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Helmets cramp my style

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Helmets cramp my style

Old 04-13-07, 12:41 AM
  #1276  
John C. Ratliff
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Tour de France crash with arrows

Closetbiker,

'Sorry it has taken me so long to post these. I've been pretty busy over the last few weeks. Anyway, the arrows point to the helmet striking the rail, then bouncing off. Do you really feel that the results would be the same if he had not been wearing a helmet?

John
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Old 04-13-07, 12:53 AM
  #1277  
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not wearing a helmet..well..it's a no-brainer, litterally !
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Old 04-13-07, 08:22 AM
  #1278  
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Funny how no one has waded in on this .

Canada (what a great name) spun his bike around and placed it between him and the guard rail. His bike hit it, he didn't.

The picture is too fuzzy to see anything in any detail, but I've gone over the video lots, and only come away with an admiration at these riders skills, and cool. Imagine, in a situation like that, going tat fast and having the presense of mind and body control to do that.
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Old 04-13-07, 09:29 AM
  #1279  
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Closetbiker,

Look closely, and you'll see his bike above him, not in front of him. His head is against the guard rail.

It would be interesting to get David Canada's reading of this, since he had a unique perspective. I understand that he received a broken collar bone, and I'm interested in which side was broken. If it was his right collar bone, it occurred in the initial fall. However, if it was his left collar bone, it occurred when he impacted the guard rail. I found this from a website on the Tour, so it was his right collarbone that was broken:

Crash Claims Two Victims!
At 141km, Canada and Verbrugghe lost control of their bikes on a right-hand turn. Kessler crashed into Canada and all three went flying over roadside barriers. Kessler remounted and was caught by the peloton at the 144km mark. The other two were taken to hospital: Canada fractured is right collarbone and Verbrugghe needed x-rays for a suspected fracture of a bone in his leg (the doctors didn’t specify where the break was).
see: https://www.letour.fr/2006/TDF/LIVE/us/1400/index.html

I don't think you do much pushing with a broken collarbone to control a bicycle in a crash.


John

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Old 04-13-07, 10:18 AM
  #1280  
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and I don't think breaking a collarbone equates to hitting your head. Didn't I originally post that was what happened in the first place?

The bike is above him, because it impacted the rail , putting a barrier between the rail and himself (there is no depth perspective or clarity in the pic), and rebounded back. The helmet sure looked intact after the bounce.

Maybe finding a different angle would help? Also, finding the speed at which the riders lost control in the curve would help too. If I remember right, the cornering speed was somewhere around 70 kph (but I could be wrong). Hitting a guard rail at that speed, with a helmet would be a bit beyond it's capacities, wouldn't you think?

Oh yeah, maybe you're not the best person to ask that question. That's OK John, we all have our prejudices. I'm just trying to be objective, maybe that's the problem. To be objective towards someone with a prejudice.
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Old 04-13-07, 12:37 PM
  #1281  
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Originally Posted by closetbiker
and I don't think breaking a collarbone equates to hitting your head. Didn't I originally post that was what happened in the first place?

The bike is above him, because it impacted the rail , putting a barrier between the rail and himself (there is no depth perspective or clarity in the pic), and rebounded back. The helmet sure looked intact after the bounce.

Maybe finding a different angle would help? Also, finding the speed at which the riders lost control in the curve would help too. If I remember right, the cornering speed was somewhere around 70 kph (but I could be wrong). Hitting a guard rail at that speed, with a helmet would be a bit beyond it's capacities, wouldn't you think?

Oh yeah, maybe you're not the best person to ask that question. That's OK John, we all have our prejudices. I'm just trying to be objective, maybe that's the problem. To be objective towards someone with a prejudice.
You know, I could simply reverse the statement you made above, and say "Oh yeah, maybe your not the best person to ask that question. That's OK, Closetbiker, we all have our prejudices. I'm just trying to be objective, maybe that's the problem. To be objective towards someone with a prejudice..." It does look to me that you're a bit blind to what the photos show. We have not seen David Canada's helmet, so we cannot say until we get better info. I don't think there is another angle on this, as this was the only camera on the crash that I know about.

