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Originally Posted by merider1
(Post 6262744)
Yet, YOU'VE been a major contributor. Therefore, based on your post, one can only incur damage by reading this thread unless they read your posts/views only? :rolleyes:
Major contributor? Nah. I just put in the old geezer point of view who rides in a third world nation which has more rock / gravel roads than pavement... I am sure that point view is very much under represented. |
Originally Posted by GlassWolf
(Post 6260584)
for what it's worth, a foam helmet is designed to split that way as it absorbs the energy of the impact. It did it's job as designed. This is similar to a crumple zone on a newer car. Once it's dropped or wrecked, you replace it.
It would seem to me that a split won't absorb much impact - crushing an inch of foam might give a little. http://en.wikipedia.org/wiki/Bicycle...3B_new_designs Design intentions and standards There are two main types of helmet: hard shell and soft/micro shell (no-shell helmets are now rare). Both are intended to reduce acceleration to the head due to impact, as a stiff expanded polystyrene liner is crushed.[5][6] Standards involve the use of an instrumented headform which is dropped, wearing a helmet, onto various anvils. The speed of impact is designed to simulate the effect of a rider's head falling from approximately usual riding height, without rotational energy and without impact from another vehicle.[7][8] Collision energy varies with the square of impact speed; a typical helmet is designed to absorb the energy of a head falling from a bicycle, an impact speed of around 12mph or 20 km/h. This will only reduce the energy of a 30 mph or 50 km/h impact to the equivalent of 27.5 mph or 45 km/h, and even this will be compromised if the helmet fails. As a subsidiary effect they should also spread point impacts over a wider area of the skull. Hard shell helmets may do this better, but are heavier and less well ventilated. They are more common among stunt riders than road riders or mountain bikers. Additionally, the helmet should reduce superficial injuries to the scalp. Hard shell helmets may also reduce the likelihood of penetrating impacts although these are very rare. [edit] Criticism of current standards; new designs Helmet liners may be too stiff to be effective. Some standards require the use of headforms heavier and more rigid than the human head; these are more capable of crushing foam than is the human head. [9] [10] In real accidents "very little crushing of the liner foam was usually evident... What in fact happens in a real crash impact is that the human head deforms elastically on impact. The standard impact attenuation test making use of a solid headform does not consider the effect of human head deformation with the result that all acceleration attenuation occurs in compression of the liner. Since the solid headform is more capable of crushing helmet padding, manufacturers have had to provide relatively stiff foam in the helmet so that it would pass the impact attenuation test... As the results in Figure 15 illustrate, the child skull is far from being solid and will deform readily on impact. This fact is well known in the medical field and is largely why a child who has had a rather modest impact to the head is usually admitted to hospital for observation. The substantial elastic deformation of the child head that can occur during impact can result in quite extensive diffuse brain damage."[11] In real accidents, while broken helmets are common, it is extremely unusual to see any helmet that has compressed foam and thus may have performed as intended. “Another source of field experience is our experience with damaged helmets returned to customer service... I collected damaged infant/toddler helmets for several months in 1995. Not only did I not see bottomed out helmets, I didn’t see any helmet showing signs of crushing on the inside.” [12] A new design of liner, the "cone-head", now being manufactured for motorcycle helmets but not yet available for bicycle helmets, has been designed in response to the 1987 study. It may provide better impact absorption.[13] Most helmets provide no protection against rotational injury and may make it worse. "The major discovery is that the skull plays an important role in protecting against rotational acceleration," says Phillips. He says almost all head injuries involve not just a direct blow to the skull but also damage to blood vessels caused by the brain rotating within the skull. In mechanical terms, the head is an elliptical spheroid with a single universal joint, the neck. It is therefore almost impossible to hit it without causing it to rotate. The head tries to dampen these forces using a combination of built-in defences: the scalp, the hard skull and the cerebrospinal fluid beneath it. During an impact, the scalp acts as rotational shock absorber by both compressing and sliding over the skull. This absorbs energy from the impact." [14] The Phillips head protection system, also only available in motorbike helmets at present, is designed to reduce rotational injury.[15] [edit] Proper fit It is important that a helmet should fit the cyclist properly – according to research most helmets (well over 90 % [16]) have been found to be incorrectly fitted. Efficacy of incorrectly fitted helmets is reckoned to be much lower; one estimate states that risk is increased almost twofold[17]. Most manufacturers provide a range of sizes ranging from children's to adult with additional variations from small to medium to large. The correct size is important. Some adjustment can usually be made using different thickness foam pads. Helmets are held on the head with nylon straps, which must be adjusted to fit the individual. This can be difficult to achieve, depending on the design. Most helmets will have multiple adjustment points on the strap to allow both strap and helmet to be correctly positioned. Additionally, some helmets have adjustable cradles which fit the helmet to the occipital region of the skull. These provide no protection, only fit, so helmets with this type of adjustment are unsuitable for roller skating, stunts, skateboarding and unicycling. The helmet should sit level on the cyclists head with only a couple of finger-widths between eyebrow and the helmet brim. The strap should sit at the back of the lower jaw, against the throat, and be sufficiently tight that the helmet does not move on the head. It should not be possible to insert more than one finger's thickness between the strap and the throat. [edit] |
