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Old 10-09-2018, 03:40 PM
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I'm in the hospital after car accident. Questions about G's

Hello Everyone,

I'm sitting in a hospital bed typing this on my phone. Last night I was in a pretty bad single car accident. I can only surmise that I possibly drifted off for a few secinds behind the wheel. My car left the road onto a very vey large shoulder. That's when i guess I came too.

The grass was wet and neither t the brakes nor the steering did much of anything.Apparently i jumped a driveway and went airborne about 30', then hit lets say a 40' tall pine tree head on.

I'm very bruised, especially where the seat belt and air bag hit me. I already have an injured back and it came out worst of all, I can barely move without screaming in pain. Although after seeing pictures of the car, I know that I'm very lucky to even be alive.

I can't say the exact speed that I hit the tree but I do know that I was going about 60 miles an hour on the road prior to leaving it. If I had to guess because I was well aware of the impact I guess I was traveling between 50 and 55 miles an hour when I hit the tree. I was driving a 2009 CX-9, which is a fairly big vehicle. It's kind of funny because when the impact happen I'm more heard it than I felt it and then I was out of it for a little bit .

I was wondering if any of you math types could take a guess of how many G's my body experience when it hit the tree? Maybe with the information I've given it's not possible to determine that but I just thought it'd be interesting to know. Thanks in advance and I'm happy that I'm still around to be able to talk.

Last edited by obbn; 10-09-2018 at 03:45 PM.
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Old 10-09-2018, 03:46 PM
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Glad you lived through it and are coherent enough to tell the tale!

The only G-force info I could find was related to acceleration, not sudden stops.
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Old 10-09-2018, 03:46 PM
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If any of your read that, I edited it. Sorry for the mistakes. I'm a but doozy.
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Old 10-09-2018, 03:52 PM
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Man, I don't know how hard you hit, but don't do it again. Seriously, glad you're ok. Modern cars are the shit when it comes to hitting stuff and living to tell the tale.
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Old 10-09-2018, 04:05 PM
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Here's a handy calculator from GSU. Note it gives force instead of gs, but just use 1 lb for mass and read the lb output as gs.

Speed is your guess. The big question is stopping distance. Basically, how far in the did the front of the car crumple? Seatbelts also play a role in stretching so that's something the calculator lets you play with.

I'm guessing something in the 50-80 gs range under ideal Physics. But a lot lower in real life. A survivable range for a split second.
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Old 10-09-2018, 05:01 PM
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Originally Posted by mind the gap View Post
Man, I don't know how hard you hit, but don't do it again. Seriously, glad you're ok. Modern cars are the shit when it comes to hitting stuff and living to tell the tale.
I can say without a doubt that the cars design team saved my life. I haven't seen it yet since the accident, but my wife brought me lots of pictures. The front end crumbles and you can easily follow the energy trail as more and more parts for destroyed. She said you can see the ground through the drivers floor.

When all was said and done there was barely enough space for my body in the seat. I couldn't open the driver for so had to crawl over the center console and out the passengers side.

I saw smoke and thought the car was on fire (it wasn't) so it's amazing how fast you can move while injured if you think you're about to become crispy! I got maybe to the back bumper before the pain kicked in.

I have zero doubt had I'd been driving a smaller car or not wearing my seatbelt, I'd be dead.
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Old 10-09-2018, 05:06 PM
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Man, I don't know how hard you hit, but don't do it again. Seriously, glad you're ok. Modern cars are the shit when it comes to hitting stuff and living to tell the tale.
That is total nonsense. Back in ye olden days, cars were solid, with steel chassis and it took a fair old whack to even bend a bumper. This meant that when they impacted a tree at speed a great deal of the energy involved was transferred to the occupants with catastrophic consequences.

Modern cars are designed to crumple and in doing so much of the energy is absorbed. Add in airbags and seat belts and the occupants have a considerably greater chance of survival and survival without life-changing injury.
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Old 10-09-2018, 05:06 PM
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If any of your read that, I edited it. Sorry for the mistakes. I'm a but doozy.
Are you saying you're ass sleep?
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Old 10-09-2018, 05:10 PM
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Originally Posted by bob++ View Post
That is total nonsense. Back in ye olden days, cars were solid, with steel chassis and it took a fair old whack to even bend a bumper. This meant that when they impacted a tree at speed a great deal of the energy involved was transferred to the occupants with catastrophic consequences.

