Wear your helmet kids!

It's hard to see a good alternative solution that wouldn't be unbearable to wear.

Exactly !. Now add manuf/retail costs into the mix and suddenly we're transported to a place where helmet design is very different to what we're wearing today.

S

Current helmets I've seen/I own, are dense polystyrene, and something as round and blunt as my head isn't going to compress it enough to enjoy any cushioning effect during an impact.

The density of polystyrene is carefully controlled and calculated to provide the best impact protection. The compression of the polystyrene provides a large deceleration during an impact event. When it approaches the maximum compression allowable by the density of the foam, the failure mechanism changes to that of fracture to further dissipate energy. Once fracture has occured the helmet has then dissipated as much energy as it can by design.

I haven't read all of this, as the usual suspects were present and correct early on and it's never very fruitful.

The crash occurred "on a double step down ". Now I'm not sure exactly what that is, but I'm confident that it is RAD to the power of sick. I'd be wearing a helmet if I was doing a "double step down", as I think 99% of us would be.

I'll still potentially not bother when I'm bimbling to the shops or doing other purely ambient and in no way gnarl things. 🙂

Just another anecdote, but I watched the occupant of this…

… piledriving head first into the ground after spectacularly misjudging a steep roll-in to a fire road. And he walked away from it (slightly unsteadily).

BigDummy, it was where one deep step followed directly after another one so the rear wheel went light as the front dropped down the first step then carried on going lighter (i.e skywards) as the front wheel dropped down the second step. I think it was one of those cases where if I'd been going a touch slower I could have saved it or a bit faster & I could have cleared it although my talent would also have run out on the second option I suspect!

I kinda knew that. 😉

Point is, even TJ usually admits that he wears a helmet when he's doing anything seriously fast or technical with any risk of falling off the bike that's greater than the risk of tripping over while walking. As with others, I wear a good, well-fitting helmet when I'm riding hard off road, but quite often a good, well-fitting trilby when I'm riding gently around town.

When it approaches the maximum compression allowable by the density of the foam, the failure mechanism changes to that of fracture to further dissipate energy.

After all this, that's what I was going to say 🙂 The foam probably flexed a bit, storing the energy and then the snap dissipated it. Have any of the posters measured the density of the foam through the helmet to see if it did in fact compress? Or are you just looking at a photo of the outside?

So let me get this straight. Are people (TJ) seriously advocating NOT wearing anything at all to protect your head in the case of an accident? I mean, if you have to headbut the ground, would you rather your head be completely naked, or wrapped in polystyrene?

Words fail me, they really do.

As for following the science Mr Jeremy, why don't you try it yourself? No scientist will want to stake his life on his 'theories', so wear a helmet just in case.

LHS.

Yes, I should have written "enjoy much cushioning…" rather than "enjoy any cushioning".

However, the polystyrene still isn't compressing very much, esp when forces are spread over the contact area of my head against the inner surfaces/contact points of the helmet. My skin is softer than the polystyrene in the helmet.

More often than not the crack originates from stress raisers and point loads play their part in propagating a failure, and as before, once failure occurs, the helmet ceases to protect although the accident being experienced could still be happening…

However, none of this appears to play much of a constructive role in controlling head decelleration, imo.
Do we have a "Pulse" for head impact, wearing a conventional cycle helmet.
Bet it spikes significantly just before the polystyrene fails…

Consider motorsport helmets, theres a bit more going on there, including cost and not forgetting the question/issue of comfort…

Then consider that we've all been shown the Sainsbury's/Tesco £8 specials, and there probably isn't a market for the £250 cycle helmet.

So, we pays our money…..But what is the choice ?.
🙂

S

Oh yay my post has resulted in a pic of naked women, who'd a thunk it 😆

So let me get this straight. Are people (TJ) seriously advocating NOT wearing anything at all to protect your head in the case of an accident?

As in my earlier post. I wear a current design of helmet.

However, I'm wondering whether it couldn't be done better, from a safety/protection performance prospective ?.

