11/15/1999 | 7 MINUTE READ

Body Shaping

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The Frankfurt International Motor Show, which is held every two years, is a key centerpiece for automotive developments. Here is a look at some of what rolled out in Germany this past September, with an emphasis on body materials...


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One of the most-impressive vehicles to roll out at the 1997 Frankfurt Motor Show was the Audi Al2. We were so taken with the vehicle that we put it on the cover of the November 1997 issue. The aluminum-intensive Al2 is a concept car. Often, concept cars don't get far beyond the show stage.

But Audi rolled out something more impressive in Frankfurt in '99: the A2 (above). It's the Al2 realized as a production model. It is an aluminum tour de force, with both an aluminum structure (the Audi Space Frame [ASF]) and aluminum body panels. It is arguably the only vehicle of its kind in the world.

Audi Al<SUB>2</SUB>

According to Audi calculations, the A2, which has a mass of 895 kg, is 40% lighter than it would be if it had a conventional steel structure.

One challenge faced by Audi was refining the ASF method that was first used in 1994 for the production A8 model. The A8 is a luxury sedan; annual production is on the order of 15,000 units. Certainly, that number is manageable from the standpoint of making a niche vehicle with what is still a niche material. Things are significantly different so far as the A2 goes.

The A2 is a compact car (overall length: 3,826 mm; wheelbase: 2,405 mm; height: 1,553 mm; width [excluding side mirrors]: 1,673 mm). Audi management anticipates the need to produce 60,000 or more per year, four times as many as the A8. That's a bigger niche, to be sure.

But Audi is seemingly dedicated to working with aluminum because it provides the mass reduction.

Why is Audi so weight-aware? Because it, like other European vehicle manufacturers, is trying to develop what's called the "three-liter" car: a vehicle that is capable of traveling 100 km on three liters of fuel. The diesel version of the A2 (a 1.4-liter, three-cylinder diesel with direct injection) does 100 km with 4.2 liters of fuel; the in-line, four-cylinder DOHC, spark-ignition engine requires 6.1 liters of unleaded premium to go 100 km. Closer, but not three liters.

The space frame is a combination of castings, extrusions and stamped panels. The ASF approach connects the extrusions with vacuum diecast nodes. The high-strength aluminum panels forming the body are integrated with the frame such that a rigid, self-supporting structure is formed. All of the aluminum for the A2 is sourced from Zurich-based Alusuisse (which may be combining with both France's Pechiney and North America's Alcan to form a huge aluminum supplier).

One of the refinements that was made to the ASF for the A2 as distinct from the earlier ASF for the A8 is significant part consolidation. For example, the roof rails, from the A- to C-pillars, are single hydroformed components. The cross section of the rail varies so that the load requirements can be handled without the weight penalties that would be associated with a uniform cross section (i.e., one that is sized to handle the largest load).

But all is not aluminum on the A2 body. As on the Al2, a retractable glass roof—which encompasses the area the entire width of the vehicle, back to the tailgate—is available as an option, replacing the standard ribbed aluminum panel that forms the A2 roof.

Audi Al<SUB>2</SUB>Will the open air smart City Cabrio bring more people into the dealers and save this plastic-bodied niche DaimlerChrysler brand?.

The body panels on the A2 that aren't aluminum are these: they're glass. It is called the "Open Sky" system, which is an option for the vehicle.

Get smart

So far as sales go, the vehicles from Micro Compact Car smart GmbH—the company that was originally a combination of the fashion sense and imagination of the company that produces Swatch watches and the vehicle engineering and manufacturing chops of what is now DaimlerChrysler (DCX)—have been anemic. Some people have argued that smart is, well, dumb. But the company, now fully owned by DCX, is driving forward.

smart will be launching the City-Cabrio model in March 2000. Its trick is that it has a fabric top and plastic rear window. The whole thing has a clever three-stage opening technique ((1) there is an electrically operated sunroof that retracts to the B-pillar; (2) an electrical release and manual actuation of the roof position it over the trunk lid, with an electric motor that then kicks in to keep the roof from vibrating in the breeze; (3) there is the ability to remove the longitudinal struts that connect the A- and B-pillars so that the top is completely open).

One of the notable aspects of the City-Cabrio (which is similar to the City-Coupe, with which it shares 75% of the same components) is that it is built with panels formed from GE Plastics' Xenoy PBT (polybutylene terephthalate) PC (polycarbonate) thermoplastic materials. One of the objectives of the plastic panel approach is to permit the switching of panels in a manner analogous to the way that people are able to switch their Swatch watches (with the difference being, of course, that smart is looking for people to change panels while Swatch wants people to change complete watches). It is supposed to be car as "fashion statement."

