|
A bicycle is a two wheeled vehicle driven by the riders feet pushing on cranks or pedals. A common misconception is that the earliest form of bicycle was the dandy-horse, which was pushed along by the rider's feet. However, while both the dandy-horse and the later bicycle are both velocipedes, the dandy-horse is not propelled by cranks.
The first bicycle was introduced to England from France in 1868, and comprised two solid wheels of equal size fitted to a frame, much like a modern bicycle in appearance, with a saddle fitted in the centre and propelled by cranks attached to the front wheel. This vehicle provided such a bumpy ride to the rider that it became popularly known as 'the bone-shaker'. Later came the Penny-Farthing with pedals fixed to the large front wheel which was made large to achieve high speeds. Later still, around 1895, came the safety bicycle with pedals driving the rear wheel by way of a chain, and the rider sitting upon a saddle set back from the front wheel so as to reduce the chances of falling forwards over the handlebars, from this developed the Raleigh bicycle design of 1900 which forms the basis of the modern bicycle. In 1888 the two-person tandem bicycle was invented.
In 1906 it was reported that speeds of 50 mph were attained on a bicycle. Around the same time, slightly earlier, the motorised bicycle (motorcycle or motorbike) was invented.
A typical bicycle is comprised of several parts. The principal and essential being: the frame, front forks, wheels, pedals, saddle, handlebars, chain and brakes. The largest part of the bicycle is the frame, and these vary in design depending upon the specialised intention of the bicycle.
A frame for a BMX bicycle being small, heavily braced and made of aluminium. The frame for BMX xyxling needs to be strong so as to endure the stresses of the bumpy ride, and the saddle low as competitors never sit down during a competition and as such they need space to sprint and jump with ease.
Cross-Country cycle frames are generally made of aluminium and carbon-fibre so as to be light weight. They are relatively small frames to allow quick and easy mounting and dismounting off road, and strong to endure off-road bumpy conditions. The smaller frames are often compensated for by having a longer seat post to allow a normal height saddle position.
The cycle speedway bicycle frame is designed primarily for strength, and as such is typically made from steel or aluminium.
Road racing bicycle frames are designed to be light and stiff. Traditionally they ewre made of steel, but by the start of the 21st century carbon fibre was being used for the more expensive models as this offered the same stiffness at reduced weight. The design of the tubes also developed over time, tubes becoming of a larger diameter, but thinner walls, to allow the same stiffness with reduced weight.
Bicycles are fitted with various types of brake, the most popular being the calliper, cantilever, hydraulic or disc and the V brake. The most common form of brake found on leisure bicycles, is that form used also on road racing bicycles. The calliper brake. Calliper brakes are a very efficient means of rim braking and basically comprise two blocks of rubber or plastic which are squeezed onto the wheel rim when the brake lever is squeezed by the ride.
Cantilever brakes operate on the same principal as calliper brakes, but are of a slightly different design at the wheel end, offering increased clearance between the tyre and the brake pads and as such are frequently employed for cyclo-cross bicycles and mountain bikes.
The most efficient form of rim brake is the V brake. The V brake also offers the most clearance of any rim braking system, and is most often found on mountain bikes.
Hydraulic or disc brakes are the most efficient and powerful form of bicycle brake. They use the wheel hub to brake, rather than the rim. Disc brakes offer the most clearance, and as such are used on mountain bikes, but are also expensive to fit and maintain.
Bicycle wheels are generally of one of three types. The most common and traitional bicycle wheel is the spoked wheel, comprising a rim connected to the central bub by a series of thin metal rods known as spokes. Spoked wheels are light in weight. Less common than spoked wheels, but offering greater strength and durability at the expense of weight are mag wheels which comprise a rim attached to the hub by a few, thick solid plastic bars. Solid wheels, also known as disc wheels, are made from composite material or carbon fibre are very strong, stiff, aerodynamic and very expensive. They are rarely used except as rear wheels in time-trialing and track racing.
 Research Bicycle
 More pictures of Bicycle
In engineering, a cantilever is a projecting beam, truss, or bridge unsupported at the outer end; one which overhangs.
A spring is an elastic device for linking two objects together so as to allow of relative displacement between them, this being resisted by a force which increases as the displacement becomes greater. The most common forms of metal springs are the spiral - used chiefly for clockwork, helical - which are used to resist extension or compression in the direction of their axes, double spiral, laminated cantilever and laminated semi-elliptic.