You think that 70 kph is beyond the capacity of the helmet to handle, so it won't make any difference at all? That's an interesting statement. I'm wondering what the head without a helmet would look like? And let's say that, for argument purposes, David Canada did not hit his head on the rail (even though the photos pretty clearly show that happening). Would you like to be that close, at those velocities, to hitting your head without a helmet?

John
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Old 04-13-07, 01:00 PM
  #1282  
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I agree that we all have our prejudices, and that's why I've asked (as you have) for a different opinion.

I asked 3 co-workers (non-cyclists) to look at the clip and the pictures and they all said, the heads never hit anything (for what thats worth)

I think your looking for things that aren't there. (but that's just my opinion)

I think at those velocities, it doesn't matter if your wearing a helmet. At those velocities, it wouldn't do any good.

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Old 04-13-07, 03:36 PM
  #1283  
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Originally Posted by closetbiker
I think at those velocities, it doesn't matter if your wearing a helmet. At those velocities, it wouldn't do any good.
And I simply disagree.

John
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Old 04-13-07, 05:29 PM
  #1284  
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And that's ok with me, if its ok with you, but according to

https://www.helmets.org/limits.htm
If you have the misfortune to impact head first against a bridge abutment at the bottom of a screaming 55 mph downhill, your helmet will not prevent a head injury.
and,
The typical bike crash involves a drop to the pavement... The typical bicycle crash impact occurs at a force level equating to about 1 meter (3 feet) of drop, or a falling speed of 10 MPH...So bike helmets are tested with a 2 meter (6.56 feet) drop. Motorcycle helmets are tested at 3 meters, about 17 mph. A really good bicycle helmet can handle that.

Last edited by closetbiker; 04-13-07 at 06:11 PM.
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Old 04-13-07, 06:10 PM
  #1285  
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Well, let's see, you quoted 70 kpm above, not 55 mph. 70 kph is 43.5 mph, more than 10 mph less than you quote above. And David Canada did not hit a bridge abutment, but a guard rail. He did not hit it head-on, but at about a 30-45 degree angle. So there was not a sudden, complete stop, but a rebound in the opposite direction at an angle from the original angle equal, to the incoming angle. If you take a ball, and throw it as hard as you can straight down against a concrete floor, it will rebound straight up. But if you throw it at a 30-45 degree angle, it use that energy to go out, not up. On top of that, he had been on the ground, and slowing, for some 30 feet before hitting the guard rail. So he would have slowed considerably by the time he hit the rail.

If his head did hit the ground, it was a glancing blow, at an even greater angle. The forces are independent, and so the force downward is the same as if he had dropped from that height at no forward velocity. I did some of these kinds of calculations in high school physics in the 1960s, and the laws of physics have not changed.

I know you know this, but you use this bridge abutment analogy, and your analogy really does not fit this situation. This is actually stated in the article you cite above. Here is what it states, in whole:

Under US standards bike helmets are tested in 2 meter drops that achieve about 14 miles per hour (22.5 kph) on the flat anvil. In Europe the drop height is only 1.5 meters. Why so low, when bicyclists frequently exceed 14 mph in forward speed?

The typical bike crash involves a drop to the pavement. The important energy in that crash is supplied by gravity, not by forward speed. Although forward speed can contribute some additional energy, the main force is the attraction of gravity, and the impact severity is determined by the height of your head above the pavement when the fall begins. It is gravity that determines how fast your helmet closes with the pavement. Some of the crash energy is often "scrubbed off" by hitting first with other body parts. The typical bicycle crash impact occurs at a force level equating to about 1 meter (3 feet) of drop, or a falling speed of 10 MPH. The rider's forward speed before the crash may be considerably higher than that, but the speed of the head closing with the ground, plus a component of the forward speed, less any energy "scrubbed off" in other ways, normally average out at about 10 MPH.

