bump for the glitch

I don’t really get the TJ bashing that goes on with this (well, I do a bit coz he doesn’t always come across very well).
But I think some of his basic points are valid – “I crashed and would be dead if I didn’t have my helmet on” – you don’t know this is true.
Common sense might say it is, but common sense isn’t evidence.
Linking to individual peer reviewed articles doesn’t count as evidence either.
I suggest you have a look at evidence based practice and systematic reviews, the CEBM site explains the background quite well.
Cochrane review says’ they’re good by the way:
Helmets for preventing head and facial injuries in bicyclists

Diane C Thompson2, Fred Rivara1, Robert Thompson3

Abstract
Background
Each year, in the United States, approximately 900 persons die from injuries due to bicycle crashes and over 500,000 persons are treated in emergency departments. Head injury is by far the greatest risk posed to bicyclists, comprising one-third of emergency department visits, two-thirds of hospital admissions, and three-fourths of deaths. Facial injuries to cyclists occur at a rate nearly identical to that of head injuries. Although it makes inherent sense that helmets would be protective against head injury, establishing the real-world effectiveness of helmets is important.
Objectives
To determine whether bicycle helmets reduce head, brain and facial injury for bicyclists of all ages involved in a bicycle crash or fall.
Search strategy
We searched CENTRAL, MEDLINE, EMBASE, Sport, ERIC, NTIS, Expanded Academic Index, CINAHL, PsycINFO, Occupational Safety and Health, and Dissertations Abstracts. We checked reference lists of past reviews and review articles, studies from government agencies in the United States, Europe and Australia, and contacted colleagues from the International Society for Child and Adolescent Injury Prevention, World Injury Network, CDC-funded Injury Control and Research Centers, and staff in injury research agencies around the world. The searches were last updated in November 2006.
Selection criteria
Controlled studies that evaluated the effect of helmet use in a population of bicyclists who had experienced a crash. We required studies to have complete outcome ascertainment, accurate exposure measurement, appropriate selection of the comparison group and elimination or control of factors such as selection bias, observation bias and confounding.
Data collection and analysis
Two authors independently extracted data. Odds ratios with 95% confidence intervals were calculated for the protective effect of helmets for head and facial injuries. Study results are presented individually. Head and brain injury results were also summarized using meta-analysis techniques.
Main results
We found no randomized controlled trials, but five well conducted case-control studies met our inclusion criteria. Helmets provide a 63 to 88% reduction in the risk of head, brain and severe brain injury for all ages of bicyclists. Helmets provide equal levels of protection for crashes involving motor vehicles (69%) and crashes from all other causes (68%). Injuries to the upper and mid facial areas are reduced 65%.
Authors' conclusions
Helmets reduce bicycle-related head and facial injuries for bicyclists of all ages involved in all types of crashes, including those involving motor vehicles. Our response to comments from critics are presented in the Feedback section.
________________________________________

Plain language summary

Wearing a helmet dramatically reduces the risk of head and facial injuries for bicyclists involved in a crash, even if it involves a motor vehicle
Cycling is a healthy and popular activity for people of all ages. Crashes involving bicyclists are, however, common and often involve motor vehicles. Head injuries are responsible for around three-quarters of deaths among bicyclists involved in crashes. Facial injuries are also common. The review found that wearing a helmet reduced the risk of head or brain injury by approximately two-thirds or more, regardless of whether the crash involved a motor vehicle. Injuries to the mid and upper face were also markedly reduced, although helmets did not prevent lower facial injuries.

LoL @ Clubber 😉
Good one.

So, this being my first "helmet" thread, but being somewhat familiar with STW-F.

I am disappointed that this has turned into a true flame-war about injuries, but not surprized.

I was really more interested in where helmet design goes from here, and why.

LHS. Clearly you have experience and knowledge of this matter. Surely it would have been better for you to contribute on how things can be improved, as you admit there is room/scope to furthering helmet design.
So, how can the design move-forward ?, iyo.
(genuine Q)

TT. Imo, its gonna be difficult to design a cycle helmet in detail, on a forum thread, so much so that I wouldn't consider it practical. However, with LHS's and others contribution, would it be too difficult to discuss general features ?.

When TJ posted a few comments on what he'd like to see on helmets, I had hoped that would kick-off such a discussion, but alas it hasn't gone that way.

I'm not that interested in arguing other people's research, yadda, yadda.
Rather, how could the current day design be improved to perhaps, increase crash performance.

LHS. What say you to an outer cover that doesn't crack on initial impact, but rather deforms thus keeping the EPS from cracking ?.
I would think that a different density EPS would be required so that energy could be dealt with before the EPS failed ?.
🙂

Solo

terry – there is a major flaw in that which is discussed in depth [url=http://www.cyclehelmets.org/1069.html]here ( take your pinch of salt)[/url] and here Its also discussed on the BMJ site

The main criticism is that it is not a complete data set, its a self selecting sample which always gives false positives. You don't have the non helmet wearers who don't get injured for example.

