Posted on Leave a comment

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

Posted on Leave a comment

Social aspects of bikes (P.2)

Around the turn of the 20th century, bicycles reduced crowding in inner-city tenements by allowing workers to commute from more spacious dwellings in the suburbs. They also reduced dependence on horses. Bicycles allowed people to travel for leisure into the country, since bicycles were three times as energy efficient as walking and three to four times as fast.
A number of cities around the world have implemented schemes known as bicycle sharing systems or community bicycle programs.The first of these was the White Bicycle plan in Amsterdam in 1965. It was followed by yellow bicycles in La Rochelle and green bicycles in Cambridge. These initiatives complement public transport systems and offer an alternative to motorized traffic to help reduce congestion and pollution. In Europe, especially in the Netherlands and parts of Germany and Denmark, bicycle commuting is common. In Copenhagen, a cyclists’ organization runs a Cycling Embassy that promotes biking for commuting and sightseeing. The United Kingdom has a tax break scheme (IR 176) that allows employees to buy a new bicycle tax free to use for commuting.

In the Netherlands all train stations offer free bicycle parking, or a more secure parking place for a small fee, with the larger stations also offering bicycle repair shops. Cycling is so popular that the parking capacity may be exceeded, while in some places such as Delft the capacity is usually exceeded. In Trondheim in Norway, the Trampe bicycle lift has been developed to encourage cyclists by giving assistance on a steep hill. Buses in many cities have bicycle carriers mounted on the front.

There are towns in some countries where bicycle culture has been an integral part of the landscape for generations, even without much official support. That is the case of Ílhavo, in Portugal.

In cities where bicycles are not integrated into the public transportation system, commuters often use bicycles as elements of a mixed-mode commute, where the bike is used to travel to and from train stations or other forms of rapid transit. Some students who commute several miles drive a car from home to a campus parking lot, then ride a bicycle to class. Folding bicycles are useful in these scenarios, as they are less cumbersome when carried aboard. Los Angeles removed a small amount of seating on some trains to make more room for bicycles and wheelchairs.

Some US companies, notably in the tech sector, are developing both innovative cycle designs and cycle-friendliness in the workplace. Foursquare, whose CEO Dennis Crowley “pedaled to pitch meetings … [when he] was raising money from venture capitalists” on a two-wheeler, chose a new location for its New York headquarters “based on where biking would be easy”. Parking in the office was also integral to HQ planning. Mitchell Moss, who runs the Rudin Center for Transportation Policy & Management at New York University, said in 2012: “Biking has become the mode of choice for the educated high tech worker.”
Bicycles offer an important mode of transport in many developing countries. Until recently, bicycles have been a staple of everyday life throughout Asian countries. They are the most frequently used method of transport for commuting to work, school, shopping, and life in general. In Europe, bicycles are commonly used. They also offer a degree of exercise to keep individuals healthy.

Bicycles are also celebrated in the visual arts. An example of this is the Bicycle Film Festival, a film festival hosted all around the world.

Bicycles also contributes to poverty alleviation. Experiments done in Uganda, Tanzania, and Sri Lanka on hundreds of households have shown that a bicycle can increase a poor family’s income as much as 35%.
Transport, if analyzed for the cost-benefit analysis for rural poverty alleviation, has given one of the best returns in this regard. For example, road investments in India were a staggering 3-10 times more effective than almost all other investments and subsidies in rural economy in the decade of the 1990s. What a road does at a macro level to increase transport, the bicycle supports at the micro level. The bicycle, in that sense, can be an important poverty-eradication tool in poor nations.

Posted on Leave a comment

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.

Posted on Leave a comment

Legal requirements for riding

Bicycle law is the parts of law that apply to the riding of bicycles. It varies from country to country, but in general, cyclists’ right to the road has been enshrined in international law since 1968, with the accession of the Vienna Convention on Road Traffic. Under that treaty, bicycles have the legal status of vehicles, and cyclists enjoy the legal status of vehicle operators. There are over 150 contracting parties to the treaty, including the United States, Canada, Mexico, the United Kingdom, Ireland, almost all of Europe, Australia, New Zealand, Japan, and China. In countries that are contracting parties, the treaty has the force of law, and its provisions have been incorporated into national law.
The position of British cyclists was first established by the Local Government Act in August, 1888. It removed the right of local councils to treat cyclists among the “nuisances” it could ban and defined them as “carriages”.
International varieties of bicycle law

