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  1. 2 points
    It could be that I'm going blind but I didn't see the word 'better' in any part of the question!
  2. 2 points
    I was drawing the diagram of the cycle and I could notice that the flash chamber creates a decreasing both the Entropy and Temperature to send the leaving one-stage vapour, to the high-pressure compressor. With the purpose of increase the COP and decrease the compressor power input.
  3. 2 points
    Lisho Thomas

    Why tyres are made black in color?

    Tyres are mixture of various rubbers with carbon black added. Carbon black improves traction and wear resistance of pure rubber. Another reason is that black color has higher absorption capability by which the tyre of any vehicle becomes adhesive to road
  4. 2 points
    Mechanical Engineering is passion or liking..... I really don't know how to explane ..... this is like some one is poet or writer .... very interesting field and never ending ... keeps you fit in this world
  5. 1 point
    What is the function of flash chamber in multistage refrigeration system? You can answer this question. You can like the best answer. You can share the question You can get updates of new questions on Facebook linkedin twitter & google plus
  6. 1 point
    1. What are the differences between true stress, engineering stress, proof stress. 2. What do you men by factor of safety and what is its significance 3. What do you mean by Young’s modulus, modulus of rigidity and bulk modulus. 4. What do you mean by resilience. 5. What is pure torsion and what do you mean by flexural igidity. 6. What is the difference between endurance limit stree and endurance strength. 7. What do you understand by efficiency of riveted joint. 8. What is caulking and fullering in riveted joint. 9. What do you mean by stress conc. Factor and what are the methods to reduce stress conc. 10. Why stress conc. Is more serious in brittle materials. 11. What do you mean by fatigue . 12. Springs are subjected to which type of streses. 13. What are the difference between through bolt, tap bolt and stud. 14. What is check nut and what is the function of washer. 15. Cotter and knuckle joints take which type of load and where they are used. 16. What are the difference types of couplings and what is their function. 17. What is the function of key and which type of stress they are subjected to? 18. Generally shafts are subjected to which type of stress. 19. What are the difference types of mechanical drives and which is the best for different situations. 20. What is the function of a bush why it is phosphor bronze. 21. What are difference types of threads and which threads are used for power transmission and why. 22. Why the pulley arms are elliptical in cross section and it is made up of cast iron. 23. Why it is required to change the all V belt if one of them is broken. 24. Why V belts transmit more power than flat belts. 25. What is the meaning of 6*37 or 6*7 in a rope drive. 26. What do you mean by pinion sprocket and wheel sprocket and which one is used for driving shaft. 27. What is the function of flywheel and why its material is cast iron. 28. Why the leaf springs are laminated as reducing length. 29. What is the function of clutch and is the difference between uniform wear and uniform pressure. 30. Now a days which type of clutches are used in automobiles. 31. Why disc brake is more efficient than mechanical brake. 32. What is the function of bearings and what are the different types. 33. What is bearing characteristics number and bearing modulus. 34. What is the significance of the digits of a rolling contact bearing number 6304? 35. Which type of gear drive is used for perpendicular transmission of power? 36. Why helical gears transmit more power than spur gears. 37. What do you mean by different terms like back lash, pressure angle, circular pitch in a gear drive. 38. Why involute tooth profile is better than cycloid tooth profile? 39. What is interference in gear drive and how to avoid it? 40. What do you mean by law of gearing
  7. 1 point

    Pan Tilt Vibration Stability

    The term "Pan and Tilt Control System" does not have a universal definition, so no one can be sure what you are talking about. If you want help, give a detailed description of what you need to build, including one or more sketches of the proposed system. Only than can anyone give you a meaningful answer. DrD
  8. 1 point
    Im intrested in motorized wheel chair please help me do that project
  9. 1 point
    HEre's throwing you a bone.... How about floating windmills. You design windmills on a floating platform, much like offshore oil platform/rig. Consideration of the ocean wave and current... also the wind conditions.
  10. 1 point
    Moment is used particularly for static analysis and it results in bending. Torque is used particularly for dynamic analysis and it results in rotation. I hope this would be helpful.
  11. 1 point
    Tom Shichenje Azangalala


    you can in 3D it depends with the software? i can help you.
  12. 1 point
  13. 1 point

