Inflatable helmet, really

Tom Sherman °_° wrote:
On 9/9/2010 10:51 PM, Frank Krygowski wrote:
On Sep 9, 8:37 pm, "MikeWhy" wrote:
Phil W Lee wrote:

Utter bull****.
If cycle helmets met the same standards, don't you think some
motorcyclists would be wearing them?

Not bull****. Look it up if you can figure out Google. Motorcycle
helmets have additional criteria not specified for bicycle
helmets, including coverage area and involving the chin bar when
present. Retention criteria are also more stringent. Impact loads
and survivability, however, are essentially the same.
A funny thing happens when one actually looks up what MikeWhy claims.
Specifically, they find that MikeWhy is either mistaken or lying.

Here's an article that discusses motorcycle helmet testing standards
in detail. (I've got it bookmarked.)
http://www.motorcyclistonline.com/ge...iew/index.html
or http://tinyurl.com/zglbq

What it says? "The killer—the hardest Snell test for a motorcycle
helmet to meet—is a two-strike test onto a hemispherical chunk of
stainless steel about the size of an orange. The first hit is at an
energy of 150 joules, which translates to dropping a 5-kilo weight
about 10 feet—an extremely high-energy impact. The next hit, on the
same spot, is set at 110 joules, or about an 8-foot drop. To pass,
the helmet is not allowed to transmit more than 300 Gs to the
headform in either hit."

Later, it says: "Where the Snell standard limits peak linear
acceleration to 300 G, the DOT effectively limits peak Gs to 250.
Softer impacts, lower G tolerance. In short, a kinder, gentler
standard."

I'm not sure about that "effectively." According to
http://www.smf.org/articles/mcomp2.html
DOT limits acceleration to 400 gs, but from a drop height (for a
large helmet) of about 7.35 feet, or 2.25 meters, which corresponds
to 110 Joules for a 5 kg headform mass.

By contrast, the CPSC bicycle helmet standard calls for just a two
meter drop. It allows 300 gs acceleration of the same headform. The
standards are NOT the same.

Furthermore, the motorcycle helmet standard has much more rigid
penetration tests. This is what drives the design of their heavy,
hard shells. And this is pertinent, because a heavy, hard shell is
less likely to get traction with the road during a tangential impact,
and is more likely to have significant rotational inertia, to aid in
reducing the brain's rotational acceleration. This might be
considered an accidental benefit, because penetration of any helmet
is rare, but rotational brain accelerations are now commonly
recognized as being more likely than linear ones to cause serious
brain injury. (Still, NO helmet standard tests for them!)

What's even more enlightening is that article's discussion of the
effect of various acclerations: "Newman is quoted in the COST study
on the impact levels likely to cause certain levels of injury. Back
in the '80s he stated that, as a rough guideline, a peak linear
impact— the kind we're measuring here&151of 200 to 250 Gs generally
corresponds to a head injury of AIS 4, or severe; that a 250 G to 300
G impact corresponds to AIS 5, or critical; and that anything over
300 Gs corresponds to AIS 6. That is, unsurvivable."

Bike helmets are designed to attenuate the acceleration of a
decapitated human head - no body attached - to 300 gs in a 14 mph
impact. 300 gs is the borderline between critical and unsurvivable,
according to that estimate. And that doesn't take into account
rotational acceleration, which is worse in its effect, and which
helmets may exacerbate (by their larger diameter and higher friction
compared to a bare head).

So leave the cyclist's head attached to his body, subject him to a
head impact greater than 14 mph, include a slight tangential
component to the impact, and you've blown away the "protection" of a
bike helmet.

Is it any wonder they haven't been shown to reduce serious head
injuries?

Dear Frank,

Please stop confusing the Liddites™ with facts - it only makes them
angry that their religious belief in the Magic Foam Bicycle Hat™ is
challenged.

Actually, it's the facts that make you, not me, cringe, run, hide, and blow
smoke. The only agenda *I* have is to counter the misinformation spewed here
about helmet ineffectiveness. There are factual errors and errors of logic
in Frank's post above. I won't address them individually. To do so would be
to spend the rest of eternity talking at insensate and unlearning furniture.
The facts of the matter are these:

The impact load applied in helmet testing is equivalent to a forceful blow
from a 12 pound sledge hammer applied to the helmeted head. You split the
hair if you like between 105 joules, the Snell Memorial Foundation test
specification, and 102 joules, the energy resulting from the CPSC test
specification. To understand what 100 joules looks, sounds, and feels like,
drop a 12 lb bowling ball from eye level to the floor. This is equivalent to
the CPSC impact test on a flat anvil. Choose for yourself whether the small
difference between eyebrow height and a few inches higher is a meaningful
difference. Decide here, this moment, if further discussion is at all
necessary or meaningful.

