Helmet: building a better bicycle/inline helmet - Ideas?
John Faughnan
(Caveat: This isn't a posting about whether one should wear a helmet
or not[2], it's about building better helmets for those who choose to
wear them. Prior to posting I did some google searches to see if the
topic had been recently exhausted, the best discussion I found was in
an equestrian group in 1997 [1].)
I recently experienced a mild concussion (brief anterograde amnesia,
little or no loss of consciousness, limited post-impact headache)
associated with an inline skating fall and a face plant on concrete. I
was wearing a 3-4 yo helmet which compressed slightly along the right
anterior ridge.
The helmet protected my upper face (glasses, etc) and forehead, but
the lever action on impact probably aggravated my modest lower
face/teeth injuries. I suspect the helmet did reduce my concussion,
but the liner did not compress as much as I would have liked. My brain
thus declerated against the rough anterior inferior cranium then
rebounded against the posterior cranium.
I was glad I wore a helment, and I've bought a new one. I would have
liked to see more liner compression than occurred, however. I wonder
if it's possible to build a helmet that would have resulted in no
concussion in a low velocity fall like mine.
Are there helmets that:
1. Incorporate a dual density foam system, with one layer that
compresses fairly easily (lower speeds) and one that compresses only
at higher speed impacts? (This is, of course, how automobiles are
designed to collapse during a collision.)
2. Include an anterior "spike" that would provide more compression?
Helmets seem to bulk up in back now. Of course the value of this would
depend on studying case reports of traumatic brain injury in persons
wearing helmets to determine if anterior impacts are common enough to
warrant this measure. They might be more common amongst skaters than
bicyclists.
3. Have an expiration date on the helmet foam? (The liners used to
harden over time, I don't know if that's still true.)
Lastly, given #1 and #2, how much difference would it make to
decelerate over 1/2 cm (today's shells) vs. over 2 cm (dual layer foam
with a "spike")? Would this result in a 75% reduction of the force
applied to the brain?
Any other ideas?
--
john faughnan
jfau...@spamcop.net
http://www.faughnan.com/touringbike.html
[meta: jfaughnan, jgfaughnan, helmet, bicycle, concussion, fall,
improvement, design, better helmet, accident, TBI, traumatic brain
injury, dual-layer, double layer, inline skating, rollerblading,
blading, bicycling, touring]
[1] http://groups.google.com/groups?hl=en&lr=lang_en&threadm=339EF4FF.7E7C%40n-link.com&rnum=2
[2] http://www.magma.ca/~ocbc/ is a page by someone who thinks helmets
are (at best) overvalued. I disagree with most of his interpretations
of studies and with his overall conclusions, but he is correct that
helmets cannot eliminate head injury. I would also say that we need to
better understand the nature of head injury and what kind of helmet
design will help lessen traumatic brain injury (TBI). Happily my main
interest here is whether there's any way to improve helmets for my
use, rather than discussing whether others should use them.
Jkpoulos7
So. I've had several.
>I was glad I wore a helment
Why?
>Any other ideas
Helmets are for wimps.
smokey
please read the caveat in the original post. he clearly stated this
was NOT a post about whether or not one should wear a helmet. ENOUGH
with the helmet wearing flame wars, already!
smokey
Frank Krygowski
>
> I recently experienced a mild concussion (brief anterograde amnesia,
> little or no loss of consciousness, limited post-impact headache)
> associated with an inline skating fall and a face plant on concrete. I
> was wearing a 3-4 yo helmet which compressed slightly along the right
> anterior ridge.
A minor point: Amnesia in accidents is not necessarily due to
concussion. There are reports of people experiencing this phenomenon
after a sudden extreme shock (i.e. physical surprise) with no head
injury involvement at all. For example, I heard of one example where a
woman on stage in front of an auditorium suddenly slipped and fell to a
seated position, directly on her rump. Concussion was _very_ unlikely,
and she did not lose consciousness, but was very confused for about ten
minutes, unable to recall how she came to be at the auditorium!
