Reinventing the yo-yo: a simple toy gets seriously techno.

Got an extra 400 bucks? How about spending it on a yo-yo? A really nice yo-yo, a state-of-the-art, forged-magnesium-alloy, ultralong-spinning yo-yo. Later this year, Duncan Toys, a seller of inexpensive yo-yos for 75 years, will roll out this new high-end yo-yo, which the company plans to call the Freehand Mg. It comes with the latest in axle and bearing technology, and its balance is ensured with precision tooling to micrometer tolerances by a computer-controlled lathe.

"It's gonna be awesome; says champion yo-yoer Stephen D. Brown, Duncan's chief yo-yo designer. "I've gotten a few prototypes of it. It rules!"

Not so long ago, Duncan sold only $2 or $3 yo-yos, many of them not much different from the product that the company offered in 1929, when Donald F. Duncan Sr. bought a fledgling yo-yo company. In the last decade, however, the company has been scrambling to keep up with a wave of technological innovation launched by other yo-yo aficionados and small manufacturers. Those developments have been transforming yo-yos into precision instruments.

But isn't a $400 yo-yo a bit over the top? Even Brown admits that its premium materials and precision of the machining go well beyond what's needed for even the highest levels of play. But with those additions, Brown says, the company has made a topnotch toy for dedicated yo-yo fans and competitors, and the high-tech plaything does double duty as a publicity gimmick.

Manufacturers are in the midst of a "science-innovation war," says Dale Oliver, a yo-yo producer and champion yo-yo player. "It's the search for the Holy Grail of the yo-yo."

Fans today commonly pay $40 for a competition-grade yo-yo. It can sport features such as minimal-friction axles, a string-grabbing response system for enhancing tricks, and modular construction for easy repairs and upgrades.

The high-teching of yo-yos has fomented a revolution in the ways in which people play with yo-yos. Today's hotshots put their ever-spinning yo-yos through long-lasting sequences of leaps, bounces, and swings as they weave the string on their fingers into patterns resembling configurations in the game cat's cradle.

Yo-yoing has gone extreme.

GETTING SOME SLEEP As mostly everyone knows, a yo-yo is a puck-shaped toy, usually made of wood or plastic, that's split down the middle except for an axle at the center that holds the two halves together. By means of a string in contact with the axle, a player can make the yo-yo fall and spin under the influence of gravity, unwinding the string as it descends. The yo-yo then rises as its rotation makes it rewind the string around its axle.

Yo-yos have been around for millennia. Historians have found evidence in a painting on a Greek bowl from around 500 B.C., for example. No one knows whether it was the ancient Greeks or Chinese or someone else who invented this toy.

The main difference between high-tech yo-yos today and all the yo-yos that went before is the time that the modern ones can spin at the ends of their strings. In yo-yo parlance, that's called sleeping. A few decades ago, a good player could make a yo-yo sleep for 15 to 20 seconds. Last October at the World Yo-Yo Championships in Chico, Calif., Rick Wyatt made his yo-yo sleep for 14.03 minutes, a new record.

For a yo-yo to sleep at all is a fairly modern development. Although the history is murky, it seems that right up to the early 1900s, strings were attached directly to taxies of such toys, which the French called "emigrettes" and the British called "quizzes". As it reached the end of its string, the simple yo-yo immediately would start its ascent.

By 1928, Pedro Flores had introduced to the United States a toy, called a yo-yo, from his native Philippines. With it arrived the key innovation behind today's versions: looping the string around the axle so that the axle could spin freely within the loop. Since then, yo-yo popularity has had its ups and downs, reaching its latest peak in 1998, largely through successful commercial promotions.

When a yo-yo sleeps, a world of tricks opens up. Those include rolling the dangling, spinning yo-yo along the ground "walking the dog", swinging it back and forth through a triangle of string "rock the baby, and swinging the flinging yo-yo in giant circles at the end of the string "around the world".

When a yo-yo sleeps for minutes, rather than seconds, the number of possible tricks climbs. "For 50 years, there were probably between 150 and 200 tricks," says Oliver, who runs Spintastics Skill Toys in Euless, Texas. He estimates the repertoire of tricks now tops 2,000. What's more, trick complexity has soared.

RIP VAN WINKLED Two modifications give today's yo-yos their remarkable sleepiness. Manufacturers have redistributed the weight across the disks and have practically banned friction between the yo-yo's spinning axle and the string.

