Impact Speed

[david k]

I'm not missing the point: you claimed that a helmet that had scratched in a situation where the head wouldn't have was effective!

No, I supported somebody else s findings that the head wasn't scratched in either case.

 

[david k]

Well, it didn't break so it must have been. It stands to reason.

No Adrian, if the head wouldnt have scratched anyway, it makes no difference if a helmet was worn or not (assuming this to be the case), the head wasnt damaged in either case.

 

[Twilkes]

If there's going to be a fight, could everybody please put their helmets on now.

 

[Dan B]

No Adrian, if the head wouldnt have scratched anyway, it makes no difference if a helmet was worn or not (assuming this to be the case), the head wasnt damaged in either case.

This is not the same as you said upthread

So in short, a helmet may scratch which will protect the head from scratching and in other cases the helmet may scratch when the head wouldn't have scratched. In both cases the head didnt scratch so it confirms the helmet has done its job (as far as stopping scratches)

If it makes no difference whether the helmet was worn, it can hardly be described as having done its job.

Or maybe ... maybe it can. Perhaps the helmet which sits on top of my bookcase at home for most of my cycle journeys is actually still protecting me from scratches and cuts even when I'm not wearing it. I wonder how far we can take this line of thinking: perhaps if I'd left it in the shop it might even work its magic from there - after all, it doesn't know whether I've paid for it

 

[david k]

I guess a wildly optimistic person could imagine this to represent progress.

Progress? its always been the case so there no change from me

Progress would be you being able to see anything remotely identifying a helmet as slightly useful and you not having to make numerous posts to try to rebuff the claim

 

[david k]

This is not the same as you said upthread

If it makes no difference whether the helmet was worn, it can hardly be described as having done its job.

Or maybe ... maybe it can. Perhaps the helmet which sits on top of my bookcase at home for most of my cycle journeys is actually still protecting me from scratches and cuts even when I'm not wearing it. I wonder how far we can take this line of thinking: perhaps if I'd left it in the shop it might even work its magic from there - after all, it doesn't know whether I've paid for it

take it where you want mate its largely insignificant, and as we said upthread the survey proved nothing and all comments are based on assumtions

 

[david k]

So this
Means nothing then?
I appreciate that what I have now done is provide David K with another opportunity to do his best barrister impression "Ah ha, so you do agree that helmets are useful then" and then I have to go through the qualifications all over again.

What it does do is you cannot be open minded and only want to jump on any post that may suggest a helmet in any positive light however small.
So as you brought it up again ill ask the same questions again, the ones you didn't answer last 2 times:

How do you know from google images what people presumed?
How do you know what the accident speed actually was and therefore how do you know the helmet did not do what it was designed to do?
As you suggest they are only designed to work in a certain way up to a certain speed, as you dont know how can you make these statements?

Once again I'm pointing out that the survey proves nothing, what your doing is making up a back story to be argumentative

 

[Licramite]

w

I've been sitting here watching your hotpotch of units , with your assumptions and roundings and your fixation on force. Helmets are tested in Joules, a BS helmet is "good if it doesn't shatter under 100J . I'll be interested in watching the mental gymnastics from here.

which BS are you refering to ?
yes sorry about jumping about with units of measure but G force isn't measured in joules, nor is bone strength if you can convert them I would love to see the formula as it would be so much easier.
100J isn't awful lot , go on splat calculator and say drop a 5kg body (a head weighs about 10lb), you won't have to drop it very far to acheive 100j. - 2m jusy gave 98j.
G force increases its weight , thats increased with speed, 25mph ups a heads weight under G to 250lbs so thats 113.6Kg dropped 100mm = 111.3joules - are you sure the BS said that?

 

[Little yellow Brompton]

w


which BS are you refering to ?
yes sorry about jumping about with units of measure but G force isn't measured in joules, nor is bone strength if you can convert them I would love to see the formula as it would be so much easier.
100J isn't awful lot , go on splat calculator and say drop a 5kg body (a head weighs about 10lb), you won't have to drop it very far to acheive 100j. - 2m jusy gave 98j.
G force increases its weight , thats increased with speed, 25mph ups a heads weight under G to 250lbs so thats 113.6Kg dropped 100mm = 111.3joules - are you sure the BS said that?

BS/EN 1078

I don't need to translate them , this is your project.


"100J isn't awful lo, go on splat calculator and say drop a 5kg body (a head weighs about 10lb), you won't have to drop it very far to acheive 100j. - 2m jusy gave 98t"

By Jove I think he's got it!

You are right 100J is not a lot, it's the equivalent of standing astride your bike and falling sideways, once you start cycliing you are already outside the parameters that the helmet was designed to withstand.Maybe you start to realise now why so many people are not impressed with " My helmet sdaved my life.."?

I was being generous with the 100J, a helmet could only manage 85J and still pass.

still think it's worthwhile doing the maths for a 25MPH impact?

 

[Twilkes]

If Jesus had been wearing a helmet, perhaps he would still be with us today.

 

[david k]

I have not presumed anything about anyone who posted any of those images or about any of the people who wore the helmets.
.

Can I refresh your memory

srw said: ↑

How silly of me. That's what the internet exists for.
https://www.google.co.uk/search?q=damaged bicycle helmets&hl=en&tbo=u&rls=com.microsoft:en-gbE-SearchBox&tbm=isch&source=univ&sa=X&ei=IIsCUcXUOcSa1AWcpIGYCA&ved=0CD0QsAQ&biw=991&bih=683

I've done a simple frequency count. Of the 21 pictures of damaged helmets on the first two results pages on 25th Jan at about 1:40pm GMT:

• 5 appear to be of surface damage only;
• 3 appear to be damaged by crushing (typically minor);
• 13 appear to be complete write-offs.

So only 3/21 (14%) appear to have been damaged in the way in which they are designed to offer protection, and 4 times as many are completely destroyed.​

david k said: ↑

are you saying those helmets that were completely destroyed offered no protection?​

Adrian said: ↑

No, no one is saying that. What people are saying is that they did not provide the protection, either that they were supposed to, or what people assume they did when they look at them afterwards.​

david k said: ↑

so your saying they did offer protection?​

Adrian said: ↑

Yes but not necessarily any useful protection. It could be a minor cut saved. The person's head might well have been fine without the helmet. We just don't know.​

 

[david k]

How many times do I need to tell you that no input that I have had on this thread is by reference to those images?

you clearly did as above, i asked srw a question regarding images and you answered

 

[david k]

So my telling you exactly what my position here is counts for nothing. At which point I have to ask, why are you asking then?

I wasn't asking, I was reminding you this is what we are discussing.
Everything I asked or discussed was in relation to srws original post and I pointed this out continually, and as such all responses are in relation to this.

 

[benb]

No, I supported somebody else s findings that the head wasn't scratched in either case.

So when you said "In both cases the head didnt scratch so it confirms the helmet has done its job" you weren't claiming the helmet was effective?

 

[david k]

So when you said "In both cases the head didnt scratch so it confirms the helmet has done its job" you weren't claiming the helmet was effective?

depends how you read it, in both cases the head wasnt hurt. in cases where the head would have scratched the helmet would have protected the user from scratches. In cases where the head wouldnt have scratched it made no difference