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  1. 46 likes
    Basically a Pump is used for liquid or fluid to transform it to a much high pressure head while a Compressor is used for gases to transform from low to a much high pressure. From Mechanical Engineering point of view liquid is incompressible so Compressor cannot be used for liquid substances. Posted by AbdulQadir Abba Sheriff on linkedin
  2. 13 likes
    Pumps can handle both liquids and gases. But Compressor can handle only the gases due the incompressible nature of liquids.................
  3. 13 likes
    In DTSi, instead of 1 we are using 2 spark plugs. Flame front formed is able to consume more air-fuel mixture as compared with 1 spark plug, thus more complete burning and more efficiency. in DTS-Si, with addition of 2nd spark plug, what they are doing is relocating valves position. With proper designing of inlet and outlet valves you can induce extra swirl for inoming air fuel mixture. Due to turbulence, extra efforts are provided for proper mixing of air and fuel. (We can not allow petrol to go in liquid droplet form, it should be finely atomized). With well atomized air fuel mixture, efficiency increases.
  4. 12 likes
    In second angle, both top and front view are drawn above the x-line whereas in fourth angle its vice versa. In second and fourth angle method, top view and front view overlaps. hence we never use those methods. In first angle method, front view lies above the x-line and top view lies below. vice versa for third angle. As both the views lies on either side of x-line in first & third angle, we make use of these methods.
  5. 10 likes
    To draw a projection of any object first we need to place this object in any quardrant then fit a source of light in front, above or any angle you want. A shadow will occur in the opposite side of the light source which will represent the projection of that object. Now after drawing this projection, the horizontal plane is to be rotated 90 degree clockwise. in second and fourth angle projection due to this process horizontal and vertical plane will overlap with each other. That's why we can't draw second and fourth angle projection.
  6. 9 likes
    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
  7. 8 likes
    Dear Sourabh, very good question. Just because of the norms we do this. We consider that horizontal plane rotates in clockwise direction after having projection on it. that's why we use 1st angle and 3rd angle projection. because only in this two quadrants we will get the both views after clockwise rotation of horizontal plane. Yes we can use second angle and fourth angle projection but in that case we need to rotate horizontal plane of projection in counterclockwise direction. Thus both 1st angle and 3rd angle projection will be replaced by 2nd angle and 4th angle projection.
  8. 7 likes
    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
  9. 7 likes
    Example for Calculation of Least Count of Vernier Calipers: A vernier scale has the length of 9 main scale divisions and is divided in to 10 divisions. Calculate the Least Count of the Vernier Calipers. Solution: Since 9 divisions of the vernier scale coincide with 10 divisions of the main scale VSD = 9 / 10 mm = 0.9 mm MSD= 1 mm Least Count= 1 MSD- 1VSD = 1mm - 0.9mm = 0.1mm
  10. 6 likes
    The performance test of an IC engine is done to find out the power of the engine at various loading conditions and the fuel consumptions at various loads. The main parameters which are tested are 1.Indicated power 2.Brake power 3.frictional power 4.specific fuel consumption(sfc) when subjected to different loads. Further,tests can also be conducted to compute the surface temperature of the engine,oil/water needed to cool the engine.
  11. 6 likes
    Well, a compressor compresses a gas and a pump moves a liquid. Compressors are often used in refrigeration applications where gas is transformed into a liquid, so the main task for the compressor is not to move the gas but to compress it to increase its pressure. But role of pump is for displacement of fluid (mainly liquid) by applying pressure.