    Jigs and fixtures

    From the album Engineering images 10

    What are Jigs? Jigs are the work holding device which holds, supports and locate the workpiece and guides tools to perform a specific operation. In other words we can say that, jigs are the device which is used for both purposes of holding the workpiece and guiding the tool. It is a tool which is used to control the location and motion of the tool during the operations. Jigs main purpose is to provide repeatability, accuracy and interchangeability in the manufacturing of products. It is used in the unidimensional machining i.e drilling, taping, reaming etc. Jigs are found to be light in weight and have complex designing. In jigs, gauge blocks are not necessary and the cost of jigs is higher. They are the special tools particularly used in drilling, reaming, tapping and boring Operations. Jigs are not fixed to the machine table until a big operation is not required to perform. What are Fixtures? Fixtures are the work holding device which holds, supports and locate the workpiece but not guides the cutting tool to perform a specific operation. In other words the fixtures are only the work holding device that holds, supports and locate the workpiece in desried position to perform any operation. The main purpose of the fixtures is to hold and locate the workpiece during any machining operation in the industries. And to provide repeatability, accuracy and interchangeability in the manufacturing of products. It is used in multidimensional machining i.e. milling, grinding, turning etc. Fixtures are found to be heavy in weight and have less complex designing. In fixtures, gauge blocks may be provided for effective handling and the cost of fixtures is not so high. Fixtures are specific tools used particularly in milling machine, shapers and slotting machine. Fixtures are fixed to the machine table. Difference Between Jigs and Fixtures in Tabular Form: The various difference between jigs and fixtures in the tabular form are given below: S.no Jigs Fixtures 1. It is a work holding device that holds, supports and locates the workpiece and guides the cutting tool for a specific operation. It is a work holding device that holds, supports and locates the workpiece for a specific operation but does not guide the cutting tool 2. jigs are used in unidimensional machining i.e. drilling,reaming, tapping, etc fixtures are used in multidimensional machining i.e. milling,turning,grinding,etc . 3. Jigs are light in weight. Fixtures are rigid and bulky. 4. Gauge blocks are not necessary. Gauge blocks may be provided for effective handling. 5. The jigs are special tools particularly used in drilling, reaming, tapping and boring operation. Fixtures are specific tools used particularly in milling machine, shapers and slotting machine 6. Usually it is not fixed to the machine table. It is fixed to the machine table. 7. Its cost is more. Its cost is less as compared with the jig. 8. Their designing is complex. Their designing is less complex. Summary of Difference Between Jigs and Fixtures Jigs are the device which is used to holds, supports and locate the workpiece and it guides the cutting tool for a specific operation. Fixtures are the device which is used to hold, support and locate the workpiece and they don’t guide the cutting tool. Jigs are used in unidimensional machining whereas fixtures are used in multidimensional machining. In jigs, gauge blocks is not necessary. In fixtures gauge blocks may provided for effective handling. Jigs are light in weight as compared with the fixtures. The cost of jigs is higher when it is compared with the fixtures. The jigs designing is complex where as fixtures designing is less complex. Jigs are not fitted to the machine table but fixtures are fitted.
  14. 1 point
    What is Powder Metallurgy Process | Advantages and Disadvantages Of Powder Metallurgy Introduction Of Powder Metallurgy The process of manufacturing of shaped components or semi-finished products such as bar and sheet from metal powder is called as Powder metallurgy. The technique of powder metallurgy combines unique technical features with cost effectiveness and generally used to produce sintered hard metals known as ‘carbides’ or ‘tungsten carbides’. This technique deals with the production of metal and non metal powders and manufacture of components. Powder metallurgy is generally used for iron based components. The powders used as raw material can be elemental, pre-alloyed, or partially alloyed. Elemental powders like iron and copper are more compressible and produce pressed compacts with good strength. Pre-alloyed powders are harder but less compressible therefore require higher pressing loads to produce high density compacts. Powder metallurgy technique has many advantage as well as limitation. Two main techniques used to form and consolidate the powder are sintering and metal injection molding. Recent developments have made it possible to use rapid manufacturing techniques which use the metal powder for the products. Because with this technique the powder is melted and not sintered, better mechanical strength can be accomplished. Principles of Powder Metallurgy Process Powder metallurgy is the process of blending fine powdered materials, compacting the same into a desired shape or form inside a mould followed by heating of the compacted powder in a controlled atmosphere, referred to as sintering to facilitate the formation of bonding of the powder particles to form the final part. Thus, the powder metallurgy process generally consists of four basic steps, as indicated in Figure