toddulu Posted January 22, 2009 Share Posted January 22, 2009 This has been on the local forum, and I hadn't seen it here so I thought I'd pass it along. :biggrin: Click Here Link to comment Share on other sites More sharing options...
Member Contributer KevCarver Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 Couple years ago I had the same helmet size epiphany and found the correct size Shoei X-11. What a world of difference, and I love the fit! Something I have seen on another Arai presentation that wasn't mentioned specifically here is that you should not set your helmet on top of the gas tank. He mentions that gas can break down the inner liner, but doesn't go any further in this video. The gas cap can vent fumes out and up into your helmet sitting on top. Link to comment Share on other sites More sharing options...
Member Contributer sa1713 Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 When I had my helmet inspected by Arai USA, they confirmed the inner lining is the best way to determine helmet safety. They also stated that personal hair products can accelerate the lining's deterioration similar to gas fumes...... :laugh: Link to comment Share on other sites More sharing options...
Guest Posted January 22, 2009 Share Posted January 22, 2009 Helpful video. Now I just need to drop 500 bucks on an Arai :laugh: Link to comment Share on other sites More sharing options...
Baileyrock Posted January 22, 2009 Share Posted January 22, 2009 Helmets are a one use item, meaning that it's only good for one impact with your head in it. :laugh: It is the compression of the liner (which is the impact absorbing part of the helmet) that makes it a one shot deal. Dropping your helmet on the ground without your head in it to compress the liner does No harm it as long as the outer shells integrity isn't damaged. IMO. Link to comment Share on other sites More sharing options...
Member Contributer cruzinaz Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 Good video, thanx. Link to comment Share on other sites More sharing options...
Member Contributer FotoMoto Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 The physics are the same but no one suggests football players (US football) put a new helmet on after each contact. Things that make you go "hmmm?". :laugh: Link to comment Share on other sites More sharing options...
Baileyrock Posted January 22, 2009 Share Posted January 22, 2009 The physics are the same but no one suggests football players (US football) put a new helmet on after each contact. Things that make you go "hmmm?". :blush: True, but they have a real hard time getting to 60 or 100 mph on the field. Also I think they use more of a memory foam which allows for repeatable impacts than the traditional non-memory foam used in m/c helmets (don't they) :laugh: Link to comment Share on other sites More sharing options...
Member Contributer VF1000R Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 Also I think they use more of a memory foam which allows for repeatable impacts than the traditional non-memory foam used in m/c helmets (don't they) :laugh: Yes, having worn both extensively, I can tell you that they are designed very differently. Many football helmets even have inflatable sections of padding. Dirk Link to comment Share on other sites More sharing options...
Member Contributer CrazyInNYC Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 Hey, thanks. :laugh: There's always been a lot of debate over that topic. :dry: :dry: Now I feel bad for scolding my wife when she dropped her helmet out of her hand. Well, she did scratch up the finish, so no I don't. :blush: Link to comment Share on other sites More sharing options...
mechdziner714 Posted January 22, 2009 Share Posted January 22, 2009 Ever poured gas in a styrofoam cup? Link to comment Share on other sites More sharing options...
Member Contributer sa1713 Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 Ever poured gas in a styrofoam cup? McGuyver Napalm? Link to comment Share on other sites More sharing options...
Beck Posted January 22, 2009 Share Posted January 22, 2009 Dropping your helmet from around 3 feet off the ground shouldn't damage its shell's structural integrity. All helmets have some sort of woven mat matrix (Fiberglass, Carbon fiber, Kevlar) moulded into it's shell that makes it very hard to crack or rip apart with impacts speeds it might encounter at non-driving situations. Unless it hits some sort of sharp point or sharp corner when it hits the ground, the damage should be mostly cosmetic. If there is more than cosmetic damage after such a drop, you most likely have a defective shell on your helmet. A check by a qualified helmet technician should still be done otherwise after ANY sort of significant impact just to make sure. (means shipping to the manufacurer's "local" HQ for inspection). JMOs Beck 97 VFR Link to comment Share on other sites More sharing options...
