 A chain-drive bicycle with a internal-geared multi-speed rear hub  In this simple epicyclic gear mechanism, the inner gear or "sun gear" (green) provides the input rotation. The two "planet gears" (blue) rotate freely about the planet gear carrier (yellow) which is fixed. As the planet gears rotate about the sun gear, they propel the outer ring gear or "annulus" (red), which provides the output rotation  14-speed hub cutaway diagram
Hub gears or internal-gear hubs are a type of gear system used on bicycles. Hub gears are used mostly on utility bikes and various types of small wheeled bicycle, such as folding bikes. Hub gears work by internal planetary or epicyclic gearing, which means that the outer case of the hub gear unit (which is attached to the spokes) is made to turn at a different speed relative to the rear wheel's sprocket depending on which gear is selected.
In the United States and United Kingdom, hub gears are less common than derailleur gears which are the dominant gear system on most modern bicycles in these countries. In most of continental Europe, however, hub gear systems are more popular. For example, Vélib' and Vélo'v, the public bicycle rental programmes in Paris and Lyon, use bikes with 3-speed hub gears. Unlike derailleur gears, where the gears and mechanism are exposed to the elements, hub gears and lubricants are sealed within the hub of the bicycle's rear wheel. Gears are changed by a cable which is tightened or loosened by a lever or twist grip on the handlebars. [edit] History Prior to using epicyclic gears in hubs of bicycles they were used on various locations of tricycles, there are a number of patents dating from the early 1880s.[1]
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.[2]. This was a 2-speed but was not commercially successful. In 1896 William Reilly of Salford, England patented a broadly similar 2-speed hub which went into production in 1898 as 'The Hub'.[3] 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.[4] Meanwhile, well-known English journalist and inventor Henry Sturmey had also invented a 3-speed hub.[5] In 1903 Frank Bowden, head of the Raleigh cycle 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.[6] 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[7] but was arguably an unusual epicyclic gear, in which a second sun was used in place of an annulus.[8] By 1909 there were 14 different 3-speed hub gears on the British market.[9] In 1904 the Fichtel & Sachs (Germany, Schweinfurt) produced a hub gear under license to Wanderer. 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. Where they have become less popular it is because modern derailleur gears offer indexed shifting, a wider gear range and a more fashionable image for a lower price. 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.[10] Since then there has been a small but steady increase in interest in hub gears, reflected in the wider range of products now available. In 2008, Sturmey-Archer make 3-, 5- and 8-speed hubs, SRAM (successor to Fichtel & Sachs) make 3-, 5-, 7- and 9-speeds, Shimano make 3-, 7- and 8-speeds, Rohloff make 14-speed hubs and NuVinci make ∞-speed (CVT) hubs. Though most hub gear systems use one rear sprocket, SRAM's DualDrive system combines an epicyclic hub with a multi-speed rear derailleur system to provide a wide-ranging drivetrain concentrated at the rear wheel. Brompton Bicycle have their own design, with a two-speed derailleur coupled to a three-speed SRAM hub gear. 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. [edit] Advantages - Because the mechanism is sealed within the hub and bathed in lubricant it is not exposed to dirt or weather. Consequently, hub gears need less maintenance than derailleur gears, and are more reliable, making them suitable for utility bicycles.
- Internal hub gears are far less susceptible to impact damage in use or when the bicycle is being shipped.
- The gear can be shifted when the bike is stationary; derailleurs need the chain to be moving, which takes some trouble if the bike has stopped while in a high gear.
- Shifting is smoother than in external rear derailleurs.
- As the chain does not move sideways, it can be covered with a chain guard or even fully enclosed, protecting the rider's clothing from grease and damage, useful for utility cycling. A fully encased chain will maintain clean lubrication and last much longer than if exposed.
- The rear wheel spokes are symmetric on both sides of the bike. Symmetric spokes more evenly distribute load across the rear wheel and are an advantage where wheel loadings are high as in utility or touring bicycles.
- Hub gears have a single range of gears without overlap; for example a 14-speed hub gear has a high-to-low range of about 5 to 1, while a 24-speed derailleur system has 3 overlapping ranges with about the same total range but only some 16 to 19 distinct gears and a more complicated gear-shifting pattern.
[edit] Disadvantages - Hub gears offering a wide range of ratios are very expensive, costing more than a frame and fork of reasonable quality.
- Some, especially those with a high number of speeds, are less efficient than derailleur systems, although derailleurs become less efficient when dirty and worn. A simple 3-speed hub when run-in and properly lubricated can match or exceed derailleur efficiency, benefiting from the lack of the derailleur's jockey wheels and from its perfect chainline.
- They are heavier than a derailleur system, also concentrating the weight towards the rear of the bicycle. The greater unsprung weight is also disadvantageous for a full suspension bicycle.
- They are considerably more difficult to repair than derailleur gears, where every component is accessible. Spares availability can, however, be very good as the difficulty of rebuilding the rear wheel, and the cost of a new hub, can make repair rather than replacement an attractive option.
- With 3 or 5-speed hubs there is usually quite a big jump from one gear to the next. Sturmey-Archer once made medium- and close-ratio 3 and 4 speed gears for racing, but these have been out of production since the 1960s.
[edit] See also [edit] Manufacturers [edit] References - ^ Berto, Frank; Tony Hadland, Jan Heine, Raymond Henry, Gordon Selby, Ron Shepherd, Walter Ulreich (2009). The Dancing Chain : history and development of the derailleur bicycle, Third Edition. San Francisco, CA, USA: Van der Plas Publications/Cycle Publications. pp. 34. ISBN 1892495414. http://www.cyclepublishing.com/cyclingbooks/dc.html.
- ^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.18-19
- ^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.19-22
- ^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.26-29
- ^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.31-34
- ^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.35-38
- ^ Evans, David E. The Ingenious Mr Pedersen, Alan Sutton, Stroud, 1992, p.49
- ^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.65
- ^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987, pp.67-68
- ^ Hadland, Tony, The Sturmey-Archer Story, Pinkerton Press, Birmingham, 1987.
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