[Jeroen]

Originally Posted by Lobogris

One element that can tilt the balance slightly in favour of thicker sheet metal is that the weight of cars with thicker sheet metal would be higher by a few hundred kilos. Take a look the short video below from US Insurance Institute for Highway Safety where you would see a Toyota Yaris fare poorly when colliding with a Camry. The experts made this conclusion: "all other things being equal, people in larger, heavier cars would fare better than people in smaller, lighter cars". Although the size may remain the same and thus would negate this theory a little, the added weight of thicker sheet metal is bound to help to some url]

Its been stated over and over and over again in this thread, its down to construction not weight. If you check earlier posts you will also find a video where, in a crash, a lighter car fares a lot better then the heavier one. Truth is, things are not equal, things are different by design and the design wins hands down from weight for regular road cars. There are all sort so expert opinions on the internet and I keep repeating not to believe to much you read on the internet. If you really want to understand why a better design outperforms some weight advantage you really need to dig into the basics of how car construction engineering works. Its mostly about finding ways to absorb the kinetic energy of the impact whilst having the lowest deceleration. The better you can do that the safer the car will be

Unfortunately this weight advantage is a real myth kept alive by poorly informed individuals who for some reason believe heavier is good. There are theoretical instances where heavy could have the edge, but we don't live in theoretical worlds, we live in a real world.

By and large, if safety is a buying criteria, you should look at all the safety features in a car, including crumple zones and preferably if available crash test data. Not weight. My wife little light Ford Fiesta is infinitely more safe then my heavy Mercedes W123, no contest.

Jeroen

[CrAzY dRiVeR]

Originally Posted by Jeroen

Its been stated over and over and over again in this thread, its down to construction not weight. If you check earlier posts you will also find a video where, in a crash, a lighter car fares a lot better then the heavier one. Truth is, things are not equal, things are different by design and the design wins hands down from weight for regular road cars. There are all sort so expert opinions on the internet and I keep repeating not to believe to much you read on the internet. If you really want to understand why a better design outperforms some weight advantage you really need to dig into the basics of how car construction engineering works. Its mostly about finding ways to absorb the kinetic energy of the impact whilst having the lowest deceleration. The better you can do that the safer the car will be

Unfortunately this weight advantage is a real myth kept alive by poorly informed individuals who for some reason believe heavier is good. There are theoretical instances where heavy could have the edge, but we don't live in theoretical worlds, we live in a real world.

By and large, if safety is a buying criteria, you should look at all the safety features in a car, including crumple zones and preferably if available crash test data. Not weight. My wife little light Ford Fiesta is infinitely more safe then my heavy Mercedes W123, no contest.

Jeroen

You did not get the point he was trying to convey. Crash tests are conducted to simulate a condition where a car crashes against an identical weight. For example, a five star rated S- class crashing against an identical weight. Or a five star rated 'smart' crashed against an identical weight. In such tests, weight doesn't matter and it's all down to construction.

But coming to the real world scenario of a crash involving an S class and a smart, both five star rated and having good construction, there is all probability of the S class being the best one to place your bet on? Why? Because the weight of the car means the force transferred to the Smart will be several fold that the Smart transferred to the S.

Infact - as seen in the test videos of such crash scenarios, the smaller car gets smashed and thrown around. Not something you see with the heavier car.

It might have been stated several times in this thread that weight doesn't matter for crash tests. Because in a crash tests a car is made to smash against an identical weight. Structure matters there, but that's not the case with a real life scenario involving two structurally identical cars.

As stated in the previous posts, let me emphasise - ALL THINGS REMAINING IDENTICAL, a heavier and longer car will have better probability of surviving a crash.

Comparing apples to apples- Your wife's Fiesta might be a lot safer than your W123, but it might have little odds of survival against a W212.

