Helmet performance
benthic
Posts: 26
Is there a way of knowing, ex-ante, which models of cycle helmet are more likely to compress on impact, thereby giving me some protection, rather than just split, which offers little protection?
For example, should I look for;
* a particular shape?
* price?
* brand?
* testing standard?
* construction materias - is there an alternative to EPS foam?
Many thanks,
B.
For example, should I look for;
* a particular shape?
* price?
* brand?
* testing standard?
* construction materias - is there an alternative to EPS foam?
Many thanks,
B.
0
Comments
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Eh? They're all designed to meet the same standards - therefore they should all offer the same minimum level of protection (it's harder to judge how much each specific type exceeds this minimum of course)
You do realise the energy taken to split is taking energy out of your skull - that's the premise on which all of these things work - whether they split or compress is neither here nor there.
Perceived wisdom in terms of testing rigour is, American CPSC is the hardest in terms of impact speed and angles of fall tested, Australian AS standards are essentially the European CE standard with the added bonus of batch testing, rather than just testing that type of helmet. That leaves CE standard as the lowest - lowest impact speed, only testing the helmets upside down (that would be the top of your head landing square on the pavement) and only testing the model of helmet - not each batch.Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0 -
The industry is simply not interested in the relative strengths of helmets which is why they are marketed in other ways - weight, airflow, styling etc.
The big bike mags need to take this up and start doing massive group tests of the top selling helmets to discover which ones work and which do not. Instead all we get is "nice helmet, comfortable with good airflow, but the clip is a little fiddly with gloves on."
Never a single word about the primary function of the helmet.You only need two tools: WD40 and Duck Tape.
If it doesn't move and should, use the WD40.
If it shouldn't move and does, use the tape.0 -
Daz555 wrote:The industry is simply not interested in the relative strengths of helmets which is why they are marketed in other ways - weight, airflow, styling etc.
The big bike mags need to take this up and start doing massive group tests of the top selling helmets to discover which ones work and which do not. Instead all we get is "nice helmet, comfortable with good airflow, but the clip is a little fiddly with gloves on."
Never a single word about the primary function of the helmet.
Would it not be difficult to release figures on the strength of helmets though? I mean, I fully understand that they must meet some standard but the variety of heads that these lids are going to be sat on is a massive variable.
How about this, how many people have cracked there skulls whilst wearing a helmet after they have fallen off?
I'm under the illusion that manufacturers suggest replacing a helmet after you've been in an accident?0 -
TommyEss wrote:Eh? They're all designed to meet the same standards - therefore they should all offer the same minimum level of protection (it's harder to judge how much each specific type exceeds this minimum of course)
No, some brands design (and manufacture) to the Snell standard (e.g. Specialized) which, to my knowledge, is significantly harder to achieve than the basic (e.g. CE) standards; others do not.
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Yep - CPSC (Snell is a foundation - CPSC governs the standards) - I said that further down...Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0
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“Minimal” might not offer much protection.Eh? They're all designed to meet the same standards - therefore they should all offer the same minimum level of protection (it's harder to judge how much each specific type exceeds this minimum of course)
Yes.You do realise the energy taken to split is taking energy out of your skull - that's the premise on which all of these things work
You’ve made three assumptions there:whether they split or compress is neither here nor there.
1) That splitting foam requires the same force as crushing it.
2) That splitting foam reduces deceleration forces to the head the same as compressing it would.
3) That, in the case of a secondary impact (which may be a fraction of a second later), a split helmet still offers as much protection as one that has merely crushed in one spot.
Materials in compression and tension often behave very differently (hence the need for reinforcing bars in concrete). It doesn’t take much strength to snap a piece of foam - in my experience, it’s pretty brittle stuff. Crushing it is another matter.
OK. That’s a useful steer. Thanks.Perceived wisdom in terms of testing rigour is, American CPSC is the hardest in terms of impact speed and angles of fall tested, Australian AS standards are essentially the European CE standard with the added bonus of batch testing, rather than just testing that type of helmet. That leaves CE standard as the lowest - lowest impact speed, only testing the helmets upside down (that would be the top of your head landing square on the pavement) and only testing the model of helmet - not each batch.0 -
Olza23 wrote:Would it not be difficult to release figures on the strength of helmets though? I mean, I fully understand that they must meet some standard but the variety of heads that these lids are going to be sat on is a massive variable.
