Power-plant mounting

All power plants, with the few exceptions, are mounted in the forward end of the frame. The transmission is considered part of the power plant, since it governs or controls the ratio of speed and power which may be delivered to the rear axle. The engine drives the transmission, and the transmission turns the propeller shaft.

V-8 power plant (Ford V-8 engine and accessories). A transmission B breather C fuel pump D air cleaner E carburetor F generator G fan H intake manifold I exhaust manifold J starter K water pump L timer distributor M rubber engine mount N cylinder block 0 oil pan P cylinder head

The speed of the propeller shaft depends on the gear in which the shift lever is set. In high, the ratio through the transmission is 1 to 1. In low, the ratio is about 3 to 1. Low and intermediate give greater turning power (torque) to the propeller shaft than high, but the speed of the car is cut down. These points are mentioned thus briefly to show that the power plant rightfully includes this unit which transmits the power of the engine at varying speeds. Likewise, the clutch belongs to the power plant.
The most favoured method is to build engine, clutch, and transmission together as a unit, and mount the unit power plant in the car frame in a manner calculated to prevent engine vibrations being transmitted to the car interior. Rubber-lined mounting blocks, are used to check engine vibration.
For many years either three- or four-point metallic contact mounting was used for the unit, power plant, both being popular with the manufacturers. The later use of the rubber engine-mounting blocks reduced the amount of vibration carried to the driving compartment.
Chrysler engineers learned that by mounting an engine at two points, so that the centre of mass or centre of gravity was approximately on a line between the two bearings (one well up on the front of the engine and the other under the transmission case), engine vibration could be still further reduced. The rocking or torque reaction of the engine under load was first absorbed by a leaf spring but later this spring was replaced by rubber blocks which were found more effective. There are many variations of power-plant mounting, most of which make use of some form of rubber mountings.
Just as the units of the chassis were considered, it is desired to separate and study the functions of the units composing the power plant on this page. Next, the individual units going into an engine are studied, and in the individual parts of the various other units of the power plant are discussed in detail. On this page, it is desired to familiarize with the names and locations of the various units going into the make-up of a complete power plant. The duties falling to the lot of each accessory or unit will be discussed briefly.

Engine

The water pump and oil pump appear on the left side of the engine, and are considered a definite part of the engine. A fan-drive pulley appears on the forward end of the pump shaft. A fan mounting bracket is provided.

Nask engine	Chevrolet engine

The right-side view of the engine shows the starting motor bolted to the flywheel housing. This starter, when removed, exposes the teeth of the flywheel ring gear to view. The screw mounting holes are made in accordance with S.A.E. specifications.
When the starting-motor manufacturer builds his equipment, it is built according to the same specifications, and a fit is thus assured. The manifold is a part of the engine, but the carburetor is an accessory. The intake and exhaust manifolds are cast together in some instances. A flange is left at the centre of the manifold. This flange is machined to allow the carburetor to be fitted to it.
Carburettors are made in varying sizes and certain size flanges are provided for the specified carburetor sizes. The car manufacturer may then fit a carburetor of the size desired and of the make which he may select from those offered. Other fittings and accessories are mounted on the engine where the car manufacturer may desire. The engine manufacturer usually provides certain bosses at advantageous points, and the car builder utilizes them at his discretion.
Where the car manufacturer builds his own engines, the practice will vary slightly. Only those mountings are provided which the designee knows are to be used., It is very rare that the engine accessories are built by the car manufacturer ; hence all these are designed with certain fittings known as S.A.E. specifications. Members of the Society of Automotive Engineers (S.A.E.) have agreed on these specifications, and parts will fit when machined according to them. This greatly reduces the cost of production, and car owners as well as manufacturers benefit by it.

Carburetor

 

