Helmet Wankers

[Tony Raven]

David Kerber wrote:
>
> Do you have any cites for the claim that helmets "amplify the rotational component" of a head
> impact to any significant degree? I don't need to see them for the fact that rotational
> acclerations are more damaging to the brain; that is well-known, and has been for many years.
>

Curnow WJ "The efficacy of bicycle helmets against brain injury", Accident Analysis and Prevention,
Vol 35, pp287-292 (2003)

http://tinyurl.com/3hnav (abstract plus link if you are registered to full article)

In other sports, the role of helmets in increasing rotational injuries is also known. See for
example: http://www.ipvca.org/coaches_connection_medical_helmets.htm

Tony

 

[Just Zis Guy]

On Sun, 08 Feb 2004 03:23:01 GMT, bikinchris
<[email protected]> wrote in message
<[email protected]>:

><url:http://starbulletin.com/2004/02/02/news/index3.html>

A perect example of why the helmet lobby's arrogation of the entire bike safety agenda is profoundly
undesirable.

Guy
===
May contain traces of irony. Contents liable to settle after posting.
http://chapmancentral.demon.co.uk

 

[Just Zis Guy]

On Sun, 08 Feb 2004 11:07:25 GMT, Graeme
<[email protected]> wrote in message
<[email protected]>:

>This is getting scary Guy, I find myself agreeing with your posts more and more, and now I find we
>both have the same degree.

Luke, I am your father...

Where did you do the B.Eng? If it was Southampton please be aware that the world will have reached a
degree of smallness where China may require a second layer.

Guy
===
May contain traces of irony. Contents liable to settle after posting.
http://chapmancentral.demon.co.uk

 

[Mark Thompson]

> Curnow WJ "The efficacy of bicycle helmets against brain injury", Accident Analysis and
> Prevention, Vol 35, pp287-292 (2003)
>
> http://tinyurl.com/3hnav (abstract plus link if you are registered to full article)
>
> In other sports, the role of helmets in increasing rotational injuries is also known. See for
> example: http://www.ipvca.org/coaches_connection_medical_helmets.htm

wot he said, and

Bicyclists, helmets and head injuries: a rider-based study of helmet use and effectiveness
Wasserman RC, Waller JA, Monty MJ, Emery AB, Robinson DR 1988. American Journal of Public Health:
1988 Sep;78(9):1220-1

suggests that helmeted riders are seven times more likely to hit their heads. I guess that this is
something to do with the control groups, but it's not hard to think of several ways that helmets
make you more likely to headbutt things (size, weight, risk comp etc).

---
Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.577 / Virus Database: 366 - Release Date: 03/02/2004

 

[Tim Woodall]

On Sat, 07 Feb 2004 19:26:05 -0800,
Benjamin Lewis <[email protected]> wrote:
> David Kerber wrote:
>
>>>>> God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t," and there was light.
>>>>
>>>> So are you an EE or a Physicist?
>>>>
>>> Physicist.
>>>
>>> Tim.
>>
>> That was my guess; most EE's of my acquaintance (including me) aren't that big into theory to
>> remember the basic equations years later, even though they certainly learned them at one time.
>
> Also, I was under the impression that EEs usually express these in a different format.
>
So do Physicists nowadays but, IIRC "dF = 0" just doesn't have the same ring to it.

Tim.

--
God said, "div D = rho, div B = 0, curl E = - @B/@t, curl H = J + @D/@t," and there was light.

http://tjw.hn.org/ http://www.locofungus.btinternet.co.uk/

 

[Graeme]

"Just zis Guy, you know?" <[email protected]> wrote in
news:[email protected]:

> Luke, I am your father...

That explains it, the Dark Side has been calling for some years now. Unfortunately SWMBO has been
calling for different things (weddings, moving to the other side of the world etc.) which means my
bank balance seldom reaches the relevant level (although I wouldn't have to pay shipping on a
Greenspeed trike now

> Where did you do the B.Eng? If it was Southampton please be aware that the world will have reached
> a degree of smallness where China may require a second layer.

Phew! It was Edinburgh. The only link I have to Southampton is having been there a couple of times
visiting the council for work purposes. So the mutation may not reach the moustache stage.

