OAKLAND -- Ralf Hotchkiss never let much interfere with his restless independence before or after his motorcycle accident, so it was not unusual for him to be hitchhiking, wheelchair and all, on Ashby Avenue that day in October 1975. Deborah Kaplan, a law student disabled after a shallow dive, gave him a lift in her green Dodge Dart.

They chatted. They went their separate ways. They found themselves working together in Ralph Nader's Washington office. They fell in love. They married. They moved back to the West Coast to a house on a hillside overlooking the Bay and hazy downtown Oakland.

Now the couple has a loud, wiry, lightning-quick 2-year-old son named Desmond who is proving to a skeptical world that two parents who use wheelchairs can raise an active child.

Friends speak of the couple in terms usually reserved for high-speed locomotives: You wouldn't want to get in their way. Kaplan and Hotchkiss dislike the legal restrictions that make it difficult for the disabled to become parents, and Kaplan is organizing a movement to encourage disabled Americans who want to raise families.

"They are excellent role models," said Ed Roberts, president of the World Institute on Disability. "They have both succeeded professionally and have now opened their lives up for a child."

While working with Nader, Kaplan founded the Disability Rights Center (she exposed manufacturers' failure to provide proper instructions on wheelchairs and home respirators) and Hotchkiss founded the Center for Concerned Engineering and was the co-author of "What To Do About Your Bad Car," usually called "The Lemon Book." An engineer and irrepressible tinkerer, he once accidentally set fire to the National Press Building while testing a defective electric blanket.

Now they spend much of their time attending to Desmond Kaplan Hotchkiss. Sitting in a wheelchair, Hotchkiss can hoist Desmond by the straps of his overalls onto his lap and, with the boy's head resting under one arm, swiftly change his diapers. Roberts says Kaplan, using only gentle persuasion, can coax the boy onto a couch or bed for the same purpose.

Hotchkiss has not been able to use his legs since his motorcycle missed a curve on an Illinois road in 1966, when he was 18, and he broke his back. He remembers swearing so violently as he lay on the pavement that the farm woman who had come to help him blushed in embarrassment.

Once it was clear he would survive, he said he worried about two things: Could he still enjoy making love, and could he be a father? A visit by a female friend shortly after the accident eased his mind on one count, and a year recuperating at home and playing with his baby sister, Sara, convinced him he could raise a child from a wheelchair.

He had been interested in designing devices to help the handicapped since, at age 12, he read about Helen Keller. He finished at Oberlin, where he engaged the visiting Nader in a discussion of Corvair suspensions, and then went to work.

Kaplan was 21 when she dived into a shallow California stream in 1971 and broke her neck. She has since learned to walk, slowly and awkwardly, with the help of a cane. She has overruled the therapists who insisted that she walk everywhere and uses a wheelchair, for safety and mobility, whenever she is outdoors.

That determination to write their own rules also governs their handling of Desmond. "This might seem irresponsible," Hotchkiss said, "but when I drive him to day care, I let him get out of the car right on the sidewalk. He walks across the lawn and rings the doorbell. I don't get out of the car."

Between ages 1 and 2, his mother said, Desmond was like other children: "crazy, with no common sense whatever." Now, according to Hotchkiss, he seems "remarkably self-sufficient and responsible for his age." As able-bodied as they come, Desmond has nonetheless wheedled his father into making him his own small wheelchair for occasional play.

Desmond has discovered that he can evade his father if he hides under the workbench of Hotchkiss' hopelessly cluttered workshop in their Oakland home. Father and son then negotiate. "We usually work it out," Hotchkiss said.

Lowell Dodge, a friend from Nader's office who is now head of affirmative action plans for the General Accounting Office, noted that "when Desmond misbehaves, which he often does, Ralf is not put off by it, but seems to delight in it. It is that adventurousness which Ralf wants to encourage."

The couple adopted Desmond after Kaplan failed to become pregnant, the possible result of Hotchkiss' low sperm count from sitting for long periods. Social service agencies were reluctant to consider disabled couples as adoptive parents, so they arranged an adoption privately.

Desmond's biological mother was young enough to have been exposed to the recent integration of disabled children into regular schools. She knew that Kaplan and Hotchkiss used wheelchairs, "but she didn't think it was such a big deal," Kaplan said.

Desmond was born in October 1985, 10 years to the month after his new parents met. Kaplan discovered, as she compared notes with able-bodied parents, that her fears and apprehensions about handling an infant were no greater than theirs. "Desmond rolled off the bed at five months," Kaplan said. "But someone said, 'Oh, yeah, that happened to me too.' "

Now they are looking to spread the message of parenthood for the disabled. Kaplan, drawn into the struggle to help a disabled San Jose woman, Tiffany Callo, regain custody of her two infants, has begun to work with a private California-based group, Through the Looking Glass, in forming a national legal and legislative effort for disabled parents' rights.

Adoption agencies have been reluctant to work with such couples, and care-giving agencies for the disabled have discouraged them from bearing and raising children. Provision is rarely made for extra benefits if a disabled person becomes a parent.

Hotchkiss has continued to work on improved wheelchairs and other devices. He has traveled to Nicaragua and other Third World countries to develop techniques for producing more efficient aids for the disabled from simple materials. The Veterans Administration and a private group, Appropriate Technology International, have sponsored many of his projects. He also teaches engineering and design at San Francisco State University.

Kaplan has continued her legal work in disabled rights, including advising state Sen. Milton Marks (D-San Francisco) on bills to guarantee rights and financial assistance for disabled parents. She said she thinks it may be time to start a national organization both to promote such rights and to provide parents information she and Hotchkiss had to gather by trial and error.

And then, noting Desmond's imperial attitude about his central role in the family, Kaplan mentioned the possibility of adopting a second child. "It's time to unseat the king," she said.