Transmission of power in automobile

The power from the engine to the drive wheels is transmitted through the transmission which is composed of the following mechanisms: Clutch is a device which permits the engine to be connected with, or disconnected from, the transmission mechanisms, so that the car may, or may not, move while the engine is running.

Gearbox is a mechanism regulating the motive power of the engine, which is transmitted to the drive wheels of the automobile.

Through drive shaft power is transmitted from the engine to the rear-axle. It is located between the gearbox and the rear-axle.

Differential is the device that permits the rear wheels to revolve at different speeds independently one of the other.

Front-axle and rear-axle suspensions serve to support the automobile.

The front suspension of a car carries about 80% of the weight of the engine, and must at the same time withstand the shocks and jerk jars that it receives through the steering wheels; it must, therefore, be strong and stiff. It also carries about 20 to 40 percent of the weight of the entire car.

The center of the axle is bent down, so that it is the lowest point of the car except the wheels. This is done in order to protect the mechanism from being struck by high spots in the road. A rock or a stump, standing up high enough to hit the flywheel, will first strike the axle which is strong enough to withstand a blow that could easily damage the engine.

The steering spindles are that part of the front axle on which the front wheels revolve. They are made of nickel steel, heat-treated. The steering spindles are fitted with either roller or ball bearings. The steering knuckle is that part which fits into the joke of the axle.

There are two types of rear axles: "dead axle" and "live axle". The rear axle carries from 60 to 80% of the car weight. Dead axles are stationary, with the wheels running free on the ends of the axle. Live rear axles is the name given to axles that revolve with the wheels, and are known as "plain" live axle, "semi-floating" axle, "three-quarter floating" axle, "full-floating" axle. The axle shafts on a "live" axle are in two sections. The inner end is connected with the differential gear; the outer ends are connected to the drive wheels. It is necessary to support the axle parts in a strong housing. Nowadays multilink rear suspension is standard.

 

LIGHT TRUCK FUEL ECONOMY

In developing optimum specifications for fuel-efficient light trucks, weight reduction, downsized frontal area, aerodynamic improvements, and power plant sizing must be considered, in addition to other factors.

The fuel economy improvement associated with weight reduction must be considered relative to other means of improving economy, since weight reduction is not easy to achieve in light trucks without downsizing. Light trucks are generally considered "weight efficient" since they frequently carry payloads 25,50, or even 100 percent greater than their base curb weights.

If the base structure of a vehicle must be designed to accommodate payloads, then it will essentially be "overdesigned" when running unloaded. This payload requirement renders weight reduction of light trucks very difficult.

Weight reduction via engine downsizing (if possible, considering performance and emission requirements), designing with high strength steels, and use of plastic

and aluminum for structural and non-structural components are being studied.

Use of graphite-fiber reinforced components is also being considered, though technical problems exist.

With present technology, the stages of fuel economy improvements may be as follows:

• determine minimum power requirements to achieve the requisite acceleration and grade speed cruising performance;

• reduce aerodynamic drag and frontal area to minimum feasible levels;

• reduce road load power consumption due to tires, weight, and other powertrain losses;

• select the smallest possible displacement engine which will deliver acceptable performance while considering durability, emissions, engineering and manufacturing constraints, and other factors;

• reduce engine operating rpm to the lowest possible levels considering NVH factors;

• fully optimize automatic transmissions by adding torque converter lockup devices;

• tailor transmission size to engine power output to optimize part-load efficiency;

• consider alternative technology to improve fuel technology.

 

 

VEHICLES AIR CONDITIONING

AND ENVIRONMENT

In the near future, there will be 1 billion vehicles on the world's roads. As this number grows, so does environmental concern over fuel usage, emissions, and end-of-life disposal.

Today's vehicles are composed of many systems, each affecting customer satisfaction and environmental impact. One of many such systems is air-conditioning (A/C). Customers have come to expect the high level of comfort and safety current systems offer. As a result, A/C is now standard on most new vehicles in the U.S. while demand for it in Europe and Asia is rising.

