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The yo-yo in its simplest form is an object consisting of an axle connected to two disks, and a length of twine looped around the axle, similar to a slender spool. It is played by holding the free end of the string (usually by inserting one finger in a slip knot) allowing gravity or the force of a throw to spin the yo-yo and unwind the string (similar to how a pullstring works), then allowing the yo-yo to wind itself back to one's hand, exploiting its spin (and the associated rotational energy). This is often called "yo-yoing". First made popular in the 1920s, yo-yoing remains a popular pastime of many generations and cultures. It was first invented in ancient Greece.
In the simplest play, the string is intended to be wound on the spool by hand; The yo-yo is thrown downwards, hits the end of the string, then winds up the string toward the hand, and finally the yo-yo is grabbed, ready to be thrown again. One of the most basic tricks is called the sleeper, where the yo-yo spins at the end of the string for a noticeable amount of time before returning to the hand. Many yo-yo tricks are done while the yo-yo is said to be sleeping. One of the most famous tricks on the yo-yo is "walk the dog". This is done by throwing a strong sleeper and allowing the yo-yo to roll across the floor, before tugging it back to the hand. English historical names for the yo-yo include bandalore (from French) and quiz. French historical terms include bandalore, incroyable, de Coblenz, emigrette, and joujou de Normandie (joujou meaning little toy).
A Greek vase painting from 500 BCE shows a boy playing yo-yo (see right). Greek records from the period describe toys made out of wood, metal, or painted terra cotta (fired clay). The terra cotta disks were used to ceremonially offer the toys of youth to certain gods when a child came of age—discs of other materials were used for actual play.
Origin of name and the American yo-yo 
In the American design, one continuous piece of string, triple the desired length, is twisted around something to produce a loop at one end which is fitted around the axle. Also termed a looped slip-string, this seemingly minor modification allows for a far greater variety and sophistication of motion, thanks to increased stability and suspension of movement during free spin.
The principal distinction between the Filipino design and more primitive yo-yos is in the way the yo-yo is strung. In older (and some remaining inexpensive) yo-yo designs, the string is tied to the axle using a knot. With this technique, the yo-yo just goes back-and-forth; it returns easily, but it is impossible to make it sleep.
Birth of the modern yo-yo 
In 1928 Pedro Flores opened the Yo-yo Manufacturing Company in Santa Barbara, California. The business started with a dozen handmade toys; by November 1929, Flores was operating two additional factories in Los Angeles and Hollywood, which altogether employed 600 workers and produced 300,000 units daily.
The Duncan era 
Shortly thereafter (ca. 1929), an entrepreneur named Donald F. Duncan recognized the potential of this new fad and purchased the Flores Yo-yo Corporation and all its assets, including the Flores name, which was transferred to the new company in 1932 - the same year that the name "Yo-yo" was first registered as a trademark and Harvey Lowe won the first World Yo-Yo Contest in London, England. In 1932, Swedish Kalmartrissan yo-yos started to be manufactured as well. In 1946, the Duncan Toys Company opened a yo-yo factory in Luck, Wisconsin. The Duncan yo-yo was inducted into the National Toy Hall of Fame at The Strong in Rochester, New York, in 1999.
1960s resurgence 
In a trademark case in 1965, a federal court's appeals ruled in favor of the Royal Tops Company, determining that yo-yo had become a part of common speech and that Duncan no longer had exclusive rights to the term. As a result of the expenses incurred by this legal battle as well as other financial pressures, the Duncan family sold the company name and associated trademarks in 1968 to Flambeau, Inc, who had manufactured Duncan's plastic models since 1955. As of 2011[update], Flambeau Plastics continues to run the company.
The rise of the ball bearing 
As popularity spread through the 70's and 80's, there were a number of innovations in yo-yo technology, primarily regarding the connection between the string and the axle. In 1979, dentist and yo-yo celebrity Tom Kuhn patented the “No Jive 3-in-1” yo-yo, creating the world's first "take-apart" yo-yo, which enabled yo-yo players to change the axle.
Tom Kuhn introduced the SB-2 yo-yo that had an aluminum transaxle, making it the first successful ball-bearing yo-yo.
