A hub gear,[1]internal-gear hub,[2]internally geared hub[3] or just gear hub[4] 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 18 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.[5][6] 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.[7] 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'.[8] 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.[9] Meanwhile, well-known English journalist and inventor Henry Sturmey had also invented a 3-speed hub.[10] 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.[11]
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[12] but was arguably an unusual epicyclic gear, in which a second sun was used in place of a ring gear.[13] 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.[14]
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 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 systems, which offer a wider gear range, have now started to appear.
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.[15] Since then, there has been a slow but steady increase in interest in hub gears, reflected in the wider range of products now available.
early NuVinci hubNuVinci internals
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 an increasing range of about 380%[16] (2016).
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.[17]
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 presented the 1.442-concept, a hybrid hub which uses a similar epicyclical/derailleur combination.[18]
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), in recumbent bicycles, and cargo bikes (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.
Principle of operation
Epicyclic gears as implemented in common bicycle 3-speed gear hubs: the sun gear (yellow) is fixed, the sprocket drives either the ring gear (red) or the planet cage (green), and the hub is driven by either the ring gear (red) or the planet cage (green), depending on the gear selected.
The simplest 3-speed hubs use a single planetary epicyclic gearset. The sun gear (in yellow) is mounted solidly to the axle and is thus fixed relative to the bicycle frame.
In low gear, the sprocket drives the annulus (in red), and the planet carrier (in green) drives the hub, giving a gear reduction.
In middle gear, the sprocket drives the hub directly.
In high gear, the sprocket drives the planet carrier (in green), and the annulus (in red) drives the hub, resulting in a gear increase.
The hub axle of a hub gear (unlike that of a derailleur system) will carry torque in all gears except direct drive, and so must be securely braced against rotation. While anti-rotation washers between the dropout and axle nut have often proved adequate, wider-ranging modern systems use a reaction arm affixed to the chain stay. Rear wheels with drum brakes (a feature on some commuter bicycles) require a reaction arm anyway.
Most hub gears are operated in a similar manner, with a single twist, trigger or thumb-shifter. An exception is the older style of Sturmey-Archer 5-speed, which used a second shift cable to change between close and wide-range sun gears, effectively giving two 3-speed hubs in one unit. The middle gear in both ranges was direct drive, so there were five distinct gears. They could either be controlled with a special 5-speed shifter which operated both cables, or with a regular 3-speed shifter and a friction shifter.
Advantages
Hub gears are sealed within the hub, which protects them from water, grit, and impacts. Thus hub gears usually require less maintenance and can be more reliable over time than comparable external derailleur gear systems, which may require more adjustments and replacement of parts (front chainrings, rear sprockets, narrow derailleur-chain).
Hub gears completely avoid the danger of collision with the spokes and wheel-collapse that derailleur systems can suffer.
Hub gears can change gear ratios when the rear wheel is not rotating. This can be useful for commuter cycling with frequent stops and for mountain biking in rough terrain.
Hub gears can be simpler to use for inexperienced riders, because there is generally only a single shifter to operate and there are no overlapping gear ratios. By contrast, modern derailleur systems often have two shifters, and require some forethought to avoid problematic gear combinations.
Hub gears can be manufactured to include a coaster brake (though not all hub gears are available with coaster brakes). This is not possible with derailleur systems, because the chain cannot transmit a backwards pull.
Hub gears provide a means for shifting gear ratios on drivetrains incompatible with external derailleurs such as belt drives and shaft drives.
The single chainline allows for a full chain enclosure chain guard, so the chain can be protected from water and grit, and clothing can be protected from contact with the lubricated chain.
The single chainline does not require the chain to bend or twist. As a result, the chain can be constructed differently, with parallel pins instead of barrel-shaped ones.[19] Line-contact between the bearing surfaces, instead of the point-contact of a derailleur chain, greatly extends the working life of all components.[citation needed]
On bicycles with fixed chain-lines, no chain tensioner is required, eliminating a part that could otherwise become damaged in rough terrain- an advantage for off-road cyclists. Where a tensioner is required, a short cage is usually sufficient to take up the chain slack.
The single external sprocket means that the wheel can have a hub with more distance between its flanges and be built with no or much less dish, making it laterally stronger than a similar wheel with narrower flange spacing and more dish to accommodate multiple sprockets.[20] The hub shell of gear hubs is also often of a larger diameter than that of derailleur hubs, meaning the spokes on such wheels may be shorter.[20]
Disadvantages
It can be hard or impossible to select another gear whilst pedalling, because a release of pressure is required to enable a change in this case.