An engine, such as is used in automobile service, is termed an internal-combustion engine. This means that the fuel is burned within it. The point where the fuel is burned is called the combustion chamber. This space is above the piston in the cylinder head and around the valves, and naturally includes that portion of the cylinder exposed as the piston is driven down.
The fuel used in engines is, for the most part, gasoline or similar fuel. The burning process is ordinarily termed firing or exploding the gas. The fuel, that is, the gasoline, in order to be burned or "exploded" within the combustion space, must first be passed through the carburetor where it is mixed with air. Next, it must be drawn into the combustion space, and then it must be compressed after which it is fired by the electric spark.
The function of the carburetor is to mix the fuel and air. In order to mix the gasoline with the air, the gasoline must be sprayed into the air which is rushing through the carburetor on its way into the engine. The early carburettors were called mixing valves.
Gasoline is furnished the carburetor from the main supply tank by means of a fuel pump, a vacuum tank, gravity feed from the main supply tank, or air pressure. Carburetor engineers spend much time designing and testing their product for motor-car manufacturers.
The demands placed on carburettors vary with load, bore and stroke of the engine, climatic conditions, rear-axle-gear ratios, and a multitude of other details. Variation in fuel is, of course, a vital consideration. The principles of carburetor construction will be discussed at a later point, but at this time it is well to fix its function clearly in mind. The carburetor, by aid of the suction of the engine, takes raw fuel, converts it into a spray of vapour, and mixes it with a charge of air for the cylinders of the car.
The mixture is called a fuel charge. Maintaining the proper proportions of fuel and air at all engine speeds is the task of the carburetor. If this is not done, the engine fails to operate satisfactorily. Carburetors may be either updraft, in which case the incoming air passes up, through it, or downdraft (air passing down).
 
Timer-distributor and coil

 
It is the function of the ignition set to deliver a spark to the spark plug at the approximate moment when the compression is greatest. All timer-distributors are manufactured to S.A.E. specifications. The car manufacturer selects the equipment which he desires, or he may have the electrical-equipment factory build it after a specified design.
An ignition set may be either self-contained as in the case of the high-tension magneto used on some busses, trucks, marine engines, racers, and aircraft engines, or it may be composed of several units. Every ignition set has three major parts. These are the timer, the distributor, and the coil .
Battery ignition depends on the generator and battery for current. High-tension magnetos generate their own current. Almost all passenger cars depend on the manufacturers of batter y-ignition equipment for their ignition sets. The theory of ignition is discussed later.
In brief, it is as follows: The ignition coil draws current at low voltage from the battery. This current is stepped up to high voltage in the coil when the timer breaker points open. The high-tension current (spark) is carried to the proper plug by the cable from the distributor. Thus, its task of firing the charge of fuel in the cylinder is performed in time with the engine rotation.

Spark plugs

 

The purpose of the spark plug is to receive the high.. tension spark or current from the distributor (through the spark-plug cable), and conduct it to the combustion space, where it fires the charge as it jumps the air gap of the plug. It must be made most carefully in order not to break down in the intense heat of the exploded gases. Ordinarily, one plug per cylinder is used by the manufacturer, but two plugs may be used. When more than one plug is used in a cylinder, it is with the idea of preventing failure and also securing quicker ignition.

Generator

 

Passenger cars are dependent on the storage battery for their ignition and lighting as well as electric cranking. The battery would quickly be exhausted were it not for the generator which is constantly building up or charging the battery when the engine is operating above an idling speed. Different methods are used to drive the generator. Unlike the timer-distributor, it is not necessary to drive the generator at a definite speed relation with the engine.
Belt drive is popular and quite satisfactory. The pump may be connected to the shaft by any one of several means. Special flexible couplings are used and, in a number of instances, rubber hose is clipped to the ends of the accessory and generator shafts, thus giving a quiet and flexible drive. The functions, then, of the generator are to keep the battery charged and assist in supplying current for the lighting of the lamps of the car and furnishing current for ignition.

Starting motor

 

Hand cranking was for many years a factor in limiting the use of passenger automobiles. Special spring starting devices, gas starters, and air starters were designed to relieve the driver of this arduous and dangerous task. When Mr. Chas. F. Kettering, Vice-President of General Motors, in Charge of Research, invented and perfected the system of electric cranking of automobiles, he performed a wonderful service for both car manufacturers and the general public.
Starting motors are designed to turn the engine over at speeds in excess of those possible by hand cranking. They are connected to the engine while cranking it, and then are automatically disengaged when the engine starts to operate under its own power. Starting motors, although small, are assigned heavy duties.
The amount of current they draw is very great. Operating them quickly exhausts the battery. The generator requires about fifty times as long to recharge a battery as is required to discharge it in normal starting service. The function of the starting motor is to crank the engine until it has drawn in gas and compressed it, at which time the ignition-distributor delivers a spark to fire the charge, and the engine operates under its own power.
The starting motor of a passenger automobile operates for a very short period of time and at very infrequent intervals. The "starters" are now so well built that failure occurs only very rarely.