🙂

S

However, the polystyrene still isn't compressing very much, esp when forces are spread over the contact area of my head against the inner surfaces/contact points of the helmet. My skin is softer than the polystyrene in the helmet.

To reduce the decelleration your head sees during an impact event the polystyrene doesn't have to compress that much. You would be surprised.

We have done a lot of work at looking at different densities of foams and different thicknesses of EPS. The results are quite wide ranging but only up to a certain optimal point. We have also looked at variable EPS density liner where the density increases as you travel through the thickness to further control the rate of deceleration.

Solo, by people I meant TJ 🙂 I think your approach is a good one, but helmet manufacturers have been working on this for many years, I suspect that they are somewhat further down the development road than you 🙂

You already have several options. You could get a super vented light road lid, or an MTB specific one like a Giro Xen. For more protection you could get various degrees of full-facer, or even a BMX pisspot with a thick hard shell.

However, none of this appears to play much of a constructive role in controlling head decelleration, imo

Yeah but in all fairness, you are not doing any research or experimentation, you are just guessing.

So let me get this straight. Are people (TJ) seriously advocating NOT wearing anything at all to protect your head in the case of an accident? I mean, if you have to headbut the ground, would you rather your head be completely naked, or wrapped in polystyrene?

No, they're not. that's the bit that some people fail to grasp here. TJ has never said "don't wear a helmet" and has frequently said that if he knows he's doing techy stuff he always wears one.

All that some people are suggesting that sometimes it's not really necessary to wear one, and that generally people have a higher regard for the protective qualities of bicycle helmets that the evidence would suggest that they should….

Ok?

LHS, for whom do you work, if you don't mind me asking? Independent researcher or lid manufacturer?

Nickc – then it would be a classic case of TJ arguing for something utterly bleedin obvious whilst appearing to argue something controversial with the result that everyone gets wound up.

I think he does that because he doesn't understand people very well. If he really thinks that WE think that helmets are some kind of magical protection charm.

Thanks to IanMunro's pic my helmet is now leaking.

More often than not the crack originates from stress raisers and point loads play their part in propagating a failure, and as before, once failure occurs, the helmet ceases to protect although the accident being experienced could still be happening…

However, none of this appears to play much of a constructive role in controlling head decelleration, imo.
Do we have a "Pulse" for head impact, wearing a conventional cycle helmet.
Bet it spikes significantly just before the polystyrene fails…

After the helmet crack the helmet does not provide any more energy dissipation to the wearer. During the compression of the EPS liner the acceleration seen at the head decreases dramatically and during the fracture mechanism the energy is dissipated even further.

On an acceleration pulse plot you will see spikes during the initial impact, upon the bottoming out of the foam and after the energy dissipation due to fracture.

Believe me ALL of this plays a VERY constructive role in head protection.

Although I would always wear a helmet, they can most definitely make injuries worse in certain conditions.
I managed to lose my line whilst riding through a steep sided 'gully'. Bars glanced the soft side of the trail, causing me to spin into it. Helmet peak caught and rotated my head backwards whilst I was still traveling forwards. Still have a sore neck and headache 4 weeks on. I suspect that the design of the helmet contributed to this. A Zen fwiw. Large circumference for given head size on this helmet. Face made contact too, but was unmarked.
Wish I had been wearing my much closer fitting, and peakless, roadie helmet !

Helmet peak caught and rotated my head backwards whilst I was still traveling forwards

Anything that presents itself as a snag hazard will always be at detriment to protection. Any helmet peak should be designed such that it will snap away with a very low force so as to avoid the incident as described.

For what its worth, having had a relatively high speed (c.20 mph) head to tarmac incident recently. An inspection of my helmet shows compression over much of the front right hand side, and where the helmet has fractured it follows the line of deepest compression. That helmet has not failed, I cant say what state I would be in if I had not had it on, and I don't care to dwell on it.

