Squashed tuna cans - Page 3 - PeachParts Mercedes-Benz Forum

aklim · #31 06-12-2009, 01:37 AM

Quote:

Originally Posted by WVOtoGO

Bingo. Now, we actually have a real winner.

Best line of the thread so far.

To think that one can judge the overall safety of a car from its mass...
Or from a photo...
Or from the results of a single accident you happen to know about...
Or who built it, for that matter...

is nuts.

- S

Imagine 2 cars hitting a wall at 50 mph. Which one exerts more force on the wall? The 1500# car or the 3000# car?

Is that an absolute equation? Probably not when you consider all the factors involved. However, which one is generally favored?

WVOtoGO · #32 06-12-2009, 01:46 AM

Favored for what?

On the subject of driver/occupant safety - don’t confuse the kinetics of the body of steel and plastic with the kinetics of the body inside it.

It’s easy to imagine a mass and its resultant force upon hitting a wall.
In doing so, it’s also easy to conclude that the mass that is capable of doing the most damage to the wall is also the safest mass to be within during the impact. That’s often a grave conclusion.

If we’re talking about occupant safety… It is not the force upon the wall we are so concerned with. It’s the force transmitted to the occupants.

WVOtoGO · #33 06-12-2009, 01:49 AM

The last thing I want to do is get into a lecture on Dynamic Overshoot and such issues at 0100.

- Shelby

aklim · #34 06-12-2009, 01:55 AM

Quote:

Originally Posted by WVOtoGO

Favored for what?

It’s easy to imagine a mass and its resultant force upon hitting a wall.
In doing so, it’s also easy to conclude that the mass that is capable of doing the most damage to the wall is also the safest mass to be within during the impact. That’s often a grave conclusion.

In terms of which one will impart more energy to the wall.

I'm curious now. Why do you say that? If I plot two opposing vector components, the bigger one cancels out the smaller one doesn't it? After all, if they are equal, they have a net zero effect. If one is bigger than the other, doesn't the vector diagram show that when a level 3 vector meets an opposing level 4 vector, the net result is that it becomes a level 1 vector moving in the direction of the level 4 vector?

cmac2012 · #35 06-12-2009, 01:58 AM

Quote:

Originally Posted by aklim

Which has what to do with the issue? I am safer in a bigger box. I can make the money back much easier than rebuilding my body. Gas might be ending tomorrow or next year or next century but that has nothing to do with the issue.

Sorry Boskowitz. It has everything to do with why more and more people are going to smaller cars.

aklim · #36 06-12-2009, 02:01 AM

Quote:

Originally Posted by cmac2012

Sorry Boskowitz. It has everything to do with why more and more people are going to smaller cars.

Well, if my mass keeps me safer and they want to go into smaller cars, I'm good with that. Like I said, I can rebuild my wallet a lot easier than my body.

Jim B. · #37 06-12-2009, 02:05 AM

Quote:

Originally Posted by WVOtoGO

I’m not 100% on this, but didn’t the crew from Top Gear stage a head-on with something like a big Volvo and some small econo-car, with some interesting results?

- Shelby

It was this one, Shelby.

http://www.youtube.com/watch?v=k3ygYUYia9I

WVOtoGO · #38 06-12-2009, 02:17 AM

Quote:

Originally Posted by aklim

In terms of which one will impart more energy to the wall.

I'm curious now. Why do you say that? If I plot two opposing vector components, the bigger one cancels out the smaller one doesn't it? After all, if they are equal, they have a net zero effect. If one is bigger than the other, doesn't the vector diagram show that when a level 3 vector meets an opposing level 4 vector, the net result is that it becomes a level 1 vector moving in the direction of the level 4 vector?

Yes. You are correct.
But that’s not what automotive safety (in a crash) is all about.

Think about the two vehicles and the wall again:

The 3K lb vehicle hits a solid wall at 20 mph. It is a vehicle designed to absorb the impact. The front crushes. The engine ejects (thanks VW) out the bottom. Airbags deploy. Etc. etc. X number of G forces are experienced by the occupant for Y number of seconds as they decelerate to a stop. They live.

Same wall. Same speed. But now a 6K lb vehicle built solid as a rock (like those cars in the 50s/60s). This time, the deceleration rate is way too high. Very little kinetic energy is transmitted from, or absorbed by, the vehicle throughout the deceleration process. Way too many Gs for way too long of a period are subjected to the occupant. They die.

