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According to our sources, the threshold established for preventing serious injury to the head and neck begins at and above 4,000 Newtons (N). One pound of force is equal to 4.4 N. This would be about 5 g's on the entire body of a person who weighs 180 pounds. The SFI testing level is 70 g's. For a force exerted on the base of the skull and neck, that's equal to the weight of the head (including the helmet, and so on) multiplied by 70. The head and neck can't physically contain such a force if unprotected. The damage is similar to what happens when someone gets hanged. It's not a pretty sight.
The ultimate force necessary to cause injury in each person is necessarily dependent on varying factors that make choosing a threshold difficult. The following are factors that enter into the complex circumstances of crash survival: 1) the driver's age (the younger the better), 2) the driver's weight, especially the head, 3) how physically fit the driver is, 4) the driver's gender (you pick which is better), and 5) past injuries that may contribute to the degree of injury in later events. So, choosing a threshold such as 4,000 N doesn't necessarily indicate a perfectly safe condition--it just indicates that you're much better off if a device can lower the force on the head and neck to some force below that level.
"Without" Results Without an H&N device, the forces on the head and neck can exceed 35 g's in a 60mph crash. The SFI test level force of 70 g's is probably much higher than we will ever experience but it's possible. The various devices being tested must lower the force felt at the base of the skull to well below the 4,000 N level (909 pounds of force).
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Getting down to brass tacks, what does that mean? It's all dependent on the amount of head weight plus helmet weight. We found this interesting quote on the SFI website: "An adult human cadaver head cut off around vertebra C3, with no hair, weighs somewhere between 4.5 and 5 kg, constituting around 8 percent of the whole body mass." In our 180-pound example, the head would weigh about 15 pounds. A helmet weighs about 31?2 pounds. So, if we divide 909 pounds of force (4,000 N) by 18.5, that equals about 50 g's.
This may indicate that a 180-pound person will not survive a crash that exceeds 50 g's, according to the 4,000 N limit. In reality, the actual force of a sudden impact may far exceed 4,000 N because of the whipping effect of the head being thrown forward on impact. So, a 35g crash, measured in the car, may instantaneously exert more force than that on the head and neck, hence the 70g test level.
A heavier head/helmet combination would necessitate the need to experience even less g-force in a crash in order to survive. We can see where g-force and Newton numbers are subjective. The bottom line is that we need to reduce the loads on our head and neck in order to survive a crash. Head-and-neck restraint systems do just that. Racing without one is like walking on a tightrope with a noose around your neck. If you fall off, well, you get the point.
Product Showcase In a typical race car, the driver's body is restrained by the seatbelts and seat. This leaves the head free to move unrestrained in the event of an impact. This unrestrained movement can lead to injury and, in many cases, death. Head-and-neck restraints have been developed to combat this.
Recent racing history tells us there is a real and present danger to the driver associated with sudden deceleration when crashing into concrete walls or other objects at high speeds. In addition to the rash of top-level professional drivers' deaths, of which we are all aware, there have been fatalities on the short tracks caused by the very same conditions that these products are designed to address.