So bike helmets are tested with a 2 meter (6.56 feet) drop. Motorcycle helmets are tested at 3 meters, about 17 mph. A really good bicycle helmet can handle that.

As a famous study showed years ago, helmets prevent about 85 percent of head injuries and 88 percent of brain injuries. Those are good odds. But that means that helmets did not prevent all brain injury for 12 percent of the study population. And they are designed to prevent catastrophic brain injury, not the milder forms of concussion. If they are softened to prevent mild concussions they will compress too fast and bottom out in the more severe impacts. Today's helmets may or may not be perfect in striking the balance, but we know they work well. Still, every bike helmet sold in the US has a sticker inside warning you that "no helmet can protect the wearer from all foreseeable impacts." That sticker is required by law.

If you have the misfortune to impact head first against a bridge abutment at the bottom of a screaming 55 mph downhill, your helmet will not prevent a head injury. That is not very important, since the rest of your body will be mush anyway. Fortunately that very seldom happens. Most of the cases where the helmet's limits are exceeded involve crashes with cars. Every rider understands that it is very important to avoid being hit by a car.

Obviously a helmet covers only your head, leaving the rest of your body unprotected.

In sum, your helmet will do a good job of protecting you in a fall, but the limits can be exceeded. It should be clear that nothing about wearing a helmet affects the need to ride safely, or the need for safe riding facilities. (emphasis added--jcr), from: https://www.helmets.org/limits.htm
I really wish you would post quotes in context.

John
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Old 04-13-07, 06:12 PM
  #1286  
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Well, I edited it if you can't get the gist. 10 mph vs 43 is still quite a leap. (and didn't I ask what the speed was? - I'll bet it was more than 10 mph) (and independant sources said, no head was hit) (and isn't an abutment something that supports a structure? like a support pillar on a guard rail?)

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Old 04-13-07, 07:58 PM
  #1287  
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Closetbiker,

I don't think you understand the physics of this at all. 43 mph is the initial speed (rolling speed of the bicyclist coming into the turn), prior to impact. It has little to do with the speed at which the head impacts either the ground or that guard rail, as that speed "scrubs off" (see the above post), from several factors. The initial fall was absorbed already, so acceleration due to gravity was pretty well dissipated. What we have left is a glancing blow caused by the resultant forward speed against the guard rail, if indeed his head did hit the guard rail (which you dispute). But in that case, the speed of David Canada's head impacting the guard rail was probably in the neighborhood of 10 mph, which is where the helmet is designed to function.

Now if we look at the initial fall, and whethe his head hit the ground, because these are independent forces, it is only the acceleration of gravity from approximately 1-1.5 meters that would be a factor (see the paper's description that you quoted).

The only exception to that is if he hit an immovable object, dead on (good reason for that choice of words), and the helmet had to absorb the full impact of the forward motion plus the inertia of the bicyclist's body and bike, at a 90 degree angle to the motion. That dead stop, like the paper says, would be lethal. That is where the bridge abutment (a usually square column holding up a bridge) comes in. It's like the road runner cartoons (maybe too old for you to remember) where the coyote trying to catch the roadrunner hits an object dead on, stops completely, and slides down the object. This would also apply to a car hood hit dead on, but worse. Those situations are outside the design criteria of a helmet.

John
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Old 04-13-07, 09:06 PM
  #1288  
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I think we're forgetting that it isn't always about how much the helmet can absorb in any kind of sudden motion...but how much the brain can absorb when it impacts the inside of the skull. That's a brain injury that can't be avoided and the most common kind.
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Old 04-13-07, 11:15 PM
  #1289  
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Traumatic brain injury is helped by a helmet though. Basically, the brain is inside the skull, but surrounded by fluid (cerebral-spinal fluid). The fluid protects, and dampens, the movements of the brain. But very sudden jarring can force the brain to either impact the side of the skull, or move so quickly that it actually tears. Both can be deadly. The helmet helps by dampening the impact. When the foam crushes, it decelerates the brain much more slowly than if the impact had been against the skull itself. The skull keeps moving as the foam is compressed, instead of instantly stopping and reversing direction. This dampens the effect of the force applied to the head, and helps keep the brain from tearing or hitting hard against the inside of the skull.