Clutch

 

There are a number of types of clutches. Cone clutches were very popular at one time. Disk or multiple-plate clutches were used in many passenger vehicles. Single-plate clutches for light cars and double-plate clutches for the heavier cars are in general use.
Clutches are provided with a clutch-pressure plate which moves or is made to turn with the flywheel at all times. A plate is fastened to the clutch shaft, and this connects with the transmission shaft. When the clutch is held in the "out" position, the clutch-pressure plate on the flywheel is free to turn with it, but does not cause the plate fastened to the clutch shaft to turn.
When "in," the springs in the clutch-pressure plate throw the plates together and hold them that way. The friction material on the driven plate engages the plain faces of the clutch-pressure plate and the flywheel, and causes it (the driven clutch plate) to turn. Clutches must give a smooth pick-up of the load, and must release the load quickly when the clutch pedal is depressed. They must hold positively under all conditions of load, and yet must be free of grabbing or jerking.
The hydraulic drive (fluid flywheel) eliminates all jerking. With its use, much gear-shifting is eliminated since the load may be picked up in any speed.

Transmission

 

The connection of the transmission with the power plant was discussed at the first part of this chapter. Transmissions are made by manufacturers ,of cars in many instances ; but very often they are built by factories which have had long experience in building gears for this special service.
Transmission gears are subject to as severe use as, and worse abuse than, any other part of the automobile with the possible exception of the clutch. However, these two items are used in connection with each other, and each must stand much abuse from inexperienced and incompetent drivers. The transmission gears are the only gears about the motor car which are not as a rule in constant mesh. Gear shifting means demising and meshing of the teeth of the driving and driven gears except where shifting dogs or dog clutches are used.
In case of unsuccessful shifts, or shifts which are only partially completed before the clutch is let in, the teeth of the transmission gears are subject to abuse. Clashing and grinding gears is abuse. A driver, who is untrained in shifting, and who fails to understand or heed instruction, will ruin the best gears it is possible to make. In his hands, gears, which should give service for the life of the car, are ruined in a few thousand miles. As designed by the builders, the transmission gears are amply strong, if not abused.
Conventional practice specifies the use of the sliding gear or change gear as a means of securing changes of car speeds. Reverse drive also is secured through gear changes in the gear box or transmission case. Differences in construction details in the transmission are treated elsewhere.

Fan

 

Engines are provided with fans, to draw the air through the radiator when the engine is operating. Heat from the engine must be passed off into the air. The water in the engine water jacket carries it to the radiator, and the air passing through the radiator conducts the heat out of the fins and tubes. Fans are usually made up by shops which cater to the car manufacturers, by producing some of the smaller parts for them. Belts are used as a rule for fan drive. Adjustment of the fan bracket is provided in order that the fan belt may be kept at proper tension.

Engine accessories

 

Figure on top of this page illustrates a number of the usual engine accessories. Most engines are fitted with an air cleaner which may also be designed as a flashback screen or fire preventer or an intake-roar silencer. The carburetor on this engine is downdraft.
The exhaust manifold has a centre outlet for tail-pipe connection. The intake manifold has a section interlocking the exhaust manifold so as to receive heat there from. The oil pump is driven from the camshaft and is easy of access from the side of the engine. The oil cleaner is attached to the engine near the oil pump and just to the rear of the fuel pump which is driven by the engine from the camshaft. The fan is mounted on the water-pump shaft and is belt-driven.

Other accessories

Oil gauges or oil-level indicators for the crankcase and oil-pressure gauges for the dash are a part of the power plant. Switches for the starting motor and for the ignition set are also part of the power plant.

                                       PURPOSE OF AIR FILTER IN CARS

 Studies conducted over the past two decades demonstrate that the exposure of the passengers inside a car to the dangerous air pollutants including respiratory irritants, neurological agents, volatile organic compounds (VOCs), carbon monoxide and carcinogens is significantly higher than that of bicyclists, pedestrians and public transfer riders. 
Increased exposure to these pollutants can produce serious health problems. Benzene is a known carcinogen and VOCs are  also likely cancer agents. Almost all the pollutants can irritate the eyes, nose, and respiratory systems of people exposed to them.
They also may hinder the development of fetuses and infants. Studies indicate that the elevated levels of auto exhausts can also suppress the immune system, making human beings more vulnerable to colds, influenza, and other respiratory conditions like asthma. Car air filters purify the air inside a car, allowing the passengers to have healthy and clean air to breathe.
Car air filters come in two main types: the panel style, as used on most fuel-injected cars, and the radial style, which are usually used on carbureted vehicles. A car air filter is enclosed in a black plastic casing near the center-top of the engine.

