Helmet compulsion....

On Thu, 29 Apr 2004 20:52:51 +0100, "Russ"
<[email hidden]> wrote in message
<[email hidden]>:

Quoted message said:

the helmet was completely busted in two though so it
appears it may well have worked very well

Or not. Helmets are supposed to work by plastic deformation;
in brittle failure mode they absorb virtually no energy.

--
Guy
===
May contain traces of irony. Contents liable to settle after
posting. chapmancentral.co.ukchapmancentral.co.ukOpen ↗

88% of helmet statistics are made up, 65% of them at
Washington University

in message <[email hidden]>, Russ

(') said:

It's also one of the first questions I get asked by the
various members of my legal team - My head was pretty much
uninjured, unlike my back - the helmet was completely
busted in two though so it appears it may well have worked
very well

Nope.

A helmet that worked is crushed but not broken. A helmet
that's broken just failed and didn't do any good at all.
Helmets 'work' by plastic deformation (that is, the foam
crushes). This absorbs quite a lot of energy. If they break
they absorb little or no energy in the process.

--
[email hidden] (Simon Brooke)
jasmine.org.uk~simonOpen ↗

Morning had broken, and there was nothing we could
do but wait patiently for the RAC to arrive.

"Simon Brooke" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

in message <[email hidden]>,

Russ (') said:

It's also one of the first questions I get asked by the
various members of my legal team - My head was pretty
much uninjured, unlike my back - the helmet was
completely busted in two though so it appears it may
well have worked very well

Nope.

A helmet that worked is crushed but not broken. A helmet
that's broken just failed and didn't do any good at all.
Helmets 'work' by plastic deformation (that is, the foam
crushes). This absorbs quite a lot of energy. If they
break they absorb little or no energy in the process.

Just because it's broken doesn't necessarily mean that it
didn't work though. I don't have the helmet but knowing a
bit about how materials fail it's entirely possible (and
indeed likely) that it did in fact absorb a significant
amount of enery by plastic deformation prior to reaching the
limit of it's strength and splitting [1] and even after
splitting would continue to absorb energy while it was in
place (which it was). As I said the accident was well
outside the design parameters for the helmet (12mph) but to
claim it didn't work just because it split is just plain
stupid I'm afraid. The idea that I could hit the ground with
my head at that speed and not suffer serious head injuries
is just not an option (at the very least I'd have had
serious lacerations). I didn't though and therefore the
helmet must have done it's job. The helmet splitting is
merely an indication of the seriousness of the accident - of
course it failed (you'd expect that hitting the ground so
hard), but it will have failed after absorbing a significant
amount of energy just as it's designed to do.

It's all very well trying to claim helmets don't help in
some accidents but they do help where you come off the
bike and land directly on your head. I still don't
support compulsion and don't even insist my children wear
a helmet all the time but in a sports environment where
there's a significant chance of coming off they do help
protect the head.

Russ

[1] even concrete will split if you crush it hard enough -
that's how materials fail in compression

On Fri, 30 Apr 2004 10:15:04 +0100 someone who may be "Russ"
<[email hidden]> wrote this:-

Quoted message said:

knowing a bit about how materials fail it's entirely
possible (and indeed likely) that it did in fact absorb a
significant amount of enery by plastic deformation prior to
reaching the limit of it's strength and splitting

It will have absorbed some energy. I doubt if this was
significant though.

Quoted message said:

and even after splitting would continue to absorb energy
while it was in place (which it was).

It may have absorbed a small amount of energy.

Quoted message said:

(at the very least I'd have had serious lacerations).

Study of Google will indicate that everybody agrees that
helmets will prevent some cuts and grazes. However, these
are seldom serious or fatal.

--
David Hansen, Edinburgh | PGP email preferred-key number
F566DA0E I will always explain revoked keys, unless the UK
government prevents me using the RIP Act 2000.

"David Hansen" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

On Fri, 30 Apr 2004 10:15:04 +0100 someone who may be
"Russ" <[email hidden]> wrote this:-

Quoted message said:

knowing a bit about how materials fail it's entirely
possible (and indeed likely) that it did in fact absorb a
significant amount of enery by plastic deformation prior
to reaching the limit of it's strength and splitting

It will have absorbed some energy. I doubt if this was
significant though.

and your proposed mode of failure to support this is ? as
opposed to the one I've proposed above.

Quoted message said:

Quoted message said:

and even after splitting would continue to absorb energy
while it was in place (which it was).

It may have absorbed a small amount of energy.

So where did the rest go then - my head hit hard enough
that the force of my body following through seriously
broke two vertibrae and to completely destroyed the one
inbetween those but without damage to my head which was
what I landed on.

That's a fairly significant amount of energy absorbed by
the helmet to prevent injury to my head/skull in my book.
At the end of the day it did what it was designed to do
within the limited parameters of that design will have
absorbed the energy it was designed to absorb. It gave me a
significant level of protection, ie a level of protection
significantly higher than than would have existed had I not
been wearing it.

