The Science of Cycle Helmet Safety

This sub-forum all discussions about this "lively" subject. All topics that are substantially about helmets will be moved here, if not placed here correctly in the first place.
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mjr
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Re: If there is a multi impact helmet?

Postby mjr » 18 Jan 2019, 12:32pm

jack1992 wrote:Thankyou- just looked through their website very interesting!, from what they are saying it is being distributed soon! are you getting one?

No. I don't use a helmet any more since one injured my neck and then I looked at the evidence about them :shock:
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Cunobelin
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Re: If there is a multi impact helmet?

Postby Cunobelin » 18 Jan 2019, 12:37pm

irc wrote:
jack1992 wrote:I know helmets have came on leaps and bounds


Really? I thought the helmet test they are built to hadn't changed in years. I thought helmet design was mostly fashion, maybe better ventilation and comfort, but I've never seen any maker claiming their helmet was any safer than any other helmet.

In fact I wojuldn't be surprised if any advances had been used to make helmets to pass the existing test lighter rather than keeping the weight the same but giving protection that exceeded the test.

For an item pushed hard by many people on safety grounds there is little evidence of any attempts to make them safer.


Controversial...

Arguably by decreasing the amount of absorbent material by increasing ventilation, the helmet can absorb less energy and is therefore less effective

The remaining material needs to be stiffer and denser to support the shape and structure, again reducing the ability to absorb energy (Specialized did experiment with two Laye foam for this reason.)

The new helmets also have a problem where these bridges are a weak point (even with the increasing use of carbon fibre cages and tend to fail on impact

A classic example or two:

Image

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jack1992
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Re: Is there a multi impact helmet?

Postby jack1992 » 18 Jan 2019, 1:17pm

I guess this is where the company called Hedkayse are going.. saying their helmet does not crack etc, £150 for the helmet though?... would you pay for this if it was bang on the money with what they are saying
Jack1992 is a Support Mangler for Hedkayse. Please treat this post with the contempt it deserves.

thelawnet
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Re: Is there a multi impact helmet?

Postby thelawnet » 18 Jan 2019, 1:43pm

Cugel makes a fair point - while a bike with a crack or fracture or dodgy carbon could snap and kill you, so if you drop your £10k bike on the floor it might be as well to throw it away, but a helmet with a crack in it cannot necessarily said to have failed or to be useless. For example , if you keep the packaging from your new TV it will likely include some similar compressible polystyrene, and if it got damaged during unpacking it would still be usable and useful if you wanted to package the TV up in future, so in this sense it seems rather silly to suggest that any sort of impact should render a helmet 'broken'.

Apparently the shell is supposed to transmit forces throughout the structure of the helmet . I am not sure if cracks or whatever would in fact stop that.

jack1992
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Re: Is there a multi impact helmet?

Postby jack1992 » 18 Jan 2019, 1:50pm

thelawnet wrote:Cugel makes a fair point - while a bike with a crack or fracture or dodgy carbon could snap and kill you, so if you drop your £10k bike on the floor it might be as well to throw it away, but a helmet with a crack in it cannot necessarily said to have failed or to be useless. For example , if you keep the packaging from your new TV it will likely include some similar compressible polystyrene, and if it got damaged during unpacking it would still be usable and useful if you wanted to package the TV up in future, so in this sense it seems rather silly to suggest that any sort of impact should render a helmet 'broken'.

Apparently the shell is supposed to transmit forces throughout the structure of the helmet . I am not sure if cracks or whatever would in fact stop that.



It is a very fair point considering when you buy delicate products there is always polystyrene, looking into it more one how there material works it seems to reconstruct it self, if you have time watch some of their videos, on testing their helmet to a regular one the results are interesting- i know testing some times does not reflect a crash
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scottg
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Re: If there is a multi impact helmet?

Postby scottg » 18 Jan 2019, 1:55pm

irc wrote:Really? I thought the helmet test they are built to hadn't changed in years. I thought helmet design was mostly fashion, maybe better ventilation and comfort, but I've never seen any maker claiming their helmet was any safer than any other helmet.


There is independent testing of helmets, including bike helmets.
All the helmets are CPSC approved, the testing goes beyond CPSC
and has individual helmet ratings. US centric list.
None are multi impact.

https://www.helmet.beam.vt.edu/bicycle- ... tings.html
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Brucey
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Re: Is there a multi impact helmet?

Postby Brucey » 18 Jan 2019, 2:02pm

as others have said most helmets absorb impact by crushing the polystyrene. This is rarely accomplished without any cracking. The purpose of the outer shell is to both hold the pieces together and to allow the helmet to slide on most impacting surfaces rather than snag on it (which might well cause a neck injury). The straps also help hold everything together and onto your head; it is currently popular to arrange the straps differently to this but straps that loop over substantial bits of the polystyrene seem to work very well.

Perhaps most importantly with this type you can see if the whole helmet is compromised or not, whereas if the strap disappears into the polystyrene, possibly attached to some kind of internal structure that you cannot see, there is no way of knowing if that is just about to fall apart or not.

