Helmets
yk
expensive helmets safer or more aero-dynamically designed ? What to look
for besides fit and color ? TIA
Art Harris
> 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 ?
Fit is very important. Look for a helmet that comes in at least three
different sizes, not one size fits all (like some cheap helmets). Also
look for a helmet that offers enough adjustments to get the helmet
properly positioned and snug. Finally, get a helmet that fits the shape
of your head. It's best to buy at a bike shop where you can try several
on, and get them adjusted properly.
Price is often driven by style and is not necessarily an indication of
protection.
See:
http://www.bhsi.org
for lots more information.
Art Harris
mark
"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
>
of holes that will still offer nominal head protection is trickier and
presumably more expensive than molding a solid chunk of polystyrene foam
into a head shape. Really cheap helmets come in one size only, with maybe
some pads to shim them up so they don't rattle around on your head. Better
helmets may have a sturdier retention system. Better helmets come in a wider
range of sizes. It's worth noting that a closely fitting helmet is necessary
for optimum protection, so the one size fits all cheapos *really* only work
for the larger heads.
Also worth noting is that the higher priced helmets are designed to barely
pass impact tests while being as light and well ventilated as possible. The
extra time it takes to design a helmet this way is probably reflected in the
price. Cheap helmets are designed to pass impact tests by a comfortable
margin without too much R&D time being spent making them ultra-lightweight
or well ventilated.
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.
--
mark
SocSecTr...@earthlink.net
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.
Also, don't forget that in a collision where the bicyclist is hit by a
car from behind the closing speed may well be in that 12-15mph range
after the idiot in the car finally steps on the brakes.
C
Cheapo helmets usually come in only one size and are hard to fit properly
if you have a smaller or larger than average head. Saftey is about the
same at all price ranges, but only if you can get a good fit. Comfort
is also related to fit. More expensive helmets tend to have better
ventilation for hot weather use. Cheapo helmets used to be much heavier,
but they are getting pretty lightweight these days.
mark
<SocSecTr...@earthlink.net> 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.
> Also, don't forget that in a collision where the bicyclist is hit by a
> car from behind the closing speed may well be in that 12-15mph range
> after the idiot in the car finally steps on the brakes.
>
I won't forget that. Am I missing something, or is a cyclist hit from behind
by a car going to get accelerated rather abruptly to the car's speed at the
time of impact, regardless of closing speed?
--
mark
Doug Huffman
<SocSecTr...@earthlink.net> wrote in message
news:1120664276.8...@g49g2000cwa.googlegroups.com...
clu...@lycos.com
Fit is high on the list. If you don't like it, you won't wear it, it
won't be there when, not if, you need it. Christopher Reeves became a
paraplegic from a fall from a horse. Yes he was higher but dirt is
softer than asphalt.
Ventillation is up there also.
Wear your helmet, smiling beats drooling,
Wes
>
--
Reply to:
Whiskey Echo Sierra Sierra AT Alpha Charlie Echo Golf Romeo Oscar Paul dot Charlie Charlie
Lycos address is a spam trap.
Zog The Undeniable
The expensive ones have more marketing effort put into them. They're
also lighter and better ventilated. Having said that, the difference
between this year's $200 helmet and last year's $100 helmet is neither
here nor there.
carl...@comcast.net
>"yk" <y...@hotmail.com> 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
>
>Fit is high on the list. If you don't like it, you won't wear it, it
>won't be there when, not if, you need it. Christopher Reeves became a
>paraplegic from a fall from a horse. Yes he was higher but dirt is
>softer than asphalt.
>
>Ventillation is up there also.
>
>Wear your helmet, smiling beats drooling,
>
>Wes
Dear Wes,
Without arguing about the merits of helmets . . .
Reeves suffered a broken neck, not a head injury.
He became a quadriplegic, not a paraplegic.
And he was wearing a helmet.
Carl Fogel
Benjamin Lewis
> "yk" <y...@hotmail.com> 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
>
> Fit is high on the list. If you don't like it, you won't wear it, it
> won't be there when, not if, you need it. Christopher Reeves became a
> paraplegic from a fall from a horse. Yes he was higher but dirt is
> softer than asphalt.
Assuming he wasn't wearing a helmet when he was injured (I have no idea),
how do you suppose a helmet would have prevented his spinal cord injury?
--
Benjamin Lewis
"Love is a snowmobile racing across the tundra and then suddenly it flips
over, pinning you underneath. At night, the ice weasels come."
--Matt Groening
E Willson
defined by the consumer protection agency. I believe the standard is Z90
(IIRC), and the helmet liner is marked accordingly. Moreover there used
to be a more stringent standard used by the SNELL institute. Helmets
with SNELL ratings used to be more safe (for penetration) than helmets
that just met the Consumer protection standards. I am not sure if SNELL
still exists, but I would suggest that you look for a helmet that has a
SNELL rating if you are looking for the ultimate in safety. I would
appreciate comments from anyone who knows the current situation, because
I am not sure of it.
HTH,
Ernie
Eric Hill
I grazed google past this topic about a month or so ago, and I was left
with the impression that SNELL does not exist for bicycle helmets
(anymore). It's pretty much a motorcycle helmet thing.
To the original poster, since all helmets in the US pass the same test,
the only real difference is ventilation and appearance.
-eric
Fritz M
> Am I missing something, or is a cyclist hit from behind
> by a car going to get accelerated rather abruptly to the car's speed at the
> time of impact, regardless of closing speed?
40 mph car rear-ending a 20 mph cyclist has a closing speed of 20 mph.
40 mph car hitting the front of a 20 mph cyclist hits with closing
speed of 60 mph. I think I'd rather be accelerated 20 mph rather than
60 mph.
RFM
Mike Kelly
when you are riding in the same direction at 20 mph, is like standing still
and being hit by a 20 mph car. Yes, you will be accerelated plus 20 mph in
either case but at a much slower rate.
The other case you get hit by a 60 mph car, and then accelerated to 40 mph.
BIG difference.
