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How do bicycles operate?

A bicycle’s performance, in both biological and mechanical terms, 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. 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.

Mechanical efficiency

From a mechanical viewpoint, up to 99% of the energy delivered by the rider into the pedals is transmitted to the wheels (clean, lubricated new chain at 400W), although the use of gearing mechanisms reduces this by 1-7% (clean, well-lubricated derailleurs), 4-12% (chain with 3-speed hubs), or 10-20% (shaft drive with 3-speed hubs). The higher efficiencies in each range are achieved at higher power levels and in direct drive (hub gears) or with large driven cogs (derailleurs).

Energy efficiency

A human being traveling on a bicycle at 16–24 km/h (10–15 mph), using only the power required to walk, is the most energy-efficient means of human transport generally available. Air drag, which increases with the square of speed, requires increasingly higher power outputs relative to speed, power increasing with the cube of speed as power equals force times velocity. A bicycle in which the rider lies in a supine position is referred to as a recumbent bicycle or, if covered in an aerodynamic fairing to achieve very low air drag, as a streamliner.
On firm, flat ground, a 70 kg (150 lb) person requires about 60 watts to walk at 5 km/h (3.1 mph). That same person on a bicycle, on the same ground, with the same power output, can travel at 15 km/h (9.3 mph) using an ordinary bicycle, so in these conditions the energy expenditure of cycling is one-third of walking.

Energy output

Active humans can produce between 1.5 W/kg (untrained women for longer periods) and 24 W/kg (top-class male athletes during 5 s). 5 W/kg is about the level reachable by ordinary male athletes for longer periods. Maximum power levels during one hour range from about 250 W (“healthy men”) to 500 W (exceptional men athletes)

Energy input

The energy input to the human body is in the form of food energy, usually quantified in kilocalories [kcal] or kiloJoules [kJ=kWs]. This can be related to a certain distance travelled and to body weight, giving units such as kJ/(km∙kg). The rate of food consumption, i.e. the amount consumed during a certain period ot time, is the input power. This can be measured in kcal/day or in J/s = W (1000 kcal/d ~ 48.5 W).
This input power can be determined by measuring oxygen uptake, or in the long term food consumption, assuming no change of weight. This includes the power needed just for living, called the basal metabolic rate BMR or roughly the resting metabolic rate.
The required food can also be calculated by dividing the output power by the muscle efficiency. This is 18-26%. From the example above, if a 70 kg person is cycling at 15 km/h by expending 60 W and a muscular efficiency of 20% is assumed, roughly 1 kJ/(km∙kg) extra food is required. For calculating the total food required during the trip, the BMR must first be added to the input power. If the 70 kg person is an old, short woman, her BMR could be 60 W, in all other cases a bit higher. Viewed this way the efficiency in this example is effectively halved and roughly 2 kJ/(km∙kg) total food is required.
Although this shows a large relative increase in food required for low power cycling, in practice it is hardly noticed, as the extra energy cost of an hour’s cycling can be covered with 50 g nuts or chocolate. With long and fast or uphill cycling, the extra food requirement however becomes evident.
To complete the efficiency calculation, the type of food consumed determines the overall efficiency. For this the energy needed to produce, distribute and cook the food must be considered.

Typical speeds

In utility cycling there is a large variation; an elderly person on an upright roadster might do less than 10 km/h (6.2 mph) while a fitter or younger person could easily do twice that on the same bicycle. For cyclists in Copenhagen, the average cycling speed is 15.5 km/h (9.6 mph).
On a racing bicycle, a reasonably fit rider can ride at 40 km/h (25 mph) on flat ground for short periods

Reduction of weight and rotating mass

There has been major corporate competition to lower the weight of racing bikes in order to be faster uphill and accelerating. The UCI sets a limit of 6.8 kg on the minimum weight of bicycles to be used in sanctioned races

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Social aspects of bikes (P.1)

Bicycle manufacturing proved to be a training ground for other industries and 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.
It was a pair of bicycle mechanics in Dayton, Ohio, Wilbur and Orville Wright, who achieved the first powered flight in an aircraft. Their design owed much to knowledge gained from bicycles.

They also served to teach the industrial models later adopted, including mechanization and mass production (later copied and adopted by Ford and General Motors), vertical integration (also later copied and adopted by Ford), aggressive advertising (as much as 10% of all advertising in U.S. periodicals in 1898 was by bicycle makers), lobbying for better roads (which had the side benefit of acting as advertising, and of improving sales by providing more places to ride), all first practiced by Pope. In addition, bicycle makers adopted the annual model change (later derided as planned obsolescence, and usually credited to General Motors), which proved very successful.

Early bicycles were an example of conspicuous consumption, being adopted by the fashionable elites. In addition, by serving as a platform for accessories, which could ultimately cost more than the bicycle itself, it paved the way for the likes of the Barbie doll.

Bicycles helped create, or enhance, new kinds of businesses, such as bicycle messengers, traveling seamstresses, riding academies, and racing rinks. Their board tracks were later adapted to early motorcycle and automobile racing. There were a variety of new inventions, such as spoke tighteners, and specialized lights, socks and shoes, and even cameras, such as the Eastman Company’s Poco. Probably the best known and most widely used of these inventions, adopted well beyond cycling, is Charles Bennett’s Bike Web, which came to be called the jock strap.

