GST

GST
         It is a destination based tax on consumption of goods and services. It is proposed to be levied at all stages right from manufacture up to final consumption with credit of taxes paid at previous stages available as setoff. In a nutshell, only value addition will be taxed and burden of is to be borne by the final consumer. 

Measuring Instruments

1) linear Measurement-

A) Nonprecision instruments

a) Steel rule
b) calipers
c) Dividers
d) Telescopic gauge
e) Depth gauge

B) Precision Instruments

a) Micrometer
b) Vernier calipars
c) Height gauge
d) Slip gauge

2) Angular Measurments

A) Nonprecision instruments

a) protractors
b) Adjustable bevel
c) Engineers square
d) Combination set

B)  Precision Instruments

a)  Bevel Protractors
b) Dividing Head
c) Sine bar
d) Angle gauges
e) Spirit level
f) clinometers
g) Autocollimatos

3) Taper measuements

4) Surface measurments

Types of Loads

Types of Loads

Different types of loads  in engineering mechanics are compression, tension, torsion and bending.

Compression:

Compression loading is an effect in which the component reduces it size. During compression load there is reduction in volume and increase in density of a component.

Tension:

Tension is the act of stretching rod, bar, spring, wire, cable etc. that is being pulled from the either ends.

Torsion:

Torsion is the act of twisting of an rod, wire, spring etc. about an axis due to applied couple (torque).

Bending:

Bending is act of changing component from straight form into a curved or angular form.

Differential Introduction

Differential Introduction

A differential is a device, usually, but not necessarily, employing gears, capable of transmitting torque and rotation through three shafts, almost always used in one of two ways: in one way, it receives one input and provides two outputs—this is found in most automobiles - and in the other way, it combines two inputs to create an output that is the sum, difference, or average, of the inputs.

In automobiles and other wheeled vehicles, the differential allows each of the driving road wheels to rotate at different speeds.

The differential has three jobs:

1. To aim the engine power at the wheels

2. To act as the final gear reduction in the vehicle, slowing the rotational speed of the transmission one final time before it hits the wheels

3. To transmit the power to the wheels while allowing them to rotate at different speeds (This is the one that earned the differential its name.)

Scavenging of IC Engines

The scavenging, in an internal combustion engine (IC Engine), is the process of removing the burnt gases from the combustion chamber of the engine cylinder. Though there are many types of scavenging, yet the following are important from the subject point of view:

1. Crossflow scavenging. In this method, the transfer port (or inlet port for the engine cylinder) and exhaust port are situated on the opposite sides of the engine cylinder (as in the case of two stroke cycle engines).

2. Back flow or loop scavenging. In this method, the inlet and outlet ports are situated on the same side of the engine cylinder.

3. Uniflow scavenging. In this method, the fresh charge, while entering from one side (or sometimes two sides) of the engine cylinder pushes out the gases through the exit valve situated on the top of the cylinder.

1. Two Stroke vs Four Stroke Engines

Two Stroke vs Four Stroke Engines - Advantages and Disadvantages of Two Stroke over Four Stroke Cycle Engines.

In a two stroke engine, the working cycle is completed in two strokes of the piston or one revolution of the crankshaft. In a four stroke engine, the working cycle is completed in four strokes of the piston or two revolutions of the crankshaft.

The following are the advantages and disadvantages of two stroke over four stroke cycle engines :

Advantages

1.    A two stroke cycle engine gives twice the number of power strokes than the four stroke cycle engine at the same engine speed. Theoretically, a two stroke cycle engine should develop twice the power as that of a four stroke cycle engine.

2.    For the same power developed, a two stroke cycle engine is lighter, less bulky and occupies less floor area.

3.    A two stroke cycle engine has a lighter flywheel and gives higher mechanical efficiency than a tour stroke cycle engine.

Disadvantages

1.    The thermal efficiency of a two stroke cycle engine is less than that of a four stroke cycle engine, because a two stroke engine has less compression ratio than that of a four stroke cycle engine.

2.    The overall efficiency of a two stroke cycle engine is also less than that of a four stroke cycle engine.

3.    The consumption of lubricating oil is large in a two stroke cycle engine because of high operating temperature.

TURBOCHARGER

TURBOCHARGER

A turbocharger or turbo is a forced induction device used to allow more power to be produced for an engine of a given size. A turbocharged engine can be more powerful and efficient than a naturally aspirated engine because the turbine forces more intake air, proportionately more fuel, into the combustion chamber than if atmospheric pressure alone is used. Turbo are commonly used on truck, car, train, and construction equipment engines. Turbo are popularly used with Otto cycle and Diesel cycle internal combustion engines.

There are two ways of increasing the power of an engine. One of them would be to make the fuel-air mixture richer by adding more fuel. This will increase the power but at the cost of fuel efficiency and increase in pollution levels… prohibitive! The other would be to somehow increase the volume of air entering into the cylinder and increasing the fuel intake proportionately, increasing power and fuel efficiency without hurting the environment or efficiency. This is exactly what Turbochargers do, increasing the volumetric efficiency of an engine.

