Bentley Arnage Drophead Coupé

Engineering and specification

Work on the Arnage Drophead Coupé started in January 2004 and only the introduction of new technologies and advanced production techniques meant it could be produced in such a short timescale, as Ashley Wickham, chief engineer, explains:

"The real challenge of this programme was to develop a car that had such stylish lines in the timescale we had available. With good planning and close teamwork we were able to combine simultaneous engineering and design with the latest 'fast-track' technologies - it was a great mix of conventional and new thinking.

"For example, right up to the point of engineering, digital data was taken from the clay model's surfaces on a day-by-day basis, even while some parts of the clay were still evolving. This ensured we could transfer the right design feeling directly to the CAD surfaces which are used to make the tooling. And to ensure that the designers could continue to make quick revisions to the car, new technologies were adopted as the programme progressed. The body panels, for example, were actually pressed from special resin-based tools which could be machined in a matter of days."

The twin-turbocharged V8 engine, double-wishbone suspension and extremely rigid body structure of the 2005 Model Year Arnage R provide a state-of-the-art basis for the Drophead Coupé. The show car is powered by a 450bhp (336Kw) version of the Arnage R's 6.75-litre twin-turbocharged intercooled V8 engine and produces 875Nm (645lb ft) of torque.

The Arnage's impressive ventilated brakes with Electronic Stability Programme, Antilock Braking System and Electronic Brake pressure Distribution work in conjunction with the independent double wishbone suspension and a computer-controlled adaptive electro-hydraulic damping system to ensure optimum stability and handling at all times. The Arnage Drophead Coupé also benefits from the introduction of the new comfort suspension system used on the Arnage R.

To guarantee the Drophead Coupé met aggressive body stiffness targets set at the start of the project, significant stiffening members have been added to the underlying Arnage chassis. These strengthened steel parts lie in the sill section of the car and extend into the A-pillars that form the windshield frame. Beneath the car, cross-bracing members reinforce the whole body shell. The result is a car that displays remarkable body stiffness.

Strengthening has also been applied to the body structure behind the rear seats where an advanced rollover protection system has been fitted. This immediately detects if the car is in danger of inverting and deploys two hoops that are integrated within the rear headrests. In conjunction with the strengthened front windshield frame, these are capable of supporting the entire weight of an over-turned car.

...continued