Bizarre coincidence, but saved by their helmets.

On 02/10/2010 12:37, Derek C wrote:
On Oct 2, 12:16 pm, wrote:
On 02/10/2010 12:00, Derek C wrote:





On Oct 2, 10:32 am, wrote:
On 02/10/2010 08:40, Derek C wrote:

On Sep 29, 4:43 pm, wrote:
On 29/09/2010 11:00, Derek C wrote:

On Sep 28, 8:45 pm, Tony wrote:
Derek C wrote:

So if you have an accident where you have a head impact in the range
700 - 800 joules, up to 1100 joules in some cases, wearing a cycle
helmet will prevent a skull fracture.

Unlikely. At those energies the helmet is receiving up to ten times its
maximum design energy and will fail catastrophically. Second, at the
velocities associated with those energies, the additional mass of the
helmet strapped to the head adds about as much energy to the impact as
it absorbs if it works perfectly.

However the brain is most likely
to be damaged by a high g deceleration, whether or not the skull is
fractured, with a maximum short term tolerance of about 300 g for an
average person. Modern cycle helmets cushion the head so that they
limit the loading to about 200g in a reasonably survivable impact.

You know even less about neurology than you do about physics.
Coup-contrecoup injuries are not typically the problem.

Tony

You obviously haven't read the link I provided for Mark.

http://www.motorcyclistonline.com/ge...lmet_review/in...

I did, when I asked"
However the brain is most likely
to be damaged by a high g deceleration, whether or not the skull is
fractured, with a maximum short term tolerance of about 300 g for an
average person.

Source?"

I expected a more rigorous source than a magazine article. You haven't
yet supplied your vector force diagram of a cyclist coming off "head
first" yet either , or even commented upon the physics of 100J equating
to a 10mph accident . Are you equipped to continue this discussion in
terms of physics, or as your critics point out is your contribution
simply to be arm waving and "commonsense"?- Hide quoted text -

- Show quoted text -

TRL PPR446 comes to more or less the same conclusions if you want
something more scientific. If you fall off a push bike or motorbike
and strike your head on the road surface, it matters little if you are
doing 5mph or 100mph, apart from subsequent minor abrasion injuries.

Are you really trying to say that a helmet will have the same effect
if the 80Kg rider has 197J of Ke or 79000J ?

It's the height of the fall that is most significant, hence drop tests
are valid.

Is your physics up to giving figures for a 1.75M fall under 1G at 5mph
compered with a 1.75M fall at 100mph?

The vertical acceleration (deceleration) is the same in either case as
long as the road surface is flat and nothing else such as a kerbstone
is struck after the initial hit. The force of gravity remains
constant.

So in your model 5mph=100mph? I ask because if you say that gravity is
a constant and that the impact energy is the same then the inputs must
also be the same. As this sort of physics is wayyyy beyond my
understanding could you please show the equation that you use in your
model?







I can't find a Google reference to how many Joules a helmet will
absorb, as most papers refer to reducing g loadings.

"Most papers", are you sure? What papers have you read?

Even if it is

100J, the important thing is that it is the initial 100J and
subsequent loadings on the brain will be reduced by this amount, even
if the helmet fails at this stage.

Really? so what happens if there is a 5mph blow to the head of a
stationary helmet wearer, does this mean that the "loading on the brain"
( forgetting the head's built in "shock absorbers") will be -87? How low
or high must the figure be to avoid brain damage?

Permanent brain damage starts at about 300g for more than a couple of
milliseconds. This reference includes a graph showing the difference
between a helmeted and unhelmeted head form.

There were two questions, you ignored the first. Here it is again

" Really? so what happens if there is a 5mph blow to the head of a
stationary helmet wearer, does this mean that the "loading on the
brain" ( forgetting the head's built in "shock absorbers") will be -87?"?

It's a closed question, the answer will be Yes or No...







If you apply the front brake hard at speed, the front wheel will act
as a fulcrum about which the whole bike and rider will rotate
(assuming the front tyre doesn't skid). Motorcyclists and BMX riders
make use of this effect to do stoppies, where the bike ends up
balanced on the front wheel (if you get it right!). See:

http://www.youtube.com/watch?v=KlLjF...208922&playnex...

But where's the force vector diagram showing the rider coming off "head
first"? You are capable of producing one , aren't you? You wanted to use
physics to make your argument, I've yet to see you use any, do you
understand the principles and forces involved or do you simply cut and
paste words that you think will impress?-

Normally in a higher speed sudden stop, the rider will just be thrown
forward over the handlebars after a small amount of rotation.

But where's the force vector diagram showing the rider coming off "head
first"? It's a physics problem, so express it as a physics solution...
you can do that can't you? You wanted to use "simple physics", now's
your chance.- Hide quoted text -


As I have already pointed out, I cannot easily post vector diagrams to
this newsgroup.


