Sportsman saved by helmet. Makes you wonder how light a cycle helmetcould be and still work right.

Duane writes:

On 7/22/2014 2:22 PM, Joe Riel wrote:
Duane writes:

Woman riding with us Sunday hit one of the stupid poles that mark bike
lanes. On this lane (about 5km long) they removed all but one. She
must have sided to the left a bit and it clipped her bar. Went down
sideways and landed on her back. You could hear her head smack the
tarmac for blocks. I didn't tell her that she wouldn't have hit her
head if it wasn't for the helmet. And no one remarked on whether
Frank somebody or other on some newsgroup somewhere would have been
displeased when she said that she was glad the helmet was cracked and
not her head. YMM indeed V.

A cracked helmet isn't indicative of much; helmets crack fairly easily
and don't dissipate significant energy doing so. The energy dissipation
comes from crushing. How detectable is a crushed liner following an
impact? Has anyone seen the before/after of a helmet test?


Not sure how easily is fairly easily. I've had falls when the helmet
broke and falls when it didn't. I think it takes a pretty good
beating.

A crack suggests a tensile load. A possible cause of that is a bending
load, which puts the outer surface of the bent member [could be the
inner surface of the helmet] in tension.

I'd like to see an experiment that measures the typical impact that
*cracks* a helmet; what sort of accelerations is the headform subjected
to? It should be significantly lower than the pass/fail limit.
Somewhat indicative of the robustness of the helmet.

--
Joe Riel

On 7/22/2014 3:02 PM, Joe Riel wrote:
Duane writes:

On 7/22/2014 2:22 PM, Joe Riel wrote:
Duane writes:

Woman riding with us Sunday hit one of the stupid poles that mark bike
lanes. On this lane (about 5km long) they removed all but one. She
must have sided to the left a bit and it clipped her bar. Went down
sideways and landed on her back. You could hear her head smack the
tarmac for blocks. I didn't tell her that she wouldn't have hit her
head if it wasn't for the helmet. And no one remarked on whether
Frank somebody or other on some newsgroup somewhere would have been
displeased when she said that she was glad the helmet was cracked and
not her head. YMM indeed V.

A cracked helmet isn't indicative of much; helmets crack fairly easily
and don't dissipate significant energy doing so. The energy dissipation
comes from crushing. How detectable is a crushed liner following an
impact? Has anyone seen the before/after of a helmet test?


Not sure how easily is fairly easily. I've had falls when the helmet
broke and falls when it didn't. I think it takes a pretty good
beating.

A crack suggests a tensile load. A possible cause of that is a bending
load, which puts the outer surface of the bent member [could be the
inner surface of the helmet] in tension.

I'd like to see an experiment that measures the typical impact that
*cracks* a helmet; what sort of accelerations is the headform subjected
to? It should be significantly lower than the pass/fail limit.
Somewhat indicative of the robustness of the helmet.


Hmmm. I'm not that familiar with Styrofoam but I thought tensile
strength was more of a factor for brittle materials. I work for a
company that among other things, does heat treatment using nitriding
systems and this is an issue when hardening steel. While I'm not a
metallurgist, I do design software based on their requirements.

I would have thought that Styrofoam was not that brittle and any cracks
would have been caused by compression induced stress.

On 7/22/2014 12:03 PM, jbeattie wrote:
On Monday, July 21, 2014 3:35:07 PM UTC-7, Frank Krygowski wrote:
My "Any helmet will do" was based on the
assumption that (as here) people will note "he wore a helmet" and look
no further.

And except for the fact that you can't sell a bicycle helmet in the US
unless it meets CPSC standards.

While that's correct, I don't that's widely known. And I strongly
suspect that if (say) a kid crashed his bike while wearing a football
helmet or a construction hard hat, there would be no mention in the news
that "he was not wearing a helmet." I also doubt that in a MHL
district, such a kid would be ticketed for absence of a helmet.

