Paper Helmets

[marzjennings]

So what do you think they are tested for ?

Not speed or forward momentum. Tests are generally a vertical drop to a flat, edged or angled surface with no horizontal movement at all.

 

[Linford]

Not speed or forward momentum. Tests are generally a vertical drop to a flat, edged or angled surface with no horizontal movement at all.

So what forces do you think are in play with this rig ?

 

[User482]

There is a reasonable view that every helmet worn promotes helmets and brings the prospect of compulsion closer.

What about other pieces of safety equipment?

 

[Linford]

[QUOTE 2875074, member: 45"]Impact speed.[/quote]


It is a bit more than that. It is the value/weight of the momentum at the point of impact. A 20 stone cyclist is goign to do a lot more damage to his head at 20mph than 10mph because his momentum is a multiple of his mass against his velocity.

When you look at it the other way. double the speed (velocity) and halve the weight of the rider give the same value.

It doesn't matter which way the rig is facing provided they have calculated and allowed for the difference.

 

[Linford]

I thought you were an expert on the Snell standard and testing regime, Linford. Surely you should know the answer?

You are getting me confused with Cunobelin who cited that he would consider this helmet if it conformed to Snell B95 testing standards.

Ultimately the function of a helmet is to reduce the amount of energy at point of impact from being transfered to its contents. All a test does is determine if the helmet meets the 'pass'' criteria, not whether it exceeds it or by what margin.

 

[Linford]

Momentum and kinetic energy are not the same..

Perhaps you'd like to explain to the class what the differences are Adrian ?

 

[User482]

Not an issue I have thought about to be honest. It's not as though you read stories about insurance companies arguing reduced compensation for no elbow pads.

http://www.telegraph.co.uk/news/ukn...-multi-million-pound-compensation-battle.html

Do you think a cyclist or pedestrian wearing a hi-vis jacket promotes them and brings the prospect of compulsion closer?

 

[User482]

I wasn't thinking about Hiviz because I prefer not to but yes, most probably,

So we shouldn't use any type of safety equipment, in case it becomes compulsory?

Personally, I don't see attempts by insurers to mitigate their losses as closely linked to compulsion.

 

[User482]

Sounds reasonable to me, at least for any that you wouldn't want to be compulsory.

What if you think that the particular piece of equipment offers a safety benefit?

 

[Dan B]

[QUOTE 2874565, member: 45"]Remember that helmets are tested on speed of impact. This is not the same as travelling speed prior to incident.[/quote]
I speculate that if you're impacting a flat horizontal surface, the vertical component of travelling speed prior to impact is usually zero or thereabouts: you might sand all the hair and skin off your skull as you slow down, but a 300G impact doesn't seem all that likely. OTOH if you slide into a kerb at high speed, brain damage is probably back on the menu. If you roll instead of sliding the situation changes again. If your head snags on something - perhaps you have very sticky hair, for example - different again.

I can't think of many circumstances where you'd hit a horizontal surface at a speed even close to your pre-impact horizontal speed. Maybe getting your front wheel stuck in a grating while holding the bars in a death grip, or something like that.

 

[User482]

Net benefit? If so, what is the problem?

Offering a benefit to a particular individual at a particular time isn't the same as a benefit for everyone all of the time.

 

[Linford]

Linfords bumped his head.

Good to see you join us...We are (mostly) managing to debate the issue without getting personal. What do you think about this lid apparent ability to absorb a huge amount of energy ?

Every cyclist magically develops cat like reflexes and they always land on their feet ?

 

[ufkacbln]

I've already stated that anything up to walking pace, and I consider the risk to be no greater...anything more than that, and the risk goes up as the momentum rises Momentum = Mass x Speed

If I were to move my motorbike at anything more than walking pace, I would consider it entirely sensible to wear the lid. I am not the one arguing against the value of head protection for speeds above walking pace.

Brilliant,

NOw all you need to do is clarify... greater than what

No greater than racing ferrets?
No greater thhan dangling your toes in an pirahna infested swimming pool?

 

[User482]

That's a definition of an artificial leg, but not necessarily a cycling helmet. Innit.

I'm not necessarily talking about helmets.

 

[User482]

What, specifically, are you thinking of?

I think I'm capable of deciding for myself what safety equipment I should use. I think that elbow and knee pads, and a helmet are a good idea for downhill mountain biking. I don't think they should be compulsory all of the time. I don't think me choosing to wear them promotes compulsion.