Now - let's focus on the standard (this finally penatrated my thick skull)
Collision energy varies with the square of impact speed; a typical helmet is designed to absorb the energy of a head falling from a bicycle, an impact speed of around 12mph or 20 km/h. How about a test of 12 MPH with a 100 lb body behind it? Think you will get a different result? Also, for those of you who are so sure that a helmet saved your life - please get a new helmet and compare you old one - how much did the foam compress? If it didn't compress all the way - it didn't do much, now did it? Another part of above "very little crushing of the liner foam was usually evident... What in fact happens in a real crash impact is that the human head deforms elastically on impact. The standard impact attenuation test making use of a solid headform does not consider the effect of human head deformation with the result that all acceleration attenuation occurs in compression of the liner. Since the solid headform is more capable of crushing helmet padding, manufacturers have had to provide relatively stiff foam in the helmet so that it would pass the impact attenuation test... As the results in Figure 15 illustrate, the child skull is far from being solid and will deform readily on impact. This fact is well known in the medical field and is largely why a child who has had a rather modest impact to the head is usually admitted to hospital for observation. The substantial elastic deformation of the child head that can occur during impact can result in quite extensive diffuse brain damage. My opinion of helmet - wear it if you want - but don't think it cures the real problem - which is how you are treated in traffic. When I am in traffic, everyone waits, no honking, no swearing, and no getting too close. I am a LOT safer than you with your little piece of foam. Ranting about helmets isn't doing a thing - lobby for safe riding in the streets. Man, I have given myself a head ache - where is my helmet? :rolleyes: |
Ah - just read this: Same source
Anecdotal evidence A common misunderstanding is to assume that a broken helmet has prevented some serious injury. "the main impact was to my head. So much so, that my helmet broke in two (as it is designed to do). Without the helmet, it would have been my head that was broken and I wouldn’t be writing this blog entry! I’d be dead..."[47] Helmets are designed to crush without breaking; expanded polystyrene absorbs little energy in brittle failure and once it fails no further energy is absorbed. To prevent overt fragmentation, the foam in most helmets is reinforced inside with plastic netting to keep the foam together. |
Originally Posted by merider1
(Post 6262722)
They offer "some" protection and isn't that enough? (I don't agree that it offered no protection at all - too many examples of how that isnt true in so many instances) And why isn't "enough" something that should end the agrument?
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Originally Posted by rruff
(Post 6262840)
Then please tell me what is unreliable about the data, or at least provide some of your own that tells a different story.
Please go here and read the statistics, research, testimonials, etc. all over again, since you obviously didn't do so before: http://www.bhsi.org/subjects.htm |
modern helmets, yes. The foam helmets I speak of are from 20 years ago, when you could still buy one. I don't think they even make soft shell helmets anymore. The one I (still) have, is reinforced only by the cloth net over the outside of it, to hold it together. That being said, any sharp object impacting the foam will tend to both compress the foam, and split it like a wood splitter.
You do realize it's not a "one of the other" thing. you can compress foam, and still have the shell break. Both of these are absorbing some of the impact energy. Yes stop wearing helmets and just advocate safer roads. While you're at it, should you fight for driving without a seatbelt because it's better to fight for safer roads? Why not advocate safer riding and wear safety gear? |
Originally Posted by crtreedude
(Post 6263132)
Also, for those of you who are so sure that a helmet saved your life - please get a new helmet and compare you old one - how much did the foam compress? If it didn't compress all the way - it didn't do much, now did it? My opinion of helmet - wear it if you want - but don't think it cures the real problem - which is how you are treated in traffic. When I am in traffic, everyone waits, no honking, no swearing, and no getting too close. I am a LOT safer than you with your little piece of foam. : As for compression, the helmet is completely dented (is that what you mean?), and the foam cracked. It is now useless, but it was excellent for protection at the moment I hit the ground. Last but not least, I wish those of you talking in hyperbole about how helmets don't prevent death in all instances or are not the "cure" - no one has said they do or that they are. I'm about to pull my hair out that this is just ignored. No one has said that helmets prevent death and/or injury in all cases of a catastrophic cycling accident in which the head suffers trauma upon impact. No one has said that helmets will cure all accidents and stop riders from ever going down. They are stictly meant to help protect in the case of an accident. Sheesh! Why don't we start a thread on wrist guards? :rolleyes: |
Apparently anecdotal evidence is only valid when it supports the potential danger of wearing helmets.
