In 2002, Volvo executives tasked their designers to come up with a replacement for the venerable C70, which, over its six years in production, sold 50,000 units, a respectable number for a convertible. The team was told to push the envelope and a competition was generated between Volvo’s design studios in California and Sweden. When all was said and done, the design presented by the California team was given the green light. But that was just the beginning of a journey that would require Volvo to set out on uncharted territory, since the design called for the development of a hardtop convertible providing room for up to four passengers, while maintaining the compact dimensions of the existing P1 platform (shared with the S40, V50, upcoming C30, European Ford Focus, Mazda3 and Mazda5), and of having room for cargo in the trunk, even when the top is down. These requirements called for out-of-the-box thinking. After sifting through three different hardtop design proposals from various suppliers, Volvo settled on a three-panel hardtop solution designed by Open Air Systems GmbH (OASYS), a wholly owned subsidiary of Webasto AG (http://www.webasto.com). “We chose OASYS because they had the most up-to-date technology and their solution was the best one to fit all of our requirements,” says Olle Odsell, technical director for the C70 project. It also didn’t hurt that OASYS was partially owned at the time by Pininfarina SpA, which did a majority of the engineering work on the C70 project. What’s more, Pininfarina is also involved in producing the C70: the car is built at a plant-within-a-plant at Volvo’s Uddevalla, Sweden, factory, a 60:40 joint venture with Pininfarina.
The hardtop and trunklid system, which consist of more than 700 parts, is manufactured alongside the C70 final line. The roof panels are placed on the body-in-white before the paint process begins. Once painting is complete, the panels are removed and sent to the separate roof assembly line. The body proceeds on a separate track through the final assembly shop and the two systems get reacquainted in the middle of the final assembly hall.
Assembling the top system may have been the least challenging step, whereas making sure the system was reliable and could operate seamlessly in a myriad of situations was the most complex process of them all, according to Odsell. “The obvious challenges were water tightness, noise resonance and fixing the trunklid on the roof while the top is down. The heavy roof [the system weighs 198 lbs.] has its own resonant frequency and we had to pass that, along with making sure that mass is secured in the trunk; we had to put a lot of effort into making sure those three pieces were secured and stable,” he says. “We tested the vehicle extensively on gravel roads and parked it with one wheel on a curb, to make sure the roof locked secure in the trunk and didn’t create any noise issues.” To achieve the requirement of storage in the trunk with the top down, OASYS devised a unique loading sequence. The top’s computer system moves the entire folded roof up 7.9 in. when the trunklid is open, for added ease in loading and unloading luggage or other items (a divider prevents overloading the available space). Added attention was paid to kinematics, specifically assuring the top operates in a seamless, smooth motion throughout the opening and closing sequences, actuated by a pushbutton. Engineers opted for a single electric motor, hydraulic pump and computer module to operate the roof, with several hydraulic linkages: “The kinematics on this type of hardtop were very tricky. Some of the other proposals from other suppliers didn’t operate as smoothly and were not very efficient for packaging. What made the difference was how we stacked the system, with the largest piece ending up on top,” Odsell says. During operation, which takes all of 30 seconds, the latches on the windscreen unlock electronically, while the sides of the fabric headliner butterfly into the center of the panels. The rear portion of the roof ends up on top, while the front slides neatly above the middle section. One thing that seemed to cause a bit of concern was the use of Kevlar rope to deploy the headliner butterfly portion of the operation. Odsell says Volvo engineers made sure the rope was “very durable” and additional attention will be paid to those particular parts of the system when the vehicle returns to dealerships for routine maintenance. To assure durability, the roof system has already gone through a 20,000-cycle test, which should be the average usage during the normal vehicle life.
The C70 will be the first three-panel hardtop to hit the market, although several competitors are nipping at Volvo’s heels when it comes to capturing a piece of the four-seat hardtop niche. Volkswagen will introduce its Jetta/Golf-based Eos hardtop convertible later this year, while General Motors Corp.’s European Opel brand will introduce a three-panel hardtop version of its Astra as well. “We expect that you will see more manufacturers opt for this solution in lower priced segments as the costs decrease,” says Patrik Widerstrand, business project leader for the C70.—KMK