Yet another post about plastic hats

[Ian Smith]

On Tue, 11 Sep 2007 16:03:16 -0700, Squashme <[email protected]> wrote:
>
> I was standing using a cash machine this morning, when there was the
> crash of glass behind me.

If you go round labelled 'squashme', what do you expect?

regards, Ian SMith
--
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|o o|
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[Tony Raven]

"DavidR" <[email protected]> wrote in
news:[email protected]:
>
> As I started this thread saying I am a non-believer, I do wear a hat
> off-road. If I hit an overhanging branch I do expect it to take some
> of the sting away. Knowing this, a hat is therefore a performance
> enhancer. But since it adds another inch to the top of the head, more
> hits are likely because the brain is very good at knowing where the
> top of the head is. For the same reason I also wear eye protection so
> that I don't have to dodge holly bushes.

Back in the days when I used to wear a helmet, I would never wear it
indoors. The reason? I am tall and although I never hit my head normally
on door frames, I did it constantly when I was wearing my helmet. My brain
was adapted to clearing door frames without hitting them but when given
another inch or two on top it constantly misjudged unless I consciously
thought about it. I suspect the same is true off-road - we only hit the
tree branches because our brains are misjudging the clearance needed. As
an aside the most painful off road fall I had was when a branch caught in a
helmet vent and hoiked me off the bike backwards by the helmet.

>
>> I'd be much more interested to hear about some comparative research
>> between injured cyclist wearing and not wearing helmets.
>
> The Dutch don't wear helmets. By all accounts they ought to be
> dropping like flies.
>

Also the two papers by Hewson (links on cyclehelmets.org) look at
comparisons between helmet wearers and non-wearers in the UK police and
hospital accident stats and find no evidence for a benefit.


--
Tony

" I would never die for my beliefs because I might be wrong."
Bertrand Russell

 

[Peter Clinch]

Tony Raven wrote:

> Back in the days when I used to wear a helmet, I would never wear it
> indoors. The reason? I am tall and although I never hit my head normally
> on door frames, I did it constantly when I was wearing my helmet. My brain
> was adapted to clearing door frames without hitting them but when given
> another inch or two on top it constantly misjudged unless I consciously
> thought about it. I suspect the same is true off-road - we only hit the
> tree branches because our brains are misjudging the clearance needed.

Up to a point...
Orienteering on Sunday, no helmet, lots of head strikes on branches.
Why? The bit of forest I was negotiating didn't leave much choice
because there were branches at all levels with no clear path between
that avoided them. There really wasn't much choice except cover your
eyes and barge on through and take the flak. Roos joked later on (in a
not especially amused manner, it has to be said) that full body armour
might have been handy. She's got an interesting set of scratches and
bruises...

You will hit tree branches for reasons of basically not enough
clearance, period, as well as misjudging. The degree to which the
former happens will depend on the specific venue. As with caving, where
I always wear a lid despite knowing I'll hit my head more, I would
speculate there are venues where you're better off with some armour as
several inconsequential hits are probably better than a single one that
really hurts.

What do I do on an MTB? Technical trails around Glen Tress with /lots/
of branch potential at all vertical levels, happy to wear one. XC in
the 'Gorms for a Munro bag, no.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email protected] http://www.dundee.ac.uk/~pjclinch/

 

[Peter Clinch]

7@m3 G33k wrote:
> Tony Raven wrote:

>> PS The plural of anecdote is anecdotes and not data and helmets that
>> fracture have failed, not worked.

> Erm...wrong - this is precisely how expanded polystyrene helmets work.
> The energy of the impact is absorbed in deforming the helmet rather than
> your skull.

He said "fracture", you said "deforming". Not the same thing. If it
fractures it doesn't necessarily deform first. Brittle fracture absorbs
practically no energy.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email protected] http://www.dundee.ac.uk/~pjclinch/

 

[7@m3 G33k]

Martin Dann wrote:
>
> There is that famous piece of american research that shows that wearing
> a cycle helmet reduces the chances of leg injuries by a significant amount.
>
> There is Dr Walkers research that drivers drive closer to cyclists
> wearing a MFH, than to those not wearing a MFH.
>
> There is research into risk compensation that shows wearing a helmet
> makes you take more risks.
>

Interesting stuff - any pointers as to where these may be found on-line?

>
> Remember that with good (expensive) helmets, you are often just paying
> more for bigger holes.
>

I'm happy to pay for those holes as it is always my intention to spend
less time falling off and more time actually cycling i.e. getting hot
and sweaty - I've suffered under a poorly ventilated lid and for me the
extra is worth it. That said well-ventilated lids are cheaper even in
absolute terms now than they were 5 or 10 years ago.