You can work through the rest of it yourself, given this proper picture of
what the impact test really entails. Bearing in mind that a helmet worn on
the head does nothing for the neck or its attachment to the head, just what
does it mean to substitute the full body mass, as Frank suggests, for the
head mass in the test? I intended that as gently rhetorical, but it would be
interesting to hear further defense of his oddly blind suggestions.

On 9/10/10 1:46 AM, MikeWhy wrote:

The impact load applied in helmet testing is equivalent to a forceful
blow from a 12 pound sledge hammer applied to the helmeted head.

Which is actually less than a typical 'header' bicycle accident, and
really, really far below the impact of a header from getting hit by a
car. In any event, if i were wearing a lid, i would definitely NOT let
you hit me on the head with a 12-pound sledge on the head on a dare, but
get enough beer in me, and I'd take the dare wearing a motorcycle lid.
Maybe. Would take a lot of beer.

On Sep 10, 4:46*pm, "MikeWhy" wrote:
Tom Sherman °_° wrote:
On 9/9/2010 10:51 PM, Frank Krygowski wrote:
On Sep 9, 8:37 pm, "MikeWhy" wrote:
Phil W Lee wrote:

Utter bull****.
If cycle helmets met the same standards, don't you think some
motorcyclists would be wearing them?

Not bull****. Look it up if you can figure out Google. Motorcycle
helmets have additional criteria not specified for bicycle
helmets, including coverage area and involving the chin bar when
present. Retention criteria are also more stringent. Impact loads
and survivability, however, are essentially the same.
A funny thing happens when one actually looks up what MikeWhy claims.
Specifically, they find that MikeWhy is either mistaken or lying.

Here's an article that discusses motorcycle helmet testing standards
in detail. *(I've got it bookmarked.)
http://www.motorcyclistonline.com/ge...lmet_review/in....
*orhttp://tinyurl.com/zglbq

What it says? "The killer—the hardest Snell test for a motorcycle
helmet to meet—is a two-strike test onto a hemispherical chunk of
stainless steel about the size of an orange. The first hit is at an
energy of 150 joules, which translates to dropping a 5-kilo weight
about 10 feet—an extremely high-energy impact. The next hit, on the
same spot, is set at 110 joules, or about an 8-foot drop. To pass,
the helmet is not allowed to transmit more than 300 Gs to the
headform in either hit."

Later, it says: *"Where the Snell standard limits peak linear
acceleration to 300 G, the DOT effectively limits peak Gs to 250.
Softer impacts, lower G tolerance. In short, a kinder, gentler
standard."

I'm not sure about that "effectively." *According to
http://www.smf.org/articles/mcomp2.html
DOT limits acceleration to 400 gs, but from a drop height (for a
large helmet) of about 7.35 feet, or 2.25 meters, which corresponds
to 110 Joules for a 5 kg headform mass.

By contrast, the CPSC bicycle helmet standard calls for just a two
meter drop. *It allows 300 gs acceleration of the same headform. *The
standards are NOT the same.

Furthermore, the motorcycle helmet standard has much more rigid
penetration tests. *This is what drives the design of their heavy,
hard shells. *And this is pertinent, because a heavy, hard shell is
less likely to get traction with the road during a tangential impact,
and is more likely to have significant rotational inertia, to aid in
reducing the brain's rotational acceleration. *This might be
considered an accidental benefit, because penetration of any helmet
is rare, but rotational brain accelerations are now commonly
recognized as being more likely than linear ones to cause serious
brain injury. (Still, NO helmet standard tests for them!)

What's even more enlightening is that article's discussion of the
effect of various acclerations: *"Newman is quoted in the COST study
on the impact levels likely to cause certain levels of injury. Back
in the '80s he stated that, as a rough guideline, a peak linear
impact— the kind we're measuring here&151of 200 to 250 Gs generally
corresponds to a head injury of AIS 4, or severe; that a 250 G to 300
G impact corresponds to AIS 5, or critical; and that anything over
300 Gs corresponds to AIS 6. That is, unsurvivable."

Bike helmets are designed to attenuate the acceleration of a
decapitated human head - no body attached - to 300 gs in a 14 mph
impact. *300 gs is the borderline between critical and unsurvivable,
according to that estimate. *And that doesn't take into account
rotational acceleration, which is worse in its effect, and which
helmets may exacerbate (by their larger diameter and higher friction
compared to a bare head).

