Historical overview
A bicycle, or bike, is a pedal-driven land vehicle with two
wheels attached to a frame, one behind the other. First introduced
in 19th-century Europe, bicycles evolved quickly into their
familiar, current design. Numbering over 1,000,000,000 in the world
today, bicycles provide the principal means of transportation in
many regions and a popular form of recreation and transport in
others.
The bicycle has affected history considerably in both the cultural
and industrial realms. In its early years, bicycle construction drew
on pre-existing technologies; more recently, bicycle technology has
contributed, in turn, to other, newer areas. Beyond recreation and
transportation, bicycles have been adapted for use in many
occupations, including the military, local policing, courier
services, and sports. A recurrent theme in bicycling has been the
tension between bicyclists and drivers of motor vehicles, each group
of whom argues for its fair share of the world's roadways. According
to members of Critical Mass, a bicycle activist group, "We aren't
blocking traffic, we are traffic!"
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Performance
In both biological and mechanical terms, the bicycle is
extraordinarily efficient. In terms of the amount of energy a
person must expend to travel a given distance, investigators
have calculated it to be the most efficient self-powered means
of transportation.1 From a mechanical viewpoint, up to 99% of
the energy delivered by the rider into the pedals is transmitted
to the wheels, although the use of gearing mechanisms may reduce
this by 10-15% 2 9. In terms of the ratio of cargo weight a
bicycle can carry to total weight, it is also a most efficient
means of cargo transportation. |
Bicycle physics
A rider stays upright on a bicycle by steering the bicycle
so that the point where the wheels touch the ground stays
underneath the center of gravity. Once underway, this effort
is largely replaced by physical forces generated by the
rotation of the wheels which produce a remarkable
"self-steering" effect.3 The angular momentum of the wheels
and the torque applied to them by the ground generates a
phenomenon called precession, by which the wheel turns, or
trails, toward whichever side the bicycle tilts. Like the
rider's steering adjustments, this motion automatically
returns the contact point of the wheel directly under the
center of gravity. These forces, perhaps aided at very high
speeds by the gyroscopic effect of the spinning wheels,4 are
sufficiently strong that a riderless bicycle going down a
slope will stay upright by itself. Conversely, a bicycle
whose steering fork is locked in a perfectly straight ahead
position is virtually impossible to balance. |
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Economic and social implications
Bicycle manufacturing proved to be a training ground for
other industries. Building modern bicycle frames led to the
development of advanced metalworking techniques, both for
the frames themselves and for special components such as
ball bearings, washers, and sprockets. These techniques
later enabled skilled metalworkers and mechanics to develop
the components used in early automobiles and aircraft. J. K.
Starley's company became the Rover Cycle Company Ltd. in the
late 1890s, and then the Rover auto maker. The Morris Motor
Company and Škoda also began in the bicycle business, as did
Henry Ford and the Wright Brothers. |
Interesting resources
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