The air filter traps dirt particles, which can cause damage to engine cylinders, walls, pistons and piston rings. Changing car's filters on a regular basis can have a significant impact on engine life and performance. A good rule of thumb is to change filters once or twice a year, or roughly once every 15,000 miles. Replacing a clogged air filter has two-fold impact on the engine: a fuel economy benefit: up to 10%, which makes for equivalent gasoline savings up to 15¢ per gallon.
Dirty and dusty driving conditions will require more frequent filter replacements. It is important to avoid using the wrong size filter in a car.
Nowadays, car owners are using ‘Nanotechnology’ based filters to improve cabin air quality. Such filters contain charcoal layers, which remove odors. These filters allow ‘mechanical filtration’, in which the fiber material of the filter with pores of a specific size will trap particles larger than the size of the pores. Almost 80% of the cars sold in U.S. include a built-in nanotechnology-based filter.

Five Types of Car Suspension:

Since the car was invented, a few types of suspensions have been used to make driving more comfortable and safer. Many cars use independent front suspension, in this case each front wheel can move independently and attached separately. Some cars also have independent rear suspensions, which result in four-wheel independent suspension. Older cars use dependent rear suspension. Usually, you’ll find double wishbone and strut suspension in consumer cars. Right now, pneumatic suspension is becoming more popular in consumer cars and while electromagnetic suspensions are slowly being introduced.

Double-wishbone suspension:

It has a longer lower control arm and shorter upper control that is used to hold the wheel tightly to the frame. In this case, control arms are necessary to allow the wheel to move with better flexibility, just like a hinge that allows door to swing freely. If you check it closer, you’ll notice the lower arm is bigger because it needs to bear a significant amount of load when the car is driven. Ball-joint and rubber bushings are used to allow the wheels to pivot and rotate.

Multi-link suspension:

It is more advanced than the double-wishbone type and available in a number of configurations. It offers more flexibility, which results in better ability to deal with changes in driving conditions. Although this suspensions system still uses wishbone, each arm is connected separately to a spindle instead of as a single solid unit. It allows independent pivoting based on the steering wheel movement.

Strut suspension:

You can find conventional and modified strut suspension systems in consumer cars. On conventional struts, its coil springs are wrapped around a cartridge, while the modified strut suspension have a spring that is mounted remotely. These suspensions don’t have upper control arm. The wheels are hold in place by an upper strut mount.

Air suspension systems:

It is found on certain SUVs and luxury cars. This suspension system uses tubes controlled by sensors and air-filled bags that determine whether the suspension should be stiffened or softened, by pumping or letting the air out of the bags. Some air suspensions are automatic while others are controlled by the driver

Bose acoustic suspension:

It is developed by Bose, the same company that makes expensive and sensitive sound systems. The company comes up with an innovative suspension system that uses acoustic energy, a truly major automotive advance. Instead of using hydraulics, shock absorbers and conventional springs, the system has electromagnetic motors on all wheels. When the car moves, an amplifier sends signals to boost the wheel motors, allowing better suspension sensitivity than contemporary suspension system. The suspension allows the car to remain level when the accelerator and the brake pedals are pressed abruptly. Passengers may also notice far fewer shakes during sharp turn and vibrations are virtually eliminated.

How does a dynamo work?

 The movement of another body is transmitted to a rectangular coil of wire that is inside a U-Shaped magnet. The motion of this coil of wire cuts the magnetic flux in the magnet. Faraday once stated that-Whenever there is a change in magnetic flux linked with a circuit there is an induced current and the strength of this induced current is directly proportional to the rate of magnetic flux-. So according to this rule when the magnet is in motion it is constantly cutting the magnetic flux, and as it does this there is a current that is induced (eddy currents). However a dynamo can either be A.C or D.C according to the brushes and number of commutators used (Flemings Right-hand rule). If we refer back to Faraday's rule it says that the strength of this induced current is directly proportional to the rate of magnetic flux. This rule can be seen practically in a bicycle that has a dynamo. The faster the rider rides the faster the change in magnetic flux and hence the brighter the light

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Dynamo is just the opposite/ reverse action of motor operation.