In all transaxle yo-yos, ball bearings significantly reduce friction when the yo-yo is spinning, enabling longer and more complex tricks. Subsequent yo-yoers used this ability to their advantage, creating new tricks that had not been possible with fixed-axle designs.
Contemporary yo-yo culture 
Yo-yo contests 
A yo-yo competition normally consists of two parts, a set of compulsory tricks and a freestyle, where points are scored for each and the winner is the yo-yo player who scores the most points. Compulsory tricks (also known as a trick ladder) are a set of tricks that have been chosen before the contest, and the competitor must successfully complete each trick on their first or second attempt to score points. The freestyle is when the yo-yo player performs a routine to their choice of music in front of a panel of judges, and is judged based on difficulty of the tricks, synchronization with the music and artistic performance.
The World Yo-Yo Contest is held every year in Orlando, Florida and is hosted by YoYoGuy.com during early August or late July. This contest takes the winners from national yo-yo contests around the world and pits them against each other. Japanese players in particular have risen to the top of the yo-yo world. The eleven-time, double-handed world champion Shinji Saito—considered the best in the world—[by whom?]is Japanese. Countries such as the United States, Brazil, Japan and the UK hold competitions at the national and regional levels. In addition, national yo-yo contests, without regionals, are held every year by Mexico, Taiwan, Singapore, Hong Kong, Korea, France, Germany, Switzerland, The Czech Republic, Hungary, and Australia.
The International Yo-Yo Open was held annually in August at South Street Seaport in New York City from 2007 to 2009, but is "on hiatus" in 2010. This contest is hosted by YoYoNation.com and aims to showcase the best yo-yo players in the world. In the inaugural 2007 contest, there were over 8,500 people in attendance and the event received almost 30 million media impressions. Besides US contests, European contests are becoming better and better. Hungary and the Czech Republic are the leaders of European yoyoing. In Prague (Czech Rep.) the european championship is held, and in Sopron(Hungary) the Sopron International Yo-Yo Contest Hosted by sleeper.hu
The TV Times world yo-yo championship was held in the United Kingdom in 1974 with heats across the United Kingdom and a final in London in 1975, the championship was sponsored by the Louis Marx toy company with the 'Lumar' brand of yo-yo. The competition was judged by a celebrity panel in each city and also Lumar demonstrator and European yo-yo champion Don Robertson. The winner of the final was Simon Harris (intermediate category). The championship was not repeated.
Contest divisions 
Currently there are nine yo-yo divisions to compete in:
- 1A-The player uses a long sleeping yo-yo to perform string tricks which usually require the manipulation of the string.
- 2A-The player uses two yo-yos simultaneously to perform reciprocating or looping tricks. This tends to be the most visually entertaining style with some players incorporating acrobatics into their routines.
- 3A-The player uses two long spinning yo-yos to perform tricks that involve manipulation of the string.
- 4A-The player uses an offstring yo-yo, often releasing the yo-yo into the air and attempting to catch it on the string.
- 5A-The player uses a yo-yo with a counterweight on the other end of the string rather than having it attached to a finger.
- AP-This is Artistic Performance where the yo-yoist uses any type of yo-yo or other prop in order to perform a freestyle.
- CB-This is the Combined Division held only at the world competition, where players have to compete and demonstrate skill in multiple styles.
- 1S-The player must perform 25 string tricks to the regulation standards and can only miss one trick.
- 2S-The player must perform 25 looping tricks to regulation standards and can only miss one trick.
Competitors usually bring a number of yo-yos to the performance stage with them to allow for mid-routine replacements in the case of knots/jams (common with string tricks), string breakage (common with looping tricks), or drops (common with offstring tricks).