                                           

In a naturally aspirated engine, the downward stroke of the piston creates an area of low pressure in order to draw more air into the cylinder through the intake valves.  Now because of the pressure in the cylinder cannot go below 0 (zero) psi (vacuum) and relatively constant atmospheric pressure (about 15 psi) there will be a limit to the pressure difference across the intake valves and hence the amount of air entering the combustion chamber or the cylinder. The ability to fill the cylinder with air is its volumetric efficiency. Now if we can increase the pressure difference across the intake valves by some way we can make more air enter into the cylinder and hence increasing the volumetric efficiency of the engine.

It increases the pressure at the point where air is entering the cylinder, thereby increasing the pressure difference across the intake valves and thus more air enters into the combustion chamber. The additional air makes it possible to add more fuel, increasing the power and torque output of the engine, particularly at higher engine speeds.

Turbochargers were originally known as Turbo superchargers when all forced induction devices were classified as superchargers; nowadays the term "supercharger" is usually applied to only mechanically-driven forced induction devices. The key difference between a turbocharger and a conventional supercharger is that the latter is mechanically driven from the engine, often from a belt connected to the crankshaft, whereas a turbocharger is driven by the engine's exhaust gas turbine. Compared to a mechanically-driven supercharger, turbochargers tend to be more efficient but less responsive.

HISTORICAL PERSPECTIVE

The turbocharger was invented by Swiss engineer Alfred Büchi. His patent for a turbocharger was applied for use in 1905. Diesel ships and locomotives with turbochargers began appearing in the 1920s.

AVIATION:

During the First World War French engineer Auguste Rateau fitted turbochargers to Renault engines powering various French fighters with some success. In1918, General Electric engineer Sanford Moss attached a turbo to a V12 Liberty aircraft engine. The engine was tested at Pikes Peak in Colorado at 4,300 m to demonstrate that it could eliminate the power losses usually experienced in internal combustion engines as a result of reduced air pressure and density at high altitude.

Turbochargers were first used in production aircraft engines in the 1920s, although they were less common than engine-driven centrifugal superchargers. The primary purpose behind most aircraft-based applications was to increase the altitude at which the airplane could fly, by compensating for the lower atmospheric pressure present at high altitude.

PRODUCTION AUTOMOBILES:

The first turbocharged diesel truck was produced by Schweizer Maschinenfabrik Saurer (Swiss Machine Works Saurer) in 1938 .The first production turbocharged automobile engines came from General Motors in 1962. At the Paris auto show in1974, during the height of the oil crisis, Porsche introduced the 911 Turbo – the world’s first production sports car with an exhaust turbocharger and pressure regulator. This was made possible by the introduction of a waste gate to direct excess exhaust gasses away from the exhaust turbine. The world's first production turbo diesel automobiles were the Garrett-turbocharged Mercedes 300SD and the Peugeot 604, both introduced in 1978. Today, most automotive diesels are turbocharged.

1962 Oldsmobile Cutlass Jet fire

1962 Chevrolet Corvair Monza Spyder

1973 BMW 2002 Turbo

1974 Porsche 911 Turbo

1978 Saab 99

1978 Peugeot 604 turbo diesel

1978 Mercedes-Benz 300SD turbo diesel (United States/Canada)

1979 Alfa Romeo Alfetta GTV 2000 Turbodelta

1980 Mitsubishi Lancer GT Turbo

1980 Pontiac Firebird

1980 Renault 5 Turbo

1981 Volvo 240-series Turbo

OPERATING PRINCIPLE

A turbocharger is a small radial fan pump driven by the energy of the exhaust gases of an engine. A turbocharger consists of a turbine and a compressor on a shared shaft. The turbine converts exhaust heat to rotational force, which is in turn used to drive the compressor. The compressor draws in ambient air and pumps it in to the intake manifold at increased pressure resulting in a greater mass of air entering the cylinders on each intake stroke.

The objective of a turbocharger is the same as a supercharger; to improve the engine's volumetric efficiency by solving one of its cardinal limitations. A naturally aspirated automobile engine uses only the downward stroke of a piston to create an area of low pressure in order to draw air into the cylinder through the intake valves. Because the pressure in the atmosphere is no more than 1 atm (approximately 14.7 psi), there ultimately will be a limit to the pressure difference across the intake valves and thus the amount of airflow entering the combustion chamber.

Because the turbocharger increases the pressure at the point where air is entering the cylinder, a greater mass of air (oxygen) will be forced in as the inlet manifold pressure increases. The additional air flow makes it possible to maintain the combustion chamber pressure and fuel/air load even at high engine revolution speeds, increasing the power and torque output of the engine. Because the pressure in the cylinder must not go too high to avoid detonation and physical damage, the intake pressure must be controlled by venting excess gas. The control function is performed by a waste gate, which routes some of the exhaust flow away from the turbine. This regulates air pressure in the intake manifold.

