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Gear Inches
Gear inches is one of several relative measures of bicycle gearing, giving an indication of the mechanical advantage of different gears. Values for 'gear inches' typically range from 20 (very low gearing) via 70 (medium gearing) to 125 (very high gearing); as in a car, low gearing is for going up hills and high gearing is for going fast. 'Gear inches' is actually the diameter in inches of the drive wheel of a penny-farthing bicycle with equivalent gearing. Origin of the term When the high wheeler or penny-farthing was the "ordinary" bicycle form, the comparative diameter in inches of the driven wheel was an indication of relative speed and effort. A 60-inch wheel propelled a bicycle faster than a 50-inch wheel when both were cranked at the same cadence. The technology of the high wheeler imposed a natural limit—a 60-inch wheel was about the maximum size that could be straddled by ordinary sized legs. When "safeties" replaced "ordinaries," chains and sprockets allowed small whee ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bicycle Gearing
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. On some bicycles there is only one gear and, therefore, the gear ratio is fixed, but most modern bicycles have multiple gears and thus multiple gear ratios. A shifting mechanism allows selection of the appropriate gear ratio for efficiency or comfort under the prevailing circumstances: for example, it may be comfortable to use a high gear when cycling downhill, a medium gear when cycling on a flat road, and a low gear when cycling uphill. Different gear ratios and gear ranges are appropriate for different people and styles of cycling. A cyclist's legs produce power optimally within a narrow pedalling speed range, or cadence. Gearing can be optimized to use this narrow range as efficiently as possible. As in other types of transmissions, the gear ratio is closely related to the mechanica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mechanical Advantage
Mechanical advantage is a measure of the force amplification achieved by using a tool, mechanical device or machine system. The device trades off input forces against movement to obtain a desired amplification in the output force. The model for this is the ''law of the lever.'' Machine components designed to manage forces and movement in this way are called mechanisms. An ideal mechanism transmits power without adding to or subtracting from it. This means the ideal machine does not include a power source, is frictionless, and is constructed from rigid bodies that do not deflect or wear. The performance of a real system relative to this ideal is expressed in terms of efficiency factors that take into account departures from the ideal. Lever The lever is a movable bar that pivots on a fulcrum attached to or positioned on or across a fixed point. The lever operates by applying forces at different distances from the fulcrum, or pivot. The location of the fulcrum determi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Penny-farthing
The penny-farthing, also known as a high wheel, high wheeler or ordinary, is an early type of bicycle. It was popular in the 1870s and 1880s, with its large front wheel providing high speeds (owing to its travelling a large distance for every rotation of the legs) and comfort (the large wheel provides greater shock absorption). It became obsolete in the late 1880s with the development of modern bicycles, which provided similar speed amplification via chain-driven gear trains and comfort through pneumatic tires, and were marketed in comparison to penny-farthings as " safety bicycles" because of the reduced danger of falling and the reduced height to fall from. The name came from the British penny and farthing coins, the former being much larger than the latter, so that the side view resembles a larger penny (the front wheel) leading a smaller farthing (the rear wheel). Although the name "penny-farthing" is now the most common, it was probably not used until the machines were ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cadence (cycling)
In cycling, cadence (or pedalling rate) is a measure of angular speed calculated as the number of revolutions of the crank per minute; this is the rate at which a cyclist is pedalling/turning the pedals. Cadence is directly proportional to wheel speed, but is a distinct measurement and changes with gearing—which determines the ratio of crank rpm to wheel rpm. Cyclists typically have a cadence at which they feel most comfortable, and on bicycles with many gears it is possible to maintain a preferred cadence at a wide range of speeds. Recreational and utility cyclists typically cycle around 60–80 rpm. According to cadence measurement of seven professional cyclists during three-week races they cycle about 90 rpm during flat and long (~190 km) group stages and individual time trials of ~50 km. During ~15 km uphill cycling on high mountain passes they cycle about 70 rpm. Cyclists choose cadence to minimise muscular fatigue, and not metabolic demand, since oxyg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sheldon Brown (bicycle Mechanic)
