h a l f b a k e r yWhy on earth would you want that many gazelles anyway?
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Although there are safety standards for bicycle helmets, they are actually impossible to enforce, because a helmet should not be used again after it has received a blow, but there is no way to test a helmet to tell if it has received a blow (except possibly a destruction test).
By using a variant
of self-healing polymers embedded in the material of the helmet, we may be able to make a helmet that visibly displays damage.
Self-healing polymers normally release an agent that bonds a crack together to repair damage, but in this version, the embedded microcapsules would release a dye in order to highlight damage, so a bump that caused a microfracture that would degrade helmet reliability would cause that fracture to be visible on the surface of the helmet. At which point you know that it should no longer be used.
G
Similar principle
http://www.scienced...06/100607112046.htm
Semi-baked - same idea but releases a smell, not a dye [gtoal, Oct 09 2013]
Mechanical impact sensors
http://www.helmets.org/sensors.htm
helmet impact sensors - alternative solution, not rated very well [gtoal, Oct 09 2013]
[link]
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[+], but in my rather extensive experience on the subject,
one either remembers the helmet absorbing an impact, or
one does not remember much of anything at all, which is a
strong indicator of the incidence of impact. Also there is
the traditional visual inspection, considered so reliable a
method that there's a sticker on the inside telling you how
to do it. On the other hand, this is still a cool idea. |
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My new helmet fell off of my motorcycle seat on to gravel, leaving a series of little pits in the finish, and voiding the warranty. Perhaps multiple levels of microcapsules, for minor, moderate, and major abuses. |
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Bicycle helmets are a marketing fraud. |
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On the other hand, given the nature of bicycle
helmets, it might be better to prevent the
problem arising in the first place. |
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The reason that "hidden" damage is a problem is
that the core of the helmet is made of expanded
polystyrene, which is brittle and has a low work of
fracture. The thin shell is more flexible, making it
possible to damage the core whilst the shell is
intact. If a proportion of fibres were included in
the polystyrene, then |
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(a) it would be less likely to crack
(b) damage sufficient to crack it would probably
also make clearly visible cracks in the thin outer
shell and
(c) Even if it had a hidden crack, the fibres would
maintain its integrity and leave it almost as
effective as before. |
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The reason this isn't done already is probably that
moulding expanded polystyrene with fibres in it is
harder than without, and needs different
equipment. |
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//Bicycle helmets are a marketing fraud.
— pocmloc, Oct 08 2013
// |
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They're not impressive pieces of design, but I've seen one broken in two - I'm certain the wearer got his money's worth out of it. |
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Having, as a teenager, skidded my bike out on a
patch of sand and put a half inch deep dent in my
helmet, right over my temple, I'd say they do what
they're supposed to. |
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I don't recall that there were such things as bicycle helmets when I was a teenager... which could explain some things about previous generations. |
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//Care to elaborate?// It's a perception and conformity thing, rather than a practical or engineering thing. People get emotionally attached to their practice or decisions. |
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Why not just evolve thicker skulls ? If you
start now, in ten milennia you can throw
those silly hats away … |
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/Bicycle helmets are a marketing fraud.
— pocmloc, Oct 08 2013/ |
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Maybe pocmloc has the helmets mixed up with the
bicycle seatbelts. I admit to being skeptical about
those too. Especially the shoulder belt. |
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// rather than a practical or engineering thing// |
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See my above case where a helmet clearly saved me
from a head injury. Given the location, probably
severe, and possibly permanent or lethal. |
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[poc], with all respect, and I mean this in the least
antagonistic possible way somebody can possibly use this
phrase, this time you can blow it out your ass. |
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I have had my life saved by one helmet and been saved
from serious injury by two others; one of the latter was a
bicycle helmet that functioned precisely as designed in a
mountain bike-vs.-ash tree incident that left me with a
minor concussion and a broken clavicle. It could have left
me with a major skull fracture and permanent brain
damage. Bicycle helmets work and they are a neccessity.
Your socio-economic prosthelytizing, no matter how
sincere, is invalid. Sorry. |
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Ah yes sorry, I was not thinking of sports / extreme / mountain biking. In that case yes this idea has relevance and merit. |
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Penny farthing bicycles should have moustaches. |
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I'm just curious, were those of you who were saved by
bicycle helmets saved by the "rock climbing" style helmets
or the racing style ones that sit perched on top of your
head? I've been skeptical of the traditional/racing style
helmets. They don't offer any protection on the sides of
the head where it matters and are loosly barely held on by
a nylon strap. How do they work? |
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Mine was just a regular bike helmet, albeit a mid-quality
one sold at a bike shop. It was a pressed styrofoam bucket
with a thin plastic shell that seemed mostly cosmetic. |
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For the record, the other two helmets were a full-face
motorcycle helmet and a ski/snowboarding helmet (like a
rock climbing/extreme sports helmet with an insulated
liner). |
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Regular. It kept my head from hitting whatever it
was (a bit of paving gravel most likely), even though
it caught it down around the edge. Even if it had
been lower, it still would have helped by spacing the
rest of my head off the road. |
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And [Poc] mine was road biking. The sand was
leftover from the winter sanding of the roads. |
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// possibly ... lethal // |
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The perfect argument against bike helmets ... |
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