LOS ANGELES - While the Plymouth Prowler's design is rooted in the past, the car is a preview of the future.
Chrysler Corp. is using the roadster to test new materials and manufacturing techniques.
The automaker eventually will use some of the innovations in higher-volume production vehicles.
Packed with aluminum, plastic and a little magnesium, the Prowler will help Chrysler reduce weight, costs and assembly time in future vehicles, the company said.
Chrysler, like other automakers, has been using aluminum in small quantities on various vehicles. But the Prowler represents Chrysler's first large-scale use of aluminum on a production vehicle, said Craig Love, executive engineer for the Prowler development team.
The 2,862-pound roadster has nearly 900 pounds of aluminum. Prowler has an aluminum frame, body panels and suspension parts. Different grades of aluminum are used, depending on the properties needed. The hood, deck lid, doors and hood side panels are stamped from aluminum 6022-T6, a high-strength alloy from Aluminum Company of America.
LIGHTER
Substituting aluminum and other materials for conventional steel makes the Prowler 21 percent lighter than it would have been if made of conventional steel, said Saad Abouzahr, materials executive for the Prowler team. The most important lesson Chrysler will learn with Prowler may be how to mass-produce aluminum cars, Abouzahr said.
'If we can take 25 percent of the weight out of tomorrow's cars and trucks, we can expect dramatic gains in performance and fuel efficiency,' Abouzahr said.
However, the automaker acknowledges that cost still is a significant barrier to aluminum. Pound for pound, aluminum is about four times as expensive as steel, the automaker said.
The Prowler's retail price is hefty: $39,000, including the destination charge.
Not only is Chrysler evaluating aluminum for the frame and body panels, the automaker is trying different methods of forming, joining and handling aluminum.
For instance, instead of spot welds, Prowler's aluminum panels are joined by rivet bonding and adhesives, Love said.
With rivet bonding, a shank of metal is driven into two sheets of aluminum, and epoxy adhesive is applied for extra hold, he said. By using self-piercing rivets in combination with adhesives, body stiffness is greatly enhanced, he said.
UNLIKELY PLACES
Aluminum can be found in unlikely places.
The rear brakes have cast-aluminum rotors, said Jon Rasbach, manager of Prowler powertrain and chassis design and development.
'We'll be the first on the market with aluminum rotors,' Rasbach predicted. Aluminum typically would not hold up on brake rotors, so Prowler uses silicon carbide ceramic particle to increase the stiffness of the aluminum rotor. The composite rear brake rotors take out about 15 pounds.
Prowler's aluminum suspension components - control arms, rocker arms and steering knuckles - are made using a special process called semisolid forging. The process reduces shrinkage of the aluminum and eliminates air that may be trapped in the components.
Most machining is eliminated because the components hold the shape of the molds almost perfectly. In this process, aluminum billets are heated until they reach the consistency of butter, Love said. The soft aluminum then is injected into a permanent die under high pressure.
Love said he believes this is the first use of the process in suspension components in North America.
MAGNESIUM
Chrysler also is experimenting with other materials. The instrument panel has a die-cast magnesium cross-car skeleton, not the traditional welded steel structure. There can be high scrap rates with a standard instrument panel because of heat distortion. But die-cast magnesium comes out the same almost every time.
The magnesium panel combines more than 20 stamping and plastic components into a single casting. It is eight or nine pounds lighter than a conventional instrument panel and is designed to bear the load of all the gauge parts.
Prowler's front and rear quarter panels, its motorcycle-type fenders and the rear valance panel above the bumper are made of sheet molding compound.
'It's used on Prowler to create elegant and flowing shapes,' Love said. The plastic composite also is used to surround the windshield, where it provides the strength of steel, but with less weight.
The Prowler has a new leather seat in which the foam padding is permanently bonded to the leather seat covers, eliminating the need for mechanical attachment devices, Love said.
Stainless steel replaces cast iron in the exhaust manifolds. The stainless steel can withstand higher exhaust temperatures, he said.
Prowler is equipped with a tire pressure warning alarm mounted on the instrument panel to warn the driver when the tires are too low, Love said. The vehicle also has run-flat tires, which allow a motorist to drive a vehicle up to 50 miles after getting a flat.
Straps made of Kevlar, the fiber used in brake pads and bullet-proof vests, are used on Prowler to help secure the body to the frame, Love said.