As merider noted earlier, helmets can lessen the chance of injury in certain situations. I didn't say prevent fatalities, I said lessen the chance of injury. Having been through one of those situations, I'll continue to wear a helmet. I suppose I should ignore direct experience in favor of statistics, but I won't. In fact I just bought a new helmet yesterday. I did note that the manual indicates not to wear it while climbing trees. That sounds like sound advice. |
Originally Posted by merider1
(Post 6263584)
I'm positive that my helmet protected my head and may have saved my life when I crashed. I hate the word anecdotal in these discussions, because that implies that those of us who have actually crashed and are giving an account of what happened are "telling a story." We aren't. We are giving facts. My head did hit the ground. My helmet was cracked all the way through with a pebble embedded in it. I had horrible headaches for over two days following. I'm not as dumb as barnyard chicken to think that the helmet I was wearing properly at the time of impact did me no good, didn't do it's job, didn't protect my head or may have caused more damage than good.
Good to hear you were wearing a helmet so you can be here to argue this with everyone ;). I'm with you, but it's still just an anecdote. Now, if everyone involved put together their experiences and we compiled them into a statistic we'd have a much more useful piece of evidence. Especially since this group would be representative of the group known as "hardcore riders" "real cyclists" or "those people who actually wear their bikes out." I have a feeling it would look something like this: 80% -- Never needed the helmet in a crash. 10% -- It saved my life!! Okay, it probably didn't but it might have saved me from a concussion. 10% -- Undecided. Then you'd hear complaints about how the dead aren't represented by the poll and it'd be thrown out as useless. |
I want to focus on the issue of helmet design.
The helmet needs to do several things, among others: a) Provide best deceleration possible b) Dissipate energy c) Prevent twisting/sudden rotation of the head I don't think modern helmets, while certainly providing protection over wearing nothing, do a good job of any of the above. Appear to be more fashion that function. My thoughts (even though this would initially be the most uncool looking helmet :) ) : a) Provide best deceleration possible - what is needed is a couple of inches at minimum of thickness with 2 layers of compressible foam, the inner one being much softer. My helmet hardly compressed from my last crash. b) Dissipate energy - shatter by design, much as movie glass is safety/precut to split into a hundred pieces. My helmet cracked oddly in 3 pieces. I would have liked to see 8-10 pieces really fly away as in race cars. c) Prevent twisting/sudden rotation of the head. Round should be much better than the pointed ones we use, that often end in a point at the back. Recently manufacturers are correcting this. Plus shiny motorcycle helmet like surface with fewer large vents (lots of smaller holes instead) would help to prevent snagging on something to snap the neck/twist the head. One could still retain sufficient holes for cooling. |
My problem with helmets is simple:
1. Many of those who wear helmets think that the wearing of helmets helps a lot - no statistical evidence for this - result, no one pushes for better helmets or better conditions on the road. The law makers think - "hey, we will cure this problem of deaths on the road - everyone wear a helmet!" - which will do absolutely nothing to deal with the real problem. 2. Many people assume because people say to not wear a helmet is stupid, foolish, etc. that riding a bike is more dangerous than walking. Statistically, it isn't. (this is a fact) - result, less people ride bikes which results in lack of excercise and much more people dying early. 3. It make me look uglier (not really, I think I maxed out on ugly sometime ago) 4. So far - the same arguments that people use for wearing a helmet (i.e. it is better than nothing) can be used with an equally dangerous activity - walking. I appreciate that some of you have had near death experiences that you feel a helmet prevented - cool, and there are many people who are dead that if they wore a helmet WHILE WALKING would still be alive. That doesn't mean we all go around telling people who don't wear a helmet while walking that they are talking unnecessary risks and mandate that all children wear helmets while walking. If older people want to walking around with helmets on their heads (I am thinking people who are 70) it really wouldn't be a bad idea and it surely would save a lot of lives. I kid you not. But - there is no one making a big point of this. |
Originally Posted by crtreedude
(Post 6263999)
....If older people want to walking around with helmets on their heads (I am thinking people who are 70) it really wouldn't be a bad idea and it surely would save a lot of lives. I kid you not. But - there is no one making a big point of this.
