Several cyclists injured in another black ice incident



B

Bronzie

Guest
As this happened about 5 years ago, I'm pretty sure I've disposed of
the damaged helmet, but if not I'll have a closer look and let you know.
 
M

MartinM

Guest
Mark Thompson wrote:
> > was. It seems reasonable enough to me that if the impact was
> > sufficient to split my helmet, my head would have been far more likely
> > to have been injured if the helmet hadn't already absorbed some of the
> > impact.

>
> The split shows that it didn't absorb a lot of energy. They absorb it by
> compressing. When they fail they crack, absorbing almost no energy.


and you know this for a fact? The anti-helmet "facts" espoused by some
on this NG are often as incredulous as the pro ones espoused by the
manufacturers
 
S

sothach

Guest
MartinM wrote:
> Mark Thompson wrote:
> > > was. It seems reasonable enough to me that if the impact was
> > > sufficient to split my helmet, my head would have been far more likely
> > > to have been injured if the helmet hadn't already absorbed some of the
> > > impact.

> >
> > The split shows that it didn't absorb a lot of energy. They absorb it by
> > compressing. When they fail they crack, absorbing almost no energy.

>
> and you know this for a fact? The anti-helmet "facts" espoused by some
> on this NG are often as incredulous as the pro ones espoused by the
> manufacturers


If I remember that stuff about youngs modulus from college, I guess
they must absorb energy up until they crack, as it takes energy to
crack them.
 
R

Richard

Guest
MartinM wrote:
> Mark Thompson wrote:
>
>>>was. It seems reasonable enough to me that if the impact was
>>>sufficient to split my helmet, my head would have been far more likely
>>>to have been injured if the helmet hadn't already absorbed some of the
>>>impact.

>>
>>The split shows that it didn't absorb a lot of energy. They absorb it by
>>compressing. When they fail they crack, absorbing almost no energy.

>
>
> and you know this for a fact? The anti-helmet "facts" espoused by some
> on this NG are often as incredulous as the pro ones espoused by the
> manufacturers


I know it for a fact, yes. Go and look up the brittle failure strength
of expanded polystyrene. Compare it to the crushing deformation
strength. Also compare it to the strengths of bone. Look it up for
yourself, then you can't accuse me of espousing "facts". Come back and
let us know how you got on.

R.
 
I

Ian Smith

Guest
On Tue, 31 Jan 2006, Nick Murphy <[email protected]> wrote:
>
> Isn't it logical that if you have something on your head it will cushion the
> impact of your skull if it hits a a hard surface, however, miniimal that
> effect might be if you're going at speed.


Yes. It's equally logical that if you strap something to your head
and then your head hitrs a surface at anything more than an exactly
normal angle, it will wrench the neck and shake the brain more than
had you not been wearing something.

It's equally logical that if people have belief that their protective
equipment will mitigate injury severity, they will have more accidents
than if tehy were not wearing it.

> A couple of years ago I came off my bike and my head hit the road. I know
> that if I hadn't been wearing a helmet it would have been my skull which
> took the impact.


Possibly. But that's all you know. You don't, for example, know
that your injuries would have been any different. Most especially,
you don't know that you'd have had suvstantially the same accident had
you not been wearing a helmet. Personally, I'd rather my bare head
didn't hit the road than my head hit the road inside a helmet.

> Wearing a helmet doesn't make me feel invincible or less wary of stupid
> drivers - it's just a sensible precaution which stacks the odds slightly in
> your favour if the wrost happens.


No, if you look at the 'odds', all the real-world figures show that
while most people _think_ they can't hurt, they do in fact increase
the chance of you suffering an injury requiring hospital treatment
(though this may of course be a secondary effect rather than a direct
cause-effect situation), and do not in fact reduce the chance of you
suffering a life-changing injury.

But don't let facts impede your common sense.

regards, Ian SMith
--
|\ /| no .sig
|o o|
|/ \|
 
I

Ian Smith

Guest
On Tue, 31 Jan 2006, Richard <> wrote:
> John B wrote:
>
> > I suggest you wear a helmet when out walking.

>
> And driving - pedestrians and car occupants are at more risk of head
> injuries than cyclists.


And don't even think of getting into a shower bare-headed.

regards, Ian SMith
--
|\ /| no .sig
|o o|
|/ \|
 
J

James Annan

Guest
MartinM wrote:

> Mark Thompson wrote:
>
>>>was. It seems reasonable enough to me that if the impact was
>>>sufficient to split my helmet, my head would have been far more likely
>>>to have been injured if the helmet hadn't already absorbed some of the
>>>impact.

>>
>>The split shows that it didn't absorb a lot of energy. They absorb it by
>>compressing. When they fail they crack, absorbing almost no energy.

>
>
> and you know this for a fact?


