TOP FIVE RECENT DEVELOPMENT IN MECHANICAL ENGINEERING

1.)First turbine-powered street legal motorcycle -MTT Y2K SUPERBIKE

It’s the Most powerful production bike in the world which runs on diesel with kerosene. It has Rolls Royce-Allison gas turbine engine which produces 420 HP with 678 NM torque. 2-speed automatic transmission transfers excellent power, the top speed is more than 440 kph, weighs 230 kg. The design is great and fabricated from solid billets. It obtained Guinness World Record as the most expensive production motorcycle.

2.)Car engine - most powerful up to now 

The Devel Sixteen V16 Hyper-car - The custom made the real most powerful engine in the world is Devel Sixteen V16 Hyper-car which has 5000-hp, Quad-Turbo, 12.3-Liter V16. this is craziest power ever which has red-line of 8000 - hp. It is first revealed in Dubai Motor show, it reaches PS 0-60 in 1.8 seconds, and a top speed nearing 350 mph.

3.)Toyota launches first mass-market fuel cell car - Mirai, which converts hydrogen into electricity and emits nothing but water drops. It’s going to be the breakthrough in future for other vehicles like Forklifts, trucks, buses.

4.)Self driving Car

Google’s self driving car is almost driver less(manual assist needs in some dangerous turns) with start and stop option and which uses chauffeur system. The LIDAR(combined SONAR and RADAR) technology with Google map works in a precision manner. It uses 64 typical laser beams to find the objects around the car (360 degree). Cost of this system is around US $ 1 lakh. Accuracy, precision is more in this system which enables pre safe. Top speed is 40 kph.

5.)3D printing Technology

3D- printed steam turbine turbo-machinery used to convert Seawater into drinking water which was developed by GE.

Miniaturized Turbine used to compress and stream a mixture of air, salt and water through a hyper-cooling loop that freezes seawater. By freezing the mixture, the salt naturally separates in solid form, leaving just the ice. The ice is then melted, leaving clean water.

TECHNICAL TERMS OF MACHINES TOOLS

1.)REAMER – Multiedged cutting tool having cutting edges arranged down the length of the tool, the teeth (and the flutes) being either straight and parallel to the axis or alternatively helical with a lead opposite to the direction of rotation.

2.)RECESSING TOOL – Type of tool employed to cut recesses in bored holes.

3.)SCREW PLATE – A set consisting of the more commonly used taps and dies, a tap wrench, and a die stock, cased in a wooden box.

4.)SCREW SLOTTING SAWS – A series of thin saws of various widths,generally used in an automatic screw machine but sometimes in a milling machine, to cut the slots in the heads of screws.

5.)SURFACE GRINDER– It is a general purpose machine tool used to finish machine a plane surface. There are two types—horizontal and vertical.

6.)PLAIN MILLER – Milling machine in which milling can be carried out in a direction parallel with the axis of the arbor or at right angles to it ,but no swivelling of the worktable is possible.

7.)MACHINE TOOL – Type of power driven machine for cutting metal as employed in machine shops, the term being usually restricted to those which use the tool that produces waste material in the form of chips or cuttings. Typical machine tools are lathes, planers, shapers, slotters, borers, drills, broaches, millers and saws.

8.)MANDREL PRESS – Press for the purpose of fitting mandrels to the bore of the work.

9.)JIG BORING MACHINE – An extremely accurate machine tool having a precession spindle and a table to hold the work. The table and spindle are movable with built in measuring devices. Used for spacing and producing precision holes in tools, dies, and small lot production where extreme accuracy is required.

10.)KNUCKLE PRESS – Press designed to exert a great pressure. It is a strong,
heavily built and a rather slow-moving machine, and the standard range varies from 60-100 tons per sq.inch.

10 SKILLS EVERY MECHANICAL ENGINEER SHOULD HAVE !!

These are the skills a good mechanical engineer should possess.|

1. Excellent Designing skill. One should be able to design a mechanical system perfectly, beautifully and with high stability. Eg, say design chassis for car?

2. Ok, now not only Designing, one must have Good Analytical Skill

He must know how to analyze each component in a mechanical system, like to detect flaws, solve problems etc. How to do cost-benefit analysis? How to Qualitative analysis and Quantitative analysis!

