Bicycle: Difference between revisions
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A '' | A '''bicycle''' or '''bike''' is a [[machine]] for human [[transportation]] that employs two [[wheel|wheels]]. Unlike most modern methods of transportation, bicycles are human-powered. | ||
== History of Bicycles == | == History of Bicycles == | ||
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== Types of Bicycles == | == Types of Bicycles == | ||
There are | There are many types of bicycles. Most sold today fit into one of these categories: | ||
# [[road bicycle|Road or Racing Bicycles]] -- characterized by narrow [[pneumatic tire|tires]], no shock absorbers, thin light frames, and drop handlebars. The frame generally encourages a more inclined posture. | # [[road bicycle|Road or Racing Bicycles]] -- characterized by narrow [[pneumatic tire|tires]], no shock absorbers, thin light frames, and drop handlebars. The frame generally encourages a more inclined posture. | ||
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# [[recumbent bicycle|Recumbent Bicycles]] -- A bicycle in which the rider employs a horizontal, foot-first posture. | # [[recumbent bicycle|Recumbent Bicycles]] -- A bicycle in which the rider employs a horizontal, foot-first posture. | ||
It should be noted, however, that bicycle enthusiasts have often mixed-and-matched designs and technologies, yielding bikes that are not easily classified | It should be noted, however, that bicycle enthusiasts have often mixed-and-matched designs and technologies, yielding bikes that are not easily classified, for instance, a tandem bicycle in which the front rider employs the recumbent position. | ||
== Parts of a Bicycle == | == Parts of a Bicycle == | ||
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''Main article:'' [[bicycle wheel]] | ''Main article:'' [[bicycle wheel]] | ||
The wheels of bicycles are very | The wheels of bicycles are very lightweight, yet strong and flexible enough to withstand bumps. A typical bicycle wheel consists of a central hub, a plethora of [[spoke|spokes]] leading to a circular rim, and a [[pneumatic tire]] fastened to the rim. | ||
==== The Hub ==== | ==== The Hub ==== | ||
=== The Transmission === | === The Transmission === | ||
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''Main article:'' [[bicycle transmission]] | ''Main article:'' [[bicycle transmission]] | ||
A human operator typically powers a bicycle by applying a [[force]] to pedals using his or her legs. The pedals are connected to a front sprocket ( | A human operator typically powers a bicycle by applying a [[force]] to pedals using his or her legs. The pedals are connected to a front sprocket (the ''chain ring'') by [[cams]] (''cranks'' or ''crank arms''), which translate the linear force from the foot into a [[torque]], thus rotating the chain ring. This torque is transmitted via a [[chain (transmission)]] to a rear sprocket (called a ''freewheel'' or ''cassette'', depending on the technology), which is coupled to the rear wheel. | ||
Alternatively, there are | Alternatively, there are bicycles which use a [[treadle]] mechanism in place of the pedals. | ||
==== Fixed-Gear, Fixies, and Track Bikes ==== | ==== Fixed-Gear, Fixies, and Track Bikes ==== | ||
In a fixed-gear bicycle, the rotation of the pedals is directly coupled with the rotation of the rear wheel. There is only one available gearing ratio. Such a bicycle cannot [[coast]], nor can the rider adjust the [[gear ratio]] to accommodate changes in terrain. | In a fixed-gear bicycle, the rotation of the pedals is directly coupled with the rotation of the rear wheel. There is only one available gearing ratio. Such a bicycle cannot [[coast]], nor can the rider adjust the [[gear ratio]] to accommodate changes in terrain. Such bicycles can also be ridden backwards. | ||
These bicycles are perceived as being more efficient. There are arguments that one of the major sources of inefficiency experienced by a cyclist are due to [[derailleur]] transmissions. For this reason, fixed-gear bicycles are often used in races. | |||
The rear wheel of a fixed-gear bicycle is marginally stronger than one from a multiple gear bicycle due to the wheel's [[wheel dish|dish]] -- an asymmetry in spoke structure necessitated by the width of multiple sprockets. This is also the case with single speed or internally geared bicycles. | The rear wheel of a fixed-gear bicycle is marginally stronger than one from a multiple gear bicycle due to the wheel's [[wheel dish|dish]] -- an asymmetry in spoke structure necessitated by the width of multiple sprockets. This is also the case with single speed or internally geared bicycles. | ||
==== Single Speed | ==== Single Speed Bicycles ==== | ||
A single speed bicycle should not be confused with a fixed-gear bicycle. A single speed bicycle features a [[free wheel]], which allows the rear wheel to move forward while the chain remains stationary. | A single speed bicycle should not be confused with a fixed-gear bicycle. A single speed bicycle features a [[free wheel]], which allows the rear wheel to move forward while the chain remains stationary. | ||
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==== No brakes, a la Fixed-Gear ==== | ==== No brakes, a la Fixed-Gear ==== | ||
When the pedals are directly coupled with the motion of the rear wheel, as is the case with fixed gear bicycles, a rider can brake by simply pedaling more slowly. For this reason, experienced fixed gear riders will often build bicycles without brakes. | When the pedals are directly coupled with the motion of the rear wheel, as is the case with fixed gear bicycles, a rider can brake by simply pedaling more slowly. For this reason, experienced fixed-gear riders will often build bicycles without brakes. | ||
However, as typical bicycle chains are not designed to withstand this sort of use, it is not a good idea | However, as typical bicycle chains are not designed to withstand this sort of use, it is not a good idea. | ||
== Bicycles in Sport == | == Bicycles in Sport == | ||
Revision as of 22:09, 1 April 2007
A bicycle or bike is a machine for human transportation that employs two wheels. Unlike most modern methods of transportation, bicycles are human-powered.
