Embedded Files
Students Learn About:
historical developments in transport systems
effects of engineering innovation in transport on society
construction and processing materials used over time
environmental effects of transport systems
environmental implications from the use of materials in transport
Students Learn To:
investigate the history of technological change related to transport and its impact on society
identify design features in the engineering of transport systems
describe the environmental impact of energy requirements for transport systems
analyse the impact of developments in transport systems on the environment
- historical developments in transport systems
Cycle Development
Cycle Development
The bicycle is an interesting machine to have developed. Prior to it, nothing existed that operated on the principle of balanced travel and it has only extended to the motorcycle. The car is merely a progression from the horse drawn cart, while the truck is a development of the old bullock teams. The bicycle, however, marked the beginning of a new style of transport.
Early Machines
Early Machines
The invention of the bieycle has been credited to a Frenchman, le Comte de Sivrac, who introduced his machine, the célérifere, at the Palais Royal Gardens (Jardin du Palais Royale), in Paris, in 1791. He put wheels on what had been a child's toy, the rocking horse.
The célérifère was renamed the velocipede or dandy-horse and efforts were made to improve the appearance by making it resemble animals such as lions, horses or evendragons. In 1816, a German, Baron Karl von Drais von Sauerbron improved the original velocipede by fitting a steerable front wheel, armrests, a padded seat and even a primitive rear wheel brake. His machine was called a draisienne and was still propelled by walking it along the ground. The draisienne became popular, especially in England, where it became known as the hobby-horse.
The method of human propulsion on the early machines was hardly ideal. The introduction of mechanical propulsion was sure to come. In 1821 an Englishman, Lewis Compertz, designed a rack and pinion (a cog meshing with a toothed rack) system so the arms could be used to assist the feet pushing along the ground. It was not a perfect solution but definitely an improvement.
Pedal Power
Pedal Power
A Scottish blacksmith, Kirkpartick Macmillan, developed a pedal drive in 1839. He used a pair of hanging stirrup pedals, attached to long arms, that connected to cranks on the rear wheel. It was similar in principle to the locomotive drive, with the backwards and forwards motion of the pedals converted into rotation by the cranks on the back wheel. Gearing was determined by the size of the rear wheel; the larger the wheel, the higher the gear. Macmillan's machine, sometimes called Macmillan's Velocipede, weighed just over 30 kg. It was archaic in concept and construction but it now enabled a rider to travel without having to push with his feet on the ground.
Rear wheel drive was not to become popular on bikes for a long lime The next stage of bicycle development was front wheel drive. In 1861 Monsieur Brunel took his draisenne for repairs to a coach maker, Pierre Michaux. Michaux's son, Emas, suggested that the machine could be improved by fitting cranks, with pedals on the ends, to the front wheel so that it could be pedalled.
By 1867, at the Paris Exhibition, this new bieycle, the velocipede (the cynics called it "boneshaker") had became, an established mode of transport. Michaux opened a factory and employed 300 workers to produce these bicycles. Soon three-wheeled. four-wheeled, tandem and even triplet versions of the velocipede appeared. Schools for riding sprang up, and organised races were introduced.
Lady cyclists on "boneshakers" were among the first women to cast skirts aside and appear in public showing stocking covered legs. "Bloomers" for cycling, based on baggy pantaloons were popularised by Mrs Amelia Bloomer in America. In 1874 Englishman James Starley, famous in the cycling world, patented the first 'lady's' bicycle. It was ridden side-saddle with one pedal. Starley also invented the spoke, radiating at an angle from the wheel hub.
The "Old Ordinary" (Penny-Farthing)
The "Old Ordinary" (Penny-Farthing)
As with the car the speed of bicycles has been something that has motivated new designs. The problem with the velocipede was that it moved along only one wheel circumference per turn of the pedals, because there was no variable gearing. Before gears, the solution was to increase the front wheel diameter so that, for each rotation of the wheel, the bike went further. Wheels became larger and larger with the only limitation being the length of the rider's leg. The new bicycle had a large front wheel up to 1.52 m (5 feet) in diameter and a small rear wheel. Released in 1870, it became known as the Old Ordinary or Penny Farthing (two British coins). In retrospect the Old Ordinary was not a particularly feasible design. It was unstable and when braking heavily it usually sent the rider over the handlebars. Descending hills was a thrilling, if not dangerous, experience as the pedals span wildly. To counter this final problem, footrests were fitted high on the front forks so that the rider could free his/her feet from the pedals. Although they were tricky to ride, they were the fastest things on two wheels until the chain driven safety' bicycle appeared.