The refrigerant used in current systems is HFC-134a, which is classified as a global warming gas and is under scrutiny for possible phase-out in Europe.

Emissions of HFC-134a from vehicle A/C systems account for about 0.1% of total world emissions. While the automotive industry is improving HFC-134a systems, it is evaluating two replacement refrigerants: carbon dioxide (C02) and propane. The C02 system has higher operating pressures; if used, C02 would require all new A/C system components.

The use of propane requires only a modification of the existing HFC-134a system. In the secondary-loop propane system, a device in the engine compartment chills a coolant (water-glycol). This coolant, not propane, circulates through the passenger compartment.

Although these technical options are promising, cost-benefit analysis is needed to understand the environmental and consumer benefits they offer compared to other potential vehicle fuel-saving technologies.

The international impact of SAE (Society of Automotive Engineers) documents on mobile A/C systems is far-reaching. SAE standards for system design, service equipment, and technician service procedures and training have been used throughout the world. Equipment based on SAE's refrigerant recycling standards is being used in both developed and developing countries to prevent unnecessary release of refrigerant to the atmosphere during service.

Vehicle makers will have to determine which systems need to be changed to best manage total vehicle emissions and then implement those changes.

 

GAS ECOLOGY

There are many ways that we can reduce pollution by observing good gas ecology — that is using our cars in fuel efficient ways.

Don't move the car unless you are going somewhere. Plan ahead. Starting the car up just to move it a short distance produces more pollutants than hours of driving on the freeway.

Don't use your heater until the car is warmed up. The engine will start more quickly, because it won't be losing heat to warm you. Try to drive within 35-45 miles per hour when possible. Driving at slower speeds reduces engine efficiency and causes more pollutants.

Don't make fast starts or stops. Fast starts can burn more than 50% gas than regular acceleration (as well as cause 50% more emissions). When a big burst of gas enters the engine, much of catalytic converter's job is bypassed and the unburned gas comes out the tailpipe or is sent into the converter. Rapid acceleration is only called for in emergency or passing situations. Stopping rapidly also leaves the engine with a lot of unburned gas to deal with. This results in damage to the converter and pollution.

Try not to idle. At bank lines and fast food places with over thirty second waits, turn the engine off, and restart it. It is more fuel efficient, and causes less pollution. The only time that idling is a good thing is after a long, fast run. Idling the engine for a minute or so after one of these helps get rid of any hot spots and fuel vapors.

Keep to steady speeds on the highway. Changing speeds produces more pollution and uses more gas. Don't use the air conditioner unless you have to. It makes your engine work harder, uses more gas, and causes more pollution. Most evaporative emissions get into the atmosphere when we put gas in our cars. Make sure your gas cap is the right one, and in good working order. Gas caps don't cost that much, but are very important in anti-pollution.

Since gasoline expands, never overfill your tank. It will wind up leaking out.

Use known brands of gas. Poor quality gas will not save you money.

Instead, it will foul your engine and cause it to function badly. Try several different brands and octane ratings to find out which makes your car the happiest, and stay with it.

 

 

CARS: PASSION OR PROBLEM?

For many people, cars are more than a convenient form of transportation: they are a source of passion and pleasure. Yet cars can also be a source of many problems.

In 1903, Ford Motors became the first to mass-produce cars. This made the car available to large numbers of people. It has brought people much closer to places of work, study, and entertainment. Many people also work in car-related industries: fixing cars, washing cars, advertising cars and selling car products such as stereos and cellular phones.

Many Americans buy a new car every six years. In fact, there are more cars than people in the United States. In New York City, 2.5 million cars move in and out of the city each day. In this traffic, the average speed is sometimes 8.1 miles per hour. This speed could be easily reached by riding a horse instead of driving a car.

Enviromentalists dream of turning parking lots into parks and replacing cars with bicycles. They insist on developing public transportation and point out that it saves fuel and does not damage the environment that much. Many people around the world are unhappy with car traffic and pollution but they cannot imagine their life without driving.

