Parts of a Bicycle

The bicycle is one of the simplest contraptions used for transportation. It is environment friendly, easy to handle and easy to store when not in use. It can be carried on the roof of a car or slung behind the car or packed into the boot of a car. As a matter of fact it can be used wherever there is a hint of a path that has is not too steep. Bikes have been designed for use on flat roads, race tracks and mountainous terrain. Normally one person can ride it but in typical cases more than one person can be accommodated on the front bar leading from the seat to the handle, the normal seat and the seat over the rear wheel.

The Frame

bike frame

Photo by missionbicycle

The main frame on which all the different parts of the bicycle are attached is an irregular five-sided structure made of circular pipes. The weight of the bicycle depends mainly on the thickness of the main frame. The top of the main frame is parallel to the ground with the other sides attached to it at various angles. The side at the front holds the handle and the front wheel whereas the side at the rear holds the seat and the rear wheel. The two lower sides which are attached to the front and the rear side meet at a point where the pedal is located.

The rear side of the main frame extends down to another fork that holds the rear wheel. The rear wheel is an exact replica of the front wheel with the same rubber tires and inflatable tubes. The inflatable tubes for the tires normally have brass nozzles which stick out of the wheel frame. An air pump is attached to this nozzle to inflate the tubes. The air is held inside the tube by a one way valve that is operated by a small and narrow rubber tube that covers a small hole on the upper portion of the nozzle. This portion can be removed to replace the rubber tube of the valve in case it fails to hold the air inside the inflatable tube.

The seat is attached to the rear side of the main frame with the help of a pipe that slides in and out of circular frame. The height of the seat can be adjusted by loosening the nut holding this rod in place and then either by pressing it down or pulling it out. The seat can be made of leather or rubber mounted on three coils of springs to give added comfort. Seats for racing bikes are usually much smaller than normal bicycles or sports bikes.


bike tire

Photo by Robert Baker

The handle is the part of the bike used for steering it. It is about two to two and a half feet wide and has plastic or rubber grips provided at both ends for holding it strait. Turning it in either way can cause the bike to move right or left. The handle is fixed to a perpendicular rod which passes through the front of the main frame and leads to a fork at the bottom. This fork holds the front wheel in place. The front wheel is fixed to the fork with the help of an axle that has ball bearings on both sides which enable the free movement of the wheel on the axle.

Moving Forward

Bicycles usually come with two wheels. There have been cases when they have been given an elongated form with multiple seats and multiple pedals which could be ridden by multiple people pedaling simultaneously to provide more power. These are called tandem bicycles. Sometimes an additional wheel has also been added to the bicycles to give them more stability which are called tricycles or bikes with three wheels. To understand how it operates you have to know the various bike parts with which it is constructed from.

Rubber tires are mounted on the wheel frame with rubber tubes between the tire and the frame which are inflated with air. The levers for the front and the rear brakes are mounted on either side of the handle so that they can be easily operated with the hand while gripping the handle. The levers are attached to the arms operating the brake shoes through wires. When the levers are depressed the wire gets pulled through a sheath which acts against the pull and actuates the brake arms bring the brake shoes to rub against the wheels to reduce speed.

The size of the wheels depends on the use to which the bike is put to. Bicycles for children have much smaller wheels in comparison to those which are ridden by adults. The wheels of racing bikes are around twenty six inches in diameter while the normal bicycles have wheels that are more than twenty-eight inches in diameter. Bikes used for sports and cycling in difficult terrain may have a variety of sizes. The wheels of sports bikes are normally much more thick than those of normal bicycles whereas racing bikes have the thinnest tires to make them as light as possible.

To make them more light in weight, tires made from materials other than rubber are sometimes used which are solid in nature and do not have any inflatable tubes. The power for the forward movement of the bicycle is provided through the pedals. These pedals are located at the lowermost end of the main frame where the two longer sides of the frame meet. The pedals are arranged in such a way that they are in line but one hundred and eighty degrees away from one another. When one pedal is at its highest point the other one is at its lowest. Both the feet are used to operate the pedals. When one foot is used to press one of the pedals the other foot is relaxed to let the other pedal come up.

The pedals are fixed on an axle passing horizontally to the ground and perpendicular to the frame. Just like all the other portions of the bike where moving parts meet the main frame such as the handle and the wheels, the pedals also move on two sets of ball bearings on either side of the axle. The sizes of the ball bearings in each portion may differ in size or may be of the same size. Bigger sized ball bearings provide more strength while smaller sized ball bearings better smoothness.

Mechanisms that Make it Move

bike chain

Photo by bike

The chain is the part which transfers the power from the pedals to the rear wheels to move the bike forward. The chain passes over a large sprocket fixed usually to the left side pedal. On the rear wheel there a free wheel which has teeth matching the links of the chain. It is called a free wheel because it drives the bicycle when moved forward while allowing you rest your feet when you are not pedaling. The free wheel is fixed to the axle of the rear wheel and has a ratchet inside it which allows movement in the forward direction only.

The ratchet can be of a different version where stopping its forward motion or moving it backwards can cause a braking action to reduce the speed of the bicycle. The chain is made up of a large number of links which can be removed or added to decrease or increase the total length of the chain. The wheels have two portions one of which is the outer frame while the second portion is the one which contains the axle. Both of these portions are held together by the spokes which can be adjusted to give the wheel a perfectly circular periphery and correct any maladjustment or slight tilt.

The ball bearings in the handle, the wheel axles and the axle for the pedals should be greased and oiled to keep the bicycle running smoothly. The handle can be dismantled by loosening the clamp that holds it to the fork. By loosening the nut that allows the front fork to be removed, access to the two sets of runners and ball bearings is possible. The wheels can be removed by loosening the nuts on the axle at either end. The circular nut acting as half of the runner can be loosened to access the ball bearings on the wheel. Similarly, the ball bearings can be accessed by loosening the cotter pin and removing the pedal and the runner.

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