Safer cycling? Don't get a helmet and cross red light

[Cyclezee]

Time for bit of positive lateral thinking about accidents

Without accidents, disease, famine, natural disasters, wars etc., more people would live longer and the world would be even more densely populated than it already is.

Because of the increasing human lifespan, elderly care which is already a ticking time bomb would explode even sooner.

Pension funds and state benefits which are already strained would not be able to cope.

Plus there would be a loss of income and employment for those whose job it is to deal with every aspect of an accident.

I rest my case.........where someone will probably trip over it

Not Tillson and Flecc of course

 

[flecc]

Your argument falls down on one simple fact John, the high number of births which are accidents, being an unintentional by-product of pleasure seeking.

Without all those accidents, the world's population would not be out of control.
.

 

[Cyclezee]

Your argument falls down on one simple fact John, the high number of births which are accidents, being an unintentional by-product of pleasure seeking.

Without all those accidents, the world's population would not be out of control.
.

So you are in favour of at least one form of personal protective equipment

 

[flecc]

So you are in favour of at least one form of personal protective equipment

If something is at least 99% effective and the alternative is a very high risk of the "accident", it's a sensible choice for those who wish to use it.

But cycle helmets are not remotely as effective and the alternative is not a very high risk of an accident. Every study has shown that the alternative is often a slightly lower chance of an accident.

The circumstances are not in any way comparable.

 

[Daz Marshall]

Daz Marshall, I'm afraid that you have fallen victim to cycle helmet manufacturer's propagander.

I don't know which type of cycle helmets you have owned or examined, but every single one that I have seen is manufactured from a dense type of polystyrene which possesses nothing like sufficient compressibility to prevent dangerously high levels of g force in the event of an impact. I've never owned a motorbike helmet, so can't say how it is constructed. I do however use an aviation flying helmet which has a carbon fibre outer shell and about 65 mm of soft foam padding on the inside. This is what I'd expect to have in order to reduce impact g forces, and to suggest that a cycle helmet compresses similarly is laughable. I suspect that the material choice used for cycle helmets has everything to do with economies of manufacture and profit margins, with effectiveness languishing in third place or lower. You will see from my calculations earlier in this thread that even if the polystyrene could compress 5mm, which I doubt that it can, the g force on the brain at just 20 MPH is 580 g, which is going to kill you or leave you with a serious brain injury (Interesting that the propaganda which you linked to uses 10 MPH).

Don't confuse the polystyrene shell of a bicycle helmet with the sponge type lining found inside a motor cycle helmet (which I suspect is constructed in a similar way to a flying helmet). That sponge inside the motor cycle helmet is many times more compressible than the cycle helmet polystyrene and it is that greater compressibility which gives the protection against high g, and hence brain injury. That is why I carried out the same calculation with an assumed 50mm of compression. This reduces the g load from 580 g when wearing a cycle helmet to 80 g when wearing a motorcycle helmet (when impacting at 20 MPH).

I'm not denying that a cycle helmet may reduce the effect of a point load, but as far as brain damaging acceleration forces are concerned, they are next to useless.

It's easy to dredge up hog wash from the internet which is sponsored by groups a with vested interest. Try not to be so gullible. Instead rely on facts and learn a bit of basic science and mechanics, it does wonders for your understanding of how things work.

Wow, some people will just never admit when they're wrong, will they.

ALL motorcycle and motorsport helmets are constructed the same basic way. The compression substance has to be as shockingly hard to compress as polystyrene obviously feels to you do to the immense forces they're trying to deal with over very short times. As you know the greater the rate of change of acceleration the greater the force so all this layer tries to do is make the deceleration occur over a longer period of time, just like a seat belt and air bag (and, indeed crumple zones on the car itself). A soft piece of foam would compress almost instantaneously and provide almost no change in the rate of deceleration and thus no change in the forces felt on the skull.

You crack me up, you honestly think bicycle helmet manufacturers would make the polystyrene layer of the helmet so thick and the (should I say it - comfort) foam inserts so thin if it was the (comfort) foam inserts that did the job of lowering the g-forces felt on the head? Bonkers.

But anyway, you're obviously right so I really think you should get in touch with all the manufacturers and tell them how wrong they are and they should use some soft foam that will work much much better.

When will I learn to never argue with someone on the internet. Someone stop me please

 

[tillson]

I

Wow, some people will just never admit when they're wrong, will they.

ALL motorcycle and motorsport helmets are constructed the same basic way. The compression substance has to be as shockingly hard to compress as polystyrene obviously feels to you do to the immense forces they're trying to deal with over very short times. As you know the greater the rate of change of acceleration the greater the force so all this layer tries to do is make the deceleration occur over a longer period of time, just like a seat belt and air bag (and, indeed crumple zones on the car itself). A soft piece of foam would compress almost instantaneously and provide almost no change in the rate of deceleration and thus no change in the forces felt on the skull.

You crack me up, you honestly think bicycle helmet manufacturers would make the polystyrene layer of the helmet so thick and the (should I say it - comfort) foam inserts so thin if it was the (comfort) foam inserts that did the job of lowering the g-forces felt on the head? Bonkers.

But anyway, you're obviously right so I really think you should get in touch with all the manufacturers and tell them how wrong they are and they should use some soft foam that will work much much better.

