Sheet Metal Thickness - Does it matter?

[Leoshashi]

Originally Posted by shineshine

The "vault like feel, the assuring thud of the doors and good suspension behavior" are not just feel good factors.

Those who wants to have the "Best Power to Weight Ratio" and "fuel economy to beat a 'Prius'", may find these factors useless. But for those who wants to have a safer means of transport from A to B, this means a LOT!!!

And I could see a lot of people considering the NCAP ratings as the BENCHMARK of safety. What I believe is no such ratings can make a car safest. If so, why do they revise the safety targets every year..ever though about that?? Those environments under test are ABSOLUTELY PRE-DEFINED and accidents on road hardly resembles those testing environments.

Attaching a few pictures which would help you understand this. Wondering whether a 'Roll over rating' would actually help this? Do we really have a NCAP testing for these?? I strongly believe that a better 'Sheet Metal thickness' will help in these cases.

Please pardon my ignorance, but I would beg to disagree. Aren't the three cases involving 3 different scenarios where application of pressure is not the same?? I guess the following pics reflect an even playing ground where all the cars, be it japanese, american, korean or german are subjected to almost similar conditions and forces. All I can see is that the aftermath is same for all cars, irrespective of country of origin( which we eventually relate to sheet metal thickness).





I,as a visitor of this highly enlightening forum, have come to conclusion that sheet metal thickness is secondary, the chassis design takes the prime imortance when safety is concerned. Had it not been the case, Ambassador and Premier Padmini would have been the epitome of safety. I have personally been in an accident when my friend's Swift ZXi crashed head-on with an Amby and there were causalities in the Amby. I agree that our car was rendered useless and crumpled like an amoeba, and the amby was still very much in shape, but thanks to modern engineering and seatbelts, we came out unscratched!!
Like someone aptly said in this thread, Outside body panels are like skin, and the chassis is like our skeleton. Thinner sheet metals might take bruises easily, but a car can be safe if structural design is sound enough.

Having said that, hearing that reassuring thud surely gives a peace of mind. But still, I will prefer to be in an over-engineered car(even with a thinner sheet metal) than being in a Hump of Metal in case of an accident. Now please don't misunderstand me- I am not refering to the germans here. They surely make great cars, with some clever engineering. All I mean is-even if the germans start coming with wafer thin sheet metals, I will choose them if their chassis design is safe.
Hence for me, Sheet metal thickness takes a secondary importance, with prime importance given to chassis design.


Just my 2 cents....\

Regards,
Shashi

[kiku007]

It's a big deal for me.
Every once in a while when I close the boot door of a swift Dzire taxi, I almost freak out. With a Ford being my daily ride, I cannot believe how light that damn boot door is. Maruti may very well have made it in plastic instead.
And of course the lighter cars don't seem to hold up well in bad road conditions after some years. They are rattle snakes.

[vinodbollini]

Originally Posted by 100kmph

No car would sustain if a tree falls on it.

http://www.topgear.com/uk/videos/a-t...s-18-episode-5
No Europe vs Rest in this video, but there's a couple of good examples.
"Lancia Engineers said the results were perfect... SAAB engineers... not good at all"
"... pillars were so strong they did not _need_ roll bars ..."

I do think the "Europeans" and the "Asians" could be from different worlds: I believe it is a philosophy issue somewhere, and the Europeans IMHO push the envelope more often.
I think on an average the European asks and answers the question: How can we make this better - effectiveness, safer, stronger, faster? And the Asian asks in the same place, how can we make this more efficient - money, time, scale?
Neither approach is complete solution.

I believe in a weird sort of way, that boils down to how the people who buy and use these cars in the end.