Anyway:
> The helmet protected my upper face (glasses, etc) and forehead, but
> the lever action on impact probably aggravated my modest lower
> face/teeth injuries. I suspect the helmet did reduce my concussion,
> but the liner did not compress as much as I would have liked. My brain
> thus declerated against the rough anterior inferior cranium then
> rebounded against the posterior cranium.
>
> I was glad I wore a helment, and I've bought a new one. I would have
> liked to see more liner compression than occurred, however. I wonder
> if it's possible to build a helmet that would have resulted in no
> concussion in a low velocity fall like mine.
>
> Are there helmets that:
>
> 1. Incorporate a dual density foam system, with one layer that
> compresses fairly easily (lower speeds) and one that compresses only
> at higher speed impacts? (This is, of course, how automobiles are
> designed to collapse during a collision.)
Personally, I've not heard of one. Sizing pads compress easily, but
absorb no energy, so they don't count.
> 2. Include an anterior "spike" that would provide more compression?
> Helmets seem to bulk up in back now. Of course the value of this would
> depend on studying case reports of traumatic brain injury in persons
> wearing helmets to determine if anterior impacts are common enough to
> warrant this measure. They might be more common amongst skaters than
> bicyclists.
Seems to me spikes would likely have more negative effects than
positive. You're adding something which would make it easier for the
skull to be snapped sideways, converting a linear acceleration to a
potentially more damaging rotational one. The "bulk up in back" of
modern helmets is questionable for the same reason (although rear
impacts are much less frequent than frontal ones, so there's less
likelihood of demonstrating this disadvantage).
I think what you'd really want is simply a much bigger diameter helmet.
These things have been tried,
>
> 3. Have an expiration date on the helmet foam? (The liners used to
> harden over time, I don't know if that's still true.)
>
> Lastly, given #1 and #2, how much difference would it make to
> decelerate over 1/2 cm (today's shells) vs. over 2 cm (dual layer foam
> with a "spike")? Would this result in a 75% reduction of the force
> applied to the brain?
>
> Any other ideas?
>
> --
> john faughnan
> jfau...@spamcop.net
> http://www.faughnan.com/touringbike.html
>
> [meta: jfaughnan, jgfaughnan, helmet, bicycle, concussion, fall,
> improvement, design, better helmet, accident, TBI, traumatic brain
> injury, dual-layer, double layer, inline skating, rollerblading,
> blading, bicycling, touring]
>
> [1] http://groups.google.com/groups?hl=en&lr=lang_en&threadm=339EF4FF.7E7C%40n-link.com&rnum=2
>
> [2] http://www.magma.ca/~ocbc/ is a page by someone who thinks helmets
> are (at best) overvalued. I disagree with most of his interpretations
> of studies and with his overall conclusions, but he is correct that
> helmets cannot eliminate head injury. I would also say that we need to
> better understand the nature of head injury and what kind of helmet
> design will help lessen traumatic brain injury (TBI). Happily my main
> interest here is whether there's any way to improve helmets for my
> use, rather than discussing whether others should use them.
--
Frank Krygowski frkr...@cc.ysu.edu
Frank Krygowski
I recently experienced a mild concussion (brief anterograde amnesia,
> little or no loss of consciousness, limited post-impact headache)
> associated with an inline skating fall and a face plant on concrete. I
> was wearing a 3-4 yo helmet which compressed slightly along the right
> anterior ridge.
A minor point: Amnesia in accidents is not necessarily due to
concussion. There are reports of people experiencing this phenomenon
after a sudden extreme shock (i.e. physical surprise) with no head
injury involvement at all. For example, I heard of one example where a
woman on stage in front of an auditorium suddenly slipped and fell to a
seated position, directly on her rump. Concussion was _very_ unlikely,
and she did not lose consciousness, but was very confused for about ten
minutes, unable to recall how she came to be at the auditorium!
