HOW TO CRACK BHEL EXAMS

                                                           BHEL EXAMS                                                                         
What is BHEL?
         Bharat Heavy Electricals Limited (BHEL) majority-owned and founded by the Government of India, is an engineering and manufacturing company based in New Delhi, India. Established in 1964, BHEL is India's largest power plant equipment manufacturer. The company has been earning profits continuously since 1971-72, except in FY 2015-2016, and paying dividends uninterruptedly since 1976-77.

It has been granted the prestigious Maharatna (big gem) status in 2013 by Govt of India for its outstanding performance and vast scale. The elite list of Maharatna companies contains a total of 7 behemoth Public Sector Undertakings (PSUs) of India. Maharatna status affords the Boards of these companies enhanced financial and operational autonomy.
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What is the format of BHEL exam ?

 There are 240 questions in the paper. Out of 240 120 are Technical and other 120 are Aptitude & General English questions. There is a negative marking of 1/5th mark for each wrong answer. Five options are given for each question of which only one is correct.

The questions are very simple in Aptitude section and can be answered well if practiced well. Time management is an important factor as you have to answer 240 questions in 150 minutes.
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TYPES OF GEARS

                                                             TYPES OF GEARS

                                   

THERE ARE MANY TYPES OF GEARS USED WORLD WIDE BUT HERE ARE SOME MAJORLY USED GEARS AND ITS TYPES:  

1. Spur Gear
2. Helical Gear
3. Herringbone Gear
4. Bevel Gear
5. Worm Gear
6. Rack and Pinion
7. Internal and External Gear
8. Face Gear
9. Sprockets

1] Spur Gear-Parallel and co-planer shafts connected by gears are called spur gears. The arrangement is called spur gearing.

Spur gears have straight teeth and are parallel to the axis of the wheel. Spur gears are the most common type of gears. The advantages of spur gears are their simplicity in design, economy of manufacture and maintenance, and absence of end thrust. They impose only radial loads on the bearings.

Spur gears are known as slow speed gears. If noise is not a serious design problem, spur gears can be used at almost any speed.

 

2)Helical Gear-Helical gears have their teeth inclined to the axis of the shafts in the form of a helix, hence the name helical gears.

These gears are usually thought of as high speed gears. Helical gears can take higher loads than similarly sized spur gears. The motion of helical gears is smoother and quieter than the motion of spur gears.

Single helical gears impose both radial loads and thrust loads on their bearings and so require the use of thrust bearings. The angle of the helix on both the gear and the must be same in magnitude but opposite in direction, i.e., a right hand pinion meshes with a left hand gear.

 

3)   Herringbone Gear - Herringbone gears resemble two helical gears that have been placed side by side. They are often referred to as "double helicals". In the double helical gears arrangement, the thrusts are counter-balanced. In such double helical gears there is no thrust loading on the bearings.

 

4)  Bevel/Miter Gear-Intersecting but co-planar shafts connected by gears are called bevel gears. This arrangement is known as bevel gearing. Straight bevel gears can be used on shafts at any angle, but right angle is the most common. Bevel Gears have conical blanks. The teeth of straight bevel gears are tapered in both thickness and tooth height. 

a)Spiral Bevel gears: In these Spiral Bevel gears, the teeth are oblique. Spiral Bevel gears are quieter and can take up more load as compared to straight bevel gears.

 

b)Zerol Bevel gear: Zero Bevel gears are similar to straight bevel gears, but their teeth are curved lengthwise. These curved teeth of zero bevel gears are arranged in a manner that the effective spiral angle is zero.

 

5)  Worm Gear- Worm gears are used to transmit power at 90° and where high reductions are required. The axes of worm gears shafts cross in space. The shafts of worm gears lie in parallel planes and may be skewed at any angle between zero and a right angle.In worm gears, one gear has screw threads. Due to this, worm gears are quiet, vibration free and give a smooth output.Worm gears and worm gear shafts are almost invariably at right angles.

 

6)      Rack and Pinion- A rack is a toothed bar or rod that can be thought of as a sector gear with an infinitely large radius of curvature. Torque can be converted to linear force by meshing a rack with a pinion: the pinion turns; the rack moves in a straight line. Such a mechanism is used in automobiles to convert the rotation of the steering wheel into the left-to-right motion of the tie rod(s). Racks also feature in the theory of gear geometry, where, for instance, the tooth shape of an interchangeable set of gears may be specified for the rack (infinite radius), and the tooth shapes for gears of particular actual radii then derived from that. The rack and pinion gear type is employed in a rack railway.