Russ

On Fri, 30 Apr 2004 16:48:14 +0100 someone who may be "Russ"
<[email hidden]> wrote this:-

Quoted message said:

Quoted message said:

Quoted message said:

knowing a bit about how materials fail it's entirely
possible (and indeed likely) that it did in fact absorb
a significant amount of enery by plastic deformation
prior to reaching the limit of it's strength and
splitting

It will have absorbed some energy. I doubt if this was
significant though.

and your proposed mode of failure to support this is ? as
opposed to the one I've proposed above.

I didn't question your mode of failure and neither did I
propose a different mode of failure.

What I did question is your assertion that this resulted in
a significant amount of energy being absorbed by the helmet.
By significant I assume you mean a significant proportion of
the total energy.

--
David Hansen, Edinburgh | PGP email preferred-key number
F566DA0E I will always explain revoked keys, unless the UK
government prevents me using the RIP Act 2000.

Russ <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Quoted message said:

It may have absorbed a small amount of energy.

So where did the rest go then - my head hit hard enough
that the force of

my

Quoted message said:

body following through seriously broke two vertibrae and
to completely destroyed the one inbetween those but
without damage to my head which was what I landed on.

Your skull is much more resistant to injury that your neck.
To injure the skull you need an impact with a point, or VERY
high crushing force. The injuries you describe are
completely consistent with any head-on impact, irrespective
of whether you were wearing a plastic hat.

Quoted message said:

That's a fairly significant amount of energy absorbed by
the helmet to prevent injury to my head/skull in my book.

Your book needs editing.

Quoted message said:

At the end of the day it did what it was designed to do
within the limited parameters of that design

will

Quoted message said:

have absorbed the energy it was designed to absorb. It
gave me a significant level of protection, ie a level of
protection significantly higher than than would have
existed had I not been wearing it.

A) it's not designed to prevent injury of any
significant degree
B) it didn't do what it was supposed to - it split rather
than be crushed, absorbing hardly any energry
C) if it had succeeded completely in its design it still
would have had no significant effect on your injury

You'd best go on to another thread; you're not going to
persuade anyone here of your view - we have all read the
statistics and you clearly haven't. Try asking about
greasing your tapers...

"jtaylor" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Russ <[email hidden]> wrote in
message "]news:[email hidden]...

Quoted message said:

Quoted message said:

It may have absorbed a small amount of energy.

So where did the rest go then - my head hit hard enough
that the force

of

Quoted message said:

my

Quoted message said:

body following through seriously broke two vertibrae and
to completely destroyed the one inbetween those but
without damage to my head which

was

Quoted message said:

Quoted message said:

what I landed on.

Your skull is much more resistant to injury that your
neck. To injure the skull you need an impact with a point,
or VERY high crushing force. The injuries you describe are
completely consistent with any head-on impact,
irrespective of whether you were wearing a plastic hat.

Well I've had concussion from hitting the ground playing
rugby so at the very least it should protect from that.

Quoted message said:

Quoted message said:

That's a fairly significant amount of energy absorbed
by the helmet to prevent injury to my head/skull in
my book.

Your book needs editing.

Quoted message said:

At the end of the day it did what it was designed to do
within the limited parameters of that design

will

Quoted message said:

have absorbed the energy it was designed to absorb. It
gave me a significant level of protection, ie a level of
protection significantly higher than than would have
existed had I not been wearing it.

A) it's not designed to prevent injury of any significant
degree

It's designed to protect the head from impact I believe -
thats certainly how they're tested.

Quoted message said:

B) it didn't do what it was supposed to - it split rather
than be crushed, absorbing hardly any energry

Did you read the thread at all and do you have any idea at
all about failure modes of materials ? - splitting is
entirely consistent with a material over stressed to failure
by crushing. Therefore it would have absorbed all the energy
it was designed to and then failed - it therefore did
exactly what it was supposed to do.

Quoted message said:

You'd best go on to another thread; you're not going to
persuade anyone

here

Quoted message said:

of your view - we have all read the statistics and you
clearly haven't.

Errm - that'll be the statistics that show that in non
traffic accidents where people hit their head on the ground
that the control group of non helmet wearers was not less
injured than the helmet wearers. - not

I'm well aware of (and understand very well) the statistics
of various studies of road users in areas of helmet
compulsion and while very revealing about helmet compulsion
the huge number of other factors make any extrapolation
about efficacy of helmet per se completely meaningless.

Quoted message said:

Try asking about greasing your tapers...

comments like this show what a [censored] you really are and
I wonder if it's even worth taking the time to answer
your post.

Russ

"David Hansen" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

On Fri, 30 Apr 2004 16:48:14 +0100 someone who may be
"Russ" <[email hidden]> wrote this:-

Quoted message said:

Quoted message said:

>knowing a bit about how materials fail it's entirely
>possible (and indeed likely) that it did in fact
>absorb

a

Quoted message said:

Quoted message said:

Quoted message said:

>significant amount of enery by plastic deformation
>prior to reaching

the

Quoted message said:

Quoted message said:

Quoted message said:

>limit of it's strength and splitting

It will have absorbed some energy. I doubt if this was
significant though.

and your proposed mode of failure to support this is ? as
opposed to the

one

Quoted message said:

Quoted message said:

I've proposed above.