Mind you, I'm sure I've got a virtual 'tache, here I am sitting in Australia and I'm listening to
Radio 4 via broadband- Gardener's Question Time even! It may even be a virtual beard, pipe and
slippers :-O



Graeme

 

[Tony Raven]

Graeme wrote:
>
> Mind you, I'm sure I've got a virtual 'tache, here I am sitting in Australia and I'm listening to
> Radio 4 via broadband- Gardener's Question Time even! It may even be a virtual beard, pipe and
> slippers :-O
>

Off to uk.rec.sheds with you ;-)

Tony

 

[David Reuteler]

In rec.bicycles.misc Graeme <[email protected]> wrote:
: EE = electrical engineer? That's me (well, at least if what your degree was defines you). V=IR is
: about all I can remember instantly, most other stuff takes a bit of thinking or a book :-/ Mind
: you, I fell into the computer side of things soon after graduating and even Ohm's law became
: irrelevant
: :-/

i was physics but otherwise resemble that remark. what with the ample employment opportunities in
physics proper i'd say 50% of my graduating class (1993) went into computers. of 30 (physics had
such wonderfully small class sizes! & this at the university of minnesota twin cities) half into
computers, 2 went to graduate school in physics, 3 became high school science teachers, couple went
into engineering. a few found jobs in physics. not sure about the rest. love the major, tho. it has
always served me well.
--
david reuteler [email protected]

 

[David Kerber]

In article <[email protected]>, [email protected] says...
> On Sat, 7 Feb 2004 20:14:07 -0500, David Kerber <ns_dkerber@ns_ids.net> wrote in message
> <[email protected]>:
>
> >most EE's of my acquaintance (including me) aren't that big into theory to remember the basic
> >equations years later, even though they certainly learned them at one time.
>
> Always assuming that their lecturers, call them for the sake of argument Professor Hammond, made
> the bloody things comprehensiuble in the first place.

LOL! I was pretty lucky that way: most of my professors had been working engineers before coming
back to teach.

--
Dave Kerber Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.

 

[David Kerber]

In article <[email protected]>, [email protected] says...
> On Sun, 08 Feb 2004 01:45:01 GMT, Graeme <[email protected]> wrote in message
> <[email protected]>:
>
> >EE = electrical engineer? That's me (well, at least if what your degree was defines you). V=IR is
> >about all I can remember instantly, most other stuff takes a bit of thinking or a book
>
> Scarily true. I can't remember most calculus any more.

I have forgotten some of mine, but I still use some, and I've been learning a bit of linear algebra
as well, in my current job working for a statistician.

>
> (B.Eng Hons, Electrical Engineering)
>
> Guy
> ===
> May contain traces of irony. Contents liable to settle after posting.
> http://chapmancentral.demon.co.uk
>

--
Dave Kerber

B.S. EE, Magna Cum Laude, UMR

Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.

 

[David Kerber]

In article <[email protected]>, junk@raven- family.com says...
> David Kerber wrote:
> >
> > Do you have any cites for the claim that helmets "amplify the rotational component" of a head
> > impact to any significant degree? I don't need to see them for the fact that rotational
> > acclerations are more damaging to the brain; that is well-known, and has been for many years.
> >
>
> Curnow WJ "The efficacy of bicycle helmets against brain injury", Accident Analysis and
> Prevention, Vol 35, pp287-292 (2003)
>
> http://tinyurl.com/3hnav (abstract plus link if you are registered to full article)

That abstract draws no conclusions at all; it just says that the it study it examined wasn't
properly designed to draw the conclusions it did. Kind of like declaring a defendent in a trial to
be not guilty because the prosecution didn't prove the case beyond a reasonable doubt: it does not
say the defendent didn't do it, only that it was not proven that he did do it.

> In other sports, the role of helmets in increasing rotational injuries is also known. See for
> example: http://www.ipvca.org/coaches_connection_medical_helmets.htm

That one is more interesting, and presents an issue I hadn't thought of, and which could certainly
be an issue in bicycle crashes with the projections they typically have in front of and behind the
head. Of course they are discussing neck injuries, and not head injuries, but it still needs to be
considered.

Note that neither one of these links you provided supports your assertion that helmets exacerbate
rotational injuries to the brain. Do you have any others which do?

--
Dave Kerber Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.

 

[Tony Raven]

David Kerber wrote:
>
> That abstract draws no conclusions at all; it just says that the it study it examined wasn't
> properly designed to draw the conclusions it did. Kind of like declaring a defendent in a trial to
> be not guilty because the prosecution didn't prove the case beyond a reasonable doubt: it does not
> say the defendent didn't do it, only that it was not proven that he did do it.
>

Well pay your money and read the whole article then.

>
> Note that neither one of these links you provided supports your assertion that helmets exacerbate
> rotational injuries to the brain. Do you have any others which do?