History of Bicycles
Types of Bicycles
There are many types of bicycles. Most sold today fit into one of these categories:
- Road or Racing Bicycles -- characterized by narrow tires, no shock absorbers, thin light frames, and drop handlebars. The frame generally encourages a more inclined posture.
- [[hybrid bicycle|Hybrid Bicycles] -- a blanket term for bicycles which have characteristics of both Road and Mountain bicycles.
- Mountain Bicycles -- characterized by wide, knobby tires, shock absorbers, heavier frames, and straight handlebars. The frame generally encourages a more upright posture.
- Tandem Bicycles -- A bicycle with two sets of handlebars, seats and transmission, to allow two people to ride at once.
- Recumbent Bicycles -- A bicycle in which the rider employs a horizontal, foot-first posture.
It should be noted, however, that bicycle enthusiasts have often mixed-and-matched designs and technologies, yielding bikes that are not easily classified, for instance, a tandem bicycle in which the front rider employs the recumbent position.
Parts of a Bicycle
Despite its apparent simplicity, a modern bicycle is actually a very complicated machine. Each part of a bicycle has been repeatedly improved upon by more than a century of engineering.
The Frame
Main article: bicycle frame
The Wheels
Main article: bicycle wheel
The wheels of bicycles are very lightweight, yet strong and flexible enough to withstand bumps. A typical bicycle wheel consists of a central hub, a plethora of spokes leading to a circular rim, and a pneumatic tire fastened to the rim.
The Hub
The Transmission
Main article: bicycle transmission
A human operator typically powers a bicycle by applying a force to pedals using his or her legs. The pedals are connected to a front sprocket (the chain ring) by cams (cranks or crank arms), which translate the linear force from the foot into a torque, thus rotating the chain ring. This torque is transmitted via a chain (transmission) to a rear sprocket (called a freewheel or cassette, depending on the technology), which is coupled to the rear wheel.
Alternatively, there are bicycles which use a treadle mechanism in place of the pedals.
Fixed-Gear, Fixies, and Track Bikes
In a fixed-gear bicycle, the rotation of the pedals is directly coupled with the rotation of the rear wheel. There is only one available gearing ratio. Such a bicycle cannot coast, nor can the rider adjust the gear ratio to accommodate changes in terrain. Such bicycles can also be ridden backwards.
These bicycles are perceived as being more efficient. There are arguments that one of the major sources of inefficiency experienced by a cyclist are due to derailleur transmissions. For this reason, fixed-gear bicycles are often used in races.
The rear wheel of a fixed-gear bicycle is marginally stronger than one from a multiple gear bicycle due to the wheel's dish -- an asymmetry in spoke structure necessitated by the width of multiple sprockets. This is also the case with single speed or internally geared bicycles.
Single Speed Bicycles
A single speed bicycle should not be confused with a fixed-gear bicycle. A single speed bicycle features a free wheel, which allows the rear wheel to move forward while the chain remains stationary.
Internally Geared Hubs on Utility Bikes
The Derailleur
The Brakes
Most bicycles feature a method for slowing the bicycle by using friction.
Caliper Brakes
V Brakes
Disk Brakes
No brakes, a la Fixed-Gear
When the pedals are directly coupled with the motion of the rear wheel, as is the case with fixed gear bicycles, a rider can brake by simply pedaling more slowly. For this reason, experienced fixed-gear riders will often build bicycles without brakes.
However, as typical bicycle chains are not designed to withstand this sort of use, it is not a good idea.
Bicycles in Sport
Main article: cycling