Modern cars are designed to crumple and in doing so much of the energy is absorbed. Add in airbags and seat belts and the occupants have a considerably greater chance of survival and survival without life-changing injury.
Pretty sure that he meant "the shit" as a positive. Might be specific to the US.

Last edited by steatopygia; 10-09-2018 at 05:11 PM.
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Old 10-09-2018, 05:11 PM
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@bob++. I believe that in the phrase "the shit", the "the" essentially functions as a "not". English is the easy...

obbn, although I don't have an answer to your factual question about Gs, I'd like to offer my congratulations on not being dead. Have you also been considering the important scientific question about what sort of factors might have been involved in your nodding off briefly, and how to stop them happening again?
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Old 10-09-2018, 05:14 PM
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Impact metrics are generally stated in terms of peak acceleration levels--often stated as "g" (equivalent surface gravity of the Earth) = 9.81 m/s2 = 32.2 ft/s2 not "G" which is the acceleration constant--because acceleration is directly measurable and it is easy to calculate an equivalent inertial load, but it is actually the rapid change in acceleration (jerk in physics terms) which gives the actual impulse (force divided by time). A very rapid change in increase in acceleration will do more damage than a slower application both by dint of giving the body less time to respond and because the application of impulse will be localized to the first points of contact, hence why in a frontal impact the outline of the seatbelt can often be seen with distinct abrasions where the edges of the belt cut into the body.

Neither human or car bodies are rigid objects under heavy impact so in terms of damage the orientation of body with respect to the acceleration, how much of the impulse is absorbed or dampened by deformation, and how the body is restrained will dictate the experienced acceleration and what kind and how much damage will occur. A body can tolerate levels of a few hundred g of acceleration for brief periods, and accelerations in the tens of g for a few seconds. The Snell Foundation "2015 Standard For Protective Headgear For Use with Motorcycles and Other Motorized Vehicles" defines a maximum allowable peak acceleration of 275 g for an impact speed of 7.75 m/s as measured inside the helmet, which is supposed to prevent brain damage (concussion) for a frontal impact although the potential for damage has as much to do with the direction of impact as the experienced acceleration.

So for the o.p., I don't think there is a simple answer to your question. A rough guess for frontal impact at 60 mph in a modern automobile with an approximate 0.5 m effective crush zone is that the peak acceleration as experienced at the driver's seat is on close order of 80 g, but experienced peak acceleration will be reduced by both the airbag, stretch in the seatbelt, and any other occupant safety mechanisms, e.g. anti-whiplash devices. If your head or other body part impacted a solid surface, that would increase to hundreds or thousands of g and cause blunt or penetrating trauma, hence why modern occupant safety measures have reduced severe injury and death in moderate speed accidents, and have allowed survival in high speed accidents in which occupants would have otherwise exited the vehicle in an uncontrolled manner at a high rate of speed and be found a significant distance away from the impact site.

Stranger
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Old 10-09-2018, 05:16 PM
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Originally Posted by obbn View Post
I saw smoke and thought the car was on fire (it wasn't) so it's amazing how fast you can move while injured if you think you're about to become crispy! I got maybe to the back bumper before the pain kicked in.
Airbags can produce a pretty good cloud of crap inside the car. It's really disorienting and can lead to the fear of a fire.
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Old 10-09-2018, 05:32 PM
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Speed is your guess. The big question is stopping distance. Basically, how far in the did the front of the car crumple? Seatbelts also play a role in stretching so that's something the calculator lets you play with.
Here's a crash test of the 2008 CX-9. Stepping through frames, counting from when the bumper first touches the barrier, the driver's head moves about 50 inches before stopping. (I'm pretty sure the yellow/black stripes are 1 inch apart.) About half of that is the crumple zone crumpling, the rest is the seat belt stretching/slipping (also a safety feature) and the head moving forward.

Decelerating from 60 mph to 0 over 50 inch distance is an average deceleration of 29 G.

Of course the peak would be much higher. I wouldn't be surprised if it was double that.

Last edited by scr4; 10-09-2018 at 05:36 PM.
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Old 10-09-2018, 05:40 PM
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I can give you an approximate mathematical solution to your question, but it's only valid for spherical chickens in a vacuum.

Just kidding. Glad you survived!
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Old 10-09-2018, 05:45 PM
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Wow, I'm glad you're still able to post after that.