FWIW helmets are a lot cheaper than heads are; binning a £15 'daily use' helmet after a few years/knocks is no big deal. Years ago helmets were more expensive and I didn't have two beans to rub together; thus when I broke a helmet I did once patch it up. It was an early microshell helmet. The polystyrene was slightly crushed in once place, cracked through in some other places, and the microshell was cracked in one or two spots.

I reasoned that the crushing wasn't too bad ( about 85% of the original thickness remained) and probably another impact wouldn't occur in the same place anyway. The cracked polystyrene pieces I glued back together using PVA glue. The cracked microshell was 'repaired' using self adhesive tape. I only had to tape around the edges of the microshell (it was taped at this point from new, I just used wider tape) but I'd have happily run duct tape over parts of the shell if the cracks had been more extensive. Probably taping the microshell is a good idea anyway (provided the adhesive doesn't attack and weaken the plastic); if the shell itself cracks a reinforced tape will hold it together.

I used this helmet for run-of-the-mill uses for some time after it had been 'repaired'; I didn't mind leaving it locked to the bike etc because I figured that it owed me nothing. I didn't have cause to 'test it' but it stayed in one piece as well or better than it would have otherwise.

I am pretty sure that the PVA glue poses no problems; to test this I broke pieces of polystyrene, glued them back together and broke them again. They never broke again at the glue line. If I wanted to improve such a helmet (where the microshell wasn't 100% bonded to the top) I'd probably excavate grooves in the outside of the polystyrene shell and glue nylon shot cord into the grooves and then replace the microshell; this would hold the helmet together better than the microshell alone. More modern helmets have the microshell bonded all over so I don't think you could do quite the same thing.

If you want a helmet that will take daily knocks, (and don't mind the extra weight not to mention the looks of the thing), there is something to be said for a hardshell helmet. Skateboard helmets, the Old Bell V1, and some others are like this. Basically if the shell isn't cracked, the polystyrene liner is in more or less one piece, and the straps are still secure, the helmet ought to work OK. With a lot of more modern helmets they are damaged more easily and you can't inspect them so easily.

cheers
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Mick F
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Re: Is there a multi impact helmet?

Postby Mick F » 18 Jan 2019, 4:36pm

I've banged my head many times over the years, but I've never needed to replace it.
Had I banged my helmet, it would need to be ditched and a new one bought.
Mick F. Cornwall

pete75
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Re: Is there a multi impact helmet?

Postby pete75 » 18 Jan 2019, 6:32pm

jack1992 wrote:I am looking for a multi impact helmet, i know helmets have came on leaps and bounds, so just wondering if there is anything out there which can take the crashes more then once- as i know it is recommended to replace once you've had a crash


How can any manufacturer claim their helmet can withstand multiple impacts when they have no knowledge of the severity of any impact that helmet sustains in use?

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Re: If there is a multi impact helmet?

Postby Cyril Haearn » 18 Jan 2019, 6:44pm

100%JR wrote:Oh dear.
Rearrange these words.
Worms,of,open,can :wink:

The human body has evolved over millions of years, could anyone have designed it, could one do better than nature? Maybe the human skull is a perfectly designed/evolved h****t :wink:

'Can worms open cans' is my offer, do I win a prize?
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Airsporter1st
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Re: Is there a multi impact helmet?

Postby Airsporter1st » 18 Jan 2019, 7:17pm

I think the main advantage of ensuring a helmet is always replaced after even the slightest impact is increased sales.

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Re: Is there a multi impact helmet?

Postby Cyril Haearn » 18 Jan 2019, 7:52pm

Airsporter1st wrote:I think the main advantage of ensuring a helmet is always replaced after even the slightest impact is increased sales.

I b€t mo$t of u$ agr€€ with that :?
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Pete Owens
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Re: Is there a multi impact helmet?

Postby Pete Owens » 18 Jan 2019, 11:37pm

This seems to be a curious enquiry.

How frequently do you anticipate banging your head?

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Mick F
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Re: Is there a multi impact helmet?

Postby Mick F » 19 Jan 2019, 6:58am

Airsporter1st wrote:I think the main advantage of ensuring a helmet is always replaced after even the slightest impact is increased sales.

Spot on.

They won't be getting any more money from me. I saw the light, and stopped wearing one in 2015.
Mick F. Cornwall

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pjclinch
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Re: Is there a multi impact helmet?

Postby pjclinch » 19 Jan 2019, 10:39am

pete75 wrote:
jack1992 wrote:I am looking for a multi impact helmet, i know helmets have came on leaps and bounds, so just wondering if there is anything out there which can take the crashes more then once- as i know it is recommended to replace once you've had a crash


How can any manufacturer claim their helmet can withstand multiple impacts when they have no knowledge of the severity of any impact that helmet sustains in use?


By having some Fine Print under the claim about what values of "Impact" they mean. My camera is "waterproof" and "shockproof", but if I look at the small print it turns out while they're happy to say if I do up the seals properly it will cope with immersion up to 2.5m they won't make that level of claim about dropping it.
My guess would be along the lines of an "impact" being the kind an EN1078 certification says will be dealt with without the helmet failing catastrophically.

The legal departments concerned will have gone over it with a fine toothed comb to make sure there's no basis for getting sued. I strongly suspect that's why e.g. claims of life-saving never come from advertising by helmet manufacturers.

Pete.
Often seen riding a bike around Dundee...