"Fritz M" <nos...@masoner.net> wrote in message
news:1120689309....@g49g2000cwa.googlegroups.com...
frkr...@yahoo.com
Eric Hill wrote:
> E Willson wrote:
> > I am not sure if SNELL
> > still exists, but I would suggest that you look for a helmet that has a
> > SNELL rating if you are looking for the ultimate in safety. I would
> > appreciate comments from anyone who knows the current situation, because
> > I am not sure of it.
The Snell rating still exists, in that any manufacturer who has a
helmet that meets Snell requirements, and who wants to pay to have it
certified by Snell, can do so. However, manufacturers seem to have
decided en masse that it's not worth paying for that certification.
The US law requires CPSC certification, and they're happy enough with
that.
And I wouldn't call Snell " the ultimate in safety." Snell is just
slightly more stringent than CPSC. (CPSC requires a 2 meter drop;
Snell a 2.2 meter drop.) The impact speeds are very nearly equal.
Neither test has the mass of a body attached to the headform. IOW, the
helmets are certified to protect a decapitated head hitting something
at 14 mph. Hitting at 16 mph is beyond what they're designed for.
Hitting with your body still attached to your head is also likely to
overpower the helmet.
Incidentally, I think this is why Snell certification isn't popular.
If a manufacturer claimed "Ours is more protective! We're _Snell_
certified!!" some consumers would ask "What's the difference?"
The answer would have to include a description of the laughably low
certification; and once that was given, the jig would be up. Consumers
and legislators would realize how worthless the things are.
>
> I grazed google past this topic about a month or so ago, and I was left
> with the impression that SNELL does not exist for bicycle helmets
> (anymore). It's pretty much a motorcycle helmet thing.
>
> To the original poster, since all helmets in the US pass the same test,
> the only real difference is ventilation and appearance.
Not so. As others have pointed out, more expensive helmets tend to be
lighter and have better ventilation. That makes them generally less
uncomfortable to wear. But it also makes them less protective. Much
of the expense in a pricey helmet comes from the extensive computer
modeling and testing to get them to be as light and "holey" as
possible, but JUST BARELY pass the standards test.
The cheaper ones have more margin of protection. They leave in more
styrofoam and cut fewer holes so they can be sure it will pass the test
without re-designing.
So when you pay more, you get better ventilation, but you get less
protection. You also tend to get something that looks more like a
psychedelic squid wrapped around your head. But there's no accounting
for fashion!
- Frank Krygowski
E Willson
To continue the thread
Thanks for the several replys
As you say , the SNELL rating is basically a motorcycle thing which has
been applied to bicycle gear. Based on your comments I believe that the
impact performance of a CPSC helmet and a SNELL certified helmet is
about the same. IIRC the SNELL certification came about because a
motorcycle rider named Snell was killed by a sharp metal object that
penetrated his helmet, killing him. The helmet he was wearing was
adequate for impact resistance. As I remember it, the original intention
of the SNELL rating was to improve the penetration performance of
helmets. Based on what has been said here, I'd have to assume that if a
helmet carried a SNELL certification it would be as good (or better) in
impact as a CPSC rated helmet, and it would be more protective against
penetation type objects. Does this sound correct?
Comments?
Regards,
Ernie Willson
frkr...@yahoo.com
E Willson wrote:
> >
>
> To continue the thread
>
> Thanks for the several replys
>
> As you say , the SNELL rating is basically a motorcycle thing which has
> been applied to bicycle gear. Based on your comments I believe that the
> impact performance of a CPSC helmet and a SNELL certified helmet is
> about the same. IIRC the SNELL certification came about because a
> motorcycle rider named Snell was killed by a sharp metal object that
> penetrated his helmet, killing him. The helmet he was wearing was
> adequate for impact resistance. As I remember it, the original intention
> of the SNELL rating was to improve the penetration performance of
> helmets. Based on what has been said here, I'd have to assume that if a
> helmet carried a SNELL certification it would be as good (or better) in
> impact as a CPSC rated helmet, and it would be more protective against
> penetation type objects. Does this sound correct?
Well, not really. Snell was an auto racer, and the fatality didn't
involve penetration, AFAIK.
>From the Snell Memorial Foundation website:
"William "Pete" Snell died in 1956 because his then state of the art
helmet lacked the protective capacity to see him through what was
termed a survivable accident. Pete Snell's helmet represented an
intuitive solution for impact protection. After Snell's death, Dr.
George Snively demonstrated that human intuition is not a reliable
guide to understanding crash impact, particularly in the millisecond
time domains in which crash impact occurs.
Snively discovered that most injuries of helmeted people occurred
because the liner had reached full compression, that is, the helmet had
used up all its protective capacity, before the impact was over.
Helmets were too thin and far too soft.
Snively studied auto racing accidents and compared injury versus helmet
compression in real world impacts to peak acceleration versus helmet
compression in laboratory tests. He concluded that young healthy men
could expect to withstand head impacts corresponding to lab tests
incurring from 400 to 600 G's. Since tolerances vary among people and
are likely to vary with age, Snively set Snell test criteria at about
300 G's.
Snively then set up the first of the Snell helmet standards..."
Also from that website:
" William "Pete" Snell was an amateur auto racer. He died needlessly in
a racing event in 1956 when his then state-of- the-art helmet utterly
failed to protect him."
What's interesting to me is that there have been many deaths of
helmeted cyclists, including cyclists wearing Snell-certified helmets!
One could say that each of these "died needlessly when his then
state-of-the-art helmet utterly failed to protect him."
IOW, one could use the same logic to call for a new Memorial
Foundation!
Seriously, the Snell Memorial Foundation has certainly improved helmet
science. I just wish they'd drop the rabid promotion of helmets for
activities that are already more than reasonably safe. Like cycling,
of course.
- Frank Krygowski
Art Harris
> I was left with the impression that SNELL does not exist for bicycle helmets
Not quite. See the link below for a discussion of the various
standards.
http://www.bhsi.org/standard.htm
Art Harris
clu...@lycos.com
>Dear Wes,
>
>Without arguing about the merits of helmets . . .
