Helmets

yk wrote:
The price range from $10 - $200. What are the differences ? Are
expensive helmets safer or more aero-dynamically designed ? What to look
for besides fit and color ? TIA

Three things to look for in a helmet, fit, fit and ohh yes, fit.

More expensive ones may be 'cooler' in terms of temp and looks but all
are approved to the same 'low' standrards of safety in terms of height
and speed. 4 ft and 14 MPH...

On point! Hell-mutt nazis never address rotation/shear brain injuries. The
statistical data is corrupt but

The conspiracy of ignorance masquerades as common sense.


wrote in message
...

I grant you that. He might have made it to dead sooner w/o the
helment. I don't remember anyone blaming his broken neck on the
helmet.

In article , says...
The price range from $10 - $200. What are the differences ?

Advertising. Lighter weight. Lastest fad color scheme.

Are expensive helmets safer or more aero-dynamically designed ?

Possibly more aero. If you as the manufacturer, they will tell you their
cheapest helmets are just as safe as their expensive ones.

What to look for besides fit and color ? TIA

ANSI or SNELL sticker is important. I find that high end helmets with prior
years color schemes tend to be the best deals. You can usually find them
for about 1/3 the price of the latest fad color.
---------------
Alex

mark wrote:
wrote ...


mark wrote:
In other words, look for fit, color, an acceptable level of ventilation
and
a reasonably sturdy retention system. And keep in mind that they really
won't help much at speeds over 12-15 mph, and they won't do much good in
the
typical cyclist/car collision.

It depends. If you go head first into a windshield, it will absorb some
of the energy, as will the windshield itself. It is certainly better
than nothing, but it is not designed to provide full protection from
that type of impact. If you are launched into the air, it will absorb
the energy of the fall from whatever height your head reaches, up to
about 6' (IIRC), due to the acceleration of gravity, and maybe will
have some capacity leftover to absorb some deceleration from any
frontal impact. All in all, your higher brain tissue may be left intact
while the rest of your body (including brain stem)gets beat to hell. I
would say that it will do a lot of good in a typical collision, but it
will not always be enough.


That's nice, I'll be sure and go through the windshield the next time a car
hits me, and I'll make sure not to get launched more than 6' into the air.

Stop taking it so personally and you might realize that I was trying to
explain what protection a helmet does provide, and what it doesn't.

If you think about it, your head is only about 4' from the ground when
you're on a bike. No matter how hard you are hit, your head will only
accelerate toward the ground from that height unless the angle of
collision somehow catapults you higher or into the ground.

So, in fact, contrary to your original statement, a helmet provides
significant protection to the brain in most types of collisions, but it
is the only part of the body that is protected to any degree.

If you don't want to use a helmet, fine, but at least don't go around
spreading nonsense.

Alex Rodriguez wrote:

ANSI or SNELL sticker is important.

Alex, I see this all the time (especially on ride event applications).
Guess what? If your helmet is less than 10 years old, it is NOT ANSI
certified. And it's there's only a very slim chance it's SNELL
certified.

Most helmets sold in the US are CPSC certified.

See:
http://www.bhsi.org/standard.htm

Art Harris

wrote:


If you think about it, your head is only about 4' from the ground when
you're on a bike.

Um, you might want to measure that.

No matter how hard you are hit, your head will only
accelerate toward the ground from that height unless the angle of
collision somehow catapults you higher or into the ground.

So, in fact, contrary to your original statement, a helmet provides
significant protection to the brain in most types of collisions, but it
is the only part of the body that is protected to any degree.

You seem to be assuming the "collision" will involve only a rider
toppling to the flat ground. Things are a bit more complicated.

First, very few topples to flat ground are serious problems. People
have been falling off bikes ever since bikes were invented. Those
people land on their head only in vanishingly rare cases. IOW, those
incidents aren't worth worrying about. (Contrary to modern belief,
people actually survived riding bikes in pre-helmet days!)

The events that are used to promote helmets are those that cause
permanent injury or death. The vast majority of those events involve
collisions with moving motor vehicles. In those cases, it's very
common for the impact speed to be much higher than the 14 mph - that
is, to greatly exceed the rated capacity of a bike helmet.

