How'd They Do That?
The Helios design team borrowed a vintage Lincoln Continental four-door convertible as an idea-generator, but its nearly three-ton curb weight, foot-thick doors, twist-o-flex structure, and trunk-consuming top had no good ideas to offer. So the team started with a clean sheet of paper--and Chrysler's complete finite-element computer model of the 300. Some 20 structural reinforcements were then developed, all of which can be welded or bolted onto the existing unibody to compensate for the missing roof structure.
A patented center bulkhead consists of heavy reinforcements that span most of the height of the truncated B-pillars to route crash energy down through a beefy beam that runs straight across the car. It's welded to the top of the existing center tunnel and tied into the tall new tunnel reinforcement that, along with lower side-rail reinforcements, provides most of the bending rigidity. The front seats are modified to nest over the bulkhead beam, preserving the full range of front-seat travel and ample rear-passenger foot space. Similar cross-car reinforcements under the front of each rear-seat cushion provide additional side-impact protection. Underneath the car, a large X-brace spans the entire cockpit, and two V-braces connect this brace to the engine and rear suspension cradles. These reinforcements bolt on to preserve serviceability, and they reduce ground clearance slightly. A large panel welded in behind the rear seatback boosts torsional rigidity and helps support popup rollbars behind each rear headrest.
The resulting structure survives Chrysler's full battery of computer crash simulations without resorting to the "basket handle" B-pillar some larger open cars have used. Of course, pruning the B-pillar necessitated the revival of another long-lost art: four-door pillarless hardtop glass. A new regulator miraculously maneuvers the longer rear-door glass backward and down on an angle, clearing the rear-wheel cutout to disappear completely.
The final miracle ASC managed to work is the Xpanse top, which shrinks from 68 inches long to fit in an 18-inch-long, 12-inch-deep recess. It essentially works like most other shorter tops except that the side rails along the forward two-thirds of the top scissor inward, pulling the header panel rearward to fit the space of a shorter top. Shoulder-room intrusion is minimal. Accommodating the top well required moving the fuel-filler down and aft a bit, which may turn out to be the trickiest part of the Helios concept to productionize.--Frank Markus
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