Bicycle laws in the Mainland China

Laws may exist, but they are almost universally ignored. When asked, bicyclists in Shenzhen seem only to be aware of the law that makes electric bicycles illegal except for licensed delivery or tradesmen, but nobody worries about it because the cops almost never stop you. The unwritten rules of the road are roughly as follows: Ride on the right, unless there is a truck, car or bike, delivery trike or motorcycle heading toward you on the wrong side of the street. This happens every 2 minutes or so on most city streets. When this happens, ride either on the sidewalk, the middle of the road or on the other side of the road facing traffic. There are seemingly no laws or conventions about which side of the road or sidewalk to ride on. Approximately half of the bicyclists ride the wrong way on one way streets or in the lane reserved for oncoming traffic. The most common practice for turning left on a 2 lane street is do so from the wrong side of the road, against oncoming bike and vehicular traffic, forcing your way around the oncoming cars until you find an opening, then turn left into oncoming traffic and fight your way across onto your own side of the road. The rest of the people use a less predictable approach. Bicycles (and pedestrians) never have the right of way. Motorized vehicles never the yield the right of way unless it is almost certain that the cyclist will be killed. In fact, if a motorist or motorcyclist thinks there is any chance that allowing you to pass would require them to slow down, they will deliberately overtake you and cut you off. On a typical 20 minute commute, this will happen at least 2 or 3 times. There are also no conventions about what to do when two cyclist meet head-on on a sidewalk (where about 70% of cyclists travel). An equal number pass on the right as on the left, with frequent collisions.

Bicycle laws in the United States

For at least the past 60 years, bike safety rules and cycling laws have been drummed into the head of children, such that good cycling habits and etiquette is pretty much ingrained into the minds of the populous. The vast majority of motorized vehicles will automatically give you the right way. Similarly, the vast majority of bicyclists travel on the right hand side of the road, and almost always yield for pedestrians. The few cyclists travelling on sidewalks are mostly children or families with children. Everyone knows that riding on the sidewalk is illegal for an adult, but generally people have enough respect for the law to ride on the right hand side of the sidewalk most of the time, and yield for pedestrians.

Posted on Leave a comment

Your bikes need love too!

Your bike is a mess? We can give you some easily done basic bicycle care steps that’ll rejuvenate most well-ridden two-wheelers. And the same tips can keep a new bike running and looking new for as long as you want.

Pump It Up

Probably, the number one reason bikes fall apart is because people ignore the tires. Here’s what happens: Bicycle tires have very little air in them. And bicycle tubes, which are made of butyl rubber, are porous enough to allow air to seep out.

The result is tires softening over a period of about a week for road bikes and about a month for mountain bikes (though it depends some on tire size).

When the tires get soft, bad things happen. Some folks decide to stop riding the bike because they think they have flat tires and they put off getting the flat fixed because it means loading the bike in the car and dragging it down to the bike shop.

Lube It or Lose It

A bicycle is made up of a bunch of moving metal parts, many of which are meshing with each other. In order to keep these parts from grinding each other to dust as you pedal merrily along, they should be lubricated.

Spinning parts containing bearings, such as the wheels, pedals, bottom bracket (what the crankset is mounted to), and headset (the mechanism that connects the fork to the frame and allows steering), come from the manufacturer packed with grease. About once a year, these components should be dismantled, checked and regreased. But, because special tools are needed and the work is required only occasionally, you may prefer to leave this job to a bike shop mechanic.

Keep It Clean

Mountain bikers, especially those who ride in the mud, should keep a cleaning kit in the corner of the garage ready for use at ride’s end. All that’s needed is a bucket with some sponges and dishwashing detergent and a nearby hose.

When you return from a ride, prop the bike up and spray off the majority of the mud and muck with the hose. It’s crucial to not blast the water sideways at the bike. Doing so may force the water into the pedals, hubs and bottom bracket, which may compromise the grease and bearings inside these components. Instead, spray water only from above and don’t ever direct it toward greased parts.

Store It

I tell everyone to store bike(s) inside. It’s the best way to keep them running and looking like new. And it doesn’t take much in the way of space or supplies. The only item needed is a bike hook. These are shaped like question marks and coated with vinyl so as not to scratch the wheel when you hang the bike on the hook.

Install the hook in a stud in a wall or a rafter or beam; anywhere where the bike can hang vertically is fine. I’ve seen bikes stored in stairwells, bathrooms, bedrooms—anyplace you can find dead space is fine. It’s also possible to use two hooks and hang the bike horizontally, one wheel on either hook.