  12. 5 likes
    Following are the reasonable points that conclude the high torque and efficiency of diesel engine. Diesel engine uses simple mechanism for combustion unlike in gasoline engine. Removal of ignition system not only makes the mechanism simpler but also reduces the risk of improper combustion due to damage in ignition system. In short burning of the fuel is easy and always accessible. This results in higher efficiency diesel engine. Diesel fuel is a heavier hydrocarbon in which carbon and hydrogen are strongly bonded with each other. And when energy is supplied in form of heat it gets explode releasing much higher energy then gasoline. In short diesel fuel has higher energy density then gasoline which results in huge explosion. One more factor for higher efficiency in diesel engine is its property of lubrication. Although all fuel has property of lubrication but diesel fuel has much higher lubrication then gasoline fuel. The compression ratio is much higher in diesel as compared to gasoline because in diesel engine air is alone compressed inside the cylinder and it’s a known fact that gas easily compresses then liquid. This is not so in gasoline engine because air-fuel mixture is compressed inside the cylinder. This higher compression gives higher heat and simultaneously higher torque. We can’t use Carnot cycle to get 100% efficiency but can use its principle to attain maximize efficiency. In diesel engine heat is added at constant pressure which results in higher utilization of heat energy to get maximize work output. These were the advantageous features of diesel engine but it has some demerits as well like it releases highly toxic gases, noisy, higher maintenance cost and starting problem (now starting problem is eliminated by using a bulb nearby to the cylinder) to heat the engine before ignition. And it is costlierthan gasoline engine but with optimum operation and good maintenance resolve all these problems.
  13. 5 likes
    Hardness: Hardness is the resistance of a material to localized deformation. The term can apply to deformation from indentation, scratching, cutting or bending. hardness commonly refers to a material's ability to penetrate softer materials. An object made of a hard material will scratch an object made of a softer material.In metals, ceramics and most polymers, the deformation considered is plastic deformation of the surface. For elastomers and some polymers, hardness is defined at the resistance to elastic deformation of the surface. The lack of a fundamental definition indicates that hardness is not be a basic property of a material, but rather a composite one with contributions from the yield strength, work hardening, true tensile strength, modulus, and others factors. Hardness measurements are widely used for the quality control of materials because they are quick and considered to be nondestructive tests when the marks or indentations produced by the test are in low stress areas. Toughness: The quality known as toughness describes the way a material reacts under sudden impacts. toughness is the resistance to fracture of a material when stressed. It is defined as the amount of energy that a material can absorb before rupturing, and can be found by finding the area (i.e., by taking the integral) underneath the stress-strain curve. It can be defined as the work required to deform one cubic inch of metal until it fractures. Toughness, often expressed as the Modulus of Toughness, is measured in units of joules per cubic meter (J/m3) in the SI system and pound-force per square inch (sometimes expressed as in-lb/in3) in US customary units. Toughness is measured by the Charpy test or the Izod test. Both of these tests use a notched sample. The location and shape of the notch are standard. The points of support of the sample, as well as the impact of the hammer, must bear a constant relationship to the location of the notch. Difference: The hardness of a metal limits the ease with which it can be machined, since toughness decreases as hardness increases Toughness is a combination of high strength and medium ductility. It is the ability of a material or metal to resist fracture, plus the ability to resist failure after the damage has begun. A tough metal, such as cold chisel, is one that can withstand considerable stress, slowly or suddenly applied, and which will deform before failure. Toughness is the ability of a material to resist the start of permanent distortion plus the ability to resist shock or absorb energy
  14. 5 likes
    Casting is a process in which the metal is melted at high temperatures and then poured into a mould to give it the desired shape. There are many casting methods: Sand Casting, DIe Casting, Lost Wax casting. In casting process the newly formed shape sometimes needs extra machining to get the desired surface finish. The cast parts can also incorporate defects because of air bubbles and internal stresses. Casting have some issues with metal selection. All the metals are not suitable for casting. It is sometimes associated with blow, scar, scab etc. errors. Forging is also very old method. Blacksmiths used to do forging with the hammer and anvil from an ancient time. It is the process where metal is heated in different temperature ranges and then hammered to get the desired shape. Depending on the temperature forging can hot, cold or warm. While forging there is a change in the grain structure of the metal which consequently makes it more tough and wear resistant. There are very less porosity and shrinkage defects.
  15. 5 likes
    Washers are used when bolting to make stronger the joint and to reduce bolt fatigue due to inconsistent loads. Any stretch or flattening of parts is likely to be less than the compression of the washer thus, the bolt won't loosen much.
  16. 5 likes
    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
  17. 5 likes
    Because tractor is designed for farm which is very rough, uneven and highly zigzag surface. because of this surface there may be chances of damage of exhaust system if it designed as a car. So, it designed for up front with turbocharger engine.