Send it here

On Sat, 2 Oct 2010 04:00:14 -0700 (PDT), Derek C
wrote:

The vertical acceleration (deceleration) is the same in either case as
long as the road surface is flat and nothing else such as a kerbstone
is struck after the initial hit. The force of gravity remains
constant.

So you keep saying. Unfortunately for you, the classical model of an
object hitting a frictionless horizontal plane does not exist outside
of basic textbook exercises.

Permanent brain damage starts at about 300g for more than a couple of
milliseconds. This reference includes a graph showing the difference
between a helmeted and unhelmeted head form.

It is strongly dependent on the nature of the force. Rotational forces
have much more serious effects than linear forces.

Guy
--
http://www.chapmancentral.co.uk/
The usenet price promise: all opinions offered in newsgroups are guaranteed
to be worth the price paid.

On Sat, 02 Oct 2010 12:28:08 +0100, Marc wrote:

http://www.bhsi.org/foam.htm


Are you sure you are a scientist? That's not a graph, where is the
scale, what's it measuring, what are the axes? It hasn't even got a
title! That would have received scorn from any tutor seeing it in even
the very first paper of a first year undergraduate, pathetic! The very
fact that you even think that this might be an explanation shows, to me
at least, that you don't even understand the ideas of physics let alone
how to work with or express them.

Oh but it must be 100% reliable, it supports DerekC's religious
convictions. Never mind that the site owner sincerely believes that
the 85% / 88% figures are correct, even though they are now
acknowledged by their authors to be unsupported, and in any case won't
stop using them because a change "would not be helpful". The two of
them would get along fine, neither seems terribly inclined to let
facts stand in the way of their conclusions.

Guy
--
http://www.chapmancentral.co.uk/
The usenet price promise: all opinions offered in newsgroups are guaranteed
to be worth the price paid.

On Oct 2, 3:13*pm, "Just zis Guy, you know?"
wrote:
On Sat, 02 Oct 2010 12:28:08 +0100, Marc wrote:
http://www.bhsi.org/foam.htm

Are you sure you are a scientist? That's not a graph, where is the
scale, what's it measuring, what are the axes? *It hasn't even got a
title! That would have received scorn from any tutor seeing it in even
the very first paper of a first year undergraduate, pathetic! The very
fact that you even think that this might be an explanation shows, to me
at least, that you don't even understand the ideas of physics let alone
how to work with or express them.

Oh but it must be 100% reliable, it supports DerekC's religious
convictions. Never mind that the site owner sincerely believes that
the 85% / 88% figures are correct, even though they are now
acknowledged by their authors to be unsupported, and in any case won't
stop using them because a change "would not be helpful". The two of
them would get along fine, neither seems terribly inclined to let
facts stand in the way of their conclusions.

Guy

Pot? Kettle? cyclehelmets.org?

On Sat, 02 Oct 2010 13:32:47 +0100, Round repeated


153 lines of ****e - just to add one more line :

Send it here



ffs - can't you learn to do anything?



--

Per billion passenger kilometres

Car KSI 18
Cycle KSI 541
Pedestrian 358

(KSI : Killed or Seriously Injured)
Dft 2008 FIgures

Who says cycling is safer than walking?

On Sat, 2 Oct 2010 08:27:49 -0700 (PDT), Derek C
wrote:

On Oct 2, 3:13*pm, "Just zis Guy, you know?"
wrote:
On Sat, 02 Oct 2010 12:28:08 +0100, Marc wrote:
http://www.bhsi.org/foam.htm

Are you sure you are a scientist? That's not a graph, where is the
scale, what's it measuring, what are the axes? *It hasn't even got a
title! That would have received scorn from any tutor seeing it in even
the very first paper of a first year undergraduate, pathetic! The very
fact that you even think that this might be an explanation shows, to me
at least, that you don't even understand the ideas of physics let alone
how to work with or express them.

Oh but it must be 100% reliable, it supports DerekC's religious
convictions. Never mind that the site owner sincerely believes that
the 85% / 88% figures are correct, even though they are now
acknowledged by their authors to be unsupported, and in any case won't
stop using them because a change "would not be helpful". The two of
them would get along fine, neither seems terribly inclined to let
facts stand in the way of their conclusions.

Guy

Pot? Kettle? cyclehelmets.org?

No, but thanks for asking. (Hint: the people involved in CHO almost
all started out as advocates and became more sceptical in response to
conflicting evidence).

Guy
--
http://www.chapmancentral.co.uk/
The usenet price promise: all opinions offered in newsgroups are guaranteed
to be worth the price paid.

On Sat, 02 Oct 2010 15:13:39 +0100, "Just zis Guy, you know?"
wrote:

snip


Oh but it must be 100% reliable, it supports DerekC's religious
convictions.


