Cadillac's approach to cutting weight out of its vehicles reminds me of the diet plan, Weight Watchers, which advocates a slow and methodical approach to weight loss unlike some other plans that look for bigger, more immediate results. I think Cadillac's commitment to cutting mass in the ATS by reexamining every facet of the design, down to the fastener level, can't help but be the more effective way to ensure a lighter, yet still highly stable and high performance vehicle. Chuck, obviously new material choices and close attention to customer requirements played key roles in its redesign effort, but what about use of CAE software? I'm assuming that FEA played a key role in the weight reduction redesign operation.
Beth: I didn't ask David Masch about CAE and FEA at the auto show, but I'm sure that played a big role. These days, it's almost unheard-of to do a structural design like this one without the aid of FEA. The beauty of FEA is that it enables engineers to manage stresses and strains in a way that allows them to optimize the cross-sectional area of members, and therefore optimize the weight.
Beth, here's an addendum to my earlier response: Cadillac's official press info says, "Advanced computational development helped determine the most efficient design." The press info also makes special note of the fact that a team of mathematicians was involved in the design.
Great article, Chuck. With all of the strong metals, I can't help but think one of the objectives is to protect the driver and passengers in the case of a collision. I know one of the fears involved in small-car purchases is the problem that comes when a small vehicle hits a giant SUV. Perhaps these metals answer that fear.
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.
Great point about computational analysis, which ties in with the recent crop of stories Beth Stackpole has done about CFD and FEA (computational fluid dynamics and finite element analysis) seeing broader usage. Of course, the automakers have long performed such analyses.
This story is a significant look at incremental engineering to achieve a goal. The "big" weight-reduction wins aren't there anymore, but there's still gas mileage savings to be achieved with every -- as you say -- gram you can shave off the weight of a car. Cadillac focused its engineering team on this task and achieved it. There's an important lesson here about the team engineering process which extends beyond the car. It applies to the entire auto industry, as well as to smaller-scale product design such as in medical miniaturization.
Chuck, thanks for a great article on an important topic. This is a good lesson about how to do lightweighting the right way. Although the headline of the article says that they cut mass one gram at a time, it's important to note that Cadillac has a well thought-out overall approach, rather than just blindling chunking mass out of components.
I've worked on projects where design groups working on each subsystem were each mandated to reduce weight by 10%. There was no "big picture" view. Designers frantically scrambled to take weight out of components wherever possible, reducing wall thicknesses, adding holes and pockets, etc. In many cases, this resulted in poor decisions, many of which had to be reversed later at significant cost.
In contrast, Cadillac started out with load path optimization. Then they built the vehicle around the optimized load path. This is a much smarter approach, which focuses around making sure that mass is utilized efficiently.
It's also noteworthy that Cadillac's lightweighting strategy made extensive use of steel. The idea that lightweighting always consists of replacing steel with aluminum is simply wrong. In some cases, steel is the best way to get the strength and stiffness you need with a minimum of material.
Another thing worth noting is that plastics and composites apparently were not a major part of this lightweighting effort. I'm sure that Cadillac probably looked at the possibility of using plastics or composites for some of these parts. It would be interesting to hear their reasons for staying away from these materials.
Your comments all seem to applaud Cadillac's design efforts. And, for the redesign points noted, they all may be justified. However, at 3400 pounds for a 'compact' SUV, that seems a little heavy for the mission of fuel efficiency for the next 5 years US standards. For all of the money spent for this redesign, it appears that the computational dynamics forgot to include the aerodynamics of the vehicle. And, when cars are so expensive, is there really that much usable space in this vehicle? In my 25+ years in commercial aviation, we always always had to consider the aerodynamic loads as the key to fuel efficiency. Apparently, Cadillac did not based on the shape of this vehicle, and it was not mentioned in the article or any of the comments I read. Engineering wisdom is based on past successes and failures. The Dodge Intrepid of 2000 has more space, one of the lowest coefficient of drag at 0.42, and a weight of only 3200 pounds with the highest level of torsional ridigity of any passenger car since then, and at a much lower price while easily achieving 28 to 32 MPG at 70 MPH.
Honda sells more cars than Cadillac. Maybe the reason for that success is that Honda started and still employs design engineers from the aviation industry. And, 'powdered metal connecting rods' - that is a recall just waiting to happen.
@windy9: As a rule of thumb, I've found that it's not a good idea to use powder metal in any application which sees significant tensile loads (like a connecting rod). That being said, powder forged connecting rods are widely used in the automotive industry. According to this article, more than 500 million powder forged connecting rods were produced between 1986 and 2005. So it's not exactly like this is something new which Cadillac came up with for the ATS.
