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Old 29th May 2013, 15:19   #61
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by lucifer1881 View Post
Driver would lose steering control because his/her hands would automatically be jerked off the steering on deployment.

And, no airbag deployment at any speed is not always less harmful than its absence. If an airbag deploys at, say, 60 kmph on hitting a dog and the car is on a curve then it will go off the road. If this happens while driving in the mountains, then the car can even go off the cliff.
I don't think driver side airbags are big enough to push your hands away from the steering wheel.

I guess supertinu can answer this point better. But from his post I assume that he still had his hands on the steering wheel even after the airbags deployed because he has mentioned that the car stopped in a straight line. But this is just an assumption.

So supertinu would you mind telling us if your hands were jerked away from the steering wheel?
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Old 29th May 2013, 16:02   #62
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by MotoNanu View Post
... Only after the minimum threshold, the airbag deployment is expected. ...
So if you are at standstill and a car rams your car from the front, the airbags in your car shouldn't deploy?

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Originally Posted by MotoNanu View Post
... I quoted pedestrian airbag as they are required to deploy at lower speeds and their threshold is different than the one for the driver/ passenger airbags.
Err... which airbag is the 'pedestrian airbag' in the context of this discussion?

I have heard of bumper-mounted airbags to minimize injury to a pedestrian on a hit, but that is still an esoteric subject. Not in regular production yet.

Quote:
Originally Posted by lucifer1881 View Post
... his/her hands would automatically be jerked off the steering on deployment. ...
Doesn't happen that way usually. It really doesn't matter if it did, since visibility will be completely obscured, and the driver will be disoriented for a short while - hardly a situation where the driver is still in control.

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Originally Posted by lucifer1881 View Post
... And, no airbag deployment at any speed is not always less harmful than its absence. ...
Think again. And again. The hot air in the airbag will at most singe your skin. Without the airbag, you might need to visit a dentist for 1 year!

As far as losing control is concerned, statistical probability still applies on unending use-case possibilities - paranoia makes the issue irrational! If every use-case had equal probability, there would be a 50% chance that one would be safe leaving the car at home and taking public transport.

I am not sure I can compute the chances of someone coming across a dog crossing the road at exactly the same time that they are on a curve or hairpin bend AND there is an impact AND the airbag fires! Can you?
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Old 29th May 2013, 16:10   #63
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by DerAlte View Post
So if you are at standstill and a car rams your car from the front, the airbags in your car shouldn't deploy?

Err... which airbag is the 'pedestrian airbag' in the context of this discussion?

I have heard of bumper-mounted airbags to minimize injury to a pedestrian on a hit, but that is still an esoteric subject. Not in regular production yet.
Well the scenario is still the same when your ignition is OFF and someone rams the car. The airbag would not deploy as Ignition has to be ON!

You correctly interpreted the pedestrian airbag, though not in this context, I only wanted to give the hint of the speed threshold
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Old 29th May 2013, 16:49   #64
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by DerAlte View Post
...I am not sure I can compute the chances of someone coming across a dog crossing the road at exactly the same time that they are on a curve or hairpin bend AND there is an impact AND the airbag fires! Can you?
This is a very real possibility, something that I have experienced in the Bolero. In my case, it was not a dog but a tractor carrying a wide load that rammed into the front right of the bumper when I was doing 80 kmph. The impact reduced the speed to about 50 kmph in almost no time at all. The damage was quite severe - from the right headlight to the right front fender everything had to be replaced. Since the Bolero does not have airbags, I could keep the car in a straight line. Else it could have veered off and hit an on-coming bus.

It is not about paranoia. I am just discussing a possibility, which in my case was a reality. I fully understand the importance of airbags. However, an airbag deploying when a car is doing substantial speeds is surely not safe.
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Old 29th May 2013, 16:58   #65
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Default Re: Airbags deployed after hitting a dog. Understanding why?

A bunch of retards crashing into a traffic jam.



You can see how fast the airbags inflate and deflate. Accident happens at 53 seconds. By 58 seconds the camera is back to normal and you can see the airbags have been deflated.

Last edited by bblost : 29th May 2013 at 17:02.
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Old 29th May 2013, 17:30   #66
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by DerAlte View Post
So if you are at standstill and a car rams your car from the front, the airbags in your car shouldn't deploy? ...
Quote:
Originally Posted by MotoNanu View Post
Well the scenario is still the same when your ignition is OFF and someone rams the car. The airbag would not deploy as Ignition has to be ON! ...
Are you sure the scenarios are same?

In my example I am assuming you have been forced to stop because some unthinking person is coming full tilt at you in your lane (usual Indian scenario). You wouldn't be sitting there with ignition off in that scenario, now would you?
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Old 29th May 2013, 18:04   #67
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by DerAlte View Post
In that state of mind (understandable; you cannot say you were cool as a cucumber throughout the episode, can you?), you might have pulled it quite hard. Happens to anyone in a hurry - that is the nature of the friction-based lock. The correct action is to unlatch.