powder manufacture, blending of powders, compacting of powders in a mould or die, and sintering. Compacting is generally performed at room temperature and at high pressure. Sintering is usually done at elevated temperature and at atmospheric pressure. Often, compacting and sintering are combined. Optional secondary processing often follows to obtain special properties or enhanced dimensional precision. Powder Metallurgy route is very suitable for parts that are required to be manufactured from a single or multiple materials (in powder form) with very high strength and melting temperature that pose challenge for the application of casting or deformation processes. Advantages Of Powder Metallurgy: Metal in powder form is costlier than in solid form. Further, expensive dies and equipment needed to adapt this process implies that the process is justified by the unusual properties obtained in the products. Powder metallurgy offers the following specific advantages. Parts can be produced from high melting point refractory metals with respectively less difficulty and at less cost. Production rates are high even for complex parts. This is primarily because of the use of automated equipment in the process. Near net shape components are produced. The dimensional tolerances on components are mostly such that no further machining is needed. Scrap is almost negligible. Parts can be made from a great variety of compositions. It is therefore much easy to have parts of desired mechanical and physical properties like density, hardness toughness, stiffness, damping, and specific electrical or magnetic properties. Parts can be produced with impregnation and infiltration of other materials to obtain special characteristics needed for specific applications. Skilled machinists are not needed, so labour cost is low Parts with controlled porosity can be produced Bi-metallic products, sintered carbides and porous bearings can be produced only by this process. Limitations Of Powder Metallurgy : Powder metallurgy has the following limitations. High cost of metal powders compared to the cost of raw material used for casting or forging a component. A few powders are even difficult to store without some deterioration. High cost of tooling and equipment. This is particularly a limitation when production volumes are small. Large or complex shaped parts are difficult to produce by PM process. Parts have lower ductility and strength than those produced by forging. Uniformly high – density products are difficult to produce. Some powders (such as aluminum, magnesium, titanium and zirconium) in a finally divided state present fire hazard and risk of explosion. Low melting point metal powders (such as of zinc, tin, cadmium) give thermal difficulties during sintering operation, as most oxides of these metals cannot be reduced at temperatures below the melting point. Applications of Powder Metallurgy: There is a great variety of machine components that are produced from metal powders, many of these are put to use without any machining operation carried out on them. Following are some of the prominent PM Products. Filters: Permanent metal powder filters have greater strength and shock resistance than ceramic filters. Cutting Tools and Dies. Cemented carbide cutting tool inserts find extensive applications in machine shops. These are produced by PM from tungsten carbide powder mixed with cobalt binder. Machinery Parts. Several machinery parts including gears, bushes and bearings, sprockets, rotors are made from metal powders mixed with sufficient graphite to give to product the desired carbon content. The parts have nearly 20 percent porosity. The pores of the parts which are to rub against another surface in their use, are impregnated with oil to promote quiet operation. Bearing and Bushes. Bearing and bushes to be used with rotating parts are made from copper powder mixed with graphite. In small quantities, lead or tin may also be added for obtaining better wear resistance. After sintering, the bearings are sized and then impregnated with oil by vacuum treatment. Porosity in the bearings may be as high as 40 percent of the volume. Other machinery parts made by PM include clutch plates, brake drums, ball retainers and welding rods. Magnets. Small magnets produced from different compositions of powders of iron, aluminum, nickel and cobalt have shown excellent performance, far superior to those cast. Electrical Parts. The possibility of combining several metal powders and maintaining some characteristics of each has promoted PM for production of electric contact parts. These parts are required to have excellent electrical conductivity, be wear resistant, and somewhat refractory. Several combinations such as copper – tungsten, cobalt – tungsten, silver – tungsten, copper-nickel, and silver – molybdenum have been used for production of these parts.
  15. 1 point
    The purpose for a governor on at CI engine is the same as the purpose for a governor on any machine: to maintain constant speed under varying load conditions. DrD
  16. 1 point
    Tolerances are allowed so it aid in interchangeability of the product during use, assembly and when subjected to different conditions. It is most derived from the purpose of which the product is to be used for. Environment i.e temperature , application depending on speeds, assembly so it can suit global use.
  17. 1 point
    There is most definitely a difference. Accuracy is the closeness to the desired value. Precision is the closeness to each other. You can be precise in your measurements but be precisely wrong.
  18. 1 point