The Safety Bicycle
The Safety Bicycle
Attempts to make the front wheel smaller, and therefore the bicycle safer, were defeated by the lack of a feasible solution at the time. A reliable bicycle chain was a major invention needed to develop a safe successor to the Old Ordinary. James Starley gave us the makings of the modern bicycle when he developed the Rover *safetv' bicycle of 1885. Starley had already designed a chain-driven bike for Rover in 1880. It had linkage steering of the front wheel, which was still larger than the rear wheel. His new design brought together some of the main elements of the modern machine: geared chain drive, wheels of equal size, direct steering, inclined forks, and the diamond-shaped frame. These safety bicycles were a vast improvement on the Old Ordinary. Not only were they easier to mount and ride, they allowed improved gear ratios, which made them faster but requiring less effort to ride.
Initially there was some resistance to the new design but another development was about to make the "Rover Safety" the number one design. In 1888 a Belfast veterinary surgeon, John Boyd Dunlop invented the pneumatic cycle tyre. Prior to this, all tyres were solid rubber. With pneumatic tyres the bicycle was more comfortable so the rider could travel even faster. Sensing the commercial value of this, Dunlop went into the tyre manufacturing business, and within a few years, the pneumatic tyre had completely replaced the solid tyre as standard equipment on bicycles and on the new inventions, cars and trucks. The Dunlop Company had become the largest in the tyre business.
Mass Production
Mass Production
By the late 1800s the bicycle had ceased to be a novel status symbol and was becoming a cheap and practical form of personal transport. Mass production of the bicycle began, and by 1914 the practical utility bicycle was being assembled from some 300 separate components. The majority of these were manufactured by specialist firms. Many cycle companies were the core of the fledgling automotive industry, for example Morris and Riley and Peugeot.
Up to the Present
Up to the Present
Through the 1900s bicycle frame design did not change a great deal. The frame angles were altered and different alloys were used to reduce weight. By the 1960's high strength, lightweight aluminum alloy frames were used and new gearing systems were developed. Nowadays we see very base end bicycles made from mild steel tubing, entry level road and mountain bicycles using aluminum alloys and high end bicycles now use carbon fibre reinforced polymers.
Big developments occurred in the 20" century with gearing and braking. By the 1990's the mountain bicycle had demanded wider range gearing and the simple 10 speed derailleur system expanded out to take in first 7 speed rear clusters with now 10 speed rear clusters being the norm for high end bicycles. Front derailleurs have remained two speed for most road bicycles and 3 speed for mountain and touring bicycles. Hub gears are rare in Australia but are used extensively on city and folding bicycles through Europe. Derailleur gear systems are more efficient than hub gears but require more maintenance. Currently the "fixie" is very fashionable, using only single speed chain drive, in a modern road bike frame.
Brakes have improved with cast aluminium alloys now allowing dual pivot calliper brakes with good braking performance and also lightweight for weight conscious road bicycles. Early mountain bicycles used cantilever brakes, which were predominately replaced by V brakes and now disc brakes; both cable and hydraulic discs are used on mountain bicycles.
Modern Bicycles
Modern Bicycles
Mountain Bikes
Mountain Bikes
Initially the term "mountain bike" was marketing exercise; simply a standard diamond frame bike that had been more heavily constructed to stand up to off road riding. Mountain bikes typically have smaller wheels than road bicycles (ETRTO 559 mm) with knobbly tyres. Such tyres are not ideal for road riding because of the high rolling resistance. However entry-level mountain bicycles have become the bicycle of choice for recreational cyclists. These typically use aluminium alloy frames (such as 7000 series). High-end mountain bicycles are popular with off road riding and various competitive events exist for such cycling. Here carbon fibre reinforced frames dominate.
