More magic helmets

Tim Hall said:

My local freesheet had a story last week about a bike-lorry collision.
The cyclist was reported as being dragged for 50 feet by the lorry and
is in hospital in a critical condition.

See http://tinyurl.com/f8wel

'The driver of the truck, who did not want to be named, said: "The guy just
came from nowhere and then went right under me."'

So, as well as sporting a magic helmet, it appears he rider also possesses
other magic powers.

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

Quoted message said:

My local freesheet had a story last week about a bike-lorry collision.
The cyclist was reported as being dragged for 50 feet by the lorry and
is in hospital in a critical condition.

See http://tinyurl.com/f8wel

Two quotations from the article:

'Broken fragments of his cycle helmet and shreds of his clothing also
littered the scene.'

'Inspector Mark Piper, of Crawley Police, said: "This incident
highlights the vital importance of wearing a cycle helmet."

"The cyclist was wearing his helmet and that might make the vital
difference between life and death."'

I feel a letter coming on.

Tim

"The driver of the truck, who did not want to be named, said: "The guy just
came from nowhere and then went right under me. It was terrifying.""

WTF is that all about?

May be the 70 year old cyclist "beamed in" like on Star Trek...

Why wasn't the 70 year old cyclist using the under-pass at Broadfield?

And, if he was T-boned, who didn't look? One of them is likely to be very
incompetent.

http://maps.google.co.uk/maps?f=q&hl=en&q=southgate+roundabout,+Crawley,+West+Sussex,+RH11&om=1

Quoted message said:

Quoted message said:

'Broken fragments of his cycle helmet and shreds of his clothing also
littered the scene.'
'Inspector Mark Piper, of Crawley Police, said: "This incident
highlights the vital importance of wearing a cycle helmet."

"The cyclist was wearing his helmet and that might make the vital
difference between life and death."'

Maybe it was his cycle clothing that made the difference ........
Makes you think......
Robert

So his helmet shattered - great, it was really useful then! Doesn't say
that his head did though, so perhaps this 'highlights the vital
importance' of wearing a skull to protect the brain ; - )

On Tue, 9 May 2006 11:47:58 +0100 someone who may be "Simon Bennett"
<[email hidden]> wrote this:-

Quoted message said:

'The driver of the truck, who did not want to be named, said: "The guy just
came from nowhere and then went right under me."'

So, as well as sporting a magic helmet, it appears he rider also possesses
other magic powers.

Indeed. Presumably the 70 year old cycles at something close to the
speed of light, so that he can appear from nowhere.

--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Blonde said:

this 'highlights the vital
importance' of wearing a skull to protect the brain ; - )

I never laeve home without mine. I have been known to get out of it, mind.

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

Quoted message said:

Blonde said:

this 'highlights the vital
importance' of wearing a skull to protect the brain ; - )

I never laeve home without mine. I have been known to get out of it, mind.

Conversely, some road-users leave their brains behind. ;-)

Blonde said:

So his helmet shattered - great, it was really useful then!

They're supposed to. Dissipates impact apparently.
--

Martin Bulmer

Tim Hall said:

"The cyclist was wearing his helmet and that might make the vital
difference between life and death."'

Which way?
--

Martin Bulmer

On Tue, 9 May 2006 23:13:57 +0100 someone who may be "Martin Bulmer"
<[email hidden]> wrote this:-

Quoted message said:

Quoted message said:

So his helmet shattered - great, it was really useful then!

They're supposed to.

No they're not.

Quoted message said:

Dissipates impact apparently.

Helmets are supposed to work by the polystyrene being crushed. While
being crushed it absorbs a fair amount of energy.

If it shatters that does not absorb very much energy at all. The
helmet has not done what it is supposed to do and it has not
protected the rider other then to a minimal extent.

--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

David Hansen said:

The
helmet has not done what it is supposed to do and it has not
protected the rider other then to a minimal extent.

I thought that protecting the rider to a minimal extent was exactly
what it was supposed to do....

IGMC.

"Bob"
--

Email address is spam trapped, to reply directly remove the beverage.

David Hansen said:

On Tue, 9 May 2006 23:13:57 +0100 someone who may be "Martin Bulmer"
<[email hidden]> wrote this:-

Quoted message said:

Quoted message said:

So his helmet shattered - great, it was really useful then!

They're supposed to.

No they're not.

Quoted message said:

Dissipates impact apparently.

