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Originally Posted by DerAlte Thanks for the ESP related information.
But, if the inertia lock is holding the person in place (not moving any further forward), what help would the tensioner provide in bringing the person back? If the driver's mouth hit the steering wheel rim, the teeth are already broken - pulling him back won't save any more? (Sorry for the gory details!). OTOH, in that state pulling the torso back will injure the neck (reverse whiplash), no? |
The mechanical lock works when the seat-belt is pulled by a jerk like it happens in an event of a crash. If the car crashes, the jerk will cause the mechanical lock to lock the seat-belt and hold you in whatever position you already are. If you put on the seat-belt and bend forwards slowly, then the seat-belt will allow you to go and touch your forehead on the dashboard or the steering wheel. It wont lock.
So just before the crash, if you are bent forward i.e. away from the seat-back and closer to the steering wheel, the mechanical lock will only lock your torso in the position it already is; close to the steering wheel. You may also get hit by the air-bag deployment or your head may hit the wheel. But the pre-tensioner will pull you towards the seat-back, away from the steering and hold you there firmly. Same with the tensioner. The tensioner is deployed fractionally before the air-bag so that your torso is taken away from the airbag deployment range and you stay planted in your seat.
Ofcourse your head will be whipped forward due to it, but it is going to happen anyways in the crash.
Rally cars are equipped with cables coming out of head restrains and attach to the helmet of the driver. In case of a crash these cables tighten up and prevent the head of the driver from getting tossed voilently.
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Originally Posted by DerAlte And "What If" means the video is made up? |
Yes. It is an ad made up to promote their website. I didn't get their connection with air-bag though.
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Originally Posted by DerAlte Err... what kind of ad hoc logic is that?
* Both the airbag and the driver are in the same car traveling at whatever speed
* When the airbag deploys, the speed at which the head travels towards it is independent of the car's speed
So the airbag shouldn't be deployed? Funny!
Didn't understand. Did you mean similar to the filling air in a (plastic / paper) bag and bursting it, scaring someone?
So the airbag shouldn't deploy if you brake to a stop only to be hit by an oncoming vehicle? Common scenario in India - I asked this earlier. |
Here you missed my point by a mile atleast.
Let me put it this way. Consider that a car travelling at 100kmph hits a dog about 50meters before a curve.
The air-bag is deployed and the driver is startled/blinded due to it.
He doesn't notice the curve and drives straight towards the median.
The air-bag will already be losing the air inside it. (It does not hold the air inside it. It deflates within a few seconds)
And when the car will Actually hit the median (when the air-bag would actually be needed) it wont be available because it has already been deployed and the air is now gone.
The driver will be severely injured due to hitting his head.
So the air-bag should be deployed only during a severe crash. A car nannot travel any further (In max cases) after a severe crash. So there will be no chance of losing control due to air-bag deployment.
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Originally Posted by saaicon Thanks for the quite illuminating discussion on dependence of airbag opening on impact intensity . But I had a different question :
1. Why was there smoke inside the cabin ? is it connected to hot air inside the bag?
Also I read somewhere that after an impact the fuel supply to engine is automatically cut off . Did it not happen in this case ? |
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Originally Posted by bsksam There was a white powdery smoke in the cabin, and the steering wheel was warm to the touch. |
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Originally Posted by vikram_d A small explosive charge is used to rapidly inflate airbags and this miniature explosion causes the smoke. |
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Originally Posted by bblost Its not just the explosion.
But the layers of powder that are kept between the layers of the airbag that give out an illusion of smoke.
The powder is to help prevent burns. |
Vikram, you are partially right. Its sodium azide that is ignited in air-bags and the heat is due to its ignition. But it causes much less smoke than what appears in the cabin. As Bblost pointed out it is the powder which causes the illusion of smoke. It is similar to talc cum powder. It does not prevent burns.
Its purpose is to prevent the folded air-bag from sticking together and deploying freely when required. You may have noticed a powder between tyres and tubes or inside the tubes at the puncture shop. Same function
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Originally Posted by saaicon Thanks Vikram. How about the question on the fuel to the engine being cut off ? Is it not a mandatory safety requirement? |
I dont think it is mandatory. Some manufacturers have the feature, some dont.