[Lobogris]

Originally Posted by Jeroen

Its been stated over and over and over again in this thread, its down to construction not weight. If you check earlier posts you will also find a video where, in a crash, a lighter car fares a lot better then the heavier one. Truth is, things are not equal, things are different by design and the design wins hands down from weight for regular road cars. There are all sort so expert opinions on the internet and I keep repeating not to believe to much you read on the internet. If you really want to understand why a better design outperforms some weight advantage you really need to dig into the basics of how car construction engineering works. Its mostly about finding ways to absorb the kinetic energy of the impact whilst having the lowest deceleration. The better you can do that the safer the car will be

Unfortunately this weight advantage is a real myth kept alive by poorly informed individuals who for some reason believe heavier is good. There are theoretical instances where heavy could have the edge, but we don't live in theoretical worlds, we live in a real world.

By and large, if safety is a buying criteria, you should look at all the safety features in a car, including crumple zones and preferably if available crash test data. Not weight. My wife little light Ford Fiesta is infinitely more safe then my heavy Mercedes W123, no contest.

Jeroen

Crazy Driver has explained it perfectly.

It is true that the design of the car is far more important then weight. However now-a-days all modern cars are well designed and get good crash test ratings. Now if we have two cars where one is made very light using thin sheet metal and the second one is heavier by a few hundred kilos due to thicker sheet metal and both have received an identical 4 or 5 star ratings- in this scenario, the heavier car might have an edge of say around 10 to 20% over the lighter one. Of course there are so many variables in design and construction as well as how the impact takes place and where each car is impacted. But all things being equal, the heavier car would have an edge against a similarly well constructed but lighter car. That is what the experts at US IIHS stated and that is the point I was making. We are not talking about comparing an old clunker from 30 years ago with a modern well designed car. We are talking about comparing two modern well made cars with one being heavier by 20% over the other.

[Lobogris]

Here is a clear statement on this matter from the US NHTSA (National Highway Transport Safety Association), the body that conducts US crash tests:

"Consider Weight
Crash data show that heavy vehicles offer more protection than light vehicles with the same safety equipment, particularly in two-vehicle crashes."

http://icsw.nhtsa.gov/safe_car_new/S...001/page2.html

Here is some additional input from CAR and Driver:

"Here's just one of many supporting examples from the Insurance Institute for Highway Safety: For 1994-97 four-doors, the driver death rate (expressed in deaths per million registered vehicle years) in the less-than-2500-pound class was 101; each 500-pound step up through the weight classes reduces the rate, first to 85, then to 73, then slightly less reduction to 75 for the 3500-to-3999-pound class."

"Weight softens impacts by forcing the other object to crush. This is the big-hammer effect. If you fall off the road, a heavy vehicle more readily deforms hedges and fences. And the big hammer is extremely important car to car. "In a head-on crash, for example, the heavier vehicle drives the lighter one backward, which decreases forces inside the heavy vehicle and increases forces in the lighter one," says IIHS. In other words, the lighter car crashes harder than the heavy one, even though they're both having the same crash."

http://www.caranddriver.com/columns/...t-crash-safety


This shows us that though weight by itself is not the only factor, it does remain at least a partial factor in improving crash safety. Of course it is possible to engineer a very light car and make it safe if we used special materials but for two similar vehicles with similar design and safety equipment, the one that is heavier by say 20% would have a slight edge.

[Jeroen]

Originally Posted by CrAzY dRiVeR

longer car will have better probability of surviving a crash.

Another dimension added to the myth. So our cars need to be heavier AND longer! (eh, no!)

Originally Posted by Lobogris

. However now-a-days all modern cars are well designed and get good crash test ratings.
.

Eh, no again. Still substantial variation in Crash test results across different manufacturers and or models. As I learned on this forum, Indian models might be less safe then their western counterparts

Originally Posted by Lobogris

.
the heavier car might have an edge of say around 10 to 20% over the lighter one.
.

10 to 20% of what?

Originally Posted by Lobogris

.
We are not talking about comparing an old clunker from 30 years QUOTE]

Webster definition for a clunker:

an old or badly working piece of machinery; especially: a dilapidated automobile ]

Remarkable that you can label my car, which sits in storage in the Netherlands and is valued at near concours condition? Are you aware of the passive safety features Mercedes built into this series?

As those whom might have read some of my other post are likely to recognize, I value the theoretical knowledge and analytical approach to just about anything. But unless you put all that knowledge to some practicual use, it remains a bit arbitrary what the value of such wealthy fountain of knowledge really brings to us, India and perhaps the world at large.