Road Bikes
Road Bikes
The modern road bicycle typically uses an aluminium alloy frame for entry-level bikes and then carbon fibre reinforced polymers moulded frames are used with more expensive models. They have large diameter (ETRTO 622 mm) but narrow wheels and tyres. Road bicycles rely on some flex in the frame to provide improved pedalling response and some release from road vibrations, but require rigidity as well so pedalling forces are not lost. Originally steel and alloy steel frames offered this perfect compromise, but desire for lighter weights led to aluminium alloys which tend to have less flex because aluminium alloys have no definite fatigue limit so frames are built with little or no flex. Carbon fibre reinforced polymers offer the ride of steel but are lighter than aluminium alloys so they are now the frame material of choice. Although their durability in terms of long-term ownership is questionable.
Moulton Bikes
Moulton Bikes
Alex Moulton's bicycles pioneered the use of small wheels with high-pressure tyres. Prior to this small wheel bicycles were simply children's bikes. Moulton proved that small wheels with high-pressure tyres were the equals of large wheeled bicycles. However they had a rougher ride so he fitted suspension as well. Moulton bicycles were very popular in the 1960s but as the craze waned Moulton moved into high quality small volume bicycle production and his designs now use a complex stainless steel space frame design, which is light, strong but quite expensive.
Folding Bikes
Folding Bikes
There are a wide variety of bicycles that took the small wheel concept pioneered by Alex Moulton and developed them into bikes that can fold for easy commuting and transport. One of the best examples of a folding bicycle is the Brompton bicycle. Within 20 seconds a Brompton can be folded to a package less than a quarter its original size. Although the Brompton is clearly designed with city riders and commuters in mind, its devotees have toured all over the world on them.
Recumbent Cycles - Or Riding Reclined
Recumbent Cycles - Or Riding Reclined
The concept of the recumbent bicycle (and tricycle) is a sound engineering principle. The human body is not really designed for the arms to support a person's weight. Yet the common or upright bicycle requires that part of the body weight is supported by the arms. The bicycle saddle, developed many years ago, is not designed to support all of the rider's weight. If one sits vertically, without putting weight on the arms, the bottom will soon get sore.
Recumbent Bikes
Recumbent Bikes
The recumbent bicycle is one solution. The larger, more comfortable seat, has a backrest and is reclined like a car seat. The pedals are out in front. The rider's arms carry no weight. A softer, larger seat makes for greater comfort and lower frontal area because it is reclined. The machine is more aerodynamic and finally, if the rider falls off, he/she has less distance to fall. Conversely they are heavier, more costly, and harder to balance, especially initially. The world of recumbent bicycles is highly diverse and covers many different styles, materials and manufacturing methods.
Recumbent Tricycles
Recumbent Tricycles
The upright tricycle is primarily a child's toy or a load carrier. With the high centre of gravity they have a tendency to roll over. One of the disadvantages of a bicycle is the need to balance it and the rider must allow the bike to wander slightly from side to side in order to maintain balance. The tricycle is a solution to this, but, it is highly susceptible to rolling at moderate speeds. The recumbent tricycle has a low centre of gravity so rolling is far less of a concern, and there is no balance issue. Because of their extra mass, tricycles tend to be a slower on hills but on the flats and downhill they are equally as quick as any bicycle. They can also corner as quickly as any bicycle. Being low, means that they have an aerodynamic advantage in head and cross winds. They are better in wet conditions than the bike because their design makes them more stable when cornering. But they are heavier and more costly than an equal quality upright bicycle.
Train Development
Train Development
So far, all of our forms of transport have been personal transport. We shall now turn our attention to a public transport system. In the following section some important developments in trains will be discussed. From the 14' to the 18th centuries the train was in use but horses powered it. Many wagons were hauled up out of mines using "pit ponies", and this practice continued in Australia until the 1950s. Originally rails were timber but iron rails were introduced in 1728 in England. In 1803 the first public railway was opened for hauling freight; it was just over 15 km long and ran from Wandsworth to Croydon in Southern England. This was followed in 1806 by the first public passenger line with a horse-drawn train in South Wales. In Australia the very first railway was in Tasmania and was actually convict powered. The train ran on rails, but instead of a steam engine, the convicts ran alongside the train, pushing it.