They also presaged a move away from public transit that would explode with the introduction of the automobile.
J. K. Starley’s company became the Rover Cycle Company Ltd. in the late 1890s, and then simply the Rover Company when it started making cars. Morris Motors Limited (in Oxford) and Škoda also began in the bicycle business, as did the Wright brothers. Alistair Craig, whose company eventually emerged to become the engine manufacturers Ailsa Craig, also started from manufacturing bicycles, in Glasgow in March 1885.

In general, U.S. and European cycle manufacturers used to assemble cycles from their own frames and components made by other companies, although very large companies (such as Raleigh) used to make almost every part of a bicycle (including bottom brackets, axles, etc.) In recent years, those bicycle makers have greatly changed their methods of production. Now, almost none of them produce their own frames.

Many newer or smaller companies only design and market their products; the actual production is done by Asian companies. For example, some 60% of the world’s bicycles are now being made in China. Despite this shift in production, as nations such as China and India become more wealthy, their own use of bicycles has declined due to the increasing affordability of cars and motorcycles. One of the major reasons for the proliferation of Chinese-made bicycles in foreign markets is the lower cost of labor in China.

In line with the European financial crisis, in Italy in 2011 the number of bicycle sales (1.75 million) just passed the number of new car sales.

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Choosing your equipments

Be a smart and well – equipped cycler. Before you purchase a bicycle, think about the type of cycling you plan to do. Pick and choose from the myriad of options to find the combination of features that best suits you and your goals.
You might be tempted to buy everything available for your bicycle. In the beginning, you may not need a bicycle computer, GPS, and heavy winter gear. As your experience and skill level improve, you can add items to your gear collection.

The Bicycle

If you plan on a combination of road and mountain biking, pick a hybrid. Road bikes are for the road and mountain bikes are for off-road use.
The most important part of bicycle shopping is finding the right frame size. A frame that is too small will place unnecessary strain on your joints. A frame that is too large will decrease the level of control you have over your bike. If the frame is not properly fitted to your body, your center of gravity will be greatly compromised.
When choosing your bicycle, pick the best combination of features for the type of cycling you plan to do. For example, don`t put off-road tires on a road bike.

The Shoes

Many road bikes along with mountain bikes include clipless pedals to which special shoes attach, via a cleat, permitting the rider to pull on the pedals as well as push.
The right cycling shoes will support your foot on the pedal. This can reduce cramping and foot fatigue as you ride. The shoe you pick will depend on the type of pedal you plan to use with your bicycle.

The Helmet

Helmets offer essential protection while cycling. Modern designs are sleek and lightweight. There is no longer a question of style when choosing to wear a helmet. Helmets are proven to save lives and prevent life altering injuries from having their full effect. A good helmet will cost you at least US$50 and the best helmets can cost hundreds of dollars.

The Clothes

Dress for the weather. Lightweight, breathable fabrics are excellent for keeping the body cool and dry in warm weather. Moisture-wicking, heat retaining fabrics like fleece are best for winter riding. Gloves, glasses, socks, and extra outer layers are important regardless of season.
In general, fabrics suited for most outdoor sports will be appropriate for cycling. However, avoid loose fitting clothing as these clothes may get caught in your spokes, chain, or handlebars.

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No. 1 rule : safety first!

Bicycles are legally considered “vehicles” on roadways. That means bicyclists must obey the rules of the road like drivers of any other vehicle and must be treated as equal users by all other vehicles. Here are some safety tips:

  1. Obey traffic signs and signals – Bicycles must follow the rules of the road like other vehicles.
  2. Never ride against traffic – Motorists aren’t looking for bicyclists riding on the wrong side of the road. State law and common sense require that bicyclists drive like other vehicles.
  3. Follow lane markings – Don’t turn left from the right lane. Don’t go straight in a lane marked “right-turn only.”
  4. Don’t pass on the right – Motorists may not look for or see a bicycle passing on the right.
  5. Scan the road behind you – Learn to look back over your shoulder without losing your balance or swerving. Some riders use rear-view mirrors.
  6. Keep both hands ready to brake – You may not stop in time if you brake one-handed. Allow extra distance for stopping in the rain, since brakes are less efficient when wet.
  7. Wear a helmet and never ride with headphones – Always wear a helmet. Never wear a headphone while riding a bike.
  8. Dress for the weather – In rain wear a poncho or waterproof suit. Dress in layers so you can adjust to temperature changes. Wear bright colored clothing.
  9. Use hand signals – Hand signals tell motorists and pedestrians what you intend to do. Signal as a matter of law, of courtesy, and of self-protection.
  10. Ride in the middle of the lane in slower traffic – Get in the middle of the lane at busy intersections and whenever you are moving at the same speed as traffic.
  11. Choose the best way to turn left – There are two choices: (1) Like an auto: signal to move into the left turn lane and then turn left. (2) Like a pedestrian: ride straight to the far side crosswalk. Walk your bike across.
  12. Make eye contact with drivers – Assume that other drivers don’t see you until you are sure that they do. Eye contact is important with any driver which might pose a threat to your safety.
  13. Look out for road hazards – Watch out for parallel-slat sewer grates, gravel, ice, sand or debris. Cross railroad tracks at right angles.
  14. Use lights at night – The law requires a white headlight (visible from at least 500 feet ahead) and a rear reflector or taillight (visible up to 300 feet from behind).
  15. Keep your bike in good repair – Adjust your bike to fit you and keep it working properly. Check brakes and tires regularly. Routine maintenance is simple and you can learn to do it yourself.