I forgot that you were an expert on religious convictions.


Is it true that you cannot answer the simple question :

"Did you posts as Lou Knee"?

because if you said "No" - your God would strike you down.


--

"I have never said that I encourage my children to wear helmets. I would challenge judith
to find the place where I said I encourage my children to wear helmets." Guy Chapman
Judith then produced the web page where he said "I encourage my children to wear helmets."
Later that day Chapman immediately added the following to the web page:
"This page is out of date and preserved only for convenience" but he left the date last updated as 31/08/2004.

On 02/10/2010 16:27, Derek C wrote:
On Oct 2, 3:13 pm, "Just zis Guy, you
wrote:
On Sat, 02 Oct 2010 12:28:08 +0100, wrote:
http://www.bhsi.org/foam.htm

Are you sure you are a scientist? That's not a graph, where is the
scale, what's it measuring, what are the axes? It hasn't even got a
title! That would have received scorn from any tutor seeing it in even
the very first paper of a first year undergraduate, pathetic! The very
fact that you even think that this might be an explanation shows, to me
at least, that you don't even understand the ideas of physics let alone
how to work with or express them.

Oh but it must be 100% reliable, it supports DerekC's religious
convictions. Never mind that the site owner sincerely believes that
the 85% / 88% figures are correct, even though they are now
acknowledged by their authors to be unsupported, and in any case won't
stop using them because a change "would not be helpful". The two of
them would get along fine, neither seems terribly inclined to let
facts stand in the way of their conclusions.

Guy

Pot? Kettle?cyclehelmets.org?

Let's have a look shall we?
Oh Yes!
http://www.cyclehelmets.org/1079.html

Graphs, with titles, lableled axes, scales, units of measurment (Ok the
Sustrans one is a bit iffy) that looks like the output of scientists. So
on the one hand we have a "graph" that can mean anything that anyone
wants it to mean, that doesn't meet any sort of criteria, on the other
there are graphs which meet the standard of acceptable practice when
discussing scientific ideas. Look more like the pot calling the kettle
black when in actual fact the kettle is a clear, transparent, shining
example of labware.

By the way, I haven't received the vector diagram of your "simple
physics" problem yet.

Having had a good laugh at the utter desperation of the anti helmet
psycholists, one has to wonder why they are so adverse to wearing a simple
safety device?

How can a padded helmet not be safer than a bare head? A clear case of
denial.

Is it because they are terrified of any form of regulation, fearing that it
might lead to taxation?

Is it because helmets would make them look bigger dickheads than they
already do?

Don't know what all the fuss is about anyway. Cyclists don't have much in
the way of brains to damage.


--
Dave - intelligent enough to realise that a push bike, like a skateboard, is
a kid's toy, not a viable form of transport.

On Oct 2, 4:50*pm, Marc wrote:
On 02/10/2010 16:27, Derek C wrote:





On Oct 2, 3:13 pm, "Just zis Guy, you
wrote:
On Sat, 02 Oct 2010 12:28:08 +0100, *wrote:
http://www.bhsi.org/foam.htm

Are you sure you are a scientist? That's not a graph, where is the
scale, what's it measuring, what are the axes? *It hasn't even got a
title! That would have received scorn from any tutor seeing it in even
the very first paper of a first year undergraduate, pathetic! The very
fact that you even think that this might be an explanation shows, to me
at least, that you don't even understand the ideas of physics let alone
how to work with or express them.

Oh but it must be 100% reliable, it supports DerekC's religious
convictions. Never mind that the site owner sincerely believes that
the 85% / 88% figures are correct, even though they are now
acknowledged by their authors to be unsupported, and in any case won't
stop using them because a change "would not be helpful". The two of
them would get along fine, neither seems terribly inclined to let
facts stand in the way of their conclusions.

Guy

Pot? Kettle?cyclehelmets.org?

* Let's have a look shall we?
Oh Yes!http://www.cyclehelmets.org/1079.html

Graphs, with titles, lableled axes, scales, units of measurment (Ok the
Sustrans one is a bit iffy) that looks like the output of scientists. So
on the one hand we have a "graph" that can mean anything that anyone
wants it to mean, that doesn't meet any sort of criteria, on the other
there are graphs which meet the standard of acceptable practice when
discussing scientific ideas. Look more like the *pot calling the kettle
black when in actual fact the kettle is a *clear, transparent, shining
example of labware.

By the way, I haven't received the vector diagram of your "simple
physics" problem yet.- Hide quoted text -

- Show quoted text -

If graphs are just intended to be be comparative and produced by the
same method, there is not a total need for defined units of
measurement, although it would be better if there where. There are
some pretty dodgy graphs in cyclehelmets.org, but not as dodgy as
their use of statistics!

Derek C