On a more directly related note, I have the following points:
1. The Ciaz is an extreme example, since the metallurgy and weight reduction was very deliberate. Without that the i20 Elite (also Asian) weighs more! I don't think the crux of the build choices that define European-ness or Asian-ness is "sheet metal thickness". It's how and where they put the metal, to a much greater extent.
2. The MQB and other similar efforts are looking at weight reduction from the chassis and then onto the rest of the car; and the reductions are significant without compromising on the other goals - the Polo is based on the same platform as the A1, weights about 7-8% less than the previous gen. and has a 5 star NCAP on the Euro-spec. So weight reduction is not directly in conflict with safety; and is a far more complex than metal thickness in the body panels - so you cannot ever compare apples and oranges.
3. In my investigation into buying a car, I found that the Polo HL is cheaper than the top end of Swift, i20 Elite, Etios Liva, Punto Evo by a significant amount. This was both when I was looking for a car in the family 5 months ago, and as recently as last week. All of this is OTR comparison. Am I missing something here? Everybody seems to think that German car is expensive. And also seem to be surprised that a "better built" car is cheaper. It sounds too dramatic to be true.

[blacksport]

We have had numerous such arguments in the past, and wonder how this thread escaped the axe of the mods until now. Perhaps the weekend. So before this thread gets deleted or closed let me...

It is a big deal to me. Not because I believe that sheet metal thickness equals safety. But because, I believe, what is visible in the exterior is testimonial to what could be available inside. A car with "adequate" sheet metal thickness would give us only "adequate" of everything. And that includes the structure as well. I would any day pick a thick skinned car than take my chances with a thin skinned one.

Secondly, I do not believe in the philosophy of lighter equals better. I might accept that philosophy for a smartphone, but in cars, I think heavier is more desirable. I would love cars that don't freak me out at 100kmph.

At the end of the day, we are all free to choose what we want. I love handling, performance and safety. But that doesn't mean somebody shouldn't choose to want fuel efficiency over the above virtues. But I just wouldn't like it when somebody tries to justify his choice by arguing that other people's choices are no big deal.

[nakul0888]

Originally Posted by blacksport

Secondly, I do not believe in the philosophy of lighter equals better. I might accept that philosophy for a smartphone, but in cars, I think heavier is more desirable. I would love cars that don't freak me out at 100kmph.

At the end of the day, we are all free to choose what we want. I love handling, performance and safety. But that doesn't mean somebody shouldn't choose to want fuel efficiency over the above virtues. But I just wouldn't like it when somebody tries to justify his choice by arguing that other people's choices are no big deal.

If you think heavier cars are better than lighter ones, you are sadly mistaken blacksport.
I am also surprised to see that you have failed to spot the trend in the international market nowadays.

All the VAG group cars are moving to the lighter MQB platform, The range rover has shed 400 kilos of weight, The new bmw m cars are focussing more and more on lightness, the alfa romeo 4c weighs just 800 kilos. The examples just go on and on.

Many of the people here have an opinion that lightweight cars are only good for better FE and nothing else and heavier cars like the punto and the polo are the ones that are better to drive. You all couldn't be more wrong.

Weight is a negative trait in any good car. Remove the weight and everything improves not just FE, but performance, emissions, handling, ride quality, quite literally the whole car will become better.

Manufacturers should be and most of them are including VAG group are trying to build cars that are lighter yet just as safe or even safer than before.

[Jeroen]

Originally Posted by nakul0888

If you think heavier cars are better than lighter ones, you are sadly mistaken blacksport.

Fully agree. Its down to design, construction and materials used.

Here's an interesting movie comparing old versus a new car, but also actually heavy against light:

http://www.streetfire.net/video/5th-...?__federated=1

[blacksport]

Originally Posted by nakul0888

All the VAG group cars are moving to the lighter MQB platform, The range rover has shed 400 kilos of weight, The new bmw m cars are focussing more and more on lightness, the alfa romeo 4c weighs just 800 kilos. The examples just go on and on.

But then you should also be able to explain why the newer Marutis/Hyundais/Toyotas are heavier than the earlier versions. Also why Swift does not use the thinner sheet metal they use in the Alto/Wagon R. Does cars currently available here use the same material as the Alfa Romeo 4C? Here, sheet metal material remaining the same, the only variable is the thickness.

