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#11
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helmets and rotational acceleration
Just zis Guy, you know? wrote:
On Mon, 11 Aug 2008 15:01:34 +0100, Phil Armstrong said in : Having scanned the two papers (which are related: the physical testing generates paramenter values for the finite element analysis) the main conclusion appears to be that the coefficient of friction between the headform (with anatomically correct scalp + hair) and the helmet is too low to lead to rotational forces in a 'typical impact' which are large enough to cause brain damage. I think this is a bit of policy-based evidence making. Dr Mills is a non-medical doctor with no relevant qualifications who has given important (to one side) testimony in over 100 cases of contributory negligence. So far as he is concerned, it appears that helmets are always effective as the only factor of importance is the 1.5m a cyclist falls vertically when he's hit. That he might be propelled forwards at the same time by a 50 mph car is totally irrelevant. Yes, the "typical impact" in the paper appears to be about the same as the one used to test that a given helmet reaches the relevant British Standard. Phil -- http://www.kantaka.co.uk/ .oOo. public key: http://www.kantaka.co.uk/gpg.txt |
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#12
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helmets and rotational acceleration
Just zis Guy, you know? wrote:
On Mon, 11 Aug 2008 15:01:34 +0100, Phil Armstrong said in : Having scanned the two papers (which are related: the physical testing generates paramenter values for the finite element analysis) the main conclusion appears to be that the coefficient of friction between the headform (with anatomically correct scalp + hair) and the helmet is too low to lead to rotational forces in a 'typical impact' which are large enough to cause brain damage. I think this is a bit of policy-based evidence making. Dr Mills is a non-medical doctor with no relevant qualifications who has given important (to one side) testimony in over 100 cases of contributory negligence. So far as he is concerned, it appears that helmets are always effective as the only factor of importance is the 1.5m a cyclist falls vertically when he's hit. That he might be propelled forwards at the same time by a 50 mph car is totally irrelevant. Brian Walker and John Franklin, plus a few solicitors, are currently largely warding off such nonsense but it could be more difficult if he's now coming up with 'proof' that helmets guard against oblique impacts. Note that the 'proof' in this case is largely dependent on the assumption that he is right. Guy Please see http://www.cyclecraft.co.uk/digest/liverpool.html for an example of Dr Mills other contributions. Assuming it is the same 'Dr Mills' then this would seem to point to a more balanced perspective. Graham |
#13
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helmets and rotational acceleration
On Mon, 11 Aug 2008, Martin wrote:
To me the second one seems to say, that linear impacts forces were not affected by the helmet rotating. They also investigated rotational forces, but do not have the results in the abstract. The first one says that extra rotational forces were negligible when the rider hits the ground at 4m/s (about 9mph). So, for a collision where you probably won't have life-changing injury when bare-headed, and for which you probably won't have life-changing injury in a pure normal impact, you're almost as likely not to have life-changing injury if it's an oblique impact? Maybe that's unfair, I'd still like to read the papers. regards, Ian Smith -- |\ /| no .sig |o o| |/ \| |
#14
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helmets and rotational acceleration
Ian Smith wrote:
On Mon, 11 Aug, Tom Crispin wrote: On 11 Aug 2008 12:41:47 GMT, Ian Smith wrote: Two papers available online from today, which appear to address one of the significant uncertainties regarding helmet performance. Can someone confirm my interpretation of this: ======== From these tests, any additional danger of rotational head injury from wearing a helmet is slight or negligible. ======== I would say you shouldn't conclude anything from the abstracts of two technical papers. Which is why I'd be keen to hear the views of anyone that does have access to the content. If it was someone I trust to be able to read straight, it might even influence my opinion. regards, Ian SMith I will ask whether any of my former colleagues have access to the full papers -- Nigel |
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helmets and rotational acceleration
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#16
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helmets and rotational acceleration
Ian Smith wrote:
Maybe that's unfair, I'd still like to read the papers. I did send you copies of the text, assuming your stated email was valid... if it isn't, mine is, let me know where to send. Pete. -- Peter Clinch Medical Physics IT Officer Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital Fax 44 1382 640177 Dundee DD1 9SY Scotland UK net http://www.dundee.ac.uk/~pjclinch/ |
#17
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helmets and rotational acceleration
Peter Clinch wrote:
Ian Smith wrote: On Mon, 11 Aug, Tom Crispin wrote: On 11 Aug 2008 12:41:47 GMT, Ian Smith wrote: Can someone confirm my interpretation of this: ======== From these tests, any additional danger of rotational head injury from wearing a helmet is slight or negligible. ======== I would say you shouldn't conclude anything from the abstracts of two technical papers. Which is why I'd be keen to hear the views of anyone that does have access to the content. If it was someone I trust to be able to read straight, it might even influence my opinion. I would concur with Ian's analysis. But, for the sake of argument, let's assume your take is a fair one. The possibility of rotational injury aggravation by helmets has primarily been a conjectured mechanism for how they might make things worse. Even if you demonstrate that as a non-issue, it will not affect in any way, shape or form the whole population studies that demonstrate no clear advantage in terms of serious injuries to wearing a cycle helmet. Pete. helmets don't seem to attaully do much, niether harm or protect. though in my experance getting sweaty is something they do rather well. roger -- www.rogermerriman.com |
#18
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helmets and rotational acceleration
My reading of this is that the authors deliberately used tests below
the minimum required by EN whatever. They showed that even at these low levels the rotational acceleration is sufficient to get to 50% of that required for causing brain injury. They claim that because the tests do not exceed the limits (due to being essentially at almost stationary fall off speeds where DAI is unlikely to occur anyway) that the criticisms of Curnow etc are invalid. There is a lack of relating this work to the real world in terms of crash speeds and likely outcomes. ...d |
#19
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helmets and rotational acceleration
On Mon, 11 Aug 2008 21:16:52 +0100, Slark
said in : Please see http://www.cyclecraft.co.uk/digest/liverpool.html for an example of Dr Mills other contributions. Assuming it is the same 'Dr Mills' then this would seem to point to a more balanced perspective. Not sure, but he does appear to amend his evidence according to which side employs him. Guy -- May contain traces of irony. Contents liable to settle after posting. http://www.chapmancentral.co.uk 85% of helmet statistics are made up, 69% of them at CHS, Puget Sound |
#20
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helmets and rotational acceleration
On 11 Aug 2008 20:53:46 GMT
Ian Smith wrote: So, for a collision where you probably won't have life-changing injury when bare-headed, and for which you probably won't have life-changing injury in a pure normal impact, you're almost as likely not to have life-changing injury if it's an oblique impact? That's my interpretation too - move along, nothing to see here ... |
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