Advising everybody to start buying Mercedes S-class and add some concrete in the boot for good measure, might theoretically speaking, be the way to go.

For most of us its simply not practictal, other then the fact you would not see me dead in a S class to start with, but that is besides the point.

And that is my problem with those, oviously, very generic and theoretical statements about all things equal. In the real world they are not.

One can get some comfort I suppose/hope by looking at the crash test result of your car as a buying critiria. Do we seriously believe we need to add weight to that? You would really have to look into the sort of accidents that happen in India to be able to come up with an answer. I mean even without having access to statistical facts I'd say the changes of smacking into a Mercedes S in India are pretty remote!

Car safety, I think, needs to be seen within the context of the real world environment it which it needs to function/protect.

Jeroen

[Lobogris]

Originally Posted by Jeroen

Another dimension added to the myth. So our cars need to be heavier AND longer! (eh, no!)



Eh, no again. Still substantial variation in Crash test results across different manufacturers and or models. As I learned on this forum, Indian models might be less safe then their western counterparts



10 to 20% of what?



Webster definition for a clunker:



Remarkable that you can label my car, which sits in storage in the Netherlands and is valued at near concours condition? Are you aware of the passive safety features Mercedes built into this series?

As those whom might have read some of my other post are likely to recognize, I value the theoretical knowledge and analytical approach to just about anything. But unless you put all that knowledge to some practicual use, it remains a bit arbitrary what the value of such wealthy fountain of knowledge really brings to us, India and perhaps the world at large.

Advising everybody to start buying Mercedes S-class and add some concrete in the boot for good measure, might theoretically speaking, be the way to go.

For most of us its simply not practictal, other then the fact you would not see me dead in a S class to start with, but that is besides the point.

And that is my problem with those, oviously, very generic and theoretical statements about all things equal. In the real world they are not.

One can get some comfort I suppose/hope by looking at the crash test result of your car as a buying critiria. Do we seriously believe we need to add weight to that? You would really have to look into the sort of accidents that happen in India to be able to come up with an answer. I mean even without having access to statistical facts I'd say the changes of smacking into a Mercedes S in India are pretty remote!

Car safety, I think, needs to be seen within the context of the real world environment it which it needs to function/protect.

Jeroen

This is not a myth. US NHTSA itself stated (as quoted and linked above) that heavier and longer cars will fare better. Weight adds mass while the additional length adds extra crumple zone and slows down deceleration. It is immaterial whether the car is in India or Spain, the laws of physics don't change.

[Jeroen]

Originally Posted by Lobogris

This is not a myth. US NHTSA itself stated (as quoted and linked above) that heavier and longer cars will fare better. Weight adds mass while the additional length adds extra crumple zone and slows down deceleration.

Unfortunately, especially the bit about longer cars is a myth. It needs to be designed as such. Just because its long doesnt mean it has a crumple zone in the true sense of the word. By the way, my W123 has a true crumple zone as part of it being long. Very much by (German) design.



US NHTSA has a problem in the sense that they want to translate engineering and physics into one liners that look good in a simple article. Then those sort of generic statements make it to the internet and become myths. Safety is down to design and engineering, weight and the length of a car are just design paramters to take into consideration.



Here how the, in my case 32 year old clunker does in a crash test. all by design and engineering

https://youtube.com/watch?v=BCA-GuE0mUA

Jeroen

[su1978]

Have gone thru each and every thread very carefully. One of the theories of physics that comes to my mind is F=MxA(force= mass X accelration). Hence, compared to a car with lighter sheet metal, a car with heavier sheet metal travelling with same speed, is bound to gain greater inertia and hence the impact transferred to the cabin and passengers will be greater. So in my view, structural rigidity with lighter sheet metal would be a greater protection.

Please correct me if i am wrong.

[Jeroen]

Originally Posted by su1978

Have gone thru each and every thread very carefully. One of the theories of physics that comes to my mind is F=MxA(force= mass X accelration). Hence, compared to a car with lighter sheet metal, a car with heavier sheet metal travelling with same speed, is bound to gain greater inertia and hence the impact transferred to the cabin and passengers will be greater. So in my view, structural rigidity with lighter sheet metal would be a greater protection.