If there is no helmet, then there is no dampening effect, and the skull translates the forces to the brain, as there is not much dampening effect caused by a thin layer of skin and the underlying bone. The cerebral-spinal fluid would still act to dampen the force, but because there is not too much distance between the brain and the skull, there is not very much protection in a bicycle crash from this fluid covering the brain.

John
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Old 04-14-07, 08:37 AM
  #1290  
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Originally Posted by John C. Ratliff
Closetbiker,

I don't think you understand the physics of this at all...the speed of David Canada's head impacting the guard rail was probably in the neighborhood of 10 mph...The only exception to that is if he hit an immovable object...

------------

Traumatic brain injury is helped by a helmet ...When the foam crushes, it decelerates the brain much more slowly than if the impact had been against the skull itself.

John
You're off kilter John. I know you believe that's what happened, but 3 other people I asked said it didn't, but even if it did, I wonder at your grasp of physics if you believe that Canada's head contacted the guard rail at around 10 mph and that the guard rail wasn't an immovable object.

I understand how it is that a helmet works, but I'm thinking you're not understanding the level of force at which that crushing is finished it's job. There is a limit to it's ability to be crushed.

The brain does not simply move in one piece in the head on impact. When the impact occurs the brain moves in different directions, and at different velocities, in a very complex series of motions where there seems to be no discernable pattern. Medical theory is moving toward better definitions of concussion vs.
catastrophic brain injury. It is still working on it and bike helmets are an attempt to improve chances of injury in some, limited circumstances, and even then, results have been spotty at best.

What's going on in the skull is far beyond what we put on outside the skull. An impact to the skull is not even necessary to have a brain injury.
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Old 04-14-07, 01:42 PM
  #1291  
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Closetbiker,

Read carefully! I did not say that the guardrail was an immobile object; I said that David Canada's head, if it hit the guard rail, struck it a glancing blow. His head did not stop cold, but continued moving. This is a very different statement.

In a different paragraph, I stated that "if he hit an immoveable object, dead on...," meaning at a 90 degree angle, it would be a different situation. You have a propensity of editing to make the meaning of a post different from what was actually said.

More later.

John

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Old 04-14-07, 04:40 PM
  #1292  
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Vector analysis of Tour de France Bike Crash

Closetbiker,

The part of physics I'm speaking about is called "vector analysis." You can get a good look at it here:

https://www.dac.neu.edu/physics/a.cro...2/Vectors.html

Basically, any force vector can be broken into its components to form a right triangle. The individual components are given by the Pythagorean theorm, as shown on the site above. What we are looking for is the component which is at right angles to the helmet/guard rail interface. This is the component the helmet and/or head has to contend with.

Before looking at the calculation, I'm going to make some assumptions. Looking at the photos, I am assuming that what started out as about a 45 mph turn, lost about half it's initial velocity through friction with the road. David Canada appears to have hit the road, and skidded about 33 feet (10 meters) before hitting the guard rail. I am going to assume that he hit with a velocity of about 25 mph, after loosing that much (through the "scrubbing off" of velocity mentioned in the site you cited by the fall, the friction of the roadway, and the rolling that we see in the photos). So in the calculation, the initial velocity into the guardrail on about a 30 degree angle to the rail (again from the photos) is 25 mph.

From the Professor Cromer site above, you can see the R vector is the one we are using, which would be 25 mph. The "A" angle would be 30 degrees, and the component we are looking for is the "y" vector (or "j" component on that diagram). To get that, we use the following formula:

sinA = y/R
or,
y = SinA*R
y = sin(30 degrees) * 25 mph
y = 0.5 * 25 mph = 12.5 mph

Now, the 30 degrees was an estimate, based on the photos. If it was 25 degrees that David Canada's head hit the guardrail at, then the calculation would be:

y = sin(25 degrees) * 25 mph
y = 0.42 * 25 mph = 10.6 mph

These both are within the range of the helmet to help mitigate the impact, according to the source you cite above. My citing of a 10 mph impact on the helmet was a guestiment, but appears to be good.