  18. 4 likes
    There are 3 reasons for this point. "Why Tractors have vertical exhaust in the front" 1. Design level reason : Tractor is made of 2 piece construction. The rear portion (with the rear axle and drive line) can be seperated from the front portion (with engine, transmission). Hence, the silencer and exhaust tail pipe has to be kept along with the front part of the tractor. If the exhaust was to be facing the ground, then the hot gas will blow on the Driver's legs and will cause uncomfort for the user. Hence, the exhaust gas is sent vertically upward. 2. Functional level reason : If Silencer has to be placed facing the rear, (as in car), then the silencer has to be kept at the bottom. If the exhaust tail pipe is kept at a lower level, the fast blowing exhaust gas will lift up the loose sand in the crop field, now, this has multiple negative impacts 2.1. Top layer of any crop field is the fertile sand, which will get blown-off if tractor silencer is fitted like in cars. If this is allowed, every time, tractor is used, the crop field will loose its fertile sand and ultimately will become barren land. 2.2. Another effect, is these blown-off loose sand, will fall and settle on the crops, forming a layer which will cover the crop and thus stopping the Photosynthesis process of the crops. So the crop yield will be badly affected 3. Yes, keeping the silencer and tail pipe at the bottom will have other packaging issue, where, due to the articulation in crop fields, there is every chance of the silencer getting damaged due to ground hits. By the way , I m in Automobile Service Industry for the last 12 years.
  19. 4 likes
    Flexible coupling are mostly used to protect the pipelines connected to any machines carrying fluids . It may be used for a pump or some engines carrying coolants through it. Another use of flexible coupling is to transmit power from an engine . If the coupling was rigid , it could transmit the vibration from the power producing engine. Mostly in four stroke marine propulsion engine flexible couplings are used to connect the flywheel and the intermediate shaft for rotating the propeller and prevents misalignment of the shaft. Mostly it is made of rubber.
  20. 4 likes
    Forging, of course, wherever is possible. Tensile strength is withstanding the maximum stress before failure. It depends on structure of material. The finer it is, the stronger it will be. Forging is mostly a hot process. So, the crystals tends to come as closer as possible with each other. This improves tensile strength. If there occurs a crack, the material already failed. So, we are taking the best case possible. Casting is a relatively easy n cheap process. But the crystals don't form a finer structure. Cooling temperature varies for different sections. So, they are unable to form a fine structure. An e.g. Pistons of larger size (>150mm dia.) are preferred to be made by forging. As they have to withstand larger stresses. So, as far as I'm concerned, forging is preferred over casting for better tensile strength. But, making and maintaining dies makes it more complicated. So, casting is easier in manufacturing.
  21. 4 likes
    CRDI means Common Rail Direct Injection.. In crdi contains a small tube is called Common rail where the injectors are connected and contains fuel at a constant high pressure of 1,350 bars. The CRDI engine small amount of fuel into the engine before the actual charge and another one afterwords. the high pressure in common rail ensures that when it injected the fuel atomizes to a very high degree and mixes evenly with the air, thereby it making very clean exhaust gas. The engine pr. , timing of fuel injected is controlled ECU. The injectors have very precise dose of diesel into each cylinder .and ECU makes sure the fuel injected at optimum moment. "This ensures lower emissions, and allows better fuel economy.
  22. 4 likes
    The bush material would be of a softer material than the shaft/spindle that runs inside it, often bronze, even oil impregnated bronze. The reasons for using the bush are that the bush will wear out before the bearing or the shaft/spindle, therefore reducing the time and costs of replacing the bearing or shaft. It would usually be sensible to carry spare bronze bearings already made to size to allow for a fast replacement. Usually these bronze bearings would be turned up from a length of bronze bearing material, ask your bearing supplies company for it, and make a few up in one go on the lathe, then label them and put them somewhere you will find them again!
  23. 4 likes
    A forming process that adds a pattern on the exterior of a workpiece, either for cosmetic reasons or better handling. Knurling is a manufacturing process, typically conducted on a lathe, whereby a diamond-shaped pattern is cut or rolled into metal.