Modern car onboard computers will log all sorts of data about the vehicle speed, brake pedal position, throttle position, etc. for some time leading up to the event. Maybe even the peak G from the various accelerometers. It might be neat / super morbid to get a look at that data. Your insurance company might even do it routinely.
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Old 10-09-2018, 05:50 PM
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Holy smokes, that sounds terribly frightening. Glad you survived. I hope you find relief for the pain you are in. Heal well and soon.
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Old 10-09-2018, 05:55 PM
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That is total nonsense.
"Modern cars are shit" = bad.

"Modern cars are THE shit" = good.
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Old 10-09-2018, 06:06 PM
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Airbags can produce a pretty good cloud of crap inside the car. It's really disorienting and can lead to the fear of a fire.
They hurt like hell, too. But it WAY better than hitting a steering wheel or windshield.
OP, your are truly lucky. Send your wife out for lottery tickets. Good luck.
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Old 10-09-2018, 06:09 PM
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It's kind of funny because when the impact happen I'm more heard it than I felt it and then I was out of it for a little bit .
"The worst part was hitting the ground
Not the feeling so much as the sound
Can't help but wonder if all this is real 'cause
Tonight is the night I fell asleep at the wheel."
--Barenaked Ladies
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Old 10-09-2018, 07:59 PM
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Stranger, you might want to double-check that. Impulse (change in momentum) is force times time, not divided. Jerk is only relevant to the extent that you can brace yourself for acceleration.
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Old 10-09-2018, 11:02 PM
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The only G-force info I could find was related to acceleration, not sudden stops.
According to my amateur understanding of physics, G-force is the same no matter whether it's positive or negative (negative in the sense of stopping, not starting).
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Old 10-10-2018, 03:48 AM
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"Modern cars are shit" = bad.

"Modern cars are THE shit" = good.
OK - I get it now.
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Old 10-10-2018, 07:22 AM
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Oh, and
Quote:
Quoth scr4:

Decelerating from 60 mph to 0 over 50 inch distance is an average deceleration of 29 G.

Of course the peak would be much higher. I wouldn't be surprised if it was double that.
Actually, I'd expect that the acceleration would be fairly steady, with the peak not much greater than the average. Remember, it's all due to things specifically designed as safety features, and very well-engineered safety features at that. The crumple zones, seat-belt slip, and airbag would all be designed to provide a constant acceleration of just such a magnitude as to stop from 60ish MPH, in the distance available.
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Old 10-10-2018, 09:13 AM
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Here's a crash test of the 2008 CX-9. Stepping through frames, counting from when the bumper first touches the barrier, the driver's head moves about 50 inches before stopping. (I'm pretty sure the yellow/black stripes are 1 inch apart.) About half of that is the crumple zone crumpling, the rest is the seat belt stretching/slipping (also a safety feature) and the head moving forward.

Decelerating from 60 mph to 0 over 50 inch distance is an average deceleration of 29 G.

Of course the peak would be much higher. I wouldn't be surprised if it was double that.
I used to work for Ford in test crash analysis (they prefer to call them "barrier tests") and the cars were typically towed into a concrete barrier at 35 MPH to exceed the federal requirements for performance at 30 MPH. The tests were primarily to confirm steering column intrusion limits. I do not not if there are any regulations specifying performance at 60 MPH. This test was performed by an insurance institute, so it's not clear what they were evaluating here. Also, the crash was not into a fixed barrier (which simulates a head-on collision with an equal-mass vehicle going the same speed in the opposite direction) but rather a collapsible barrier, which also mitigates the impact. It also appears that the engine compartment is just shredded, so I don't know if that is a stock car.

Quote:
Originally Posted by obbn
Apparently i jumped a driveway and went airborne about 30'[....]
I thought that only happened in the movies. How can a car launch from flat ground to the height of a three-story building?

