Bicycles are one of the most efficient modes of transportation. One billion bikes are used in the world today. Cycling is a form of exercise that works the heart, blood vessels, lungs and other muscle groups. It improves physical and mental fitness and lowers the risk of various diseases. Bicycles are also great fun.
Bicycle frames are made of steel and sometimes other lightweight materials, such as carbon fiber. Most frames are welded using a manual or machine process. Steel frames are the standard for ordinary bicycles, but carbon fiber composites are increasingly popular. Although carbon fiber composites are more expensive, they are lighter and stronger than steel. They are also rustproof.
The 1860s were a decade of invention for bicycles. Improvements in the bicycle included ball-bearing hubs, solid rubber tires, and lever-operated four-speed gearshifts. Another important milestone in bicycle history occurred during this decade, when the inventor James Stanley invented a bicycle with unique features. His bike was known as the Ordinary, and it had a wide front wheel. The 1860s were also the decade when freewheeling was invented, making biking more convenient and comfortable.
Bicycle wheels have a large number of spokes that support the rider’s weight. Without these spokes, the bicycle wheels would be squashed when the rider sat on them.