published helmet research - not troll

John Forrest Tomlinson wrote:
On Sat, 19 Jun 2004 22:31:00 -0400, Steven Bornfeld
wrote:


Mandatory inspection makes a lot more sense to me than
mandatory CPSC regs such as reflectorized pedals.


Who and how many people would this help? In talking about public
policy, you've got to ask what is the benefit and what is the cost? I
see benefit for an extremely small amount of people and cost for an
extremely large number of people. So I don't understand the point of
this suggestion.

JT

I don't know the answer to this. One might think that self-interest
would make automobile inspections unnecessary as well--maybe you agree.
But if you don't, I do not see a fundamental difference in principle.

Steve

"Just zis Guy, you know?" wrote in message
...
On Sat, 19 Jun 2004 23:34:30 GMT, "Shayne Wissler"
wrote in message
944Bc.71708$eu.12036@attbi_s02:

Casual observation would imply the opposite. Helmets are more slippery
than
skin,

Er, not quite. That only really applies to hard shell helmets.

If you say so.

and they have a larger radius than the skull.

Correct. This amplifies rotational forces.

The rate of rotation is diminished with the larger radii. And it's the
acceleration to that rate that matters not the torque.

Also, the helmet is not
as tightly coupled to the head as the skin is

Incorrect. A correctly fitted helmet will not rotate on the head.

I wasn't talking about the helmet spinning freely here, I'm talking about a
small rotation on impact. Surely you don't fasten your helmet to your head
with epoxy?


Shayne Wissler

"Just zis Guy, you know?" writes:

On Sat, 19 Jun 2004 23:34:30 GMT, "Shayne Wissler"
wrote in message
944Bc.71708$eu.12036@attbi_s02:

Some of the following is yet more grasping at straws and more
repetition of arguments that were shot down a decade ago.

Casual observation would imply the opposite. Helmets are more slippery than
skin,

Er, not quite. That only really applies to hard shell helmets.

and they have a larger radius than the skull.

Correct. This amplifies rotational forces.

The increased moment arm does not produce a major change, but as a
result of the added material, you get better protection against an
impact and protection against abrasion (which causes unslightly road
rash to the head.) Until a 'road-rash look' comes into style, you
might want temporary head hair removal left to your barber.

Also, the helmet is not
as tightly coupled to the head as the skin is

Incorrect. A correctly fitted helmet will not rotate on the head.

A correctly fitted helmet will rotate slightly. It is not
glued in place.

--
My real name backwards: nemuaZ lliB

Shayne Wissler wrote:

"VC" wrote in message
om...

"Shayne Wissler" wrote in message

news:TQJAc.135474$Ly.96010@attbi_s01...

snip of implication that helmets may increase risk of rotational brain
injury

Not everything is what it seems to be. A helmet may indeed not be so
good for your health.


Nice imagination, but do you have any actual reason to believe that helmets
increase the rotational forces involved?

Casual observation would imply the opposite. Helmets are more slippery than
skin...

I doubt that bike helmets are more slippery than skin - or, more
properly, skin covered with a good layer of hair. It's been my guess
that human evolution left hair on the head partly for that reason - to
reduce the effect of a glancing blow (whether in accident or on combat).

When the hair alone can't handle it, the scalp is pretty easily torn,
exposing the well-lubricated scalp layers - a messy but effective second
line of defense.

No-shell bike helmets were taken off the market when it was claimed they
grabbed the asphalt. The microshells that are now popular don't look
very convincing to me. I'd think they would conform to, and lock to,
asphalt roughness. Perhaps not... but AFAIK, they haven't been tested
for this. Certainly the standards don't address it.

... and they have a larger radius than the skull.

This causes two effects, one probably beneficial, one probably
detrimental. On the good side, the speed of the glancing surface
corresponds to less angular velocity. On the down side, the increased
moment arm means increased torque to cause angular acceleration.
Perhaps the effect is a more rapid acceleration for a shorter period of
time - but again, it hasn't been tested, AFAIK, and it's not addressed
in the standard.

