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PostPosted: Sat Jun 29, 2013 1:58 pm 
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Then working definition used by the HSE...

Hazard - something which can cause an adverse affect.

Risk - the likelihood that a hazard will cause that adverse affect, together with a measure of the effect.

So Graham enjoying his sunny day bimble on the river bank may be less hazardous, but should a pretty lady/flasher/duck distract him and he falls then the risk is the same.

It's very dull, so probably best read it for yourself, but it can be seen that the phenomenon of probability Graham was referring to is indeed likelihood, not risk.

http://www.hse.gov.uk/risk/theory/alarpglance.htm


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PostPosted: Sat Jun 29, 2013 2:07 pm 
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There are arguments for and against just about everything nowadays.

At the end of the day you have to make your own decisions, and no amount of derision or inflated claims to definitive answers will change that.

I remember the seat belt compulsion like it was yesterday, and all the arguments against it.

The real facts on helmet wearing may only reveal themselves over time.

It is a subject that has been done to death on every forum.

Concerning motorbikes, and the varying laws across the world and particularly between US states, there is still some debate about compulsion but very few arguments are based on efficacy.


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PostPosted: Sat Jun 29, 2013 2:24 pm 
retrobike rider
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The optimal solution in reducing brain injury may be to have helmet designs that are effective and proven and riders who do trust that the helmets to protect them much and as a consequence do not take unnecessary risks.

However it seems to me that at present we have the opposite. Riders who believe that their helmets are going to save them and helmet designs that may not even protect adequately against even low speed collisions.


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PostPosted: Sat Jun 29, 2013 2:48 pm 
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Downhill helmets are a whole different kettle of fish to what is normally worn, the answer might be to separate up the classifications of helmet when drawing conclusions.

Next they will be telling us body armour is ineffective.

I don't think the kind of rider who goes out and rides recklessly is going to be bothered much by their helmet or lack thereof.

Conversely I think the conscientious rider who buys a helmet and associated safety gear is more likely to be a safer rider generally, and unlikely to take more risks on the basis they are wearing a helmet. Unless it is suggested they might not venture out at all if they did not make that purchase, or consider it afforded some guarantee of protection.

At best a helmet is ameliorating risk, at worst it is causing risky behaviour.

I wonder which is most prevalent and has most influence on accident outcomes.


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PostPosted: Sat Jun 29, 2013 8:05 pm 
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You can actually buy helmets that are designed to reduce the likelihood of brain damage caused by angular or rotational acceleration.
http://www.youtube.com/watch?v=m8W5X0s2AhU

And others are being developed.
http://www.bicycling.com/sites/default/ ... Helmet.pdf


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PostPosted: Sat Jun 29, 2013 11:57 pm 
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GrahamJohnWallace wrote:
Here is a video showing a design of self-inflating helmet.
http://www.youtube.com/watch?v=Tn65Bows0Ws
The commentary uses the term " protecting the wearer", which implies that it will protect you entirely in all circumstances. However apart from being overwhelmed by high energy impacts. it also needs to deflate in order to absorb energy on impact, airbag style. This means that it is unlikely to be effective in accidents were the head is impacted more than once.



Air compresses. Tyres and air suspension don't deflate on impact. I was under the impression that vehicle air bags deflate after impact so as not to suffocate the user.


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PostPosted: Sun Jun 30, 2013 9:04 am 
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Definition of protect - AIM to preserve.

Any one who argues that helmets aren't necessary because they don't keep you safe under every circumstance, has rather missed the point and anyone who wears a helmet and believes they are immune to injury as a result, is an idiot.

I've bounced my head off a few rocks in my time and I'm quite sure that I'm such a good looking bloke now as a result of my helmet hitting the ground before my face on numerous occasions. Only last week, as I slid along the ground, listening to the noise of tree roots hitting my helmet before I came to a stop, was I thinking "this would hurt without a helmet". Of course then the realisation dawned that although the helmet had once again saved my good looks, I'd cut up my legs and knackered my shoulder. Maybe I should start wearing body armour and knee pads.


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PostPosted: Sun Jun 30, 2013 9:09 am 
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GrahamJohnWallace wrote:
You can actually buy helmets that are designed to reduce the likelihood of brain damage caused by angular or rotational acceleration.
http://www.youtube.com/watch?v=m8W5X0s2AhU

And others are being developed.
http://www.bicycling.com/sites/default/ ... Helmet.pdf

I've recently bought a POC. It's a nice lid, although I have the version without the big chunk missing out the top! ;)


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PostPosted: Sun Jun 30, 2013 9:51 am 
retrobike rider
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JamesM wrote:
GrahamJohnWallace wrote:
Here is a video showing a design of self-inflating helmet.
http://www.youtube.com/watch?v=Tn65Bows0Ws
The commentary uses the term " protecting the wearer", which implies that it will protect you entirely in all circumstances. However apart from being overwhelmed by high energy impacts. it also needs to deflate in order to absorb energy on impact, airbag style. This means that it is unlikely to be effective in accidents were the head is impacted more than once.



Air compresses. Tyres and air suspension don't deflate on impact. I was under the impression that vehicle air bags deflate after impact so as not to suffocate the user.

That's a good observation.
Tyres and suspension do not indeed deflate on impact, they absorb the impact and then release it back in the opposite direction. This is not desirable with a cycle helmet or an airbag as the rebound would double the total of the deceleration and acceleration forces experienced during the impact. The ideal is for the energy of the impact to be totally absorbed over the longest time period possible. The correctly performing foam lining of a cycle helmet should take about 6,000ths of a second to fully crush whilst a bare head will absorb the same energy in 1,000th of a second. If the foam lining has worked as intended then its will be totally crushed. Broken helmets or those where the lining is not crushed have in fact not performed as intended. An airbag has vent holes in it. It is the air traveling through these holes that actually absorbs the impact energy at a controlled rate.

http://en.wikipedia.org/wiki/Airbag
"Post-deployment"
"A chemical reaction produces a burst of nitrogen to inflate the bag. Once an airbag deploys, deflation begins immediately as the gas escapes through vent(s) in the fabric (or, as it's sometimes called, the cushion) and cools. Deployment is frequently accompanied by the release of dust-like particles, and gases in the vehicle's interior (called effluent). Most of this dust consists of cornstarch, french chalk, or talcum powder, which are used to lubricate the airbag during deployment."


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PostPosted: Wed Jul 03, 2013 9:21 pm 
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Two Cartoons from New Zealand


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yehudamoon3.jpg
yehudamoon3.jpg [ 36.75 KiB | Viewed 85 times ]
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