    Version 1.0.0


    It will give you a brief idea about the cylinder arrangements in an engine
  19. 1 point
    What is mohr's circle used for ? Explain its application. 1. You can answer this question 2. You can like the best answer 3. You can share the question...
  20. 1 point

    What is 'CC' of a bike? How does it matter?

    This is one important point missing in the two previous answers. The "cc rating" of an engine is a volume measure, as previously stated, but it is not the actual cylinder volume. Rather, it is the swept volume of the cylinder, also called the "displacement" of the cylinder. The actual cylinder volume is always somewhat greater than this value because the piston at TDC does not leave zero cylinder volume. The small volume remaining at TDC is called the "clearance volume," the volume available for the early stage of combustion. DrD
  21. 1 point
    With "Gear Hobbing", both Cutter and Gear are in action or rotation, With "Gear Shaping" only the Cutter is in action or rotation ,, tool feed remains the same for both !!
  22. 1 point



    Presentation on Design of- Clutch Brake Belts Chain Gears
  23. 1 point
    Though your question's somewhat vague, intentionally increasing clearance (boring) the cylinders is to increase cylindrical volume, to increase compression ratio and improve power. Unintentionally increased clearance (from wear) will decrease compression ratio due to creating a larger volumetric area which decreases amount of compression per amount of gas allowed in to the cylinder. Also allows for leakage.
  24. 1 point
    Ghajini Mohamad explained well. Torsional rigidity is the force limit before a solid deforms or fatigues. In other words, a solid's resistance (elasticity) to radial twisting (torquing). Lateral rigidity is the force limit forces generated along its axis(es). With a rectangular solid, it can bend (curve) or deform the solid until its sides which are affected by the opposing forces becomes non parallel.
  25. 1 point
    Drill sleeves are often used with drill bits which have tapered shanks. The tapered shank inserts into a sleeve of matching taper in the drill chuck.
  26. 1 point
    Well, to answer this in simple terms.. Rigidity is the maximum resistance an object can offer before it deforms, in other words, it is the minimum force required to deform an object. Torsional Rigidity : The minimum force required to deform an object by twisting through a unit dimension..(in this case, for twisting the dimension is in angle of twist) Lateral Rigidity : Again, the same logic.. The minimum force required to deform an object by bending along the lateral axis through a unit dimension..in this case, the dimension of bending is normally in mm or other length measure scale.. (if the bending load is applied on the longitudinal axis, then the object will not bend, instead the load will act like a compression load), Both Torsional and Lateral Rigidity are considered for the design of shafts with rotating components like gears/pulleys, etc.
  27. 1 point
    It leads to less compression work to second stage of compression, as at first compression temp goes up and pressure develops to get more compressed pressure at output it must intercooled. As pressure increases temp increses so, to avoid higher temp at output it must intercooled
  28. 1 point
    The higher the temperature the harder it is to compress air in smaller volume or in other words the more energy you need to do it. So - lower temperature, smaller amount of energy, higher temperature, larger amount of energy. So once you compress it on stage one, its temperature increases due to molecular collisions in the small volume, if you take away energy in the form of heat, its temperature will fall and now you can again compress it with significant savings of energy because the decrease in temperature has reduced molecular movement inside the small volume making it possible to compress them with smaller amount of energy. So in the end it results with increased effectiveness. This type of system can also be used to take away water vapor from the air that's being compressed, because as you compress the air and you reduce its temperature some of the water vapor inside will condense and fall down in the form of drops.
  29. 1 point
    Prof Dou

    What is priming & why it is done ?

    When a centrifugal pump dry start, the vacuum at the suction will draw air into the system. When there is air in the system pumping efficiency will drop. Priming is the process to get rid of the air drawn in during dry startup.
  30. 1 point
    There is no single answer that applies in all situations. At one point in my career, I was involved in pipeline vibrations work for natural gas transmission pipelines. These pipelines use very large reciprocating compressors to move the natural gas several thousand miles. The discharge from a reciprocating compressor has highly variable pressure as the valves open, the flow moves through the valve, and then the valve closes for the next stroke. These pressure variations, referred to as "pipeline acoustics," cause the entire assembly to shake and can do much fatigue damage to the piping. Fatigue in turn leads to cracks and cracks allow leaks. This is one strong reason for pipeline leaks. DrD
  31. 1 point
    CFD is a computer based flow simulations, where the aim is to solve the Navier-Stokes equations. The equations to be studied are a consequence of the laws of conservation of mass, momentum and energy. FEM is a computer based solid, heat and flow simulations, where the aim is to integrate equations. The equations to be studied are mechanical partial differential equations which are approximated by a set of algebraic equations or a set of ordinary differential equations.
  32. 1 point
    Kesava Moorthi

    Explain why washers are used?