I didn't question your mode of failure and neither did I
propose a different mode of failure.

What I did question is your assertion that this resulted
in a significant amount of energy being absorbed by the
helmet. By significant I assume you mean a significant
proportion of the total energy.

Not of the total accident no - but of the total energy that
would otherwise have had to be absorbed by my head that
could have caused concussion or other injury yes

Russ

in message <[email hidden]>, Russ

(') said:

"Simon Brooke" <[email hidden]> wrote in message news:1gd8m1-
[email hidden]...

Quoted message said:

in message <[email hidden]>,

Russ (') said:

It's also one of the first questions I get asked by the
various members of my legal team - My head was pretty
much uninjured, unlike my back - the helmet was
completely busted in two though so it appears it may
well have worked very well

A helmet that worked is crushed but not broken. A helmet
that's broken just failed and didn't do any good at all.
Helmets 'work' by plastic deformation (that is, the foam
crushes). This absorbs quite a lot of energy. If they
break they absorb little or no energy in the process.

Just because it's broken doesn't necessarily mean that it
didn't work though.

[snip]

That's possible, but the fact that it split isn't proof that
it worked.

Quoted message said:

The idea that I could hit the ground with my head at that
speed and not suffer serious head injuries is just not an
option (at the very least I'd have had serious
lacerations).

I hit the ground with my head at something probably over
eighty miles per hour in a car crash four years ago, with
the weight of the car (still rolling) on top of me[1]. They
cleaned mud and moss out of my hair in casualty. But the
only injury I sustained was a smashed and crushed fifth
thoracic vertebra; I didn't have even a scratch on my head,
although I did have slight concussion.

So, again, you can hit the ground with your head exceedingly
hard (hard enough to crush your backbone) without injuring
your head. Mind you, of course, that may be because where
there's no sense there's no feeling.

[1] It should be said here that when the car bounced in the
inverted position the rollover bar took most of the
impact - otherwise I doubt I'd be posting this. The
second time it inverted it was in the air and didn't
bounce until it was again right way up.

--
[email hidden] (Simon Brooke)
jasmine.org.uk~simonOpen ↗

"Simon Brooke" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

in message <[email hidden]>,

Russ (') said:

"Simon Brooke" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

in message <[email hidden]>,
Russ ([email hidden]'😉 wrote:

> It's also one of the first questions I get asked by
> the various members of my legal team - My head was
> pretty much uninjured, unlike my back - the helmet
> was completely busted in two though so it appears it
> may well have worked very well

A helmet that worked is crushed but not broken. A
helmet that's broken just failed and didn't do any good
at all. Helmets 'work' by plastic deformation (that is,
the foam crushes). This absorbs quite a lot of energy.
If they break they absorb little or no energy in the
process.

Just because it's broken doesn't necessarily mean that
it didn't work though.

[snip]

That's possible, but the fact that it split isn't proof
that it worked.

We'll know for sure soon enough as it's going for forensic
analysis. My bet is that it did what it was supposed to.

Quoted message said:

Quoted message said:

The idea that I could hit the ground with my head at
that speed and not suffer serious head injuries is just
not an option (at the very least I'd have had serious
lacerations).

I hit the ground with my head at something probably over
eighty miles per hour in a car crash four years ago, with
the weight of the car (still rolling) on top of me[1].
They cleaned mud and moss out of my hair in casualty. But
the only injury I sustained was a smashed and crushed
fifth thoracic vertebra; I didn't have even a scratch on
my head, although I did have slight concussion.

Except that that's an injury (like mine) caused by a
stretching of the spine and is caused by a direct
stretching (mine was because I took the impact on the back
of my head) or a whiplash like effect rather than the
actual striking of your head on the ground (or so my
brother who's a consultant in stuff related to this and the
consultants at the spinal injuries unit confirmed tells
me). It's a common enough injury in car crashes even where
there's no head impact at all.

A direct hit with your head results in a cervical (rather
than a thoracic) spinal injury.

Quoted message said:

So, again, you can hit the ground with your head
exceedingly hard (hard enough to crush your backbone)
without injuring your head. Mind you, of course, that may
be because where there's no sense there's no feeling.

See stretching thing above. It may not be hitting your head
hard enough to crush your backbone at all. In my case I know
it was hitting the back of my head that stretched my spine
suffiently to do the damage.

Anyway done this to death now - I guess the forensic
analysis will shed some real light on it.

Russ

In article <[email hidden]>,
[email hidden] says...

Quoted message said:

See stretching thing above. It may not be hitting your
head hard enough to crush your backbone at all. In my case
I know it was hitting the back of my head that stretched
my spine suffiently to do the damage.

A horrible thought. Could it have been the extra leaverage
that the helemt afforded that could have streached your
spine, thus causing your injury? This is a genuine enquirey,
is it the 'aero' design of some helmets that might exasabate
the possible injuries?

Whatever, until there is conclusive exidence that wearing a
helmet is bad, my children will be expected to wear one when
on their bikes. Two of them do so happily, the eldest
doesn't do healthy!
--
.paul

If at first you don't succeed... Skydiving is probably not
the sport for you.