 

7)      Internal & External Gear- An external gear is one with the teeth formed on the outer surface of a cylinder or cone. Conversely, an internal gear is one with the teeth formed on the inner surface of a cylinder or cone. For bevel gears, an internal gear is one with the pitch angle exceeding 90 degrees. Internal gears do not cause direction reversal.

8)      Face Gears- Face gears transmit power at (usually) right angles in a circular motion. Face gears are not very common in industrial application.

 

9)  Sprockets-Sprockets are used to run chains or belts. They are typically used in conveyor systems.

THEN THESE ARE ALL THE BASICS OF GEARS 

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THANKING YOU !!!!

ABS explained

                                                             ABS explained   

An anti-lock braking system or anti-skid braking system^[1] (ABS) is an automobile safety system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking, preventing the wheels from locking up (ceasing rotation) and avoiding uncontrolled skidding. It is an automated system that uses the principles of threshold braking and cadence braking which were practiced by skillful drivers with previous generation braking systems. It does this at a much faster rate and with better control than many drivers could manage.

ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces; however, on loose gravel or snow-covered surfaces, ABS can significantly increase braking distance, although still improving vehicle steering control.

Since initial widespread use in production cars, anti-lock braking systems have been improved considerably. Recent versions not only prevent wheel lock under braking, but also electronically control the front-to-rear brake bias. This function, depending on its specific capabilities and implementation, is known as electronic brakeforce distribution (EBD), traction control system, emergency brake assist, or electronic stability control (ESC).

Use

There are many different variations and control algorithms for use in ABS. One of the simpler systems works as follows:

1. The controller monitors the speed sensors at all times. It is looking for decelerations in the wheel that are out of the ordinary. Right before a wheel locks up, it will experience a rapid deceleration. If left unchecked, the wheel would stop much more quickly than any car could. It might take a car five seconds to stop from 60 mph (96.6 km/h) under ideal conditions, but a wheel that locks up could stop spinning in less than a second.
2. The ABS controller knows that such a rapid deceleration is impossible, so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again. It can do this very quickly, before the tire can actually significantly change speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up. This gives the system maximum braking power.
3. This replaces the need to manually pump the brakes while driving on a slippery or a low traction surface, allowing to steer even in most emergency braking conditions.
4. When the ABS is in operation the driver will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves. This pulsing also tells the driver that the ABS has been triggered. Some ABS systems can cycle up to 16 times per second.

thats for now friends . . . . . .

COMPONENTS AND MATERIALS OF AUTOMOBILES ENGINES

COMPONENTS AND MATERIALS OF AUTOMOBILES ENGINES:     

 1) Cam Shafts:

Camshaft is a type of rotating device or apparatus used in piston engines for propelling or operating poppet valves. Camshaft comprises of series of cams that regulates the opening and closing of valves in the piston engines. The camshaft works with the help of a belt, chain and gears.

2)   Crankshaft:

Crankshaft is a device, which converts the up and down movement of the piston into rotatory motion. This shaft is presented at the bottom of an engine and its main function is to rotate the pistons in a circular motion. Crankshaft is further connected to flywheel, clutch, main shaft of the transmission, torque converter and belt pulley.

To convert Reciprocating motion of the Piston into Rotary motion, the Crankshaft and Connecting Rod combination is used. The Crankshaft which is made by Steel Forging or Casting is held on the Axis around which it rotates, by the Main Bearings, which is fit round the main Journals provided.

There are always at least two such bearings,one at the rare end and other at front end.the increase in number of Main Bearings for a given size of the Crankshaft means less possibility of Vibration and Distortion.

But it will also increase the diffculty of correct alignment in addition to increased production cost. The Main Bearings are mounted on the Crankcase of the Engine. The Balance weight or Counter weight keep the system in perfect balance.

The Crank Webs are extended and enlarged on the side of Journal opposite the Crank Throw so as to from balance weights. The Crankshaft may be made from Carbon Steel, Nickel Chrome or other Alloy Steel.

3)    Connecting Rod:

Connecting rods are made of metals, which are used, for joining a rotating wheel to a reciprocating shaft. More precisely, connecting rods also referred to as con rod are used for conjoining the piston to the crankshaft. 

