HTY67

Just another note: You're not looking for a threshold speed or even a threshold force, you're looking for an acceleration. The acceleration will depend on the masses and relative velocity and intercept angle of the vehicles, but the SRS unit has no way of measuring these values. All that is important is the acceleration (both magnitude and direction) than an occupant would experience.

HTY67

If the SRS unit were connected to your speedometer then if you locked up your brakes your wheelspeed and speedometer would instantly drop to 0mph, triggering your airbag. Wouldn't that ruin your day!

97ej6dx

They have it on Wikipedia also on the NHTS Website and they mention it in the Vehicle Importation rules and regulations because other countries have diff airbag standards.

97ej6dx

we covered that man lol but it is Forces equal to a 14 mph frontal impact via mercury switch or accelerometer depending on the year of the car

HTY67

Well I read the other posts and I wouldn't say it was covered, at least not very well. My point is what exactly is a 14mph frontal impact? That really means nothing in engineering terms. It's insufficient to describe the situation. 14mph into an immovable object or another vehicle? Knowing the actual acceleration at the location of the SRS unit would describe the situation without ambiguity.

If the standard is indeed a 14 mph frontal, head-on impact into an immovable object made of a certain material, then the acceleration experienced by the occupants will vary based on the design of the vehicle, which makes that a pretty crappy standard. Each vehicle's SRS unit would have to be triggered at a different acceleration to achieve a 14mph threshold,. A stiff-framed truck which comes to a stop over a very short distance would impart a larger acceleration on the occupant (and it's SRS unit) at 14mph than a Civic which would deform more.

97ej6dx

Forces equal to an average weight of a mid sized car hit the car which is What ever the curb weight of the car. I haven't read in depth about what the forces grams per cubic centimeter or pounds per square inch. The exact PSI required to set off the airbag sensor would have to be info that Honda would have due to the individual mass of each car being different. But he wanted the Speed particularly Btw this is all average as is most of the NHTS data otherwise the specs would be on a 1000 page book for all of the different massed vehicles

HTY67

Well change PSI to any unit of acceleration and you'd be mostly right. And I know he wanted speed, but the point is that he's a moron and didn't know what he wanted. Speed has nothing to do with it. Airbags are triggered by acceleration.

97ej6dx

lol cant argue with you there i tryed to tell him that speed had nothing to do with it but.. "that wasnt the question" talk about hating to be wrong reminds me of my sister

99r

No see I'm not a moron I know speed isn't the factor. I'm completely let me put that again COMPLETELY aware of that. I do know how ever that if you hit a wall at X amount of speed that your mass will decelerate at a rate of Y. I want to know X.

let me put it how you'll understand it:
As in Car A hits the side of Car B Right when its VTACK hits. Whats the minimal speed Car A has to be going in VTACK to make enough force (X) to make the minimal rate of deceleration (Y) for the air bags to go off?
A+B/VTAK^2=X Xf-Xi/time (or distance)=Y

RyanA

Well, you need to give us a little more information so we can better help you then.

1. If it's a stationary object, what is its composition? If concrete, what is the mix/density? If a stick built structure, what size are the studs and what center are they installed? If it's a ditch, is it loose pack dirt that's bare, loose pack with foliage, is it clay that's bare, clay with foliage, rock (if so, what size rock, depth of rock and base material it's on), is it a culvert? What angle is car in question hitting the stationary object? What car are you using to hit the object? Is it stock height or lowered? Are you already on the brakes? If so, at what rate are you decelerating? If you are not on the brakes, did you swerve at the last split second to help further absorb impact?
2. If it's a moving object, what kind of car or truck are we talking about? Is it stock height? If a truck, does it have a push bumper? If you rear ended the truck, did it have a hitch? What is the weight of the vehicle at time of impact and also its speed? Were they swerving to miss? What car/truck were you in? What speed were you going? On a straight or on a curve? Did you swerve to miss at last second? Answer all other questions that are in number 1 if they pertain to number 2.
3. What type of road surface are you travelling on? If gravel or non paved surface, what is the composition, density and humidity? If a paved surface, what is the finish of the surface? Are there ruts in the road from heavy traffic? Is there dew or moisture on the highway? Is there snow on the road?
4. If the impact occurred on the road surface, we need to know length of black marks, how black they were so we can determine if it was a threshold or full lock braking stop, etc. Are there skid marks after the impact? If so, what did they do, what are their length, etc? Need to know all of this information so we can determine how much of the energy was absorbed by the vehicles (that is why we need post impact skidmark information)

Answer those questions and then we can ask about another 25 or 30 questions to give you a fairly accurate answer. Yes, I have done accident reconstruction so you have to answer all of the questions above.