Ian

 

[Adrian Godwin]

7@m3 G33k <[email protected]> wrote:

> formal encounter with professional medical services. As you love my
> anecdotes so much here's another: I don't recall a single off-road ride
> on which I haven't had some small knocks on my helmet from miscellaneous
> low-hanging objects. That proves nothing other than that I like to come
> home from a ride without minor scrapes and bruises on my scalp.
>

I think you'll find others here who like them for that sort of usage,
though it doesn't seem relevant to road riding.

However, the disposable polystyrene helmets would seem particularly
unsuited to this application : you're trying to protect yourself from
repeated small knocks and abrasions, possibly on lower head and neck
as well as above the hairline. A canoe helmet with its resilient
surface, wider coverage, smaller diameter and recoverable foam is
probably well suited (and maybe this is the basis for some of the
MTB/BMX helmets - I haven't studied them).

-adrian

 

[marc]

7@m3 G33k wrote:
> Martin Dann wrote:
>>
>> There is that famous piece of american research that shows that
>> wearing a cycle helmet reduces the chances of leg injuries by a
>> significant amount.
>>
>> There is Dr Walkers research that drivers drive closer to cyclists
>> wearing a MFH, than to those not wearing a MFH.
>>
>> There is research into risk compensation that shows wearing a helmet
>> makes you take more risks.
>>
>
> Interesting stuff - any pointers as to where these may be found on-line?
>
>>
>> Remember that with good (expensive) helmets, you are often just paying
>> more for bigger holes.
>>
>
> I'm happy to pay for those holes as it is always my intention to spend
> less time falling off and more time actually cycling i.e. getting hot
> and sweaty - I've suffered under a poorly ventilated lid and for me the
> extra is worth it. That said well-ventilated lids are cheaper even in
> absolute terms now than they were 5 or 10 years ago.


and nowhere near the standard they were 16 years ago!

 

[Ian Smith]

On Wed, 12 Sep 2007 08:46:58 GMT, 7@m3 G33k <> wrote:
> Tony Raven wrote:
> >
> > PS The plural of anecdote is anecdotes and not data and helmets that
> > fracture have failed, not worked.
>
> Erm...wrong - this is precisely how expanded polystyrene helmets work.
> The energy of the impact is absorbed in deforming the helmet rather than
> your skull.

Oh dear.

You do understand the difference between "fracture" (no significant
deformation, very little energy) and "deforming" (lots of energy
absorbed), don't you?

regards, Ian SMith
--
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[Peter Clinch]

Adrian Godwin wrote:
> 7@m3 G33k <[email protected]> wrote:
>
>> formal encounter with professional medical services. As you love my
>> anecdotes so much here's another: I don't recall a single off-road ride
>> on which I haven't had some small knocks on my helmet from miscellaneous
>> low-hanging objects. That proves nothing other than that I like to come
>> home from a ride without minor scrapes and bruises on my scalp.

> I think you'll find others here who like them for that sort of usage,
> though it doesn't seem relevant to road riding.

Or indeed a lot of off-road riding. Cycling 10 miles across landy
tracks in the 'Gorms for a remote Munro bag, where exactly will I find
these "low hanging objects"?

> However, the disposable polystyrene helmets would seem particularly
> unsuited to this application : you're trying to protect yourself from
> repeated small knocks and abrasions, possibly on lower head and neck
> as well as above the hairline. A canoe helmet with its resilient
> surface, wider coverage, smaller diameter and recoverable foam is
> probably well suited (and maybe this is the basis for some of the
> MTB/BMX helmets - I haven't studied them).

I'd agree. Caving helmets, likewise, which are designed on the exact
principle that they *will* get lots of small knocks. Never seen a
polystyrene foam one, they're all hard shell with a load-spreading cradle.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email protected] http://www.dundee.ac.uk/~pjclinch/

 

[Matt B]

Ian Smith wrote:
> On Wed, 12 Sep 2007 08:46:58 GMT, 7@m3 G33k <> wrote:
>> Tony Raven wrote:
>>> PS The plural of anecdote is anecdotes and not data and helmets that
>>> fracture have failed, not worked.
>> Erm...wrong - this is precisely how expanded polystyrene helmets work.
>> The energy of the impact is absorbed in deforming the helmet rather than
>> your skull.
>
> Oh dear.
>
> You do understand the difference between "fracture" (no significant
> deformation, very little energy) and "deforming" (lots of energy
> absorbed), don't you?