Sheldon Brown (July 14, 1944 – February 4, 2008) was an American bicycle mechanic, technical expert and author. He contributed to print and online sources related to bicycling and bicycle mechanics, in particular the web site ''Sheldon Brown's Bicycle Technical Info''. His knowledge of bicycles was described as "encyclopaedic" by ''The Times'' of London. Background Brown was the parts manager, webmaster and technical consultant of Harris Cyclery, a bike shop in West Newton, Massachusetts, as well as an enthusiast of vintage and classic bicycles in addition to cycling in general. Brown maintained ''Sheldon Brown's Bicycle Technical Info'', a web site highlighting a broad range of cycling subjects ranging from how to fix a bicycle flat tire to details on Raleigh and English three-speed bicycles, Sturmey-Archer hubs, tandems, and fixed-gear bicycles. He repaired cameras and was an amateur photographer. His site features his photographic work. Brown maintained an English-French c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dimensionless Quantity
A dimensionless quantity (also known as a bare quantity, pure quantity, or scalar quantity as well as quantity of dimension one) is a quantity to which no physical dimension is assigned, with a corresponding SI unit of measurement of one (or 1), ISBN 978-92-822-2272-0. which is not explicitly shown. Dimensionless quantities are widely used in many fields, such as mathematics, physics, chemistry, engineering, and economics. Dimensionless quantities are distinct from quantities that have associated dimensions, such as time (measured in seconds). Dimensionless units are dimensionless values that serve as units of measurement for expressing other quantities, such as radians (rad) or steradians (sr) for plane angles and solid angles, respectively. For example, optical extent is defined as having units of metres multiplied by steradians. History Quantities having dimension one, ''dimensionless quantities'', regularly occur in sciences, and are formally treated within the fie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bicycle Gearing
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. On some bicycles there is only one gear and, therefore, the gear ratio is fixed, but most modern bicycles have multiple gears and thus multiple gear ratios. A shifting mechanism allows selection of the appropriate gear ratio for efficiency or comfort under the prevailing circumstances: for example, it may be comfortable to use a high gear when cycling downhill, a medium gear when cycling on a flat road, and a low gear when cycling uphill. Different gear ratios and gear ranges are appropriate for different people and styles of cycling. A cyclist's legs produce power optimally within a narrow pedalling speed range, or cadence. Gearing can be optimized to use this narrow range as efficiently as possible. As in other types of transmissions, the gear ratio is closely related to the mechanica ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Derailleur Gears
Shimano 600 front derailleur (1980) 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. Modern front and rear derailleurs typically consist of a moveable chain-guide that is operated remotely by a Bowden cable attached to a shifter mounted on the down tube, handlebar stem, or handlebar. When a rider operates the lever while pedalling, the change in cable tension moves the chain-guide from side to side, "derailing" the chain onto different sprockets. Etymology ''Dérailleur'' is a French word, derived from the derailment of a train from its tracks. Its first recorded use was 1930. History A modern road bicycle drivetrain with front and rear derailleurs Various derailleur systems were designed and built in the late 19th century. One example is the Protean two-speed derailleur available on the Whippet safety bicycle. The French bicycl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hub Gear
A hub gear, internal-gear hub, internally geared 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. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Outline Of Cycling
:''This article is an outline about the activity of cycling. For an outline about bicycles themselves, see outline of bicycles.'' :The following ''outline'' is provided as an overview of, as well as a topical guide to cycling: Cycling, also called bicycling or biking, is the activity of using / riding bicycles, (at least partially) human-powered, wheeled vehicles (typically by foot pedalling), for purposes including transport, recreation, social interaction, exercise, sport, therapy, other purposes, or any combination thereof. Persons engaged in cycling are called cyclists, bikers, or sometimes bicyclists. They typically either dress for where they are going, or for the cycling, sometimes having another set of clothing with them, or arranged. Apart from regular two-wheeled bicycles, cycling also includes riding unicycles, tricycles, quadricycles, and other similar human-powered wheeled vehicles (HPVs). Some bicycles are sold with (electric) motors (e-bikes), or oth ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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