As you said, you are not a moron. You already knew this and were just waiting for us to ask you just to make sure we knew what we were talking about.

So, let us know those answers and we can go from there.

RyanA

Quoted from your ORIGINAL post that started this thread. NO, you did not ask anything about speed........

On another note, you never did tell us what 99 Civic you speak of. Coupe, hatch, or sedan? They all have different weights and crash test results. Did it have ABS? Auto or 5 speed? What trim level? We need all that to determine the deceleration capability and also the weight.

sde780

ITT: OP is a douchecanoe

HTY67

LOL LOL LOL HA HA HA, HA HA HA, HA HA HA

Seriously OP, your going to get an F- on this assignment if you don't take my advice. I have an MSME. I know this stuff.

Your equations don't make any sense. EG, (Xf-Xi) / Time = VELOCITY, not acceleration (Y) as you put it. The other equation you gave is chicken scratch, rambling nonsense, not kinematics, not conservation of momentum, just total crap.

For your purposes this is a simple inelastic collision event, where momentum is conserved but energy is not (energy is lost to deformation of the vehicles). You'll have to make some assumptions, and I'm guessing the acceleration at which the airbags deploy is one of them since you're not likely to find that easily. Make an educated guess, I'd say 2g's, 3g's or something reasonable. 20g's is about where you die regardless of whether you have an airbag or not (your neck stretches like a rubber band due to the inertia of your head).

You ought to post some more information on what you're trying to do. I'm guessing this has to do with some type of class assignment. You probably need to accept that you won't find actual data on the threshold acceleration for airbag deployment and you'll need to make an assumption and move on.

RyanA

I have this really weird feeling he is asking this because he was in an accident with his 99 Civic and they are saying speed is involved. He's butthurt because he's getting ready to get raked over the coals but his airbags did not deploy. Because of this, he thinks he has some sort of loophole that may get him out of trouble. If it was for a paper, there is a plethora of information to be found on the internet. However, he is looking for very specific information; this makes me think there is a reason he's asking for such specific information.

If you WERE in an accident and you are trying to find solid evidence, all you need to do is pull your airbag module and have it sent in and data pulled out of it. It will tell you EXACTLY what the module saw the 5 seconds before the "wake up hit" or airbag deployment. That's right, I said wake up hit. If the module sees something it believes could be an accident, it saves the 5 seconds of data leading up to that event. Send your module in along with full payment and they'll give you a nice printout of what happened up to that point. That evidence would be admissible in a court of law. Hearsay on Honda-Tech.com is not....

99r

^ the equation was a joke. lol relax.
a = Δv/Δt = (vfinal - vinitial) / (tfinal - tinitial)
Acceleration:
http://www.1-formula.com/physicians-...-formula1.html

This actually has to do with proving that I was going under 15 mph in a crash.
Thats why I need actual specific information.

Ryan since there's a bunch of people who have no idea what they are talking about I will answer all your questions in a pm seeing as how you actually know what your saying.

As for sde780, I'm not a douche bag I just would like a specific answer from intellectual people. The only people who have been replying are morons. "They can go off at 0mph".

Theres two people who are actually smart and I appreciate them but people like you who say crap completely irrelevant are pissing me off.

99r

No I'm not going to get raked. I have a solid case and its going to be dismissed because the cop is a moron and made over 30 errors on the very simple fill in the blank accident report.
Its just one more thing to tack on to his screw ups.

The air bags did not deploy, the insurance has the car and its probably some where over seas in an auction.
I wouldn't be using the hearsay from honda tech. But like your talking about, the factors your wanting to know I'm going to use to prove the point.

97ej6dx

the feelings mutual

RyanA

You need good pics of the scene of accident, pics of both cars, skidmark data, and pretty much all of the conditions. Your accident report should have road conditions, road surface type, possibly grade, etc. If you have skidmark data, I have a couple formulas I have used to determine MINIMUM speed if the car did not hit another object. If you did hit another object, the speed will not be accurate but you will know that the car was traveling above that speed.