3. After analysis? What? OPTIMIZATION.! 
Yes, ofcourse optimization is required anyhwere to make a system work with more efficacy. SO, he must be optimistic and optimize the system!

3. Should be good in softwares like AutoCAD, SOLIDWORKS, CATIA, ANSYS, LOTUS etc. Yes, all the softwares.

4. Thorough with Basics of everything of your Engineering Field.. Yes, actually fundamentals are very tough because many took it as it is to mind without even thinking about it. (esp subjects like, Automobile, Thermodynamics, Fluid dynamics and mechanics, Material Science, Metallurgy, Structural Engineering, etc)

Without understand fundamentals, we study something tough/higher level,and we call these fundamentals as ‘basics’, which is not supposed to be called. THis is very important, will yield better understanding, or you may even become a scientist ?!

5. Good problem solving skills and decision making skills. Where ever one goes, one has to take good decisions and solve problems, esp in a company. It should distrupt others very less, and should be of more efficacy.

So this is essential. To develop this, |
-> Prepare for Aptitude (Verbal, Reading, Quants, Data interpreations & Logical reasoning )
By preparing this aptitude, you acquire good skills intuitively. This will also help you in cracking interviews, but ultimate purpose is to find a person who is good with these skills.|
So, before starting, know why! and then prepare.! This will drive you like anything!

6. These days every system is integrated. Say, mechanical is automated. So,

Skills like,

a) Coding skill (C/C/++)
b) Embedded systems,
c) Mechatronics, are essential.

If possible, build your skill by availing more knowledge on basic Embedded coding like Arudino, PIC controllers and learn to build any small system like Line follower robots, or any mini project based on that. This is essential

7. Good Negotiation skill.

8. Good marketing and advertising Skill.

9. Fundamentals Project Management must be known for all engineers, obvious for mechanical engineers too. Making reports, charts like Gantt etc, are important.

10. Learn to sell yourself. If you can sell yourself, you can sell anything. Mechanical engineers should posses high Intergrity and confidence.

This is important as mechanical engineers will be working with engineers of all other domains. Develop good ethics . Good communication skill is required. Good English. Overall, develop your personality.

TECHNICAL TERMS OF I.C ENGINES EXPLAINED (PART - 2)

1.)COMBUSTION SWIRL – Air motion created by the ejection of the combustion products from the precombustion chamber into the clearance space above the piston.

2.)COMMON RAIL SYSTEM – The fuel injection system which consists of a high pressure pump which distributes the fuel to a common rail or header to which injectors are connected.

3.)CONSTANT PRESSURE COMBUSTION – Combustion which occurs without a change in pressure. In an engine, this is obtained by a slower rate of burning than with constant volume combustion.

4.)DIESEL KNOCK – Sudden, steep pressure rise due to instantaneous
uncontrolled combustion of the fuel that has got accumulated during delay period. The pressure wave hitting piston and cylinder walls produce knocking sound.

5.)ENGINE DERATING – Reducing maximum fuel flow to the engine.

6.)GLOW PLUG– is an electrical heater, which is switched on for quick starting
in cold weather. Its heating element protrudes directly into the combustion chamber in DI engines.

7.)INJECTION TIMING – Crank angle with respect to TDC at which fuel
injection starts, during the compression stroke.

8.)PHYSICAL DELAY PERIOD – The time that elapses between the begining
of fuel injection and the beginning of preflame reactions.

9.)PILOT INJECTION– is the early injection of a small quantity of fuel to
initiate combustion of the injected main fuel, in a diesel engine.

10.)TURBULENCE CHAMBER – A combustion chamber connected to the
cylinder through a throat. Fuel is injected across the chamber and turbulence is produced in the chamber by the air entering during compression.

FLUID FLYWHEEL EXPLAINED !!

Introduction:
A fluid coupling or hydraulic coupling is a hydrodynamic device used to transmit rotating mechanical power. It has been used in automobile transmissions as an alternative to a mechanical clutch. It also has widespread application in marine and industrial machine drives, where variable speed operation and controlled start-up without shock loading of the power transmission system is essential.

