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Yes I have racing seats and yes my belts are tethered into the rear support frame(the Del Sol has a near roll cage support column coming up behind the seats, the bottoms are bolted into the chassis reinforced frame points(it has a raised ridge of thickened steel for the seat belts.))
Auto tensioning seat belts are not the safety feature. Belt elasticity is. I've worked with ropes and tubular webbing(what our seat belt is made of) for a long time. When climbing you have a special length of rope(if its likely you will experience a hard fall) that is between the climber and the belay rope. Its much more elastic than the dynamic rope. The idea is it stretches to accomodate the fall over a greater distance.
Pre/auto-tensioning just makes sure that the belt doesn't act like static rope(lets you fall until your reach rope length and then moves not one millimeter further). If you didn't have pre/auto-tensioners your seat belt would be whatever length you adjusted it to when you got in and sat down. If its already tight against your body its utterly irrelevant. What you want then is a "zorber" thats a pully rigged to a very strong spring. You can't make it give by hand. On a press you can extend it but you had better be clear when it lets go. . .
At the moment the wreck starts is not the moment of impact. When your body first presses against the seat belt is when the strain will be greatest because its not stretching the belt and the shock absorber hasvn't been breached yet because it takes a fraction of a second for those mechanisms to engage. When that event happens the air bags are not deployed. They have a chemical compound (NaN3?) that produces NaN and N2 when shaken or shocked. IT happens incredibly fast but the passengers are already expanding the seat belts and have experienced the harshest of the acceleration on their chest.
Yes I am very familiar with HANS, but I'm not ever travelling fast enough for it to matter. It takes an incredible amount of force to create an "earnhardt" event. He was doing almost 200 mph(3x faster than my speed) and was wearing a 4 lb helmet(mass thats still going to want to accelerate). The most acceleration I can do is a few feet per second in reverse from 60 mph. The most I can achieve is less than 1/3 the acceleration and only 60% the amount of mass.
I've already said I am not opposed to frontal airbags. They are useful at decelerating head and neck, its just the other ones that don't make alot of sense.
I have a friend still in the hospital from a car wreck. She had frontal airbags and no side air bags. She was t-boned at 65 by a truck while she was in a Honda Civic 97. She broke both of her legs(at the Femur) and almost bled to death internally from the damage to her legs. No injuries to her head whatsoever. No injuries to any other part of her body whatsoever. Her passenger(who had no airbags) had no injuries other than a broken clavicle and her splean ruptured, both results from the seat belt not any other impact. I'm not saying the seat belts were bad, they saved their lives, but at the extremes of the spectrum(truck-car, T-boned, nearly highest speed possible fora collision) the other safety features would have been absolutely useless and probably caused more damage.
Thats why I haven't been on I had to drive to visit her yesterday. You can say I am uninformed and not involved but I've seen both of the cars and I've seen the injuries and I stick with my story. Frontals are fine, curtains, pillars and rear useless. They both agree they are glad they didn't get smashed by another (the first) set of air bags from the sides.
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