As an aside, I was at a product inspection yesterday with my expert
engineer and plaintiff's attorney. All of us were current or former
racers.
We were looking at the plaintiff's crushed helmet, and we all had stories
of ruining helmets and head injuries. Plaintiff's attorney just bought
MIPS
ski helmets for his kids:
http://www.pocsports.com/en/content/...w-technologies
The expert was recovering from a concussion, collapsed lung, many broken
ribs,
clavicle fracture, all from a non-vehicle related crash. He did the OTB,
pile-driver, head and shoulder in to the concrete thing. Yes, he is
convinced his helmet saved him from more serious head injury. Being that he
is an engineer, he has to be correct.

OK, trading anecdotes is always fun. I'll give you these:

1. One guy in our club brought his cracked helmet to a meeting. He was
riding with his jacket tied around his handlebars, and it drooped and
tangled in his front spokes, yielding an OTB crash. Of course, his
message was "Always wear your helmet." (Mine was "Use a bike bag, and
always keep everything out of your spokes.")

Anyway, he is an engineer and owner of a pretty big engineering firm. I
later asked to see the helmet and said "Look at this. These things are
designed to protect you by yielding in compression, by crushing. Yours
didn't crush at all. This crack is a tensile failure." He was a bit
surprised, but he agreed with me that the situation wasn't what he'd
thought.

We looked at it for quite a while, and couldn't say exactly what loads
led to that tensile crack. But I think it's obvious that a cracked
helmet is NOT proof that a head injury was prevented.

2. On a solo ride early this year, I came across a young lady on a nice
bike who was just finishing a ride. We had a friendly conversation for
a while, then just as we were parting, she asked "So why aren't you
wearing a helmet?"

I gave her the one-minute explanation, which I'm sure nobody here wants
me to repeat. But she then mentioned "You know, I was on a ride last
year and I don't know how it happened, but I went A over TK. I got all
scraped up, and I almost hit my head, but somehow I didn't."

I asked "Do you think your helmet would have hit the ground if you had
been wearing it?" "Yes, I think so" she said.

"And would it have been damaged? Yes. And would people have told you
it saved your life? Yes, definitely. But would it have?"

She said "I see what you mean. No, obviously it wouldn't have."

3. This probably counts as data, not anecdotes. But how many Tour de
France riders have been saved from either death or terrible TBI by their
helmets since the Tour has mandated them? There have been _lots_ of
cracked helmets, of course.

Before answering, one should probably try to find the number of terrible
traumatic brain injuries and fatalities that occurred _before_ that
mandate, in all those millions of person-miles of intense racing. And
when (or if) you can find the tiny number, remember that helmets are
certified for perfectly linear impacts up to 14 mph.

So, as I was writing this post, one of the secretaries tells me that
one of my work-mates and bicycling cohort crashed descending in the
parking garage -- maybe a 20 percent down slope with a steel drain
grate half-way down. It rained today for the first time in a month
(maybe), and it's slicker than sh** out there. He slipped on the drain
grate and somehow went OTB, whacked his head, broke his helmet.
He's going home for the day. I tried to convince him that he did not
crash; that bicycling is absolutely safe; that his helmet did not help
him in any way and that he was not hurt. It didn't work.

Nothing is absolutely safe, Jay. And it's possible his helmet did help
him, although it's (obviously?) not proven.

But I'll bet that there more Portland pedestrians than bicyclists
cracked their heads today. It's certainly true nationally. Boy, if you
could just get fragile styrofoam on all those pedestrian heads, you'd
have _far_ more anecdotes!

I hope your work-mate has learned about wet steel. It's surprising to
me that a Portland cyclist doesn't know that!

--
- Frank Krygowski

On Tuesday, July 22, 2014 3:18:52 PM UTC-4, Duane wrote:
On 7/22/2014 3:02 PM, Joe Riel wrote:

Duane writes:



On 7/22/2014 2:22 PM, Joe Riel wrote:

Duane writes:



Woman riding with us Sunday hit one of the stupid poles that mark bike

lanes. On this lane (about 5km long) they removed all but one. She

must have sided to the left a bit and it clipped her bar. Went down

sideways and landed on her back. You could hear her head smack the

tarmac for blocks. I didn't tell her that she wouldn't have hit her

head if it wasn't for the helmet. And no one remarked on whether

Frank somebody or other on some newsgroup somewhere would have been

displeased when she said that she was glad the helmet was cracked and

not her head. YMM indeed V.