[saket77]

In my opinion, the thinner sheet metal are bad for minor fender bender incidents, but with good monocoque/ structure and with all safety kit in place, it is just as safe. If the thread is more about 'safety' (as the title does not talks specifically about safety), then I will choose a car based on the structure rating and one with safety kit in place rather than just knocking on the sheet metal and finding it thicker. Also, I am not sure if a thicker sheet will be of any use over thinner ones in major crashes.

One more thing that I would like to ask - Is it that the Asian Honda City that was tested, which outscored the VW Vento, had sheets thicker than even the Vento? Was it more robust in terms of outer metals sheets used? If not, then we can be assured that the monocoque of the City is safer than that of VW Polo/Vento. Also, not to be missed is a point that the Honda City scored the maximum ever score by any car tested by ASEAN NCAP. I know of another Japanese car which has outscored many other cars in the International crash tests and that is the SX4.

[nakul0888]

Originally Posted by blacksport

But then you should also be able to explain why the newer Marutis/Hyundais/Toyotas are heavier than the earlier versions. Also why Swift does not use the thinner sheet metal they use in the Alto/Wagon R. Does cars currently available here use the same material as the Alfa Romeo 4C? Here, sheet metal material remaining the same, the only variable is the thickness.

Do you honestly believe that Toyota/honda/suzuki cars don't have the driving dynamics of say a FIAT/VW because of it's lighter build?

The fact is straight line stability, handling, ride quality of a car depends on mostly on its suspension setup and tuning. Not just thick sheet metal.

If Honda/Toyota wanted to build an outright driver's car they can easily match or even better the Europeans with exactly the current type of build that we are seeing now.

IMHO they don't make driver's cars because they are here to make profit. And hence choose just about adequate & cheaper setup for their cars. This results in the shabbier dynamics. But most people won't give a damn and will buy their cars anyway. Only enthusiasts will complain. There is no use in catering to the demand of enthusiasts because there is simply not many of us in the market. So there is no need to waste money here.

[blacksport]

Originally Posted by nakul0888

Do you honestly believe that Toyota and honda cars don't have the driving dynamics of say a FIAT/VW because of it's lighter build?

Yes, I do believe, and have experienced that.

The fact is straight line stability, handling, ride quality of a car depends on mostly on its suspension setup and tuning. Not just thick sheet metal.

I'll rephrase. Stability is dependent on many factors, one of which is weight.

If Honda/Toyota wanted to build an outright driver's car they can easily match or even better the Europeans with exactly the current type of build that we are seeing now.

Different manufacturers make cars that go well with their target audience. VAGs primary customers are those who love driving. If they make Maruti like cars they would be put out of business in Germany.

IMHO they don't make driver's cars because they are here to make profit. And hence choose just about adequate & cheaper setup for their cars. This results in the shabbier dynamics. But most people won't give a damn and will buy their cars anyway. Only enthusiasts will complain. There is no use in catering to the demand of enthusiasts because there is simply not many of us in the market. So there is no need to waste money here.

I am graying, and officially in the middle-age category. My thirst for drivers cars haven't dried up yet. But a few more years down the line, I would be shopping for boring but reliable, fuel efficient cars. We are lucky that we get both kinds of cars here, so each of us can select whatever kind of cars we like.

[saket77]

Dear Blacksport,

Not pin-pointing your post, just trying to clear some misconceptions or you may say, forwarding my opinion on some general points that most people think about.

Originally Posted by blacksport

I'll rephrase. Stability is dependent on many factors, one of which is weight.

Not totally true in practical conditions. A heavier car may give you a more planted feel in a straight line drive at high speeds, but higher inertia that will come inherently will not be beneficial when it comes to handling or nimbleness.
Lighter cars handle much better than heavier cars, catirus paribus.

Originally Posted by blacksport

Different manufacturers make cars that go well with their target audience. VAGs primary customers are those who love driving. If they make Maruti like cars they would be put out of business in Germany.

Exactly. If VW behaves like Maruti in Germany, they will be wiped there. Similarly, if Maruti Behaves like VW here in India, they too will be wiped off.

