Let the sun shine in: Chrysler joins the roadster rage with a convertible top-system jointly-developed with manufacturer Karmann

Automotive Industries, May, 2004 by John Peter

For those of you who complained about the lack of headroom in the Crossfire, Chrysler thinks that it may have solved that problem. This spring, Chrysler will add the Crossfire Roadster to the lineup. With roadsters making up 60 percent of the sales in a segment that includes Porsche Boxster and Audi TT, it was only natural that Crossfire should offer a topless version.

The roadster prototype made its public debut at the 2004 North American International Auto Show, instantly erasing any concerns that the boattail-designed coupe would lose too much character with the top cut off.

"When we did the roadster we wanted it to capture the spirit and the drama of the coupe," says Joe Dehner, director, Small/Premium/ Family Vehicle Design, "not only in rear view but in profile."

Designers tried to use elements of the coupe's boattail design while sculpting the shape of the top and the rear of the roadster while canting over as many components of the coupe as possible.

"It was a real design challenge to get all of these elements to work in the top down position," Dehner says.

The roadster was in development right along with the coupe.

"We put the coupe program together with the idea to do this," says Art Anderson, senior manager, Chrysler Crossfire and Vehicle Concept Development. But he admits that Chrysler engineers had not determined the exact design or configuration of the roadster by the time the coupe was finished.

"Given the set of factors in finding the optimum solution, we had to keep working to bring it together and it did take us a little more time." The top system was a joint development between Chrysler and Karmann, (the coupe and roadster are built at Karmann's Osnabruck, Germany, assembly plant). Anderson says that the pair went through 15 to 20 iterations to find the right roof system for the job.

"We had to work it out jointly," Anderson says, "because to make it functional and to meet all of the aesthetics and requirements, you have to do it one step at a time."

Anderson says that the development team did consider a retractable hard top but it didn't fit within the engineering criteria for the project.

"Some of these complex top systems take the whole back of the car and tip it off," Anderson says "and all the structure goes with it if it's not done exactly right."

Fitting the retractable hard top into the smaller space created by leaving the back end intact would have required the top to be bro ken into three to three and a half segments.

"By the time you create all of the links and mechanisms to do that," Anderson says, "it's a pretty formidable task. We really think we've found the right combination. It looks good, fits in the car nicely and still leaves some trunk room."

The top is constructed of Alcoa supplied aluminum castings that are painted black. The highly detailed castings are not only structural, creating a very stable top, (Chrysler has tested it at 150 mph) but also conceal all of the top's linkage so it isn't visible from inside the war with the top up.

The frame is built up and powder coated at Karmann's Rhiene facility in Germany. The premium cloth is manufactured by R&S (formerly Hartz), a major supplier of premium cloth tops for the U.S. and European markets. All of the components are then shipped to the Top Center at Karmann's Osnabruck facility where the material is cut and sewn together and installed to the frame.

The glass is then added, the Power-Packer hydraulics installed and the finished top is tested and validated at the Top Center before being sent to the main assembly line. Crossfire coupes and roadsters are assembled on the stone line. The top is packaged into the roadsters 6.5 cu.ft. trunk (7.5 cu.ft, in the coupe).

Before the top can be put down, a separator panel, that's accessed from the trunk, is pulled down and popped into place, to create a space for the folded top. A warning beep alerts the driver in the event that they haven't moved the panel into position.

With the top stowed trunk space is 3.5 cu. ft. Anderson says that golf clubs will fit in the trunk with the top down if you take the clubs out of the bag and put the bag in separately.

To operate the top, turn the release handle, mounted on the windshield header and pull it down. This releases the top fabric and automatically lowers the side glass. Lift the top approximately 8 in., press the button on the center console and the hard tonneau opens up. The soft top folds in and the hard tonneau closes. The operation takes 22 seconds, which will give you plenty of time to put the top up or down while stopped at a traffic light.

Several steps are taken to add stiffness to the body, steel tubes running the entire length of the A pillars are welded into a bracket mounted in the sill. A channel, built across the back, not only adds stiffness but serves as the attachment for the hard tonneau. The rear structure from the convertible top back has been retained.

"From a structural standpoint," says Anderson, "that still leaves a torsional rigidity of 7,300 ft. lb. per degree compared to the coupe at 15,000 ft. lb. per degree. And it gives us a natural frequency of 29 hz to the coupe at 50 hz."