Yo-yos sleep longer when their weight is concentrated at the outer edges, thereby increasing the rotational inertia. That has the effect of boosting resistance to starting the toy's spinning, but it also increases an already-spinning yo-yo's tendency to keep spinning.

This rim weighting also has a stabilizing effect that preserves long-lasting sleeps. This benefit derives because rapidly spinning yo-yos act as gyroscopes--spinning gadgets that resist changes in their orientation in space. The more a yo-yo's weight is biased toward the rim, the more gyroscopic stability the yo-yo exhibits.

Oliver says that in the early 1990s he came up with snap-on metal rings for rim weighting. Since then, another manufacturer has devised a way to mold such rings directly into yoyo bodies. Oliver notes that, as a result of this trend, overall weights of high-performance yoyos in the past 4 years have increased by about 50 percent.

To banish friction in their high-tech models, manufacturers have replaced the old wooden axle with a metal shaft surrounded by a donut-shaped bearing assembly, or transaxle. It's made of two concentric steel cylinders with balls between them.

The ends of the inner cylinder, or raze, make snug contact with the halves of the yo-yo, causing that race to spin with them. Meanwhile, the outer cylinder makes no contact with the yo-yo sides. The yo-yo's string loops around this outer race.

Such yo-yos lose only a trickle of rotational energy to the slight friction between the hard balls in the bearing and their races.

Today's yo-yo is a far cry from the first one to have a ball bearing axle. In 1984, a Swedish ball bearing company slapped a ball bearing into an unsophisticated yo-yo as a promotional gimmick. The resulting yo-yo was unplayable, yo-yoers remember. San Francisco dentist Thomas R. Kuhn, also known as Dr. Yo in the yo-yo community, is credited with inventing the first playable ball-bearing yo-yo, the Silver Bullet 2, in the early 1990s.

In the past 2 years, makers of high-end yo-yos have started offering transaxles with ceramic balls, which they claim can be made some 15 times smoother than steel. "That's the new, hot thing," Oliver says. Enthusiasts are buying up ceramic-ball yo-yos, but not everyone is convinced there are noticeable gains in player performance.

Making yo-yos better sleepers has also made them harder to wake up. So, some yo-yo makers have added mechanisms that permit the player to customize the gap between yo-yo halves, making it slightly wider for a more soundly sleeping yo-yo or slightly narrower for easier wake-ups.

There's a ratcheted, gap-adjustment apparatus in a German yo-yo known as the Mondial, which Duncan bought and has been marketing for $100 as "the most advanced yo-yo ever designed" When a player rotates the yo-yo halves in opposite directions between tricks, the machinery clicks into each new setting. The distance moved with each click is half the width of a human hair, the company claims.

Already on the drawing beards of one of Duncan's competitors is a yo-yo with an even finer ratcheting mechanism. However, that yo-yo--dubbed the Silver Bullet 3--was patented and prototyped just as the last yo-yo craze crashed, and so it hasn't yet been manufactured. Kuhn designed it with engineer Donald W. ("Captain Yo") Watson of Rohnert Park. Calif.

As string-trick masters execute complex, multistep maneuvers, they parse the yo-yos string into multiple segments, some of them switched back into the shaft's gap. The welter of string segments in the gap raises the chance that friction will cut short the yo-yo's sleep. To counter that threat, manufacturers have recently begun making yo-yos with gaps that are wider than the widest gaps of the ratcheting, adjustable yo-yos.

With this expansion of yo-yo gaps, a race has erupted among yo-yo makers. Gaps have become so wide that players need help in getting the sleeping yo-yo to snag the string when they want the yo-yo to wake up. So, yo-yo makers have developed response systems that put back in some of the friction that the new designs lack.

Late last year, for example, a manufacturer known as YoYo-Factory in Gilbert, Ariz., introduced an elaborate response system in which the pointed ends of springy plastic arms protrude into the yo-yo gap at eight positions surrounding the central bearing. Those points retreat from the gap's center when the yo-yo string is under tension. However, if the string goes slack, then the plastic arms grab the string, putting an end to the yo-yo's sleep. Thus, it takes the traditional upward jerk on the string to wake the yo-yo.

To fit more string into the yo-yo for increasingly complex tricks, some tinkerers make yo-yo gaps so wide that jerking the string no longer has any effect, notes Dick Stohr, a yo-yo enthusiast, teacher, and performer from Springfield, Va. These players have to throw extra loops of string around the yo-yo axle, in a move called a bind, to force contact with the response mechanism, he says.

