THE TRANSMISSION SYSTEM
The transmission system carries (transmits) the movement of the crankshaft to the wheels. It has three main parts: the change gears; the clutch; the rear axle gears. A gear is only a strong steel wheel with teeth. If a small gear with 25 teeth turns twice, it will turn a gear with 50 teeth once. This is a low gear. If a large gear with 50 teeth turns once, it will turn a gear with 25 teeth twice. This is a high gear. Gears can have as many teeth as are needed. The crankshaft of a car engine can turn as fast as 6,000 times a minute. One turn is a revolution. So that is 6000 revolutions per minute (rpm). This speed is too great to transmit straight to the wheels. It is made less by two things:
1. The change gears.
2. The differential gears in the back axle.
The change gears
In the gearbox there are three shafts: 1. the driving shaft is turned by the crankshaft. It has a fixed gear wheel near its end. 2. The driven shaft leads to the back axle. On this shaft there are two gears. One gear is larger than the other. These gears can move along the shaft in grooves. They can move backwards and forwards. They are moved by the gear lever. 3. The lay shaft. Four gears of different sizes are fixed on this shaft. The largest always meshes with the gear on the driving shaft. So, when the engine is running the lay shaft must be turning. It must also turn more slowly than the driving shaft. Its gear is larger. The gear box is about half full of oil.
First of bottom gear
First gear: The large gear on the driven shaft meshes with the smaller forward gear on the lay shaft. The engine is running fast but the driven shaft and the wheels turn slowly. This gear is used to start the car moving.
Second gear: The smaller gear on the driven shaft mashes with the second largest gear of the same size. The one on the lay shaft is only a little smaller. This gear is used to increase the speed of the car.
Top gear: the driving shaft joins straight on to the driven shaft. The car is now moving very fast. There is little difference between the engine speed and the speed of the wheels. If the car has to slow down, the driver will have to change to a lower gear.
When the brake pedal is pushed down, it forces oil (hydraulic fluid) through small pipes. These pipes lead to the brakes. A drum is fixed to each wheel. This goes round with the wheel. The fluid forces the brake shoe to rub against the drum. There are also disc brakes. A metal disc is fixed to each wheel. The fluid forces a pad to rub against the disc. The friction between the brake shoe and the drum, or the pad and the disc, slows down the wheel.
Springs on the axles give a smooth movement to the car body. Two kinds of springs are used. They are leaf springs and coil springs. Leaf springs are unusually on back axles. Coil springs are on front axles.
Shock absorbers filled with oil also help. These go in and out telescopes.
When the vehicle goes over a bump, the spring compresses and expands and will continue to compress and expand several times before returning to its original position. A similar action is seen when a rubber ball is dropped on the floor. This additional action is undesirable and results in an uncomfortable ride. To reduce this additional action shock absorbers are fastened between the axle and the frame. Most late-model shock absorbers consist of a telescoping tube partially filled with a fluid that can pass through a restricted passage from one part of the tube to the other. When the tube is compressed or expanded, the fluid causes a showing down action on the telescoping tube.
The steering is the mechanism by which a car can be guided along the road and steered in the direction the driver wishes to travel.
Each front wheel is mounted, on a “stub” axle which is able to swivel on a nearly upright spindle called the “king-pin”. Fitted to each stub axle is a short lever known as the “steering arm”, the two steering arms being connected together across the front of the car by a “track-rod”.
Projecting from the steering box” is a short lever called the “drop arm”, and this can be connected to the off-side wheel (the wheel on the driver’s side of the car) by means of a “drag-link”, or directly to the track rod as shown in the illustration.
When the driver turns the steering wheel, mechanism in the steering box causes the drop arm to move forward or backward. This movement results in the movement of the steering arm and the turning of the road wheel. The steering usually operates directly on the offside wheel, the track rod making sure that the other wheel exactly follows the movement.
Many cars are fitted with an alternative method of steering called “rack and pinion”. This is very efficient, but unless care is taken in the design, road jolts can affect the steering.
1. Work in small groups to have the following meeting:
You work for a car manufacturer. You are meeting your colleagues to discuss closing the gap in the range of cars you offer. At the moment your product range consists of a compact, a large van and a convertible.
The possibilities for the new model are:
· A small “green” car (a compact car with extremely low fuel consumption)
· A roadster (a fun, “good weather” car for everybody, young and old)
· An SUV (a versatile on-road / off-road vehicle with lots of room)
· A limousine (a long, roomy car with mini bar and fridge)
· A hatchback(a rear door including the back window that opensvertically)
· A minibus (designed to carry fewer people than a full-size bus)
ALUMINUM – THE METAL OF THE YEAR
With the launch of the A2, Audi AG introduced the first vehicle in the world to have a volume-built all-aluminum body. In 1996, series production of the A8 began. The A8 is the first luxury limousine made of aluminum and the Audi plant produces 20 000 vehicles a year. The A8 combines high strength with low weight. This is the lightest car in the luxury class. The third-generation Audi Space Frame now has fewer components than its predecessors, which makes it easier to build the car in large quantities.
Other car makers are also starting to take aluminum seriously. As engine sizes have increased, cars have become more top-heavy. Using aluminum for the bonnet and front wings helps to get a better weight distribution between front and rear axles. Another advantage of aluminum is that it is cheaper to recycle than steel. This will be an important consideration in the future when the EU introduces tougher recycling regulations.