Yes, it's elementary materials science, and common sense to boot. I
dropped a helmet onto a hard surface once (from about 3 feet) and a part
actually cracked off. Crushing it is a very different business. Try it
next time you have some polystyrene packaging.

I once did crush a helmet with a faceplant when a motorbike t-boned me,
effectively knocking the bicycle out from under me. I was still
concussed despite the helmet. I reckon it certainly reduced the facial
injuries and probably saved me from a broken nose. However, I doubt very
much whether I would have died from such a fall, and by sticking out, it
seems possible that the helmet actually increased the impact on my forehead

James
--
James Annan
see web pages for email
http://www.ne.jp/asahi/julesandjames/home/
http://julesandjames.blogspot.com/
 
M

Mark Thompson

Guest
> and you know this for a fact? The anti-helmet "facts" espoused by some
> on this NG are often as incredulous as the pro ones espoused by the
> manufacturers


Yes. Are you implying that my statement was false, anti-helmet
'propaganda'? No, of course not. The statement was true and neither
'pro' not 'anti' helmet.

<http://www.cyclehelmets.org/mf.html?1019> deals simply with the subject.
Further googling may reveal pages with actual figures on the energies
involved.
 
I

Ian Smith

Guest
On 31 Jan 2006 05:20:01 -0800, sothach <[email protected]> wrote:
>
> MartinM wrote:
> > Mark Thompson wrote:
> > > > was. It seems reasonable enough to me that if the impact was
> > > > sufficient to split my helmet, my head would have been far more likely
> > > > to have been injured if the helmet hadn't already absorbed some of the
> > > > impact.
> > >
> > > The split shows that it didn't absorb a lot of energy. They absorb it by
> > > compressing. When they fail they crack, absorbing almost no energy.

> >
> > and you know this for a fact? The anti-helmet "facts" espoused by some
> > on this NG are often as incredulous as the pro ones espoused by the
> > manufacturers

>
> If I remember that stuff about youngs modulus from college, I guess
> they must absorb energy up until they crack, as it takes energy to
> crack them.


Exactly, and the energy implied by reference to 'youngs modulus' is
tiny. Elastic deformation (ie, that relevant to young's modulus) and
brittle fracture (ie, that implied by 'crack') both absorb very little
energy, compared to plastic deformation (ie, that implied by 'crush').

This is why cars have 'crumple zones' rather than 'shatter zones' or
'springy zones'. It's why even if you mount your car bumpers on nice
elastomers they take only the lightest of parking knocks against
bollards, and if you actually want to dissipate the sorts of energy
that bodies colliding generate, you need large areas of material
undergoing large plastic deformations.

A helmet that has simply cracked (without crushing) will not have
absorbed much energy. Of course, it may have crushed before it
cracked, but if it was a simple clean crack, not much energy was
dissipated.

regards, Ian SMith
--
|\ /| no .sig
|o o|
|/ \|
 
M

MartinM

Guest
Mark Thompson wrote:
> > and you know this for a fact? The anti-helmet "facts" espoused by some
> > on this NG are often as incredulous as the pro ones espoused by the
> > manufacturers

>
> Yes. Are you implying that my statement was false, anti-helmet
> 'propaganda'? No, of course not. The statement was true and neither
> 'pro' not 'anti' helmet.


no I was questioning whether a polystyrene cycle helmet (covered in
what ever meringue etc they cover them in) absorbs no energy unless it
compresses.

> <http://www.cyclehelmets.org/mf.html?1019>


read it countless times; I don't consider it impartial.
 
M

Mark Thompson

Guest
> no I was questioning whether a polystyrene cycle helmet (covered in
> what ever meringue etc they cover them in) absorbs no energy unless it
> compresses.


Ah. There's the problem. No one has claimed that.
 
M

MartinM

Guest
Mark Thompson wrote:

> > no I was questioning whether a polystyrene cycle helmet (covered in
> > what ever meringue etc they cover them in) absorbs no energy unless it
> > compresses.

>
> Ah. There's the problem. No one has claimed that.


Helmets do a variety of things depending on the accident; from scraping
along the ground to shattering to compressing a bit to causing
increased rotation (and that doesn't include any external effect they
may have on other road users or even their wearers). The figures for
the effectiveness or disadvantage of each situation are not
sufficiently large IMO to make many claims either way. Compare this to
seatbelts where presumably they had a large amount of data before and
after they were fitted and also a fairly standard scenario in which
they were effective (I assume).
 
R

Richard

Guest
MartinM wrote:

>><http://www.cyclehelmets.org/mf.html?1019>

>
>
> read it countless times; I don't consider it impartial.


Why not? Are you suggesting that the authors are selective as to what
papers they discuss? Are you suggesting that the authors are selective
as to how they discuss the papers?

R.
 
