In the low-slung seat of the Cobra, Ralf Hotchkiss careered down a steep, rocky seven-mile trail on Mount Tamalpais at speeds pushing 25 miles per hour one spring afternoon in 1988. Mount Tam, as it's called, rises 2,600 feet above sea level amid hundreds of acres of redwoods and coastal hills in Marin County, Calif., and is a favorite spot for mountain bikers. But the high-tech, blue-and-black vehicle Hotchkiss was riding stood out from the pack. For one thing, the Cobra has four wheels and disk brakes; for another, many of its riders can't walk, let alone pedal. Designed by Bay Area engineer John Castellano, the Cobra is an off-road wheelchair that allows people with disabilities to indulge in mountain-bike fever.
On that spring day in '88, Hotchkiss, a 44-year-old paraplegic engineer who has spent the past decade designing all-purpose wheelchairs for use in Third World countries, was test-riding the Cobra. Castellano and his wife, Marisa, had spent two hours taking turns towing Hotchkiss behind their standard mountain bikes to the top of the trail, passing a 12-foot tow rope back and forth. At the top, Hotchkiss told the couple, "Don't expect me to go down too fast. I want to enjoy the scenery." After all, it was a trail he had never been on before. "But once I got going and the wind started whistling through my hair, I couldn't help but let the brakes go." recalls Hotchkiss. "I went whipping around those corners with all four wheels sliding and clouds of dust coming up. The Cobra handles like a tiny Porsche. It feels like you're stuck to the road."
Who better than Hotchkiss to take that hair-raising descent? It was he who inspired the Cobra. Castellano hit upon the idea for the chair after reading a 1984 article in Car and Driver about new wheelchairs being road tested by Hotchkiss. An MIT graduate in mechanical engineering, Castellano, who grew up in Ridgefield Park, N.J., worked for Hughes Aircraft in Los Angeles. He had designed bicycles, go-karts and skateboards since he was a teenager, and in 1984 he got hooked on mountain-biking.
In 1986, inspired by Hotchkiss's article, Castellano began sketching designs for an off-road wheelchair. The following year he left Hughes, moved to the Bay Area and started his own company, Up And Over Engineering, in El Cerrito. He got in touch with Hotchkiss, who lives in Oakland. After giving the concept the nod, Hotchkiss became a technical consultant. "It was the most ambitious project I'd ever undertaken." Castellano, 34, says. "No one else was doing this, and it seemed like it needed to be done."
The result is the Cobra, a cross between a go-kart and a mountain bike. The 40-pound vehicle has a standard wheelbase of 30 inches, chromoly tubing, two-speed hand rims (20 inches and 12 inches in diameter), aluminum handlebars that steer like a bicycle's, four-wheel disk brakes and Specialized mountain-bike tires. "Its layout and geometry are optimal for downhills, but to make it climb, you have to be sure it won't tip over backward," Castellano explains. "To do that, I made the seat as low as possible and moved the rear wheels back about three or four inches from where they'd be on a racing chair."
With the help of mountain-biking friends and paraplegics such as Hotchkiss, Castellano tested the prototype on paved roads, vacant lots, dirt trails—even in the Mojave Desert while waiting for the wind to come up for land sailing, another passion of Castellano's. In 1989 the Cobra was ready to be offered for sale. It didn't take long for the chair, named after the A.C. Cobra race car, to gain a following among wheelchair-riding thrill seekers. Castellano has now custom-built and sold 28 Cobras, which go for $3,500 each, including water bottle. Mountain & City Biking magazine has called it "as advanced as any quality |all-terrain bicycle] on the market.' " Riders quickly discovered that it can take switchbacks at high speeds, coast over rocks without a hitch and gain two feet of air off' a jump. The only thing the Cobra can't do is climb steep hills, so Castellano is now working on a variable-speed, lever-drive system to do just that.
The Cobra provides plenty of off-road adventure for those who can afford a specialty chair. Hotchkiss, the recipient of a 1989 MacArthur Foundation "genius grant." is working on less expensive options. His latest design is the Torbellino II (torbellino is Spanish for "whirlwind"), a folding, lightweight, all-purpose wheelchair for use in Third World countries. Rather than building and exporting the chairs—the cost of which would be prohibitive in poor countries—Hotchkiss teaches engineers from abroad how to make them in their homelands. In some countries the Torbellino II can be bought for as little as $150, because it's made with locally available parts and equipment. By exporting the technology, Hotchkiss is helping to revolutionize how disabled people around the world participate in sports and recreation.
Designed for rural terrain, the Torbellino II is also good for basketball, road racing and tackle football. "Some of these football games are like demolition derbies," says Hotchkiss. "it's a real measure of chair design, because a chair can get hit from any direction, anytime, any way."
A sleek red-and-black chair weighing 34 pounds, the Torbellino II has bicycle tires in the rear and seven-inch wheels, designed like those on pushcarts in Zimbabwe, in the front, "instead of being hollow like our semipneumatic, semisolid tires on kids' wagons in this country, the tire is wide on the surface but narrow going down into the wheel, like an I beam or a I." says Hotchkiss. "The leg of the T gives it soft suspension; the top gives it flotation over soft ground and the ability to wobble over rocks."
The technology is a variation of today's high-tech ultralights, designed to be made at very low cost out of mild steel. "In the Third World, people can't afford a special chair that's good only for the race," Hotchkiss says. "How are they going to get to the race? Or what are they going to ride every day? This serves all those purposes."