The floor of Detroit's Cobo Hall was filled with myriad concepts during the recentNorth American International Auto Show. Of interest from a body perspective were a number of vehicles. Volvo's Safety Concept Car (SCC) has see-through A-pillars, an idea that may make its way into production on Volvo's 2004 Ford Focus-size S40/V40 replacement.Toyota's Matrix features body panels that combine sharp edges and soft curves in a single panel, thanks to "edge-web" panel forming technology. It will grow in importance as Toyota continues to chase the youth market. And DaimlerChrysler rolled out the latest iteration of its composite body technology in the guise of the Jeep Willys.
However, the most pervasive trend in body design/engineering is the reappearance of "suicide" doors, those rear-opening back doors last seen in volume production on the 1961-1963 Lincoln Continental and its successors. This door design came under legislative scrutiny in the late 1960s, and disappeared from the automotive scene soon thereafter. Only recently did extended cab pickup trucks and the Saturn SC bring this idea back from the dead.
Today, suicide doors are on concept vehicles everywhere. Unlike those found on the '61 Continental, however, most of the new designs eliminate the B-pillar. The reason for this change is to provide easy access to the interior. Whether used for improving access to the rear seats for adults, children, or adults with children in car seats; hauling large objects; or supporting the ubiquitous "active lifestyle" owner, the suicide door is the body style of choice for today's designer.
Proof of this statement can be found in one simple fact: Ten of the concepts shown in Detroit sported suicide doors. (Another, the Pontiac Vibe, was scheduled for introduction at the Chicago Auto Show.) Of those, only one–the Volvo SCC–did not dispense with the B-pillar. Yet all used upper and lower latches to tie the rear doors into the overall structure. One, the Mazda RX-8, is production-bound. Others–like the Honda Model X, GMC Terracross, and Nissan's massive Alpha-T pickup truck concept–are clear indicators that these companies are seriously considering this body style for production. Clearly, the suicide door is the body design trend.
Mazda takes a freestyle approach to re-inventing its flagship rotary-powered sports car.
|The RX-8's "freestyle door system" eschews the B-pillars and employs rear-hinged rear doors to create a capacious opening for easy access to the rear seats.|
"Our biggest challenge with this project was creating a four-door sports car that can seat four adults comfortably while maintaining the look and spirit of a true Mazda rotary engine sports car." So states Noboru Katabuchi, program manager of the Mazda RX-8. The RX-8 is officially a "design and engineering model," but the wink-wink, nudge-nudge comments by Mazda CEO Mark Fields indicate that the production model will offer few differences.
One of the key factors allowing this sports-car look is what Katabuchi calls the "freestyle door system," which is perhaps a better term than what might be otherwise be used: "suicide doors." There are rear-hinged doors but no B-pillars, which result in a huge side opening that provides an easy access to the rear seats not normally associated with sports cars. In other words, the excellent ingress/egress characteristics of the freestyle door system helped Katabuchi and his team meet their passenger comfort requirements while maintaining "a silhouette that unmistakably says sports car." In fact, when viewed from the side with the doors closed, one would be forgiven for thinking that there actually are B-pillars.
This is because Mazda has surrounded the small glass area on the rear doors with thick frames that are blacked out in the front, mimicking the non-existent pillars. The thick curve of the rear portion of the door frame fits almost seamlessly into the rear pillar giving the impression of one solid unit, and harkens back to the original RX-7. Each rear door swings out and away from the rear quarter panel on one massive hinge and latches with pins into the frame when closed. Given the sturdy construction of the freestyle doors, the RX-8 may have been structurally sound even without its B-pillars, but Mazda's engineers chose to provide an alternate source of body strength. They did this by giving the RX-8 a little backbone.