>
>Reeves suffered a broken neck, not a head injury.
>
>He became a quadriplegic, not a paraplegic.
>
>And he was wearing a helmet.
>
>Carl Fogel
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.
There are times when being thrown from a car beats riding it all the
way. Odds favor seatbelts.
I belive in self determination. Darwin isn't operating all that well
in our society.
Qui si parla Campagnolo
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...
Doug Huffman
statistical data is corrupt but
The conspiracy of ignorance masquerades as common sense.
<clu...@lycos.com> wrote in message
news:11cqaio...@news.supernews.com...
Alex Rodriguez
>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
SocSecTr...@earthlink.net
mark wrote:
> <SocSecTr...@earthlink.net> 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.
Art Harris
> 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
frkr...@yahoo.com
SocSecTr...@earthlink.net 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
SocSecTr...@earthlink.net
frkr...@yahoo.com wrote:
> SocSecTr...@earthlink.net 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 bullshit,
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.
Bullshit. 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.
Francesco Devittori
>
> 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
carl...@comcast.net
wrote:
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/hbase/traj.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
Scott
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.
mark
<SocSecTr...@earthlink.net> wrote .
>
> 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.
>
Actually I do use a helmet, and I have used one quite consistently since
about 1979. As I've learned more about helmets, I've become increasingly
skeptical about their value, except in very limited circumstances. Looking
at the changes in helmet design since I bought my first Bell Biker in 1979,
it's pretty apparent to me that today's helmets offer distinctly less
protection than the hardshell helmets of the '70s and '80s.
You seem to be taking a very oversimplified view of what happens in a car /
bicycle collision. As a number of posters have pointed out, it's a little
more complex than car hits bike, bike falls down. As Carl Fogel points out,
a cyclist hit by a car can easily assume the characteristics of an object
accelerated about an axis, and the cyclist's head can get slammed into the
ground with far more force than would be the case if the cyclist just fell
over.
A number of the regulars on uk.rec.cycling have done some research on
bicycle helmets, and the findings are interesting. What impresses me the
most about this research is that the countries that have enacted laws
requiring cyclists to wear helmets have not seen a reduction in head injury
rates, they've just seen a dramatic reduction in the number of people
bicycling. Another interesting point is that the countries with the lowest
head injury rates for cyclists are the countries with the lowest rates of he
lmet usage by cyclists. Check this website: www.cyclehelmets.org and see
what they have to say.
--
mark
carl...@comcast.net
wrote:
For those interested in equations, the familiar
falling-chimney scenario mimics a bicyclist simply toppling
sideways.
The equations are somewhat daunting, but lead to the usual
conclusion that the force of gravity can indeed accelerate a
fairly simple falling object at a rate greater than 1 G by
leverage:
http://hep.brown.edu/users/partridge/ph5/Lecture20.pdf
See page 12 of 20 of the pdf above.
Carl Fogel
carl...@comcast.net
wrote:
The corollary (probably not exactly the right word) is the
end of the horizontal plank supported at one end by a table
and released, which may be easier to follow and is closer to
the bicyclist whose lower rim slams sideways into a curb:
http://www.physicsforums.com/archive/t-41611_Surprising_physics.html
Search down in the thread from the first post for "chimney"
and you'll find the chimney scenario mentioned.
Carl Fogel
frkr...@yahoo.com
SocSecTr...@earthlink.net wrote:
> frkr...@yahoo.com wrote:
> > SocSecTr...@earthlink.net 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.
:-) So a 50% error doesn't matter? You're being awfully charitable
toward yourself!
I just measured myself on the bike. Turns out that my head is at the
same height (plus/minus less than an inch) whether I'm standing or on
the bike. Obviously, there would be slight differences depending on
bike geometry - and big differences for a recumbent - but I think it's
safe to say 4 feet is usually _way_ off!
>
> 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.
Nope. I'm thinking nothing of the kind. I thought my pencil
illustration made that clear.
>
> > 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 bullshit,
> 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.
Good grief, such hysteria! Arm or no arm, falling off a bike does not
"very likely" mean you'll bash your brains out! Serious head injuries
were never "very likely" no matter what. The link between head
injuries and bikes was forged only AFTER Bell had a product they wanted
to sell.
If head injuries were at all common, do you seriously think Dr. Paul
Dudley White would have had the leader of the free world, Eisenhower,
bicycling for exercise? And doing so without a foam hat?
> > 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".
I don't think you grasp the degree of chaos involved. Giving lip
service to the word "catapult" does not mean that a 14 mph
certification must cover all - or almost all - crashes.
As an illustration: In one of our university labs, we have a double
pendulum chaos demonstrator. Two metal bars on good bearings; one
hangs from the bottom of the other. The top hangs from a fixed
support. Each pivot is capable of 360 degree rotation.
The motion is absolutely unpredictable. Most interestingly, if you
hold them off to the side then release, they don't just swing smoothly.
One may suddenly jerk, spin or jump about at high speed. If you were
to stick your hand in at that moment, you'd certainly be hurt. And you
cannot mathematically predict when "that moment" will occur.
The human femur and tibia are similar, with the added spice that they
can move about other axes as well, and they are influenced by large
muscles that can jerk reflexively. Splice two of those onto a
twistable trunk, add two similar arms and a flexible neck, and there is
absolutely no way to calculate what will happen in a collision with a
car. Certainly, there is no justification for thinking a helmet
certified only to protect a decapitated headform at only 14 mph will
suffice for any large percentage of the impacts.
>
> > 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.
>
> Bullshit. Cite needed.
"A Bicycling Mystery: Head Injuries Piling Up." [Despite greatly
increased helmet use, that is.] New York Times, July 29, 2001.
http://www.cyclehelmets.org/1028.html
There are similar reports from other countries. Australia bragged
about the drop in head injuries from its strictly enforced, all ages
helmet laws - but then people pointed out that cycling had dropped
_more_ than the head injuries, leaving more head injuries per remaining
rider.
>
> > 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.
