Friday, October 24, 2008

16 A Distingerated Bicycle Helmet



Thanks to Sandra from Australia (of Competitive Cycling fame) for sending me an image of a helmet involved in a crash. Its branded Tioga. Her friend was descending from Mt. Coot-tha when the person took a bad spill that ended up putting some serious cuts and bruises to the face and breaking a couple of vertebrates as well.

The lid is completely destroyed. Whether a helmet saves your life or not may be still moot, but keep staring at the picture above. 

What do you think? Did it do its "as designed job"? Does it look too fragile? Perhaps one of the commentators, Richard Keatinge, from my "How a Bicycle Helmet Works" post will be very interested in this image. Comment away.

16 comments:

  1. Anonymous4:56 PM

    It doesn't look like the helmet had much of a chance to deform, the top seems to have sheared off. The idea of the foam helmets is they compress to absorb impact energy. That looks like a manufacturing defect to me.

    I'll stick to name brand helmets...

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  2. I went over my handlebars in Spain a few years ago and landed on the left side of my head. The helmet, a Bell, came off after impact. I picked it up and it looked scratched and chipped on the outside but no big deal. Turning it over it looked like a bomb had gone off inside--the foam was totally deformed. I am also puzzled by the damage to the helmet pictured.

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  3. Anonymous11:32 PM

    Ron,

    This image is looking very suspicious to me at best.

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  4. Tom in SJ12:20 AM

    I didn't read anything about brain trauma, so it worked, plain and simple. Possibly a face plant (endo) where the forehead impacted first, the helmet shattered from the impact, then her face slid across the ground. Where is the rest of the plastic? The scratches on the plastic always tell the true story on where the impact was.

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  5. I'm an epidemiologist, not an engineer, so on this point I'll quote some engineers and leave you to make up your own mind: "In an impact situation involving a motorcycle or bicycle helmet, cracking through the thickness of the foam liner (slabcracking) is undesirable as it renders the foam liner of the helmet useless in its ability to further absorb an impact force. As a result the foam is unable to distribute the focal impact over a larger area and to decelerate the blow at the point of impact...
    The majority of cracking displayed by samples was in the shape of an arc outlining the spherical
    headform on impact. Arc-cracking has minimal effect, as it is part of the crushing process.
    However, cracks developing partly or fully through the thickness of the foam-slab renders it
    useless in crushing and absorbing impact forces." (from http://www.atsb.gov.au/publications/2001/pdf/helmet_liner.pdf Improved Shock Absorbing Liner for Helmets. Morgan D.E., Szabo L.S. July 2001. Australian Transport Safety Bureau.) Further relevant quotations at http://en.wikipedia.org/wiki/Bicycle_helmet#Criticism_of_current_standards.3B_new_designs

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  6. I'm still am a firm believer in helmets. Anything just has to be better than nothing when it comes to your head hitting a hard immovable surface.

    I've never had to test out my bike helmet seriously but I did go down through the ditch on a motorcycle once. I did land on my head hard enough to tear a sod out of the ground which was hanging out from between the visor and the top of the helmet.

    I suffered no head injury but was pretty beat up everywhere else.

    There is a helmet law here in Nova Scotia for bikes and now the CSA has a standard for workplace hard hats that they must also have a foam liner much the same as a bike helmet so their must be some advantage to the material.

    -B

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  7. "Her friend was descending from Mt. Coot-tha when the person took a bad spill..."

    I'm assuming a lot here but... Descending on a road bike you can quite easily get up to speeds there are more motorcycle territory than bike territory. This could be a case of the helmet being involved in a crash that was out of the impact range it was designed for.
    Also, I wonder if something fairly solid didn't catch in one of the vents and tear the helmet apart or something.

    Either way, the rider survived what looks/sounds to have been a pretty scary crash so we can't really judge the helmet to harshly, especially without more info on what really happened.

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  8. I didn't see the actual crash but from what I have been described, my husband's work colleague hit a tree head on, coming over his handlebar. He impacted slightly to the back of the helmet first (in some type of forward roll), which pushed the helmet forward into his face and with his chin towards his chest he compressed and fractured two vertebras in his neck. He reckons he was doing about 60 km/h when the tyre blew. Knowing the guy and having seen him on the side of the road in pretty bad state I believe the picture and state of helmet is genuine.

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  9. Thanks! That fills in some questions we had about how he crashed. Wish we had another closeup, because to some it would seem like the foam just cracked, and to some, it may seem like it crushed and then fell apart from the helmet. Thanks Richard for your insight, and Surestick, your point goes with my thinking of putting too many vents than needed in a helmet that I feel takes something away from the structural rigidity of the helmet.

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  10. I would say that the foam in the helmet certainly did its job, keeping the person from getting brain damage or being killed due to significant brain injury. The shell, I thought, was supposed to be intact, but depending on the impact, I guess not all shells can do that. In my opinion, if the person is still alive, it did its job regardless of the outcome of the helmet. Don't forget too, helmets are designed to sustain one collision, and you should never wear a helmet that has been in a crash, no matter how little the impact was.

    I'd be dead without the awesome technology put into the helmets today, so I'm glad that the technology has gotten a lot better. No matter how "ridiculous" you think the helmet makes you look, always choose safety over fashion!

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  11. I believe the better name brand helmets have a skeleton of some kind in the foam to keep the foam from breaking apart like this.

    Last summer I went over the bars at about 35mph landed on my head then my back. The inner halo size adjuster broke loose from the helmet but the rest stayed in tack which I think it was designed to work.

    It was a Bell Sweep R

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  12. Zach and Bill : I know now you both are crash survivors. Well, its great to have you guys commenting here.

    Bill : You sure are lucky to have that helmet work for you. I've had a diametrically opposite experience with the same. Infact, even though I didn't crash on it yet, the very type of cracking Richard Keatinge has described above has been taking toll on the foam, especially the unsupported ones on the rear side. The new Bell Volt's have better supported shells and foams in the rear. I had briefly talked about the design of the Bell Volt in an earlier post. I referenced the foam cracking on my own helmet in that post as well, towards the end in a link.

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  13. It is hard to believe look at the remnants but reading Groover's comment and how he crashed I can see why it may look like this. Just glad to hear the cyclist lived and will most likely recover fully.

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  14. Bill : I think you're right. These new lightweight helmet models have a kevlar skeleton.

    Here's an image for those who don't know what we're talking about.

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  15. Anonymous7:51 PM

    Helmet foam (unlike "foam rubber") is made to partially aborb energy by cracking. Under the low speed impacts that helmets are really made for, the helmet normally won't come apart. But it is substantially weakened by the impact which is why you should replace a helmet after an impact, even if it looks fine.

    A helmet shattering like this one is normal for this powerful an impact (40 mph into a solid object). It probably absorbed quite a bit of energy and did give the wearer some protection. But bycycle helmet design standards are such that they are not really made for this powerful an impact. The legal design and testing requirements are more based around low speed falls.

    My two cents on the whole helmet debate - helmets save lives. But helmet laws kill by discouraging cycling, reducing the number of bikes on the road, which has been shown to make riding more dangerous for those that continue to do it.

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  16. Anonymous9:39 PM

    Anon : New studies from groups of hospitals show that an individual is more likely to suffer brain injury without wearing a helmet. Saving lives vs discouraging cycling...you weigh whats more important.

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Thank you. I read every single comment.