Like an equivalent Euro NCAP? Nice idea. It would probably push standards up.0 -
It's worth noting that the huge numbers of life-changing injuries and fatalities you get with cars simply do not occur with bicycles, so the impetus for improving the standards of the associated safety equipment is correspondingly much lower. I'm not aware of a single injury where the impact mitigation properties of a helmet has ever been highlighted as a factor.- - - - - - - - - -
On Strava.{/url}0 -
Reading this section of the Wiki page on cycle helmets, it would appear that the OP should look for a lid with a Snell rating for the highest standard of protection. (Interesting that one could easily find such here twenty years ago.)Location: ciderspace0
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Yes, but I think the problem is that Snell is a foundation, as I said, so helmets in the US have to pass CPSC, but Snell is a voluntary submission on the part of the manufacturers - someone else alluded to the fact that it's so hard to find a Snell approved helmet these days, perhaps that's part of the problem?!
Anyway - the main point of my post was that there are a number of different standards, and anything that has passed can only be assumed to have met the minimum requirement - whether it's a £20 halfords jobby or a £200 Sky TdF Kask thing...
The idea that we could have something akin to the EuroNCAP for helmets is interesting, but I reckon we're probably far too small a group of consumers to make that viable - extra testing means extra costs to the manufacturers. Whereas car manufacturers can write this off against sales values, I doubt a helmet manufacturer could.Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0 -
You can look them uphere - there aren't many manufacturers I recognise - Specialized and Limar only... Plus, this is a US thing, so some of these models might not be for sale over here, or if they are, they could be the same model made to a different standard.
I seem to remember something about the Bell Meteor time trial helmet - the European version is a fair few grams heavier than the US model because the testing over here required thicker padding round the full circumference, whereas the US version had trimmed it right back on the sides to get the aero shape they wanted - something like that - anyway, they were very different designs whilst ostensibly "the same helmet".
My point being - if you take one of the Specialized helmets off the list, and buy it in Evans, it's probably been made for the European market only, and it's not clear cut as to whether it's identical to the US Snell approved version, or whether it looks the same, is called the same, but is made in a different batch to different standards...Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0 -
Benthic wrote:
“Minimal” might not offer much protection.Eh? They're all designed to meet the same standards - therefore they should all offer the same minimum level of protection (it's harder to judge how much each specific type exceeds this minimum of course)
Errr, nobody said anything about 'minimal'. FWIW, all safety standards are designed against minimums. It would hardly make any sense for it to be the other way round
TommyEss wrote:My point being - if you take one of the Specialized helmets off the list, and buy it in Evans, it's probably been made for the European market only, and it's not clear cut as to whether it's identical to the US Snell approved version, or whether it looks the same, is called the same, but is made in a different batch to different standards...
Irrc, the Giro Prolight was noticeably heavier in its US version for this reason.Faster than a tent.......0 -
Taken in a very literal sense, yes, I suppose that's correct.Rolf F wrote:Benthic wrote:Eh? They're all designed to meet the same standards - therefore they should all offer the same minimum level of protection (it's harder to judge how much each specific type exceeds this minimum of course)
“Minimal” might not offer much protection.
Errr, nobody said anything about 'minimal'.
My original query was based on various assumptions and crude research methods;
1) Helmets are designed to crush, not crack, to protect the user. [I'm pretty sure this is correct]
2) There are lots of photographs on-line of cracked helmets.
3) I've yet to find a photograph of one that's convincingly crushed.
4) Is there a straightforward way of identifying a model of helmet that wont tend to shatter on impact, i.e. give me greater protection than one that would?