2009 World Yo-Yo Contest Results for 1A 1st. Shinya Kido 2nd. Hiroyuki Suzuki 3rd. Chris Fraser
2010 World Yo-Yo Contest Results for 1A 1st. Jensen Kimmitt 2nd. Hiroyuki Suzuki 3rd. Christopher Chia
2011 World Yo-Yo Contest Results for 1A 1st. Marcus Koh 2nd. Sebastian Brock 3rd. Gentry Stein
2012 World Yo-Yo Contest Results for 1A 1st. Hiroyuki Suzuki 2nd. Marcus Koh 3rd. Christopher Chia
Yo-yo techniques 
Keeping a yo-yo spinning while remaining at the end of its uncoiled string is known as sleeping. Sleeping is the basis for nearly all yo-yo tricks other than looping, the player first putting the yo-yo in a "sleep" before throwing the yo-yo around using its string. Most modern yo-yos have a transaxle or ball bearing to assist this, but if it is a fixed axle yo-yo, the tension must be loose enough to allow this. The two main ways to do this are (1), allow the yo-yo to sit at the bottom of the string to unwind, or (2) perform lariat or UFO to loosen the tension
In competition, mastery of sleeping is the basis for the 1A division. Inexpensive fixed-axle yo-yos usually spin between 10–20 seconds, while expensive ball bearing yo-yos can spin about 1–4 minutes depending on the throw  As of 2010[update], the world record sleep times were 3m51.540s for fixed-axle and 21m15.170s for transaxle yo-yos.
Looping is a yo-yo technique which emphasizes keeping the body of the yo-yo in constant motion, without sleeping.
Yo-yos optimized for looping have weight concentrated in their centers so they may easily rotate about the string's axis without their mass contributing to a resistance due to a gyroscopic effect.
In yo-yo competitions, looping plays a strong role in the 2A division. Looping both to the inside and outside of the hand with the yo-yo.
In the "off-string" technique, the yo-yo's string is not tied directly to the yo-yo's axle, and the yo-yo is usually launched into the air by performing a "forward pass" to be caught again on the string. However, some players can 'throw down' off-string yo-yos and catch it on the string just as it leaves the end of the string by pivoting the string around a finger as it unwinds, so that the yo-yo is caught on the string. This is exactly the opposite of a "forward pass", but with the same result.
Yo-yos optimized for off-string tricks have flared designs, like the butterfly shape, which makes it easier to land on the string, and often have soft rubber rings on the edges, so minimum damage is inflicted on the yo-yo, the player, or anyone who happens to be standing nearby, should a trick go wrong.
Yo-yo competitions have the 4A division for off-string tricks.
In freehand (5A) tricks, the yo-yo's string is not tied to the player's hand, instead ending in a counterweight. The counterweight is then thrown from hand to hand and used as an additional element in the trick.
Developed in 1999 by Steve Brown, as of 2008 freehand is considered to be the fastest-growing style of yo-yo play. Steve Brown was awarded a patent on his freehand yo-yo system, which was assigned to Flambeau Products (Duncan's parent company).
In yo-yo competitions, counterweight yo-yos are emphasized in the 5A division.
Yo-yo shapes 
Yo-yo bodies come in a number of form factors or "silhouettes," each designed with specific advantages in mind. However, there are three popular configurations.
The modified shape is a very popular design for looping style tricks. This shape is also known as a flywheel or modern shape. It usually has a hollowed face (sometimes covered with paper or plastic) with extra material left in the rim. The modified shape yo-yo is also used for string tricks because of the long spin times due to its shape.
Duncan released its first wooden butterfly yo-yo. Wayne Lundberg, the inventor, was one of the demonstrators. The butterfly looks a bit like the separated halves of a standard yo-yo that have been reconnected back-to-back. The wider string gap to make it easier to catch the yo-yo body on the string. Although the butterfly shape is good for 'string tricks,' it is not good for 'looping' tricks, because the winged shape of the body does not allow it to easily flip while looping. This shape is similar to a small Diabolo, sometimes called a Chinese yo-yo.
Newer shapes 
Introduced to the "yo-yoing community" only within the past few years, many yo-yos are being produced with wide-gaps, H-shapes, and dimples. Wide-gap yo-yos are not exclusive to any one yo-yo manufacturer and as their name suggests, have a wider gap. The wide gap allows more layers of string to be stacked in the yo-yo, and tricks using string slack or lacerations. The drawback for this shape is that the yo-yo does not return to the player's hand unless bound through the use of a front or under mount. H-shaped yo-yos are much like the butterfly-shaped, but the center (toward the bearing/axle) is offset to a smaller diameter to add to circumferential weight and allow for easy "grinding" tricks. Utilizing the technology of a golf ball, dimples are found in Roo-Yo (Italian yo-yo manufacturer) yo-yos and reduce air friction.