Construction:

Fluid  fluid couplings work on the hydrodynamic principle. It consists of a pump-generally known as impeller and a turbine generally known as rotor, both enclosed suitably in a casing. The impeller and the rotor are bowl-shaped and have large number of radial vanes. They face each other with an air gap. The impeller is suitably connected to the prime mover while the rotor has a shaft bolted to it. This shaft is further connected to the driven machine through a suitable arrangement. Oil is filled in the fluid coupling from the filling plug provided on its body. A fusible plug is provided on the fluid coupling which blows off and drains out oil from the coupling in case of sustained overloading.

Working :

Let's take an example that two fans a placed in front of each other as shown in figure below.As one fan is turned ON the blades of fan which is OFF is turned automatically.So,here is no any mechanical connection between two blades of fan but one is moving other.Similarly,there is no mechanical interconnection between the impeller and the rotor (i.e. the driving and driven units) and the power is transmitted by virtue of the fluid filled in the coupling. Hydraulic fluid couplings transfer rotational force from a transmitting axis to a receiving axis.The impeller when rotated by the prime mover imparts velocity and energy to the fluid, which is converted into mechanical energy in the rotor thus rotating it. 

Although fluid couplings use hydraulic fluid within their construction, the mechanism loses a portion of its force to friction and results in the creation of heat. No fluid coupling can run at 100 percent efficiency. Excessive heat production from poorly maintained couplings can result in damage to the coupling and surrounding systems.

TECHNICAL TERMS OF HEAT TRANSFER AND THERMODYNAMICS EXPLAINED !!

1.)ENTHALPY – Name given to the total heat in the fluid at any temperature.

2.)EXTRINSIC PROPERTIES– Also called extensive properties, are those properties which are dependent on the mass of the system. Examples are volume, weight and total energy.

3.)FACTOR OF EVAPORATION – A quantity which when multiplied by the amount of steam generated at a given pressure from water at a given temperature, gives the equivalent evaporation from and at 100°C.

4.)FREE EXPANSION– is a process wherein a fluid from a pressure chamber expands into a vacuum chamber through an orifice of large dimensions.

5.)GAUGE PRESSURE – Pressure above or below atmospheric pressure.

6.)HEAT SINK – A means for disposing of unwanted heat, usually by using it to increase the temperature of water, which is then run to waste.

7.)HEAT SOURCE – Supplier of heat to the working agent of a heat engine-a fraction of the heat supplied being changed into work.

8.)HYPERBOLIC PROCESS– is one in which a gas is heated in such a way that at any instant its pressure multiplied by its volume remains constant.

9.)IDEAL GAS– is one which will obey all the gas laws, under all conditions of temperature and pressure. For an ideal gas, the internal energy and enthalpy are functions of temperature alone.

10.)INTERNAL ENERGY – is the energy arising from the motion and from configuration of the internal particles (atoms and molecules). It is the energy stored in the gas and is used for raising its temperature.

MECHANICAL ENGINEERING INTERVIEW QUESTIONS !!

1. Explain the second law of thermodynamics.

The entropy of the universe increases over time and moves towards a maximum value.

2. What kinds of pipes are used for steam lines?

Normally galvanized pipes are not used for steam. Mild steel with screwed or welded fittings are the norm. Pressure and temperature are very important factors to be considered in what type of materials to be used. Steam even at low pressures can be extremely dangerous.

3. What is the difference between projectile motion and a rocket motion?

A projectile has no motor/rocket on it, so all of its momentum is given to it as it is launched. An example of a projectile would be pen that you throw across a room.
A rocket or missile does have a motor/rocket on it so it can accelerate itself while moving and so resist other forces such as gravity.

4. What is a cotter joint?

These types of joints are used to connect two rods, which are under compressive or tensile stress. The ends of the rods are in the manner of a socket and shaft that fit together and the cotter is driven into a slot that is common to both pieces drawing them tightly together. The tensile strength of the steel is proportionate to the strength needed to offset the stress on the material divided by the number of joints employed.

5. What is the alloy of tin and lead?

A tin and lead alloy is commonly called solder. Usually solder is a wire with a rosin core used for soldering. The rosin core acts as a flux.

6. What is annealing?

It is a process of heating a material above the re-crystallization temperature and cooling after a specific time interval. This increases the hardness and strength if the material.