Molgrips, can't figure out how to PM on here to discuss, in answer to your question – both.

There are no PMs on here, you have to email – mine is in my profile.

But cool to see someone working on scientific R&D for bike stuff – I am jealous 🙂

Yeah but in all fairness, you are not doing any research or experimentation, you are just guessing.

In all fairness MolGrips, you're quite wrong.

I have worked in the field of passenger restraint/occupant protection.
You may now remove your foot from your mouth. Top marks for getting it in there though.
😉

Believe me ALL of this plays a VERY constructive role in head protection.
As above, I wear one, and I beleive that in a lot of cases, a helmet is better than none at all. And while I'd never seek to rubbish the hard work developers put into the current design of the common helmet, I think we could benefit from a different approach to design.

Wish I had been wearing my much closer fitting, and peakless, roadie helmet
My case in point, design, I believe, has some way to go yet, if it does at all.

S

I think we could benefit from a different approach to design.

For example…………………………the floor is yours. What would you do different?

molgrips, I think he just gets wound up by the usual suspects saying things like "if I hadn't been wearing my helmet I'd be a vegetable now…" and when he tries to suggest that that might not necessarily be the case, people tend to get a bit angsty about it.

It may be 'bleedin obvious' but a lot of folk seem to miss it…

TT.

Oh, thats kind of you, but thats also a pretty impracticle proposition for a forum.

Just because I think it could be done differently, that doesn't mean I don't understand where we are now. As previously posted, when considering issues of safety, comfort, cost, I can see why we are here, but will it, should it be better.

Looking at some of the pics here of broken hats, I'm grateful the wearers claim to be Ok afterwards (regardless of being STW contributors 😛 )
But I think theres room for improvement, if for no other reason that to address the Nay-sayers, but really to reduce the percieved/alledged downsides to wearing current designs.

Or are we saying that current design is as good as its ever going to get ?.

Cheers.
🙂

Solo

It may be 'bleedin obvious' but a lot of folk seem to miss it…

Yeap, I agree.

S

If you think we could benefit from a different approach to design, but can't say why, what the differences are or what is wrong now, then what benefits do you think might be realised?

but can't say why

Nice try, but its not practical to go into this here.

Ta
🙂

S

But I think theres room for improvement

Same can be said for pretty much any product, but when you take into account the list of variables in the design you will realise that modern helmet design is very good.

You need to consider:

Weight
Size
Anthropometric head range
Material types
Impact Protection – Front, rear, side, crown, oblique
Penetration Protection
Durability
Manufacturability
Retention strength
Non recurring development cost
Recurring cost
Style
Cooling
Comfort

Large circumference for given head size on this helmet. Face made contact too, but was unmarked.
Wish I had been wearing my much closer fitting, and peakless, roadie helmet !

The bigger the helmet the better the protection… At least it's what most of test for crash helmet (from TJ's LR) seems to prove.

Agree on the peak. Funnily enough most of modern helmet have a peak that move/disengage under impact…

^^^ Cop out!

As for "I'd be a vegetable now" – I think that's a natural and excusable oversimplification. I don't think the layman pretends to know all about the intricacies of head trauma. However, a lot of people would almost certainly be in a lot more trouble without their helmets.

Like my mate who I had to pick up off the hardpack one summer afternoon many years ago after a bad high speed faceplant. He spent the night in hospital with concussion, and he was wearing a lid. Had he not, he'd have almost certainly had worse head injuries, and his nose would definitely have ended up all over his face.

LHS.

You repeat a point I've already made. I would add though, that a cycle helmet isn't just any other product.
😉

Agree on the peak. Funnily enough most of modern helmet have a peak that move/disengage under impact…

Things move-on.

S

LHS – there is some debate about the density of the polystyrene with some experts believing that the densities are too high leading to good performance in the testing but poor performance in the real world. There is data out there on this

nickc – ta – that is pretty much my point along with :-

I want to see a lot more and better quality research, better design, much more stringent testing including oblique impacts to test for rotational effects. Some testing has shown up to 1/3 of all oblique impacts injury severity worsened by the rotational accelerations.