Other shapes 
There are, of course, many other shapes. Other less popular shapes are: Humphrey, Ball, Slimline, Russell Style (Bulge Face), Puck, Satellite, Coaster and Riveted Disk.
Weight distribution 
Each silhouette may have more weight distributed at either the center of the yo-yo or the edge. More weight towards the rim will make the yo-yo more stable for string tricks; more weight towards the center will make the yo-yo easier to turn and therefore better for looping tricks.
Heavier yo-yos will have more angular momentum when spinning at a given speed, and thus will spin freely for a longer period.
Most modern yo-yos are made from a "take-apart" design, designed to be taken easily apart and reassembled by the player. This design was first created by Tom Kuhn. This enables the replacement of yo-yo components, including the string, renewable friction sources, or even trans-axle components.
In order to increase spin times, extra weight was added to the outermost portion of the yo-yo. The first to do this was Dale Oliver (Spintastics Skill Toys, Inc) with the addition of steel rings when he brought out the Tigershark yo-yo early in 1998.
Some take-apart designs allow the player to reconfigure the yo-yo's halves. In the Tom Kuhn No Jive 3-In-1, the halves may be attached in three different configurations, resulting in a traditional, butterfly, or "pagoda" silhouette. In the Yo-yo Factory FlyMaster, the body has two different "shells" to convert to and from an off-string yo-yo.
Another innovation to the yo-yo is the ability to adjust the gap between the two halves of the yo-yo, in order to increase or decrease response. In most designs, this is accomplished by twisting the yo-yo halves, but some designs (such as the Tom Kuhn Silver Bullet) can be disassembled for adjustment without twisting. This second option eliminates the possibility of the yo-yo coming out of adjustment during play.
- John Jerome McAvoy, Jr. was awarded patents for the gap-adjustable yo-yo: patent #5389029 on February 14, 1995, and #6066024 on May 23, 2000.
- In 1998, HSPIN launched the Handquake series of yo-yos, which sported an adjustable gap by using shims of 0.1-0.5mm thickness. By adding or removing shims, the gap could be widened or shrunk by +/- 1mm.
- Harry Baier (creator of the "Mondial" yo-yo) and the Flambeau Products Company (owner of Duncan) were awarded patent #6162109 on December 19, 2000 for a gap-adjustable yo-yo which has discrete positions for specific gap widths. This patent was first implemented in the CameYo Mondial before being bought by Duncan.
- YoYoFactory's productline of Speed Dial yo-yo's feature "Fully Adjustable Starburst Technology" which allow the gap to be adjusted using a dial on the yo-yo. This allows for a more discrete response setting that stays the same after the yo-yo is taken apart and put back together.
Axle/bearing differentiation 
The basic innovation since the 1990s is the transaxle, a system where the string is not directly connected to the axle that connects the two halves of the yo-yo.
- Fixed axle yo-yos are represented by the original yo-yo design popularized in the first half of the 20th century, where the axle is directly connected to the string and halves of the yo-yo body. In order to enable the throwing of a "sleeper", the player must ensure the string is not wound too tightly around the axle, because it must freely spin in order to accomplish this move. Yo-yos designed for "looping" tricks tend to be fixed-axle yo-yos.
- Some more exotic fixed-axle yo-yos have axles made from low-friction materials such as ceramic alloys—this allows for easier "sleeping," which is essential for string tricks.
- The majority of trick yo-yos sold are Bearing transaxle yo-yos. In these transaxle yo-yos the string is not connected to the axle directly, but rather it is wrapped about a ballrace bearing. The bearing, in turn, surrounds the true axle of the yo-yo. In this way, the body of the yo-yo may spin freely about the string's point of contact.
- There are transaxle systems which do not use a ball bearing, such as the Duncan ProFire and Yomega Fireball. These use a low-friction metal or plastic collar around the axle.
- The clutch transaxle, innovated by Yomega with the Yomega Brain, is a transaxle that can be engaged or disengaged.