So leave the cyclist's head attached to his body, subject him to a
head impact greater than 14 mph, include a slight tangential
component to the impact, and you've blown away the "protection" of a
bike helmet.

Is it any wonder they haven't been shown to reduce serious head
injuries?

Dear Frank,

Please stop confusing the Liddites™ with facts - it only makes them
angry that their religious belief in the Magic Foam Bicycle Hat™ is
challenged.

Actually, it's the facts that make you, not me, cringe, run, hide, and blow
smoke. The only agenda *I* have is to counter the misinformation spewed here
about helmet ineffectiveness. There are factual errors and errors of logic
in Frank's post above. I won't address them individually. To do so would be
to spend the rest of eternity talking at insensate and unlearning furniture.
The facts of the matter are these:

The impact load applied in helmet testing is equivalent to a forceful blow
from a 12 pound sledge hammer applied to the helmeted head. You split the
hair if you like between 105 joules, the Snell Memorial Foundation test
specification, and 102 joules, the energy resulting from the CPSC test
specification. To understand what 100 joules looks, sounds, and feels like,
drop a 12 lb bowling ball from eye level to the floor. This is equivalent to
the CPSC impact test on a flat anvil. Choose for yourself whether the small
difference between eyebrow height and a few inches higher is a meaningful
difference. Decide here, this moment, if further discussion is at all
necessary or meaningful.

You can work through the rest of it yourself, given this proper picture of
what the impact test really entails. Bearing in mind that a helmet worn on
the head does nothing for the neck or its attachment to the head, just what
does it mean to substitute the full body mass, as Frank suggests, for the
head mass in the test? I intended that as gently rhetorical, but it would be
interesting to hear further defense of his oddly blind suggestions.

I would have thought that even the illogic of the Unlidded (can I ™
that?) would have noticed that a motorcyclist impact velocity is
likely to be somewhat higher than that of a cyclist, requiring more
energy to be absorbed and a slightly more arduous test condition for
the safety helmet.

Also, has anyone actually dabbed their head on the ground while
traveling along, to try to gauge the applied torque produced comparing
a bare head to a bicycle helmeted one? What is the coefficient of
dynamic friction of scalp compared to helmet?

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

JS

James wrote:
On Sep 10, 4:46 pm, "MikeWhy" wrote:
Tom Sherman °_° wrote:
On 9/9/2010 10:51 PM, Frank Krygowski wrote:
On Sep 9, 8:37 pm, "MikeWhy" wrote:
Phil W Lee wrote:

Utter bull****.
If cycle helmets met the same standards, don't you think some
motorcyclists would be wearing them?

Not bull****. Look it up if you can figure out Google. Motorcycle
helmets have additional criteria not specified for bicycle
helmets, including coverage area and involving the chin bar when
present. Retention criteria are also more stringent. Impact loads
and survivability, however, are essentially the same.
A funny thing happens when one actually looks up what MikeWhy
claims. Specifically, they find that MikeWhy is either mistaken or
lying.

Here's an article that discusses motorcycle helmet testing
standards in detail. (I've got it bookmarked.)
http://www.motorcyclistonline.com/ge...lmet_review/in...
orhttp://tinyurl.com/zglbq

What it says? "The killer—the hardest Snell test for a motorcycle
helmet to meet—is a two-strike test onto a hemispherical chunk of
stainless steel about the size of an orange. The first hit is at an
energy of 150 joules, which translates to dropping a 5-kilo weight
about 10 feet—an extremely high-energy impact. The next hit, on the
same spot, is set at 110 joules, or about an 8-foot drop. To pass,
the helmet is not allowed to transmit more than 300 Gs to the
headform in either hit."

Later, it says: "Where the Snell standard limits peak linear
acceleration to 300 G, the DOT effectively limits peak Gs to 250.
Softer impacts, lower G tolerance. In short, a kinder, gentler
standard."

I'm not sure about that "effectively." According to
http://www.smf.org/articles/mcomp2.html
DOT limits acceleration to 400 gs, but from a drop height (for a
large helmet) of about 7.35 feet, or 2.25 meters, which corresponds
to 110 Joules for a 5 kg headform mass.

By contrast, the CPSC bicycle helmet standard calls for just a two
meter drop. It allows 300 gs acceleration of the same headform. The
standards are NOT the same.