In your enthusiasm to attack you miss the fact that I made no such assertion. I was just
responding to your request for information on helmets and rotational injuries. Helmets can
exacerbate the rotational effects for which you should look at section 7 of
http://www.bhsi.org/chinstrp.pdf which found some helmets created rotational accelerations
significantly in excess of the recommended maximum.

Tony

 

[David Kerber]

In article <[email protected]>, junk@raven- family.com says...
> David Kerber wrote:
> >
> > That abstract draws no conclusions at all; it just says that the it study it examined wasn't
> > properly designed to draw the conclusions it did. Kind of like declaring a defendent in a trial
> > to be not guilty because the prosecution didn't prove the case beyond a reasonable doubt: it
> > does not say the defendent didn't do it, only that it was not proven that he did do it.
> >
>
> Well pay your money and read the whole article then.
>
> >
> > Note that neither one of these links you provided supports your assertion that helmets
> > exacerbate rotational injuries to the brain. Do you have any others which do?
>
> In your enthusiasm to attack you miss the fact that I made no such assertion.

I realized after making my post that you were not the one who posted the message I was initially
answering; he _did_ make that claim. I apologize for that mistake.

> I was just responding to your request for information on helmets and rotational injuries. Helmets
> can exacerbate the rotational effects for which you should look at section 7 of
> http://www.bhsi.org/chinstrp.pdf which found some helmets created rotational accelerations
> significantly in excess of the recommended maximum.

That's an interesting study, but based on their descriptions, I'm not sure it applies to most
bicycle helmets that people actually wear. They didn't describe in much detail what a "non-shell"
helmet is, which they noted was the only one which gave significant rotational force to the head.
Would that be the leather style ones which you used to see on racers? Their description of
"ribbed hard-shell" helmets seems to be consistent with the description of the ones most riders
wear these days.

--
Dave Kerber Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.

 

[Tony Raven]

David Kerber wrote:
>
> That's an interesting study, but based on their descriptions, I'm not sure it applies to most
> bicycle helmets that people actually wear. They didn't describe in much detail what a "non-shell"
> helmet is, which they noted was the only one which gave significant rotational force to the head.
> Would that be the leather style ones which you used to see on racers? Their description of
> "ribbed hard-shell" helmets seems to be consistent with the description of the ones most riders
> wear these days.

Hardshell is one like a motorbike helmet, microshell is what most of of are used to with the thin
glossy plastic outer layer and non-shell is the old style bare polystyrene. Another interesting
paper is http://www.bhsi.org/hodgstud.htm. They say the 4500r/s/s is not exceeded on any of the
helmets but also their maximum speed is 6.4mph. If you look at the traces near the end they are not
that much below the limit to consider you would stay within the limits at not much higher speeds.
There is no control data though on the bare human head. Its also noticeable that the vented helmets
they show have virtually no vents compared with today. It could do with an updated study with
current helmet designs.

Tony

 

[David Kerber]

In article <[email protected]>, junk@raven- family.com says...
> David Kerber wrote:
> >
> > That's an interesting study, but based on their descriptions, I'm not sure it applies to most
> > bicycle helmets that people actually wear. They didn't describe in much detail what a "non-
> > shell" helmet is, which they noted was the only one which gave significant rotational force to
> > the head. Would that be the leather style ones which you used to see on racers? Their
> > description of "ribbed hard-shell" helmets seems to be consistent with the description of the
> > ones most riders wear these days.
>
> Hardshell is one like a motorbike helmet, microshell is what most of of are used to with the thin
> glossy plastic outer layer and non-shell is the old style bare polystyrene. Another interesting
> paper is

For hard shell, I was also thinking of the ones BMX riders wear. I don't remember ever seeing a bare
polystyrene helmet. The slick outer covering on current helmet designs seems unlikely to "catch" on
pavement unless some kind of object (sewer grate, curb edge, car mirror?) grabs one of the
ventilation holes.

> http://www.bhsi.org/hodgstud.htm. They say the 4500r/s/s is not exceeded on any of the helmets but
> also their maximum speed is 6.4mph. If you look at the traces near the end they are not that much
> below the limit to consider you would stay within the limits at not much higher speeds. There is
> no control data though on the bare human head. Its also noticeable that the vented helmets they
> show have virtually no vents compared with today. It could do with an updated study with current
> helmet designs.

Sounds like it.

--
Dave Kerber Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.

 

[Chris Malcolm]

Dave Kahn <[email protected]> writes:

>On Sun, 08 Feb 2004 21:37:59 +0000, "Just zis Guy, you know?" <[email protected]> wrote:

>>Interesting. I was recently told that the mechanism by which helmets absorb energy is plastic
>>deformation, which is why the Snell standards specify the helmet must not break. Apparently if a
>>helmet breaks this is an indication that it has moved from plastic deformation to brittle failure,
>>a mode in which it absorbs virtually no energy. So all those cracked helmets which "saved people's
>>lives" actually simply failed!

