Quote:
Originally Posted by gfloyd2002
I may be missing something, but why not test the chin guard area since ECE does? And why would ECE limit chin guard area testing to full face helmets? Seems like a huge flaw in the Sharp testing and rating system. The chin guard is the most common impact area. They should give a flip up helmet a fail for that test and drop the star rating, and also make sure the full face helmets get rated based on that very important area also.
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I agree that the chin guard area should be implemented as part of the overall testing. The COST 327 report found that the chin area, although still a frequent area of impact at 15.4%, was not the most common. Nevertheless, it also determined that a high proportion of fatalities sustained base of the skull fractures, which were almost always caused by direct impact to the chin area. The report stressed that certification standards should include a test of the chin area. Currently, ECE 22.05 and the British Standard includes the chin guard testing. The older ECE regulation 22.04 did not include a chin impact test or a test for rotation inducing forces and was largely considered as inferior to the British Standard BS 6658:1985.
From what I've gathered, the only assumption I can make about why SHARP does not include a chin guard test is that the COST 327 report did not test impacts to the chin area as the 05 series of amendments to ECE regulation 22 includes the chin area tests. SHARP feels that any helmet conforming to ECE 22.05 already offers adequate chin guard protection. Again, like I said earlier, SHARP testing only offers some value when viewed as an additional rating to a helmet already conforming to ECE 22.05 standard. I do like the fact that SHARP conducts the testing at a velocity of 8.5 m/s and also at lower speeds of 6.0 m/s as per the recommendations of the COST 327 report. By itself, when viewed as an overall helmet safety scheme, the SHARP system is not thorough enough. In my opinion, ECE 22.05 is probably the most thorough and realistic standard at present.
Moving back to the original topic of this thread and Snell debate, the criticism here is that the shell penetration test and conducting multiple impacts to the same point creates "optimised" helmets that are too stiff and thus are not as effective as absorbing energy at lower impact speeds. COST 327 compared the stiffness of glass fibre helmets of ECE 22.04 standard to those of SNELL 95 type and found little difference in the mean rotational acceleration and mean tangential force measurements. Of course, we don't know if this relationship still holds true today for glass fibre helmets of ECE 22.05 standard compared to those of SNELL 2010 or 2005. At the same time, I've yet to see any findings that suggest a SNELL 2005 or 2010 standard helmet transmits more energy than a supposedly softer shell ECE 22.05 helmet. Obviously, the topic and theory of Snell helmets is still debatable for some. It's important to note though that aside from the shell penetration test and multiple impact test that Snell conducts, the linear impact velocities and peak acceleration criteria are similar with values found in ECE 22.05 testing. Snell 2010 conducts linear impact testing at a velocity of 7.75 m/s but deviation is allowed to 7.48 m/s whereas ECE conducts the tests at a minimum of 7.5 m/s and allowing a positive deviation of .15 m/s. Both testing standards specify a maximum peak force acceleration of 275 G.
If I've read the Snell 2010 standards correctly, then my biggest gripe against Snell is that it does not include a test made specifically to test for rotation inducing forces on the head. The impact tests are only done in a straight line/trajectory. In real life, we know that the head and helmet can strike a surface not just dead on but also at oblique angles resulting in significant brain and head injuries due to the rotational and frictional forces that are induced. Examples of injuries include subdural haematoma and intracerebral shearing. This was supported in the findings of the COST 327 report. Both ECE 22.05 and SHARP conduct oblique impact tests, although SHARP claims that their testing method is more stringent and the helmet is also dropped against a sandpaper surface to mimic the frictional forces of the helmet hitting pavement. Their hope is that manufacturers start to develop helmets that slide better and thereby reduce the amount of friction of the outer helmet surface. ECE includes a frictional test as well but allows the option for either impacting the helmet against an abrasive anvil or a carriage abrading the outer surface of the helmet.
Regarding the chin bar tests, Snell 2010 standards only conduct their chin bar tests for full faced helmets. It might be the same for ECE 22.05, but the difference is if the chin bar has not been tested under ECE 22.05, then it must be marked somewhere on the outer surface either with the words "Does not protect chin from impacts" or a symbol showing the helmet with an X across the chin bar. In my view, the chin bar test conducted in ECE 22.05 is also more stringent than that conducted in Snell. In ECE testing, the chin area is impacted at 5.5 m/s and the measured transmitted energy to the head must not exceed 275 g. In Snell testing, a 5 kg weight is dropped onto the chin at 3.5 m/s, however, Snell does not test the transmitted energy to the head but rather only the amount of downward deflection of the chin bar.