Also, the helmet is not
as tightly coupled to the head as the skin is...

Well, tight straps are demanded by the helmet promoters, and it seems to
me the coupling is enough to induce some serious angular acceleration.
Scalp skin seems (deliberately?) loose. But again: no testing, no
standard.

... and if the helmet got a large
impulse of rotational force from a localized postion on the helmet, it would
tend to be ripped apart, damping the force.

That could certainly help. I wish there were testing or a standard that
addressed it precisely.

But it's interesting - if this is really what saves a person from
excessive angular acceleration of the brain, then helmet proponents may
need a new song. Instead of "My helmet broke, so it saved my life!!!!"
they may need to say "Thank God my helmet broke, so it didn't kill
me!!!"

--
--------------------+
Frank Krygowski [To reply, remove rodent and vegetable dot com,
replace with cc.ysu dot edu]

"Frank Krygowski" wrote in message
...

Casual observation would imply the opposite. Helmets are more slippery
than
skin...

I doubt that bike helmets are more slippery than skin - or, more
properly, skin covered with a good layer of hair. It's been my guess
that human evolution left hair on the head partly for that reason - to
reduce the effect of a glancing blow (whether in accident or on combat).

It's far more biologically plausible to speculate that the hair is for looks
or for protection from the sun or both.

snip

Perhaps not... but AFAIK, they haven't been tested
for this. Certainly the standards don't address it.

The helmet research I've seen so far is junk--it focuses on population
statistics not physics, and is motivated to social change not truth.

If researchers really cared about the truth of the matter, they would take
some of this casual analysis and more and begin formulating good models for
this so they'd have more to go by than mere emergency room statistics, and
also have a means of specifying better helmets. Maybe the manufacturers do
this, I don't know.


Shayne Wissler

Bill Z. wrote:

Mark & Steven Bornfeld DDS writes:

As for actually calculating the quantitative saving of lives,
this is always more complicated than it seems.

Except that "saving lives" isn't the issue - ... The real question is the
extent to which helmets reduce injuries.

IIRC, every helmet promotion I've ever encountered has talked about
saving lives. If that's not the issue, someone needs to inform the
"safety industry."

And regarding injuries - did you ever read that 1996 paper by Scuffham,
that detected no difference in serious injuries?

If they reduce them enough
to pay for the cost of the helmet through reductions in the cost of
treating an injury, the thing will pay for itself.

"An Economic Evaluation of the Mandatory Bicycle Helmet Legislation in
Western Australia" by Hendrie, Legge et. al. found that the Australian
helmet law almost certainly did not pay for itself.

BTW, in terms of mandating them, the real argument against doing that
is the wide spread in annual mileage. I know people who ride many
thousands of miles each year and others whose yearly mileage rarely
exceeds 5 or 10 miles. Do you require a helmet for a person who
rides such short distances? We are talking, after all about a
factor of a 1000 in annual mileage.

This is a good point. A helmet is more likely to be of value to a high
mileage cyclist than to a neighborhood cruiser - although IMO it's not a
"must" for any but the most extreme cyclists.

Still, the helmet promoters don't agree. They tend to say "Wear a
helmet for EVERY ride," or [quoting from the biggest helmet-promotion
site:] "The Bicycle Helmet Safety Institute supports carefully drawn
mandatory helmet laws covering all age groups..."

Of course, "carefully drawn" intends no exceptions for low mileage!

Got a bike you ride five miles per year? Gotta buy a helmet!!!!

--
--------------------+
Frank Krygowski [To reply, remove rodent and vegetable dot com,
replace with cc.ysu dot edu]

On Sun, 20 Jun 2004 10:23:42 -0400, Steven Bornfeld
wrote in message
:

One might think that self-interest
would make automobile inspections unnecessary as well--maybe you agree.
But if you don't, I do not see a fundamental difference in principle.

IIRC, automobile inspections were the result of concerns over the
damage done to others by inadequately maintained cars. The cost to
society of a single car with no brakes can be huge.