Anyway, I'm glad you survived it and here's hoping for a fast recovery.
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Last edited by CookingWithGas; 10-10-2018 at 09:14 AM.
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Old 10-10-2018, 09:19 AM
jz78817 jz78817 is offline
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That is total nonsense. Back in ye olden days, cars were solid, with steel chassis and it took a fair old whack to even bend a bumper. This meant that when they impacted a tree at speed a great deal of the energy involved was transferred to the occupants with catastrophic consequences.
this is not true. old cars were death traps because they were not designed to control or mitigate the crash energy in any way. Those "rigid" frames would buckle easily, the lack of a crumple zone meant the front/rear end just folded up uselessly, and the lack of a reinforced passenger cage meant the pillars would collapse and force feed you the dashboard and steering column.
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Old 10-10-2018, 10:40 AM
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this is not true. old cars were death traps because they were not designed to control or mitigate the crash energy in any way. Those "rigid" frames would buckle easily, the lack of a crumple zone meant the front/rear end just folded up uselessly, and the lack of a reinforced passenger cage meant the pillars would collapse and force feed you the dashboard and steering column.
This. Here's an offset-frontal crash test pitting a 2009 Chevy Malibu against a 1959 Chevy Bel Air. The Bel Air's passenger compartment gets destroyed (see at 0:50), and its driver eats the steering wheel. In contrast, the Malibu's passenger compartment is barely distorted at all (see at 1:08), giving the seat belt and airbag (and front crumple zone) a chance to safely decelerate the driver.

Based on the OP's description of his crash, if he (she?) had been driving a vintage car when he crashed, he'd be a mangled corpse today.

obbn, sorry for what you're going through. Hopefully your physical injuries will heal well in the coming weeks and months, but pay attention to your mental health, too. I was in a serious crash a couple of years ago, and although I escaped without any physical injury, it really messed with my head for a long time after. Look for friends and family to talk to about it - and, if necessary, professional help.
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Old 10-10-2018, 12:16 PM
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I thought that only happened in the movies. How can a car launch from flat ground to the height of a three-story building?
That seems to be horizontal distance there, not vertical.
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Old 10-10-2018, 12:31 PM
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I thought that only happened in the movies. How can a car launch from flat ground to the height of a three-story building?
Guessing OP meant a 30' horizontal flight distance - although with the right ramp/hill and enough speed, anything's possible. Here's a crash into the second story of a building.
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Old 10-10-2018, 12:57 PM
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That seems to be horizontal distance there, not vertical.
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Guessing OP meant a 30' horizontal flight distance
Thanks. That's still a pretty impressive long jump.
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Old 10-10-2018, 01:45 PM
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Stranger, you might want to double-check that. Impulse (change in momentum) is force times time, not divided. Jerk is only relevant to the extent that you can brace yourself for acceleration.
You are correct, I misspoke. However, jerk definitely does play into how the impulse is perceived and applied to a flexible body that may experience differences in acceleration at the different points at which it is applied, e.g. for an occupant in a forward impact, the head will experience a significantly different acceleration profile than the restrained torso, and how different depends on the rate at which acceleration changes.

Quote:
Originally Posted by Chronos View Post
Actually, I'd expect that the acceleration would be fairly steady, with the peak not much greater than the average. Remember, it's all due to things specifically designed as safety features, and very well-engineered safety features at that. The crumple zones, seat-belt slip, and airbag would all be designed to provide a constant acceleration of just such a magnitude as to stop from 60ish MPH, in the distance available.
It is the goal of all of those occupant safety systems to mediate the impulse and present a more constant level of acceleration rather than a dramatic peak. The energy being delivered will be the same at any level of kinetic energy, but how it is applied can be radically different. People often look at how older vehicles would survive an impact with repairable damage while a modern vehicle will experience crushing and deformation of the chassis, rendering it unrepairable, but that is exactly the point; it is cheaper to buy a new car than to rebuild a person, so the car is sacrificed to absorb as much energy as possible and mediate the rest of it, as well as to protect the occupant from direct impact with hard components. Surviving impacts at >60 mph in an unreinforced passenger car used to be virtually unheard of because even if the occupant was wearing a lap belt he or she would slam forward into the dash and suffer trauma to the head or being impaled upon the steering column. Now you actually have a pretty good chance of walking away from a frontal impact at that speed provided you are wearing your three point safety belt and don't choke on your chewing gum, and even rollover impacts are surprisingly survivable in many (but not all) vehicles. Oblique and side impacts are still pretty deadly just because of the limited ability to absorb and protect occupants but those are generally multiple vehicle collisions which can be reduced by active driver aids and (eventually) autonomous piloting systems.

Stranger
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Old 10-10-2018, 02:42 PM
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Airbags can produce a pretty good cloud of crap inside the car. It's really disorienting and can lead to the fear of a fire.
Airbags have a lot of powder which looks like smoke when they deploy. People, whether occupants or bystanders not-infrequently report a MVA (Motor Vehicle Accident) with vehicle fire based on the 'smoke' in the passenger compartment.