Member Contributer FotoMoto Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 The physics are the same but no one suggests football players (US football) put a new helmet on after each contact. Things that make you go "hmmm?". :blush: True, but they have a real hard time getting to 60 or 100 mph on the field. Also I think they use more of a memory foam which allows for repeatable impacts than the traditional non-memory foam used in m/c helmets (don't they) :laugh: Yes, of course not but a pro athlete is capable of around 20 mph so theoretically you could have a 40mph full speed collision between two players. IIRC, the Hurt report gave the avg. speed of a fatal m/c wreck at 38ish. But this is not my point. My point is I think we can safely assume m/c helmets are built to a higher standard than football helmets but it's assumed that m/c lids can't stand up to smaller impact(s) than what football players are typically subjected to without being completely "used up". Real world examples: rider low sides and the helmet kisses the ground getting some scratches. Just about everyone, including me, would tell him to get a new lid; better to be safe than sorry we'd say but a coach would tell a player to get back out there and "knock some heads!" Although some look pretty cool now-a-days with the smoked faceshields and cool paint jobs, I'm certainly not suggesting we should be wearing football helmets. I'm just pointing out what I think are some discrepancies. Link to comment Share on other sites More sharing options...
Member Contributer Knife Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 When I had my helmet inspected by Arai USA, they confirmed the inner lining is the best way to determine helmet safety. They also stated that personal hair products can accelerate the lining's deterioration similar to gas fumes...... :laugh: Well then, I should be safe from that peril. My hair is rapidly leaving me, so I don't waste any time on it, and I certainly don't waste any money on "product". Link to comment Share on other sites More sharing options...
Guest Posted January 22, 2009 Share Posted January 22, 2009 The physics are the same but no one suggests football players (US football) put a new helmet on after each contact. Things that make you go "hmmm?". :blush: True, but they have a real hard time getting to 60 or 100 mph on the field. Also I think they use more of a memory foam which allows for repeatable impacts than the traditional non-memory foam used in m/c helmets (don't they) :laugh: Yes, of course not but a pro athlete is capable of around 20 mph so theoretically you could have a 40mph full speed collision between two players. IIRC, the Hurt report gave the avg. speed of a fatal m/c wreck at 38ish. But this is not my point. Not to be a physics nerd or anything, but 2 objects of the same mass hitting each other at 20mph is still a 20 mph impact. It would be the same as running 20 mph into a brick wall.....not that I would want to do that ether! Link to comment Share on other sites More sharing options...
Member Contributer VF1000R Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 Not to be a physics nerd or anything, but 2 objects of the same mass hitting each other at 20mph is still a 20 mph impact. It would be the same as running 20 mph into a brick wall.....not that I would want to do that ether! :laugh: Yeah, this is a widespread misunderstanding and I had quite a discussion with a state trooper about it once. The force is determined by your acceleration so if you go from 20 mph to 0 mph, you get the same force no matter how it is applied. F=ma Dirk Link to comment Share on other sites More sharing options...
Guest Posted January 22, 2009 Share Posted January 22, 2009 Not to be a physics nerd or anything, but 2 objects of the same mass hitting each other at 20mph is still a 20 mph impact. It would be the same as running 20 mph into a brick wall.....not that I would want to do that ether! :blush: Yeah, this is a widespread misunderstanding and I had quite a discussion with a state trooper about it once. The force is determined by your acceleration so if you go from 20 mph to 0 mph, you get the same force no matter how it is applied. F=ma Dirk That would be an awesome conversation to listen in on...........Astrophysicist vs. State Trooper in discussing Newton's Laws of Physics! This wasn't directly after you tried to talk yourself out of a speeding ticket because he wasn't taking into account Einstein's Theory on General Relativity, was it :laugh: ? Link to comment Share on other sites More sharing options...
Member Contributer Macs06VFR Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 2 objects (people) running into each other at 20 mph is a 40 mph crash (if head-on). 1 person running at 20 mph into a stationary object is a 20 mph crash. Either way, I get a headache. :blush: I'll keep wearing my Arai. :laugh: Link to comment Share on other sites More sharing options...
Member Contributer FotoMoto Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 :laugh: Yeah, this is a widespread misunderstanding and I had quite a discussion with a state trooper about it once. The force is determined by your acceleration so if you go from 20 mph to 0 mph, you get the same force no matter how it is applied. F=maDirk LOL, you know that's probably where my I got it from. You always hear LEO's talking in terms of "closing speed" in violent head on wrecks. Link to comment Share on other sites More sharing options...