  24. 4 likes
    A "fail safe" is a component that will fail when the design load or force has been exceeded. A "safe fail" is when a system will fail to a safe state Eg: A circuit breaker, a fuse or fuel shut-off.
  25. 4 likes
    The Difference Between Casting & Forging Casting is the process where metal is heated until molten. While in the molten or liquid state it is poured into a mold or vessel to create a desired shape. Forging is the application of thermal and mechanical energy to steel billets or ingots to cause the material to change shape while in a solid state.
  26. 3 likes
    In general, pinion is used as a driving gear in a machine. They are used to transferring more torque to the gear. And we already know torque is directly proportional to power transmitted. More the torque and more power can be transmitted. Apart from cyclic loading at higher speed, the pinion also faces a large amount of shear stress since torque is directly proportional to shear stress and due to its lesser polar moment of inertia, the value of shear stress increases proportionally. Show in order to avoid it from shear failure we have to use better material. If we increase the polar moment of inertia, it means its size will be increases which is not desirable for power transmitting. So pinions are made of Superior material than gear.
  27. 3 likes
    A steel forging will display a higher tensile strength than an iron casting per unit cross-sectional area. The process of forging aligns the grain microstructure in a longitudinal direction and gives the forging directional strength. Castings, on the other hand have no directional strength due to the solidification process of the molten metal. In addition, sand castings particularly are prone to porosity and exhibit little or no elastic and plastic deformation. While cast iron does have great wear resistance, it has low ductility and is also very brittle.
  28. 3 likes
    CC means Cubic Centimeter, It basically denotes the Volume of Cylinder, whether it may be a car or Bike.Technically it's the Bore Diameter and the stroke length of the cylinder.If a car as 1.8L Engine it's nothing but 1800 cc..Hence More the cc, more the power nd torque.
  29. 3 likes
    basically F.O.F is the short term for "Face of flange" of the pipe.It is used for determining the elevation and position of the pipe in isometric view.
  30. 2 likes
    Square threads: The sides of the flanks of square threads are normal to the axis and hence parallel to each other. The pitch of the threads is often taken as twice that of B.S.W. threads of the same diameter. These are used for power transmission. V threads: British Standard Whitworth (B.S.W.) thread: It is a symmetrical ‘V’–thread in which the angle between flanks is 55°. These threads are generally used on bolts, nuts and studs et
  31. 2 likes
    We don't use a spark plug in a diesel engine because after compression stroke in diesel engine the temperature of air inside engine cylinder rises to 600°C and pressure rises to 35 bar. When the diesel is sprayed in the engine cylinder in form of the mist due to high temperature in the cylinder the diesel which is sprayed as mist catches fire due to the high temperature. So we don't need a spark plug in diesel engines. Thank you.
  32. 2 likes
    My understanding is that an anti friction bearing is a roller bearing, it has a point or line contact and a journal bearing supports supports a shaft and has surface contact. I also think speed has something to do with it, roller bearings are lower speed while journal bearing are high speed
  33. 2 likes
    Washer can increase shear area where the bolt holds, and it eliminate friction and scrathing of both contacting surfaces of bolt head/nut and the surface being bolted
  34. 2 likes
    To protect the bolt hole, spread the load & forces evenly, as a spacer, protect the nut from crevice & galvanic corrosion.
  35. 2 likes
    Washers are used with mechanism for this, that forces on surface area spread evenly.
  36. 2 likes
    S.K.Das Gupta-I think the question itself needs to be modified as "What is the advantage of providing a bush in a bearing housing in place of bush in a bearing. In fact ,the selection of bush bearing or anti friction bearing in a machine depends on the requirement.For example.in a crank shaft of an engine,the big end bearing can be fitted in two halves only.Hence a bush bearing in two halves is used.There is also a space consideration for the machine as anti friction bearing normally needs more space.Also,for very high speed machines,foil bearings are being used as these are very efficient and having a very long life.These days many bush bearings are being replaced with anti friction bearings to get better life and ease of maintenance.So in a nut cell,using a bush bearing/anti friction bearing depends on the function of the machines,it's operating condition,lubricant requirement,space for bearing mounting and many other factors. Material of bush may be phosphor bronze,gunmetal,cast iron,thermit or white metal,teflon etc.