Perhaps you're imagining that the typical car-bike collision involves
simply knocking the cyclist to the ground. But AFAIK, that's never
been demonstrated to be the case. And even if it were, there's no
reason to think the head's impact with the ground would be at only 14
mph. Crashes like that are very chaotic, in the mathematical sense.
IOW, the motion of the cyclist's body would be extremely random. It's
entirely possible that the cyclist would be energetically "flipped" and
have his head impact the ground at higher speed, even if it managed to
miss impacting the car itself.

Try momentarily balancing a 6" wooden pencil on it's point, and hit it
with a horizontal impact about 1" above the table. You'll see the
eraser hit the table much faster than if the pencil just toppled. The
same motion (or a chaotic variation of it) is possible with a cyclist
hit by a car.

Whatever the details of the mechanics, it's good to keep one fact
firmly in mind: Helmets are NOT working as claimed. Head injury rates
are not being improved by helmet wearing, and indeed seem to be
worsening somewhat. There may be other factors involved, but one
likely one is that a helmet certified for only a 14 mph impact is -
guess what? - actually good only for a 14 mph impact!

If you don't want to use a helmet, fine, but at least don't go around
spreading nonsense.

Ditto if you want to use a helmet.

- Frank Krygowski

wrote:
wrote:


If you think about it, your head is only about 4' from the ground when
you're on a bike.

Um, you might want to measure that.

Um, I would, except I'm nowhere near my bicycle. Is it less than 6'?
The answer is yes, so it doesn't matter.

No matter how hard you are hit, your head will only
accelerate toward the ground from that height unless the angle of
collision somehow catapults you higher or into the ground.

So, in fact, contrary to your original statement, a helmet provides
significant protection to the brain in most types of collisions, but it
is the only part of the body that is protected to any degree.

You seem to be assuming the "collision" will involve only a rider
toppling to the flat ground. Things are a bit more complicated.

Um, no, hence the statement "unless the angle of collision somehow
catapults you higher or into the ground". Um, you seem to be making the
mistake of thinking that the acceleration of gravity is somehow more
when you are falling toward the ground as a result of being hit from
the side.

First, very few topples to flat ground are serious problems. People
have been falling off bikes ever since bikes were invented. Those
people land on their head only in vanishingly rare cases. IOW, those
incidents aren't worth worrying about. (Contrary to modern belief,
people actually survived riding bikes in pre-helmet days!)

All irrelevant since I wasn't talking about "topples", but bull****,
nevertheless. If you don't get an arm out to break your fall, you very
likely will bounce your head off the pavement, and the fall from the
height your head is at at the time of the crash is sufficient,
physiologically speaking, to bash your brains out.

The events that are used to promote helmets are those that cause
permanent injury or death. The vast majority of those events involve
collisions with moving motor vehicles. In those cases, it's very
common for the impact speed to be much higher than the 14 mph - that
is, to greatly exceed the rated capacity of a bike helmet.

But your head still accelerates to the ground at the acceleration of
gravity.

Perhaps you're imagining that the typical car-bike collision involves
simply knocking the cyclist to the ground. But AFAIK, that's never
been demonstrated to be the case.

Nope, I'm assuming that the typical collision involves getting knocked
sideways hard as hell but falling toward the ground at the acceleration
of gravity.

And even if it were, there's no
reason to think the head's impact with the ground would be at only 14
mph. Crashes like that are very chaotic, in the mathematical sense.

The only way a car will knock you into the ground at 14 mph is if it is
going 14 mph in the direction of the ground when it falls on top of
you.

Crashes like that are very chaotic, in the mathematical sense.

Again, recalling my statement "unless the angle of collision somehow
catapults you higher or into the ground", which added to the case of a
perfect sideways hit covers _all_ the possibilities of the maximum
acceleration toward the ground in that chaos.

IOW, the motion of the cyclist's body would be extremely random. It's
entirely possible that the cyclist would be energetically "flipped" and
have his head impact the ground at higher speed, even if it managed to
miss impacting the car itself.

Thank you. That would be covered by "catapults".

Whatever the details of the mechanics, it's good to keep one fact
firmly in mind: Helmets are NOT working as claimed. Head injury rates
are not being improved by helmet wearing, and indeed seem to be
worsening somewhat.