Hmm. Well, one of the most common serious car-bike collisions is the
left hook: car turns left into cyclist. Typical closing speed perhaps
35 mph. Do you think the impact with the cyclist will usually be
below 14 mph?
> 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.
Nobody suggested that "slide out" doesn't happen. In fact, I take
great comfort in the fact that it's _always_ happened, yet it's never
caused any significant number of serious head injuries.
Cyclists make up less than 1% of the head injury fatalities in America.
This has _always_ been the case. The "bashing of brains" that you
fear was never an issue UNTIL Bell had a new product that needed to be
sold.
And it's certainly being sold! We now have an entire generation of
people who have been taught to link "bicycle" and "serious head injury"
without ever examining the data. We now have avid cyclists who mock
anyone who chooses to ride without the hat they prefer.
> If you don't want to use a helmet, fine, but at least don't go around
> spreading nonsense.
I will back up whatever I say with data and reason. I don't spread
nonsense.
Here's some reading for you, complete with citations.
http://www.bicyclinglife.com/SafetySkills/SafetyQuiz.htm
Bicycling is NOT very dangerous. It does us no good to pretend it is.
- Frank Krygowski
frkr...@yahoo.com
Francesco Devittori wrote:
>
>
> 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).
And I have seen a crash where a person was hit by a car hard enough
that he destroyed the grill, badly dented the hood, smashed the
windshield, was tossed in the air higher than the car, landed on his
head on the road, and was unhurt but for a scratch over the right ear.
If he were wearing a helmet, you would certainly claim it saved his
life. But he had no helmet.
This is no exaggeration. I can post the entire story, if you like.
But it proved to me that any one crash tells you nothing at all.
>
> 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.
But let me guess: Only when you're on a bicycle, right?
Cycling causes less than 1% of America's head injury fatalities. And
its risk per hour of HI fatality is about the same as motoring or
walking near traffic.
So why not apply your same level of protection to the other situations
that cause 99% of the problem? Why take your helmet off at all? Or
alternately, why the effort to make only bicycling look so dangerous?
>
> 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.
:-) I suggest you strap your helmet on immediately! Why, you may trip
when you get up from your computer!
And don't _you_ be so irresponsible as to say a computer helmet isn't
needed! Why, if only ONE life can be saved... <wring hands here>
;-)
- Frank Krygowski
Jeff Starr
wrote:
That's brilliant, we've never heard that arguement before. Tell me,
did you think that up, all by yourself? Or did Frank help you with
that one?
Well, anyway, you've convinced me, now I just have to decide, do I
discard the bike helmets, I own three? Or, do I go out and buy a car
specific helmet and a bullet proof vest? I already have the
tub/shower taken care of.
Hey, thanks for all your valuable help.
Life is Good!
Jeff
David Damerell
>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
When did you repeat the experiment with a control head?
>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.
Really? Presumably if you come to the UK you will wear heavy boots at all
times to protect against adder bites - there's only been one fatal one in
the last few decades, but no matter how big N is, it's worth it, right?
--
David Damerell <dame...@chiark.greenend.org.uk> Kill the tomato!
Today is Second Friday, Presuary.
Francesco Devittori
> Quoting Francesco Devittori <frenkatfrenkdtcm>:
>
>>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
>
>
> When did you repeat the experiment with a control head?
>
>
>>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.
>
>
> Really? Presumably if you come to the UK you will wear heavy boots at all
> times to protect against adder bites - there's only been one fatal one in
> the last few decades, but no matter how big N is, it's worth it, right?
Except that in this case N is bigger than one in a few decades. But
again, nobody forces you to wear an helmet.
SocSecTr...@earthlink.net
frkr...@yahoo.com wrote:
> SocSecTr...@earthlink.net wrote:
> > frkr...@yahoo.com wrote:
> > > SocSecTr...@earthlink.net 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.
>
> :-) So a 50% error doesn't matter? You're being awfully charitable
> toward yourself!
4' ot 6', they're both within the design limits for which a helmet is
designed to protect a head during a fall. Arguing the distance between
your head and the pavement when you're sitting on a bicycle is
completely irrelevant UNLESS YOU ARE GOING TO ALSO MAKE THE POINT THAT
THE HEIGHT IS OUTSIDE THE LIMIT FOR WHICH THE HELMET IS DESIGNED TO
PROVIDE PROTECTION!
> Arm or no arm, falling off a bike does not
> "very likely" mean you'll bash your brains out! Serious head injuries
> were never "very likely" no matter what.
Wrong. A mere "topple" on from a bicycle even standing still will
accelerate your head to a high enough speed that you can sustain a
fatal head injury. It's that simple.
> > Thank you. That would be covered by "catapults".
>
> I don't think you grasp the degree of chaos involved. Giving lip
> service to the word "catapult" does not mean that a 14 mph
> certification must cover all - or almost all - crashes.
I don't think you grasp what I was saying, which is actually the
opposite of how you interpreted it. The catapult is one reason why a
14mph certification does not provide protection in somes types of
crashing. Why are you arguing with me about something I agree with you
on?
> Certainly, there is no justification for thinking a helmet
> certified only to protect a decapitated headform at only 14 mph will
> suffice for any large percentage of the impacts.
I said something along the lines of, "it will protect your upper brain
tissue while the rest of your body (including brain stem) gets beat to
hell". Again, arguing with me where I agreed with you three posts back.
> "A Bicycling Mystery: Head Injuries Piling Up." [Despite greatly
> increased helmet use, that is.] New York Times, July 29, 2001.
> http://www.cyclehelmets.org/1028.html
It says, "No one is very sure, but safety experts stress that while
helmets do not prevent accidents from happening, they are extremely
effective at reducing the severity of head injuries when they do occur.
Almost no one suggests that riders should stop wearing helmets, which
researchers have found can reduce the severity of brain injuries by as
much as 88 percent."
"'Bicycle helmet technology is the best we have for protecting the
brain,' Dr. Kelly said. 'The helmets serve the function of an air
bag.'"
"But the most effective way to reduce severe head injuries may be to
decrease the number of accidents in the first place."