The rear wheel cannot be completely separated from a bicycle with hub gears without also disconnecting the gear cable (and any coaster-brake clamp), which complicates the process of replacing an inner tube (of course, one can still patch an innertube without removing a wheel).
The hub gear is an integral part of the wheel and it is not possible to change the wheel without also changing the hub gear.
Hub gears are more complex and usually more difficult for the rider to repair, which is nearly impossible by the roadside.[4]
Hub gears are typically more expensive than derailleur systems (note: it depends on what you are comparing them with).
At commuter/recreational power levels, current hub gears are typically about 10% less efficient than reasonably maintained derailleur gears.[21][22] (note: some marketing material from tests performed by the manufacturers has the number at 2%, but that is not only false, but impossible. Several tests compared a new internal gear hub with an old and badly-maintained derailleur system, or did not apply any weight on the axle and load into the system. The real numbers are different - the efficiency/losses are closer to that of all planetary gear transmissions.)
Hub gears tend to be heavier than derailleur systems with equivalent gearing characteristics, and the additional weight is concentrated at the back wheel. For this reason, they are not a primary choice for rear-suspension bicycles in sporting use as the extra unsprung weight may adversely affect traction and braking.
Hub gears are generally incompatible with quick release mechanisms/skewer axles.[2]
It is sometimes possible to select no gear when changing gears with a poorly adjusted gear cable, which results in a complete loss of drive.[citation needed]
Hub gears in everyday use
Traditional hub gears are indexed at the shifter, making operation dependent on correct cable tension (and lubrication thereof). In practice, gear-jumping and consequent internal damage are unusual, except in high-mileage units. Modern hub gear-units incorporate the indexing within the unit and are, therefore, unaffected by shifting malfunctions caused in this way.
Most Sturmey-Archer and Fichtel & Sachs "Torpedo" systems default to top gear at slack-cable, which could make the bicycle usable for long-distance travel in flat terrain, even if a fault developed in the change mechanism. It is rather like a derailleur system, which can be manually set to a high gear in case of a similar fault. The very earliest Sturmey-Archer hubs, however, defaulted to low gear. Some modern hub gear systems, e.g., 7-speed Shimano, also default to bottom gear and are thus more dependent on the cable-pull.
Hybrid gearing with derailleurs
Some systems combine internally geared hubs with external derailleurs. A freewheeling hub with a sprocket suitable for narrow chain can be combined with a double or triple crankset and front derailleur, in order to provide a wider range and closer gear ratio spacing. A chain tensioner or a rear derailleur is needed to take up chain slack, and care is needed not to over-torque the hub by using too small a chainring/sprocket ratio.
Alternatively, some hubs can accept two dished drive sprockets,[23] between which the rider can switch with a rear derailleur. Careful sprocket selection can allow the available gear ratios when using one sprocket to fall half-way between those available when using the second sprocket, providing half-step gearing, as on the Brompton 6-speed folding bicycle. This concept is used and extended in the SRAM Dual Drive system, where a conventional multi-speed cassette is mounted to a 3-speed hub. A similar version of the ever-popular AW hub is manufactured by Sturmey Archer. This system may be useful on bicycles which cannot accept a front derailleur. The German company Canyon introduced the 1442 in 2010, a hybrid hub which uses a similar epicyclical/derailleur combination.
When both front and rear derailleurs are used with a geared hub, the result is a very wide-ranging drivetrain, at the expense of increased weight and complexity.
A particular use of the dualdrive systems is on recumbent bicycles where starting off from a standstill, or after braking hard, is very difficult if a high gear is engaged. On an upright bicycle, if a high gear is engaged, the rider may use one leg to gain minimal momentum and stand on the pedals and use her/his upper body to balance the bike; this is not possible on a 2-wheeled recumbent bicycle. Here the dualdrive setup allows shifting at a standstill or at low speeds, which is not possible with derailleur gears alone.
Advanced hub gears
Advanced hub gears offer a higher number of gears by using multiple epicyclic gears driven by each other. Their ratios are chosen to give more evenly spaced gears and a larger total gear range. The operating principle of such units is the same as with less advanced systems, with a trigger or twist shifter with sequential shifting.
The 12-speed Sachs Elan was the first hub gear with 10 or more speeds in the market (1995–1999). It was considered heavy and plagued with quality issues, and was discontinued after a few years.
