Volvo Raises Safety Bar with C70 Convertible
Although Volvo has been working to become more stylish, the people in Gothenburg are still pursuing safety, as is evident in the 2007 C70 Convertible. That’s right: a safer convertible. Although sedans like the S40 and estates like the V50 have hardtops that utilize the roof structure in order to deal with crash energy management, the C70 doesn’t afford that opportunity. So while the engineers used the Volvo-developed safety cage structure that was developed for the S40 and V50, they had to deploy some other technologies, like a specially designed side-impact airbag and rollover protection system, to help make the C70, well, a Volvo.
Volvo engineers paid special attention to the C70’s frontal impact safety, since frontal collisions account for more than 40% of all collisions. They divided the C70’s structure into zones, each with its own deformation properties. The outer zones accommodate the most deformation and energy absorption, while less deformation takes place the closer the collision approaches the passenger compartment. The C70’s mid- and front-sections are constructed with high-strength steel, while the main members of the space frame are constructed from extra high-strength steel. The doors play a vital role in the C70’s safety structure, and so have been reinforced with a longitudinal aluminum member along the upper edge, which channels forces backwards into the body structure itself. The engine, which is transversely mounted, also contributes to passenger safety, thanks to its compact construction and efficient packaging. The turbocharger, alternator and air-conditioning compressor are mounted as close as possible to the block, while a generous amount of space is left between the engine and the passenger compartment, allowing the engine to move as much as 5.9-in. rearward before the crankshaft comes into contact with the transverse beam beside the cowl.
In the event of a side impact, the C70 utilizes the latest version of Volvo’s Side Impact Protection System, which relies on the B-pillars to act as the main intrusion inhibitor. The pillars have extra reinforcements and are linked to each other through a transverse floor member. In all, there are five transverse members placed along the length of the car, while a flexible deformation box between each B-pillar and the transverse member provides added absorption of collision forces. The C70’s door sills are raised behind the B-pillars to offer improved protection, while the doors are designed to hook onto the B-pillars and remain closed when they are subject to a collision, allowing energy to be sent through the entire vehicle body, around the passengers, while transverse members in front of the passenger compartment and a horseshoe-shaped member behind the rear seat channel forces to the opposite side of the body. If all this isn’t enough, Volvo engineers worked alongside their counterparts at Autoliv to develop an innovative door-mounted inflatable curtain that provides added protection for front seat occupants. The curtain ejects in an upward motion from the upper door panel, while its double row slat construction provides support for the bag to remain upright for better head protection. The curtain also deflates slowly to provide added protection in the event of a rollover situation.
Probably the most confounding problem any engineer would have to deal with is how to protect passengers in the event of a rollover in a convertible. Initial protection takes the form of a stronger A-pillar, which is designed to withstand very high forces thanks to the use of extra high-strength steel and hydroforming. Hydroforming allows the A-pillar to be shaped optimally without any joints or sharp angles to threaten its integrity. The pillar features different steel thicknesses at varying points, which makes it stronger at critical junctures, such as at the base along the body and at the top where it meets the windshield. Additional protection is provided by the C70’s Rollover Protection System, which features metal bars that come up from behind the rear passenger headrests to provide added support in a rollover situation. Activated by a pyrotechnic charge, the bars deploy when the vehicle’s sensor indicates a roll condition, whether the roof is open or closed. This means that if the vehicle rolls while the roof is up, the bars will protrude through the rear window, shattering it to smithereens.
To demonstrate just how strong the C70’s body structure is, Volvo conducted a live side-impact crash test involving an XC90 SUV and the ‘07 C70 (with the top down). The test scenario was established as follows: The C70 was accelerating from a stop, moving along at about 15 mph, when the XC90 sped through a stop sign at a speed of 31 mph. The results were surprising. While the XC90 experienced minimal damage, the C70’s robust door structure and B-pillar absorbed most of the energy during the crash. The side curtain airbag provided ample support for the test dummy to experience minimal injuries. Amazingly, the driver’s side door, which was badly mangled, could still open and close easily. The test proved Volvo remains at the top when it comes to safety, even when going topless.—KMK