Nothing in that article suggests that helments don't provide protection
from head injuries. What it does ask is why are head injuries occurring
more frequently in the first place. One of the hypotheses is that
helmets make the rider feel more secure and therefore take more
chances. Well, that's a point: helmets may protect your brain, but they
won't make it any smarter than it was before you put the helmet on.
> Hmm. Well, one of the most common serious car-bike collisions is the
> left hook: car turns left into cyclist. Typical closing speed perhaps
> 35 mph. Do you think the impact with the cyclist will usually be
> below 14 mph?
No, and if your head impacts the car, you will be in trouble. But, if
what happens is that you get knocked away from the car, when you hit
the ground the speed vector in the direction of the ground will be <
14mph, and your head will be protected while the "rest of your body is
beat to hell".
> Nobody suggested that "slide out" doesn't happen. In fact, I take
> great comfort in the fact that it's _always_ happened, yet it's never
> caused any significant number of serious head injuries.
Brain injuries are about the only way to die from a "slide out".
> Cyclists make up less than 1% of the head injury fatalities in America.
That is a meaningless statistic, so ridiculous that I am not going to
spend the time picking it apart in the many ways it could be done.
> This has _always_ been the case. The "bashing of brains" that you
> fear was never an issue UNTIL Bell had a new product that needed to be
> sold.
My memory of it was that it was recognized that the leather hairnet did
not provide any significant protection, and people wanted more. I knew
racers that had had concussions, they were scared, and they wanted real
protection.
> And it's certainly being sold! We now have an entire generation of
> people who have been taught to link "bicycle" and "serious head injury"
> without ever examining the data. We now have avid cyclists who mock
> anyone who chooses to ride without the hat they prefer.
If you don't personally understand the relationship between head injury
and bicycling, you either don't ride enough, or you and your
acquaintances have been very, very lucky.
> > If you don't want to use a helmet, fine, but at least don't go around
> > spreading nonsense.
>
> I will back up whatever I say with data and reason. I don't spread
> nonsense.
Hardly. You used your cite above to suggest that helmets themselves are
causing head injuries when it actually states that they DO reduce the
severity of head injuries.
> Here's some reading for you, complete with citations.
>
> http://www.bicyclinglife.com/SafetySkills/SafetyQuiz.htm
>
> Bicycling is NOT very dangerous. It does us no good to pretend it is.
I didn't say it was. But don't pretend that this cite is suggesting
that bicycling is so safe that you don't need to wear a helmet.
This is the crux of the matter: there are many types of injuries that
you can have on a bike, from the bruise I have on my leg right now from
a little mtbing last weekend, to road rash, to broken bones. But,
because, of the fact that cycling is a relatively safe activity, there
are very few types of injuries that are likely to be fatal. Like a
said, a mere "topple" at a standstill is all it takes to accelerate
your brain to a speed high enough to scramble it against the inside of
your skull, so a helmet provides protection against the type of injury
that is most likely to be fatal to a bicyclist.
David Damerell
Excuse me, I thought you would use the protective device no matter how big
N is? It says so right there.
Benjamin Lewis
> frkr...@yahoo.com wrote:
>> Arm or no arm, falling off a bike does not
>> "very likely" mean you'll bash your brains out! Serious head injuries
>> were never "very likely" no matter what.
>
> Wrong. A mere "topple" on from a bicycle even standing still will
> accelerate your head to a high enough speed that you can sustain a
> fatal head injury. It's that simple.
I notice that these two statements are not mutually exclusive. "Can" is
very different from "very likely".
--
Benjamin Lewis
"Love is a snowmobile racing across the tundra and then suddenly it flips
over, pinning you underneath. At night, the ice weasels come."
--Matt Groening
SocSecTr...@earthlink.net
Benjamin Lewis wrote:
> SocSecTr...@earthlink.net wrote:
>
> > frkr...@yahoo.com wrote:
> >> Arm or no arm, falling off a bike does not
> >> "very likely" mean you'll bash your brains out! Serious head injuries
> >> were never "very likely" no matter what.
> >
> > Wrong. A mere "topple" on from a bicycle even standing still will
> > accelerate your head to a high enough speed that you can sustain a
> > fatal head injury. It's that simple.
>
> I notice that these two statements are not mutually exclusive. "Can" is
> very different from "very likely".
There are pretty objective answers to this: the average brain in the
average head will be fatally injured in an unbroken fall from six feet
to an impact with an unyielding surface. It does not mean that that
type of impact will always or even usually occur in a "topple", hence
the use of the word "can".
Bill Sornson
You should have used it twice: "A mere 'topple'...from a bicycle even
standing still /will/ (*can*) accelerate your head to a high enough speed
that you can sustain a fatal head injury."
Bill "brain bucket buster...but not THAT often" S.
Benjamin Lewis
Indeed. Regardless of whether your first statement is true or not, I don't
see why you're saying Frank's statement was "wrong". Falling off a bike is
*not* "very likely" to lead to serious head injuries, just as he said.
SocSecTr...@earthlink.net
Bill Sornson wrote:
> You should have used it twice: "A mere 'topple'...from a bicycle even
> standing still /will/ (*can*) accelerate your head to a high enough speed
> that you can sustain a fatal head injury."
No, the acceleration of gravity is constant and a topple "will always"
accelerate your head to the same speed in the six feet to the
ground(disregarding unimportant variations in ambient air pressure and
head weight), hence the use of the word "will"; because of other
variables it "will not always" result in a fatal head injury, hence the
Bill Sornson
Perhaps for a crash-test dummy, but human beings tend to protect their heads
with hands, arms, neck muscles, etc. -- the latter of which /can/ decrease
said acceleration to less than fatal limits.
Minor distinction, admittedly...
BS
Werehatrack
>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 ?
Opinions only:
Cheaper helmets, from what I have seen, appear to have more foam in
them. More expensive helmets have more open spaces and fancier
sculpting. It has been stated by others that the fancier, more
expensive helmets have been shown to be just barely able to pass the
impact tests in the labs, while the cheaper ones pass with a greater
margin, presumably due to having more foam. I do not know if this is
the case in fact.