Also no allowance is made for risk compensation nor for helmet induced injury – both of which occur although to what extent is debatable

Its not relevant because it is the same for both data sets.

It is! The proportion of people who end up in hospital from each data set is important. In order to know that, you have to know how many people don't end up in hospital, don't you?

molgrips – go and read the research

What it is looking at is the total number of head injuries. Non head injuries are not relevant. It compares the total number of head injuries against the number of cyclists before and after the legislative change

That critisism is relevvant to much of the research but not this one bcause of its design.

I know the research and the argument but I just dont see how wearing a helmet makes it more dangerous for you. Clearly the OP would have more injuries if he had not worn the helmet – of course I cant prove it any more than I can prove that the copper would have been hurt more if the bullet proof vest failed but it is just self evidently true whatever TJ wants to say for ever on this subject I can t read it all again.

"You don't have the non helmet wearers who don't get injured for example"

What you are asking for is impossible

Who in their right mind would go out of their way to say that they weren't injured to complete the statistics?

Unless you devise a sadistic experiment where people crash without helmets?

TJ – I mostly agree with you. My interpretation of the Cochrane SR is that helmets do reduce the severity of head injuries. However I don't believe all the "I'd have a fractured skull if I didn't have a lid on" anecdotes, because you simply don't know.

Also interestingly the SR's I've read show no reduction in head injuries in countries with compulsion – although I know this is slightly OT.

I wear a helmet most of the time, but I get pretty annoyed by people insisting you must wear one, when really its got nothing to do with them, and they're basing their insistance on feelings, not fact.

However I don't believe all the "I'd have a fractured skull if I didn't have a lid on" anecdotes, because you simply don't know

No but you can calculate the probabilty of a serious head injury.

We know the density of the skull and its tolerance to impact.
We know exactly how much force is required to break the helmet.

A simple calculation would work out the probability of a fracture or serious injury to the skull based on just those two facts.

So saying 'We don't know' maybe true because we are basing our assumptions on probabilities, but calculations show that you will most likely not walk away from that accident.

You don't know the force of impact, how that force is applied (eg over time – short sharp stop or a rolling impact for example), or even all the variables of a specific accident though, do you…

Solo, in answer to your question the evolution of helmet design would be different for each individual person based on what THEY considered to be the most important features. For most it would be something like

1. Protection
2. Cost
3. Style
4. Weight
5. Brand

Now, you could fiddle around with the top 5 till your hearts content depending on personal choice.

From a design point of view, for most MTB manufacturers it will come down to a combination of Protection, Cost, Manufacturability and style.

From a development point of view it usually comes down to looking at variances in:

Material – Foams, plastics, CFRP
Design – Variable density foam, varying thickness of outer shell, two part helmets with frangibl interfaces, collapsible/frangible features, shape factors, built in shearing elements.

A modern day fighter helmet for example has a CFRP shell of a certain designed in thickness, consisting of a particular weave of CFRP to get the right fracturing properties to dissipate maximum energy initially. This is built to a particular shape which not only fits the variances in anthropometric head size range but also builds in shape factors for increased or indeed decreased stiffness in particular areas.

This then has an EPS foam liner of a particular designed in density to provide maximum energy absorption whilst maintaining a controlled rate of deceleration and to a certain extent penetration properties too. The inside surface of the liners are formed from laser scans of the individuals head so that a pre-determined minimum thickness is maintained at all points of the head (to account for all the weird lumps and bumps we have)to ensure maximum protection. This laser scan also provides a "key" to the individuals head to stop rotation.

All that obviously comes at a price.

You know the force and you know the tolerances. You can deduce what kind of impact it was from the crack itself and the force required to create it.

Jeez, if Mr TJ can't suggest something better than a helmet, to wear instead of a bike helmet, then I really don't understand why he keeps going on.

LHS.

Thanks. Yes, I see that head shape and size would have to be dealt with to provide a mass production solution.

The cost, as you point out, is a question I kinda pointed at in earlier posts. Any scope for a similar but less costly mat'l to CFRP ?.

Multiple density foam, now we're talking. Again, I've no idea of whether the cost would be prohibitive for application to cycle helmets.

Ref the liner, are you referring to the main Foam structure or a thinner layer that actually contacts the wearers head ?.
Like:
Outer shell
Foam structure inside
thin liner of appropriately soft mat'l

Do you think it would be possible to achieve the desired pulse without the foam/EPS failing ?.

After all this, I would include, cooling. I reckon that heat build-up is one of the things thats going to get people taking their helmets off.
At the moment, my helmet has many vents in it, which give rise to the EPS only have point contact with my head in those areas.
Could we vent a helmet in another manner to increase the amount of foam in contact with the head ?.
Just thinking out-loud, Nasa ducting on the leading edge, sort of thing ?.