The load on the piston due tocombustion of fuel in the combustion chamber is transmitted to crankshaft through the connecting rod.One end of connecting rod known as small end and is connected to the piston through gudgeon pin while the other end known as big end and is connected to crankshaft through crank pin.

Connecting rods are usually made up of drop forged I section.In large size internal combustion engine,the connecting rods of rectangular section have been employed.In such cases,the larger dimensions are kept in the plane of rotation.

In petrol engine,the connecting rod's big end is generally split to enable its clamping around the crankshaft.Suitable diameter holes are provided to accommodate connecting rod bolts for clamping.The big end of connecting rod is clamped with crankshaft with the help of connecting rod bolt,nut and split pin orcotter pin.

Generally,plain carbon steel is used as material to manufacture connecting rod but where low weight is most important factor,aluminium alloys are most suitable.Nickel alloy steel are also used for heavy duty engine's connecting rod.

Connecting rods can be made of steel, aluminum, titanium, iron and other types of metals.

4)    Crank Case:

A crankcase is a metallic cover that holds together the crankshaft and its attachments. It is the largest cavity within an engine that protects the crankshaft, connecting rods and other components from foreign objects. Automotive crankcases are filled with air and oil, while Magnesium, Cast Iron, Aluminum and alloys are some common materials used to make crankcases.

5)    Cylinder Heads:

Cylinder heads refers to a detachable plate, which is used for covering the closed end of a cylinder assembled in an automotive engine. It comprises of combustion chamber valve train and spark plugs. Different types of automobiles have different engine configurations such as Straight engine has only one cylinder head while a engine has two cylinder heads.

6)    Engine Belts:

Engine belts are the bands made of flexible material used for connecting or joining two rotating shafts or pulleys together. These belts work in coordination with wheels and axles for transferring energy. When the wheels or shafts are positioned at extremely different angles, then the engine belts have the ability to change the direction of a force. Engine pulley is a type of machine or a wheel having either a broad rim or groomed rim attached to a rope or chain for lifting heavy objects

7) Engine Oil System:

Oil is one of the necessities of an automobile engine. Oil is distributed under strong pressure to all other moving parts of an engine with the help of an oil pump. This oil pump is placed at the bottom of an engine in the oil pan and is joined by a gear to either the crankshaft or the camshaft. Near the oil pump, there is an oil pressure sensor, which sends information about the status of oil to a warning light or meter gauge. 

The different parts of engine oil systems include:

a)      Engine Oil

b)      Engine Oil Cooler

c)      Engine Oil Filter

d)     Engine Oil Gaskets

e)      Engine Oil Pan

f)       Engine Oil Pipe

8)    Engine Valve:

Automobile engine valves are devices that regulate the flow of air and fuel mixture into the cylinder and assist in expelling exhaust gases after fuel combustion. They are indispensable to the system of coordinated opening and closing of valves, known as valve train. Engine valves are made from varied materials such as Structural Ceramics, Steels, Superalloys and Titanium alloys. Valve materials are selected based on the temperatures and pressures the valves are to endure.

The primary components of engine valve are:

a)      Inlet Valve

b)      Exhaust Valve

c)      Combination Valve

d)     Check Valve

e)      EGR Valve

f)       Thermostat Valve

g)      Overhead Valve

h)      Valve Guide

i)        Schrader Valve

j)        Vaccum Delay Parts

Inlet Valve & Exhaust Valve-

Function-Inlet valve allow the fresh charge of air-fuel mixture to enter the cylinder bore.Exhaust valve permits the burnt gases to escape from the cylinder bore at proper timing.

9)    Engine Block:

An engine block is a metal casting that serves as a basic structure on which other engine parts are installed. A typical block contains bores for pistons, pumps or other devices to be attached to it. Even engines are sometimes classified as small-block or big-block based on the distance between cylinder bores of engine blocks. Engine blocks are made from different materials including Aluminum alloys, gray cast iron, ferrous alloys, white iron, gray iron, ductile iron, malleable iron, etc.

10)           Engine Pulley:

An engine pulley is a wheel with a groove around its circumference, upon which engine belts run and transmit mechanical power, torque and speed across different shafts of an engine. An engine houses pulley units of different sizes for cam shaft drive, accessory drive and timing belts. Molded plastics, iron and steel are normally used to make engine pulleys.