As far as the rest of it is concerned, there is no doubt in my mind
that the principle functional differences between the expensive
helmets and the cheap ones are insufficient to explain the price
gradient. In my opinion, a $200 helmet has that price tag because
there is a perception in the helmet industry that there is a market
for a $200 helmet. Everything done to justify that price in the
buyer's eye is, in my estimation, purely a matter of marketing hype.
(I will note, however, that if you ride in a sweltering climate like
mine, the difference in ventilation between a $25 helmet and a $45
helmet may be worth the expense. Beyond that point, I personally
can't see enough of a difference to merit more expense...and I paid $5
each for the last two that I bought, both from Goodwill, apparently
unused.)
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
Werehatrack
IIANM, they aren't certified by the CPSC, but rather are certified by
the manufacturer as meeting CPSC requirements. US government agencies
are notorious for coming up with a standard, requiring that it be met,
and then not providing the testing themselves.
Michael Press
<1120847530.1...@g14g2000cwa.googlegroups.com>,
SocSecTr...@earthlink.net wrote:
Get the physics correct. In free fall in a uniform gravitational
field the speed parallel to the field of the center of mass
increases linearly with respect to time; increases linearly with
respect to the square root of the distance traversed parallel to
the field. The kinetic energy increases linearly with respect to
the distance traversed.
The center of mass is never located in the region of the cranium.
Add angular momentum to a human body in free fall and movements of
the body itself and the acceleration of the cranium when the body
meets the ground varies widely.
No cans, no ifs. Categorical statements. Arguments from
experiments dropping melons in helmets are laughable.
When the cranium meets the pavement before any other portion of
the body serious injury ensues, helmet or no helmet, regardless of
the starting altitude; as the body follows torque on the cervical
vertebrae can fracture them, damage the brain stem, injure the
spinal cord, or swirl the brain in the brain pan like jelly in a
bowl. The best anyone should expect from a helmet is protection
from scalp laceration.
A young woman of my acquaintance, after a session in dance class,
dehydrated and weak from self-induce hunger, was talking to her
friends, fainted, and fell to the ground. Her brain swelled up
forcing the brain stem through the foramen magnum and she died.
Would a helmet have saved her life?
--
Michael Press
Michael Press
wrote:
> "yk" <y...@hotmail.com> 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
>
> Fit is high on the list. If you don't like it, you won't wear it, it
> won't be there when, not if, you need it. Christopher Reeves became a
> paraplegic from a fall from a horse. Yes he was higher but dirt is
> softer than asphalt.
What injuries did Mr. Reeve (note spelling) sustain in the fall?
How did the impact cause the injuries? Was he wearing a helmet
that horsemen wear?
--
Michael Press
Michael Press
E Willson <ewil...@patmedia.net> wrote:
> 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
> >
> >
> As far as I know, all helmets sold in the US meet basic safety standards
As far as you know.
> defined by the consumer protection agency. I believe the standard is Z90
You believe.
> (IIRC), and the helmet liner is marked accordingly. Moreover there used
> to be a more stringent standard used by the SNELL institute. Helmets
> with SNELL ratings used to be more safe (for penetration) than helmets
> that just met the Consumer protection standards. I am not sure if SNELL
You are not sure.
> still exists, but I would suggest that you look for a helmet that has a
> SNELL rating if you are looking for the ultimate in safety. I would
> appreciate comments from anyone who knows the current situation, because
> I am not sure of it.
No, you are not. Do your own research.
--
Michael Press
Michael Press
<1120695521.0...@g47g2000cwa.googlegroups.com>,
frkr...@yahoo.com wrote:
> Eric Hill wrote:
> > E Willson wrote:
> > > I am not sure if SNELL
> > > still exists, but I would suggest that you look for a helmet that has a
> > > SNELL rating if you are looking for the ultimate in safety. I would
> > > appreciate comments from anyone who knows the current situation, because
> > > I am not sure of it.
>
> The Snell rating still exists, in that any manufacturer who has a
> helmet that meets Snell requirements, and who wants to pay to have it
> certified by Snell, can do so. However, manufacturers seem to have
> decided en masse that it's not worth paying for that certification.
> The US law requires CPSC certification, and they're happy enough with
> that.
>
> And I wouldn't call Snell " the ultimate in safety." Snell is just
> slightly more stringent than CPSC. (CPSC requires a 2 meter drop;
> Snell a 2.2 meter drop.) The impact speeds are very nearly equal.
The kinetic energy is 1.1 times as great for the 2.2 m drop as the
2.0 m drop
[...]
--
Michael Press
frkr...@yahoo.com
SocSecTr...@earthlink.net wrote:
> frkr...@yahoo.com wrote:
> >
> > :-) So a 50% error doesn't matter? You're being awfully charitable
> > toward yourself!
>
> 4' ot 6', they're both within the design limits for which a helmet is
> designed to protect a head during a fall. Arguing the distance between
> your head and the pavement when you're sitting on a bicycle is
> completely irrelevant UNLESS YOU ARE GOING TO ALSO MAKE THE POINT THAT
> THE HEIGHT IS OUTSIDE THE LIMIT FOR WHICH THE HELMET IS DESIGNED TO
> PROVIDE PROTECTION!
Well, again: General population statistics show there has not been any
decrease in rates of serious bike head injuries since helmet use has
soared. Such injuries have always been rare, but they're no more rare
now that helmets are so common.
_Something_ must be responsible for this failure. We can discuss
what's responsible - but one obvious one is that helmets, designed and
tested for disembodied heads falling six feet, are simply not up to the
task.
Again, don't misunderstand me. I'm not calling for thicker, heavier
helmets. The data I've found shows that cycling is adequately safe
without a helmet. But people need to get realistic about the observed
effects (or lack of benefits) of helmets. The idea that they are
miraculous life-savers is
clearly wrong.
>
> > Arm or no arm, falling off a bike does not
> > "very likely" mean you'll bash your brains out! Serious head injuries
> > were never "very likely" no matter what.