The powder forging process produces a significantly denser part than conventional powder metallurgy (nearly 100% dense), so the mechanical properties are much closer to a wrought material.
As far as aerodynamics, you have a valid point, but I'm not sure that people who buy luxury cars necessarily want something that looks like a 2000 Dodge Intrepid.
Something said was, "you wouldn't want it to look like a 2000 Dodge Intrepid."
Well I would. I loved my Intrepid. My only fault with the car at the time was that I prefer rear wheel drive. (Which was considered for the intrepid.) A very roomy car that still performed well, had truly great brakes, and room for four large adults. Oh and a trunk with room for all their baggage. If I could buy a 2012 Intrepid with up to date systems and design improvements I would do so in a heartbeat.
BTW the only reason I don't still have the original 2001 Intrepid 3.5 RT was my wife was driving it and was t boned by a cell talking teenager totalling the car. Progressive improvements are a great way to improve the breed while giving a great value. Styling is a subjective thing, Benz and BMW could hardly be considered the kings of styling, but they continue to sell well. I hope Cadillac can produce a good compact luxury car, without such a high price that a few of us can afford it.
I must admit that I like the looks of the Dodge Intrepid much better than the current Cadillac styling. The windows are too small, and the longitudinal creases look "retro". Give me the fluid lines of the Intrepid any day!
I absolutely agree with the small windows. Is the main reason I will not get a new car because of the stupidity of the design. Has nothing to do with looks, but functionality. Understand small windows looks "racy","sexy" or "tough" or whatever, and every stylist does it.
Depth perception with stereo view is only good to about 20 feet. Beyond that is all based on visual cue. That means if all you can see is the grill of the car behind you, you have no clue how far it is. You need to see the car behind you, the tree, brush, signs and everything else relate to size of the car to judge distance. In traffic, you only have a second or less to do it. That means you need as BIG a window as possible on a car. Unfortunately, new cars make rear windows so small. Not only that, but windows get smaller the further back they go until they end in a sharp point. Hyundai even had the last window end in a triangle the size of a postcard. What a joke. From a functional point of view, that is ridiculous.
Went car shopping with my aunt over Christmas because she knows I am a car nut. Looked at Volvo. She liked it, but decided not to get it. She specifically mentioned the windows are too small to be comfortable. I agree. All the options on the car were great, but windows were too small. She instinctively knew small windows were not right. I wonder how many sales were turned away just because of that.
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.
There was some discussion in posts on the weight of the ATS projected, vs the weight of a 200 dodge interpid. Being a past owner of a 2000 Dodge interpid I would state if tat weight 3200 lbs it was due to serious fibbing by Dodge. mineweighted a lot closer to 3600 lbs. I have an ide of the weight because when I JUNKED it I drove it to the JUNKYADwere it was weighed for value.
Competitive vehicle weight to the ATS today...2012 Honda CRV 3300 to 3490 lbs depending on model. Toyota Rav 4 3300 lbs (appox). Bmw x3 2.5 (could be 2.8 BMW no longer tacks models to displacement...hanging around the old Detriot too much). 4112 lbs.
If Honda is hinring and employing a good number of aerospcae engineers, i would like to know from where. The Japanese Aerospace business is very small and people do not move much in the Japanese engineerring world do to the nature of employment. Hoonda itself is a renegade firm in that regaurd it is well know, and Honda is build ing a light jet, but it is Honda first light jet, and past smilar home grown products have been remarkable unsuccessfull.
I think it is time to parise Detroit for doing well. In the past they were darn good. Detroit did show engineering excellence for a very long time esp with keeping with the cost of the products. One can argue BMWs or MBZ prowess, however for the most part once you remove the marketing discussion...German cars cost 20 to 30 % more than equivalent American and Japanese makes.
The use of advaced CFD and CAD techniquies is NOT the same as using the latest version of say Unigraphics. There is a lot ot getting these packages to perform to thier highest potential and developing anaysis code to be integrated ocvver the std package it a good way to do this. Being critcal of a press release is a good idea. However a better way to analyze the SOA of a firm is to read the technical papers presented at the various conferances on the specific topics.
While I am a critic of detriot they have come a very long way up the content, value and quality ladder. I think it is time to evaluate fairly and not with the sweeping hand of ignorance based on times past.
