Helmet ******s

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

In rec.bicycles.misc Graeme 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

Nearly right. In fact the motorcycle crashes tended to be more
seriously injurious of the riders. The interesting point is that
somehow this greater risk of injury in crashes balanced out the lesser
incidence of crashes to produce the *same* risk of injury per mile.

Was this just an extraordinary co-incidence?

The suggestion of the author was that *if* risk compensation occurs,
we should expect it to be most clearly demonstrated in the most
experienced and capable people, because those are the people whose
appreciation of the risks and of their own capabilities would be the
most realistic.

That's why he chose specially trained police drivers and riders, those
who've graduated from the special advanced training courses.

His suggestion was that these experienced capable drivers and riders
had a certain level of injury risk which they felt comfortable with,
and adjusted their behaviour on motorcycles or cars in such a way as
to compensate for the very different characteristics and
vulnerabilities of these different vehicles, so that they ended up,
realistically, taking the same level of risk. Risk compensation.

Of course that study didn't *prove* risk compensation, it simply
either exemplified it well or was a remarkable coincidence. You need
to pile up some more, and fail to find counter-examples, to strengthen
the case.

And this intuitively feels right.

Someone is going to howl me down about this but it just seems obvious to
me that there is a perceived risk level I am ok with and one I am not.
And that the more experience one has the more likely the percieved risk
is to be close to the real risk.

Incidently my ex, a crap driver if anyone was went on to fail the
police pursuit course... twice

Dave

In article , 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_connect...al_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.

In article ,
says...
On Sat, 7 Feb 2004 20:14:07 -0500, David Kerber
wrote in message
:

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.

In article ,
says...
On Sun, 08 Feb 2004 01:45:01 GMT, Graeme
wrote in message
:

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 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

In article , 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.

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

On Sun, 8 Feb 2004 20:08:43 -0000, "Tony Raven"
wrote in message
:

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

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
===
May contain traces of irony. Contents liable to settle after posting.
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