Mazda located a high-mount backbone frame on the upper part of the center tunnel which connects the front and rear bulkheads. The purposes are to improve both overall body rigidity and to improve the car's performance in front, offset and rear collisions. And the structural role the backbone plays as a part of the main frame has allowed Mazda to reduce the thickness of the body panels, achieving a 30 kg. weight reduction. The strategic use of structural foam also strengthens the body while keeping weight gain to a minimum. And to further enhance body rigidity, Mazda equipped the RX-8 with a closed section power plant frame–a design proven on both the Miata and the RX-7. (Incidentally, the RX-8 is powered by the new 250-hp RENESIS rotary engine which is so compact that the engine block is only 338-mm high, or about the same height as the transmission. In addition to the lower block height, the thickness of the oil pan on the RENESIS has been reduced to 40 mm, or half the height of the oil pan on the current RX-7. Taken together, these improvements allowed the RX-8 team to lower the engine, the one-piece, carbon composite propeller shaft and the rear differential by 40 mm. This lowers the car's center of gravity, which not only improves its dynamic performance, but creates space for the backbone frame without intruding into the passenger compartment. Compared to the RX-7's front mid-ship layout, the RX-8's engine is 60 mm closer to the center of the body resulting in a central mid-ship layout and a 50:50 front/rear weight distribution that enhances control and handling.) The central position of the engine also enlarges the crush zone between the engine and the front bumper reducing the deleterious effects of frontal and offset collisions.
According to Yoichi Sato, who led the RX-8 design team, the vehicle's overall styling reflects the compact layout of the engine. "We moved the front pillar more forward than usual and tilted it," he notes, "This design places most of the appearance of mass toward the back, resulting in a look that suggests that the car's center of gravity is in the rear." The front fenders help to balance the density of the rear by arching above the hood to create a sense of power. In keeping with Mazda's weight-reducing theme, the hood and fenders are made of aluminum and plastic respectively.–KEW
Now You See It…
|Volvo's Safety Concept Car (SCC).|
|Comparison of B-pillar blind spot between the SCC and a conventional vehicle.|
At a time when most automakers are shoehorning every new gimcrack gadget they can into their concept cars, leave it to the stolid Swedes at Volvo to get back to basics. Someone at Volvo, or Ford, the mother ship, determined that about 90% of information a driver needs to maneuver a vehicle safely comes by looking through the windows. So, it stood to reason: increase visibility and you decrease the chances that something bad will happen to the vehicle, driver, and passengers from an unseen object. Of course, this idea is not new. The designers of the Popemobile, that clear plastic box on wheels, figured it out years ago. What is new is the way Volvo and Ford went about improving visibility when designing their SCC.
Instead of reducing the car's support pillars to thin slivers and then using some exotic material to provide the necessary strength, Volvo made nice thick A-pillars with an open steel box construction and then covered it with transparent Plexiglas. The result is both protection and visibility. To eliminate the blind spot associated with the B-pillars, they were curved inward away from the side windows and integrated into the front seat frames.
One of the biggest challenges in developing a new automobile is translating the look and feel of an early concept sketch or clay model into mass-producible sheet metal. Toyota has taken a big step in bringing its stylists' visions closer to reality through recent advances in its metal stamping techniques. Working with a long-time Japanese supplier, Toyota developed proprietary methods that allow it to more precisely stamp sheet metal into complex shapes. The fruits of these labors can be seen in Toyota's newly introduced Matrix "Street-Performance Utility" vehicle. The core of the exterior design, which was penned by Craig Kember, a senior designer at Toyota's CALTY Design Studio in California, is a character line that runs across both door panels and rises to cut across the rear quarter panel and the gas cap. The sharp edge of this line falls into a soft contour along much of its length which Toyota likens to a web. Thus, Kevin Hunter, vice president of CALTY dubbed the body panel look "edge-web." And, since the Matrix will be marketed at the fashion conscious youth market, stamping improvements on the shop floor could translate into a competitive advantage on the showroom floor. The Matrix will be made at Toyota Motor Manufacturing, Canada, and will go on sale in early 2002.
If DaimlerChrysler's skunk works has its way, the one-word tip–plastics–that Benjamin Braddock received in "The Graduate" will carry the day.
The real story surrounding the Jeep Willys isn't what was said. It was what wasn't said that told the story. This isn't just another look at what a future Wrangler might look like, or an off-road toy for the wealthy. This concept is the brainchild of DaimlerChrysler's Liberty and Technical Affairs engineering group, and it is the latest iteration of the company's continuing look at composite body technology. Further, it is proof that DaimlerChrysler has not forgotten about this technology, and that it is serious about moving it out of the lab and into the assembly plant.