Classification of Gears

Classification of Gears

Classification of gears can be done according to relative position of the axes of revolution into three types. They are:

1.      Gears for Parallel shafts

1.1 Spur Gears

1.2 Helical Gears

1.3 Herringbone Gears

1.4 Rack and Pinion

2.      Gears for Intersecting Shafts

2.1 Straight Bevel Gears

2.2 Spiral Bevel Gears

3.      Gears for Skew Shafts

3.1 Hypoid Gears

3.2 Worm Gears

Classification about these types of gears discussed below.

1. Gears for Parallel Shafts:
The motion between parallel shafts is same as to the rolling of two cylinders. Gears under this category are the following:

1.1 Spur Gears:

Straight Spur gears are the simplest form of gears having teeth parallel to the gear axis. The contact of two teeth takes place over the entire width along a line parallel to the axes of rotation. As gear rotate , the line of contact goes on shifting parallel to the shaft.

1.2 Helical Gears:

In helical gear teeth are part of helix instead of straight across the gear parallel to the axis. The mating gears will have same helix angle but in opposite direction for proper mating. As the gear rotates, the contact shifts along the line of contact in in volute helicoid across the teeth.

SPARK PLUG

SPARK PLUG:-

Spark plug is a device used to produce electric spark to ignite the compressed air fuel mixture inside the cylinder. The spark plug is screwed in the top of the cylinder so that it electrode project in the combustion chamber.

A spark plug consist of mainly three parts:

1. Center electrode or insulated electrode.

2. Ground electrode or outer electrode.

3. Insulation separating the two electrodes.

The upper end of the centre electrode is connected to the spark plug terminal, where cable from the ignition coil is connected. It is surrounded by insulator. The lower half portion of the insulator is fastened with a metal shell. The lower portion of the shell has a short electrode attached to one side and bent in towards the centre electrode, so that there is a gap between the two electrodes. The two electrodes are thus separated by the insulator. The sealing gaskets are provided between the insulator and the shell to prevent the escape of gas under various temperature and pressure conditions. The lower part of the shell has screw threads and the upper part is made in hexagonal shape like a nut, so that the spark plug may be screwed in or unscrewed from the cylinder head.

Cleaning the Spark Plug

Due to the combustion of fuel in the cylinder, carbon particles deposit on and around the electrode which not only reduce the plug gap but also prevent the spark to occur. If the spark is still occurring, it is too weak that it cannot ignite the fuel. Hence the spark plug is to be cleaned. Carbon particles can deposit due to any reason like, nature of fuel, mixture strength, lubricating oil, etc. The spark plug can be cleaned by a sand paper.

Anti-Lock Braking System (ABS)

Anti-Lock Braking System (ABS)  :-

It is a safety system in automobiles. It prevents the wheels from locking while braking. The purpose of this is to allow the driver to maintain steering control under heavy braking and, in some situations, to shorten braking distances (by allowing the driver to hit the brake fully without skidding or loss of control).

How Do Wheels Lock?

During braking, wheels lock if the brake force applied is more than the friction between the road and tyre. This often happens in a panic braking situation, especially on a slippery road. When the front wheels lock, the vehicle slides in direction of motion. When the rear wheels locks, the vehicle swings around. It is impossible to steer around an obstacle with wheels locked. Locked wheels can thus result in accident. Skidding also reduce tyre life.

 Components:

The anti-lock braking system consists of following components.

Wheel Speed Sensor

The wheel speed sensor consists of a permanent magnet and coil assembly. It generates electrical pulses when the pole wheel rotates. The rate at which the pulses are generated is a measure of wheel speed. The voltage induced increases with the speed of rotation of the wheel and reduces with increasing gap between the pole wheel and the sensor.

Pole Wheel

Pole Wheel is a toothed wheel made of ferrous material. It normally has teeth on the face. In some cases where it is not possible to install the sensor parallel to the axle, the pole wheels are designed with teeth on periphery. The pole wheel fitted on standard 9-20, 10-20 tires has normally 100 evenly spaced teeth. 80 evenly spaced teeth pole wheels are used for the vehicles having the tyre diameter less than 9mm.

Sensor Extension Cable

The sensor extension cable is a two core cable which connects the wheel speed sensor to the Electronic Control Unit. The inner core sheathing is of EPDM rubber and the outer sheathing is polyurethane which provide abrasion resistance to the cable. The cable has a module plug with two pins is connected to the control assembly. The cable has two cores-brown and black in colour.

Electronic Control Unit

The ECU is the core component of the ABS system. Wheel speed sensor signal are the input to the Electronic Control Unit. The ECU computers wheel speeds, wheel deceleration and acceleration. If any wheel tends to lock, the ECU actuates the corresponding Modulator valve to prevent wheel lock. The ECU is normally mounted in driver's cabin.