But there are drawbacks to using aluminum. Replacing steel with aluminum is expensive; an aluminum body costs twice as much as a steel one. Not only are production processes expensive, they are also difficult to implement. Because aluminum is more brittle and tears more easily than steel, it can only be formed when it is in an unhardened state. Furthermore, aluminum used for the outer parts of the car, such as the wings and the doors, needs to be thicker than steel because it doesn’t have the same stiffness. The dent-resistance of aluminum is also less than that of steel. On the plus side, aluminum doesn’t rust like steel, and in car crashes it has a higher energy absorption rate, which increases the car’s active safety.
2. Complete the sentences about materials with words given below :
Shatterproof, light, corrosion-resistant, durable, elastic, natural, rigid, flammable, malleable, heat-resistant.
a) Wood is very often used in interiors because it looks _______ and warm.
b) Aluminum and magnesium are important for car makers because they are _______ and therefore good for weight-saving.
c) Safety regulations require that the foam used in car seats shouldn’t be _______.
d) Rubber should be able to withstand great temperature differences while staying _______. In other words, it shouldn’t become brittle.
e) Windscreens are made of a special _______ glass to protect drivers in accidents.
f) Fabrics used in cars need to be _______ and not look old too quickly.
g) Steel is used for load-bearing parts because it is _______.
h) Sheet metal is used for large car parts because it is _______ and dent-resistant.
i) Ceramic, which is _______, is used in the catalytic converter because of the very high temperatures.
j) Aluminum is ideal for bumpers and other body parts because it is _______.
3. Translate this extract in written form:
Vehicle bodies are made from a wide array of materials, including steel, aluminum, metal alloys, fiberglass and plastic, with each material requiring a different repair technique. Most repairers can work with all of these materials, but as car manufacturers produce vehicles with an increasing proportion of lightweight fiberglass, aluminum and plastic parts, more repairers specialize in these specific materials.
Collision repairers frequently must remove car seats, accessories, electrical components, hydraulic windows, dashboards and trim to get to the parts that need repair. If the frame or a body section of the vehicle has been bent or twisted, frame repairers and straighteners can sometimes restore it to its original alignment and shape. This is done by chaining or clamping it to an alignment machine, which uses hydraulic pressure to pull the damaged metal into position. Repairers use specialty measuring equipment to set all components, such as engine parts, wheels, headlights and body parts, at manufacturer’s specifications.
1. Read and discuss the following passage. What do you know about traffic rules of our country? Do you obey them?
If you have heard that driving in central London is difficult, just wait till try to find somewhere to park. Of course, it would be a little bit easier for you to park if you have Smart or Mini. But there is one more problem, except spare room for parking. If you park illegally or run over time on your parking-meter, you will get a parking ticket on your windscreen, demanding a fine. Even worse, your car may be immobilized by a wheel-clamp; follow the instructions to the Payment Center, where you must pay 38 pounds to get the clamp removed, plus a parking fine. You may have to wait several hours to recover your vehicle. For serious parking offences, vehicles may be towed away and impounded. To retrieve your vehicle you have to go to a Payment Centre and pay a 105 tow-away fee and 12 storage for each day your car has been kept in the pound.
Over the last years people have got used to the sight of very small cars parked in tiny parking spaces. Smart is one of the world’s youngest car makers and yet the Smart Fortwo is such a distinctive car that it has already been included as an exhibit in the Museum of Modern Art in New York – one of only six cars to attain this distinction.
In April 1994, the Micro Compact Car AG was founded in Switzerland as a joint venture between Mercedes-Benz and Swatch. Nicolas Hayek, the inventor of the Swatch watch, brought his idea for an ultra-short small car and Mercedes-Benz contributed expertise and experience from more than a hundred years of building cars. Engineers devised a car which is not only extremely mobile and efficient, but also very economical. Its other key feature is safety, with its unique tridion cell.
After starting development, the Smart Fortwo celebrated its premiere at the Motor Show in 1997. Production in Hambach, France, started in 1998, and sales took off in other European countries. There is no doubt that it is a leader in urban mobility. All Smart vehicles embody the same brand values and have the same ‘DNA’: innovation, functionality and joie de vivre. They appeal to people who are sporty, independent and young at heart; people who love clever solutions and are open to new ideas.
2. Answer these questions:
a) What are the advantages and disadvantages of the Smart?
b) In which countries do you think small cars are most successful?
c) Do you think small cars will become more popular in the future? Why?
3. Complete the table:
Airbag, speedometer, headlight, petrol cap or flap, sunroof, sill, ashtray, wheel arch, cigarette lighter, dashboard, wheel trim, logo, windscreen wiper, wing, aerial, boot, gearstick, number plate, glove compartment, rear window, handbrake, horn, ignition, wing mirror, rear-view mirror, seat belt, rear light, steering wheel, sun visor, engine oil temperature gauge, fuel gauge.
4. What car parts are made of what materials? Pay attention to glass, leather, plastic, rubber, steel, textile, wood and others.
Work in groups of three to have a role-play meeting. You have to decide whether the tailgate of a new car should be made of steel or plastic. Take the parts of a controller (A), a member of the technical department (B) and a member of the production department (C). Try to reach a decision by the end of the meeting.
6. Read “The Mini Story”. Which three paragraphs are from the same article and which one is from a fashion magazine? Put the paragraphs from the article in the correct order.
7. Answer these questions:
a) When was the first Mini made?
b) Why is the Mini factory in Oxford so special?
c) How many new Minis are made each year?
d) How many people work at the Mini factory?
e) Why is the new factory better for the workers?