Helmets are supposed to work by the polystyrene being crushed. While
being crushed it absorbs a fair amount of energy.

If it shatters that does not absorb very much energy at all. The
helmet has not done what it is supposed to do and it has not
protected the rider other then to a minimal extent.

When I used to wear one, mine sort of did that - the external shell was
left intact but the polystyrene cracked when I had a bad accident and
hit the ground from about 40mph. I was not all that convinced of the
merit of the helmet though as it did not prevent me from getting
concussion (or road rash :- ( !!!)

Blonde said the following on 09/05/2006 16:38:

Quoted message said:

So his helmet shattered - great, it was really useful then!

They're meant to do that. It means the helmet absorbed the impact
rather than the skull.

--
Paul Boyd
http://www.paul-boyd.co.uk/

Paul Boyd said:

Blonde said the following on 09/05/2006 16:38:

Quoted message said:

So his helmet shattered - great, it was really useful then!

They're meant to do that. It means the helmet absorbed the impact
rather than the skull.

You need to understand the difference in energy absorption between
brittle fracture and compression. If it has shattered, its not meant to
do that, it has failed by brittle fracture and it has not absorbed much
energy. A helmet that has worked as intended will be intact with
crushed polystyrene at the point of impact.

--
Tony

"The best way I know of to win an argument is to start by being in the
right."
- Lord Hailsham

Paul Boyd said:

Quoted message said:

So his helmet shattered - great, it was really useful then!

They're meant to do that.

No, they're meant to crush. The energy absorbed when a helmet splits is
far smaller (an order of magnitude IIRC) than the energy absorbed when
it crushes.

Quoted message said:

It means the helmet absorbed the impact
rather than the skull.

It meant the helmet absorbed far less energy than it should, ie the head
absorbed far more.

R.

On Wed, 10 May 2006 12:37:08 +0100 someone who may be Paul Boyd
<[email hidden]> wrote this:-

Quoted message said:

Quoted message said:

So his helmet shattered - great, it was really useful then!

They're meant to do that.

Incorrect.

Quoted message said:

It means the helmet absorbed the impact rather than the skull.

Incorrect. It means that the helmet absorbed very little energy and
what it didn't absorb was passed on to the skull.

A helmet that had been crushed would be a different matter.

The mechanics are fairly simple. Next contestant please.

--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

in message <[email hidden]>, Martin Bulmer

(') said:

Blonde said:

So his helmet shattered - great, it was really useful then!

They're supposed to. Dissipates impact apparently.

They are /not/ supposed to break, they are supposed to crush. If they
crush, they absorb a lot of energy; if they break, virtually none. To
verify this, take a piece of polystyrene foam (what helmets are made
of). Try to crush it. It's difficult. It resists crushing, absorbing a
surprising amount of your energy. Now try to break it. How much energy
did that take?

A broken helmet just failed. It didn't do it's job at all.

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

((DoctorWho)ChristopherEccleston).act();
uk.co.bbc.TypecastException: actor does not want to be typecast.
[adapted from autofile on /., 31/03/05]

in message <[email hidden]>, Richard

(') said:

Paul Boyd said:

Quoted message said:

So his helmet shattered - great, it was really useful then!

They're meant to do that.

No, they're meant to crush. The energy absorbed when a helmet splits
is far smaller (an order of magnitude IIRC) than the energy absorbed
when it crushes.

I think you'll find that's more like three orders of magnitude.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; We don't just borrow words; on occasion, English has pursued other
;; languages down alleyways to beat them unconscious and riffle their
;; pockets for new vocabulary -- James D. Nicoll

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

Quoted message said:

On Tue, 9 May 2006 23:13:57 +0100 someone who may be "Martin Bulmer"
<[email hidden]> wrote this:-

Quoted message said:

Quoted message said:

So his helmet shattered - great, it was really useful then!

They're supposed to.

No they're not.

Quoted message said:

Dissipates impact apparently.

Helmets are supposed to work by the polystyrene being crushed. While
being crushed it absorbs a fair amount of energy.

If it shatters that does not absorb very much energy at all. The
helmet has not done what it is supposed to do and it has not
protected the rider other then to a minimal extent.

Is it possible to say exactly how much the helmet protected the rider
without knowing at which point the helmet shattered.

The article says that the cyclist was dragged for 15 metres. If the helmet
was being crushed for 14 of those 15 metres and only shattered in the last 1
metre then it did protect the rider. If it shattered upon impact then it was
useless.

Adam