    To protect the bolt hole, spread the load & forces evenly, as a spacer, protect the nut from crevice & galvanic corrosion.
  33. 1 point
  34. 1 point
    damper used to control vibration with the help of resistance and this vibration energy release in the form of heat energy isolator used to support damping and control wave vibration due to shock loads by absorbing the vibration energy.
  35. 1 point
    The foot valve normally found at the bottom of the submerge pump at the column in the tank
  36. 1 point

    What is EDM & When do you need it.

    What is EDM? A Brief History The acronym EDM is derived from Electrical Discharge Machining. The EDM process we know today started with the observations of Joseph Preistly in 1770. He noticed that electrical discharges had removed material from the electrodes in his experiments. This is also known as electro-discharge erosion. In the 1940's two Soviet researchers, the Lazarenkos', developed a machining process that formed the foundation for modern EDM. Electric Discharge MachiningThe basic EDM process is really quite simple. An electrical spark is created between an electrode and a workpiece. The spark is visible evidence of the flow of electricity. This electric spark produces intense heat with temperatures reaching 8000 to 12000 degrees Celsius, melting almost anything. The spark is very carefully controlled and localized so that it only affects the surface of the material. The EDM process usually does not affect the heat treat below the surface. With wire EDM the spark always takes place in the dielectric of deionized water. The conductivity of the water is carefully controlled making an excellent environment for the EDM process. The water acts as a coolant and flushes away the eroded metal particles. Wire Cutting EDM wire cutting uses a metallic wire to cut a programmed contour in a workpiece. Extrusion dies and blanking punches are very often machined by wire cutting. Cutting is always through the entire workpiece. To start machining it is first necessary to drill a hole in the workpiece or start from the edge. On the machining area, each discharge creates a crater in the workpiece and an impact on the tool. The wire can be inclined, thus making it possible to make parts with taper or with different profiles at the top and bottom. There is never any mechanical contact between the electrode and workpiece (see above). The wire is usually made of brass or stratified copper, and is between 0.1 and 0.3 mm diameter. Depending on the accuracy and surface finish needed, a part will either be one cut or it will be roughed and skimmed. On a one cut the wire ideally passes through a solid part and drops a slug or scrap piece when it is done. This will give adequate accuracy for some jobs, but most of the time, skimming is necessary. A skim cut is where the wire is passed back over the roughed surface again with a lower power setting and low pressure flush. There can be from one to nine skim passes depending on the accuracy and surface finish required. Usually there are just two skim passes. A skim pass can remove as much as 0.002" of material or a as little as 0.0001". During roughing ( i.e. the first cut) the water is forced into the cut at high pressure in order to provide plenty of cooling and eliminate eroded particles as fast as possible. During skimming (accuracy / finish cuts) the water is gently flowed over the burn so as not to deflect the wire.
  37. 1 point