7. What is ductile-brittle transition temperature?

It is the temperature below which the tendency of a material to fracture increases rather than forming. Below this temperature the material loses its ductility. It is also called Nil Ductility Temperature.

8. What is a uniformly distributed load?

A UDL or uniformly distributed load is a load, which is spread over a beam in such a way that each unit length is loaded to the same extent.

9. What are the differences between pneumatics and hydraulics?

a) Working fluid: Pneumatics use air, Hydraulics use Oil
b) Power: Pneumatic power less than hydraulic power
c) Size: P components are smaller than H components
d) Leakage: Leaks in hydraulics cause fluid to be sticking around the components. In pneumatics, air is leaked into the atmosphere.
e) Pneumatics obtain power from an air compressor while hydraulics require a pump
f) Air is compressible, hydraulic oil is not

10. What is enthalpy?

Enthalpy is the heat content of a chemical system.

TECHNICAL TERMS OF AUTOMOTIVE VEHICLES

1.)AERODYNAMIC DRAG– is the air resistance to the motion of the vehicle.This consists of profile drag, induced drag, skin friction drag, interference drag, and cooling and ventilation drag.

2.)AERODYNAMIC LIFT– is the vertical component of the resultant force caused by the pressure distribution on the vehicle body.

3.)AIR BRAKE – A braking system which uses compressed air to supply the effort required to apply brakes.

4.)BOOSTER – Device incorporated in a car system (such as brake and steering),to increase pressure output or decrease amount of effort required to operate or both.

5.)CAMBER ANGLE – The outward (positive) or inward (negative) angle of the wheel centre line to absolute vertical.

6.)CASTER ANGLE – The rearward (positive) or forward (negative) angle of the steering axis to absolute vertical.

7.)CLUTCH PEDAL – A pedal in the drivers compartment that operates the clutch.

8.)CLUTCH SLIPPAGE – A condition in which the engine over revs during shifting or acceleration.

9.)DUAL BRAKE SYSTEM – Tandem or dual master cylinder to provide a brake system that has two separate hydraulic systems, one operating the front brakes, the other operating the rear brakes.

10.)EPICYCLIC GEAR– In the epicyclic gearing, at least one gear not only rotates about its own axis, but also rotates about some other axis.

NEW PRODUCT DEVELOPMENT PROCESS EXPLAINED !!

NEW PRODUCT DEVELOPMENT PROCESS:-

New product development (NPD) covers the complete process of bringing a new product to market. New product development is described as the transformation of a market opportunity into a product available for sale.

The eight stages or process or steps involved in the development of a new product are listed as follows:

1. Idea generation (Problem identification)

The first step in new-product development is idea generation.

New ideas can be generated by:

• ·         Conducting marketing research to find out the consumers' needs and wants.
• ·         Inviting suggestions from consumers.
• ·         Inviting suggestions from employees.
• ·         Brainstorming suggestions for new-product ideas.
• ·         Searching in different markets viz., national and international markets for new-product ideas.
• ·         Getting feedback from agents or dealers about services offered by competitors.
• ·         Studying the new products of the competitors.

·         

2. Idea screening (Problem Definition)

Most companies have a "Idea Committee." This committee studies all the ideas very carefully. They select the good ideas and reject the bad ideas.

Before selecting or rejecting an idea, the following questions are considered or asked:

• ·         Is it necessary to introduce a new product?
• ·         Can the existing plant and machinery produce the new product?
• ·         Can the existing marketing network sell the new product?
• ·         When can the new product break even?

If the answers to these questions are positive, then the idea of a new-product development is selected else it is rejected. This step is necessary to avoid product failure.

3. Concept Generation

In concept generation product concepts like physical dimensions,functionality and specifications are generated.

4. Concept testing

Concept testing is done after concept generation. It is different from test marketing.

In this stage of concept testing, the company finds out:

• ·         Whether the consumers understand the product idea or not?
• ·         Whether the consumers need the new product or not?
• ·         Whether the consumers will accept the product or not?

Here, a small group of consumers is selected. They are given full information about the new product. Then they are asked what they feel about the new product. They are asked whether they like the new product or not. So, concept testing is done to find out the consumers' reactions towards the new product. If most of the consumers like the product, then business analysis is done.