Quote:
Originally Posted by Stranger On A Train View Post
Impact metrics are generally stated in terms of peak acceleration levels--often stated as "g" (equivalent surface gravity of the Earth) = 9.81 m/s2 = 32.2 ft/s2 not "G" which is the acceleration constant--because acceleration is directly measurable and it is easy to calculate an equivalent inertial load, but it is actually the rapid change in acceleration (jerk in physics terms) which gives the actual impulse (force divided by time). A very rapid change in increase in acceleration will do more damage than a slower application both by dint of giving the body less time to respond and because the application of impulse will be localized to the first points of contact, hence why in a frontal impact the outline of the seatbelt can often be seen with distinct abrasions where the edges of the belt cut into the body.
There are three crashes, microseconds apart:
  1. Car hits object
  2. Occupant(s) hits car (steering wheel, dash, back of front seat, etc.)
  3. Occupant(s) internal organs hits occupant (rib cage, body walls)
The first one is always survivable; it's the second two that cause injury & death. Airbags & crumple zones help minimize the second & third crashes.


Quote:
Originally Posted by CookingWithGas View Post
I thought that only happened in the movies. How can a car launch from flat ground to the height of a three-story building?
If the car hits a ditch, the start of a Jersey barrier, or even a short but steep driveway ramp with enough speed they can go airborne. Here is a video of a crash that happened earlier this year where the car ended up embedded in the second story of a building.
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Old 10-10-2018, 07:09 PM
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You are very lucky to be alive. Just G-forces alone can certainly kill you.

Back in my LEO days, I had a guy who crashed a Fiero in almost the same circumstances. We determined he had three fatal injuries. He left his left leg in the car when he exited through the front window, which would have caused death by blood loss pretty quickly. The G-forces also caused a torn aorta (with no external chest injury), which would have caused very fast death through immediate loss of circulation and blood volume. But even that wasn't fast enough to be the real cause of death, because he flew headfirst into a really solid tree, and that was immediate lights out.
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Old 10-10-2018, 08:16 PM
Stranger On A Train Stranger On A Train is offline
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Back in my LEO days, I had a guy who crashed a Fiero in almost the same circumstances. We determined he had three fatal injuries. He left his left leg in the car when he exited through the front window, which would have caused death by blood loss pretty quickly. The G-forces also caused a torn aorta (with no external chest injury), which would have caused very fast death through immediate loss of circulation and blood volume. But even that wasn't fast enough to be the real cause of death, because he flew headfirst into a really solid tree, and that was immediate lights out.
And yet, surprisingly, the car didn’t catch on fire.

“Can’t trust them foreign cars, ya’ know?”

Stranger

Last edited by Stranger On A Train; 10-10-2018 at 08:17 PM.
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Old 10-10-2018, 09:21 PM
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I, for one, am glad the OP doesn't, "NEED ANSWER FAST."


Get well.
  #35  
Old 10-11-2018, 03:27 AM
EdelweissPirate EdelweissPirate is offline
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I can say without a doubt that the cars design team saved my life. I haven't seen it yet since the accident, but my wife brought me lots of pictures. The front end crumbles and you can easily follow the energy trail as more and more parts for destroyed.

[snip]

I have zero doubt had I'd been driving a smaller car or not wearing my seatbelt, I'd be dead.
First of all, I think everyone on this board (to say nothing of you and your family) is delighted that you are not dead.

Youre right to credit the various crumple zones with your survival. However, the sheer size of your car is probably a red herring, especially in a collision with a quasi-fixed object like a tree.

A well-designed smaller, lighter car would have protected you at least as well as your Mazda CX-9. As an extreme example, a Formula One car has perhaps 15-20% of your Mazdas mass, but protects its occupant well against much worse impacts than yours.

Im not suggesting that a small car would have been more protectiveIm just saying that the protection came from the quality of the engineering (specifically, of the explicit dynamics simulations) rather than the mass of your car.

The more mass involved, the more energy the crumple zones have to absorb. In many situations, increasing mass is basically (from a safety perspective) a zero-sum game. Head-on collisions with another vehicle are different, though, and not in a good way. More mass protects the occupants of the heavier vehicle at the expense of the occupants of the lighter vehicle. It quickly becomes an arms race and/or tragedy of the commons.