- the Yomega Brain is a centrifugal clutch transaxle-- when spinning at a sufficiently high speed, counterweights inside the yo-yo body disengage the axle, automatically allowing the yo-yo to "sleep." Conversely, when the speed slows below the threshold, the yo-yo will return automatically.
- Other clutch transaxles feature a manual switch which can engage or disengage the axle.
Hubstacks are bearings added to the hub (the outside) of a yo-yo and covered with some form of side cap to allow it to be held while it spins. With the side cap bearing you can hold the yo-yo in many different planes and perform different styles of tricks which are difficult, or impossible in some cases, to be performed with conventional yo-yos. These may be called Hubstacks, bearing caps, synergy caps, or jimmy hats.
Physical mechanism 
When the yo-yo is first released, the throw gives it translational kinetic energy. As the string unwinds, much of this energy is converted into rotational kinetic energy, causing the yo-yo to spin rapidly. As the yo-yo unwinds, it also gains some energy from gravity. Because the yo-yo has a significant rotational inertia, the yo-yo can store enough energy in its rotation allow it to fight gravity all the way back up to your hand. The string winds in the opposite direction upon the return of the yo-yo. If the string is connected to the shaft with a loop, there may not be enough friction to overcome gravity, and begin winding the string. In this case, the yo-yo will continue to spin at the end of the string instead of returning. However, if the yo-yo is jerked slightly, it will enter free fall for a brief moment, and the string's friction becomes the most significant force on the yo-yo. This allows the slack string to bind, and the energy from the yo-yo's rotation finishes the rest of the return.
See also 
- Easy Yo-Yo Tricks, Editors of Publications International, Ltd., howstuffworks.com
^ Advanced Yo-Yo Tricks for Kids, Editors of Publications International, Ltd., howstuffworks.com
- "National Yo-Yo Museum, California". Nationalyoyo.org. Archived from the original on May 13, 2008. Retrieved 2010-01-17.
- Miller, Stephen G. (2004). Ancient Greek Athletics. Yale University Press. pp. 169–. ISBN 9780300115291. Retrieved 19 March 2013.
- Pedro Flores, National Yo-Yo Museum, archived from the original on January 20, 2008, retrieved 2008-02-18
- Online Etymology Dictionary. Etymonline.com. Retrieved on 2012-04-09.
- Hopkins, Michelle (2009-04-19). "'Great ambassador' passes away". Richmond News. Retrieved 2009-04-12.
- "Kalmartrissan snurrar vidare", Dagens Nyheter 19 December 2012 (not available in the on-line edition) (Swedish)
- Kalmartrissan fyller 70 år, Sveriges radio, 25 January 2002, retrieved 22 March 2013 (Swedish)
- Classic Toys: The Yo-Yo. Retro Planet (2009-05-12). Retrieved on 2012-04-09.
- By admin (2010-04-27). "Home of the National Yo-Yo Contest, National Yo-Yo Museum and National Yo-Yo League". National Yo-Yo. Retrieved 2011-05-23.
- Tzeng, Grace. "Toy Story: Gravity-defying yo-yo tricks on display at California State Yo-Yo Championships". AsianWeek. Retrieved on 8 September 2008.
- Yo-Yo Basics, howstuffworks.com.
- American Yo-Yo Association website.
- Science News, Week of April 17, 2004; Vol. 165, No. 16, p. 250[dead link]
- Team Offstring Superheroes, October 17, 2008.
- Lucky's Collectors Guide to 20th Century Yo-Yos, 1999
- U.S. Patent 6,066,024 Filed August 4, 1998; Issued May 23, 2000
- U.S. Patent 5,389,029 Filed April 27, 1993; Issued February 14, 1995
- U.S. Patent 6,162,109 Filed October 29, 1999; Issued December 19, 2000
- www.YoYoSkills.com/hans-interview.html - Interview with Hans Van Dan Elzen, YoYoFactory
- U.S. Patent 6,331,132 Filed July 27, 1999; Issued December 18, 2001
- U.S. Patent 7,192,330 Filed October 29, 1999; Issued December 19, 2000