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Many people might not know, but the primary purpose is not to simply stop the passenger's inertia in a collision, but rather to stop it in a non-lethal manner.
Instead of jerking to a painful, and in some cases harmful stop, why not add a little give to the seatbelts? At the seat connection node,
add a thick elastic cord in parallel with a slightly longer steel cable.
In the event of collision, the passenger will first be slowed down by the elastic, before completely stopped by the steel, dissipating inertia in a slower and safer manner.
Trials
http://www.billfrye.../newimages/cat5.jpg
The early experimental stages and clinical trials of [Aq_Bi's] invention were a huge success. [skinflaps, Aug 16 2005]
[link]
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So after they are flung through the windshield at an alarming rate, they will be sprung back in again and slammed down onto the chair? Interesting |
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There is a small movement on current
designs of seatbelt and I'd rather keep ti
that way... unless you want to move the
dashboard a few feet further away. |
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My car has pyrotechnic (something to do with fire and Lego apparently) seatbelt tensioners - how would this invention affect those? |
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What [st3f] said. In the only accident I’ve had, the seatbelt stopped me with my face an inch from the steering wheel. I wasn’t injured by the seatbelt through my coat, but given the choice, I’d choose a broken collar bone over face/head injuries. |
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To put [stf3]'s comment another way, seatbelts ARE elastic already, and to make them any more elastic than they are would be dangerous. |
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You missed the point of the steel cable. The seatbelt would not be able to extend farther than it would normally. The elastic cord would only be in effect in the short space already present before completely stopping the passenger. |
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It's similar to the automatic tightening mechanisms, but does so with a more gentle spring force, before the full stop. |
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At the decelerations and forces present in a front-on collision, webbed seatbelt material is already quite springy (and so is steel cable!) |
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Even at 40km/h, going from 40 to zero in 0.5m is going to take some very strong and only very slightly springy material. |
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//a more gentle spring force// will have almost no effect, what you want is a very stiff spring that decelerates your upper body from 40 to 0 in a few milliseconds! The force on your body attached firmly to the car frame (spread out on the seatbelt web) will be far less than if your body is allowed to continue moving at 40km/h for another (0.5) meter before it hits the steering column. |
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Another way of looking at this is to see that starting to decelerate sooner is better, as what causes damage is rapid deceleration over a short distance. |
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The pyrotechnic tighteners start deceleration as fast as possible, giving the longest possible time to decelerate. |
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Bone - (you'll need several to replace the broken ones if you implement this.) |
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Take it from a former Ford seat belt engineer: seat belts are designed with very specific tensile requirements of elasticity. |
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Making them more compliant would be a very bad idea. |
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Since I've moved on, I'm uncertain if they've moved in the direction towards more non-linear strain behaviors. |
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Always have your seatbelt replaced when you get into a serious accident. Many are designed with specific tear-strips that give once a certain threshold is reached that are only good for one go-round. Pyrotechnic seatbelt tensioners are also very common, although not so much in the rear seats. These should also be replaced. |
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This idea is a bizarre combination of already-baked and bad science. |
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[copro] mentioned a device that, if I remember rightly, is designed to take up all the remaining slack in the belt in an impact. I'll let the car take care of decelerating my body carefully - that what it's designed to do, and what all those government crash tests are about. As for the belt, snug it down! In a wreck, the last thing you want to be doing is flopping about inside a big rubber band. |
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Some of the fastest and most violent impacts are experienced by race-car drivers, who invariably walk away from the crash because they were belted in tight.
The belts are pulled VERY tight to ensure the driver hardly moves at all relative to the seat. All the deceleration is designed to be performed by the chassis of the vehicle. It's not usually practical to install a full harness in a road car, but it still makes sense to make the belts as tight as possible and allow the 'crumple zones' to take the energy out of the crash.
Even tightly belted in, there are a lot of hard objects very close to the driver, so adding any elasticity to the belt would probably increase the risk of hitting them in a violent crash. Airbags, collapsible steering columns and softer surfaces near the driver's head and knees would seem to be the way to go. |
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Good anno's. Goes to show it's very
difficult to implement a single change
that will improve a complex product,
especially one into which a great deal of
resources have been directed. |
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[Mash], very succinctly put. |
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Pardon the advocacy, but please wear
your seatbelt Every Single Time. |
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