Again, the important point is that youre alive and kicking. I hope you heal quickly!
  #36  
Old 10-13-2018, 01:53 AM
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Airbags have a lot of powder which looks like smoke when they deploy. People, whether occupants or bystanders not-infrequently report a MVA (Motor Vehicle Accident) with vehicle fire based on the 'smoke' in the passenger compartment.




There are three crashes, microseconds apart:
  1. Car hits object
  2. Occupant(s) hits car (steering wheel, dash, back of front seat, etc.)
  3. Occupant(s) internal organs hits occupant (rib cage, body walls)
The first one is always survivable; it's the second two that cause injury & death. Airbags & crumple zones help minimize the second & third crashes.



If the car hits a ditch, the start of a Jersey barrier, or even a short but steep driveway ramp with enough speed they can go airborne. Here is a video of a crash that happened earlier this year where the car ended up embedded in the second story of a building.
Oh, to clarify, I traveled about 30' THROUGH the air after hitting the driveway. I don't know how high, but I do know you can clearly see skid marks, driveway, no skid marks and then see where the car came down again.

Last edited by obbn; 10-13-2018 at 01:56 AM.
  #37  
Old 10-13-2018, 06:28 AM
Quartz Quartz is offline
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I can attest first-hand to the efficacy of seatbelts and crumple zones. Get well soon. There is one thing I regret: not taking a photograph of the impressive bruise the seatbelt left.
  #38  
Old 10-13-2018, 07:00 AM
Quartz Quartz is offline
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The only G-force info I could find was related to acceleration, not sudden stops.
A sudden stop is negative acceleration.
  #39  
Old 10-13-2018, 08:31 PM
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I can attest first-hand to the efficacy of seatbelts and crumple zones. Get well soon. There is one thing I regret: not taking a photograph of the impressive bruise the seatbelt left.
I took one and you aren't kidding. The bruise on my left thigh from the lap belt is HUGE and horrible. Doesn't hurt but looks nasty!
  #40  
Old 10-13-2018, 08:44 PM
obbn obbn is offline
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I can attest first-hand to the efficacy of seatbelts and crumple zones. Get well soon. There is one thing I regret: not taking a photograph of the impressive bruise the seatbelt left.
If you are interested here's a picture of the seatbelt bruise and what's left of the Mazda

Bruise
https://www.dropbox.com/s/m7cif7osuq...29562.jpg?dl=0

Mazda

https://www.dropbox.com/s/clecdcy1ev...07402.jpg?dl=0
  #41  
Old 10-13-2018, 08:59 PM
Joey P Joey P is offline
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Originally Posted by obbn View Post
If you are interested here's a picture of the seatbelt bruise and what's left of the Mazda

Bruise
https://www.dropbox.com/s/m7cif7osuq...29562.jpg?dl=0

Mazda

https://www.dropbox.com/s/clecdcy1ev...07402.jpg?dl=0
You got a free hood ornament, so there's that.
  #42  
Old 10-13-2018, 09:26 PM
obbn obbn is offline
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You got a free hood ornament, so there's that.
You noticed that too? Amazing that pine cone!
  #43  
Old 10-14-2018, 01:32 AM
DesertDog DesertDog is offline
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I have zero doubt had I'd been driving a smaller car or not wearing my seatbelt, I'd be dead.
Seat belt almost certainly but small cars can be surprisingly strong. A couple months ago I saw a BBC program where they wound up running a SmartCar -- with a titanium cage -- into a block of concrete at 70-mph. It was one of those worst case scenarios where the block ended at the mid-point across the car's front so you got a lot of sheer.

The presenter was standing by the remains and said, "Now, we're not meaning to imply you could survive running into a wall at 70 miles per hour, but the titanium worked." He opened the door then closed it again. "It won't be because the cabin collapsed."
  #44  
Old 10-14-2018, 03:47 AM
Quartz Quartz is offline
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I took one and you aren't kidding. The bruise on my left thigh from the lap belt is HUGE and horrible. Doesn't hurt but looks nasty!
I had a huge bruise diagonally across my torso. I went swimming perhaps a week later and it still drew stares. Wear your seat belts, folks!
  #45  
Old 10-14-2018, 03:48 AM
Quartz Quartz is offline
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Originally Posted by obbn View Post
If you are interested here's a picture of the seatbelt bruise and what's left of the Mazda