Please correct me if i am wrong.

You are correct that the total weight of the car has an impact on how you design the structural integrity, crumple zones etc. But I don't think you can just jump to the conclusion on how one would influence the other. They are definitely interrelated and some forum members might want to do a an everything remains equal type of analysis, but i wont go that way.
Jeroen

[Lobogris]

Without producing any evidence you are dismissing statements from reputed industry bodies like NHTSA, IIHS and Car and Driver as "myths". Here is a similar statement from EURO NCAP since you see to be alluding that Europeans know better:

"In frontal impacts between cars, the occupants of the heavier car or the one with higher structures tend to fare better than those travelling in lighter, lower cars."

http://www.euroncap.com/Content-Web-...-your-car.aspx

It is simple logic. If a car's bonnet is 2 feet long, then the crumple zone will be smaller than what a car with a 4 feet long bonnet can have. No one would debate that in a crash between a bus and a car, the car would come out better due to better engineering. Similarly, though to a lesser extent, the heavier and larger vehicle often survives a crash better as long as both vehicles are well designed.

[srishiva]

So basically a heavier car will use the other smaller car as its crumple zone

I remember reading in U.S magazine some years ago wherein the smaller cars (Fit etc) were much safer than some bigger cars. I agree that its all in the design of the car and not always we can generalize with "all things being equal".

[CrAzY dRiVeR]

Originally Posted by su1978

Have gone thru each and every thread very carefully. One of the theories of physics that comes to my mind is F=MxA(force= mass X accelration). Hence, compared to a car with lighter sheet metal, a car with heavier sheet metal travelling with same speed, is bound to gain greater inertia and hence the impact transferred to the cabin and passengers will be greater. So in my view, structural rigidity with lighter sheet metal would be a greater protection.

Please correct me if i am wrong.

Correct. Acceleration being a constant for such crash tests, force is proportional to mass.

So, for a heavy SUV to score a 5 star rating- it has to dissipate a lot more force with the help of its crumble zones as compared to a small hatchback. Remember, a crash test simulates a crash against an identical weight. So a 2 ton SUV has to crash against a 2 ton and still manage to protect its occupants for it to get a good star rating.

Hope that clear?

Now we take the same 5 star rated SUV and a 5 star rated hatchback on the road for a head on collision at the same speeds. The force experienced by the SUV will be a lot lesser than what it can handle while the hatch is subjected to more than it can take. If you see the test videos, the smaller car more often than not get thrown away towards the rear by the impact.

[Jeroen]

Originally Posted by Lobogris

This is not a myth. US NHTSA itself stated (as quoted and linked above) that heavier and longer cars will fare better. Weight adds mass while the additional length adds extra crumple zone and slows down deceleration. It is immaterial whether the car is in India or Spain, the laws of physics don't change.

Call it a generic statement, call it a myth, whatever you want. From an design and or engineering point of view it just to simplistic. Additional lenght doesnt add extra crumple zone. You need to design it to become extra crumple zone.

Here is a little exercise you could try. Correlate the nose lenght of the cars with their Safety rating. You will see a huge deviation around the mean, no mistake. There are short and long cars with very good, medium and still a few with poor ratings.

Again, these are very simple generic statements, that I for lack of a better word, call myths. They are used to try and create awareness for the masses and the internets of this world.

You want to feel adressed in that way, by all means please do. You will find yourself in excellent company or a least a lot of company. That doesn't mean it is a try representation of the topic at hand.

There are plenty of topics where I would go with the masses and the internets, but not this one. For one reason, see my earlier comments, you can't translate this statement to the real world and the Safety Ratings of cars confirm that, still widely different!

Jeroen

[sbr007]

After reading this entire thread, I can understand that many are misled about the safety of thicker sheet metal. As an Engineer myself, I will never agree to the fact that thicker sheet metal are safer than thinner sheet metal. Let me explain this with some basic physics:

1) The plasticity and brittleness of thicker sheet metal is higher than that of thinner sheet metal. So the impact instead of being compromised by elastic deformation is prolonged and oscillated for a longer time leading to even more destruction.