DIFFERENT STROKES While advances in yo-yo technology influence how players use the toys, the creativity and preferences of players also feed back into the toy's designs. Yo-yo-related patent applications are up since 1998, the peak of the last yo-yo craze, Oliver notes.

Instead of weaving complex string patterns with sleeping yo-yos, some yo-yoers pursue another type of play in which their yo-yos are ever zooming to the ends of their strings and back. Called loopers, these players keep their yo-yos--often one in each hand--continuously in orbit, or looping, in long, elliptical sweeps. Often, loopers send their yo-yos overhead, under their arms, and over their shoulders in a fashion reminiscent of jugglers.

Loopers' play demands yo-yos with characteristics different from those of the more numerous string-trick players. For example, loopers shun rim weighting. Because the yo-yo must flip at the far reach of its ellipse, extra stability is detrimental. Manufacturers sell yo-yos with extra weight toward the center for loopers to use.

Even among the string-trick players, different styles demand different instruments. Since the late 1990s, players have invented two approaches that have spread swiftly and already stand as distinct categories in national and world competitions.

In the style known as off-string, players throw a yo-yo into the air so that it completely separates from its string. Then, they use the string as both a tightrope and a trampoline for the disk. Finally, they throw a loop around the yo-yo and cinch it tightly to force the yo-yo to rewind.

In freehand style, invented by Duncan's Brown, the player end of the yo-yo string connects not to the player's hand but to a small counterweight that is heavy enough to keep the string taut yet light enough that it doesn't act as too much of a drag on the yo-yo as it gets thrown and flipped around. At the start of a trick, the string near the counterweight rests between the player's fingers, but later the player repeatedly releases and catches either the string or the counterweight.

Each style has spawned specific yo-yo designs. Both require wide gaps to make the high-flying yo-yos easy to catch on thin strings. For freehand yo-yos, Brown says, it took a lot of experimenting to discover that the best ratio of yo-yo mass to counterweight mass is 7 to 1.

Yo-yo enthusiasts say that they expect the symbiosis between yoyo designers and players to continue to drive innovation. Not-yet-invented styles of play will push manufacturers to revise their designs. Meanwhile, players will be stretching to fully exploit the expanded performance offered by the designs already available.

"It's like the training wheels are gone," says Stohr. "The kids are limited only by their own creativity".

RELATED ARTICLE: Textbook yo-yo-ology.

Labor of love elucidates spinner science and technology

Students sometimes use yo-yos to investigate physics, but almost no one ever uses physics to investigate yo-yos. That's probably because every physicist knows that yo-yos must follow Newton's laws. So who would expect anything very interesting to be learned?

Donald W. ("Captain Yo") Watson for one. He's a retired mechanical and electrical engineer who cares deeply about yo-yos. Watson is also an engineering consultant to some of the world's top yoyo inventors.

"Until very recently, most people have thought of the yo-yo as nothing more than a toy," Watson says. "I don't see it like that."

Having found technical literature on yoyos to be almost nonexistent, he has created some reports of his own. In a series of five pamphlets, the last of which he completed last October, Watson lays out his findings from what may be the most extensive studies of yo-yo physics ever conducted.

Rather than submit his work to peer-reviewed journals for publication, Watson provides his photocopied booklets of meticulously neat engineering drawings, graphs, and handwritten text to two yoyo Web sites that sell them for him (http://www.skilltoys.com/cgi-bin/commerce/index.cgi; http://www.yoyoguy.com/yoyo/bookmag/?). He says that he's sold a "couple of thousand" of the series.

Among specific results reported in the monographs: Watson derives equations for calculating yo-yo rotation rates after free fall or a hard throw; he analyzes features of yo-yo strings and investigates why yo-yos wobble; and he discovers a "yo-yo constant" that links yo-yo spin speeds to the rotational property known as the radius of gyration.

Moreover, as Watson writes at the end of the final booklet, there's another "salient principle" to be gleaned from those monographs: "Investigating yo-yo physics is fun."

Steven D. Brown, who designs yo-yos for Duncan Toys but has not collaborated directly with Watson, has studied the monographs. He finds them a "great help" in his work and rates Watson as a "hell of an engineer."

"[Watson] has certainly been part and parcel of a lot of the advancement of yoyo technology," adds Oliver.--P.W.