The ultimate Sisyphean household chore may well be mowing the grass. Yet Americans remain obsessed with the perfect lawn.

Marry that quest with our fascination with clever gadgets and ingenious technology, and the appeal of something called the zero-turn-radius mower becomes clear: Work seems to turn into play, exertion into recreation. If time has supplanted money as the currency of the day, this is one mower zipping along with the zeitgeist.

With his old Honda lawn tractor, it used to take Dave LaRocque three hours to cut his half-acre of grass in Penllyn, Pa. And it took an additional hour for the trim work around the trees and flower beds with a walk-behind mower.

These days, he does the job in half the time with his zero-turn-radius mower, also known as a ZTR, or simply a Z.

"You can go down a strip, turn around and go right back. And you can get a lot closer to shrubs and beds," said LaRocque, 72, a retired insurance-underwriting manager. "I actually look forward to getting out and cutting the grass."

Once used exclusively by commercial gardeners and landscapers, ZTRs are all the rage among weekend yard jockeys. An array of manufacturers are making gasoline-powered models designed for consumers, and as prices have tumbled -- $2,500 will buy a basic machine, $5,000 can get you a top-of-the-line residential model -- sales have soared.

"It's the fastest-growing segment in our industry," said Greg Weekes, group marketing manager for John Deere riding lawn equipment.

According to the Outdoor Power Equipment Institute, consumer ZTR mower shipments are up over 75 percent as of May versus the same period in 2004. James McNew, vice president of technical and marketing services, declined to specify how many mowers that represents.

ZTRs are not new, exactly. The first commercial models, distinguished by twin-lever steering and an out-front mowing deck, were developed in the mid-1960s. They are so named because they can pivot in place and spin on a dime, thanks to separate hydraulic motors or transmissions on the rear wheels that enable the wheels to move forward or backward independently.

"They're highly maneuverable and efficient," said Toro Co. spokesman Mike Ferrara. "You just whip around trees. You don't have to make multiple passes or use a weed whacker. It's safer because you have great visibility, and it's fun."

No doubt about that. Piloting a Z is like riding a Tilt-a-Whirl and mowing the lawn at the same time.

That's what captivated LaRocque. For years, he watched enviously as commercial landscapers aboard agile ZTRs barbered his neighbors' lawns with dispatch. In May 2004, he took the plunge, shelling out $3,000 for a Toro TimeCutter 17-42Z.

He doesn't regret a penny.

"The engineering is terrific," he said as he ticks off some of the features of his 17-horsepower machine with the 42-inch cutting deck.

Consumer Z's come with all the bells and whistles: comfortable high-back seats, adjustable footrests and cup holders, engine covers, electronic start, electric clutch.

"They're built to commercial standards, so they're tougher and hold up better than small tractors, where the quality has really slipped," said Mark Nilsson, owner and operator of Marple Tractor & Mower Service in Broomall, Pa.

Z's cut grass faster, too.

"Some of them have three blades, and they can move along at 8 mph, versus 4 to 5 mph for a typical lawn tractor," said Jerry Peda, sales manager for Niemayer's Service Center in Newtown Square, Pa., which sells about 25 John Deere ZTRs a year to homeowners.

But they take some getting used to.

"It's not something the average person can just jump right on and start trimming with," said Lee Reynolds, owner of Lee's Power Equipment in Berwyn, Pa. "There's a learning curve."

Z's don't have steering wheels, for example -- you operate them with two levers.

"The sticks can be a little confusing at first," Reynolds said. "To turn, you push one forward and pull the other back."

It's similar to steering a shopping cart, said Toro spokeswoman Kathleen Hennessy. "When you want to turn right, you push with your left hand, pull back with your right. It's really very intuitive."

Maybe. Before perfecting their skills, amateurs usually carve a few doughnuts in the carpet.

"If you turn too sharp, too fast, the pivoting rear wheel can dig in and tear up the turf," LaRocque warned. (He may have gotten the knack quicker than most; in the Army, he drove a 50-ton M48 tank with zero-turn-radius capability.)

Maneuverable, ZTRs are. Versatile, however, they are not.

Unlike lawn tractors, "they are not made for plowing snow or towing a heavy cart," said David Lightkep of David H. Lightkep Inc. in Maple Glen, Pa.

And on slopes, ZTRs can be problematic.

"On hillsides, they tend to drift, and you have to constantly correct for that to stay in a straight line," John Deere's Weekes said.

If a hill is too steep, flipping is a possibility, which is why some ZTRs, especially commercial models, come with roll bars. But the experts say ZTRs are ideal for lawns that are more than an acre and generally flat, with lots of things to steer around.