11)           Engine Brackets:

An engine bracket is a metallic part used to join an engine mount to the power unit or the body of a vehicle. These auto parts are installed between a vehicle's body and power unit to dampen the vibrations generated by the engine, thus preventing a vehicle's body from shaking due to the vibrations. Engine brackets are made from Ductile Iron Cast, Aluminum, Polypropylene, Fiberglass and alloys.

12)           Engine Mounting Bolts:

Automotive mounting bolts secure different automobile components viz. air bags, brake fittings, etc. on to a supporting structure. Likewise, engine mounting bolts help secure an automobile's engine in place. Based on usage, a number of materials such as alloys, silicon bronze, bronze, ceramic, carbon, aluminum, nylon, phosphor bronze, nickel silver, plastic, titanium, zirconium and stainless steel are utilized to produce these bolts.

13)           Piston:

Piston is a cylindrical plug which is used for moving up and down the cylinder according to the position of the crankshaft in its rotation. Piston has multiple uses and functions. In the case of four-stroke engine the piston is pulled or pushed with the help of crankshaft while in the case of compression stroke, piston is pushed with the powerful explosion of mixture of air and fuel. 

Piston comprises of several components namely:

a)      Piston Pins

b)      Piston Floor Mat

c)      Piston Rings

d)     Piston Valve

14)              Piston rings:
Piston rings provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder. The rings serve two purposes:

·         They prevent the fuel/air mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion.

·         They keep oil in the sump from leaking into the combustion area, where it would be burned and lost.

15)           Push Rods:

Push rods are thin metallic tubes with rounded ends that move through the holes within a cylinder block and head, to actuate the rocker arms. Pushrods are found in valve-in-head type engines and are essential for the motion of engine valves. Some commonly used materials for manufacturing pushrods are Titanium, Aluminum, Chrome Moly and Tempered Chrome Moly.

16)           Valve train:

Valve train consists of various components and parts, which enables valves to operate and function smoothly. Valve train comprises of three main components: camshafts, several components which are used for turning the camshaft’s rotating movement into reciprocating movement, and lastly valves and its various parts.

The primary components of valve train are:

a)      Tappet

b)      Rocker Arms

c)      Valve Timing System

17)           Governor

It controls the speed of engine at a different load by regulating fuel supply in diesel engine. In petrol engine, supplying the mixture of air-petrol and controlling the speed at various load condition.

18)           Carburetor

It converts petrol in fine spray and mixes with air in proper ratio as per requirement of the engine.

19)           Fuel Pump

This device supplies the petrol to the carburettor sucking from the fuel tank.

20)       Spark Plug

This device is used in petrol engine only and ignite the charge of fuel for combustion.

21)       Fuel Injector

This device is used in diesel engine only and delivers fuel in fine spray under pressure.

22)       Gudgeon Pin

Connects the piston with small end of connecting rod.

This pin connects the piston with small end of the connecting rod,and also known as piston pin.It is made up of case hardened steel and accurately ground to the required diameters.Gudgeon pins are made hollow to reduce its weight,resulting low inertia effect of reciprocating parts.

This pin is also known as "Fully Floating" as this is free to turn or oscillate both in the piston bosses as well as the small end of the connecting rod.There are very less chances of seizure in this case but the end movement of the pin must be restricted to score the cylinder walls.This can be achieved by using any one of the following three methods,

A) One spring circlip at each end is fitted into the groove in the piston bosses.

B) On spring circlip is provided in the middle.

C) Bronze or Aluminium pads are fitted at both ends of the pin,which prevents the cylinder walls from being damaged.

The gudgeon pin may also be semi-floating type,in which either the pin is free to turn or oscillate in the small end bearing but secured in the piston bosses or it may secured in the small end bearing and allowed a free oscillating movement in the piston bosses.This method provides more bearing area at the bosses and hence no need for providing bushes there in,is preferred.

23)       Crank Pin

Hand over the power and motion to the crank shaft which come from piston through connecting rod.

24)       Sump 

The sump surrounds the crankshaft. It contains some amount of oil, which collects in the             bottom of the sump (the oil pan).

25)          Distributor –

It operates the ignition coil making it spark at exactly the right moment. It also distributes the spark to the right cylinder and at the right time. If the timing is off by a fraction then the engine won't run properly.

HOPE YOU HAVE LEARNED A BIT . . . . . . .. 

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