Guages to be wide, or not be wide; that is the question!
Guages to be wide, or not be wide; that is the question!
Gauge refers to the distance between the tracks. By the 1830s it was a hotly contested issue. Originally the gauge of lines was 4 foot 8½ inches, or approximately 1.44 m. This odd size came about, as that was the gauge of the lines that coal mines used with the wagons pulled by pit ponies. There is also some evidence that this strange size dates back to the distance between the wheels of Roman chariots. All railway engineers simply used this accepted gauge, except Isambard Kingdom Brunel. We discussed Brunel's bridge designs in Chapter 1. He was responsible for the Great Western Railway (GWR) in England. Brunel felt that a wide gauge of 6 feet (1.83 m) offered distinct advantages, and he was right. The wider gauge makes a train more stable and less likely to roll, as its wheels are further apart. It does, however, make tight curves even more difficult.
Unfortunately he was the only person to adopt this gauge and as more railways sprang up around England it became clear that the wide gauge days were numbered. In Australia, the eastern states could not agree on the gauge for their railways. NSW used the standard 4'8½" (1.44 m) gauge, while Victoria used a S'2" (1.57 m) gauge and Queensland used a narrow 3'6" (1.07 m). This ridiculous mismatch was only rectified in the 20' century, when the gauges in Victoria and Queensland were adjusted to the NSW standard.
Steam Trains
Steam Trains
Steam Trains
Steam Trains
In 1803 the very first steam locomotive was constructed by Richard Trevithick for the Coalbrookdale Ironworks. He built a second locomotive the following year and it was apparent that this machine could do more work than a horse at a speed of 8 km/h. Trevithick used his high-pressure steam engine as opposed to competing atmospheric steam engines that were used for driving pumps and machinery. This heavy locomotive, however, broke up the rail line, so it was abandoned.
In 1812 the first locomotives to conduct regular work were designed by John Blenkinsop, for a colliery in Yorkshire. They differed from current trains as the wheels and tracks had interlocking teeth. Blenkinsop felt that smooth rails would slip too easily. Trevithick had proved this was not the case, but Blenkinsops's system was to reappear, in a modified form, for mountain railroads.
George Stephenson, a mine mechanic, invented a locomotive in 1814, and it was to be the first step in his work of developing railways. Stephenson was a railway man through and through. He envisaged a railway system criss-crossing the country, carrying freight and passengers alike. In 1823 he was appointed as the engineer to the Stockton and Darlington railway. This 16 km line ran from a colliery to the port of Stockton-on-Tees, and was opened in 1825. His locomotive, Locomotion, was designed with his son, Robert. It was the first locomotive to haul on a public line and was capable of speeds up to 25 km/h.
Stephensons' Rocket is a famous locomotive and it had an immense impact on locomotive design. The future of profitable railways rested in providing quick passenger transport; something that was previously unavailable. In 1829 a series of trials were held to determine the best locomotive design. George and Robert Stephenson entered their Rocket, which had an innovative boiler design; 25 tubes carrying water ran through the firebox, more efficiently creating steam. Along with an improved exhaust system, The Rocket was twice as fast as rival designs; it could pull a 14 tonne train at 46 km/h.
The Rocket started an epoch in train design. From that moment, rail transport expanded, as it offered speedier transport than horse-drawn services. Naturally the challenge was to get trains to go faster and faster, but along with such increases in speed came difficulties in stopping the vehicles. Mechanical brakes were difficult to use, but in 1869 George Westinghouse patented an air brake design that was to become widely used. Operation centred on the brakes being held off by the air pressure. When the air pressure was released the brakes were applied. This made it safer if the train lost its air pressure, than if the system operated in the reverse fashion.