If helmets are tending to crack and yet are still passing laboratory tests then reference to standards might not be the best way to find one. Of course, that in itself may make my query a moot point.0 -
Benthic wrote:My original query was based on various assumptions and crude research methods;
1) Helmets are designed to crush, not crack, to protect the user. [I'm pretty sure this is correct]
2) There are lots of photographs on-line of cracked helmets.
3) I've yet to find a photograph of one that's convincingly crushed.
4) Is there a straightforward way of identifying a model of helmet that wont tend to shatter on impact, i.e. give me greater protection than one that would?
If helmets are tending to crack and yet are still passing laboratory tests then reference to standards might not be the best way to find one. Of course, that in itself may make my query a moot point.
1) Where is this assumption from? Is this something from your head, or is there some reference material we can read to get up to speed on this?
2) In my experience every broken helmet I've seen has cracked - this is how they break to dissipate energy - it's like putting a blow out panel into a building - some parts are strategically weaker to break and remove energy from the system.
3) If your helmet crushed what would stop it crushing into your head and causing you even more damage?
4) No.
The laboratory is testing whether the helmet reduces the accelerative forces on your brain to below a minimum level - the test does not care how this is achieved, so long as the force to the brain is lower than specified. It just so happens that every bike helmet manufacturer on the planet achieves this by having the helmet crack in certain places to dissipate the energy and thus reduce the level of acceleration on your brain?
I would like to think that the engineers at Bell, Lazer, Met etc have done a bit more than crude research into the issue of helmet design and brain injury.Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0 -
If a "broken" helmet has cracked foam, it does not follow that the formation of the cracks is somehow beneficial.TommyEss wrote:1) Where is this assumption from? Is this something from your head, or is there some reference material we can read to get up to speed on this?
2) In my experience every broken helmet I've seen has cracked - this is how they break to dissipate energy - it's like putting a blow out panel into a building - some parts are strategically weaker to break and remove energy from the system.
3) If your helmet crushed what would stop it crushing into your head and causing you even more damage?
E.g. consider: http://bjsportmed.com/content/24/1/55.full.pdf0 -
jejv wrote:
If a "broken" helmet has cracked foam, it does not follow that the formation of the cracks is somehow beneficial.TommyEss wrote:1) Where is this assumption from? Is this something from your head, or is there some reference material we can read to get up to speed on this?
2) In my experience every broken helmet I've seen has cracked - this is how they break to dissipate energy - it's like putting a blow out panel into a building - some parts are strategically weaker to break and remove energy from the system.
3) If your helmet crushed what would stop it crushing into your head and causing you even more damage?
E.g. consider: http://bjsportmed.com/content/24/1/55.full.pdf
Mate - that's far too long and full of jargon for me to get through - can you quote the section you're talking about.
And if it takes energy to break the helmet then that is energy not applied to your brain - that does follow...Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0 -
Yeah, this kind of material is hard for non-specialists - and often hard for specialists. I'm not a specialist either.
The way to go is to read the Abstract at the beginning, then the Conclusions at the end, and then try to make some sense of the hard stuff in the middle. The bits at the ends are supposed to be more accessible.
The bit I was thinking about at is at the start of the conclusions - "Discussion" in this paper:
The idea is to turn the impact energy into heat. A lot of kinetic energy is a small amount of heat.The impact tests on bicycle helmets have been
analysed to show that the main energy absorption
mechanism for impact with a flat surface is the
crushing of the polystyrene foam below the contact
area. Other mechanisms, such as the bending
stiffness of the shell and unyielded liner can be
ignored.
Don't want an elastic helmet.
We talked about helmets before, in this thread: viewtopic.php?f=40012&t=12726815
But you shouldn't believe me on the basis of one paper! Be skeptical!
Googling around will turn a bit more stuff about energy absorption in bike helmets.0 -
Cheers for that - I'm a chemical engineer, not materials or mechanical - so there's lots of stuff in there that rings faint bells from high school physics but also a lot of blanks. It is certainly an interesting discussion though.
I got confused because it started off talking about bicycle helmets, then I saw a Nolan listed as one of the test subjects, which I'm pretty sure make exclusively motor bike helmets - so that seemed weird...