The weight comments by Mike and Windy are salient points. I don't know about the hiring of aerospace engineers; cars are cars, and the different cost constraints of cars and planes impact the design process (as do weight requirements, which are there in cars but more serious in airframes). Anyway, the point I wanted to make is, I think the problem with the U.S. car industry is NOT that it hasn't upgraded its design and design-quality capabilities. (Build quality as improved too, but again I would argue that it's still not at Japanese standards, and Chrysler is not even at Ford and GM level.) So, as I started to say, the U.S. automakers problem isn't engineering capability, it's the U.S. carmakers don't employ a holistic design philisophy, which results in the best overall car, as opposed to best subsystems. It's possible that Honda and Toyota don't actually approach design holistically, that it's instead an emergent property of their processes. It's also possible that their tendencies toward staid designs are more amenable to well-design cars (i.e., change of pace is slower, allowing reliablity to be incrementally improved). Finally, it's possible that marketing and sales muck about in the design process more in the U.S. than in Japan. I'm being speculative here but I think i'm onto something.
Ok, I will agree with one of your points, and it may be the most important one that you made. The US car manufacturers apparently do not take that holiistic approach to vehicle design, and that leaves us as consumers having to select from a batch of vehicles where no one vehicle has 90 or even 80% of the latest basic functional design features - the major ones being energy efficiency, and usable space.
As to the Honda aerospace engineering comment, when Mr. Honda wanted to start his car company after the motorcycle business was doing well, the Japanese gov't would not allow him to hire many of the engineers he wanted from college and especially other auto companies. So, Mr. Honda hired aerospace engineers, the only ones he could get. That paradigm shift in quality and, of course areo efficiency was a very important reason for the high quality and very high energy efficiency.
Back to the Cadillac story. We did not, or I missed it, hear of the expected or tested fuel economy. And, did they also consider low rolling resistance tires, and did they eliminate the spare tire? After all, Cadillac owners do not change their own tires, do they?
Weight has always been a major consideration for me when buying cars (for both performance and fuel economy reasons) but somehow I am not impressed with Cadillac's effort.
Haven't checked recent models but the 2003 BMW 330i AND the 2003 Mazda Tribute SUV weighed almost 200 pounds less than this 'compact'. Are cars still gaining weight every year despite all the advances in materials and design?
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.
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.
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.
Comparing a sedan to BMW X3 is really not fair. X3 is a SUV. Should compare with the 3 series which is the gold standard for luxury compact car. Weight of the 3 series starts at 3,428 lbs. Loaded with options, it goes up to 3,800 lbs. So at 3,600 lbs the ATS is getting close, but can be better. They need to pay attention to handling too.
American cars traditionally paid no attention to weight and handling, but only ride comfort. My co-worker who is so conservative, he would never even travel outside the US bought only American cars. One time he got a BMW, and now he swear he would never touch American cars ever again. He was sold on the BMW 3 series's good handling. That is how important good handling is once people drive a good handling car. Weight and handling goes hand in hand. Handling can't be measured, is subjective. Handling has nothing to do with lateral g's. Is how the car feels in your hand. Do you feel connected to it.
GM has come a long way in handling department. I suspect there are still some old guards working that resist change. GM finally realize you have to have good handling cars. Is like fine wine or steak. Once you taste the best, you don't want to go back.
My hopes are high for the ATS. My first new car was a 1969 Mustang Mach1, then two Firebirds and my last american car was a 1984 Corvette but it was breaking down just seating in the garage. And those bad, scary recals to deal with. Since then, I had MB, Porsche and four BMWs that I found to be the best drivers cars to use them for everyday life.
Now, for the first time I am loking forward to compare the new ATS to the new 2012 BMW 3-series and hope, that ATS wins. I prefer american made for many reasons, mostly patriotic, but it must be at leat equal to BMW. I just wish that Cadillac would give the same 4-year free service like BMW does.
Another worry is the reliability issues, especially related to electronics. Can't repair them myself and little sensors cost hundrets of dollars when they fail, mostly right after warranty expires. Best electronics are Japanese - German's also like to fail sometimes, but ones you move to German cars is very difficult to go back to Japanese.
Hope, that new Cadillac ATS would change my buying trend by standing up to the best and perform like them as well.
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.
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 country’s 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.
If you’re an embedded systems engineer whose analog capabilities are getting a little bit rusty, then you’ll want to take note of an upcoming Design News Continuing Education Center class, “Analog Design for the Digital World,” running Monday, Nov. 17 through Friday, Nov. 21.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.