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Old 04-14-07, 07:30 PM
  #1293  
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Tha's nice John, but you're no pathologist or neurologist, and your qualifications do not exceed those of Dr. George Shively, (The Snell Memorial Foundation founder) or of Brian Walker, (one of the leading experts on the mechanics of helmets) or W.J. Curnow. All of these people publicly pronounce findings directly in opposition to your postings.

Speculate all you wish, but when cyclists with helmets receive brain injuries at an equal rate as cyclists without helmets, a reasonable person has to consider the limitations of helmets.

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Old 04-14-07, 07:39 PM
  #1294  
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Originally Posted by closetbiker
Tha's nice John, but you're no pathologist or neurologist, and your qualifications do not exceed those of Dr. George Shively, (The Snell Memorial Foundation founder) or of Brian Walker, (one of the leading experts on the mechanics of helmets) or W.J. Curnow. All of these people publicly pronounce findings directly in opposition to your postings.

Speculate all you wish, but when cyclists with helmets receive brain injuries at an equal rate as cyclists without helmets, a reasonable person has to consider the limitations of helmets.
Well, let's see. The heading on the Snell Momorial Foundation website states, "Think Ahead, Wear A Helmet. Make Sure It's Snell Certified." Here's the website:

https://www.smf.org/

This website states:

Why wear a helmet?
Auto racing, motorcycling, bicycling, skiing and any activity that incorporates speed, agility and a head all impose risks of head injury leading to death or permanent disability. Helmets are the single most effective means of preventing these injuries.
So what you quoted above, that bicycle helmets will protect at about a 10 mph crash, you are now repudiating? Here again is the website you quoted:

https://www.helmets.org/limits.htm

And you don't deny that the crash shown above was within these limits? Now you rely upon mini-quotes from people like Dr. George Shively, which I cannot find anywhere. But you will not stand behind the organization that he founded, the Snell Memorial Foundation, and what they say about helmets? We've discussed Mr. Walker before (those willing can dig these posts out of this thread somewhere way back when...). For those wanting to read W.J. Curnow's complete paper, you can find it here:

https://scholar.google.com/scholar?q=...=1&oi=scholarr

You can make up your own minds. That study did say that hard shell helmets "protect the brain from injury consequent upon damage to the skull..." This is why I did make the switch to a hard shell helmet for my cold-weather helmet.

John

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Old 04-14-07, 08:11 PM
  #1295  
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and we both know Dr. Shively is on record with the statement,
it is impossible to build a helmet that will offer significant impact protection.
(and any reasonable person would suspect the same)
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Old 04-15-07, 12:23 AM
  #1296  
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Originally Posted by closetbiker
and we both know Dr. Shively is on record with the statement,


(and any reasonable person would suspect the same)
Actually, I don't know that. I would like to see the full quote, not just half a sentence. Knowing how you butchered my post in a quote above, I suspect that the same has happened here. So show us the full paragraph, and hopefully a link, or a source, and I'll be more convinced.

You may want to go back and re-read my post just above this one. The Bike Forums server went down before I was able to put everything together for it.

By the way, concerning this Tour de France crash in the photos above, none of these cyclists received any brain injury.

John
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Old 04-15-07, 08:00 AM
  #1297  
closetbiker
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Yeah, I'm the one butchering posts. I think I'm the one being reasonable and understanding the posts. I think you think I'm butchering them because you're not understanding the points made with them and you don't understand you can use 10 words instead of 1000 to get a point across. (and by the way, none of those cyclists received any brain injuries because none of those cyclists hit their heads - at least that's my opinion and 3 other independant observers - I emailed SAUNIER DUVAL to ask David directly if he hit his head or not. If he or the team - doesn't reply, I'll email QUICK STEP, the team he was on when he crashed).