As for my own usage – I just bought a Giro Xen as it fitted me well and has no sticky out bits. I also have a piss pot style helmet for winter / jumping type usage as I believe it offers marginally more protection but is too hot to wear all day – but if all I am doing is pootling around I don't wear one

Ah !, Molgrips, I wondered where you had got to…..

S

LHS.

You repeat a point I've already made

I don't think I did. You assumed that it was easy to improve on helmet design but then provided a complete inability to explain as to how.

LHS – there is some debate about the density of the polystyrene with some experts believing that the densities are too high leading to good performance in the testing but poor performance in the real world. There is data out there on this

Yes, a lot of the data out there comes from the work we do.

better design, much more stringent testing

Yeah, I'd like to see that too. But of course, there'll be a cost.
This is the dilema, the compromise.

S

I don't think I did. You assumed that it was easy to improve on helmet design but then provided a complete inability to explain as to how

v v v

Solo – Member
Hhmmm. Helmets…

The cracking of the helmet indicates energy dissapation, energy that would have otherwise had to of been dealt with, by natures protection…

However, upto the point the helmet failed, most of the energy was being passed to the head, imo.
My experience leads me to think that current popular helmet deisgn does not absorb much energy. The polystyrene, as dense as it is, seems to transmit energy to my head quite well.
I was reminded of this recently when for the first time in a long time, my helmet clipped a low branch.
It was still quite an abrupt shock to my head, very little energy had been absorbed by the helmet, there wasn't much cushioning of the blow and I attribute this to the dense polystyrene and the absence of a more compliant, cushioning, layer of material.
However, the skin had not contacted the branch so I wasn't left with any cuts, etc.

Current helmet design seems to be a compromise to meet several criteria, not all of which may be safety/crash centric.

How many helmet group-tests have we read where the journos refer to "cooling", "airflow", and even asthetic featrues ?
Throw into the mix, manuf costs and its not difficult to see how current helmet design has arrived at where it is now.

I don't think current designs are the best mankind could come up with for the primary purpose of preventing significant head/brain injury.

I think we only need look at helmets from other sports to get an idea of the solution other companies have come up with to try to prevent serious head injury.

Personally I fail to see the difference between a motorcyclist hitting their head against a lamp post at 25mph, and a mountain biker hitting their head against a tree at 25mph.

Yet, the helmet design solutions for each are very different…

But then again, who's going to wear a motorcycle helmet for a quick bit of XC riding ?…..

I'm glad the OP is Ok, and if they think that their helmet prevented a more serious injury, then thats fine.

However, I tend to think that it shouldn't be a question of whether or not to wear a helmet, there is definately a need for head protection.
But rather, which design solution should we be wearing ?.

Cheers.

Solo

I have provided no such inability. When did I write that it would be easy to imporve the design ?.

Look LHS, don't get wound up. You should knwo full-well its not practical to design a helmet in a forum posting and to invite someone to do so either implies that such work can be done this way, or other.

Are you telling us that your work has led us to the ultimate helmet design and improvement is no longer possible ?.

S

Other improvements I would like to see are better fit and retention systems – the "one size fits all" with the band is experimentally shown to reduce efficiency greatly.

I would also like to see further coverage – helmets that come down below the ears, onto the back of the head and onto the cheekbones – like some sking helmets

I like the developments in sliding layers on the outside to reduce rotations as well.

As solo says – its rather hard to see why differing sports with similar requirements end up with such different designs of helmets – unfortunately fashion and consumer acceptance plays a large part.

LHS – can you tell us who you work for?

something more like this is shape – but with more ventilation and made in EPS with a low friction outer layer – but not a hard shell.

TJ.

You're a brave soul making such specific suggestions, I had avoided it so as not to turn this into a flaming session.

Like you, I just think there could be more, and I hope there will be, for all us cyclists.

S