  37. 2 likes
    To reduce the stress concentration at the sharp edges of the others shape like rec. sqr. trin. or any other shape. the Best shape is to use spherical shape but it seems not possible . In refineries the big spherical containers are used for storage , but for distribution purpose the cylindrical shape is the most suitable shape. Regards, Aftab
  38. 2 likes
    A jig's primary purpose is to provide repeatability,accuracy and interchangeability in the manufacturing of products. A device that does both functions (holding the work and guiding a tool) is called a jig. An example of a jig is when a key is duplicated, the original is used as a jig so the new key can have the same path as the old one. Fixture is a work holding device that holds, supports and locates the workpiece for a specific operation but does not guide the cutting tool. It provides only a reference surface or a device
  39. 2 likes
    Performance parameters of IC Engines 1. Power and Mechanical Efficiency 2. Fuel Air-Ratio 3. Volumetric Efficiency 4. Specific Output 5. Specific Fuel Consumption 6. Thermal Efficiency and Heat Balance 7. Exhaust Smoke and Emissions 8. Effective Pressure and Torque
  40. 2 likes
    Depending on the apparatus Torque & RPM may be the measured items and used to determine power. Horsepower vs Torque 850 HP vs 18HP w/ maximum tork @ 0RPM
  41. 2 likes
    To allow slip and creep chain drive is used over belt or rope drive. To get accurate rotational timing a chain drive is best replacement for belt drive. Pro's of chain drive over belt drive 1) It can be used for accurate rotational timing thus used in I.C. Engines as timing chain. 2) There is no loss of energy in the form of heat because no slip and creep occurs. 3) Better service than belt drive. Con's of chain drive over belt or rope drive 1) Initial cost is more than belt drive system 2) Require proper lubrication for smooth functioning. 3) Not silent as belt drive in absence of lubrication. 4) Catches rust easily.
  42. 2 likes
    Initially, cost!....no need for expensive or complicated ducting of the exhaust gasses. Minimisation of fire risk (as said above) Due to the "enhanced ventilation" available in the early tractors (ie there was no enclosed "cab") there was no need to prevent a build-up of exhaust gasses around the cab. Diffusion of highly flammable dusts (such as during harvest) reaches a lower ignition/explosion risk at slightly higher levels. Prevention of both grounding and blockage due to the environment. No exhaust blowing onto the pickers/packages following the tractor. Probably a few more to boot!
  43. 2 likes
  44. 1 like
    I recall in my early years wondering about 1st and third angle projection. What happen to number two? To practice 3D CAD programs I use a 1947 drafting text book, first published in 1911. I found the best explanation of angle projections I have even come across. "First angle was the norm until 60 years ago. Now 3rd angle is the norm in the US and Canada." I am not sure if the 60 refers to the original 1911 printing or the 7th Ed (1947) that I have. Either way it was been around before all of us even the good DrD. I took a photo of the page. The section continues onto the next page but only adds that expensive mistakes have been made confusing the two systems. Now we make those expensive mistake confusing metric and imperial units.
  45. 1 like
    Some of the qualities that should be present in materials for shafts are as follows: 1. The material should have a high index of strength. 2. Also it should have a high level of machinability. 3. The material should possess a low notch sensitivity factor. 4. The material must also have wear resistant properties. 5. Good heat treatment properties should also be present. The common material used to creates shafts of high strengths an alloy of steel like nickel is used. The shafts are manufactured by hot rolling processes and then the shaft is finished using drawing or grinding processes.
  46. 1 like
    Horizontal one .... because more area for heat transfer....
  47. 1 like
    it help to lessen the counter forces produce by vibration, to aligned all forces toward center and perpendicular to flat surface thus give optimum fastening strenght e.g. bolt and nuts with washer.
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  50. 1 like
    Its a process used to improve or alter mechanical properties and sometimes chemical properties of metals. Metals are heated up to a specific temperature and then cooled down by different cooling rates depending on the requirement. Annealing, Normalizing, Hardening, Quenching, Tempering are some common heat treatment process.