Furthermore, the motorcycle helmet standard has much more rigid
penetration tests. This is what drives the design of their heavy,
hard shells. And this is pertinent, because a heavy, hard shell is
less likely to get traction with the road during a tangential
impact, and is more likely to have significant rotational inertia,
to aid in reducing the brain's rotational acceleration. This might
be considered an accidental benefit, because penetration of any
helmet is rare, but rotational brain accelerations are now commonly
recognized as being more likely than linear ones to cause serious
brain injury. (Still, NO helmet standard tests for them!)

What's even more enlightening is that article's discussion of the
effect of various acclerations: "Newman is quoted in the COST study
on the impact levels likely to cause certain levels of injury. Back
in the '80s he stated that, as a rough guideline, a peak linear
impact— the kind we're measuring here&151of 200 to 250 Gs generally
corresponds to a head injury of AIS 4, or severe; that a 250 G to
300 G impact corresponds to AIS 5, or critical; and that anything
over 300 Gs corresponds to AIS 6. That is, unsurvivable."

Bike helmets are designed to attenuate the acceleration of a
decapitated human head - no body attached - to 300 gs in a 14 mph
impact. 300 gs is the borderline between critical and unsurvivable,
according to that estimate. And that doesn't take into account
rotational acceleration, which is worse in its effect, and which
helmets may exacerbate (by their larger diameter and higher
friction compared to a bare head).

So leave the cyclist's head attached to his body, subject him to a
head impact greater than 14 mph, include a slight tangential
component to the impact, and you've blown away the "protection" of
a bike helmet.

Is it any wonder they haven't been shown to reduce serious head
injuries?

Dear Frank,

Please stop confusing the Liddites™ with facts - it only makes them
angry that their religious belief in the Magic Foam Bicycle Hat™ is
challenged.

Actually, it's the facts that make you, not me, cringe, run, hide,
and blow smoke. The only agenda *I* have is to counter the
misinformation spewed here about helmet ineffectiveness. There are
factual errors and errors of logic in Frank's post above. I won't
address them individually. To do so would be to spend the rest of
eternity talking at insensate and unlearning furniture. The facts of
the matter are these:

The impact load applied in helmet testing is equivalent to a
forceful blow from a 12 pound sledge hammer applied to the helmeted
head. You split the hair if you like between 105 joules, the Snell
Memorial Foundation test specification, and 102 joules, the energy
resulting from the CPSC test specification. To understand what 100
joules looks, sounds, and feels like, drop a 12 lb bowling ball from
eye level to the floor. This is equivalent to the CPSC impact test
on a flat anvil. Choose for yourself whether the small difference
between eyebrow height and a few inches higher is a meaningful
difference. Decide here, this moment, if further discussion is at
all necessary or meaningful.

You can work through the rest of it yourself, given this proper
picture of what the impact test really entails. Bearing in mind that
a helmet worn on the head does nothing for the neck or its
attachment to the head, just what does it mean to substitute the
full body mass, as Frank suggests, for the head mass in the test? I
intended that as gently rhetorical, but it would be interesting to
hear further defense of his oddly blind suggestions.

I would have thought that even the illogic of the Unlidded (can I ™
that?) would have noticed that a motorcyclist impact velocity is
likely to be somewhat higher than that of a cyclist, requiring more
energy to be absorbed and a slightly more arduous test condition for
the safety helmet.

Also, has anyone actually dabbed their head on the ground while
traveling along, to try to gauge the applied torque produced comparing
a bare head to a bicycle helmeted one? What is the coefficient of
dynamic friction of scalp compared to helmet?

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

JS

Jeezus! I didn't bother to read it. Yet. All I needed was Fig. 2.

http://www.google.com/imgres?imgurl=...w=1132&bih=562

On Sep 10, 3:07*am, James wrote:

I would have thought that even the illogic of the Unlidded (can I ™
that?) would have noticed that a motorcyclist impact velocity is
likely to be somewhat higher than that of a cyclist, requiring more
energy to be absorbed and a slightly more arduous test condition for
the safety helmet.

I would have thought that those arguing in favor of bicycle helmets
would have realized that, therefore, the test standards are NOT the
same, and would not have claimed that they were. In fact, that they'd
realize that some MC helmet impact standards (e.g. Snell) are vastly
different than those of bicycle helmets.

I'd also have thought they'd realize that the extreme differences in
penetration standards - which necessitate very hard shells on MC
helmets - might effect performance of the helmets in other ways that I
mentioned.

Also, has anyone actually dabbed their head on the ground while
traveling along, to try to gauge the applied torque produced comparing
a bare head to a bicycle helmeted one?