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Old 04-15-07, 09:39 AM
  #1298  
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Well Closetbiker, I have been pretty patient with you, posting first the photos, then photos with arrows, then a mathematical explanation of the force vectors involved. For anyone wondering why I posted about Closetbiker butchering a post, see posts 1287, 1290 and 1291. Because you do this, I am asking for the full quote from Dr. George Shively, of which you have posted a fragmented portion of a sentence. Since you are not producing it, I have to assume that you did the same with him that you did with me above. So, where is that full quote?

Concerning writing SAUNIER DUVAL, I did that last Thursday or Friday.

Concerning hitting heads on the ground in this crash, and your saying it did not happen, I'm still curious how you explain Kessler's helmet, with rocks imbedded in the air vents. Have you tried doing this by simply rolling a helmet in the gravel?

You are so certain that helmets do nothing for a cyclist, especially in the situations which are discussed above, that you will not look at any evidence which shows otherwise. You brush it aside and try to turn the discussion elsewhere to derail the discussion.

John
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Old 04-15-07, 02:50 PM
  #1299  
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I doubt if too many people are following this exchange John. I'd be suprised if it's more than just a couple of others looking at it and moving on.

I think I've been easily, equally patient with you and your insistance you're right. We both have our view points, and at least I've asked a couple of other people to view both the video and the photos, so that's something, at least.

It's not the first time you refer to something that I've supposedly posted that isn't at all what I posted, or that you've missed a point and I'd be willing to bet, it's going to happen again, so I guess I'll just have to live with it.

Funny how some people can live with something, but others just have too hard of a time to accept different points of view.

As to the full quote, I'll dig it up, but does it really matter too much? It's a pretty direct statement pertaining to a reasonable point about helmets that many others have re-iterated over and again - on the other hand, even if I do dig it up, would you be willing to accept it? You haven't accepted other quotes from qualified specialists saying the same thing, so why would you accept the original statement? Your posts indicate you wouldn't be reasonable about it. Even I admit there is some good helmets can do, it's just the limitations of them we argue about. I believe they have limitations, you seem to think, even in high speed collisions, significant impact protection is possible.

Last edited by closetbiker; 04-15-07 at 03:21 PM.
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Old 04-15-07, 07:03 PM
  #1300  
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You did, Closetbiker, tick me off a bit with your misrepresentation of what I said with what you wrote in post #1290. That leads me to disbelieve much of what you quote, as when you do things like that to one person, you would do it to others.

Concerning my belief in helmets, I have qualified that with what was in the link you posted, that "If you have the misfortune to impact head first against a bridge abutment at the bottom of a screaming 55 mph downhill, your helmet will not prevent a head injury..." But I also showed, which was also in the same link you posted, that helmets can help even in supposedly "high speed" crashes by absorbing the force component that impinges directly upon the head. I gave you the mph for 30 and 25 degrees, respectively, and at those angles, the component acting upon the head is 12.5 and 10.6 mph. We could take that calculation the other way, and here is the result:

y = sin(45 degrees) * 25 mph
y = 0.707 * 25 mph = 17.6 mph

So at a 45 degree angle, the component would be 17.6 mph, which is beyond the helmet's design limits. So what would it be at 90 degrees?

y = sin(90 degrees) * 25 mph
y = 1.00 * 25 mph = 25 mph

This is way beyond what the helmet could do, even though Willey Coyote survived hitting these rocks dead on, we would not. By splitting out the components and looking at them, I was able to show why the helmet can work in some supposedly "high speed" crashes, where the helmeted head hits at an angle. The same could be said of car/bike accidents, where the blow is a glancing one. The helmet will help in these situations, but again, if it is a 90 degree "hit" it probably is not survivable. Is this such a difficult concept for you to see and understand?

At this point, I think we both need a rest from this discussion. I've got some pressing committments in the next few weeks, and so, while I'll be monitoring this discussion, I probably won't be posting much more for a while.

John

Last edited by John C. Ratliff; 04-15-07 at 10:56 PM.
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