As for the bit you've highlighted - when they talk about the shell I take it that they mean the thin stuff that's got the pretty pattern on it - I don't think anyone considers that structurally integral to the helmet - it's for decoration, and to provide a bit of bash protection from door frames - the day to day knocks that could otherwise chip away at the important material underneath. To me, that's all that statement says.
Now, as for the bit above, crushing, which is what the OP was trying to say was so different to cracking - well I started writing out a long response, tied myself in knots then had a bit of an epiphany!
I think you're right - I wrote a bit about current helmets being the best compromise - safety/cost/style/weight/ease of manufacture etc are all combined - of course it's not the safest helmet - we have motorbike helmets which offer far greater protection - but they're too heavy, expensive and hot to ride in - so we don't use them - we compromise. (There's nothing wrong with that - it's just the way it is)
But what we really need is a means to offer a more gentle deceleration within the same distance - i.e. the same helmet thickness, so we don't have to compromise on style and weight - and end up with big mushroom helmets - cyclists like the sleek and aero aspects of their helmets.
Team GB's magic Olympic helmets are made with an aluminium honeycomb structure - they obviously still have to pass a minimum safety standard to be approved by the UCI for use (so I believe must be at least EN, which we know is pretty crappy, but it's something) but that's keeping weight down and providing a crumple-zone if you like around the skull.
Doesn't sound particularly cheap - but that could be something worth looking at. I know materials science is coming a long way - it's not beyond the realms of possibility to manufacture something out of carbon fibre to have the give in the right direction to deform on impact - again - costly now - but carbon fibre frames were out of all of our reach 10-15 years ago... Not sure about the carbon fibres dusting as your bonce scrapes the pavement, mind...! But then again the right resin and protective outer shell could possibly sort that for the majority of impacts.
I'll admit to struggling during my thermodynamic lectures, but I'm pretty sure the only real conversion of kinetic to thermal energy is due to friction. What we have in current helmets is an inelastic collision, with the kinetic converted to heat, sound and binding energy (breaking the helmet apart). Of these, heat is a small part - I don't remember taking my helmet off post-crash and burning my fingers or seeing it smouldering, but it did make an almighty "thwack" and broke into a number of parts!
Anyway - how long until we all get Team GB helmets then? Is aluminium honeycomb the future?Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0 -
Benthic wrote:
Taken in a very literal sense, yes, I suppose that's correct.Rolf F wrote:Errr, nobody said anything about 'minimal'.
No - not very literal - any sense. The difference between minimal and minimum is enormous. Minimal here implies not much protection. A minimum standard could be a full enclosed motorbike style helmet or it could be a paper bag over your head - it depends entirely on the standard used. So maybe in Guatemala the minimum standard for helmet might indeed offer minimal protection, in the USA the minimum standard would be much higher (and certainly offering rather more than "minimal" protection).
As for Team GB - those helmets are track only. On the road they use almost standard Kask Mojitos mostly (they tend to differ from standard by leaving off one part of the shell presumably to save weight).Faster than a tent.......0 -
Daz555 wrote:The big bike mags need to take this up and start doing massive group tests of the top selling helmets to discover which ones work and which do not. Instead all we get is "nice helmet, comfortable with good airflow, but the clip is a little fiddly with gloves on."
Never a single word about the primary function of the helmet.
Doing this in any remotely meaningful way is way, way beyond what a bike magazine could do.
Anyhoo, slightly OT but I've read in a couple of places it's wise to go for rounder ones rather than ones with lots of pointy bits that could dig in to the ground. Personally though I find it hard to believe the pointy bits on lids are sturdy enough to cause problems that way.0 -
The motorcycle press manage it.MrChuck wrote:Daz555 wrote:The big bike mags need to take this up and start doing massive group tests of the top selling helmets to discover which ones work and which do not. Instead all we get is "nice helmet, comfortable with good airflow, but the clip is a little fiddly with gloves on."
Never a single word about the primary function of the helmet.
Doing this in any remotely meaningful way is way, way beyond what a bike magazine could do.