Member Contributer VF1000R Posted January 22, 2009 Member Contributer Share Posted January 22, 2009 That would be an awesome conversation to listen in on...........Astrophysicist vs. State Trooper in discussing Newton's Laws of Physics! This wasn't directly after you tried to talk yourself out of a speeding ticket because he wasn't taking into account Einstein's Theory on General Relativity, was it :blush: ? :laugh: No, it was at a driver safety class I took years ago in Florida after I got a speeding ticket on the 500. He made that comment during the class so I talked to him about it during a break. He insisted he was right even after I posed various thought experiments to explain it. :dry: I just let it go. Dirk Link to comment Share on other sites More sharing options...
Guest Posted January 22, 2009 Share Posted January 22, 2009 2 objects (people) running into each other at 20 mph is a 40 mph crash (if head-on). 1 person running at 20 mph into a stationary object is a 20 mph crash. Either way, I get a headache. :dry: I'll keep wearing my Arai. :laugh: Sorry Macs...........Newton disagrees with you. But still a good idea to wear the Arai whether you understand physics or not! :blush: Link to comment Share on other sites More sharing options...
Member Contributer Macs06VFR Posted January 23, 2009 Member Contributer Share Posted January 23, 2009 Not to be a physics nerd or anything, but 2 objects of the same mass hitting each other at 20mph is still a 20 mph impact. It would be the same as running 20 mph into a brick wall.....not that I would want to do that ether! :biggrin: Yeah, this is a widespread misunderstanding and I had quite a discussion with a state trooper about it once. The force is determined by your acceleration so if you go from 20 mph to 0 mph, you get the same force no matter how it is applied. F=ma Dirk Guys, I respectfully beg to differ. Newton would agree with me that his second law (F=ma) is not yet applicable here as we do not know acceleration. 20 mph = velocity; how long it took to go from 20 to 0 = acceleration. The physics of these two impacts is complex. (e.g. the acceleration of the front is significantly higher than the rear) But... the physics of these two impacts are definitely not equal. Mac Link to comment Share on other sites More sharing options...
Guest Posted January 23, 2009 Share Posted January 23, 2009 Not to be a physics nerd or anything, but 2 objects of the same mass hitting each other at 20mph is still a 20 mph impact. It would be the same as running 20 mph into a brick wall.....not that I would want to do that ether! :biggrin: Yeah, this is a widespread misunderstanding and I had quite a discussion with a state trooper about it once. The force is determined by your acceleration so if you go from 20 mph to 0 mph, you get the same force no matter how it is applied. F=ma Dirk Guys, I respectfully beg to differ. Newton would agree with me that his second law (F=ma) is not yet applicable here as we do not know acceleration. 20 mph = velocity; how long it took to go from 20 to 0 = acceleration. The physics of these two impacts is complex. (e.g. the acceleration of the front is significantly higher than the rear) But... the physics of these two impacts are definitely not equal. Mac Newton's third law actually explains it a little better. But you are correct in one regards, that it is complex generally because of the introductions of vectors during the impact and the variations in real world situations (ie. you will never have two exactly identical objects). But that doesn't justify the misnomer that a head on collision is twice as much force as a impact with a solid object. In pure theory, they are the same. Link to comment Share on other sites More sharing options...
Member Contributer VF1000R Posted January 23, 2009 Member Contributer Share Posted January 23, 2009 I respectfully beg to differ. Newton would agree with me that his second law (F=ma) is not yet applicable here as we do not know acceleration. 20 mph = velocity; how long it took to go from 20 to 0 = acceleration. The physics of these two impacts is complex. (e.g. the acceleration of the front is significantly higher than the rear) But... the physics of these two impacts are definitely not equal. Mac Ok, as head-on bike/car impacts are pretty close to being inelastic (kinetic energy goes to zero) the acceleration takes place over a very short interval and both bodies end up at the point of impact. Yes, the gory details are complicated but overall a bike going 20 mph hitting another bike going 20 mph head on will incur basically the same damage as hitting a wall at that speed. It will most certainly be much, much worse if it hits the wall at 40 mph. Dirk Link to comment Share on other sites More sharing options...
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