Another big advance in steam locomotive design was the development of the compound steam engine developed by Anatole Mallet in 1876. Instead of used steam merely being given off, it was first used in a small cylinder, then used in a larger cylinder, so the steam was used twice. Following "compounding", there was superheating, which was initially adopted in Germany in 1898. The moisture content of the steam produced by the boiler was reduced by increasing the temperatures, hence increasing the efficiency of the motor.
If one looks closely at railway design one may notice that railways neither are very steep, nor do they have very tight curves. Tight curves are difficult for trains to negotiate, while steep grades mean they lose traction. While cars can comfortably, even if a little slowly, ascend a grade of 1 in 6, trains are lucky to climb grades higher than 1 in 25. The solution to both of these problems is to produce large sweeping curves and to use tunnels and cuttings to pass over hilly terrain.
The standard steam locomotive has one or two large driving wheels, with many smaller wheels that are carried as pivoting bogies to balance the train at front and back. The train often carries a tender carriage behind it containing water and coal, which has no drive wheels under it. The problem with this is that a lot of the weight is not carried over the drive wheel, so on steep grades, the wheels will slip. Two types of locomotives that avoided this were the Garret and the Shay.
The Garratt locomotive was made in three articulated parts: the middle was the boiler and cab while the front and back carriages were the tenders for water and coal respectively. Unlike other trains, the bogies on the tenders were driven, so there were more driving wheels and therefore less chance of wheel spin. Garratt locomotives were very large, yet could deal with tight curves. The main disadvantage was the wear on the pipes that carried steam to the tenders at either end.
The Shay locomotive was a truly fascinating design. The boiler is offset to the left side of the locomotive to allow a set of three vertical pistons on the right hand side. These pistons moved up and down and were connected to a crankshaft that ran along the right hand side of the locomotive. Mounted to the crankshaft were pinions that engaged with bevel gears on every wheel. This meant that every wheel was a driving wheel, as the left side wheels were connected to the right hand wheels by axles. The crankshaft had to have universal and sliding joints to allow the bogie to turn, and the tender also had drive wheels underneath to improve traction. The main advantage was that each wheel was driving so wheel spin was less likely, and it was designed to deal with tight curves. The disadvatage was that the design was slow, with a maximum speed of 25 km/h and it sulfered a lot of wear in the universal and sliding joints.
four Shay locomotives were used in NSW on a privale railway line that ran into the Folgan Valley to ferry refined shale oil from the refining plant: At the time of operation (1909-19 1s then interittently up to 1932), rail transport was the only option available for freight, it was also the main source of income for the residents of the township of Newnes, now a ghost town. The railway was a miraculous feat, with Tight curves and I in 22 grades and only two tunnels. Although the line is gone it is possible to walk along the old track that was the line. One tunnel is now a home to glow-worms, a tourist attraction for the Lithgow area.
Electric Trains
Electric Trains
The first real challenge to the dominance of steam was the electric train. With reliable electric motors and power stations, both available by the 1880s, electric trains were a viable option to steam. One clear advantage was that they were less polluting. The power station still polluted but it was away from the rail line and was much more efficient in converting coal to the power source (electricity) than a large number of steam engines They were also quieter. The disadvantage is that they need infrastructure in place to provide power, because an electric train cannot use just any
The first electric train design was shown by Werner von Siemens at an 1579 Berlin exhibition, and by 1883 public electric lines were opened. The electric train offered great advantages with its underground rail lines. This was an answer to congestion in cities. In 1890 the first electric underground railway was opened in London and it has since become an essentiat art or the City's transport. In Sydney the underground stations of Museum and S. James were opened in 1926. Town Hall and Wnyard stations followed in 1931, and with the completion of Circular Quay station in 1956 the City Circle was created. In the London Underground, electric trains were essential. Electric trains have been used on suburban railway lines since the late 1920s in Sydney, while outlying areas like Wollongong, Newcastle and Lithgow did not gain electric trains until the 1980s.
Electric trains need to have power provided. In NSW, the power is provided by copper, overhead wires. Some of the trains' carriages have a pantograph that is connected to the electric motors that run along the overhead wires. In other situations, a third rail, between the other two, is used to provide power. Without these systems, the electric train cannot run, but with them they are a viable option. Many goods trains in NSW are pulled by electric locomotives. It is important to emphasis that electric trains do not stop pollution; they merely move it from the city to wherever the power station is located.