Anyway:
> The helmet protected my upper face (glasses, etc) and forehead, but
> the lever action on impact probably aggravated my modest lower
> face/teeth injuries. I suspect the helmet did reduce my concussion,
> but the liner did not compress as much as I would have liked. My brain
> thus declerated against the rough anterior inferior cranium then
> rebounded against the posterior cranium.
>
> I was glad I wore a helment, and I've bought a new one. I would have
> liked to see more liner compression than occurred, however. I wonder
> if it's possible to build a helmet that would have resulted in no
> concussion in a low velocity fall like mine.
>
> Are there helmets that:
>
> 1. Incorporate a dual density foam system, with one layer that
> compresses fairly easily (lower speeds) and one that compresses only
> at higher speed impacts? (This is, of course, how automobiles are
> designed to collapse during a collision.)
Personally, I've not heard of one. Sizing pads compress easily, but
absorb no energy, so they don't count.
> 2. Include an anterior "spike" that would provide more compression?
> Helmets seem to bulk up in back now. Of course the value of this would
> depend on studying case reports of traumatic brain injury in persons
> wearing helmets to determine if anterior impacts are common enough to
> warrant this measure. They might be more common amongst skaters than
> bicyclists.
Seems to me spikes would likely have more negative effects than
positive. You're adding something which would make it easier for the
skull to be snapped sideways, converting a linear acceleration to a
potentially more damaging rotational one. The "bulk up in back" of
modern helmets is questionable for the same reason (although rear
impacts are much less frequent than frontal ones, so there's less
likelihood of demonstrating this disadvantage).
I think what you'd really want is simply a much bigger diameter helmet.
These things have been tried, but didn't sell. The trend is to sell
lighter and lighter helmets, with more and more vent holes, getting
closer and closer to the minimum level of protection that will still
pass the simple certification test.
> 3. Have an expiration date on the helmet foam? (The liners used to
> harden over time, I don't know if that's still true.)
It was probably never true. The only test report I've found on an old
helmet (about 15 years old, IIRC) had the helmet passing just fine.
Styrofoam will eventually degrade in sunlight, but it takes years of
continuous exposure. Your helmet probably lives almost all its life
indoors. You can worry about UV degredation when you're in your 90s or
so.
Certain chemicals will degrade the foam, but unless your helmet-storage
closet is also your paint-remover closet, it's unlikely to be a
problem. In any case, the surface would be attacked before the bulk of
the foam's volume. Unlikely as it is, the damage would be easy to
detect.
It's true Bell Sports recommends (or recommended) replacing your helmet
every three years, but their website did not say because of foam
degrading; instead, they said something like "So you can take advantage
of advances in design and styling." I'm _sure_ it had nothing to do
with boosting their bottom line! ;-)
> Lastly, given #1 and #2, how much difference would it make to
> decelerate over 1/2 cm (today's shells) vs. over 2 cm (dual layer foam
> with a "spike")? Would this result in a 75% reduction of the force
> applied to the brain?
I think the formula you want is acceleration=0.5*(speed
squared)/distance
But keep in mind that the foam in a helmet can't be compressed to zero
thickness. This means, if you want 2 cm of compression, you'll need a
shell thickness something like, oh, three inches.
If you want such a helmet, you'll have to custom-make your own. They'll
never sell such a thing.
OTOH, a helmet is NOT a high-tech device. If you feel the need to have
this, it's perfectly feasible to make or, better, modify your own. Just
get some blocks of styrofoam (say, from packaging material for
electronics), cut them to fit and glue them on the outside of your
existing helmet. An electrically heated wire works well for cutting
foam. You can sculpt to a shape and size of your liking.
It may look a little odd, but clearly, odd looks are acceptable in
helmet wear!
--
Frank Krygowski frkr...@cc.ysu.edu