Laminated springs are generally employed in vehicles. They are composed of a number of steel plates bound together at the centre or at one end, but free to slide over one another at other points. The length of the plates increases regularly to give the spring the shape of a triangle, or of two triangles set base to base. The plates are curved , so that they will be straightened by the greatest load they are called upon to carry. It is important in a laminated spring that all the plates are of the same width and thickness.
The most perfect form of spring is of air under compression, as it is infinitely elastic and has no limit of strength.
The McDonnell Douglas A-4 Skyhawk (Bantam Bomber) is an American single-seater carrier-borne and land-based light attack aircraft developed during the 1950s to the US navy's requirements for a turbojet successor to the Douglas AD-6 Skyraider. The McDonnell Douglas A-4 Skyhawk II is a low-wing cantilever monoplane powered by a Pratt and Whitney J52-P-408 turbojet providing a top speed of 1103 kmh and a range of 547 km fully laden. It is armed with two 20 mm Mk 12 cannon in the wing roots and up to 9,155 lb (4153 kg) of disposable stores can be carried on five hard points, one under the fuselage and two under each wing.
Research A-4
The Aeritalia G91 is an Italian single-seat light attack, close support and reconnaissance fighter developed to NATO operational requirements issued in early 1954, and first flown in 1956 (as the Fiat G.91). The Aeritalia G91 is a low-wing cantilever monoplane of metal construction powered by a Bristol Siddeley Orpheus 803 turbojet engine providing a top speed of about 1045 kmh depending upon model. The Italian version is armed with four 0.5 inch Colt-Browning M3 machine-guns, the Portuguese version with two 30 mm DEFA 552 cannon, both gun arrangements located in the sides of the forward fuselage. Up to 1500 kg of disposable stores can be carried on four hard points two under each wing.
A photographic-reconnaissance version of the G91 is produced as the G91R, and a tandem two-seater trainer version as the G91T.
Research Aeritalia G91
The Aermacchi MB 308 was an Italian two-seater light cabin monoplane of the 1950's supplied to both the Italian Air Force and supplied to the civilian market. The Aermacchi MB 308 was a high-wing cantilever monoplane of wooden construction powered by a Continental C85 or Continental C90 four-cylinder horizontally-opposed air-cooled engine providing a top speed of 197 kmh or203 k h respectively and a range of 760 km or 720 km respectively. A three-seater model, the Aermacchi MB 308G was also produced and a seaplane variant with twin floats fitted.
Research Aermacchi MB 308
The Aermacchi MB 320 was an Italian twin-engined six-seater aircraft of the 1950's. The Aermacchi MB 320 was a low-wing cantilever monoplane of mixed construction powered by two Continental E185 six-cylinder horizontally-opposed air-cooled engines providing a top speed of 300 kmh and a range of 1070 km. The Aermacchi MB 320 carried two pilots with dual controls and up to four passengers seated in pairs.
Research Aermacchi MB 320
The Aermacchi MB 326 is a series of Italian single-seat light attack and two-seater trainer aircraft that first flew in 1957 and entered service in 1971. The Aermacchi MB 326 is a mid-wing cantilever monoplane powered by a Piaggio Viper Mk 632-43 turbojet providing a top speed of 890 kmh and a range of 1040 km depending upon load.
The Aermacchi MB 326 is armed with two 30 mm DEFA 552 cannons in the lower sides of the forward fuselage and carries up to 2500 kg of disposable stores on six hard points, three under each wing. A South African version built under license is known as the Atlas Impala.
Research Aermacchi MB 326
The Aero-2 is a Yugoslavian two-seater primary trainer and army co-operation aircraft. The Aero-2 is a low-wing cantilever monoplane of wooden construction powered by a De Havilland Gipsy Major 10 four-cylinder inline inverted air cooled engine providing a top speed of 208 kmh and a range of 680 km.
Research Aero-2
The Aero-3 is a Yugoslavian two-seater primary trainer and army co-operation aircraft. The Aero-3 is a low-wing cantilever monoplane of wooden construction powered by a Lycoming six-cylinder horizontally-opposed air-cooled engine providing a top speed of 230 kmh and a range of 680 km.
Research Aero-3
|
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
©1993 - 2009 The Probert Encyclopaedia
Southampton, United Kingdom
|
|
|
Abbreviations