Diesel Trains
Diesel Trains
The diesel train is the true successor to the steam train. Electric trains ran alongside steam trains in the cities but they could not service outlying areas. The first diesel train ran in 1912 in Germany, but the future for diesel trains lay in the diesel electric arrangement, where a diesel engine drives a large generator that uses electricity to drive electric motors at the wheels. This is a far better system than a gearbox, for large power delivery. Another system uses hydraulics to connect the motor and wheels and this is called a diesel hydraulic drive. A diesel motor drives an hydraulic pump which creates high pressure oil in pipes. The pipes feed hydraulic motors, mounted on the wheels.
By the 1960s in NSW, diesel trains were becoming widespread and by the early 1970s the steam train was gone. Diesel electric trains are extensively used for long distances. In NSW, for example, the diesel electric system is used on the XPT rail services and it is extensively used when hauling freight. Two large diesel electric locomotives haul the Indian Pacific that runs from Sydney to Perth. The Explorer and Endeavour passenger trains, in NS W, use a diesel hydraulic system.
- effects of engineering innovation in transport on society
Cycles
Cycles
The pedal-powered velocipede, 1839, greatly improved the usability of the bicycle.
Old Ordinary (Penny Farthing) - faster transport than the velocipede but dangerous to ride
Rover Safety Cycle, 1885 - safer transport with similar speeds
1888 - Dunlop's pneumatic tyres
Early 1900s - mass production of the bicycle
Freewheeling hubs made cycling far safer for riders
Internal hub gearing - improved bike as a form of transport
High strength steel alloys, such as Reynolds 531 - bikes became lighter.
Recumbent bikes - better comfort but outlawed from racing - stalled their development
Lightweight aluminum alloys & reliable derailleur gears - improved traditional design of Safety Cycle.
After WWII - cycle usage declined as cheap cars available - subsequent pollution not much considered.
Suez oil crisis, 1950s - forced many people back to bikes - cycle development took off again
Moulton bike sparked cycling craze in UK - suited image of the swinging sixties.
BMX (Bicycle Motor Cross) - small wheels - off road racing - popular with children
1980s - rise of the mountain bike - grew into the most popular bike - many specialised components developed.
Recumbent bikes and trikes grew in popularity in the 1990s to create a niche market - good for long-distance touring - easier on the body.
1990s and on - more exotic materials - greater weight savings - improved performance.
2010 On - resurgence in cycling as a popular recreational sport in western societies.
Trains
Trains
Steam train - 19t century alternative to the horse and cart for transport.
Railways systems developed world-wide, 19' century - ability for people to travel across country for first time- meant a boom for many small towns.
Electric trains, 20 century, in urban environments, reduced pollution compared to steam trains.
Train, important tool in WWI and WWI - supplies, movement of troops.
After WWII, diesel train started to appear - by 1960s starting to replace steam less pollution, greater reliability, quicker times
More electric rail networks - further improvement of air quality.
High-speed trains greatly cut transport times, e.g. English Channel Tunnel train faster from London to Paris than plane.
Today, some see well-designed electric trains and light rail systems as answer to traffic congestion.
- construction and processing materials used over time
Timber
Timber
Timber was used in early bicycles because of a lack of suitable alternative materials. Frames were made from timber pieces that were shaped, while timber was also used for wheel construction.
Iron
Iron
Iron was used initially as a tyre on wooden wheels and in early frames, but it was replaced by steel frames and rubber tyres.
Steel
Steel
This was produced in large, cheap quantities after Henry Bessemer developed his converter in 1856. From this point, cycle frames began to use steel construction and by the 1870s steel wheels with thin steel spokes were used. Steel tubing offered good strength with a relatively low weight. Although not as light as some materials, tubing was lighter than solid rods. Cold drawn steel tubes offered the best strength for cycle frames.
Usually steel frames were joined by brazing with lugs. The lug was a small joint piece into which the tubes slid. They were then brazed in place. Only cheaper frames were welded. With newer welding techniques, however, most plain carbon steel frames are welded.