    Explain the process of Squeeze Casting

    Squeeze casting as liquid-metal forging, is a process by which molten metal solidifies under pressure within closed dies positioned between the plates of a hydraulic press. The applied pressure and instant contact of the molten metal with the die surface produce a rapid heat transfer condition that yields a pore-free fine-grain casting with mechanical properties approaching those of a wrought product. The squeeze casting process is easily automated to produce near-net to net shape high-quality components.
  38. 1 point
    The original question was, "Why is first angle method preferred over third angle?" I think in the long run, it all comes down to local custom and tradition. Both convery the same information, so neither it truly superior to the other. That said, there is one basis for a good selection that might tilt in favor of one or the other. It is desireable to minimize the number of hidden lines in a drawing, so if one method results in more hidden lines than the other, the second option is preferable. Again though, I think it is a matter of familiarity, what we are all agreed upon, all of which is known as convention.
  39. 1 point
    Its a valve. It is located in the cooling circuit, between the engine and the radiator. If it opens it allows flow of water, assisted by a water pump, to take place from the block to the radiator in order to allow the block to "give up" excessive heat. It is a self regulating device and it is calibrated to open at a particular temperature - usually about 95 degrees C. It has a hysteresis also, that is a gap between the open and close temperature due to mechanical friction within the device itself and therefore after cooling has taken place it may not close again until the temperature drops to 90 degrees C - a hysteresis of 5 degrees C. So in this example, when the engine gets to temperature, it should maintain an operating temperature of between 90-95 degrees C. Why is this important? It is critical for a couple of reasons, firstly the many machined limits and fits of critical moving parts are designed with the prescribed operating temperature in mind. Secondly, and maybe more critically, the lubricating oil viscosity is too thick at low temps and too thin at higher temps. Oil breaks down rapidly when subject to too high a temp and closely machined mechanical parts experience boundary lubrication - that is metal to metal contact. Probably the best way to screw up your engine is to allow it to overheat! Irlanski
  40. 1 point
    When you say "nomenclature," I presume you are speaking of the specifictions (dimensions, materials). Based on that understanding, I think the answer is, with only that, you cannot evaluate the torque. You need to know a good bit about the combustion process that takes place, and that requires a knowledge of the fuels, the temperatures, and a lot of thermodynamics. If you have a credible P-V diagram for the engine at the operating point of interest, then a dynamic analysis of the engine can provide the output torque, based on that P-V diagram. It is not simple, and it requires quite a lot of calculation, but it can be done with some accuracy. But, and this is a big but, it will only be as good as the P-V data you start with.
  41. 1 point
    Drafting is essentially drawing a picture, whether in 2D or 3D, and providing dimensions and notes. A drafter may do some "catalog engineering," (selecting parts such as bearings, seals, etc. from a catalog), but drafters do not use any truly advanced mathematics (as a rule). Design, on the other hand, may be making a sketch, but it is also providing the analysis to justify the selection of component sizes (based on stress, deflection, fatigue, etc.), determination of system dynamic response and assuring that criteria are met, etc. Design goes much, much further than drafting.
  42. 1 point
    1.ram air cooling 2. intermediate ram air cooling 3. surface cooling 4.boiling 5.engine injection cooling 6. auxiliary injection cooling
  43. 1 point
    A foot valve is a check valve.It is installed at suction line's bottom in a centrifugal pump.
  44. 1 point
    clutch is a device use to engage or disengage the shaft of the gearbox to the shaft of wheel, while coupling is used to joint two shaft permanantely or temporary,...
  45. 1 point



    Shear force and Bending moment diagrams 2 Presentations Strength of materials / Mechanics of solid
  46. 1 point
    generally tolerence are required for to control the quality of the product during mfg. GD & T is coontroll the dimension of the product during manufacturing .it mean it give the perticuler range of geometric parameters like surface finish,flatness,strigtness,...etc..., sometime tolerence are given for the purpose of the type of fit requirement between two meting parts, sometime tolerence stack up analysis is also required when more than 2 parts are assembled to each other..
  47. 1 point
    When we manufacture any product, usually we manufacture it by casting or forging process. To get a proper surface finish of that product we need a proper machining. At the time of maching a certain amount of material usually removed from the surface of the core product. For this reason a tolerance is needed over the designed dimension to maintain the actual dimension. Beside this reason, tolerances also kept to maintain the needed dimension after thermal expansion or contraction at the time of solidification during casting process.
  48. 1 point

    For what Fanning diagram is used for?

    Arvind Laad Head Engineering at Creative Ashtech Power Projects Private Limited This diagram is used to find the nature of flow of viscous slurry- whether it is laminar or turbulent. It is also used to derive the coefficient of friction in such cases in order to work out the pressure drop in these pipelines & thus fix the slurry pump parameters.
  49. 1 point
    CC is the Cubic Liters of the Engine. We calculate the bore diameter and Cylinder size and multiply them the result we get t is the CC (cubic centimeter of the Engine) 2.0 L that means is 2000 CC Engine. The total volume we get is 2000 Cubic centimeter.
  50. 1 point
    Ohh god.. No one is able to give right answer. All are copying from other sources.. Let’s discuss it with an example of bicycle. In bicycle while operation the power from pedal is transmitted to small flywheel present in the rear tyre. This flywheel locks in one direction so that power can be transmitted from pedal to rear wheel not from rear wheel to pedal. In order to conserve the kinetic energy of the bicycle. Same thing happens in vehicles. In normal conventional gear box when we release our accelerator pedal the kinetic energy of vehicle deploys as it is transmitted back to engine from wheels until we disengage the clutch. Thus an overdrive in an automatic transmission locks in one direction while transmitting power from engine to the wheels and rotates freely on reverse transmission of power from wheel to engine. This conserves the kinetic energy of vehicle for useful movement.