In 1994, Chrysler introduced the CCV, which originally stood for "China Concept Vehicle" before a name switch to "Composite Concept Vehicle". Instead of the multiple stamped and welded metal pieces necessary to make a traditional vehicle, the CCV molded the main body structure in left and right halves, both inner and outer, and bonded these pieces together. (The body structure, made of recyclable PET, was molded in color.) This unit was then bonded and bolted to a simple steel ladder frame.
|Frame-web technology encapsulates an aluminum frame within a bonded thermoplastic body structure, and moves DaimlerChrysler's composite body technology to the next level.|
The CCV cut estimated assembly time from approximately 19 hours to just 6.5, and required an assembly plant one-sixth the size used for more traditional vehicle assembly methods. Finally, the total weight of the plastic body structure was claimed to cost 20% to 50% less than a comparable steel structure.
When Chrysler debuted the ESX2 in 1998, a proof-of-concept for the joint government/industry Partnership for a New Generation of Vehicle program, it became readily apparent that this construction method had made the leap from the third world to the first. Much had changed, though the basic idea of bonding inner and outer halves together and attaching the resulting body structure to a frame remained intact.
Seventy-five pounds of aluminum was added between the inner and outer panels of the ESX2 to allow the structure to meet current and projected safety standards. This included the addition of an A-pillar post, B-pillar hoop, C-pillar post, door beams, and a collapsible front structure. Chrysler continued to tout the technology's light weight and thrift, as well as its ability to eliminate the paint shop. However, the problem of producing a Class A finish on the exterior body panels remained. This did not deter the Liberty and Technical Affairs engineers, and work on this technology continued.
The appearance of the Jeep Willys at this year's North American International Auto Show in Detroit proved the Liberty group believes molded-in-color composite panels have a life beyond their use in the production Jeep Wrangler's hard top. Strip away the 22-inch wheels and over-the-top styling, and you can begin to see where this technology might be headed.
At its base, the Willys use a simple aluminum frame with nodes at major intersections, much like the Audi A8. These are used to join the vertical and horizontal spans together. Large aluminum running boards, meanwhile, add to the structure's side impact resistance, a failing of the original CCV design, while keeping additional structure to a minimum.
The aluminum frame helps keep the weight of the Willys down to an estimated 2900 lb. In production, these square-section tubes could be replaced by a combination of extrusions, nodes and tubing, or a complete hydroformed structure in either aluminum or steel. In any case, the frame would be joined using a room-temperature glue that would eliminate the need for either welding equipment, or a curing oven.
The frame provides a stable base for the composite body, which is "webbed" around the frame. This means that body panels are molded in halves and bonded so that they encapsulate the aluminum structure. This eliminates the problems associated with trying to get a fiber-reinforced polymer structure to live through a lifetime of powertrain and suspension loads, while still using it as a stressed member.
|Inner tub or separate floor structure? Current betting says tub disbelievers are all wet.|
Also, the panels can be formed to include attachment points, cable runs, etc. into a single piece. This allows a level of modularity to be built into the construction process. Each door, therefore, could be molded on a just-in-time basis, sent to a production cell where the side beams, window and lock mechanisms, door pulls, speakers and the like are added, and sent to the main assembly line for mounting.
Front and rear quarter panels could be handled in the same manner. However, the current thinking splits the inner tub, comprising everything but the door panels and instrument panel outer, into two halves. Consideration also has been given to separating this unit just above the lower frame rails, and producing the floor in a single piece to which the other panels would be bonded. This would increase complexity and the part count, but would allow the use of a much smaller and less expensive molding machine. Reportedly, the inner tub concept holds sway.
One of the obstacles standing in the way of this technology is the continuing inability to produce cost-effective thermoplastic panels with a consistent Class A surface. For a vehicle like the Wrangler, this could be a disadvantage, as most buyers use this vehicle as everyday transportation, and expect a glossy surface. A limited-edition vehicle, however, could follow the lead of the Willys by using the matte finish to distinguish it from its lesser brethren. This would eliminate the need for a $350-million paint plant, cut costs, reduce pollution, but fall well below the 100,000 unit per year level this technology can support.–CAS