Steel was used extensively in brake and gear construction up to the 1970s when aluminium alloys started to encroach, in an attempt to save weight. Steel is still extensively used in chains and gear clusters and on many cheaper bikes all components are steel, because it offers reasonable strength, ease of fabrication and it is cost effective.
The term alloy steel refers to steels with deliberately added materials in addition to iron and carbon. Reynolds 531 was a manganese-molybdenum steel that offered a better strength to weight ratio than plain carbon steel. It was first introduced in 1935. Reynolds 531 was used in racing bikes for many years.
Chromium-molybdenum steels are also used and these once again offer superior strength to weight ratios than do plain carbon steels. Whereas Reynolds 531 was really only suitable for brazing (with lugs), chromium-molybdenum (called Cro-Mo) steels can be welded. With modern production techniques, this is an advantage, as the TIG and MIG welded frame is quicker, lighter and cheaper to fabricate than a brazed steel lug frame.
Reynolds and True Temper have released air hardening steels such Reynolds 631, 853 and True Temper OSX. The problem with welding or brazing a tube of steel that is cold rolled is that, around the weld joint, the steel is annealed and softens. Air hardening steels harden in still air to maintain strength around the welded joint. The result is an extremely strong frame with strength to weight ratios approaching many aluminium or titanium alloys.
Stainless Steel
Stainless Steel
This high alloy steel was not typically used for frame construction, excepting for some Moulton bikes, but is now offered for frames in the form of a martensitic ageing stainless steel, with Reynolds 953 being an example. This stainless alloy offers UTS values up to 2000 MPa. Stainless steels are also used in the manufacture of components such as cables and pins for brakes and gears. Its corrosion resistance makes it quite desirable for these applications.
Aluminum Alloys
Aluminum Alloys
These are now widely used in cycle construction. Reynolds offers a 6061 alloy (heat-treatable Al/Si/Mg) and a 7005 alloy (heat-treatable Al/Zn). 6061 offers excellent corrosion resistance and is more workable than other heat-treated alloys. 7005 offers greater strength but greater density than 6061. Aluminum is light but considerably weaker, so tubes are often not circular but oval, to increase the resistance to bending. Aluminium must be welded, usually using Tungsten Inert Gas (TIG) or Metal Inert Gas (MIG) methods, and offers the advantage of being relatively corrosion resistant.
Aluminium alloys are also used in the manufacture of brake and gear parts because of their lightweight nature. Brake levers and arms, derailleurs and hubs use aluminium alloys.
Titanium Alloys
Titanium Alloys
To a lesser extent than aluminium alloys, titanium alloys, such as 3% Al/2.5% V/Rem. Ti are finding favour in cycle manufacture, not just in frames but also in gear componentry. Titanium components and frames are usually very expensive and in frames, at least, they offer little over steel alloys like Reynolds 953, or carbon fibre reinforced polymers. Titanium must be welded using the TIG method and this must be done very carefully or there may be weld cracking.
Titanium sprockets offer a viable alternative to steel cogs but they come at a high cost and, as such, are only used on the best racing bikes.
Carbon Fibre Reinforced Polymer (CFRP)
Carbon Fibre Reinforced Polymer (CFRP)
Carbon fibre reinforced polymers are a desirable alternative to aluminum alloys or alloy steel frames. They have an excellent strength to weight ratio that is very suitable on racing bikes. The frame is usually moulded in parts and then is fabricated together using a suitable adhesive.
CFRPs are tough, strong and stiff. When they fail, however, failure is sudden and often catastrophic, with little or no plastic deformation to warn of imminent failure. CFRPs have become the material of choice for all mid to high-level road bicycles and high-end mountain bicycles. They are also finding use as parts such as cranks, seat posts and handlebars.
Rubber
Rubber
This material was partly responsible for the growth of cycling. Solid rubber tyres were used to replace iron tyres. It was lighter and provided moderate springing. In 1888, John Boyd Dunlop developed the pneumatic tyre that made cycling even more pleasant. Today, synthetic rubber is still used in tyre construction. Rubber has also been used for suspensions on bikes. On Moulton bikes it is used for both rear and front suspension. It has the advantage of being light and also being self-damping, so no damper (a.k.a. shock absorber) is needed.