Originally Posted by blacksport

I am graying, and officially in the middle-age category. My thirst for drivers cars haven't dried up yet. But a few more years down the line, I would be shopping for boring but reliable, fuel efficient cars. We are lucky that we get both kinds of cars here, so each of us can select whatever kind of cars we like.

I don't think that the thirst will be dried ever. I drive an older car, you may say a previous generation car, but that every time I drive it, it manages to bring a smile on my face. Compared to many newer cars of friends and family, I would still rate my car higher in performance, handling and driving pleasure. And its a Maruti Suzuki. So, that is reliable, fuel efficient and something that it is definitely NOT is boring.

So, its not that a reliable, fuel efficient car needs to be boring. Just that the makers are finding it more profitable to cater the mass markets; and that what brings them money rather than enthusiasts.

[Valkyrie]

Sheet Metal thickness, although is a parameter, to increase strength, is not the only criteria.

Various steel used in cars have different properties. For example, a skin panel should have a dent resisting properties. While inner or structural steel should have high yield strength.

One way to increase strength is use of higher grade (read thickness) steels. While this is a cost effective solution. But many companies resort to use of high strength steels like TRIP, Dual Phase, Martensite Steel etc, which for the same thickness has thrice or more the yield strength.

But they are costly.

Hence cheap cars just about suffice regulatory norms of crash and other performance requirements. While costlier cars perform better in crash.

A light car can be designed to be much better than a heavier car. You just have to play with material properties, like section inertia, stiffness, strength etc.

The Pillar reinforcements of Polo are made of hot stamped steel, which is very innovative and was previously unheard of in India.

Most of the older cars in India, like the old 800 or Omni, or even gypsy didnt had sufficient reinforcements, so that they would not clear the proposed crash norms.

In India only full frontal is a regulation, while in developed markets, offset frontal, small overlap front crash, side crash, pole crash etc are regulatory requirements.

So in the end, No. Thicker steel doesnt imply stronger cars.

Stronger cars are better designed. They have a much better way of dissipating/absorbing the crash energy, more ways to channel them out of the passenger compartment. Its all in the beauty of the BIW (Body in White) design.

Hope this helps.

[diffsoft]

Originally Posted by Jeroen

Fully agree. Its down to design, construction and materials used.

Here's an interesting movie comparing old versus a new car, but also actually heavy against light:

http://www.streetfire.net/video/5th-...?__federated=1

Whoa! That was an eye-opener. I wonder what the results would have been had the pitted a Korean / Japanese equivalent of the Modus!

Cheers,

[CrAzY dRiVeR]

Originally Posted by nakul0888

I am also surprised to see that you have failed to spot the trend in the international market nowadays.

Surprised you have deeply mis-understood the trend in the international market. Cars are not just getting lighter, they are getting stronger and more rigid by the use of alternate materials which are lighter as well. Aluminium, carbon fibre etc to name a few to replace the age old iron and steel in the manufacturing process.

Can we say the same about the lighter cars in the Indian market?

Originally Posted by nakul0888

All the VAG group cars are moving to the lighter MQB platform

MQB platform uses aluminium along with steel to reduce weight, be it chasis or engines. The higher costs arising out of this is cancelled off by the fact the the architecture is modular and the company does not need to invest heavily on the research and development of each product off the platform, across brands.

Originally Posted by nakul0888

The range rover has shed 400 kilos of weight

Nice that you had to bring it up! Yes, a good example of weight saving. The new Ranger Rover uses an all aluminium chasis coupled with body panels made of alumium, boron steel and magnesium cross members to increase torsional rigidity.

Originally Posted by nakul0888

The new bmw m cars are focussing more and more on lightness

By using Carbon Fibre for the roof panels, aluminium for the body panels and bonnet and even experimenting with thermoplastic these days.

Originally Posted by nakul0888

The alfa romeo 4c weighs just 800 kilos. The examples just go on and on.

With extensive use of carbon fibre, one of the rare cars to have almost the entire chasis made of CFRP. The weight is 895kgs dry and the entire chasis that is carbon fibre weighs only 55kgs. But is still super strong and rigid for a sports car thanks to the special qualities of carbon fibre.