When will I learn to never argue with someone on the internet. Someone stop me please

I think that we are in agreement that a helmet needs a compressible layer of material so that in the event of the head hitting something, the material will compress thus reducing the acceleration to which the brain is subjected. What we dont agree on is how much a polystyrene bike helmet will compress.

I have shown that at just 20 mph, the helmet would need to compress 50 mm in order to reduce the g load to 80 g. I don't think that the polystyrene used in cycle helmets will do that.

I've just pulled my Alpha flight helmet to pieces and there is no trace of any polystyrene inside it, just a fairly high density polyurethane foam. From both my calculations and experience, this is exactly what I would expect to find in such a piece of protective equipment. I would have been horrified to find polystyrene because it would have severely reduced the amount of protection.

I think I'll leave it there because we will never agree.

 

[flecc]

I've just pulled my Alpha flight helmet to pieces and there is no trace of any polystyrene inside it, just a fairly high density polyurethane foam. From both my calculations and experience, this is exactly what I would expect to find in such a piece of protective equipment. I would have been horrified to find polystyrene because it would have severely reduced the amount of protection.

Just like that in my motorcycle helmet, nothing like cycle helmet construction.

 

[Deleted member 4366]

My Motorcycle helmets are more or less all the same as each other. There's an outer shell of GRP or kevlar with an inner liner of expanded polystyrene, which is covered in a thin cloth stuff. The only foam padding is round where your cheeks are and around the bottom to keep the draught out.

 

[drsolly]

Experimental evidence is clearly required. Now where did I put that anvil ...

 

[Daz Marshall]

I



I think I'll leave it there because we will never agree.

I know.

 

[Daz Marshall]

Just like that in my motorcycle helmet, nothing like cycle helmet construction.

I'd imagine it's an old helmet flecc?

 

[Deleted member 4366]

Is it a pudding bowl shape with a cork liner and leather ear-flaps?

 

[flecc]

Nope, Shoei mid 1990s full-face, can't remember the model. There's a thin layer of expanded polystyrene in the crown area at the top but the all over thick layer over my head is expanded polyurethane.

I was forced to wear the old all-steel and leather strapped ACU helmet in my army days as a member of a m/c team, but hated the thing.

 

[flecc]

Adding to the above, I'm surprised at the insistence of them having all polystyrene inside. When I bought the Shoei I remember some had strapping support. I can't remember it precisely, but it amounted to a steel ring at the crown with straps from there to the perimeter but can't remember how they terminated. Basically that support gave an airspace between the web of straps to the helmet shell.

I wasn't interested in the protection since I had no intention of starting to bounce my head on the road, so I chose only on comfort. The old one before it was comfortable but age made it unhygenic (i.e. it stank!)

No longer use the helmet though, sold my last motorbike a few years ago.

 

[Deleted member 4366]

That's strange. I've just checked all 6 of mine that run from the '70s to recent. They're all expanded polystyrene.

 

[tillson]

Adding to the above, I'm surprised at the insistence of them having all polystyrene inside.

This surprises me too and I've never seen it. The polystyrene must be the very low density variety such as that used in underfloor insulation or the backing on insulated plaster board. That density of polystyrene poseses virtually no structural rigidity and crumbles or breaks easily when handled, but it is quite sponge like to the touch. This characteristic would present no problem when contained within the comparatively heavy and structurally rigid shell of a motor bike helmet. It wouldn't be at all suitable for cycle helmets because it would break up too easily. I imagine this is the reason why cycle helmets are made from the higher density, more structurally rigid variety. The downside being very little compression available which severely reduces its effectiveness to near zero.

I think I'll stick to concentrating my efforts on accident avoidance too. The plecebo effect of straping high density polystyrene to the head may work for some and it certainly works for the manufacturer's pockets, but it just keeps my head warm.

 

[Deleted member 4366]

I just found this too that says Shoei helmets have an expanded polystyrene liner.
http://www.shoei-helmets.com/safety_insideshoeihelmet.aspx

 

[Deleted member 4366]

This surprises me too and I've never seen it. The polystyrene must be the very low density variety such as that used in underfloor insulation or the backing on insulated plaster board. That density of polystyrene poseses virtually no structural rigidity and crumbles or breaks easily when handled, but it is quite sponge like to the touch. It wouldn't be at all suitable for cycle helmets because it would break up too easily. I imagine this is the reason why cycle helmets are made from the higher density, more structurally rigid variety. The downside being very little compression available which severely reduces its effectiveness to near zero.

Sorry Tilson, but that's totally not true. I've got the liner out of one of my motorcycle helmets and I'm comparing it with my cycle one. It's the same stuff and the same density. I used to work in an expanded polystyrene moulding factory (Ball Plastics, Billericay) that actually made motorcycle helmet liners in 1971. The density is around 4 to 6 pounds per cubic foot. Polystyrene for shuttering is about one pound per cubic foot.

 

[Deleted member 4366]

Some interesting reading here, which mentions that most expanded polyurethane is produced in Taiwan because of toxic waste:

http://www.helmets.org/liners.htm

 

[flecc]

Having not looked at any since the mid 1990s I'm too out of date to comment on the current construction. But I did see there were at least three different ways of building the interiors in the 1990s, trying them on for comparative comfort before settling on my two materials one.