Bull****. Cite needed.

There may be other factors involved, but one
likely one is that a helmet certified for only a 14 mph impact is -
guess what? - actually good only for a 14 mph impact!

It protects the head from an impact of 14mph. That says nothing about
the speed of the cyclist or a car in a car/bicycle collision. It is
also stupid to suggest that no one ever has a bicycle slide out from
under them with a resulting bounce of the head off of the pavement, in
which case the forward speed of the bicycle is completely beside the
point and the impact will usually be very much like simplest case- the
acceleration of the head from the height it was before the crash to the
ground.

If you don't want to use a helmet, fine, but at least don't go around
spreading nonsense.

wrote:

You seem to be assuming the "collision" will involve only a rider
toppling to the flat ground. Things are a bit more complicated.

First, very few topples to flat ground are serious problems. People
have been falling off bikes ever since bikes were invented. Those
people land on their head only in vanishingly rare cases. IOW, those
incidents aren't worth worrying about. (Contrary to modern belief,
people actually survived riding bikes in pre-helmet days!)

The events that are used to promote helmets are those that cause
permanent injury or death. The vast majority of those events involve
collisions with moving motor vehicles. In those cases, it's very
common for the impact speed to be much higher than the 14 mph - that
is, to greatly exceed the rated capacity of a bike helmet.

...

I have seen *at least* a crash where the helmet splitted in two, thus
absorbing energy that would have ended in the rider's head.
The rider had no injury, without helmet he would (if you don't believe
it, take an helmet, hit the road with it so hard that it gets seriously
damaged. Then hit your head against the road with about the same force,
this will convince you).

You say "the vast majority of those events", "in general", etc.
If in a crash every N the helmet can save my life, then I wear it,
period - no matter how big N is.

If you don't want to wear it because it doesn't protect you in every
kind of possible crash, that's your choice, but don't suggest it to
other people.

Francesco

On 7 Jul 2005 12:49:35 -0700,
wrote:



wrote:
wrote:


If you think about it, your head is only about 4' from the ground when
you're on a bike.

Um, you might want to measure that.

Um, I would, except I'm nowhere near my bicycle. Is it less than 6'?
The answer is yes, so it doesn't matter.

No matter how hard you are hit, your head will only
accelerate toward the ground from that height unless the angle of
collision somehow catapults you higher or into the ground.

So, in fact, contrary to your original statement, a helmet provides
significant protection to the brain in most types of collisions, but it
is the only part of the body that is protected to any degree.

You seem to be assuming the "collision" will involve only a rider
toppling to the flat ground. Things are a bit more complicated.

Um, no, hence the statement "unless the angle of collision somehow
catapults you higher or into the ground". Um, you seem to be making the
mistake of thinking that the acceleration of gravity is somehow more
when you are falling toward the ground as a result of being hit from
the side.

First, very few topples to flat ground are serious problems. People
have been falling off bikes ever since bikes were invented. Those
people land on their head only in vanishingly rare cases. IOW, those
incidents aren't worth worrying about. (Contrary to modern belief,
people actually survived riding bikes in pre-helmet days!)

All irrelevant since I wasn't talking about "topples", but bull****,
nevertheless. If you don't get an arm out to break your fall, you very
likely will bounce your head off the pavement, and the fall from the
height your head is at at the time of the crash is sufficient,
physiologically speaking, to bash your brains out.

The events that are used to promote helmets are those that cause
permanent injury or death. The vast majority of those events involve
collisions with moving motor vehicles. In those cases, it's very
common for the impact speed to be much higher than the 14 mph - that
is, to greatly exceed the rated capacity of a bike helmet.

But your head still accelerates to the ground at the acceleration of
gravity.

Perhaps you're imagining that the typical car-bike collision involves
simply knocking the cyclist to the ground. But AFAIK, that's never
been demonstrated to be the case.

Nope, I'm assuming that the typical collision involves getting knocked
sideways hard as hell but falling toward the ground at the acceleration
of gravity.

And even if it were, there's no
reason to think the head's impact with the ground would be at only 14
mph. Crashes like that are very chaotic, in the mathematical sense.

