New chassis technologies from BWI Group have been selected to help meet the design challenges of the new Range Rover Sport. The vehicle will use BWI’s latest air suspension and lightweight active roll control (ARC) actuators to allow a combination of luxury, refinement and off-road ability. Both the roll control actuators and the air springs are manufactured at BWI’s plant in Luton, UK.
“High performance SUVs need to provide superb, sports-car-like road holding, outstanding off-road capabilities, and limousine-like comfort,” explains BWI’s director of suspension system engineering, Doug Carson. “A vehicle with such a wide range of requirements is a real challenge for chassis engineers, as we can’t accept any of the compromises normally required to deliver excellence in one specific area of capability.”
BWI worked with specialist supplier Firestone to develop a new air sleeve for the company’s air suspension modules. A bespoke nylon-reinforced rubber compound was developed with what’s been described as exceptional hot and cold climate performance, and the wall thickness was reduced to cut hysteresis. These changes, together with detailed component optimization to reduce friction, are said to help achieve outstanding absorption of small road irregularities. To provide the protection and durability needed for off-road activities, the air sleeves are sheathed in an aluminium restraining guide. Weight has been reduced through careful design analysis and by increased use of aluminum.
BWI technology is also central to the vehicle’s new Dynamic Response system, which is calibrated to almost completely eliminate body roll at cornering forces up to 0.4g. The company is supplying elements of its proven Active Stabiliser Bar System (ASBS), including the all-important ball screw rotary actuators that provide roll-control torque up to 1,500Nm. When cornering forces are detected, the front and rear actuators apply a counter-acting rotational torque to the vehicle chassis via the cast lever arms of the stabilizer bar system. Independent control of the front and rear roll stiffness allows real-time optimization of the oversteer/understeer characteristic, improving turn-in, comfort and safety.
The BWI actuators now offer 134° of rotation compared with 90° for the previous-generation system, helping to deliver a remarkable 260mm of wheel articulation at the front and 310mm at the rear to further improve extreme off-road ability. The very high angular articulation also increases packaging flexibility, allowing a compact architecture that does not require intrusion into unrelated spaces. The system is also shorter than the previous-generation system, thanks to a reduced ball screw length. Mass has been reduced by 2.4kg at the front and 2.2kg at the rear, largely through the use of hollow torsion bars with cast splined lever arms, also supplied by BWI.
BWI is exhibiting in the Vehicle Dynamics Zone at Automotive Testing Expo Europe 2013, stand number V2206.