Still, there is an important question that must be answered: What kind of fuel will be used when gasoline is no longer available? To solve this problem, car companies in Korea, Japan, Europe, and the US develop electric cars that will not require gasoline at all.

The electric car is not a new idea. Being pollution-free, quiet and easy to start, it had a success with women in the 1900s. But gasoline-powered cars were faster and soon became much more popular. In the 1970s, when there were serious problems with the availability of oil, car companies began to plan for a future without gasoline again.

Today’s new interest in the electric car is partly related to a passion for speed and new technology. In 1987 a solar-powered car won a 2,000-mile race in Australia. Air-compressed cars, fuel cell cars, flying cars are currently under development. However, the importance of cars will not decrease, no matter how they change in the future.

 

ENGINE OPERATION

An automobile, powered by a petrol engine, begins to operate when the driver turns a flywheel connected to the engine crankshaft. As the crankshaft revolves, a mixture of fuel and air is drawn from a carburettor into the engine cylinders. The ignition system provides the electric sparks that ignite this mixture. The resultant explosions of the mixture turn the crankshaft, and the engine starts moving. By regulating the flow of the fuel and air with a throttle, the driver controls the rotational speed of the crankshaft.

Cooling, electrical ignition and lubrication systems are of great importance for the good performance of a car. The lights, radio and heater add to the flexibility, comfort, and convenience of the car. The indicating devices keep the driver informed as to engine temperature, oil pressure, amount of fuel, and battery charging rate.

Brakes are of drum and disk types. The steering system consists of a manually operated steering wheel, which is connected by a steering column to the steering gear from which linkages run to the front wheels. It is difficult to turn the steering wheel, and special hydraulic power mechanisms are used to lessen this effort. Suitable springs are used against shocks. There are leaf springs, coil springs, torsion bars and air suspensions.

 

AIR-COOLED ENGINES

All vehicle engines are air-cooled to some degree. Even in water-cooled engines heat is transmitted first from cylinder to water and afterwards, in the radiator, from water to air. This method of cooling is not difficult to accomplish, because the heat taken off the hot cylinder walls by large cooling surface of the radiator and so easy transmission of heat to air is made possible.

Reciprocating engines used in aircraft are almost entirely air-cooled. Aircraft engines cooled by air are manufactured today in sizes ranging from 50 to 3500 hp and they have superseded water-cooled engines. The principal advantages of air-cooled aircraft engines are low weight, and greater reliability in operation. Modern motor-cycles are also designed almost exclusively with air-cooled engines.

New designs of air-cooled vehicle engines are notable for their easy maintenance, reliability and economical operation.

 

COOLING SYSTEM

Almost all automobiles employ liquid systems for their engines. All typical automotive cooling system comprises (1) a series of channels cast into engine block and cylinder head, surrounding the combustion with circulating water or other coolant to carry away excessive heat, (2) a radiator consisting of many small tubes equipped with honeycomb of fins to radiate heat rapidly, that receives and cools hot liquid from the engine, (3) a centrifugal-type water pump with which to circulate coolant, (4) a thermostat, which maintains constant temperature by automatically varying the amount of coolant passing into the radiator, (5) and a fan, which draws fresh air through the radiator.

For operation at temperature below 32 F (0 C), it is necessary to prevent the coolant from freezing. This is usually done adding some compound to depress the freezing point of the coolant. Alcohol formerly was commonly used, but it has a relatively low boiling point and evaporates quite easily, making it less desirable than organic compounds with a high boiling point.

Air-cooled cylinders operate at higher, more efficient temperatures, and air-cooling offers the important advantage of eliminating not only freezing and boiling of the coolant at temperature extremes but also corrosion damage to the cooling system. Control of engine temperature is more difficult, however, and high-temperature-resistant ceramic parts more difficult, however, and high-temperature is significantly increased.

