Pillars of Salt: Inflatable Roof Pillars Could Aid Future Design

It’s a pity the retro design craze seems to be petering out, because an enabler is just now emerging that would allow designers of the next generation of Camaro, Mustang, Challenger, T-Bird, Beetle, and others (a latter-day Citroen DS, please!) to recreate a key detail that has been impossible to achieve while meeting today’s roof-crush and offset frontal-collision standards: those delicate, easy-to-see-around roof pillars. Fat pillars lend a cartoonish, brutish mien to every retromobile out there.

The solution comes from an unlikely source — Swedish airbag supplier Autoliv — and, in fact, it leverages airbag technology. But instead of inflating a cloth bag, it inflates a folded steel tube that is integral to the vehicle’s body structure. Up until now, the only way to make a car capable of supporting one and a half times its weight on the roof (as required in 2012) was by giving all the pillars a thick, beefy section, and/or incorporating ultra-high-strength steel or carbon-fiber tubes in the pillars. But until you threaten to turn turtle, holding the roof up doesn’t require any more strength now than it did in the 1950s and ’60s.

Autoliv’s idea is to provide a slim, minimalist pillar until an accident is detected, then inflate a pleated steel tube so it expands to a large, strong section. This expansion pops the interior trim off, but should leave the outer surface and windshield undisturbed. The inflator uses a nitrogen-rich salt or chemical like those used to fill airbags, but generates an order of magnitude more force — 300 to 450 psi. The tube is made of 0.06-inch-thick steel that’s typical automotive-grade strength (58 kilos/square inch yield–high-strength steel is too brittle for this type of application). It’s welded closed on each end and weighs 3.5 ounces, representing a 10-percent weight savings. Cost is little more than the price of the inflators. Within 10 milliseconds of crash detection, the A-pillar expands from within its dainty 0.9-inch-wide pillar (a third the size of a typical modern pillar) to a stocky 2.9 inches wide. This increases the pillar’s stiffness by 45 percent. The unit will be replaceable after a crash.

Before inflation, visibility is said to be 25 percent better than in the average car. According to Dr. Bengt Pipkorn, project leader in Autoliv’s active body structures department, this research has been conducted in conjunction with Saab. He reckons the technology could be in production by 2020, but notes that (naturally) it has to be designed into the body structure from the outset–there’s no retrofitting such a gizmo into an existing design.

Body pillars are not the only potential applications for this technology. Mercedes-Benz displayed an inflatable side-impact door beam concept at the 2009 Frankfurt motor show that expanded into the space the door glass ordinarily drops into to increase door strength during a side impact. Another intriguing use Dr. Pipkorn described is a tunable front-end crush structure that would provide softer crash-rail performance in low-speed collisions, but inflate to become stiffer in high-speed collisions. This could be a boon for the coming wave of short-nose electric vehicles.

Here’s hoping this promising new technology helps usher out the hunkered-bunker era in favor of retro Futuramic visibility.

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