Cadillac will make its debut in the compact luxury market segment this year, thanks to a massive engineering effort that has resulted in a lightweight, high-strength body structure.
The structure makes liberal use of aluminum, magnesium, high-strength steel, and ultra-high-strength steel. It played a key role in bringing the new ATS sedan in at a curb weight 500 pounds lighter than that of its closest predecessor, the Cadillac CTS.
"We counted mass on all of our structural members in terms of grams," David Masch, vehicle chief engineer of Cadillac, told us. "We even ended up debating the size of fasteners."
The ATS body structure employs a combination of aluminum, magnesium,
high-strength steel, and ultra-high-strength steel.
(Source: Design News)
Cadillac's design effort called on teams of structural engineers, chassis engineers, materials specialists, and mathematicians to create a body structure that would manage loads intelligently. By positioning structural members to be in shear, rather than in bending, the designers made cross-sectional areas of virtually all members smaller. "Putting members in shear is the most efficient way to manage loads," Masch said. "The more you can get those structural members in line with the loads, the more efficient you can make them."
I definitely agree with that -- the design conservatism of Toyota (and for that matter, Honda too) -- and made a similar comment earlier in the thread. I also agree with Chuck about marketing mucking about too much in U.S. carmaking. Incremental improvements are the only way to both assess the effects of change incrementally improve reliability. Change all the subsystems at once and who knows what's going on. I also think that the U.S. car companies only started focusing on the build quality in their factories after Japanese and German automakers had come to the U.S. and set up factories which were more flexible, required fewer people, and built higher quality cars than they did or could.
I was thinking human safety as well while reading this. That weight savings goes towards fuel economy, yes, but in a crash there's conservation of momentum to consider as well. The weight savings means you're going to have more momentum transferred to this lighter car.
Smokey Yunik made a similar comment about reducing race car weight, a whole lot of years ago. " You don't take a hundred pounds out of a car in one place, you take an ounce out in sixteen hundred places."
Of course, one way to do that is to use the much stronger, much thinner steels. Unfortunately, when they finally do bend it is a much more destructive failure mode, and much less likely to be able to straighten. So there certainly is a tradeoff made there.
Ratsky: Excellent point about the conservatism of Toyota. That may also be the reason why Toyota thoroughly dominates Consumer Reports' reliability ratings year after year. Even after Toyota's supposed "unintended acceleration" problem a couple of years ago, Toyota's vehicles again came in with the highest marks on virtually all of their vehicles.
Re Japanese makers: all tend to be pretty conservaitive, but the most is Toyota. I was once told by a Toyota executive that they would not even consider adding any new technology until they were losing significant sales because they didn't have it! Nissan was a bit more adventurous, Honda much more so. Can't speak to the 2nd tier players (Mitsubishi, Suzuki, etc.), though.
Biggest difference: US manufacturers have been driven more by marketing, German more by engineering and function, Japanese by process (focus on quality).
One other point: largely because of their slow incremental approach to evolving thier products, the Japanese get away with 18-month design cycles, vs. 30-36 months for everyone else! Thus, when they DO decide to introduce something new, it appears quickly after the decision.
I enjoyed my 87 Cadillac deVille. It got gas mileage compareable to to the dodge stratus you mention and it wasn't that all heavy of a car. My 96 deville is rated, wikipedia, at 4,000 to 4,300 lbs and doesn't get a necessarily bad gas mileage. Some would probably say other wise, but I don't like little cars.
In the end the article says it's comparable in weight to most anything else on the market. So.. they didn't blindly reduce weight as they shouldn't if they don't want huge problems later on. But I am surprised Cadillac is even building a compact. Prior compacts like the Cimmaron did poorly. Why play that tune again? An aluminum hood? That's race car stuff from the 60's and you don't build mass produced bodies with aluminum. They dent too easy and too difficult to repair.
The question of whether engineers could have foreseen the shortcut maintenance procedures that led to the crash of American Airlines Flight 191 in 1979 will probably linger for as long as there is an engineering profession.
More than 35 years later, the post-mortem on one of the countryís worst engineering disasters appears to be simple. A contractor asked for a change in an original design. The change was approved by engineers, later resulting in a mammoth structural collapse that killed 114 people and injured 216 more.
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