Boss, the Airbag system of such smartness will cost as much as the car. Or, the car will cost upwards of 60L OTR in India (Volvo, for example)!!! If you can understand why passenger switch is not provided in low-cost cars, you
should understand the impact of cost v/s price of car.
Ofcourse I wasnt in my coolest state of mind but then I didnt keep on lugging at the seatbelt. Once the pretensioners deloyed the belts got really tight. After I unbuckled the seat belt they did not retract any further. Its just stayed out halfway and wouldnt go in neither extend out any further. I even pushed my seat back to reduce the length required but still it wasnt enough. On the driver side the seat belt was not even used and completely retracted inside during the impact. And that also had gone into same state and completely tightened up

I understand your point about feature vs cost of the car. I am just making an observation that safety feature like air bags should have been smarter or are not as smart as I assumed them to be. Whether I can afford the better ones or not that is a different story

Quote:
Originally Posted by lucifer1881 View Post
Driver would lose steering control because his/her hands would automatically be jerked off the steering on deployment.
Quote:
Originally Posted by vikram_d View Post
I don't think driver side airbags are big enough to push your hands away from the steering wheel.

I guess supertinu can answer this point better. But from his post I assume that he still had his hands on the steering wheel even after the airbags deployed because he has mentioned that the car stopped in a straight line. But this is just an assumption.

So supertinu would you mind telling us if your hands were jerked away from the steering wheel?
I pointed this out earlier in the thread, but as far as I remember I think my hands did come off the steering wheel. Primarily cause the seat belts pulled me back with a jerk and the air bags hit my chest. But I cannot be certain since it was a 1-2 second event in which car came to stand still almost in the same lane.
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Old 29th May 2013, 23:03   #68
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Default Re: Airbags deployed after hitting a dog. Understanding why?

Personally I think the idea that at higher speeds you might be better off without airbags, so you can 'steer' the car is probably just very unrealistic.

As I said earlier, this particular case is odd in the sense that it appears that the airbags were set of due to a relative small impact. To me it still sounds like a technical glitch.

Normally when the airbags are set off, it means you are experiencing a very high rate of deceleration. Without an airbag, and even with (pre) tensioners you would smash you face into the steering wheel and dash board real badly. The notion that under those circumstance you would be able to steer and control your car are completely unrealistic. There will always be exceptions as with everything in life.

But by and large, if the airbag deploys you would have been hurt very badly without them and you would not be in a fit state to steer your car around a bend or to avoid driving of a cliff.

You really should not underestimate the forces on your body even in relatively low speed accidents. My sister T-boned another car, doing about 25 km/h, in a parking lot. She was wearing her seatbelt, but her car at the time had no airbags and she ended up in intensive care. She hit her head onto the steering wheel and front window really badly.

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Old 29th May 2013, 23:53   #69
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by Jeroen View Post
I don't want to get caught in semantics, but are you saying there is a difference between tensioners and pre-tensioners? Either the belt is working normally, ie it locks/doesn't unwind or it gets (pre) tensioned.

Actually, I think the term pre-tensioning is a bit misleading in the first place; There is actual tensioning happening when this system kicks in. But it is before your body starts actually moving forward. Maybe that's why the call it pre?
Jeroen
There is a difference between tensioner and pre-tensioner.
I am coming to that point.

Quote:
Originally Posted by DerAlte View Post
Err... what is the connection between Seat Belt and Electronic Stability Program? Is the seat belt expected to hold you in the seat if you swerve the car??? -ive g produced due selective braking by ESP is way below the trigger threshold.

The time between seat belt (pre)tensioning and airbag firing can be detected only in an appropriately equipped test facility - the driver cannot figure it out

Right on all counts, @Jeroen. 'Pre' is used by some to denote active belt tensioning by the 'tensioner' before the seat belt latch/lock engages.
Yes, there is a connection between the ESP and seat-belts, in high end cars. Please read in detail about Mercedes-Benz Pre-Safe system. It is standard on all Mercs of today.
I will put it here in short.
Suppose a driver swerves at high speed in order to avoid something:
1. The car will lose stability and the ESP will be activated and it will try to stabilise the car.
2. The pre-safe feature will sense instability and a potential accidental situation based on data received from ESP.
3. So it starts preparing the car for a crash before it actually happens.
4. The seat-belt "pre"-tensioner is actuated (It is reusable and does not need replacement)
5. If the seats are reclined, they are straightened.
6. If the rear head restrains are folded, they pop out.
7. All the open windows are rolled up. (But not completely. About 2 inches of gap is left as the occupants tend to hold the edge of the window in panic. Closing the window completely would crush their fingers) Same happens with an oppen sunroof.

All this happens together.
I have been through this experience several times in a row and I definately felt the pre-tensioners pull me back on every single occasion.

The car may travel some distance in this mode and then crash which will deploy the air-bags. So there would be a lot of time between "pre"-tensioner and air-bag.

However, There is no time gap in tensioners (I have not used pre here) and air bags. The purpose of tensioner is that if the occupant has already bent forward before the crash, the conventional mechanical lock will only prevent him from going any further due to th crash, whereas the tensioner will pull the occupant back towards the seat.