There are, of course, two distinct types of fracture: brittle and ductile.

Could it be with a helmet, that the effect of the deformation caused by
the impact (absorbing the shock), combined with, say, the restraining
effect of any shell, or of the fixing straps, or of the foam geometry
itself, could induce enough bending (it only has to be a small amount)
to trigger a brittle fracture in the foam - i.e. it does its job, /then/
breaks.

--
Matt B

 

[The Luggage]

On 12 Sep, 09:04, Peter Clinch <[email protected]> wrote:
>
> What do I do on an MTB? Technical trails around Glen Tress with /lots/
> of branch potential at all vertical levels, happy to wear one. XC in
> the 'Gorms for a Munro bag, no.

Is riding up them not counted as cheating??

TL

 

[_]

On Wed, 12 Sep 2007 08:56:47 GMT, 7@m3 G33k wrote:

>
> I'm happy to pay for those holes as it is always my intention to spend
> less time falling off and more time actually cycling i.e. getting hot
> and sweaty - I've suffered under a poorly ventilated lid and for me the
> extra is worth it. That said well-ventilated lids are cheaper even in
> absolute terms now than they were 5 or 10 years ago.
>

The helmet with the biggest holes is free.

 

[_]

On Wed, 12 Sep 2007 08:46:58 GMT, 7@m3 G33k wrote:

>
> Erm...wrong - this is precisely how expanded polystyrene helmets work.
> The energy of the impact is absorbed in deforming the helmet rather than
> your skull.
>

No.

A fracture is indeed a kind of deformation, but one which, for the material
used in foam hats, takes a *very* small amount of energy. The greatest
energy absorbed by this material comes when it is compressed without
fracture - which usually requires a impact with a blunt object normal to
the pivot centre.

Fractures are usually a sign that the foam hat experienced an impact that
was offset from the pivot centre; such impacts are the ones most likely to
cause rotational injuries, which require roughly an order of magnitude less
energy than direct impacts. This much smaller energy requirement, combined
with the probability that such impacts are more likely, the additional size
and the additional friction of the foam hat may well be the reason that
head injury rates do not decline (some studies show an increase) following
sudden large increases in foam hat wearing.

 

[Peter Clinch]

The Luggage wrote:
> On 12 Sep, 09:04, Peter Clinch <[email protected]> wrote:
>> What do I do on an MTB? Technical trails around Glen Tress with /lots/
>> of branch potential at all vertical levels, happy to wear one. XC in
>> the 'Gorms for a Munro bag, no.
>
> Is riding up them not counted as cheating??

I wouldn't know, I just use the bike for the approach... Can save a
couple of hours and a lot of grind compared to walking.

There are probably a few you can top out by bike as easily on foot, but
mainly c.f. the bikes/walking efficiency thread and the limiting
problems caused by boulder fields on steep slopes.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email protected] http://www.dundee.ac.uk/~pjclinch/

 

[David Martin]

On Sep 12, 11:21 am, Matt B <[email protected]> wrote:
> Ian Smith wrote:
> > On Wed, 12 Sep 2007 08:46:58 GMT, 7@m3 G33k <> wrote:
> >> Tony Raven wrote:
> >>> PS The plural of anecdote is anecdotes and not data and helmets that
> >>> fracture have failed, not worked.
> >> Erm...wrong - this is precisely how expanded polystyrene helmets work.
> >> The energy of the impact is absorbed in deforming the helmet rather than
> >> your skull.
>
> > Oh dear.
>
> > You do understand the difference between "fracture" (no significant
> > deformation, very little energy) and "deforming" (lots of energy
> > absorbed), don't you?
>
> There are, of course, two distinct types of fracture: brittle and ductile.
>
> Could it be with a helmet, that the effect of the deformation caused by
> the impact (absorbing the shock), combined with, say, the restraining
> effect of any shell, or of the fixing straps, or of the foam geometry
> itself, could induce enough bending (it only has to be a small amount)
> to trigger a brittle fracture in the foam - i.e. it does its job, /then/
> breaks.

No. In that particular case an impact has occurred which wouldn't have
occurred otherwise. The effective head size with a helmet is much
larger, so you are more likely to hit things that without a helmet
would have missed completely.

...d

 

[Matt B]

_ wrote:
> On Wed, 12 Sep 2007 08:46:58 GMT, 7@m3 G33k wrote:
>
>> Erm...wrong - this is precisely how expanded polystyrene helmets work.
>> The energy of the impact is absorbed in deforming the helmet rather than
>> your skull.
>
> No.

Well yes - if the impact is absorbed /before/ the helmet breaks.

