Nice quote.

[jonesy]

That is an appealing argument but it does not stand up to scrutiny. A CE marked helmet is designed to withstand a single impact of 50 Joules energy. It is not expected to provide any protection in subsequent impacts. Indeed, the bulk of the helmet means that subsequent head impacts are more likely. A high speed crash will often result in such multiple head impacts. A helmet quite simply cannot be expected to provide meaningful protection in this case, and it is disingenious to suggest otherwise.

'Disingenuous'? I hope you aren't implying that I was trying to mislead anyone!

A helmet cannot be expected to provide protection at any speed, my point is simply that whatever protection it may provide will be highly dependent on the individual circumstances of the collision and doesn't simply vanish completely at an arbitrary cut-off point corresponding to the test speed.

 

[srw]

A CE marked helmet is designed to withstand a single impact of 50 Joules energy.

No - it is tested to withstand a single impact of that level. That's not at all the same thing, and says nothing at all about multiple impacts or bigger impacts. The argument is often made that therefore there is no protection above that impact level. That is a logical fallacy.

 

[screenman]

I must say I prefer to listen to the Doctor rather than somebody who has no qualifications.

Now when it comes to helmets we each consider the opponent an idiot and you know what they say about arguing with one of them.

 

[ufkacbln]

That is an appealing argument but it does not stand up to scrutiny. A CE marked helmet is designed to withstand a single impact of 50 Joules energy. It is not expected to provide any protection in subsequent impacts. Indeed, the bulk of the helmet means that subsequent head impacts are more likely. A high speed crash will often result in such multiple head impacts. A helmet quite simply cannot be expected to provide meaningful protection in this case, and it is disingenious to suggest otherwise.

A CE marked helmet is banned from competition in the US due to the paltry protection it offers!

 

[Wobblers]

'Disingenuous'? I hope you aren't implying that I was trying to mislead anyone!

A helmet cannot be expected to provide protection at any speed, my point is simply that whatever protection it may provide will be highly dependent on the individual circumstances of the collision and doesn't simply vanish completely at an arbitrary cut-off point corresponding to the test speed.

You're right: "disingenious" is far too strong a word. I'm not suggesting that you would deliberately try to mislead anyone. Re-reading my post does suggimply that, for which I can only apologise.

 

[Wobblers]

No - it is tested to withstand a single impact of that level. That's not at all the same thing, and says nothing at all about multiple impacts or bigger impacts. The argument is often made that therefore there is no protection above that impact level. That is a logical fallacy.

No. It cannot be expected to withstand a greater load. It is unreasonable to expect it to be able to cope with higher impact loads.The steel that makes up a bridge is specified to fail at a particular ultimate tensile load - you cannot expect it not to fail if you overload it, which is why civil engineers overdesign their structures to introduce a safety factor. Likewise, a crane has a maximum safe working load, which you must not exceed. Yes, it may cope with a larger load, but that's not guaranteed. It is extremely unwise to rely on an unspecified safety factor to maintain your own protection. You do not know what will happen to a structure, any structure, once you've exceeded its tested load. This is why engineers spend so much effort to ensure these limits are not exceeded - and any that didn't would find themselves prosecuted for malpractice.

It's important to understand the mechanism a helmet uses to dissipate that energy. They do so destructively, in a manner analogous to the way that a dropped mug will dissipate its impact energy by shattering. This is entirely a one shot deal. The structural integrity of areas even distal from the impact site can be expected to be disrupted sufficiently to markedly reduce their impact resistance. A helmet that has sustained one 50 J impact is not guaranteed, and it is unreasonable to expect considering the materials science, to provide meaningful protection in any subsequent impact.

Edit: and the failure mode at high impact energies is frequently different than that at lower energies. Typically, you'll see rapid crack propogation rather than localised crushing and microcracking. This failure mode absorbs very little energy indeed. It is unwise to rely on gaining any benefit at all in these circumstances.

 

[DRHysted]

A CE marked helmet is banned from competition in the US due to the paltry protection it offers!

When I got the road bike I got a helmet because I thought it would help as I expected (correctly) my speed would increase. I was concerned when the helmet had a warning not to cycle at speed when using the helmet!!
I still wear it as it may help, although earlier in the year when we were getting temperatures of 34C I did stop using it in the mountains of Scotland as the ventilation wasn't good enough and I was overheating going up the hills (in 1st gear).

I honestly don't know who is right and wrong, but I would not like to see it as a fineable item, because then, like cars, we would become a good source of income. Be warned we will still at some point in the future become a source of income, probably at the point that only the rich drive cars.

 

[Hawk]

...

Interesting, thanks for that.

However, we don't know at which point precisely the failure mode changes so it's as unwise to suggest that we can't rely on them as it is to suggest that we can?

Presumably a fracture during impact at the helmet's rated speeds would mean the helmets do not absorb enough energy to pass the required standard, which might well be costly for manufacturers. As such, are these helmets built in with a safety factor?

Additionally, would it be fair to suggest that the first head impact would tend to be most severe and any further impact would likely be less so?

I feel you are being quite reserved in not over-stating the real truth of the materials science behind helmets; are you merely against the blind faith that many have in helmets or do you think there is a good reason to avoid wearing one?

One argument commonly brought up is that helmets increase the risk of rotational/strain injuries to the neck. The weight of a human head being around 4-5kg, compared with that of a helmet (250g for mine, maybe a bit more for cheap £20 shells though), seems to make this quite unlikely. Do you have an opinion on this?

Many thanks mate

 

[screenman]

Chief doctor, they interviewed him for Cycling Weekly recently.

 

[ufkacbln]

I must say I prefer to listen to the Doctor rather than somebody who has no qualifications.

Excellent...

So if a Doctor like John Heyworth, President of the British Association for Accident and Emergency Medicine were to professionally endorse helmet, we should unequivocally accept that endorsement without question and wear it?

 

[screenman]

This particular Doctor has been involved with and traveled with cycle races for over 20 years, and has taken notice of what has happened since the introduction of the cycle helmet in racing accidents. Whilst most people who say helmets offer little protection on this forum have done what?

 

[screenman]

Yes.

 

[ufkacbln]

Yes.

So why believe that partricular Doctor, and not the ones that spent the time and effort listing, processing an analysing accidents over a ten year period and showed him to be wrong?

Are they lying, less qualified than him?

Which brings us back to John Heyworth, President of the British Association for Accident and Emergency Medicine. If he were to professionally endorse helmets, should we unequivocally accept that endorsement without question and wear it?

 

[screenman]

On the road experience counts for nothing in your eye's I suppose.

 

[ufkacbln]

On the road experience counts for nothing in your eye's I suppose.

Which is exactly what the paper I quoted was all about!

Recorded on the road experience of cyclists shows that fractures are a minority, and that knees and others are more common than clavicles

On the road experience shows that the honourable gentle man is wrong in his claims!