In the UK it started because large numbers of pre-war vehicles were
still on the roads in dangerously unroadworthy condition even into the
early 1960s. The test originally covered vehicles over ten years old,
which was subsequently reduced to three years. As Michael Flanders
once put it: "there's even been some talk of having them tested before
they leave the factory."

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

88% of helmet statistics are made up, 65% of them at Washington University

On Sun, 20 Jun 2004 15:11:21 GMT, "Shayne Wissler"
wrote in message
tOhBc.81019$HG.42994@attbi_s53:

Casual observation would imply the opposite. Helmets are more slippery
than skin,
Er, not quite. That only really applies to hard shell helmets.
If you say so.

I don't, actually - the comment was made to me by someone who tests
bicycle helmets for a living.

and they have a larger radius than the skull.
Correct. This amplifies rotational forces.

The rate of rotation is diminished with the larger radii. And it's the
acceleration to that rate that matters not the torque.

The increased radius can result in a force which turns the head
against the restraint of the neck muscles, where no rotation woudl
occur had the increased radius been absent.

Also, the helmet is not
as tightly coupled to the head as the skin is

Incorrect. A correctly fitted helmet will not rotate on the head.

I wasn't talking about the helmet spinning freely here, I'm talking about a
small rotation on impact. Surely you don't fasten your helmet to your head
with epoxy?

The scalp also rotates over the skull. And these days I mostly don't
fasten my helmet to my head: the only crash I've had in recent years I
hit the ground butt first from a height of 15".

But hey, I don't intend to argue about this any more because frankly I
don't know whether helmets make rotational injuries worse, or do
nothing on balance (far the most likely, in my view) or make them
better (how?) - as far as I can see nobody is actually researching
this. I don't know why. Maybe it's because all the research dollars
are still tied up in failed attempts to duplicate TR&T (hint: just
compare two completely different groups, that does it).

All I know is that whenever anybody even suggests that helmets /may/
make rotational injuries worse, they get shouted down but no actual
evidence is produced. On either side. Only comments to the effect
that it needs further investigation, a position with which I entirely
agree.

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

88% of helmet statistics are made up, 65% of them at Washington University

On Sun, 20 Jun 2004 16:04:19 GMT, "Shayne Wissler"
wrote in message
7AiBc.85246$Sw.42132@attbi_s51:

The helmet research I've seen so far is junk--it focuses on population
statistics not physics, and is motivated to social change not truth.

For varying values of "junk" - small scale prospectiuve studies are
certainly prone to error, but whole population evidence is harder to
ignore. That's what proved the link between smoking and cancer.

If researchers really cared about the truth of the matter, they would take
some of this casual analysis and more and begin formulating good models for
this so they'd have more to go by than mere emergency room statistics, and
also have a means of specifying better helmets. Maybe the manufacturers do
this, I don't know.

The manufacturers don't care a damn as far as I can tell. They have
pushed through lower standards and it's almost impossible to find a
helmet made to Snell B95.

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

88% of helmet statistics are made up, 65% of them at Washington University

Shayne Wissler wrote:

The helmet research I've seen so far is junk--it focuses on population
statistics not physics, and is motivated to social change not truth.

If researchers really cared about the truth of the matter, they would take
some of this casual analysis and more and begin formulating good models for
this so they'd have more to go by than mere emergency room statistics, and
also have a means of specifying better helmets. Maybe the manufacturers do
this, I don't know.

I seriously doubt the manufacturers do anything that won't improve their
bottom line!

Of course, they can improve their bottom line by giving money to Snell,
which can give money to Safe Kids Inc. and various lobbyists, who can
lobby legislators to mandate their products, whether or not they work!

But manufacturers charge over $150 for gossamer-thin racing helmets that
have significantly less impact protection than average bike helmets,
while still (barely) passing the test standards.

Clearly, they're not in the protection business; they're in the business
of selling helmets.


--
--------------------+
Frank Krygowski [To reply, remove rodent and vegetable dot com,
replace with cc.ysu dot edu]