Cheers.

Solo

The Catlike Sacana is designed around a crumplezone concept. It's an interesting idea, if a bit 'directional'

How about a lightweight micro cooling system embedded in a helmet with no vents?

That helmet looks interesting, but do all those vents result in point contact on the wearers head ?.

Also, does the rear of the helemt need to wrap around the lower part of the back of the head ?.

S

Molgrips.

How would such a cooling device be powered ?, where would the components go in the event of impact ?, drive in towards the wearers head ??…

Could the frangibles serve a dual purpose of ducting air over the wearers head ?.

My understanding is that a 'roll cage' in the helmet holds everything together, prevents contact and spreads impact energy across the entire helmet. Not sure how that would work in reality but it's a good theory. Certainly haven't seen it before.

My helmet has contact points in the upper region, on the top of my head.
I'm thinking that they become the point of load during an impact.

I'm also thinking about the smoother, fuller contact area of other types of crash helmets that cover more of the head area.

An issue though would be cooling so as the helmet wasn't so hot as to be unwearable.

Perhaps leading edge ducts send air along the head and vent at the back, possibly incorporating some of the frangibles, if testing could provide a frangible pattern that lent itself to this dual purpose.

Just throwing a few ideas about.

S

Also, just thinking about issues with the Peak on helmets, possibly causing problems.

Break-away has been mentioned I think, IIRC.

How about soft rubber ?, weight permitting…

Then the peak coud just flex away, against the helmet/forehead.

S

Perhaps leading edge ducts send air along the head and vent at the back,

It's been tried. You can't have big enough hole at the front.

Btw, Specialised used to have a firm rubbery type peak that was only loosely attached, looked a bit like a batarang. They kept falling off – lost mine, found one at a race but a different colour. Used that despite it looking silly, then lost that to 🙂

http://www.cyclehelmets.org/papers/c2023.pdf

An interesting article that can be used as ammo by all sides of the argument!

It's been tried. You can't have big enough hole at the front.

Perhaps the entire leading edge could be open, feeding a duct network inside the foam, but the ducts pass through the foam/EPS and only have a max opening of 4mm at the bottom of the duct, onto the head.

LHS. Still with us ?.
🙂

S

Its not about winning – its about rational debate and learning.

Learning should be fun, surely? All I've 'learned' from this thread is that I've become incredibly bored by the constant and pointless arguing.

Oh no Vic I've fallen and I cannot get up…

LHS is long gone. He's too busy mucking around with stuff like this 😉

The new F-35 helmet. Just being trialed in the UK in advance of our first batch of…f-35s. mmmmmmmmm….

LHS is long gone. He's too busy mucking around with stuff like this

Yeah, could be. Shame though as LHS has current experience, etc.

Oh well, worth a try.

😉

S

For a decent helmet forget the F-35 and get one of these..

When i buy a helmet i make sure it's shiney and sparkley.

hmmmm, not going to enter into any further debate on the helmets work/dont work saga, im happy to take my chances and continue wearing one in the hope it makes things a little less worse if/when i have an off.

I would like to get in on the design debate though…..

I at first thought a slit along the leading edge would be a good idea, however, apart from the fact it has apparently been tried, i find when i am running downhill, im not to bothered as there is enough wind ect to keep me cool, my head gets to hot on climbs mainly and if i am pushing hard my head is not always looking forward as i maybe looking down quite a bit thinking that this hill is to big or the like!!! and even if i was looking forward, im not sure id be going fast enough to get any airflow through the vent 😆

therefore i personally think the current design with vents all over is probably the best ventalation system, well without sky rocketing the cost of helmets with electronic components ect.

jon

woah this thread has gone on for a long time and doesn't seem to get very far (which does imply whats already out there is pretty good 😉 )

Just read this, some of it may be relevant to your discussion..
http://www.telegraph.co.uk/family/7911432/James-Cracknell-Beverley-Turner-talks-for-the-first-time-following-her-husbands-near-fatal-accident.html

Personally I'd rather wear one than not – when I was younger went over the bars, I spent 8 hours in surgery and two weeks in hospital with head injuries – due somewhat to the impact but more to landing on a newly gravelled road without a helmet.

I don't care if there is no alternative that is better – I'll be wearing a helmet as some protection is better than none.

im happy to take my chances and continue wearing one in the hope it makes things a little less worse if/when i have an off

Yeap, I'd agree with that.
🙂

I have to admit, cooling is a secondary concern for me, when considering how future helmet design might improve for its primary function.

What I don't like about my helmet is that it only seems to cover the top of my head, reaching only a short way down the back.

I guess I'd prefer more coverage, and was hoping LHS might throw some light on whether that would be a good direction to develop towards.