One of the apparent downsides for the smart has been a concern with safety such that not only is the fundamental metal frame of the vehicle characterized as a feature in the cars' promotional material (it is called the "tridon safety cell"), but the use of high-tensile steel tubes and panels in the A- and B-pillars, as well as reinforcements in the doors and rear side walls are noted characteristics.

City-Coupe and Roadster
No, there's nothing wrong with the printing of this photo: the paint on the City-Coupe is supposed to have a marbled finish. The people at MCC call the pigment application "cubic printing." Each vehicle that is so painted has its own unique result.
 Although the body panels of the smart Roadster are thermoplastic, that strong silver element is metal: part of the "tridon safety cell."

Perhaps because the quirky urban coupe didn't attain the anticipated buzz and acceptance since its launch at the Frankfurt show in 1997, in '99 the smart Roadster concept vehicle was introduced.

One of the slogans that is used as part of smart marketing is "reduce to the max." However, with the Roadster, less isn't more. More is more. Whereas the various permutations of the coupe are 2,500 mm long, 1,515 mm wide, 1,529 mm high, and have a wheelbase of 1,812 mm, the smart Roadster is a more conventional 3,223 mm long, 1,600 mm wide, 1,170 mm high and has a wheelbase of 2,270 mm.

Still, the body panels are plastic. What's more, a transparent plastic roof is deployed.

Although the smart Roadster uses the same 599-cc three-cylinder, 33-kW fuel-injected engine as the City-Coupe, it isn't limited to a top speed of 135 kph. The maximum speed of the concept hasn't been announced, but with a total mass of 700 kg, even a 599-cc engine should make it move.

Pininfarina Metrocubo
Note the Pininfarina Metrocubo's space-efficient sliding door. The body: thermoplastic. The frame: aluminum.

1.5-Box Design

Like the smart cars, the Metrocubo from Pininfarina S.p.A. is a small city car (overall length: 2.58 m). And it has a thermoplastic body structure. Like the Audi A2, the Metrocubo has an aluminum frame.

But this hybrid electric vehicle is a concept car.

A concept car with plenty of worked-out technical underpinnings, not just a one-off from the styling studio.

Interior flexibility is critical to a car with an overall length of 2.58 m).

Pininfarina worked with Michelin on tires; Lombardini Motori on the internal combustion engine; Siemens on the electric drive system; Exide for the batteries; Valeo for the lighting; BBS for alloy wheels; Webasto on the sunroof; Vickers Electrics on the generator; Isoclima Aerospace for glazings; and Technogel for seat paddings.

Metrocubo is all about energy efficiency and human utility. The former is based on such things as the hybrid drive-train and the recyclable aluminum frame. The latter is evident in the clever way that the seats (which bring to mind high-tech lawn furniture, based on both the tubular framing and the foldability) can be flexibly organized within the passenger compartment: only the driver's seat is in a fixed position.

smart vehicle

smart Factory Facts

The smart vehicles are built in Hambach, France, in a plant called "smartville." There are approximately 1,800 workers at the site, who work a 35-hour week. Of these 1,800 people, 1,100 are actually employed by what are called the "seven autonomous system partners." Said another way: there are seven suppliers who are responsible for building the modules that are fitted together to become the car. The vehicle manufacturer (i.e., MCC France SAS, which is 75% owned by DaimlerChrysler and 25% owned by a French state-owned firm) is responsible for system integration and process management.

The in-house manufacturing rate is less than 6%, which indicates how important the suppliers are to the production of the vehicle. The plant layout is cross-shaped, with suppliers feeding into the plant. There is a name for the production system, "smart-Plus." Final assembly requires just 4.5 hours. (How long it takes to learn the "smart" nomenclature is anyone's guess.)

Euro-style Conversion Cheat Sheet

Given that the information obtained for this story was in a land where the metric system reigns, we opted to use that system for the various dimensions. Although the auto industry is often described as a "global" industry, let's face it: Many—if not most—of us are more familiar with the English measures. So, by way of providing you with some of the conversion information that you might find to be handy to calculate wheelbases and whatnot. . .
•1 inch = 25.4 millimeters 
•1 mile = 1.61 kilometers 
•1 horsepower = 0.7457 kilowatts 
•1 U.S. gallon = 3.785 liters