by 9zer0 » Sun Dec 25, 2005 11:22 am
Taken from my friend the good Dr on Perthstreetbikes, it is a little long winded but makes for excellent reading when making your big decision.
I know this topic has been done to death a hundred times and if anyone wants to read the debate it is here Stds Debate .I'm not really keen on discussing it much further but I've done some research over the last week, because my information was based on summaries of tests and not a complete understanding.
Thanks to UWAs injury prevention centres subscription, I have acquired the Stds Aus helmet standards in full (standard needed to get approved in Aus), and a more detailed version of the Snell foundation standards and found that the summaries I have read were spot on.
The Snell foundation standards measure the same parameters as the Stds Aus standards. Nearly all of the acceptable limits in the tests are the same. The few that are different the Stds Aus ones are safer.
The testing rigs are very similar, though the Snell foundation ones are considerably cruder (they were invented in 1964 instead of 1988+) and thus the Stds Aus tests are more repeatable and accurate.
The Stds Aus testing has been updated often up until the year 2000, the tests have been the same since then. The Snell foundation has changed the numbers on the testing criteria (i.e. M2000 changed to M2005 in 2005) but the tests themselves have not changed.
So, in summary after an extended painful read. The Snell stds are the same or inferior to the standards needed to sell a helmet in Australia, so a Snell sticker means nothing if the helmet is purchased in Australia.
The main reason people will disagree with this (and some very passionately) is because they are mistaking Stds Aus for DOT standards (the standards needed to sell a helmet in America). The DOT standards are less demanding than both the Snell and Stds Aus. There have been many comparisons between the Snell and DOT standards which show that the Snell standards (and thus Stds Aus) are probably superior.
If anyone would like to read the two standards they are very welcome. They are however long, at 100+pages for Stds Aus and 34pages for Snell, but if you really want to know what you are on about I urge you to read them. Next week I will make a copy to loan out to interested people (I can't post them up for copyright reasons).
This does not resolve the argument if European standards (which are completely different) are superior to both Snell and Stds Aus standards, but the article posted here Helmet article goes along way to resolve that issue.
Please do not post over opinionated and undereducated replies to this topic, if you would like to disagree with me please read the data first.
Once again the most important safety issue when purchasing a helmet is fit, the fit is determined by the shape of the last the company uses and how closely that resembles your head, price of helmet has nothing to do with this. You should buy a helmet you can afford to throw away if it is in a minor accident. Also UV light damages the materials, try keeping your helmet out of the sun/ tanning salons (when not in use of course).
As other protective equipment like boots and gloves are not regulated the quality of these items is more variable. I advise you spend extra dosh on a better jacket instead of a more expensive helmet.
End of lecture, you may go to lunch now
Dr Evil.
His 2nd post
I've been asked to clarify the advice I gave above, I'd initially thought I'd just make the point that Snell=Stds Aus but then got carried away.
Am I suggesting you buy the cheapest lid you can find? No, some cheap lids can fit heads pretty poorly and if it doesn't fit your head, don't buy it. You should look at helmet construction not price or lightning bolts on the graphics.
Am I saying just find a cheap one that looks pretty? No, see reason above.
Am I saying plastic out performs fibreglass? Yes, but only in extreme situations(see below)
What lid do I have? an AXO, single density plastic, I knew nothing about the dual density foam when I bought it and they were just on the market.
Plastic vs. Glass- The plastic and glass(fibre and I believe carbon) are built to the standard they need to comply to. It is a toss up between the springy effect (impact attenuation) the material gives when it hits the road, and the penetrative resistance it has to sharp objects. The springy effect of the shell is good because it makes your head decelerate slower, the penetrative resistance is good if your head runs into a rod protruding out the back of a truck. If we could switch lids for each event it'd be great, but we can’t so it's a compromise. To get the materials to behave the same the plastic must be thicker than the glass, so it is.
The EC study done in 93-01 showed that in rare high impact accidents that the penetrative integrity of helmets can be exceeded. The vast majority of these accidents were unsurvivable, however a few were survived. They noted that the glass lids had cracked under high impact (or with sharp objects) but the plastic ones had deformed permanently but rarely split open. So they tested the materials out to destruction, they drop a heavy block splitter on them from a great height and test the g forces experienced by the headform inside the lid (because that’s what people die from). They found that the stretching of the plastic and associated spreading of the impact decreased the final g's experienced by the headform. The glass once it does crack either lets the penetrating object impact on a very small area of foam, or lets one side of the glass press on the foam. Both of these options reduce the impact attenuation of the foam liner and the deceleration becomes very rapid. So in very rare cases of very high/sharp impact accidents the plastic was superior, otherwise the materials behave very similarly.
I am about to talk to the Shoei rep to discuss the properties of the triple composite shell they are now making. It seems that they have glass, with Kevlar imbedded into it, so it won’t crack, giving your lid the UV resistance and shiny glass look, with better high impact penetrative integrity than plastic.
Why don't the high end helmet market change to plastic? Because they have massive machines that pump out thousands of glass single density lids every day that would be prohibitively expensive to replace.
I've not been asked about dual density foam but as I have the study here I'll tell you why it's better. It will pass Stds Aus. For the same impact it has 5% more crushing of the foam (good for reducing g's of your head), 10% extra elliptical depression within the foam (similar to impact attenuation), a massive 20% greater impact time duration (reflects g's your head experiences), and less slab cracking (crude test but means you are less likely to crack the pavement when your head hits it=less force transmitted to head).
To make dual density foam liners you need 2 of the same machines that are used to make single density liners, and someone to glue them together.
Which helmet should you try/buy, I briefly asked around (thanks jono) and found 4 helmets that meet the criteria above, the Shoei X-11 and XR1000, and also the HJC AC11 and FG12, I'm sure they are more out there but the manufacturers are taking their time to change to dual density foam, so I believe the bike riding public should show them that they have to, or they wont sell anything.
Thanks to anyone who bothered reading. I'd be very happy to discuss anything other than the Snell/Stds Aus comparison (unless it's with someone who has read them).
Hello 911? ahh its Quagmeyer - yeah its in the window this time.