A cracked helmet isn't indicative of much; helmets crack fairly easily

and don't dissipate significant energy doing so. The energy dissipation

comes from crushing. How detectable is a crushed liner following an

impact? Has anyone seen the before/after of a helmet test?





Not sure how easily is fairly easily. I've had falls when the helmet

broke and falls when it didn't. I think it takes a pretty good

beating.



A crack suggests a tensile load. A possible cause of that is a bending

load, which puts the outer surface of the bent member [could be the

inner surface of the helmet] in tension.



I'd like to see an experiment that measures the typical impact that

*cracks* a helmet; what sort of accelerations is the headform subjected

to? It should be significantly lower than the pass/fail limit.

Somewhat indicative of the robustness of the helmet.





Hmmm. I'm not that familiar with Styrofoam but I thought tensile

strength was more of a factor for brittle materials. I work for a

company that among other things, does heat treatment using nitriding

systems and this is an issue when hardening steel. While I'm not a

metallurgist, I do design software based on their requirements.



I would have thought that Styrofoam was not that brittle and any cracks

would have been caused by compression induced stress.

Someone will be ciming in soon stating that if the person in these accidents had NOT beeb wearing a helmet then there was a very good chance that they wouldn't have hit their head. After all, helmets add an entire inch or so the the wigth of each side of the helmet.

Cheers

On 7/22/2014 1:33 PM, Duane wrote:


Woman riding with us Sunday hit one of the stupid poles that mark bike
lanes. On this lane (about 5km long) they removed all but one. She
must have sided to the left a bit and it clipped her bar. Went down
sideways and landed on her back.

There's actually a sign of hope here. We may not be able to educate the
true believers of helmets, but perhaps we can educate the true believers
of barrier-separated bike lanes, eh?

In the meantime, I guess we'll have to continue to hope that our
magical, certified-for-14-mph hats will protect us from the segregated
infrastructure that's ... um, protecting us.

--
- Frank Krygowski

On 7/22/2014 3:02 PM, Joe Riel wrote:
Duane writes:

Not sure how easily is fairly easily. I've had falls when the helmet
broke and falls when it didn't. I think it takes a pretty good
beating.

A crack suggests a tensile load. A possible cause of that is a bending
load, which puts the outer surface of the bent member [could be the
inner surface of the helmet] in tension.

I'd like to see an experiment that measures the typical impact that
*cracks* a helmet; what sort of accelerations is the headform subjected
to? It should be significantly lower than the pass/fail limit.
Somewhat indicative of the robustness of the helmet.

Mentioned before, but on an overseas tour, back when I still believed a
bit in helmets: I was carrying my helmet and either rolling or carrying
(I forget) my bike down a steep, moist, grassy slope when I slipped and
fell. I sat directly down on my butt. I was a bit embarrassed, but
wasn't even close to hurt, not even a little.

I sat there and looked at the helmet I was carrying. It was very badly
cracked. In fact, one handful-sized chunk of the styrofoam was
completely detached, and there were other big cracks as well. Only the
microshell was holding it together.

There's no way to tell what caused that failure. I didn't land on the
helmet; it was in front of me as I fell backwards. I don't know if I
reflexively clutched it too hard or what.

But it obviously saved my life! ;-)


--
- Frank Krygowski

Duane writes:

On 7/22/2014 3:02 PM, Joe Riel wrote:
Duane writes:

On 7/22/2014 2:22 PM, Joe Riel wrote:
Duane writes:

Woman riding with us Sunday hit one of the stupid poles that mark bike
lanes. On this lane (about 5km long) they removed all but one. She
must have sided to the left a bit and it clipped her bar. Went down
sideways and landed on her back. You could hear her head smack the
tarmac for blocks. I didn't tell her that she wouldn't have hit her
head if it wasn't for the helmet. And no one remarked on whether
Frank somebody or other on some newsgroup somewhere would have been
displeased when she said that she was glad the helmet was cracked and
not her head. YMM indeed V.