Quote:
Originally Posted by lucifer1881 View Post
On a related note, what would have happened if a car at 80kmph does not brake and hits a dog or a deer or some other animal? I am assuming due to impact the speed would decrease to say 50-60 kmph or even 20-30 kmph, and the car would keep moving. Would an airbag deploy in such a case? And would it not be extremely dangerous for an airbag to deploy when the car has not come to a complete stop? Do manufacturers build in any logic to not deploy an airbag if the car is moving above a threshold speed?
You have hit the exact point. All air-bags are designed keeping this in mind and air-bags are never deployed like that. This is a case of faulty deployment.

Quote:
Originally Posted by MotoNanu View Post
Every manufacturer would have set a minimum threshold for the vehicle speed. For example: 30 kmph. Only if the vehicle speed is above this and the system detects a crash, the airbags would deploy. If the speed is less than the threshold, airbags won't deploy.
No, there is no minimum threshold speed for deployment.
Consider a scenario where your car is air-borne before it crashes. Your foot will naturally be on the brakes. So the car is sensing the speed is 0kmph since the wheels aren't rotating. But you will need the air-bags when the car lands, right?

Quote:
Originally Posted by DerAlte View Post
The video that @vikram_d posted shows that, doesn't it? It wasn't a simulation or Photoshop modification - the car was stationary when the airbag deployed.
Yes, the video is made up. In the end, it says "WHAT IF?"
Air-bags dont deploy because of a hand bag hitting the grill.

Quote:
Originally Posted by DerAlte View Post
Err ... why would the driver lose steering control? Forget to steer in panic is different! Also, the harm due to airbag deployment is - at any speed - much less than the harm it's absence would have caused, right?
Wrong. Air-bag deploying at high speed would be absolutely useless. The car is still at high speed means there is not much impact that may injure the occupants.
Also the air bag inflates and deflates in a matter of seconds. See what Bblost is pointing at in the post quoted below. There would be no air in the bag when required if the driver is alarmed and blinded by the pop of the bag and hits the median in the process.

Quote:
Originally Posted by bblost View Post
A bunch of retards crashing into a traffic jam.

You can see how fast the airbags inflate and deflate. Accident happens at 53 seconds. By 58 seconds the camera is back to normal and you can see the airbags have been deflated.
Please understand that air-bags never deploy by such a small impact. Please see the video that I have posted two paages back. The airbags deployed after the bumper, bonnet, fender were all damaged and the front wheel almost locked due to the damage. A massive impact is needed for deplyment of the air-bag. And in case of such an impact the car wont be travelling at a high speed when the air-bags deploy.

I hope I was able to explain my point correctly.
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Old 30th May 2013, 00:06   #70
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Consider a scenario where your car is air-borne before it crashes. Your foot will naturally be on the brakes. So the car is sensing the speed is 0kmph since the wheels aren't rotating. But you will need the air-bags when the car lands, right?
^ I don't think air-bags are deployed based on speedometer or tire speed.

An interesting read: http://www.midsouthrescue.org/id7.html
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Old 30th May 2013, 00:41   #71
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by Tejas Ingle View Post
I have been through this experience several times in a row and I definately felt the pre-tensioners pull me back on every single occasion.

Remind me never ever to ask you for a lift!
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Old 30th May 2013, 00:50   #72
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Remind me never ever to ask you for a lift!
Jeroen

It was during demo's of ESP, ABS, Pre-Safe performed in controlled environment by professional rally drivers.
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Old 30th May 2013, 01:21   #73
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by Tejas Ingle View Post
Yes Jeroen, you are right about tensioners. They are activated along with the seat-belts. But pre-tensioners are activated when the ABS or ESP kicks in. This happens in all the high end cars. I have felt the pre-tensioners first hand and I would say that the time between pre-tensioners and air-bags would be very distinguishable since a car may travel considerable distance after braking/swerving and before impact.
Not sure as to how it is in other cars.
But in a Fiat Linea EPK,the pre tensioners kick in pretty often,even on braking slightly hard,and even when ABS has not kicked in.
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Old 30th May 2013, 01:34   #74
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Default Re: Airbags deployed after hitting a dog. Understanding why?

^^ Those are not tensioners. That is just a mechanical lock which prevents the seat-belt from getting pulled further. The tensioners actually rewind the seat-belts with considerable force and pull the occupant back to the seat.
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Old 30th May 2013, 02:07   #75
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Default Re: Airbags deployed after hitting a dog. Understanding why?

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Originally Posted by Tejas Ingle View Post
^^ Those are not tensioners. That is just a mechanical lock which prevents the seat-belt from getting pulled further. The tensioners actually rewind the seat-belts with considerable force and pull the occupant back to the seat.
Wont the mechanical lock activate when the belt is pulled out to its full length?
What i experience is a push back to the seat and the belt tightens around me,not allowing me to move freely on the seat,i guess that is pre tensioner at work and not a Mechanical lock.
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