> A fracture is indeed a kind of deformation, but one which, for the material
> used in foam hats, takes a *very* small amount of energy.

Which could occur /after/ the main impact has been absorbed.

> The greatest
> energy absorbed by this material comes when it is compressed without
> fracture - which usually requires a impact with a blunt object normal to
> the pivot centre.

Yes, but that doesn't then prevent it from fracturing due to resultant,
smaller, bending forces.

> Fractures are usually a sign that the foam hat experienced an impact that
> was offset from the pivot centre;

A bending force, in fact. Such as on a part which is unsupported by
your head (so bends freely rather than being compressed against the head).

Consider the likely differences in outcome between hitting, with a
brick, a hollow polystyrene shell with nothing inside it, and hitting a
similar shell filled with concrete.

--
Matt B

 

[David Damerell]

Quoting 7@m3 G33k <[email protected]>:
>Damn...there I go talking rot again. However not as much rot as:
>"cycling helmets offer no significant protection". A friend of mine
>recently went over the handlebars after the cyclist in-front braked and
>wobbled without warning. She landed on her head, shoulder and hip: badly
>bruised hip, hairline fracture to the upper-arm, helmet in two pieces
>and head completely unscathed.

When did you repeat the experiment with a control unhelmeted head?
--
OPTIONS=name:Kirsty,menustyle:C,female,lit_corridor,standout,time,showexp,hilit
e_pet,catname:Akane,dogname:Ryoga,fruitkonomiyaki,pickup_types:"!$?=/,scores:
5 top/2 around,color,boulder:0,autoquiver,autodig,disclose:yiyayvygyc,pickup_bu
rden:burdened,!cmdassist,msg_window:reversed,!sparkle,horsename:Rumiko,showrace

 

[David Damerell]

Quoting 7@m3 G33k <[email protected]>:
>of research that you cite. The vast majority of injuries (especially for
>those not cycling on roads) that helmets prevent would not enter the
>statistics as they are not likely to be serious enough to require a
>formal encounter with professional medical services.

Wait, if we're talking about cuts and bruises, do you also wear BMX elbow
and knee pads?

>prone to injury. Until then I'm happy with my anecdotes that prove
>nothing because I *know* that I and plenty of cyclists of my
>acquaintance have avoided more and less serious injuries by wearing a
>good helmet.

Where "know" means "guess".
--
OPTIONS=name:Kirsty,menustyle:C,female,lit_corridor,standout,time,showexp,hilit
e_pet,catname:Akane,dogname:Ryoga,fruitkonomiyaki,pickup_types:"!$?=/,scores:
5 top/2 around,color,boulder:0,autoquiver,autodig,disclose:yiyayvygyc,pickup_bu
rden:burdened,!cmdassist,msg_window:reversed,!sparkle,horsename:Rumiko,showrace

 

[David Martin]

On Sep 12, 2:35 pm, David Damerell <[email protected]>
wrote:
> Quoting 7@m3 G33k <[email protected]>:
>
> >of research that you cite. The vast majority of injuries (especially for
> >those not cycling on roads) that helmets prevent would not enter the
> >statistics as they are not likely to be serious enough to require a
> >formal encounter with professional medical services.
>
> Wait, if we're talking about cuts and bruises, do you also wear BMX elbow
> and knee pads?

On his head? Or does he wear long sleeved tops/full length leggings to
prevent scratches etc. and just lives with the soft tissue injury as
regards minor bruises.

...d

 

[Peter Clinch]

David Martin wrote:
> On Sep 12, 2:35 pm, David Damerell <[email protected]>
> wrote:
>> Quoting 7@m3 G33k <[email protected]>:
>>
>>> of research that you cite. The vast majority of injuries (especially for
>>> those not cycling on roads) that helmets prevent would not enter the
>>> statistics as they are not likely to be serious enough to require a
>>> formal encounter with professional medical services.
>> Wait, if we're talking about cuts and bruises, do you also wear BMX elbow
>> and knee pads?
>
> On his head? Or does he wear long sleeved tops/full length leggings to
> prevent scratches etc. and just lives with the soft tissue injury as
> regards minor bruises.

Well that's not really fair, asking questions where the answers don't
fit with rationalising existing behaviour... ;-/

(I know about rationalising existing behaviour with respect to helmets:
I found out I was doing exactly that, shortly before I stopped wearing
one following a decade or so of one on every trip when I was quite
convinced it was the common sense thing to do, backed up with lots of
reasons and projections and anecdotes).

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email protected] http://www.dundee.ac.uk/~pjclinch/