collision engineering 3

[tecnos]

hello

anyone involved in automotive collision engineering?

I would like to know:

1) do we have the materials/design/technology etc to create a totally unbreakable capsule or car body ? under velocities that todays car can achieve, like 100mph etc

2) do we have the materials/design/technology etc to create a capsule/car body that when the human inside will not have serious injuries in a collision under velocities that todays car can achieve, like 100mph etc

where are we now exactly?

thanks!

 

[tecnos]

it's frightening that it took many years and deaths for HANS device to be accepted

 

[LittleInch]

Not as many deaths, injuries and years as seatbelts in "normal" motor cars.... It has taken legislation in most countries to both require front and back belts to be fitted and to force people to wear them...

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BrianPetersen]

"Hydraulic cylinders" ... "Springs" ...

Even if this were somehow feasible (did you watch the video that I posted), which way do you point them? Collisions can come from any angle and speed.

How about the air bag systems and pretensioned seat belt systems that cars already come with? Doesn't help the bodyshell, which does the job that it's designed to do by crumpling, but it helps the occupants.

 

[tecnos]

we can position them to protect from both frontal and side collisions (placed perpendicularly)

as for improving the air bag systems, I would like to know if there is still a big fatal factor the fact that passengers get smashed in rigid parts of the car, like the cockpit, the front window, etc
if yes, then we can introduce whole body airbags
and maybe fill them with some kind of foam, instead of air, to increase their elasticity

as for improving seatbelt systems, we can introduce a system that will encapsulate the passenger in in the seat, like some arms extending from the seat and seal him to the seat (not sure if you get what I mean)

 

[drawoh]

ok, maybe not ejection seats but a mechanism that will move the seat to the top of the car and let the left of the car crash beneath and absorb the whole energy?

I cannot remember my source for this, but I read somewhere that four out of five people thrown clear in car crashes are killed. Generally, particularly in modern cars, you want to stay inside the vehicle during a crash.

Ejection seats are for when you discover a supervillain in the seat next to you.

--
JHG

 

[IRstuff]

"we can position them to protect from both frontal and side collisions (placed perpendicularly)"

The Insurance Institute for Highway Safety (IIHS) spectacularly demonstrated the fallacy of such as design requirement more than 20 years ago by having a car impact a typical access restriction post and showing the degree of damage that would cause to the car and occupants. While the auto companies bitterly complained about the test being outside of the federal standards, almost all cars designed since then can survive such a crash without serious injury to the occupants, and at fairly high speeds. The federal standards were designed with the collusion of the car makers, so that minimal damage to the cars would occur, but the IIHS has a different mandate from equally well funded special interests.

"as for improving the air bag systems, I would like to know if there is still a big fatal factor the fact that passengers get smashed in rigid parts of the car, like the cockpit, the front window, etc
if yes, then we can introduce whole body airbags
and maybe fill them with some kind of foam, instead of air, to increase their elasticity

as for improving seatbelt systems, we can introduce a system that will encapsulate the passenger in in the seat, like some arms extending from the seat and seal him to the seat (not sure if you get what I mean)"

There are very specific reasons why airbags are the way they are, which is due to the fact that they have to fully deploy in less than 100 milliseconds. And, they have to essentially provide nothing solid to hit the occupant as they impact the airbag. Given those constraints, there is almost nothing else that will do the job. And, that's why higher end cars have a multitude of airbags specifically to protect the occupant from impacting other obvious parts of the compartment. Other reasons for NOT using mechanical structures is the degree of difficulty in extracting the occupant from the vehicle after the crash and before they burn or bleed to death. Having to cut through a deformed car frame is bad enough, but to then have to cut through additional metal to get inside is just more deaths waiting to happen.

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[BrianPetersen]

Modern airbag systems are already coming pretty close to "encapsulating" the passengers. Modern interiors are designed to minimize occupant impact with hard structures ... provided that they wear their seat belts. Biggest problem nowadays is people that don't wear them. They are (almost) on their own, with regards to the possibility of being ejected.