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Originally Posted by crtreedude
(Post 6263132)
"very little crushing of the liner foam was usually evident... What in fact happens in a real crash impact is that the human head deforms elastically on impact. The standard impact attenuation test making use of a solid headform does not consider the effect of human head deformation with the result that all acceleration attenuation occurs in compression of the liner. Since the solid headform is more capable of crushing helmet padding, manufacturers have had to provide relatively stiff foam in the helmet so that it would pass the impact attenuation test... As the results in Figure 15 illustrate, the child skull is far from being solid and will deform readily on impact. This fact is well known in the medical field and is largely why a child who has had a rather modest impact to the head is usually admitted to hospital for observation. The substantial elastic deformation of the child head that can occur during impact can result in quite extensive diffuse brain damage."
Ranting about helmets isn't doing a thing - lobby for safe riding in the streets. |
Originally Posted by rufvelo
(Post 6263805)
I want to focus on the issue of helmet design.
The helmet needs to do several things, among others: a) Provide best deceleration possible b) Dissipate energy c) Prevent twisting/sudden rotation of the head I don't think modern helmets, while certainly providing protection over wearing nothing, do a good job of any of the above. Appear to be more fashion that function. My thoughts (even though this would initially be the most uncool looking helmet :) ) : a) Provide best deceleration possible - what is needed is a couple of inches at minimum of thickness with 2 layers of compressible foam, the inner one being much softer. My helmet hardly compressed from my last crash. b) Dissipate energy - shatter by design, much as movie glass is safety/precut to split into a hundred pieces. My helmet cracked oddly in 3 pieces. I would have liked to see 8-10 pieces really fly away as in race cars. c) Prevent twisting/sudden rotation of the head. Round should be much better than the pointed ones we use, that often end in a point at the back. Recently manufacturers are correcting this. Plus shiny motorcycle helmet like surface with fewer large vents (lots of smaller holes instead) would help to prevent snagging on something to snap the neck/twist the head. One could still retain sufficient holes for cooling. b.) Pieces flying away are a sign of failure to dissipate energy. Crushing is a sign of success here. When those pieces fly away they dissipate the very small amount of energy it takes to accelerate their small amount of mass. If you want to get energy dissipation from a small amount of mass (and it has to be a small amount of mass for ergonomic reasons) then you need things like compression where the structure is broken down in such a way that as much of the helmet as possible absorbs impact. Styrofoam does a really good job of this already, especially for its density and price. Also, I'd like to point out a and b are really the same thing. The purpose of absorbing the energy in the helmet is to decrease the acceleration of the head. c.) My helmet is round. The glued on visor (which I hope will just break away) has corners and the back has some soft corners. I wouldn't buy an aero helmet unless I were trying to break the hour record. I think this is an area that could be improved though. I'd like to see the shell made of a material which rips away fairly easily. The plastic won't slide on the cement and I think it needs to. Something that functions how the scalp functions when it slides. I'd add a (d) to my perfect helmet: Cost. If the helmet can't be sold for $30-$40 it's too expensive. It'll only appeal to good riders and Fred's, not to the people we want to convince to ride their bikes more often. It'd just be a bigger barrier to entry. Which the helmet may already be too big of a barrier to entry for some people. |
Originally Posted by rruff
(Post 6264349)
I agree that the test that helmets are designed to pass is pretty bogus in the real world. For some reason almost every person who crashes *cracks* their helmet while compressing the foam very little, while the solid headform in the test compresses the foam instead. I think cycling helmets would be much more effective at mitigating minor injuries if the foam were a softer material.
Yup... that is the thing that would really help. Inside foam is the standard foam used now. Outside foam is about 1cm thick. Something similar to memory foam, but a bit harder. Attached to the outside foam are 1cm hexagonal plastic plates no thicker than scotch tape. Their main purpose is to add color and make the helmet easier to deal with and keep some moisture out of the memory foam. The idea being that the small plastic bits would rip off with the memory foam fairly easily (increasing helmet care) so that when they slide on the pavement it reduces the torsional forces. |
Originally Posted by merider1
(Post 6263544)
I really don't need to. Links have already been provided in here by other members to the the BHSI, that you just scoffed at.
