What means helmet rating?
12-12-06, 03:42 PM
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What means helmet rating?
In all the helmet discussions we hear about helmets being rated up to a certain speed, but I'm not sure what that really means. It seems reasonable to me that (1) the helmet might still be better than nothing even above that speed, and (2) the helmet is no guarantee even below that speed. If those assumptions are correct (are they?), then it seems that the speed rating is not just some magical point ensuring protection below and failure above, but rather a point on some kind of probability spectrum. I can envision some kind of curve showing level of protection (or perhaps probability of level of protection) plotted against speed, so is the rating simply the point on the speed axis where the protection falls below a certain threshold or the curve takes on a certain slope?
12-12-06, 05:01 PM
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I'll save supcom & others the trouble. "Yet another helmet troll thread for this week." Or "yet another helmet troll starting another thread about this dead horse of a subject."
Sorry JB, but if I don't you know others will.
Sorry JB, but if I don't you know others will.
12-12-06, 06:09 PM
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I don't think 'speed' is a consideration. This might help: https://www.helmets.org/stdchart.htm, while this is the more detailed comparison: https://www.helmets.org/stdcomp.htm
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"Let us hope our weapons are never needed --but do not forget what the common people knew when they demanded the Bill of Rights: An armed citizenry is the first defense, the best defense, and the final defense against tyranny. If guns are outlawed, only the government will have guns. Only the police, the secret police, the military, the hired servants of our rulers. Only the government -- and a few outlaws. I intend to be among the outlaws" - Edward Abbey
12-12-06, 06:55 PM
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Where have you ever seen a speed rating published for a bicycle helmet?
12-13-06, 04:13 PM
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Very tough to say.
Some helmets have a warning that say they are not for motor vehicle use, but what does that necessarily have to do with speed? Bicycles can outrun underpowered mopeds under some conditions.
It would also depend on the surface on which you impacted.
On a nice smooth concrete surface your helmet would slide and bounce after impact, where on a very rough asphalt surface, the helmet may catch and twist at impact.
There's much more to it than speed. You'll have to add an axis to your probability plot to consider surface roughness!
Some helmets have a warning that say they are not for motor vehicle use, but what does that necessarily have to do with speed? Bicycles can outrun underpowered mopeds under some conditions.
It would also depend on the surface on which you impacted.
On a nice smooth concrete surface your helmet would slide and bounce after impact, where on a very rough asphalt surface, the helmet may catch and twist at impact.
There's much more to it than speed. You'll have to add an axis to your probability plot to consider surface roughness!
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12-13-06, 04:21 PM
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Originally Posted by JohnBrooking
In all the helmet discussions we hear about helmets being rated up to a certain speed, but I'm not sure what that really means. It seems reasonable to me that (1) the helmet might still be better than nothing even above that speed, and (2) the helmet is no guarantee even below that speed. If those assumptions are correct (are they?), then it seems that the speed rating is not just some magical point ensuring protection below and failure above, but rather a point on some kind of probability spectrum. I can envision some kind of curve showing level of protection (or perhaps probability of level of protection) plotted against speed, so is the rating simply the point on the speed axis where the protection falls below a certain threshold or the curve takes on a certain slope?
If you look at the stickers in your helmet you can google the name of the testing agency and find helmet testing by that organization. It has nothing to do with speed, unless it has been changed. Snell is one of the organizations but that does not mean your helmet is snell approved. Last time I looked the helmet testing criteria was available. It was more like a certain weight dropped from a certain height.
12-13-06, 05:08 PM
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Thanks for the links. I know I've heard claims about helmets being primarily intended for falls at under 14 MPG or some such numbers, maybe I mistook those comments to actually be part of an official spec. In any case, I haven't read the specs yet, but now I can, so thanks.
Meanwhile, I propose a new term: meta-troll. Definition: One who accuses another of trolling, especially on scant evidence save the meta-troll's possible past impression of the accused.
^ 3
Meanwhile, I propose a new term: meta-troll. Definition: One who accuses another of trolling, especially on scant evidence save the meta-troll's possible past impression of the accused.
^ 3
12-13-06, 05:15 PM
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As the above links explain, helmets are tested with low speed, low height drops, and if they survive those low speed, low height drops, they meet the CPSC requirement. These tests recreate the forces found in low speed falls from a bicycle.
Obviously, the tests do not recreate the forces found in high speed crashes.
Obviously, the tests do not recreate the forces found in high speed crashes.
Last edited by Blue Order; 12-13-06 at 05:31 PM.
12-13-06, 05:26 PM
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Originally Posted by JohnBrooking
Thanks for the links. I know I've heard claims about helmets being primarily intended for falls at under 14 MPG or some such numbers, maybe I mistook those comments to actually be part of an official spec. In any case, I haven't read the specs yet, but now I can, so thanks.
Meanwhile, I propose a new term: meta-troll. Definition: One who accuses another of trolling, especially on scant evidence save the meta-troll's possible past impression of the accused. ^ 3
Meanwhile, I propose a new term: meta-troll. Definition: One who accuses another of trolling, especially on scant evidence save the meta-troll's possible past impression of the accused.
^ 3I have heard the exact same thing mentioned somewhere about 14 mph. It was after I read about helmet testing so I did not think about it much.
meta-troll : added to data base.
12-13-06, 07:11 PM
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Originally Posted by 2manybikes
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"Let us hope our weapons are never needed --but do not forget what the common people knew when they demanded the Bill of Rights: An armed citizenry is the first defense, the best defense, and the final defense against tyranny. If guns are outlawed, only the government will have guns. Only the police, the secret police, the military, the hired servants of our rulers. Only the government -- and a few outlaws. I intend to be among the outlaws" - Edward Abbey
"Let us hope our weapons are never needed --but do not forget what the common people knew when they demanded the Bill of Rights: An armed citizenry is the first defense, the best defense, and the final defense against tyranny. If guns are outlawed, only the government will have guns. Only the police, the secret police, the military, the hired servants of our rulers. Only the government -- and a few outlaws. I intend to be among the outlaws" - Edward Abbey
12-13-06, 08:35 PM
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Originally Posted by chipcom
Oh, so my links weren't good enough....why do you hate freedom, bra?
It's tired and I'm getting late?