I don't know of a test for the effective friction coefficient of a
bare human head subjected to a tangential force from an asphalt
surface. I suspect, though, that the coefficient is much lower than
that of a helmet in the same situation.

The scalp is free to move laterally a certain distance over the
surface of the skull, and it tears relatively easily (and bleeds
messily) if stressed too highly in that direction. I assume this is an
evolutionary (and/or God given, if you prefer) adaptation to protect
the brain from angular accelerations. Angular accelerations are the
kind of motion that's most likely to result in diffuse brain injury,
yet the kind which no helmet standard even bothers to measure.

- Frank Krygowski

http://www.brain-injury-online.com/d...in-injury.html

On Thu, 9 Sep 2010 10:30:45 -0700 (PDT), in rec.bicycles.tech Andre
Jute wrote:

[...]
A "full Irish breakfast" is a delete-option multiple choice. You tell
the landlady, "Leave off the bangers and the black and white puddings,
poach the eggs and crisp the bacon," and then you get a breakfast that
is palatable, looks good on the plate with the mushroom and grilled
tomato, and leaves space for lunch. The "pudding", which I have only
tasted in guest houses, actually tastes good if cooked right. We eat
cereal or toast for breakfast at home, or rarely barley oats porridge
and kippers, so I don't know how to prepare black pudding right, but
suspect it is fried in lethal amounts of fat; not for people our age,
if you won't think me impertinent.

Well, my government is printing money like it's toilet paper;
therefore, everything we did was very expensive based on our country's
currency. We really couldn't afford to have someone cook for us, so
we used our little butane burner extensively. Sorry we couldn't spend
more money, but we spent all we had! If you're close to broke, then
porridge on the beach starts looking a lot better!

We found a nice beach south of Cork and set in there a few nights. We
went into Cork twice by bus. We came due south from the Galway area,
so we didn't get over your way, although, I wanted to do so. The wife
wanted to allocate our time in Waterford and I don't regret it. It
was a nice town in which to walk... but we missed... what is it? ...
the "Ring of Cork"??? (That doesn't sound right.) OTOH, I now have a
Waterford Crystal marble for my marble collection... which was all we
could afford.

I like your pics -- you've found some places down the road from me
that I didn't even know existed -- but I'm surprised you didn't see
more sunshine. August, which is about as far back as I remember, was
so hot, I had to take my rides before dawn for a couple of weeks. No
doubt you noticed how small the Emerald Isle is, so that wherever you
go you're never far from water.

We did see some sun... a little, anyway. I see all of *that* I need
at home; the clouds and rain worked for me, thank you! "so hot..."???
gimme a break! I got 114 (F) degrees in the shade and 3% humidity!
I'm quite happy to get rained on a little bit!

more silly pictures in the desert
http://picasaweb.google.com/ra15932556/BikeTrip#
/more silly pictures in the desert

FYI, "Ajo" is Spanish for "garlic".

OK, so post *your* pictures, asshole!

Jones

On Thu, 9 Sep 2010 20:56:50 -0700 (PDT), in rec.bicycles.tech Frank
Krygowski wrote:

You're boring me, Frank.

I don't care, Jones. I'm not typing for the entertainment of a
troll. I'm merely using you as an excuse to get logic and information
out to others who may be interested.

Are you calling me a "troll", Frank? I'm offended!

Not really.

But, hey! Exactly how many people do you think are hanging on our
every word?

OK!!! ALL OF YOU PEOPLE OUT THERE, SIGN IN AND REPLY *NOW*!

You know, Frank... nobody gives a rat's ass what you think. Nobody
gives a rat's ass what *I* think, either; the difference is that I
know it!

Well... you do, I suppose.

It's too bad we're not queer, Frank... don't you think we'd make a
beautiful couple?

Jones

On Sep 11, 1:35*am, Frank Krygowski wrote:
On Sep 10, 3:07*am, James wrote:

Also, has anyone actually dabbed their head on the ground while
traveling along, to try to gauge the applied torque produced comparing
a bare head to a bicycle helmeted one?

I don't know of a test for the effective friction coefficient of a
bare human head subjected to a tangential force from an asphalt
surface. *I suspect, though, that the coefficient is much lower than
that of a helmet in the same situation.

Maybe your Unliddedness has let your eyesight degrade. I posted a
link. MikeWhy found it. Strangely you overlooked it. Maybe, like so
much else you didn't like the message it brought and chose to sweep it
under the carpet and respond with more rubbish.

JS

JS.