The 14-speed Rohloff Speedhub hub gear, introduced in 1998, has a range exceeding 5 to 1, and is thus comparable in range to 24, 27 and 30-speed derailleur systems (with 3×8, 3×9 and 3×10 cogs front and rear), since the latter have three overlapping ranges often with only about 14 distinct gears. As there is no overlap with the Speedhub, the hub gear has only two shift directions (up and down), compared to front and rear derailleur gears where two shift operators with two shift directions are needed to shift through all gears.
The 11-speed Shimano Alfine 700 hub gear, introduced in 2010, has a gear range exceeding 4 to 1, comparable to 20-speed derailleur drive-trains, and internals running in an oil bath, for greater mechanical efficiency.
Gallery
A Sturmey-Archer AM bicycle hub gear mechanism with the ring gear removed to show the compound (stepped) planet gears.
Traditional 3-speed thumb-lever shifter, this is a Sturmey Archer shifter made between 1967 and 1975, it is missing its clear plastic applique which displays the gear selected and the manufacturer's branding.
A modern SRAM Spectro S7 twist-style seven-speed indexed shifter uses the same bowden cable as the older lever.
Cross-sectional diagram of an Eadie two-speed coaster-brake gear hub.
Disassembled tricoaster gear/brake hub. The sun gear is attached to the middle of the axle which lies across the top center, the four planet gears are arranged in a square to the right of the center, and the ring gear is to the upper right of them.
Exploded view of a Sturmey Archer three-speed gear hub.
A derailleur is a variable-ratio bicycle gearing system consisting of a chain, multiple sprockets of different sizes, and a mechanism to move the chain from one sprocket to another.
A bicycle chain is a roller chain that transfers power from the pedals to the drive-wheel of a bicycle, thus propelling it. Most bicycle chains are made from plain carbon or alloy steel, but some are nickel-plated to prevent rust, or simply for aesthetics.
Sturmey-Archer was a manufacturing company originally from Nottingham, England. It primarily produced bicycle hub gears, brakes and a great many other sundry bicycle components, most prominently during its heyday as a subsidiary of the Raleigh Bicycle Company. In the past, it also manufactured motorcycle hubs, gearboxes and engines.
A single-speed bicycle is a type of bicycle with a single gear ratio. These bicycles are without derailleur gears, hub gearing or other methods for varying the gear ratio of the bicycle.
A fixed-gear bicycle is a bicycle that has a drivetrain with no freewheel mechanism such that the pedals always will spin together with the rear wheel. The freewheel was developed early in the history of bicycle design but the fixed-gear bicycle remained the standard track racing design. More recently the "fixie" has become a popular alternative among mainly urban cyclists, offering the advantage of simplicity compared with the standard multi-geared bicycle.
A shaft-driven bicycle is a bicycle that uses a drive shaft instead of a chain to transmit power from the pedals to the wheel. Shaft drives were introduced in the 1880s, but were mostly supplanted by chain-driven bicycles due to the gear ranges possible with sprockets and derailleurs. Around the 2000s, due to advancements in internal gear technology, a small number of modern shaft-driven bicycles have been introduced.
SR Suntour is a Taiwanese manufacturer of bicycle components, formed in 1988 when Osaka based SunTour (Maeda) went bankrupt and was purchased by Sakae Ringyo Company, a major Japanese maker of aluminum parts, particularly cranks and seat posts. SunTour's sales and commercial success peaked from the late 1970s to the mid-1980s.
On a bicycle, the cassette or cluster is the set of multiple sprockets that attaches to the hub on the rear wheel. A cogset works with a rear derailleur to provide multiple gear ratios to the rider. Cassettes come in two varieties, freewheels or cassettes, of which cassettes are a newer development. Although cassettes and freewheels perform the same function and look almost the same when installed, they have important mechanical differences and are not interchangeable.
A freehub is a type of bicycle hub that incorporates a ratcheting mechanism.
The Rohloff Speedhub is an epicyclic internal hub gear for bicycles, developed and patented by Rohloff AG. It has been manufactured and marketed by that company since 1998. The Speedhub 500/14 has 14 equally spaced, sequential, non-overlapping gear ratios operated by a single twistgrip. The overall gear range is 526%, meaning the highest gear is 5.26 times as high as the lowest gear. Individual gear shifts when shifting up give an increase of about 13.6%.