>Guy, do you know of a clear reference to this? IOW a concise authoritative statement that a
>shattered helmet is a failed helmet?

>I've come across plenty of photos of broken or chipped helmets along with descriptions of how the
>helmet saved someone's life. If the helmets actually failed that suggests that not only did they
>not save the lives in question, but that they failed in a relatively trivial incident.

It's not an either-or situation. For example, a helmet might absorb most of the impact by plastic
deformation, and then crack. It might absorb a lot of impact, fly off the head, and get cracked all
on its own. And so on.

--
Chris Malcolm [email protected] +44 (0)131 651 3445 DoD #205
IPAB, Informatics, JCMB, King's Buildings, Edinburgh, EH9 3JZ, UK
[http://www.dai.ed.ac.uk/homes/cam/]

 

[Frkrygow]

David Kerber wrote:

> For hard shell, I was also thinking of the ones BMX riders wear. I don't remember ever seeing a
> bare polystyrene helmet. The slick outer covering on current helmet designs seems unlikely to
> "catch" on pavement unless some kind of object (sewer grate, curb edge, car mirror?) grabs one of
> the ventilation holes.

I'm not convinced.

First, I have seen bare polystyrene helmets. They were popular in the mid '80s, as I recall. Some
were sold with gossamer-thin fabric coverings, claimed to hold the helmet pieces together if it
shattered. Worries of neck injuries took them off the market, and at least some helmet promoters
began saying you should buy a new one if that's what you had.

Today's helmets are mostly "microshell" - a thin (0.003") vacuum-formed plastic covering taking the
place of the gossamer fabric or the hard shell. Less weight & less expense than a hard shell.

But will 0.003" of relatively soft plastic keep the helmet from "catching" on the hard, rough-
textured asphalt? Perhaps it might help a tiny bit, but I doubt it helps much.

Of course, that's my feeling on the entire helmet. Maybe a tiny bit of help, but not much.

--
Frank Krygowski [To reply, omit what's between "at" and "cc"]

 

[W K]

"Nick Maclaren" <[email protected]> wrote in message
news:[email protected]...
> In article <[email protected]>, David Kerber <ns_dkerber@ns_ids.net> wrote:

> >Do you have any cites for the claim that helmets "amplify the rotational component" of a head
> >impact to any significant degree? I don't need to see them for the fact that rotational
> >acclerations are more damaging to the brain; that is well-known, and has been for many years.
>
> I haven't seen any analyses of experimental data, though I have heard that there may have been a
> little for motorcyclists and/or horse riders. It is, however, immediate from the physics involved
> that they are very LIKELY to do that.
>
> Most accidents involving reasonably cautious cyclists have the cyclist coming off sideways - even
> being hit from behind at a fairly low relative speed will do that. If someone comes off sideways,
> the impact is on hip, shoulder and sometimes knee and elbow. Because a helmet increases both the
> width and the moment of the head by a significant factor, it is very likely to cause head/helmet
> contact where it would not otherwise have happened. Q.E.D.

Only by about 20% and there is a far less friction between shell/road and head/road. So not QED.

 

[Just Zis Guy]

"Dave Kahn" <[email protected]> wrote in message
news:[email protected]...

> >I was recently told that the mechanism by which helmets absorb energy is plastic deformation,
> >which is why the Snell standards specify the helmet must not break. Apparently if a helmet breaks
> >this is an indication that it has moved from plastic deformation to brittle failure, a mode in
> >which it absorbs virtually no energy. So all those cracked helmets which "saved people's lives"
> >actually simply failed!

> Guy, do you know of a clear reference to this? IOW a concise authoritative statement that a
> shattered helmet is a failed helmet?

I am trying to get one. The source was not a public one, but there must be some public-domain
references I can quote. My contacts have been, er, contacted. Like I said, it is something I was
only recently told.

--
Guy
===

WARNING: may contain traces of irony. Contents may settle after posting.
http://www.chapmancentral.co.uk

 

[Marc]

David Kerber <ns_dkerber@ns_ids.net> wrote:

> Do you have any cites for the claim that helmets "amplify the rotational component" of a head
> impact to any significant degree?

2PiR ?

--
Marc. Please note the above address is a spam trap, use marcc to reply Printing for clubs of all
types http://www.jaceeprint.demon.co.uk Stickers, banners & clothing, for clubs,teams, magazines
and dealers.