Bruise
https://www.dropbox.com/s/m7cif7osuq...29562.jpg?dl=0


Good crumple zone, that!
  #46  
Old 10-14-2018, 08:43 AM
MarvinKitFox MarvinKitFox is offline
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... then hit lets say a 40' tall pine tree head on.
... I guess I was traveling between 50 and 55 miles an hour when I hit the tree. .
.. if any of you math types could take a guess of how many G's my body experience when it hit the tree?
2009 car would have decent crumple zones. Assuming a central head-on collision (worst case), the interior of the car experienced about 120g of deceleration.
The airbag adds another 40-50cm of travel for your body though, reducing your head and torso g-force down to about 45g, with a nice even distribution of pressure over the airbag area.

This is survivable, and you should not have *broken* ribs, back or skull. Back dislocations likely, bruising both surface and internal guaranteed. Concussion very likely, but also most likely mild.
Your limbs, not being constrained by the airbag(s), would experience a good bit more violence, and bone breaks and/or dislocations and/or tendon and muscle damage is purely up to luck. Fortunately, your limbs are both more robust and less vital than the torso or head.

In short.
That you are awake, and coherent enough to type this on the day following the accident, means that you were quite lucky. Surviving the crash was expected though.

Update, after seeing photo of your car.
That was a glancing hit, reducing the impact force by about half..(by roughly doubling the distance over which the damage occurred)
So downgrade the personal G to about 30, but add a sideways twist to it. Much less bruising, more dislocations and wrenching of the spine.

Last edited by MarvinKitFox; 10-14-2018 at 08:47 AM.
  #47  
Old 10-14-2018, 09:05 AM
Quartz Quartz is offline
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It's just struck (ahem) me that you drive on the other side of the road so that's a driver's side impact.
  #48  
Old 10-14-2018, 12:17 PM
Patch Patch is offline
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From your photo I have a few questions.

It looks like an offset frontal hit on the right side, as that's where the bumper is pushed back the most. As it's an offset hit that will cause your vehicle to rotate, which is what I suspect your vehicle did? The disturbed ground around the front of the vehicle suggests this happened as well. That will reduce the g's you experienced as your vehicle has the energy to continue moving.

I also notice that your left from quarter panel, and headlight assemble, is trashed or simply missing. That's not induced damage, so you hit something else, and I don't know when or what. Did you hit more than one tree, or did you take out something else when you left the road?

Back to the g's issue.

Looking at the car, from my own experience, I think you're somewhere in the 20s for g forces, and you experienced a combination of longitudinal and lateral g's. I'd need more information than what you have to determine what you experienced. Right now, with what's available, I don't think it can be calc'd.

If you really wanted to know, you may be able to get data from the airbag control module (I don't have info at hand to say what's recoverable from that model year). That would give you at least a delta-V for impact, and may also give you a speed at impact.

And yeah, that is a lovely hood ornament you have there.
  #49  
Old 10-14-2018, 02:06 PM
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Gatopescado Gatopescado is offline
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How is the tree?
  #50  
Old 10-14-2018, 05:15 PM
Patch Patch is offline
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Originally Posted by Patch View Post
From your photo I have a few questions.

It looks like an offset frontal hit on the right side, as that's where the bumper is pushed back the most. As it's an offset hit that will cause your vehicle to rotate, which is what I suspect your vehicle did? The disturbed ground around the front of the vehicle suggests this happened as well. That will reduce the g's you experienced as your vehicle has the energy to continue moving.

I also notice that your left from quarter panel, and headlight assemble, is trashed or simply missing. That's not induced damage, so you hit something else, and I don't know when or what. Did you hit more than one tree, or did you take out something else when you left the road?

Back to the g's issue.

Looking at the car, from my own experience, I think you're somewhere in the 20s for g forces, and you experienced a combination of longitudinal and lateral g's. I'd need more information than what you have to determine what you experienced. Right now, with what's available, I don't think it can be calc'd.

If you really wanted to know, you may be able to get data from the airbag control module (I don't have info at hand to say what's recoverable from that model year). That would give you at least a delta-V for impact, and may also give you a speed at impact.

And yeah, that is a lovely hood ornament you have there.
My bad, I'm thinking about delta-V (I use that more than Gs). Have to think about this a little more.
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