One step further:
It is quite possible that if these two vehicles were to have a head-on. The occupants would fare the same fate. The occupants of the larger mass vehicle succumb to the loads of the initial impact (Do some reading up on dynamic overshoot and the related. Good stuff.). While the occupants of the lower mass vehicle get knocked backward from the point of impact, but live.

- Shelby

WVOtoGO · #39 06-12-2009, 02:22 AM

Quote:

Originally Posted by Jim B.

It was this one, Shelby.

http://www.youtube.com/watch?v=k3ygYUYia9I

Yep. That’s the one !
Thanks, Jim

-S

aklim · #40 06-12-2009, 02:23 AM

Quote:

Originally Posted by WVOtoGO

Yes. You are correct.
But that’s not what automotive safety (in a crash) is all about.

Think about the two vehicles and the wall again:

The 3K lb vehicle hits a solid wall at 20 mph. It is a vehicle designed to absorb the impact. The front crushes. The engine ejects (thanks VW) out the bottom. Airbags deploy. Etc. etc. X number of G forces are experienced by the occupant for Y number of seconds as they decelerate to a stop. They live.

Same wall. Same speed. But now a 6K lb vehicle built solid as a rock (like those cars in the 50s/60s). This time, the deceleration rate is way too high. Very little kinetic energy is transmitted from, or absorbed by, the vehicle throughout the deceleration process. Way too many Gs for way too long of a period are subjected to the occupant. They die.

One step further:
It is quite possible that if these two vehicles were to have a head-on. The occupants would fare the same fate. The occupants of the larger mass vehicle succumb to the loads of the initial impact (Do some reading up on dynamic overshoot and the related. Good stuff.). While the occupants of the lower mass vehicle get knocked backward from the point of impact, but live.

- Shelby

Ah, I see what you are saying now. I was looking at it from a vector diagram POV, at least that is what I think you are saying. IF so, I think I understand your point. Thank you for the lesson, and I say this with all sincerity.

WVOtoGO · #41 06-12-2009, 02:31 AM

Quote:

Originally Posted by aklim

Ah, I see what you are saying now. I was looking at it from a vector diagram POV, at least that is what I think you are saying. IF so, I think I understand your point. Thank you for the lesson, and I say this with all sincerity.

Any time.

I used to teach this course: http://www.erau.edu/ec/courses/sfty435.html

I love a chance to dabble in it again. Thanks to you, as well.

Yep. I know. It’s airplane stuff.

But all the factors are pretty much the same.
(and one heck of a long list thereof)

Got to fly tomorrow am !!
PJ time for me.

Cheers all –

Shelby

Hatterasguy · #42 06-12-2009, 11:12 AM

The moral of the story is don't hit trucks.

The worst to hit would be a tri axle dump truck or cement truck. Very often tri axles are overloaded, and you can be sure 100k pounds will kill you instantly, even the most massive of SUV will offer you little protection. Cement trucks have poor brakes so do not stop quickly, and will flatten your Hummer like a soda can.

You want weight...I have seen loaded cement trucks will crush driveways and leave ruts, the road flex's under them.

Now that I have been riding in these things a bit, people are dumb to do what they do in front of them. Space people, give them space.

Mr.Kenny · #43 06-12-2009, 11:28 AM

Block walls? Of course the obvious choice is this.

http://www.youtube.com/watch?v=gnM58kHvLxc

tankdriver · #44 06-12-2009, 11:42 AM

Quote:

Originally Posted by WVOtoGO

Bingo. Now, we actually have a real winner.

Best line of the thread so far.

To think that one can judge the overall safety of a car from its mass...
Or from a photo...
Or from the results of a single accident you happen to know about...
Or who built it, for that matter...

is nuts.

- S

Quite.

Weight is a factor in safety but not the only one. There are some heavy cars built in the 70's that were not nearly as safe as some econoboxes of say the early 90's.

Quote:

Originally Posted by aklim

My C280 popped off the side airbag. I had a Semi Pubic Rami Fracture, Stable Sacral fracture and a little orange piss. The other girl had a few broken ribs, arms and spent a week in the hospital.

Different angles of impact can't really be compared, let alone comparing the bone density and strength of a hip bone to a rib bone.

Fulcrum525 · #45 06-12-2009, 12:26 PM

Quote:

Originally Posted by Mr.Kenny

Block walls? Of course the obvious choice is this.

http://www.youtube.com/watch?v=gnM58kHvLxc

Haha that is my favorite commercial of all time

Hatties right tough, don't screw around when it comes to trucks, any of them! Be it 100,000 lb dumpers or little uhauls. They are hard to see out of, heavy, and aren't exactly nimble or easy to stop.