>
> Wrong. A mere "topple" on from a bicycle even standing still will
> accelerate your head to a high enough speed that you can sustain a
> fatal head injury. It's that simple.
Would you please re-read and note the words "very likely"? Those were
the words you originally used, and they are wrong! It's NOT very
likely to happen as you describe. As evidence, we know that people
have been falling off bikes since the 1890s with very, very few
incidents such as the one you're describing.
(You must have learned to ride after 1975, and had protective parents
who made you wear a helmet while learning. Those of us who are older,
or who otherwise rode without helmets, know that head injuries were
never a serious concern.)
> > Certainly, there is no justification for thinking a helmet
> > certified only to protect a decapitated headform at only 14 mph will
> > suffice for any large percentage of the impacts.
>
> I said something along the lines of, "it will protect your upper brain
> tissue while the rest of your body (including brain stem) gets beat to
> hell". Again, arguing with me where I agreed with you three posts back.
We disagree on how much, or whether, it will protect "your upper brain
tissue." Again, the record is not good. All those helmets appeared on
bicyclists heads, and head injuries did not drop. The helmets are
designed for very low-energy impacts. Why do you think it's impossible
that these facts are related?
>
> > "A Bicycling Mystery: Head Injuries Piling Up." [Despite greatly
> > increased helmet use, that is.] New York Times, July 29, 2001.
> > http://www.cyclehelmets.org/1028.html
>
> It says, "No one is very sure, but safety experts stress that while
> helmets do not prevent accidents from happening, they are extremely
> effective at reducing the severity of head injuries when they do occur.
> Almost no one suggests that riders should stop wearing helmets, which
> researchers have found can reduce the severity of brain injuries by as
> much as 88 percent."
>
> "'Bicycle helmet technology is the best we have for protecting the
> brain,' Dr. Kelly said. 'The helmets serve the function of an air
> bag.'"
>
> "But the most effective way to reduce severe head injuries may be to
> decrease the number of accidents in the first place."
>
> Nothing in that article suggests that helments don't provide protection
> from head injuries.
???
The fact that helmet use rose tremendously, but head injuries did not
reduce? That doesn't suggest that helmets don't provide protection?
Perhaps you didn't notice the link to the actual data? Here it is:
http://www.cyclehelmets.org/1041.html
To quote from the footnotes of that data table: "The proportions of
head injuries did not change over the period despite helmet use in the
USA ncreasing from 18% of cyclists in 1991 to 50% in 2000. However,
cycle use during the period fell by 21%. Thus those who continued to
cycle were 40% more likely to suffer head injury by 2001 than in 1991."
Now, personally, I wouldn't be surprised if some of numbers in the
footnotes contain some error. I don't have high confidence in the 18%,
the 50% or the 21% - but whatever the exact numbers, those figures do
describe the trends. And with those trends, it's hard to see evidence
that all those helmets are protecting heads.
(I'm sure you won't complain about inaccurate numbers anyway, since you
believe your own 4' guess is close enough to 6'! ;-)
> > Hmm. Well, one of the most common serious car-bike collisions is the
> > left hook: car turns left into cyclist. Typical closing speed perhaps
> > 35 mph. Do you think the impact with the cyclist will usually be
> > below 14 mph?
>
> No, and if your head impacts the car, you will be in trouble. But, if
> what happens is that you get knocked away from the car, when you hit
> the ground the speed vector in the direction of the ground will be <
> 14mph, and your head will be protected while the "rest of your body is
> beat to hell".
OK, I give. You are apparently unable to understand that a
multi-jointed body will behave differently than a single concentrated
mass, and you can't understand that the energy input by the striking
automobile can cause much higher speeds than gravity.
It's OK. Everyone has their limitations.
>
> > Nobody suggested that "slide out" doesn't happen. In fact, I take
> > great comfort in the fact that it's _always_ happened, yet it's never
> > caused any significant number of serious head injuries.
>
> Brain injuries are about the only way to die from a "slide out".
Fine. Provide me with a few dozen incidents where people died when
their bikes slid out. Feel free to dig back into pre-helmet days, if
that helps.
I contend that such a fatality has always been vanishingly rare. Prove
me wrong.
> > Cyclists make up less than 1% of the head injury fatalities in America.
>
> That is a meaningless statistic, so ridiculous that I am not going to
> spend the time picking it apart in the many ways it could be done.
Need I say your rebuttal is not impressive?
>
> > This has _always_ been the case. The "bashing of brains" that you
> > fear was never an issue UNTIL Bell had a new product that needed to be
> > sold.
>
> My memory of it was that it was recognized that the leather hairnet did
> not provide any significant protection, and people wanted more. I knew
> racers that had had concussions, they were scared, and they wanted real
> protection.
To explain my position: I believe the relationship between bicycle
racing and ordinary road riding is the same as the relationsip between
NASCAR and driving out for groceries.
But having said that, road racers rarely wore leather hairnets. They
were seen almost exclusively on trackies and crit riders. Before the
hype and hysteria, even road racing was considered reasonably safe.
> > And it's certainly being sold! We now have an entire generation of
> > people who have been taught to link "bicycle" and "serious head injury"
> > without ever examining the data. We now have avid cyclists who mock
> > anyone who chooses to ride without the hat they prefer.
>
> If you don't personally understand the relationship between head injury
> and bicycling, you either don't ride enough, or you and your
> acquaintances have been very, very lucky.
Good grief! I've ridden as an enthusiastic adult since 1972. I've
held many offices (including president) of a large club. I've commuted
by bike since 1977 and have done extensive touring. And I've spent
years studying bike safety data. Why do you think you know more than
I?
Let me repeat:
> > Here's some reading for you, complete with citations.
> >
> > http://www.bicyclinglife.com/SafetySkills/SafetyQuiz.htm
> >
> > Bicycling is NOT very dangerous. It does us no good to pretend it is.
>
> I didn't say it was. But don't pretend that this cite is suggesting
> that bicycling is so safe that you don't need to wear a helmet.