Anyhoo, slightly OT but I've read in a couple of places it's wise to go for rounder ones rather than ones with lots of pointy bits that could dig in to the ground. Personally though I find it hard to believe the pointy bits on lids are sturdy enough to cause problems that way.You only need two tools: WD40 and Duck Tape.
If it doesn't move and should, use the WD40.
If it shouldn't move and does, use the tape.0 -
Daz555 wrote:
The motorcycle press manage it.MrChuck wrote:Daz555 wrote:The big bike mags need to take this up and start doing massive group tests of the top selling helmets to discover which ones work and which do not. Instead all we get is "nice helmet, comfortable with good airflow, but the clip is a little fiddly with gloves on."
Never a single word about the primary function of the helmet.
Doing this in any remotely meaningful way is way, way beyond what a bike magazine could do.
Anyhoo, slightly OT but I've read in a couple of places it's wise to go for rounder ones rather than ones with lots of pointy bits that could dig in to the ground. Personally though I find it hard to believe the pointy bits on lids are sturdy enough to cause problems that way.
Do they? Got any links?
Genuine question- I'd have thought that commissioning a proper study on these things would take a lot of time and money that mags don't really have.0 -
Benthie,
Tried to answer your questions below - some from reading/theory and some from practical experience (personally tested two helmets to failure through losing the front wheel on diesel...):
My original query was based on various assumptions and crude research methods;
1) Helmets are designed to crush, not crack, to protect the user. [I'm pretty sure this is correct]
Yes, correct. That said, in the two heavy impacts that I have experienced, the foam compressed and crushed but also cracked - I think there is a limit to the crushability before the foam factures. It definitely crushed though. Both failure modes will dissipate energy.
2) There are lots of photographs on-line of cracked helmets.
I think this may be related to my answer above. Also worth saying that modern helmets typically have the foam bonded to a plastic shell. This shell tends to keep the cracked foam together and provid some secondary protection (particularly if your helmet doesnt strike the same exact point again. In my two "tests" there were very small tears in the shell but the helmets stayed in one piece. I didnt have a secondary impact though.
3) I've yet to find a photograph of one that's convincingly crushed.
Probably less visible than the crack? The crushing tends to be quite localised.
4) Is there a straightforward way of identifying a model of helmet that wont tend to shatter on impact, i.e. give me greater protection than one that would?
All the literature seems to suggest that US standards are higher. That said my two EU standard helmets (low-mid range Giro and Bell) did what they were supposed to. I whacked my head on the tarmac and got away with a very minor headache that was gone in an hour.0 -
Sensible answers. Interesting discussion. Cheers.0
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Bit of reading around the whole crushing issue, would suggest that the test heads are steel, and so act on the helmet differently to a human head (which typically "gives" a bit during the impact).
So that would suggest that they get the crush during the testing, but not in real world accidents - so that would imply a flaw in the testing. Anecdotally to pass the test with the steel headform the manufacturers end up needing stiffer foam, which gives even less in real world impacts - that would probably be a big part of what you're seeing in post-crash helmets - a little bit of crushing, but essentially fractured into a few sizeable chunks.
Given the amount of technology that goes into Crash Test Dummies for the motor industry, it's a shame that helmets are tested with a lump of metal with an accelerometer embedded.Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0 -
Snell actually test (well break probably) the helmets in various test. This costs money and they bill the manufacturers for the lab time.
The Specialized helmet I bought went through this.0 -
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All the approval bodies test helmets in this way - but the regulations stipulate varying impact speeds, head-form weights and angle of impact. One key key difference between the US and European testing and the Aussie/Kiwi testing is that US and Europe perform the tests on each new model of helmet therefore effectively approve a design and production method, whereas the Aussie's test every batch if helmets, which theoretically should maintain the standard of a helmet throughout its production lifetime. There are of course many other quality control steps employed throughout the industry, but batch testing is rare since it's expensive (and not compulsory for most markets).Cannondale Synapse 105, Giant Defy 3, Giant Omnium, Giant Trance X2, EMC R1.0, Ridgeback Platinum, On One Il Pompino...0
