale which is the first model that firm has sold in the U.S. with the effective combination of hard shell and expanded polystyrene liner. With the normal lags for design and manufacturing time, we think that the impact of the two new standards will be more evident in coming months.


New Pamphlet

Enclosed is a new version of the Consumer's Guide to Bicycle Helmets. This one has a new section on the ANSI and Snell standards. It also has some of the newer helmets now coming on the market, but is lacking results on the Vetta, the new Brancale SP-3, the NAVA, the Etto and the new Skid Lid. (We do not usually take guesses on how a helmet will perform before receiving test results from Snell, but we note that the Vetta and the new Brancale SP-3 are constructed with a hard shell and expanded polystyrene liner, the type of design which typically does well in the tests.)

As in the past,- we are hoping to promote the widest possible distribution of the pamphlet, and have added a line at the very end which says that reproduction of the pamphlet is encouraged. Again we are happy to have other non-profit bicycle groups replace the WABA information on the last panel with their own club info. We like to see a copy of the final results just to keep up with what people are doing with it. We do not have a cheap printing connection at this point, so we do not provide the pamphlets in bulk.


New Research Results from
Dr. Hodgson of Wayne State

For some months now we have been in contact with Dr. Voigt Hodgson of Wayne State University in Detroit concerning his testing of bicycle helmets. We provided Dr. Hodgson some helmet samples for his testing. Others were provided by Skid Lid. Dr. Hodgson uses test equipment of his own design which differs from the Snell equipment, particularly the headform and instrumentation used. He also uses a different method of determining the threshold of injury. We were interested to see if his results would confirm the ranking of helmets we have been presenting in WABA's articles.

Dr. Hodgson's testing did not entirely agree with the Snell rankings. His choice of the various helmets tested was the NJL Tourrite (also sold as the Premier UltraLite). This is a hard shell helmet with an inner liner of expanded polystyrene, the same construction which does well in Snell testing. As in the Snell tests, the adult Skid Lid bottomed out at higher impact levels. At lower impact levels the small size (which has thicker foam in the same size shell) did not. Dr Hodgson made some comments about the large gaps in the Skidlid's construction, but of course it is pointless to impact on the part of the headform showing bare through the holes in that design. The consumer does not need a lab test to see how much protection there is in the bare spots!

The surprising result from Hodgson's testing was his conclusion that the Bell V1-Pro did not perform as well as it did in the Snell tests. Dr. Hodgson believes that the expanded polystyrene liner of the Bell--and that of today's motorcycle helmets as well--is too dense, and does not crush enough in impacts at lower force levels. In effect, he feels that these helmets hold back too long before they begin to crush, and although they would continue to perform in very hard impacts where a softer, less dense liner would be used up and would bottom out, they run the risk of injury to the wearer in a lesser impact.

In part Hodgson's results are due to his use of a different scale for the injury threshold from that used by Snell, ANSI, DOT, and the motorcycle helmet industry. The scale Hodgson uses is controversial and is still under discussion in the testing community. This is, however, one of the areas where everyone agrees that more work should be done. The implication here is that if Hodgson's test methods are someday validated, we might find eventually that liners should be less dense than the ones used by some current helmets, including the ones we are now ranking highest in the WABA Consumers Guides. In effect we would be giving up the protection those helmets offer in the hardest impacts to improve their protection in the lesser hits.

We think that the answer to this question will come from field experience. If Hodgson is right, both bicycle and motorcycle helmet users should be experiencing brain injury in lesser accidents without significant crushing of the helmet liners. The few helmets we have seen show the opposite, with measurable crushing of the liner taking place without injury to the rider. We do not think that what we are observing in the field warrants a revision of the rankings developed with Snell's test results. Still, our observations represent a very limited sampling and a crude. means of determining the answer to a complex question. We intend to pursue this question further, and consider it the most interesting new line of inquiry in the field at present. It could lead us to start collecting helmets from field crashes, a step we have not felt warranted to date.


Helmet Article in Bicycle Rider

The Spring 1985 issue of the new magazine Bicycle Rider (published by TL Enterprises, 29901 Agoura Road, Agoura, CA 91301) carries an article titled "A Head of the Game". It was written by Joe Minton based on research done by Dr. Hugh Hurt and his research staff at the University of Southern California. Most of Dr. Hurt's recent work has been on motorcycle helmets, and his team is best known for "Motorcycle Accident Cause Factors and Identification of Countermeasures" (generally referred to as "The Hurt Study"), which includes a very thorough investigation of motorcycle helmet performance based on field studies of actual accidents. (Available through National Technical Information Service, Springfield, VA 22161 at about $35)

The Bicycle Rider article is a good one, and adds a welcome voice to the evidence presented to bicyclists supporting the use of good helmets. The author's approach differs from our own in several respects, so the article gives a new and interesting viewpoint. The differences are immediately apparent. Some of the language concerning the hazards of poor helmets is a lot more direct than WABA's cautious phraseology, which adds to the freshness of the approach.

In the research for the article Dr. Hurt did not use either ANSI or Snell standard tests. His initial drop duplicates the flat anvil part of the ANSI standard, but he did not perform the more difficult ANSI hemispheric anvil test. After that he departed from established standards entirely to use a new approach to drop heights and anvils. His staff averaged the head height observed in a number of bicyclists riding on a nearby path, and Dr. Hurt then used that height, 5'7". The anvil used was a chunk of pavement. Both decisions sacrificed standardized test results which would have facilitated comparisons, but readers may find it appealing to have the drop height equal to average head height, and use of a chunk of pavement certainly adds a harsh note of reality to the laboratory. There are no chin strap test results.

The article presents the actual observed numbers resulting from Hurt's tests, which immediately catch the reader's eye. There is an automatic tendency to rank the helmets according to these raw numbers, which must not be done in this case, since the good helmets were still a long way from bottoming out, and at the drop levels used any reading below 300 g's is exactly as good as any other reading below 300 g's. The careful reader will find this out two pages beyond the table, but must realize that without harder impacts, and without studying the oscilloscope traces accompanying the raw numbers which show the development of g forces over the split second following the impact of the helmet on the anvil the ranking of the helmets cannot be finished. We have already been told by one helmet importer that his helmet outperformed another one in the study "by 35%" because the raw numbers were 35% lower, despite the fact that both numbers were well below the 300 g threshold. We do not know if that statement reflects an excess of promotional zeal or simple ignorance, but it points up the reason we have not used raw numbers in our articles, and the reason why you must read all of Mr. Minton's article to understand the data presented.

(Note: in later years we came to appreciate the advantages of helmets that keep g's lower than 300. See our current page on The Ideal Helmet for more on that. Most researchers now believe that the 300g threshold is too high.)

We hope that the limited circulation of Bicycle Rider will not prevent this article from being widely distributed, and will try to get permission to photocopy and send the article with the next Update.


Coming Soon

The next issue of the Update will have John and Robin Spiegel's observations from the New York bicycle show. We should also have some new test results, and if possible a reprint of the article from Bicycle Rider. The children's helmet study is nearing the writeup stage. The globetrotting Tom Balderston may be returning. Stay tuned!


Randy Swart
Editor


Printed on recycled paper.



This page was reformatted on: April 30, 2015.
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