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 61st International Motor Show,
2005 Frankfurt,

Opel Astra Twin Top

Astra TwinTop: New Roof Concept Performs “Cabrio-Coupé Lambada”


Opel livens up the Frankfurt International Motor Show (September 15–25), breathing life into motionless cars with a new dance on its stand. Visitors can watch the Astra TwinTop, which celebrates its world premiere in Frankfurt, do the “Cabrio-Coupé Lambada” as it opens and closes its roof.

At the touch of a button, a total of five sections, including the two C-pillars, go through a sequence of precisely choreographed moves with the help of five electric motors, eight hydraulic cylinders, 13 sensors and a 14-joint kinematics. The main advantage of the Astra TwinTop’s innovative roof concept: the individual components are smaller than in conventional systems and thus require less space when stowed in the trunk.

Design targets: Functionality follows styling

Designers and packaging experts began by defining their objectives according to this motto. GM/Opel engineers, in close cooperation with specialists from CarTopSystems (CTS), then went on

to develop the ultimate roof concept, to ensure not only attractive lines, but also outstanding interior space for a retractable steel hard-top. Thanks to the TwinTop’s generous shoulder and knee room, adults in the rear have plenty of space to travel comfortably. Project Manager Klaus-Rudolf Reuter says: “We analyzed all retractable roof systems on the market very carefully. Very soon we realized none were compatible with our goal of creating an exciting design with a spacious interior and a lot of luggage capacity. So the only option was a completely new concept.”

Spectacular: A dance of components

Aside from developing the concept, realizing the first three-part retractable steel roof in a production-car required a great deal of fine-tuning. This is reflected in the sequence of movements controlled by the five electric motors, eight hydraulic cylinders and 13 sensors every time the top is opened or closed – dubbed the “Lambada” by the engineers.

The fully automatic dance of components is initiated at the touch of a button located on the upper edge of the windshield or via remote control in the car key. To set the stage, the frameless side windows move a few millimeters downward out of their moldings. Then the trunk lid tilts up towards the rear of the car, while the front roof element simultaneously eases out of its fixtures. In the most spectacular scene, the three roof sections role backwards, pivoting on the two main bearings located in the area of the rear seat-backs. At the same time, the rear window moves forward out of its fixtures on the C-pillars and the cover behind the rear head restraints rises up. The three roof panels then slide underneath and store themselves neatly in the upper half of the trunk. Before the panel behind the rear head restraints and the trunk lid return to their closed positions, two small flaps fold out for each, nestling tightly against the body flanks to seal the gaps. In the finale of the almost 30-second performance, the side windows move back upward into their original positions. A subtle acoustic signal marks the final curtain. The mechanism is designed for faultless operation. The opening procedure can be initiated only when the internal divider in the trunk is in place. Connected to a contact sensor, the protective cover divides the luggage compartment horizontally and defines the usable space when the top is down, preventing the roof panels from crowding pieces of luggage.

Project Manager Reuter emphasizes that, “the show character is no more than a welcome side-effect. We were most interested in optimum functionality – with as few moving parts as possible.” Proposed solutions involving a large number of puzzle-like roof segments quickly landed in the waste paper basket. “The designers wouldn’t agree to those ideas either, because so many seams would have disturbed the clean lines. Our solution is not only successful in terms of looks, it is also aero-acoustically flawless.”

An absolute first: Power loading assistance

GM/Opel engineers also built an absolute novelty into the Astra TwinTop, the power loading assistant Easy Load. Thanks to this innovation, the luggage capacity of 200 liters in the cabrio configuration can be fully utilized. At the touch of a button, the horizontally stacked roof panels in the trunk are raised 25 centimeters. Luggage and shopping bags can thus be easily removed or stowed under the protective divider. “We put a tremendous amount of thought and effort into the faultless realization of this idea,” says Klaus-Rudolf Reuter. “I’m sure customers will appreciate this standard feature, because it keeps their luggage easily and readily accessible, even when the top is down.”

In addition, the size and format of the Astra TwinTop’s approximately 440-liter luggage compartment underline its suitability for everyday use. The slim construction of the trunk lid linkage also makes a space-saving contribution. Instead of the normal bulky tubular frame construction, a complex 14-joint kinematics, which moves the trunk lid during opening and closing, makes its premiere in the Astra TwinTop. The trunk floor has been lowered by three centimeters compared to the Astra hatchback, creating additional space. The practical and convenient design of the trunk is accentuated by storage compartments in the sides, the load-through hatch for skis and the spare-tire well, in which a spare wheel or four-part wind deflector and tire repair kit can be stored.

Despite the fact that the concept broke new ground and had to meet extremely high standards in terms of quality and functionality, the Astra TwinTop was developed in a record time of only 17 months. Reuter says his team’s performance was also due to exceptionally efficient use of state-of-the-art computer simulation programs as well as engineering partner CTS’ long-term involvement in the development and production processes. The four-seat cabrio-coupé will roll off the production line in Antwerp, Belgium – where the entire roof module will be installed on site – at the beginning of 2006.

August 23, 2005


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