The only way a car will knock you into the ground at 14 mph is if it is
going 14 mph in the direction of the ground when it falls on top of
you.

Crashes like that are very chaotic, in the mathematical sense.

Again, recalling my statement "unless the angle of collision somehow
catapults you higher or into the ground", which added to the case of a
perfect sideways hit covers _all_ the possibilities of the maximum
acceleration toward the ground in that chaos.

IOW, the motion of the cyclist's body would be extremely random. It's
entirely possible that the cyclist would be energetically "flipped" and
have his head impact the ground at higher speed, even if it managed to
miss impacting the car itself.

Thank you. That would be covered by "catapults".

Whatever the details of the mechanics, it's good to keep one fact
firmly in mind: Helmets are NOT working as claimed. Head injury rates
are not being improved by helmet wearing, and indeed seem to be
worsening somewhat.

Bull****. Cite needed.

There may be other factors involved, but one
likely one is that a helmet certified for only a 14 mph impact is -
guess what? - actually good only for a 14 mph impact!

It protects the head from an impact of 14mph. That says nothing about
the speed of the cyclist or a car in a car/bicycle collision. It is
also stupid to suggest that no one ever has a bicycle slide out from
under them with a resulting bounce of the head off of the pavement, in
which case the forward speed of the bicycle is completely beside the
point and the impact will usually be very much like simplest case- the
acceleration of the head from the height it was before the crash to the
ground.

If you don't want to use a helmet, fine, but at least don't go around
spreading nonsense.

Dear SSTW,

Below is an idealized rider on a bicycle, travelling
sideways after being accelerated to 20 mph by a careless
driver and about to hit a 6-inch-high curb:

H ----- 20 mph @ 60 inches above ground
|
|
|
CM ---- 20 mph @ 36 inches above ground
|
|
|
| _____________________________________
|_| 6-inch curb

The collision with the curb is likely to spin the rider's
head H around his center of mass CM at an impressive rate. I
think that this was the point of Frank's example of knocking
the bottom of an upright pencil sideways--the rotation
around the center of mass can be much faster than the
acceleration due to gravity.

For a more dramatic demonstration, stand a yardstick upright
and give its base a sideways kick with your foot--the top
end of the yardstick slams to the floor much faster than it
would if it had simply toppled sideways.

For fun, someone might calculate the speed at impact of the
head of a 5-foot-high "yardstick" under these three
conditions:

The first calculator on the page below will solve the first
example if you put 5 into the foot-field and click outside:

http://hyperphysics.phy-astr.gsu.edu...aj.html#tracon

12.2 mph horizontal 5-foot stick dropped from 60 inches
(no wind drag) (17.9 fps = 12.2 mph)

xx.x mph vertical 5-foot stick toppling sideways, base
remains in place, (no wind drag, falling chimney)

xx.x mph vertical 5-foot-stick whose idealized bottom is
struck by a 20 mph massive object (no wind)

A bike and rider, of course, are weighted toward the head
end, so the analogy is crude, but the idea of rotation speed
increasing fall speed seems quite plausible.

Another example would be a 60-inch-high bicyclist's head
rotating sideways down onto the hood of a 36-inch-high car
hood after being struck by the 18-inch-high car bumper at 20
mph:

Head at 60 inches ____________________
| / |
| / |
| ________/car hood at 36 inches |
| / |
| / |
| _/ ___bumper at 18 inches |
| \ ___ ___ |
| \____/ \---------------------/ \-
|________\___/_____________________\___/____


As Frank pointed out, the calculations are rather tricky,
since all sorts of things happen that a crude ASCII diagram
can't cover--the driver above might jam his brakes on just
as he strikes the bike, so that the rider is sent flying
sideways, but rotates downward and hits the ground, not the
hood of the car, because the car begins slowing violently
just after it hits the rider.

Carl Fogel

Do you wear a helmet in your car? No? Why not? You're more likely to
incur a head injury in your car than on your bike. Why not protect
yourself? How about wearing a kevlar vest? No? Not worried about
getting shot? The risk is small, but it's there, nonetheless. Have
you got those little sticky things on the floor of your tub/shower?
No? Egad! Talk about a risk taker! I hope you have plenty of
insurance.