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-- gtoal, Oct 08 2013 Similar principle http://www.scienced...06/100607112046.htmSemi-baked - same idea but releases a smell, not a dye [gtoal, Oct 09 2013] Mechanical impact sensors http://www.helmets.org/sensors.htmhelmet impact sensors - alternative solution, not rated very well [gtoal, Oct 09 2013] [+], 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.-- Alterother, Oct 08 2013 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.-- normzone, Oct 08 2013 Bicycle helmets are a marketing fraud.-- pocmloc, Oct 08 2013 I like this.
On the other hand, given the nature of bicycle helmets, it might be better to prevent the problem arising in the first place.
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
(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.
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.-- MaxwellBuchanan, Oct 08 2013 //Bicycle helmets are a marketing fraud. — pocmloc, Oct 08 2013 //
Care to elaborate?-- Custardguts, Oct 08 2013 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.-- normzone, Oct 09 2013 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.-- MechE, Oct 09 2013 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.-- FlyingToaster, Oct 09 2013 //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.-- pocmloc, Oct 09 2013 Why not just evolve thicker skulls ? If you start now, in ten milennia you can throw those silly hats away …-- 8th of 7, Oct 09 2013 /Bicycle helmets are a marketing fraud. — pocmloc, Oct 08 2013/
Maybe pocmloc has the helmets mixed up with the bicycle seatbelts. I admit to being skeptical about those too. Especially the shoulder belt.-- bungston, Oct 09 2013 // rather than a practical or engineering thing//
See my above case where a helmet clearly saved me from a head injury. Given the location, probably severe, and possibly permanent or lethal.-- MechE, Oct 09 2013 [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.
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.-- Alterother, Oct 09 2013 Ah yes sorry, I was not thinking of sports / extreme / mountain biking. In that case yes this idea has relevance and merit.-- pocmloc, Oct 09 2013 Right then.-- Alterother, Oct 09 2013 Penny farthing bicycles should have moustaches.-- FlyingToaster, Oct 09 2013 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?-- DIYMatt, Oct 09 2013 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.
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).-- Alterother, Oct 09 2013 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.
And [Poc] mine was road biking. The sand was leftover from the winter sanding of the roads.-- MechE, Oct 09 2013 // possibly ... lethal //
The perfect argument against bike helmets ...-- 8th of 7, Oct 09 2013 random, halfbakery