Saab on a roll

Saab’s 9-3 Convertible is the first soft top to achieve the maximum rating of five stars in the Euro NCAP collision test programme thanks to its Dynacage active roll-over protection system.

Saab’s 9-3 Convertible is the first soft top to achieve the maximum rating of five stars in the Euro NCAP collision test programme.

The rating comes thanks to Saab’s Dynacage active roll-over protection system. Saab’s head of safety also put the result down to Saab’s policy of basing its designs on a study of real-life accidents.

Saab’s crash testing is designed to replicate real accidents, drawing on a database of 6,000 real-life collisions. For the 9-3 programme the company tested 75 crash configurations, compared to the 15 that are legally required. These included head-on and offset frontal impacts, car-to-car and truck-to-car side impacts, and eight types of roll-over.Roll-overs are a comparatively rare type of accident but have serious consequences when they do occur.

The DynaCage combines rear roll-bars which rise up automatically, reinforced windscreen pillars and side sills, plus seat belt pretensioners in all seating positions.

The two spring-loaded roll-over bars, behind the rear head restraints, are high-strength aluminium alloy for low mass and to aid quick deployment. They are released by a small pyrotechnic charge when the the car’s diagnostics senses a roll-over and are designed to be raised and locked by the time the car reaches 90 degrees to the ground. At the same time all four seat belt pretensioners are activated.

The convertible shares its basic high-strength steel safety cage with the 9-3 saloon, which also won a five-star rating. In addition, the convertible has strengthened windscreen pillars and header rail plus reinforced floor-level cross members. An additional torsion box is situated between the rear wheel housings and enlarged side sills. Saab said that the strengthening and the DynaCage hardware contribute a major part of the convertible’s 95kg weight gain over the saloon, taking it to a kerb weight of 1,685kg.

Common to all 9-3s is a front bumper beam made of 900N/mm2 boron alloy steel which spreads impact forces across the front structure, allowing controlled deformation almost irrespective of the point of impact. In a side impact the bottoms of the doors interlock with the sills so that forces are shared across the whole side of the car.

At the rear, two longitudinal members are designed to buckle and deform downwards, dissipating impact energy towards the lower body structure and forcing the spare wheel to rotate towards the vertical to provide additional protection for the rear passengers. The fuel tank is mounted in front of the rear axle, away from any point of impact.

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