BHSI has a lot of info, and some of it is even interesting. Here is one of the interesting bits: "Motor vehicles are involved in 90-92 per cent of bicyclist deaths." Now I understand a major reason why professional cycle racing (without helmets) was safer per mile than riding a bike in the US, even though they crash a lot more often. As I read through the articles and reports on the BHSI site, I'm not seeing any credible evidence that shows helmets being effective. If you or anyone else is interested, please point out the ones that do. They seem to be in the nature of "cyclists who crash often get head injuries, helmets prevent head injuries (no data, taken on faith), and so wearing helmets would prevent a sizeable number of head injuries." Or, they do a survey of hospital admissions were they discover that the riders admitted who were wearing helmets when they crashed, had less severe head injuries than those who weren't wearing helmets. But they fail to point out that helmeted cyclists who are admitted are over-represented in the cycling population... so either helmeted cyclists crash more often, or they are more likely to go to the hospital when they do. I've never seen a pro-helmet article that attempts to explain why cycling injuries and fatalities do *not* go down when helmet use increases. IMO this is the definitive data because it covers the whole population, so extenuating variables are minimized. |
Originally Posted by merider1
(Post 6263584)
I'm positive that my helmet protected my head and may have saved my life when I crashed.
The fragileness of our heads is greatly over-emphasized, as well as the effectiveness of cycling helmets to do any good at all. |
Originally Posted by crhilton
(Post 6264673)
a.) b.) Pieces flying away are a sign of failure to dissipate energy.
Also, walking isn't as dangerous as cycling. People don't walk around the house at 50MPH. "One man's bike wreck is a tragedy. A thousand bike wrecks, a statistic." -Joseph Stalin |
Originally Posted by GlassWolf
(Post 6264760)
Have any experience with "reactive armor plating?"
Also, walking isn't as dangerous as cycling. People don't walk around the house at 50MPH. What did I say about walking? And please keep your bike below 40mph, your family loves you ;). |
reactive armor is actually designed to explode upon impact from a projectile, essentially negating most if not all of the energy of impact. It's used on tanks and medium armor vehicles like APCs these days.. neat stuff.
I do agree that helmets would do a lot of good on older folks suffering from diseases like alzheimers or senility, as they often join the bed-diving olympics, as reported statistically by my mother the RN. haha Much the same way some mentally challenged people wear a helmet to prevent damage from banging their head against a wall.. ..now if I could just figure out how to work the strap on this silly helmet. |
Originally Posted by hyperneck
(Post 6264244)
This topic is not even debatable in the “Fifty Plus” forum. We already know our brains have shrunk to half their original size, leaving more space for the brain to travel inside the skull.
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Originally Posted by GlassWolf
(Post 6264760)
Have any experience with "reactive armor plating?"
Also, walking isn't as dangerous as cycling. People don't walk around the house at 50MPH. "One man's bike wreck is a tragedy. A thousand bike wrecks, a statistic." -Joseph Stalin If you hit a metal post full on with the fanciest bike helmet on the market - you are dead. Review the testing procedures of helmets. The weight of a head (free of body) dropped from 2 meters to stimulate a HEAD (not body) falling at a speed of 12 MPH. What a joke. Statistically - walking is as dangerous as cycling. This is a fact. One issue as well is that with speed - a bike becomes very stable - unless me walking which is closer to a control fall. |
Originally Posted by rruff
(Post 6264693)
But they fail to point out that helmeted cyclists who are admitted are over-represented in the cycling population... so either helmeted cyclists crash more often, or they are more likely to go to the hospital when they do.
Also keep in mind that going to a hospital is a choice, unless one is incapacitated, in which case someone else makes the decision for the person in question. So this "statistic" could also indicate that those of the "my head can beat up rocks!!" mentality have sufficient machismo to not bother getting themselves checked out at those wimpy hospitals.
Originally Posted by rruff
(Post 6264693)
the fragileness of our heads is greatly over-emphasized
Using the logic prevalent in the "bike helmets do nothing" camp, police should abandon kevlar vests in favour of cheaper and cooler cotton T-shirts, because neither will protect them from panzershreks, and APC drivers should ditch the reactive armour and drive school buses because neither will protect them from nuclear warheads. |
Originally Posted by crtreedude
(Post 6264976)
Statistically - walking is as dangerous as cycling. This is a fact. One issue as well is that with speed - a bike becomes very stable - unless me walking which is closer to a control fall.
mass*acceleration. |
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