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A bicycle brake reduces the speed of a bicycle or prevents it from moving. The three main types are: rim brakes, disc brakes, and drum brakes. There have been various types of brakes used throughout history, and several are still in use today. Most bicycle brake systems consist of three main components: a mechanism for the rider to apply the brakes, such as brake levers or pedals; a mechanism for transmitting that signal, such as Bowden cables, hydraulic hoses, rods, or the bicycle chain; and the brake mechanism itself, a caliper or drum, to press two or more surfaces together in order to convert, via friction, kinetic energy of the bike and rider into thermal energy to be dissipated. ==History== Karl Drais included a pivoting brake shoe that could be pressed against the rear iron tire of his 1817 Laufmaschine. This was continued on the earliest bicycles with pedals, such as the boneshaker, which were fitted with a spoon brake to press onto the rear wheel. The brake was operated by a lever or by a cord connecting to the handlebars. The rider could also slow down by resisting the pedals of the fixed wheel drive. The next development of the bicycle, the penny-farthings, were similarly braked with a spoon brake or by back pedalling. During its development from 1870 to 1878, there were various designs for brakes, most of them operating on the rear wheel. However, as the rear wheel became smaller and smaller, with more of the rider's weight over the front wheel, braking on the rear wheel became less effective. The front brake, introduced by John Kean in 1873, had been generally adopted by 1880 because of its greater stopping power. Some penny-farthing riders used only back pedalling and got off and walked down steep hills, but most also used a brake.〔 Having a brake meant that riders could coast down hill by taking their feet off the pedals and placing the legs over the handlebars, although most riders preferred to dismount and walk down steep hills.〔 Putting the legs under the handlebars with the feet off the pedals placed on foot-rests on the forks had resulted in serious accidents caused by the feet getting caught in the spokes.〔 An alternative to the spoon brake for penny-farthings was the caliper brake patented by Browett and Harrison in 1887. This early version of caliper braking used a rubber block to contact the outside of the penny-farthing's small rear tire. The 1870s and 1880s saw the development of the safety bicycle which roughly resembles bicycles today, with two wheels of equal size, initially with solid rubber tires. These were typically equipped with a front spoon brake and no rear brake mechanism, but like penny-farthings they used fixed gears, allowing rear wheel braking by resisting the motion of the pedals. The relative fragility of the wooden rims used on most bicycles still precluded the use of rim brakes. In the late 1890s came the introduction of rim brakes and the freewheel.〔 With the introduction of mass-produced pneumatic tyres by the Dunlop Tyre Company, the use of spoon brakes began to decline, as they tended to quickly wear through the thin casing of the new tyres. This problem led to demands for alternative braking systems. On November 23, 1897, Abram W. Duck of Duck's Cyclery in Oakland, California was granted a patent for his ''Duck Roller Brake'' (U.S. Patent 594,234).〔Duck, Abram W., ''United States Patent Office, Letters Patent No. 594,234'', November 23, 1897〕 The duck brake used a rod operated by a lever on the handlebar to pull twin rubber rollers against the front tire, braking the front wheel.〔Duck, Abram W., ''Patent No. 594,234''〕 In 1898, after the advent of freewheel coasting mechanisms, the first internal coaster brakes were introduced for the rear wheel. The coaster brake was contained in the rear wheel hub, and was engaged and controlled by backpedaling, thus eliminating the issue of tire wear. In the United States, the coaster brake was the most commonly fitted brake throughout the first half of the 20th century, often comprising the only braking system on the bicycle. 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「bicycle brake」の詳細全文を読む スポンサード リンク
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