5. Business analysis

Business analysis is a very important step in new-product development. Here, a detailed business analysis is done. The company finds out whether the new product is commercially profitable or not.

Under business analysis, the company finds out...

• ·         Whether the new product is commercially profitable or not?
• ·         What will be the cost of the new product?
• ·         Is there any demand for the new product?
• ·         Whether this demand is regular or seasonal?
• ·         Are there any competitors of the new product?
• ·         How the total sales of the new product be?
• ·         What will be the expenses on advertising, sales promotion, etc.?
• ·         How much profit the new product will earn?

So, the company studies the new product from the business point of view. If the new product is profitable, it will be accepted else it will be rejected.

6. Product development

At this stage, the company has decided to introduce the new product in the market. It will take all necessary steps to produce and distribute the new product. The production department will make plans to produce the product. The marketing department will make plans to distribute the product. The finance department will provide the finance for introducing the new product. The advertising department will plan the advertisements for the new product. However, all this is done as a small scale for Test Marketing.

7. Test marketing

Test marketing means to introduce the new product on a very small scale in a very small market. If the new product is successful in this market, then it is introduced on a large scale. However, if the product fails in the test market, then the company finds out the reasons for its failure. It makes necessary changes in the new product and introduces it again in a small market. If the new product fails again the company will reject it.

Test marketing reduces the risk of large-scale marketing. It is a safety device. It is very time-consuming. It must be done especially for costly products.

8. Commercialization

If the test marketing is successful, then the company introduces the new product on a large scale, say all over the country. The company makes a large investment in the new product. It produces and distributes the new product on a huge scale. It advertises the new product on the mass media like TV, Radio, Newspapers and Magazines, etc.

9. Review of market performance

The company must review the marketing performance of the new product.

It must answer the following questions:

• ·         Is the new product accepted by the consumers?
• ·         Are the demand, sales and profits high?
• ·         Are the consumers satisfied with the after-sales-service?
• ·         Are the middlemen happy with their commission?
• ·         Are the marketing staffs happy with their income from the new                   product?
• ·         Is the Marketing manager changing the marketing mix according to            the changes in the environment?
• ·         Are the competitors introducing a similar new product in the market?

The company must continuously monitor the performance of the new product. They must make necessary changes in their marketing plans and strategies else the product will fail.

TECHNICAL TERMS OF FUEL AND COMBUSTION !!

1.)ADDITIVE – A substance added to fuel, or oil or grease which improves
the properties of the same.

2.)AFTER BOIL – Boiling of the fuel in the carburettor or coolant in the engine immediately after the engine is stopped.

3.)AFTER BURNING – In an internal combustion engine, the persistence of the combustion process beyond the period proper to the working cycle,i.e., into the expansion period.

4.)ANILINE POINT – The lowest temperature at which an oil is completely miscible with an equal volume of aniline.

5.)ATOMIZATION – The spraying of a liquid through a nozzle so that the liquid is broken into a very fine mist

6.)BACKFIRE (exhaust system) – Passage of unburned air fuel mixture into the exhaust system where it is ignited by some hot spot and causes a
loud explosion.

7.)CATALYTIC CONVERTER – A muffler like device for use in an exhaust system that converts harmful gases in the exhaust into harmless gases by promoting a chemical reaction between a catalyst and the pollutants.

8.)DETONATION – An uncontrolled instantaneous second explosion in a spark ignition engine, after the spark occurs, with excessively rapid burning of a portion of the compressed air fuel mixture (end charge almost exploding) resulting in a spark knock, or pinging noise.

9.)FLASH POINT– It is the temperature at which the quantities of vapour which a combustible fuel emits into the atmosphere are sufficient to allow a spark to ignite the vapour air mixture above the fluid.

10.)PING – The sound resulting from sudden auto ignition of the airfuel charge in a SI engine combustion chamber. Characteristic sound of detonation.

FIRST LAW OF THERMODYNAMICS EXPLAINED !!

The First law of thermodynamics states that energy is neither created nor destroyed. Thus the total energy of the universe is a constant. However, energy can certainly be transferred from one form to another form.