I'm also distracted by the breakage of helmets, but I'm guessing that once the impact reaches forces that exceed the HIC, then failure is possibly the only option.

Other sports seem to employ helmets that offer more coverage, but as others have pointed out, most MTB'ers, me included, like not to suffer a massively hot head.

I just can't help thinking that perhaps current helmet design has got stuck into a rut, based on performance, cost, manufacturability, sales, etc.

As I posted way back on like the 2nd page, whos going to stump-up £250 for a helmet ?, esp now that super markets have sold basic, conventional looking items for less than £10 ?.

Initially I resisted trying to design a cycle helmet by posting on a thead, for its pratical limitations, but then I realised that if someone such as LHS was going to contribute, then perhaps we could at least discuss general features that we'd either like to see come-out in new designs, or stuff we think we'd like to see the end to.

Another feature is the strapping. Seems to me that the strapping wraps around my head, but still allows the structure of the helmet to "wobble" around on my head, ie, theres still a fair bit of "play" once the strap is done-up. I know we can't all be laser-scanned for the fitment of our new helmet, but perhaps theres another strapping strategy thats being over-looked on the basis of what is curernt and cost effective.

S

I was reading about the James Cracknell incident at the weekend. Hope he makes a full recovery. Glad his helmet did the job for him. You would be amazed at how much an inch or so of EPS liner can reduce deceleration by and be the difference between life and death.

Also, as a side point, anyone who drops there helmet and thinks it will be ok, think again, you potentially will have lost the majority of the impact protection due to the EPS already being compressed, even if there isn't really any visible damage. Always replace your helmet after an impact.

Solo, happy to answer a few questions but am also aware I have a day job and spend enough time on here anyway!

As to the discussion on more side impact protection, a lot of it will come down to what is forseen to be the type of accident possible which will determine the design of a helmet. For example, a helmet designed for helicopter use has far more side impact protection – the helmet shell comes further down around the ear and a lot of features are built in like collapsible earcups. This is because the findings of fatalities in aircrew crashes was that within a helicopter environment blows to the side of the head from surrounding structure are far more common.

For fast jet helmets the main protection is focussed around the rear of the helmet due to the impact suffered on ejection. As the pilot ejects the air pressure change from the canopy firing off pulls the pilot forward and as he ejects into the airstream this then slams his head back against the seat headpad.

So for protection for bikes it will be the perceived types of accidents that are prevailant and also your aesthetics and weight issues will come into it. You can't add that amount of structure to a helmet without it looking ugly and adding weight.

So for protection for bikes it will be the perceived types of accidents that are prevailant and also your aesthetics and weight issues will come into it. You can't add that amount of structure to a helmet without it looking ugly and adding weight

And so there in lies the current circumstances that have lead to current designs ?.

As cycle helmets have moved towards the Look of todays current design with perhaps a disproportionate emphasis on cool/ing.
I would expect that most manufs might consider it too much to try to develop in an alternative direction.

But this could also be the challenge.

To actually add the material, where it would seem to be needed, but also, imo, to look at how the EPS structure contacts the head, and how the helemt is secured to the head.

As I posted earlier, due to all the venting along the top of my helmet, the EPS has only relatively slim, contact patches, touching my head.
So therefore to achieve the desired pulse, I'd expect that the available contact area would influence the density, etc of the foam selected.

If the contact areas could be increased, could one use a lower denisty of foam, thus perhaps not increasing weight quite so much ?.
All subject to testing, obviously.

And I still wonder whether a thin layer of another type of material, a liner, would also assist in reducing the forces experienced during impact.
🙂

Ta

Solo

I'd say the biggest problem in MTB helmets is the price! Most helmets have very similar construction, yet the prices go from £25 up to £200. I imagine the margin on the top end helmets is pretty good.

Also, as a side point, anyone who drops there helmet and thinks it will be ok, think again, you potentially will have lost the majority of the impact protection due to the EPS already being compressed, even if there isn't really any visible damage. Always replace your helmet after an impact.

This is another problem – in the real world your helmet is going to get dropped, knocked, scuffed. The user finds it difficult to see if it's compromised, the manufacturer would rather err on the side of caution and say it is compromised. Why can't we have some indicators built in that show clearly when certain portions are irrepairably damaged.

Also would a more modular helmet be possible I wonder? So you could replace the bits that are damaged.

And why do we not see CF on the exterior of XC helmets? I have a CF full face, but wouldn't a layer of CF instead of the PC or whatever they use make a big difference to impact strength?

I see TJ's point about helmets increasing the rotational forces. I'm just struggling to see a way of making a helmet that keeps the head the same size or even reduces it :/

Interesting piece on James Cracknells recent accident;

http://road.cc/node/20957

Judging from this discussion, helmet compulsion is only a couple of years away. Then legal disclaimers for riding on owned land, then bike bans as in some towns in the states…