 

ELECTRICAL SYSTEM

Originally, the electrical system of the automobile was to the ignition equipment. With the advent of the electric starter, electric lights and horns began to replace the kerosene and acetylene lights and bulb horns. Electrification was rapid and complete, and by 1930, six-volt systems were standard everywhere. The electrical system comprises a storage battery, generator, starting motor, lighting system, ignition system, and various accessories and controls.

The ignition system provides the spark to ignite the air-fuel mixture in the cylinders of the engine. The system consists of the spark plugs, coil, distributor, and battery. In order to jump the gap between the electrodes of the spark plugs, the 12-volt potential of the electrical system must be stepped up to about 20,000 volts. This is done by a circuit that starts with the battery, one side of which is grounded on the chassis and leads through the ignition switch to the primary winding of the ignition coil and back to the ground through an interrupter switch. Interrupting the primary circuit induces a high voltage across the secondary of the coil to each of the wires leading to the spark plugs.

The source of energy for the various electrical devices of the automobile is a generator, or alternator, that is belt-driven from the engine crankshaft.

A lead-acid battery serves as a reservoir to store excess output of the generator. Energy for the starting motor is thus made available along with power for operating other electric devices when the engine is not running or when the generator speed is not sufficiently high to carry the load.

STEERING

Automobiles are steered by a system of gears and linkages that transmit the motion of the steering wheel to the pivoted front wheel hubs. The gear mechanism, located at the lower end of the shaft carrying the steering wheel, is usually a worm-and-nut or cam-and-lever combination that rotates a shaft with an attached crank arm through a small angle as a steering wheel is turned. Tie rods attached to the arm convey its motion to the wheels. In concerning, the inner wheel must turn through a slightly greater angle than the outer wheel, because the inner wheel negotiates a sharper turn. The geometry of the linkage is designate to provide for this.

When the front wheels are independently suspended, the steering must be designed so that the wheels are not turned as tie-roads lengthen and shorten as result of spring action. The point of linkage attachment to the steering gear must be placed so that it can move vertically with respect to the wheel mountings without turning the wheels.

The distribution of weight between the front and rear wheels of automobiles shifted toward the front as the engine and passenger compartment were moved forward to improve riding comfort and road-handling characteristics. As the weight carried on the front wheels increased to more than the half of the total vehicle weight, the effort necessary to turn the wheels in steering increased. Larger, heavier cars with wider tires and lower tire pressure also contribute to drag between tire and road that must overcome in steering, particularly in parking. It was originally considered satisfactory to limit the pull on the rim of the steering wheel to 30 pounds (14 kilograms), but this limit proved to be too high. Considerable reduction in the work of steering resulted from increased efficiency of the steering wheel was accomplished by increasing the overall steering gear ratio. Large steering gear ratios make high-speed maneuverability more difficult, however, because the steering wheel must be turned through greater angles. On the other hand, steering mechanisms of higher efficiency are also more reversible; that is, road shocks are transmitted more completely from the wheels and must be overcome to a greater extend by the driver. This causes a dangerous situation on rough roads or when a front tire blows out, because the wheel may be jerked from the driver's hands.

WHEELED VEHICLES

After the early efforts to domesticate animals for their burden-carrying abilities, the most significant addition to human locomotion was the wheeled vehicle. It was one of the great inventions of all times because of the contribution that the wheel, and its utilization in a vehicle, makes up applying supplemental sources of power to an individual's mobility. Horses and camels can travel faster than the humans on their backs, but to transport more than one person with a single animal – something most horses had the strength to do – vehicle was needed. Probably the first conveyance of this sort was a plank or log dragged along the ground; the Plains Indians of North America used such a travois of two poles in their transhumant wandering until the 19^th century. Its mechanical inefficiency must have prompted the search for improvements. The invention of the wheel made the contribution of a horse more productive. The power provided by any one horse has grown with changes in vehicles, in harnessing and in the surface on which it operates.

Much of human history saw no technology superior to the sling or travois but when the wheel was devised changes was both substantial and probably fairly rapid. It seems that there were versions of the travois shaped like a platform, with a great reduction in the extent of actual contact with the ground; only the ends of the poles supporting the platform dragged along the surface, where friction would be great. Improvement came with placing a revolving wheel at the end of each of the drag poles. From this advance it was but a minor step to arrive at a two-wheel cart.