The 1^st law of thermodynamics can be mathematically stated as follows:

§dQ (HEAT) = §dW (WORK)

During a thermodynamic cycle, a cyclic process the systems undergoes, the cyclic integral of heat added is equal to integral of work done. The first law equation can also be written in the form,

§(dQ – dW) = 0

Equation dU = dQ – dW is a corollary to the first law of thermodynamics. It shows that there exists a property internal energy (U) of the system, such that a change in its value is equal to the difference in heat entering and work leaving the system.

Another property named enthalpy (H) can also be defined now as a combination of properties U, p and V.

H = U + pV

For a reversible process, since dW = pdV, the first law of thermodynamics can also be written as

dQ = dU + pdV

IMPORTANT TERMS OF WELDING EXPLAINED !!

1.)BACKHAND WELDING – A welding technique in which the welding
torch or gun is directed opposite to the progress of welding.

2.)BACK WELD – A weld deposited at the back of a single groove weld.

3.)COLD WELDING – A solid state welding process in which pressure is applied at room temperature to produce coalescence of metals with substantial deformation at the weld.

4.)DEPTH OF FUSION – Distance that fusion extends into the base metal or previous pass from the surface melted during welding.

5.)DIFFUSION WELDING – A solid state welding process that produces coalescence of the faying surfaces by the application of pressure at elevated temperature.

6.)ELECTRO SLAG WELDING – A welding process producing coalescence of metals with molten slag that melts the filler metal and the surfaces of the workpieces. The weld pool is shielded by slag.

7.)FILLER METAL – Metal to be added in making a welded, brazed or soldered joint.

8.)FUSION ZONE – Area of base metal melted as determined on the crosssection of a weld.

9.)POST HEATING – Application of heat to an assembly after a welding,brazing, soldering, thermal spraying or thermal cutting.

10.)PRE HEATING – Application of heat to the base metal immediately before
welding, brazing, soldering, thermal spraying and cutting.

TERMINOLOGIES OF FRICTION AND LUBRICATION (PART-1)

1.)ABSOLUTE VISCOSITY – Force per unit area required to move a surface at unit velocity, when it is separated by a fluid of unit thickness from a stationary surface.

2.)ADDITIVES – Chemical compounds used to alter the characteristics of lubricating oils.

3.)ANGLE OF REPOSE – The minimum inclination which a plane can have consistent with the body on it sliding down the plane by the force of gravity. It is the same as the friction angle.

4.)ANTI OXIDATION ADDITIVES – Chemical compounds added to decrease oxidation of the oil. These have a greater affinity for oxygen than does the oil.

5.)BATH LUBRICATION – Lubrication system in which the bearing contains a space filled with oil, which is in contact with a portion of the journal.

6.)BEARING OIL CLEARANCE – The space purposely provided between the revolving shaft and the bearing in which it rotates. Through this space lubricating oil can flow.

7.)CENTIPOISE – A unit of viscosity of a fluid used in figuring pressure drop etc.

8.)CRITICAL SPEED – The limiting or critical speed corresponding to a given pressure is that speed at which surface irregularities may intervene and so lead to seizure.

9.)FILM LUBRICATION – Type of lubrication in which the two metallic surfaces are separated by a continuous film of liquid oil of measurable thickness which forces itself between them.

10.FIRE POINT OF OIL – The temperature at which the oil vapour on the oil surface ignites and burns for at least five seconds, when heated gradually, under specified test conditions.

NOTES ON ELECTRON BEAM MACHINING !!

Electron beam machining (EBM) :-


Electron beam machining (EBM) is one of several industrial processes that use electron beams. Electron beam machining uses a high-velocity stream of electrons focused on the workpiece surface to remove material by melting and vaporization. A schematic of the EBM process is illustrated in the figure: 

An electron beam gun generates a continuous stream of electrons that are focused through an electromagnetic lens on the work surface. The electrons are accelerated with voltages of approx. 150,000 V to create velocities over 200,000 km/s. The lens is capable of reducing the area of the beam to a diameter as small as 0.025 mm. On impinging the surface, the kinetic energy of the electrons is converted into thermal energy of extremely high density, which vaporizes the material in a very localized area. EBM must be carried out in a vacuum chamber to eliminate collision of the electrons with gas molecules.