When a conductor is moved across a magnetic field, there induces an emf (voltage) across conductor terminals so as it opposes the change of flux (Lenz rule).
Dynamo is constructed with a cylindrical permanent magnet (which rotates at the center) amidst windings that we take the voltage output from. when the magnet rotates its flux path changes relative to the windings and across the winding there exists an electro-motive-force as a voltage..

GO back a little to leap further...

Lami's theorem

Lami's theorem is very helpful tool in mechanics to solve various problems that include exactly three vector quantities. 

What is Lami's theorem ?

Lami's theorem states that if three co-planer forces are acting on the same point then each force is proportional to the sine of the angle between other two forces.

Formula
This formula is given as:


Explanation
Consider three forces:
Let OA = F3
OB = F1
OC = F2

Also note that
* Angle opposite to OA is "alpha".
* Angle opposite to OB is "Beta".
* Angle opposite to OC is "Gamma".

FOUR STROKE ENGINE WORKING

Four Stroke Engine

The four stroke engine was first demonstrated by Nikolaus Otto in 1876¹, hence it is also known as the Otto cycle. The technically correct term is actually four stroke cycle. The four stroke engine is probably the most common engine type nowadays. It powers almost all cars and trucks.
The four strokes of the cycle are intake, compression, power, and exhaust. Each corresponds to one full stroke of the piston; therefore, the complete cycle requires two revolutions of the crankshaft to complete.

 

Intake

During the intake stroke, the piston moves downward, drawing a fresh charge of vaporized fuel/air mixture. The illustrated engine features a poppet intake valve which is drawn open by the vacuum produced by the intake stroke. Some early engines worked this way; however, most modern engines incorporate an extra cam/lifter arrangement as seen on the exhaust valve. The exhaust valve is held shut by a spring (not illustrated here).

 Compression

As the piston rises, the poppet valve is forced shut by the increased cylinder pressure. Flywheel momentum drives the piston upward, compressing the fuel/air mixture.

Power

At the top of the compression stroke, the spark plug fires, igniting the compressed fuel. As the fuel burns it expands, driving the piston downward.

Exhaust

At the bottom of the power stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted fuel out of the cylinder.

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Ignition System

This animation also illustrates a simple ignition system using breaker points, coil, condenser, and battery.

A number of visitors have written to point out a problem with the breaker points in my illustration. In this style ignition circuit, the spark plug will fire just as the breaker points open. The illustration appears to have this backwards.
In fact, the illustration is correct; it just moves so fast it’s difficult to see! Here’s a close-up of the frames just at the point the plug fires:

My original intent was to accurately show that the points need to remain closed for only a fraction of a second, called the dwell. By illustrating this, I inadvertently obscured the overall operation of the circuit. Perhaps someday I’ll prepare a more detailed illustration of the ignition system alone.
Larger four stroke engines usually include more than one cylinder, have various arrangements for the camshaft (dual, overhead, etc.), sometimes feature fuel injection, turbochargers, multiple valves, etc. None of these enhancements changes the basic operation of the engine.

APTITUDE QUESTION:2

2.	A train 125 m long passes a man, running at 5 km/hr in the same direction in which the train is going, in 10 seconds. The speed of the train is:
	A. 45 km/hr B. 50 km/hr C. 54 km/hr D. 55 km/hr

3.	The length of the bridge, which a train 130 metres long and travelling at 45 km/hr can cross in 30 seconds, is:
	A. 200 m B. 225 m C. 245 m D. 250 m

4.	Two trains running in opposite directions cross a man standing on the platform in 27 seconds and 17 seconds respectively and they cross each other in 23 seconds. The ratio of their speeds is:
	A. 1 : 3 B. 3 : 2 C. 3 : 4 D. None of these

5.	A train passes a station platform in 36 seconds and a man standing on the platform in 20 seconds. If the speed of the train is 54 km/hr, what is the length of the platform?
	A. 120 m B. 240 m C. 300 m D. None of these

TYPE YOUR ANSWERS IN COMMENT AREA WITH QUESTIONS AND THE ANSWERS WILL BE UPDATED TOMORROW..

APTITUDE QUESTION:(13-3-2012)

1.  A train running at the speed of 60 km/hr crosses a pole in 9 seconds. What is the length of the train? A. 120 metres B. 180 metres C. 324 metres D. 150 meters