A front freewheel or freewheel crank is a freewheel mechanism used on some bicycles which enables the drivetrain of the bicycle to continue spinning while the rider rolls, but stops pedaling, or coasts. Unlike regular bicycles, a front freewheel can make it possible to shift gears using a derailleur while the rider is coasting if paired with a fixed rear hub or a freehub with a slight resistance in the freewheel mechanism, which causes the chain to continue spinning with the wheel rotation.
Bicycle gearing is the aspect of a bicycle drivetrain that determines the relation between the cadence, the rate at which the rider pedals, and the rate at which the drive wheel turns.
Hyperglide is the name given by cycling component manufacturer Shimano to a sprocket design in their bicycle derailleur tooth cassette systems. It varies gear tooth profiles, and/or pins along the faces of freewheel or cassette sprockets, or between the chainrings in a crankset, to ease shifting between them.
A belt-driven bicycle is a chainless bicycle that uses a flexible belt, typically a synchronous toothed design, in order to transmit power from the pedals to the wheel.
An electronic gear-shifting system is a method of changing gears on a bicycle, which enables riders to shift with electronic switches instead of using conventional control levers and mechanical cables. The switches are connected by wire or wirelessly to a battery pack and to a small electric motor that drives the derailleur, switching the chain from cog to cog. An electronic system can switch gears faster and, because the system does not use Bowden cables and can calibrate itself, it may require less maintenance.
Bicycle drivetrain systems are used to transmit power on bicycles, tricycles, quadracycles, unicycles, or other human-powered vehicles from the riders to the drive wheels. Most also include some type of a mechanism to convert speed and torque via gear ratios.
Shimano Nexus is a brand of bicycle components which includes products such as epicyclical gear hubs, cranksets, shifters, brake levers, hub brakes, hub dynamos, and a CPU for automatically changing gears. The series is primarily aimed at the "comfort" market such as urban commuters and tourers, and as such is not made to withstand the rigours of off-road or mountain biking. The free-wheeling Nexus internal gear hubs are compatible with Shimano's "roller brake", its version of a drum brake, but not with the Shimano disc brakes used with the higher-end Shimano Alfine internal gear hubs.
The SRAM i-Motion series of products is a sport, urban, and trekking oriented product series developed and manufactured by SRAM Corporation. Branded i-Motion are internally geared hubs, shift levers, and dynamo hubs. Related to the i-Motion series are also changeable free or fixed single speed hubs, hybrid epicyclic and derailleur gear hubs, and hydraulic disc brakes. The i-Motion series of products were developed at SRAMs Schweinfurt R&D and manufacturing plant in Germany, formerly of Sachs.
A gearbox bicycle is a bicycle that uses a gearbox to convert torque and rotational speed from the power source, usually the rider's legs, to what is desired at the drive wheel. The gearbox is usually incorporated into the frame near the crank, and it may be used in addition to or instead of derailleur gears or a hub gear. Cited advantages include improved shifting performance, protecting the gearing from damage and exposure to dirt and moisture, as with hub gears, plus locating the additional mass between the two wheels and on the frame where it may be suspended, unlike with hub gears.
References
↑ Oxford English Dictionary (2nded.). 1989. derailleur, n. 1950 Chambers's Encycl. II. 307/2 The most popular variable gear in Great Britain is the 3- and 4-speed hub gear... 1959 Elizabethan Apr. 35/1 My lightweight bike with 4-speed hub gear...
1 2 "The Internal Gear Hub Review". Hubstripping.wordpress.com. Archived from the original on 2011-11-12. Retrieved 2011-11-21. Now you should be able to choose the gear hub group which fits your personal cycling purpose best!
1 2 Jobst Brandt (1993). The Bicycle Wheel (3rded.). Avocet. pp.59–64. The distance between flanges gives a wheel its lateral strength. Wheels with narrow flange spacing and many gears are less suited to rough roads than those with wider spacing and fewer gears. Large-flange hubs provide no functional advantage and have the disadvantage of added weight. Aggressively ridden tandem bicycle are an exception.
↑ Graham Moult (2007). "Sprockets for hub gears". hubgear.net. Archived from the original on 2011-07-23. Retrieved 2011-09-30. Your chainline can be affected by whether the sprocket is flat or dished - the smaller sprockets are generally flat, the larger ones are tend to be dished, and the mid-sized available in both shapes.
↑ "Trek Bicycle Case Study". Gates Corporation. Archived from the original on 2013-10-03. Retrieved 2014-02-27. Trek found that the contact points between the belt and the sprocket had worn.
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