 

ANTITHEFT DEVICES

Most vehicle theft is an increasing problem for owners, insurers, and manufacturers. The annual number of thefts increases almost every year, and the rate of thefts mat by expected to exceed 1 out of every 100 registered vehicles per year in the United States by the end of the 20^th century. The problem is, however not new. The 1900 Leach automobile featured a removable steering wheel that the driver could carry away to prevent unauthorized vehicle use. More recently, sophisticated electronic alarms, some of which incorporate radio beacons, and more tamper-resistant wiring electronic locks have been produced.

 

SAFETY SYSTEMS

From its beginnings, the automobile posed serious hazards to public safety. Vehicle speed and weight provided an impact capacity for occupants and pedestrians that produced great numbers of fatalities (13,000 in 1920) and serious injuries. During the 20^th century, the rates of death and injury declined significantly in terms of vehicle miles. Because of the increased number of vehicles on the road, however, total fatalities have declined only slightly. Most fatal accidents occur on either city streets or secondary roads. Federal expressway systems are relatively safer. Driver training, vehicle maintenance, highway improvement, and law enforcement were identified as key areas with potential for improving safety, but the basic design of the vehicle itself and the addition of special safety features received increased attention. Safety features of automobiles come under two distinct headings: accident avoidance and occupant protection.

 

INTERNATIONAL TRANSPORT

International transport refers to any of goods between countries. The journey may involve carriage only, but if the countries are separated by strength of water (sea or ocean), the crossing, or voyage if the distance is longer, will have to be organized specifically.

In both cases, the operations will normally resort to surface transport.

The transport of goods may be classified according to the countries where operation take place or to the means of transport – transport facilities – involved.

The choice of the means of conveyance depends on the communication network of the countries as well as on the nature of the goods and the cost of the transport operation.

Inland waterways (navigable rivers and canals) can also be of use for certain type of goods. Associating different means of transport gives rise to what is known as multimodal transport – or intermodal/combined transport – which has become more common with the development of containerization.

 

ROAD TRANSPORT

Road transport is perhaps the most visible and common means of conveyance because of the presence on our roads of a great number of lorries whose variety stems from the necessity for carriers to meet the wide range of needs from shippers.

A road hauler (GB) or trucker (US) may own a fleet of vehicles, but part of their equipment can be rented from specialized firms for special shipments. They usually set up their business by determining a specific route and serving a few well-defined areas. Lorry drivers then commonly ply between the same cities and the experience they gain by so doing reinforces the efficiency of the service.

A semi-trailer – or articulated lorry – with an important payload, is mostly resorted to for a long haul in order to reduce transport costs. When an open-top trailer is used, a tarpaulin – or tilt – will protect the goods from the rain. A removal van carries all the furniture and belongings of a family moving house. A tanker lorry is especially designed for the transport of liquid cargoes, whether foodstuff, oil products or chemicals. Retailers and shopkeepers often have their orders brought to them by means of a delivery van.

More and more goods are transported in containers by both road and rail. This bimodal transport makes it necessary to tranship the goods from train onto lorries in a piggy-back terminal.

Road transport depends on the road network. Not all roads can be used by any sort of lorry and if motorways and main roads – or trunk roads – are generally available, as well as dual carriageways in great Britain, there may be a few limitations on secondary roads in order to prevent lorries from causing obstructions – or "hod-ups", "traffic-jams", "congestions". This may indeed be the case at certain junctions – or "crossroads" – which is one of the reasons why these are gradually being replaced by roundabouts. In the same way, level crossings which halt the traffic at regular intervals tend to disappear in modern road networks. Road works are another cause of delays and a diversion may have to be set up to avoid inconvenience.

Finally, when planning a route, haulers must remember that not all the roads and bridges are free, and they may have to pay a toll for part of the route.