Polymers
Polymers
Polymers are greatly used in the manufacture of cycles and they have found use in applications where their flexibility is a great advantage. Polymer sheaths are placed over cables, and are also used in pedal construction. They offer flexibility, are lightweight and show good resistance to deterioration caused by the weather and UV light. They are also used in cycle lights and finishing pieces.
- environmental effects of transport system
Cycles
Cycles
Cycling is often looked on as one of the many solutions to environmental problems such as pollution and the greenhouse effect. Cycling, as a form of transport, is one of the most efficient ways to travel; that is, the energy expended is used more usefully than many other forms of transport. It is non-polluting and human power is a renewable energy source.
It is perhaps not as popular as it should be as many adults abandon cycling once they get a driver's licence and the weather becomes a major issue for travel. Many people also fear riding on roads because of the dangers posed by motor vehicles, drivers who are unsympathetic to cyclists, and the absence of good cycle paths.
Trains
Trains
Trains have also had negative impacts on the environment. The construction of railways has resulted in tree felling and the levelling of land. Many railway lines also incorporate tunnels and cuttings which, when blasted, can have an adverse impact on the surrounding areas.
Steam trains produced excessive pollution, with an efficiency of only 5 to 10 %. In many developing countries steam engines are still used but run on oil which produces even more smoke than coal did previously.
Electric trains also cause pollution, as the electricity must be produced somewhere! In NSW, that is usually in coal power stations, which are major contributors to the greenhouse effect. The electric train, however, does take the pollution away from urban areas where air quality is always a problem.
Diesel trains, although more efficient than steam trains, still pollute. Newer diesel locomotives, however, emit less smoke than the older ones, and modern computerised engines ensure minimum pollution for maximum power.
For passenger and freight transport, however, trains are better environmentally than road vehicles. Railway lines are narrower than freeways so have less of an impact, and they can haul many people or goods without congesting roads. Electric railways can move vast amounts of people in the city without pollution or traffic congestion.
- environmental implications from the use of materials in transport
Timber
Timber
Forests have been greatly affected by large scale transport developments. Timber was used for railway sleepers and as a fuel source for some steam locomotives. Such uses resulted in the clearing of large areas of forest. We are now feeling the legacy of this with global warming and local climate change. The removal of these forests has also had an impact on native fauna by reducing their habitat.
Steel
Steel
Steel has been the main transport material since 1856. It has found use in both plain, carbon and alloyed forms in all types of transport. The thirst for steel has seen the establishment of large steelworks, such as those at Port Kembla (NSW), which often affect the local atmosphere with the large amount of pollutants produced in working and refining the steel. Steel production requires large amounts of iron to be produced, which means iron ore must be mined. These mining operations are usually open-cut mines which involve large open pits with machinery digging down to extract the ore. As well as iron-ore, coal and limestone, are needed for the fulling of the blast furnaces to produce the iron. Coal also has to be mined and refined to coke.
Cast Iron
Cast Iron
Cast iron has had a similar impact to steel but is used to a lesser extent nowadays. Essentially similar metallurgically to the iron from the blast furnace, it still requires vast amounts of iron-ore and coal and coke.
Aluminium
Aluminium
Aluminium has increased in use greatly in the last half of the 20" Century. Like iron, it is refined from an ore, bauxite, which is mined in an open cut manner, also affecling the local landscape and environment. Aluminum is refined from the ore using electricity, which in Australia, primarily comes from coal-fired power stations. The use of coal greatly contributes to greenhouse gases and as a result has a detrimental effect on our atmosphere. Aluminium refining also produces fluorine gas, a major polluter in the past, which is now controlled from reaching the atmosphere.
Polymers
Polymers
]Polymer usage in transport systems has exploded since WWII, because polymers offer lightweight transport machinery which improves fuel efficiency. To protect the environment, the extensive use of polymers must be backed up by the recycling of old equipment, as polymers greatly contribute to landfill.
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