Electron beam machining is used for a variety of high-precision cutting applications on any known material. Applications include drilling of extremely small diameter holes, down to 0.05 mm diameter, drilling of holes with very high depth-to-diameter ratios, more than 100:1, and cutting of slots that are only about 0.025 mm wide. Besides machining, other applications of the technology include heat treating and welding.

The process is generally limited to thin parts in the range from 0.2 to 6 mm thick. Other limitations of EBM are the need to perform the process in a vacuum, the high energy required, and the expensive equipment.

DIFFERENCE BETWEEN DRILLING,BORING AND REAMING EXPLAINED !!

Drilling is a process of producing round holes in a solid material or enlarging existing holes with the use of multitooth cutting tools called drills or drill bits. Various cutting tools are available for drilling, but the most common is the twist drill.

In machining, boring is the process of enlarging a hole that has already been drilled (or cast) by means of a single-point cutting tool (or of a boring head containing several such tools), such as in boring a gun barrel or an engine cylinder. Boring is used to achieve greater accuracy of the diameter of a hole, and can be used to cut a tapered hole. Boring can be viewed as the internal-diameter counterpart to turning, which cuts external diameters.

Reaming is a process of improving the quality of already drilled holes by means of cutting tools called reamers. Drilling and reaming are performed on a drilling press, although other machine tools can also perform this operation, for instance lathes, milling machines, machining centers. 

In drilling and reaming, the primary motion is the rotation of the cutting tool held in the spindle. Drills and reamers execute also the secondary feed motion. Some finishing reaming operations are manual.

CHECK OUT WHY DO WE MIX OIL WITH FUEL IN 2 STROKE ENGINES BUT NOT IN 4 STROKE ENGINE !!

In a 4 stroke engine, we have a dedicated system for lubrication. We have lubricating ports which supply the lubricating oil from the sump so that all the parts are thoroughly cooled. 

But most of the two stroke engines can't use such dedicated lubrication systems because in two stroke engines the inlet and outlet (exhaust) bores are on the sidewalls of the cylinder.

So if a splash type or pump based lubrication systems as used in four stroke engines would be used in two stroke engines then the lubricating oil may enter these bores and block them. 

Moreover, unlike four stroke engines in which there is an oil sump inside the crank-case, the crank-case in two stroke engines is used for pumping and circulating air-fuel mixture to the combustion chamber (thus making it unusable for storing lubricating oil ). So, instead of using a dedicated lubrication system as in four stroke engines, most of the two stroke engines use a lubricant oil mixed with fuel so that the wear of piston and cylinder liner can be minimised. So while fueling, we mix gasoline with an oil to be distributed throughout the engine for lubrication. The two-stroke oil is ultimately burned along with the fuel. But this can contribute to more smoke and distinctive odor.

TECHNICAL TERMS OF GAS TURBINES EXPLAINED !!

1.)AIRFOIL DRAG FORCE – Force acting on the airfoil in the direction of motion, represents frictional forces.

2.)AIRFOIL LIFT FORCE – Force acting on the airfoil in the direction perpendicular to the direction of motion. Basic force causing the aeroplane to maintain its lift.

3.)AIR RATE – Kilograms per second of airflow required per net horse powerdeveloped. Also called FLOWRATE.

4.)CLOSED CYCLE TURBINE – Turbine in which the working fluid does not come in contact with the atmospheric air and the heat to theworking fluid is provided in the heater by burning the fuel externally.

5.)COMPRESSOR MECHANICAL EFFICIENCY – Ratio of rotor horse power to shaft horse power supplied to the compressor.

6.)CONSTANT PRESSURE TURBINE – Turbine in which the fuel is burnt at constant pressure. Combustion is a continuous process.

7.)CONSTANT VOLUME TURBINE – Turbine in which the combustion takes place at constant volume. Also called EXPLOSION TYPE TURBINE.

8.)ISENTROPIC EFFICIENCY – Ratio of work to compress isentropically to the actual work to compress. Also the ratio of isentropic temperature rise to the actual temperature rise.

9.)POWER RATIO – Ratio of useful or net horse power of the cycle comparedwith the power developed by the turbine of the system. Also called WORK RATIO.

10.)RAM EFFECT – The effect which causes an increase of temperature and pressure of the air that enters the compressor of an aircraft gas turbine unit due to aircraft speed. Sometimes called RAM.