For example shoot a hard cork ball and a thin plastic ball with a gun. The bullet from the gun will make a straight hole in the plastic ball leaving the other areas intact. But the cork ball will blast into pieces. This is because plastic ball takes up the impact quickly and dissipates it to the surrounding in the form of waves but thicker cork ball which is brittle holds the impact within in itself and finally blasts after reaching the critical level of oscillations. So thinner sheet metal equipped cars escape quicker from destruction caused by sudden impacts.

2) The inertia of thicker sheet metal is higher than that of thinner sheet metal. So all parts of the thicker sheet metal equipped cars are bound to bear more shear stress and fatigue stress. Right from sudden acceleration to sudden breaking thicker sheet metal cars will have more body roll axle shear than thinner sheet metal equipped cars with the same suspension setup. More inertia and more body roll means more prone to accidents.

3) Thicker sheet metal easily takes up the impact from the crumple zones and crucial impact points because it is more fused and not tensile.

Adding to these safety glitches thicker sheet metal equipped cars are:

1) Low on fuel efficiency
2) Low on acceleration
3) Prone to brake fade
4) Prone to suspension failure
5) High on cost of manufacturing
6) Wear more faster
7) Have lesser power to weight ratio.
8) Low on agility

Finally the only advantage of thicker sheet metal equipped cars are

1) Gives good high speed stability
2) Takes up potholes better
3) Prevents body paint from leeching
4) Prevents damage from minor beatings.

Hope this makes a clear view about sheet metal thickness. Safety is directly dependent on airbags, ABS and few other electronic assistance system and most importantly our own driving style.

Rejecting a car and bashing manufacturers who do lot of research making the car more and more efficient day by day without compromising on comfort as well as safety, is plain ridiculous. Efficiency is more important than sheet metal thickness. Even saving a drop of petrol by following safe driving practices is significant than bragging "My car closes with a thud".

[Lobogris]

Originally Posted by Jeroen

Call it a generic statement, call it a myth, whatever you want. From an design and or engineering point of view it just to simplistic. Additional lenght doesnt add extra crumple zone. You need to design it to become extra crumple zone.

Here is a little exercise you could try. Correlate the nose lenght of the cars with their Safety rating. You will see a huge deviation around the mean, no mistake. There are short and long cars with very good, medium and still a few with poor ratings.

Again, these are very simple generic statements, that I for lack of a better word, call myths. They are used to try and create awareness for the masses and the internets of this world.

You want to feel adressed in that way, by all means please do. You will find yourself in excellent company or a least a lot of company. That doesn't mean it is a try representation of the topic at hand.

There are plenty of topics where I would go with the masses and the internets, but not this one. For one reason, see my earlier comments, you can't translate this statement to the real world and the Safety Ratings of cars confirm that, still widely different!

Jeroen

You keep disputing solid facts presented by reputed industry bodies like US National Highway Safety Administration, US Insurance Institute for Highway Safety, Euro NCAP and a well known car magazine, Car and Driver. You haven't presented any evidence or facts whatsoever to support your challenges. It is logical that a car with a 2 foot bonnet would be able to accommodate a smaller crumple zone than a car with a 4 foot bonnet. In the Toyota Yaris vs. Camry crash test, the passenger compartment of the Yaris disintegrated while the impact didn't even get close to crushing the Camry's passenger compartment due to its larger size and weight. No one can argue that a bike crashing against a car would fare better than a car. Similarly as long as both cars are well constructed- same crash ratings- the larger and heavier car will have an edge. This is not my personal theory- it is validated by scientific evidence from the top research bodies in the world. If you have any valid concrete evidence to the contrary, please present it.

Take a look at the video I posted again (available below for convenience). Review the crash between Toyota Yaris and Toyota Camry, both 5 star rated cars. Explain why the Yaris disintegrated? The only explanation, the one provided by Insurance Institute for Highway Safety, is that the higher weight and larger size of the Camry led to it performing better despite the fact that the Yaris also had a 5 star rating and is made by the same manufacturer.

http://www.youtube.com/watch?v=QXunnaaYtz0