A cracked helmet isn't indicative of much; helmets crack fairly easily
and don't dissipate significant energy doing so. The energy dissipation
comes from crushing. How detectable is a crushed liner following an
impact? Has anyone seen the before/after of a helmet test?


Not sure how easily is fairly easily. I've had falls when the helmet
broke and falls when it didn't. I think it takes a pretty good
beating.

A crack suggests a tensile load. A possible cause of that is a bending
load, which puts the outer surface of the bent member [could be the
inner surface of the helmet] in tension.

I'd like to see an experiment that measures the typical impact that
*cracks* a helmet; what sort of accelerations is the headform subjected
to? It should be significantly lower than the pass/fail limit.
Somewhat indicative of the robustness of the helmet.


Hmmm. I'm not that familiar with Styrofoam but I thought tensile
strength was more of a factor for brittle materials. I work for a
company that among other things, does heat treatment using nitriding
systems and this is an issue when hardening steel. While I'm not a
metallurgist, I do design software based on their requirements.

I would have thought that Styrofoam was not that brittle and any
cracks would have been caused by compression induced stress.

Polystrene is brittle; I don't think it would work well otherwise.


--
Joe Riel

jbeattie writes:

So, as I was writing this post, one of the secretaries tells me that
one of my work-mates and bicycling cohort crashed descending in the
parking garage -- maybe a 20 percent down slope with a steel drain
grate half-way down. It rained today for the first time in a month
(maybe), and it's slicker than sh** out there. He slipped on the
drain grate and somehow went OTB, whacked his head, broke his helmet.

Any clue as to how he went over the bars? Maybe applied front brake
while on steel grate, tires began sliding, so squeezed harder, then bike
slid off grate back onto asphalt where the tire, with locked wheel,
grabbed? Though on a 20 percent downslope, any sort of crash might
quickly become more or less over the bars.

--
Joe Riel

On 22/07/2014 21:59, Joe Riel wrote:
jbeattie writes:

So, as I was writing this post, one of the secretaries tells me that
one of my work-mates and bicycling cohort crashed descending in the
parking garage -- maybe a 20 percent down slope with a steel drain
grate half-way down. It rained today for the first time in a month
(maybe), and it's slicker than sh** out there. He slipped on the
drain grate and somehow went OTB, whacked his head, broke his helmet.

Any clue as to how he went over the bars? Maybe applied front brake
while on steel grate, tires began sliding, so squeezed harder, then bike
slid off grate back onto asphalt where the tire, with locked wheel,
grabbed? Though on a 20 percent downslope, any sort of crash might
quickly become more or less over the bars.

Squeezed front brake, front washed out, over forwards/sideways? So not
directly OTB, but similar enough, and doesn't require regaining of grip.

Clive George writes:

On 22/07/2014 21:59, Joe Riel wrote:
jbeattie writes:

So, as I was writing this post, one of the secretaries tells me that
one of my work-mates and bicycling cohort crashed descending in the
parking garage -- maybe a 20 percent down slope with a steel drain
grate half-way down. It rained today for the first time in a month
(maybe), and it's slicker than sh** out there. He slipped on the
drain grate and somehow went OTB, whacked his head, broke his helmet.

Any clue as to how he went over the bars? Maybe applied front brake
while on steel grate, tires began sliding, so squeezed harder, then bike
slid off grate back onto asphalt where the tire, with locked wheel,
grabbed? Though on a 20 percent downslope, any sort of crash might
quickly become more or less over the bars.

Squeezed front brake, front washed out, over forwards/sideways? So not
directly OTB, but similar enough, and doesn't require regaining of
grip.

That scenario seems more likely.

--
Joe Riel