The point is - International cars are not getting lighter, they are getting smarter.

• Smarter use of materials to ensure no compromises are being made in the pursuit of lightness and efficienc.
• Smarter use of manufacturing processes to offset the costs of using advanced materials of construction. (For example - modular cars is a manufacturing process more than a chasis itself that we fondly refer to as MQB).
• Smarter engines to make sure the smaller displacement is not an issue. Turbopetrols, hybrid etc.

Originally Posted by Jeroen

Fully agree. Its down to design, construction and materials used.

+ 10.

Fully agree with you, even though I am in disagreement with the context in which you stated the above point.

Lets take the Indian context -

• The marketing papers for Ciaz says it used high strength steel as a weight reducing technology - fair enough. But somehow thats at odds with the pricing at which the car is expected to debut at. We know another car which used high strength boron steel and ended up quite overpriced for the market, in the same segment.
  
• Ever wondered how the DZire managed to acheive the same weight as the hatchback - just open the boot and have a look at that sheet metal. I have one in the extended family and had the pleasure to examine this few weeks back - the sheet is about as thick as a Rs. 2 coin. A picture in my Xcent ownership thread shows how a Rs.5 coin feels thicker in front of that metal. Can anyone point out the clever engineering here? With a small stubby boot for protection with such sheet metal - can anyone explain the relevance of NCAP ratings incase of a rear end collision. Its just cost cutting at work.
  
• Fellow BHP'ian had proved (with images) on another thread on the differences between the front bumper on the international and indian versions of the Swift. Check here. Thats what passes for weight and cost reduction in the Indian market.
  
• Honda City has a big weight disadvantage in the Indian market compared to the crash tested Thai version. Lets forget that for now since I have already explained it earlier, and look at the 1.5 DTec engine that used aluminium for its lightweight credentials - making the NVH levels rather unfit for a Honda. What was the clever engineering done to mask it? Pass it on to the customer and when lot of complaints (from Amaze owners) ensued, add more insulation material on the City.
  
• More than 300 changes were required in the Indian made Ford Ecosport to make it survive the crash tests for the european market.

Lets get it straight - All these cars discussed here are being made on a big budget here in India. A City/ Ciaz/ Etios that has almost the same dimensions as a Civic not so long ago cannot be ultra light weight and be more rigid at the same time without using some higher grade materials, which the accountants wont approve of! So, there's obviously more to this weight reduction that meets the eye. As long as the Indian market doesn't make crash tests and measure safety standards of cars with strict guidelines, we shouldn't be expecting them to deliver them either, unless the cars are made just as they are made for the international markets.


Suggest we dont conclude on this - My 'made for India' Asian/ European car car is just as safe as the international car discussion just yet - till we have conclusive data from the Indian market (be it crash tests or proper study about weight saving measures used).

Till then - those who 'feel' good with their heavily built cars can continue to do so, while sacrificing a bit of perfomance and economy. Others who have lighter cars, but just NOT 'made for India' extra light - can enjoy their superior machines with more power, performance and mileage while knowing they are just as safe.

[zenren]

Originally Posted by diffsoft

Whoa! That was an eye-opener. I wonder what the results would have been had the pitted a Korean / Japanese equivalent of the Modus!

Cheers,

We are unlikely to see anything that would be nearly as safe as Modus in India in the hatchback segment. Pit that old Volvo against an Alto or Eon and we would have concluded the exact opposite - just having new safety features like airbags are not sufficient if the structural integrity is not accounted for in the design stage.

However, an older car with thick sheet metal doors is still probably less safe than a car with thinner sheet metal and properly designed side impact beams.

There are 2 things in the current discussion that needs to be separated out -

1. weight reduction due to usage of modern high tensile steel or a better design which might actually result in higher costs
2. weight reduction due to reduction in the quantity of steel used as a way of reducing the costs.

#1 is happening in Europe/US and #2 is happening in India for most part. Lets not confuse between the two. Reduction in steel can be achieved by reducing the thickness of sheet metal or by doing away with some of the cross members that are "redundant" to the frame except for the crash worthiness aspect.