D

davek

Guest
Nick Murphy wrote:
> What is it with some of you lot and your antipathy to helmets?


Well, for a start, antipathy is not the word you are looking for.

And for another thing, there was nothing you could construe from my
remarks that would position me as either pro or anti helmets - not
helmets themselves, at least, though you may construe what you like
about my feelings towards anecdotes of the "my helmet saved my life"
variety.

> Isn't it logical...


Shtop!

No, it isn't.

d.
 
D

davek

Guest
Ian Smith wrote:
> And don't even think of getting into a shower bare-headed.


Personally, I daren't risk even getting out of bed until I have my full
body armour on.

But then the other day I got the duvet tangled in my
getting-out-of-bed-helmet strap and nearly suffocated.

d.
 
M

MartinM

Guest
Richard wrote:
> MartinM wrote:
>
> >><http://www.cyclehelmets.org/mf.html?1019>

> >
> >
> > read it countless times; I don't consider it impartial.

>
> Why not? Are you suggesting that the authors are selective as to what
> papers they discuss? Are you suggesting that the authors are selective
> as to how they discuss the papers?


no, just that it is written IMO from an anti-compulsion stance so does
tend to favour the arguments which show the effectiveness of helmets in
a less than positive light.

Although TBF which organisations out there are impartial on the
subject? one would hope the doctors treating the injuries but this does
not seem to be the case either.
 
M

Mark Thompson

Guest
>> > no I was questioning whether a polystyrene cycle helmet (covered in
>> > what ever meringue etc they cover them in) absorbs no energy unless it
>> > compresses.

>>
>> Ah. There's the problem. No one has claimed that.

>
> Helmets do a variety of things depending on the accident; from scraping
> along the ground to shattering to compressing a bit to causing
> increased rotation (and that doesn't include any external effect they
> may have on other road users or even their wearers). The figures for
> the effectiveness or disadvantage of each situation are not
> sufficiently large IMO to make many claims either way. Compare this to
> seatbelts where presumably they had a large amount of data before and
> after they were fitted and also a fairly standard scenario in which
> they were effective (I assume).


<confused> I think you just replied to the wrong post.
 
M

MartinM

Guest
Mark Thompson wrote:

> >> > no I was questioning whether a polystyrene cycle helmet (covered in
> >> > what ever meringue etc they cover them in) absorbs no energy unless it
> >> > compresses.
> >>
> >> Ah. There's the problem. No one has claimed that.

> >
> > Helmets do a variety of things depending on the accident; from scraping
> > along the ground to shattering to compressing a bit to causing
> > increased rotation (and that doesn't include any external effect they
> > may have on other road users or even their wearers). The figures for
> > the effectiveness or disadvantage of each situation are not
> > sufficiently large IMO to make many claims either way. Compare this to
> > seatbelts where presumably they had a large amount of data before and
> > after they were fitted and also a fairly standard scenario in which
> > they were effective (I assume).

>
> <confused> I think you just replied to the wrong post.


Yes I hit my head once while wearing a helmet ;-)
 
R

Richard

Guest
MartinM wrote:
> Richard wrote:
>
>>MartinM wrote:
>>
>>
>>>><http://www.cyclehelmets.org/mf.html?1019>
>>>
>>>
>>>read it countless times; I don't consider it impartial.

>>
>>Why not? Are you suggesting that the authors are selective as to what
>>papers they discuss? Are you suggesting that the authors are selective
>>as to how they discuss the papers?

>
>
> no, just that it is written IMO from an anti-compulsion stance so does
> tend to favour the arguments which show the effectiveness of helmets in
> a less than positive light.


So, again, how do they "favour" these arguments? Concrete examples,
please.

R.
 
S

Simon Brooke

Guest
in message <[email protected]>,
MartinM ('[email protected]') wrote:

>
> Mark Thompson wrote:
>> > was. It seems reasonable enough to me that if the impact was
>> > sufficient to split my helmet, my head would have been far more
>> > likely to have been injured if the helmet hadn't already absorbed
>> > some of the impact.

>>
>> The split shows that it didn't absorb a lot of energy. They absorb it
>> by
>> compressing. When they fail they crack, absorbing almost no energy.

>
> and you know this for a fact? The anti-helmet "facts" espoused by some
> on this NG are often as incredulous as the pro ones espoused by the
> manufacturers


That polystyrene splitting absorbs little energy /is/ a fact and one that
you can verify easily at home. Take a piece of 1.5cm polystyrene sheet,
snap it; note the energy you had to expend to do it. It's very, very
small. Of course the fact that a helmet splits does not prove it did not
crush first.

--
[email protected]asmine.org.uk (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; If you're doing this for fun, do what seems fun. If you're
;; doing it for money, stop now.
;; Rainer Deyke
 

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