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A hub gear, internal-gear hub,〔 or just gear hub is a gear ratio changing system commonly used on bicycles that is implemented with planetary or epicyclic gears. The gears and lubricants are sealed within the shell of the hub gear, in contrast with derailleur gears where the gears and mechanism are exposed to the elements. Changing the gear ratio was traditionally accomplished by a shift lever connected to the hub with a Bowden cable, and twist-grip style shifters have become common. Hub gear systems generally have a long and largely maintenance-free life though some are not suitable for high-stress use in competitions or hilly, off-road conditions. Many commuter or urban cycles such as European city bikes are now commonly fitted with 7-speed gear-hubs and 8-speed systems are becoming increasingly available. Older or less costly utility bicycles often use 3-speed gear-hubs, such as in bicycle sharing systems. Many folding bicycles use 3-speed gear-hubs. Modern developments with up to 14 gear ratios are available. ==History== Before epicyclic gears were used in bicycle hubs, they were used on tricycles. Patents for epicyclic hubs date from the mid-1880s. The first patent for a compact epicyclic hub gear was granted in 1895 to the American machinist Seward Thomas Johnson of Noblesville, Indiana, U.S.A.〔Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987, pp.18-19〕 This was a 2-speed but was not commercially successful. In 1896 William Reilly of Salford, England patented a 2-speed hub which went into production in 1898 as 'The Hub'.〔Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987, pp.19-22〕 It was a great success, remaining in production for a decade. It rapidly established the practicality of compact epicyclic hub gears. By 1902 Reilly had designed a 3-speed hub gear. He parted company with the manufacturer of 'The Hub' but had signed away to them the intellectual rights to his future gear designs. To circumvent this problem, the patents for Reilly's 3-speed were obtained in the name of his colleague, James Archer.〔Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987, pp.26-29〕 Meanwhile, well-known English journalist and inventor Henry Sturmey had also invented a 3-speed hub.〔Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987, pp.31-34〕 In 1903 Frank Bowden, head of the Raleigh Bicycle Company, formed The Three-Speed Gear Syndicate, having obtained the rights to both the Reilly/Archer and Sturmey 3-speeds. Reilly's hub went into production as the first Sturmey Archer 3-speed.〔Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987, pp.35-38〕 In 1902 Mikael Pedersen (who also produced the Dursley Pedersen bicycle) patented a 3-speed hub gear and this was produced in 1903. This was said to be based on the "counter shaft" principle〔Evans, David E. ''The Ingenious Mr Pedersen'', Alan Sutton, Stroud, 1992, p.49〕 but was arguably an unusual epicyclic gear, in which a second sun was used in place of a ring gear.〔Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987, pp.65〕 In 1904 the Fichtel & Sachs company (Germany, Schweinfurt) produced a hub gear under license to Wanderer, and by 1909 there were 14 different 3-speed hub gears on the British market.〔Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987, pp.67-68〕 By the 1930s hub gears were used on bicycles all over the world. They were particularly popular in the UK, The Netherlands, the German-speaking countries and Scandinavia. Since the 1970s, they have become much less common in the English-speaking countries. But in many parts of northern Europe, where bicycles are regularly used as daily transport rather than merely for sport or leisure, hub gears are still widely used. The cheaper and stronger (but less reliable) derailleur system now started to appear and offer a wider gear range. By 1987 Sturmey-Archer made only 3- and 5-speed hubs, and Fichtel & Sachs and Shimano made only 2- and 3-speed hubs. In that year the first book (apart from service manuals) for some 80 years dealing solely with epicyclic bicycle gears was published.〔Hadland, Tony, ''The Sturmey-Archer Story'', Pinkerton Press, Birmingham, 1987.〕 Since then there has been a slow but steady increase in interest in hub gears, reflected in the wider range of products now available. In 1995 Sachs introduced the Elan, the first hub gear with 12 speeds, and an overall range of 339%. Three years later Rohloff came out with the Speedhub 500/14, a gear hub with 14 speeds and a range of 526%, comparable to that of a 27 speed derailleur gear system, and also sufficiently robust and lightweight for mountain biking. In 2007 NuVinci started manufacturing continuously variable transmission ("stepless") ∞-speed hubs for commuter bicycles, with a range of about 350%. As of 2008, Sturmey-Archer makes 3-, 5- and 8-speed hubs, SRAM (successor to Fichtel & Sachs) make 3-, 5-, 7- and 9-speeds and Shimano make 3-, 7- and 8-speeds. In February 2010 Shimano announced the introduction of the Shimano Alfine 700, an 11-speed model. Though most hub gear systems use one rear sprocket, SRAM's Dual Drive system combines an epicyclic hub with a multi-speed rear derailleur system to provide a wide-ranging drivetrain concentrated at the rear wheel. In 2010 Canyon introduced the 1442, a hybrid hub which uses a similar epicyclical/derailleur combination. Brompton Bicycle have their own design, with a two-speed derailleur coupled to a special three-speed wide-ratio Sturmey-Archer hub, the "BWR" (Brompton Wide Ratio). The system is useful for folding bicycles (where a multiple front chainset could foul the bike's folding mechanism) and in recumbent bicycles and freight bicycles (where small wheels and/or increased weight require a wider range of gears with smaller steps). Hub gears have in the past also been used on motorcycles, although this is now rare. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hub gear」の詳細全文を読む スポンサード リンク
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