Side impact is a big problem. It is impossible to build sufficient "crush zone" into the side structures of a vehicle while keeping the vehicle at a practical width. The modern approach is to make the side structures as rigid as possible and then rely on the crush zone of the impacting vehicle. It does not help the person who goes off the road and then sideways into a tree.

There will always be impact scenarios that we can't realistically help. Commonly heard ... "I hit something in my car and the air bag did not go off!" Well, guess what, that statement is coming from someone who survived! The "smart airbag" controller took into account the magnitude of the impact and the weight of the person and the status of their seat belts and decided that it was not necessary to fire the air bags. And there is good reason for this. Suppose you have a double impact - a minor glancing impact with (say) a small deer, followed by the car going off the road and a blunt impact with a large tree. Airbags can only protect once! If the airbags went off at the slightest provocation, they would fire unnecessarily at the minor impact when they weren't really needed, followed by not being there for the second impact when they were really needed.

Some of your suggestions are completely off the wall. "Foam, instead of air"? Riiiight. How do you propose to inflate that in milliseconds as required?

Honestly, the best direction for vehicle safety going forward is to prevent the collisions in the first place. If you prevent the collisions, you don't need the crash protection. Realistically, the collision protection is going to stay, but further development is heading in the direction of preventing collisions.

 

[KENAT]

tecnos, maybe you should be working on force field technology, or something along the ERA lines.

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[Tmoose]

"Buy a helium balloon and tie it to the passenger seat belt in your car with the balloon extending over the head rest. Accelerate and see where the balloon goes. "

If the ballon is on a string I believe it will curioiusly lean "into" corners or forward on acceleration due to its bouyancy and the stratified air sloshing in response to gravity.

 

[BrianPetersen]

Filling the doors with foam doesn't increase the amount of crush distance. The existing steel structures in the doors already include anti-intrusion structures. Foam doesn't magically make the need for a controlled deceleration pattern go away. No, you cannot inflate foam in milliseconds as required. I'd like to see what your proposed "elastic polymer compressed and let it loose" would look like and function.

How about you store a small amount of reactive chemicals inside a folded plastic bag and ignite it to inflate the plastic bag to cushion the occupants from impact?

 

[1gibson]

Well, star for that one BrianPeterson.

 

[msquared48]

Or you could use an embedded C4 shaped charge to counter the impact force... Or not.

Mike McCann, PE, SE (WA)

 

[IRstuff]

"I don't know if you can inflate a foam airbag in milliseconds, I would need to calculate it, maybe with the correct (higher) amount of pressure, you can"

You can't, that's why current airbags are essentially tailored explosions. No chemical reaction, other than an explosion, and no pressurized gas can achieve the deployment speeds; they've already spent the money to prove that other approaches aren't fast enough.

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[tecnos]

Thank you all for your input.

 

[BrianPetersen]

You may wish to start with the requirements of the Federal Motor Vehicle Safety Standards:

http://www.nhtsa.gov/cars/rules/import/fmvss/

You may wish to explore Youtube for videos of crash tests by IIHS on existing vehicles. Here is an example of the new "small overlap" frontal impact for a new vehicle that was designed with this test in mind. Note that although there is plenty of destruction to the front of the vehicle, the driver's door remained pretty much intact (the skin was damaged but the underlying A-pillar kept its general shape - visible in the photo after the door was removed to show it - there is some deformation, which is hard to avoid in this type of test), and the windshield didn't even break. The driver's head was cushioned. In the video, the driver's seat headrest had been removed for visibility, but in reality the rebound of the driver's head would have been contained by the headrest.

Think you can do better?

 

[IRstuff]

"maybe not ejection seats but a mechanism that will move the seat to the top of the car and let the left of the car crash beneath and absorb the whole energy"

Ignoring ALL of the other engineering impossibilities inherent in this, it would take something like 500 g's of acceleration and deceleration, which is NOT survivable. And now you are outside of that nice, strong, metal container that was specifically modified to protect you from injury, with just a seat flying through the air, and very likely to be bouncing down the road, unprotected, at 65 mph because your car is now 50 ft behind you, having been stopped by its collision.



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[BrianPetersen]

Oops, here is the low-offset frontal video that I was discussing.

https://www.youtube.com/watch?v=GqIdsH_ebAQ