Talk to me about data. Use numbers. Read that article, read the
answers to the questions, and explain to me why cycling is so dangerous
that you need to wear a helmet.
Be specific! So far, you've been hand waving and speaking imprecisely.
Get precise. Use numbers.
>
> This is the crux of the matter: there are many types of injuries that
> you can have on a bike, from the bruise I have on my leg right now from
> a little mtbing last weekend, to road rash, to broken bones. But,
> because, of the fact that cycling is a relatively safe activity, there
> are very few types of injuries that are likely to be fatal. Like a
> said, a mere "topple" at a standstill is all it takes to accelerate
> your brain to a speed high enough to scramble it against the inside of
> your skull, so a helmet provides protection against the type of injury
> that is most likely to be fatal to a bicyclist.
Get specific. Tell us how frequent that type of injury is. Tell us
how many cyclists die that way in a year. Tell us how many die that
way per hour. Prove, using numbers, that you're not fixating on some
remote possibility placed in your mind by an advertisement, or by some
mindless safety blurb.
Give us numbers. And no more of your "50% error doesn't matter"
nonsense. Give us reliable numbers, with sources. In that article,
that's what I've done.
- Frank Krygowski
Benjamin Lewis
> A young woman of my acquaintance, after a session in dance class,
> dehydrated and weak from self-induce hunger, was talking to her
> friends, fainted, and fell to the ground. Her brain swelled up
> forcing the brain stem through the foramen magnum and she died.
Ouch, scary. I had a similar experience about a year ago, but I caught
most of the impact on my shoulder instead of my head. My shoulder still
bothers me. I got a nasty bump on my head as well, but that healed in a
day or two.
Come to think of it, the *only* times I've hit my head on anything were
times when I was not riding a bicycle.
Chris B.
>
>A young woman of my acquaintance, after a session in dance class,
>dehydrated and weak from self-induce hunger, was talking to her
>friends, fainted, and fell to the ground. Her brain swelled up
>forcing the brain stem through the foramen magnum and she died.
>Would a helmet have saved her life?
Maybe, maybe not.
What's certain though is that if she was instead riding a bicycle at
the time, the Helmet Nazis would have said that she deserved to die
unassisted.
They're very, very concerned about other people, you see.
rr6...@gmail.com
failed, spliting the shell. His wife established the standard against
which manufacturer's could be held liable in the future.
The research on low speed impact, ie. cycling, is that *rebound* does
more damage and disability upon blunt force trauma.
Designs, good ones, use deformation compliant foams which ended the
popularity of the SkidLid type helmets in the 70's. Newer designs
employ pointy glancing blow radii to avoid dead-on blunt force impacts.
The logic being far superior to have survived w/neck injury than
brainstem damage.
frkr...@yahoo.com
rr6...@netscape.net wrote:
> SNELL died in the 60's from a race car crash in which his helmet
> failed, spliting the shell. His wife established the standard against
> which manufacturer's could be held liable in the future.
>
> The research on low speed impact, ie. cycling, is that *rebound* does
> more damage and disability upon blunt force trauma.
>
> Designs, good ones, use deformation compliant foams which ended the
> popularity of the SkidLid type helmets in the 70's.
Hmm. While I don't recall all the details, ISTM that Skid-Lid was done
under by the first Snell standard - which was set at a level that the
Bell Biker, already in production, could pass, but the Skid-Lid could
not.
Of course, Bell had a very close relationship with Snell, and Skid-Lid
did not. But I'm sure that had _nothing_ to do with the standard being
set at that precise level!
I was at a few bike conventions at that time. For a while, Skid-Lid
had sales booths showing letters of testimony from its "satisfied
customers," the now standard "My helmet saved my life!!!!" tales. I
recall one that came with an illustration of a cyclist going forward
over the bars and landing on the top of his Skid-Lid protected head.
Of course, in our enlightened times, we know that tale must have been
inaccurate. A below-standard helmet couldn't _possibly_ have saved his
life!
But if it happens with a slightly more protective modern helmet, it's
absolute proof the helmet saved a life!
;-)
- Frank Krygowski
Scott
No, I guess you're right, I didn't exactly think any of that up. But,
the point is that there are SOOO many more things that are WAAAY more
dangerous than cycling and folks think nothing of doing these things
with no thought about mediating the risks.
As for those folks who say that there's no reason not to wear a helmet,
I'd ask, what reason is there to wear a helmet?
Most folks come up with some distorted logic that falls into the "if it
saves even one life" mindset. Hell, if we as a society did everything
that met the criteria of a good idea because it saved even one life,
we'd never actually do anything.
As for me, the evidence is far from compelling that cycling is all that
dangerous and that across the greater population a helmet is all that
helpful. I'm talking about an analysis of the statistics to show
whether helmet use makes good policy for the population as a whole.
You can hang your hat on anecdotal evidence of someone who clearly
would've died but for their helmet if you want.
The question remains, if you decide what's best for you based on
knowing someone who knows someone who's cousin knew a guy who almost
cracked his head open, then why AREN'T you wearing kevlar vests while
walking the streets and helmets while driving???
Scott
No, I guess you're right, I didn't exactly think any of that up. But,
SocSecTr...@earthlink.net
Michael Press wrote:
> A young woman of my acquaintance, after a session in dance class,
> dehydrated and weak from self-induce hunger, was talking to her
> friends, fainted, and fell to the ground. Her brain swelled up
> forcing the brain stem through the foramen magnum and she died.
> Would a helmet have saved her life?
Asshole, my niece died in a car accident from a brain stem injury. Go
back and read my ealier posts in this thread.
Doug Huffman
Social (in)security won't save you.
<SocSecTr...@earthlink.net> wrote in message
news:1120951692.9...@g43g2000cwa.googlegroups.com...
Michael Press
<1120951692.9...@g43g2000cwa.googlegroups.com>,
SocSecTr...@earthlink.net wrote:
Tetchy. Reply to the rest of the posting that you excised without
comment; you could go for the full out cerebral event. Sadly, your
helmet will not help you there.
--
Michael Press