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Mechanical Engineering


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Everything posted by SAJAL KUMAR DAS GUPTA

  1. Least count is the value of one division of vernier scale.Since we take the vernier value with the particular vertical line of vernier scale that exactly concides with the vertical line of main scale while measurement,we have to add this value with main scale value.For example say,n th line of vernier scale matches with a particular division of main scale,the final reading will be value of main scale reading+value of n th line of vernier scale x Least count(i.e value of one div of vernier scale).
  2. Provide turn buckles on both legs of table on each side of extensions.The turn buckles will connect extreme ends of extensions underside and pair of legs on each side through hinge pins.After fully extending the extensions both hinge pins will be inserted into matched holes of extension board/one end of turn buckle and table leg/other end of turn buckle and then turn buckle will be turned to make rigid support.When extension pieces are retracted fully,the turn buckles will be removed by removing pins and stored safely for further use when required.
  3. Different lubricants are used in different type of application.For example,an industrial fan can be fitted with an anti friction bearing,or a bush bearing which might be lubricated with oil or grease depending upon various factors viz load,RPM,temperature,environmental consideration but surely lubricant like graphite powder or air or viscolite can not be used.Similarly for a large multistage submersible water pumps grease can not be used in place of water as lubricant.An aerofoil bearing used for very high speed machines,oil can not be used in place of air.An elevator conveying pulverized material uses conveying material as lubricant for its bottom drum bearing.. In a nut cell,different lubricants are for different uses and can not be used in place of one another against recommendations by machine designers.
  4. The horizontal plate should cool faster since it's top surface is in contact with atmospheric air which is applied vertically to surface of the plate to dissipate heat faster. The answer is only a logical response and not intricate engineering solution.
  5. NDT is closely related to mechanical engineering as the test results are correlated to mechanical engineering on many occasions and decisions are taken accordingly.I will quote only one example in this regard. Radiography of a new large gear reveals that it has got some flaws in in the casting at it"s hub area.Now a mechanical engineer knows the type of load the will be subjected to when erected and commissioned.Now just because of a small flaw in the casting of the gear,he will not reject the item outright.instead,he will examine it thoroughly considering various operating operational parameters and may accept the item .So a mechanical engineer is an integral part of decision making with regards to test report of NDT.
  6. Why do you want to waste power by using a centrifugal pump(Fluid) having more expensive construction and higher power requirement rather than using a less expensive machine requiring much less power centrifugal blower?
  7. You could try a spring return small limit switch to be suitably located at the travel end of the cylinder rod in such a way that during every stroke,the end of piston rod pushes the switch pin gently and the pin comes back to its original position once the rod end starts its retraction. This pulse is to be measured per unit of time to calculate the cycle of operation.
  8. Please explore 1.Weather machine RPM can be changed. 2.Consider resonance factor.Look for possibility of change in natural frequency of machine structure/Foundation.
  9. Photographs along with sketch/drawing of shaft assembly with name of components will be very much appreciated.Thanks for sharing.
  10. You may explore using a PIV gear box(Hydraulic) PIV refers to Positive Infinite Velocity
  11. In the given condition,a multistage centrifugal pump designed for a suction lift of 25 mtrs or more may be explored.I am not aware whether a centrifugal pump is being manufactured having above specification. Alternatively,suitability of a booster pump down the suction line of the existing pump may be explored.. If condition permits,a submersible pump will be a better option,
  12. Preheating for uniform flow of heat through the metal to avoid stress and cracks.Post heating and controlled cooling after completion of welding to relieve stresses.
  13. You may analyze whether intermittent high pressure has got anything to do with level of solvent in the storage tank? assuming your transfer pump is a positive displacement pump delivering solvent at 40 psig,please have a look weather flow of solvent gets restricted during high pressure build up. For proper analysis,few more inputs like flow diagram,pump specification and related operational data is made available from your end.
  14. In most of the products made as per design need some modifications after the product has been practically tried and this can not be termed as failed design Also,a perfectly designed machine may fail during use due to number of other related factor such as operational parameters like pressure,temperature,environment,load,speed.Also,it must be ensured that the personnel operating the machine have got necessary technical skills. In short,before declaring a failed design,thorough analysis must be carried out to pin point the cause of failure.
  15. In a centrifugal pump used for negative head installation,suction head at site must be considered while selecting the pump.
  16. Assembly drawing is required when more than one component is assembled together to make the final assembly to be exactly the same that the designer conceived while designing. Also,BILL OF MATERIAL gives details of number of parts required along with material specifications before actual assembly job is taken up.Normally detailed dimensions like size,,tolerances,surface finish specifications are not given in assembly drawing but overall dimension,weight etc are provided for the assembly and installation personnel to plan them in advance.Also special instructions for assembly job is provided in special cases.
  17. Mainly cylindrical shape is stronger than other shapes and also for minimum stress concentration that may minimize possibility of structural failure.
  18. Knurling is a process where the surface of part of a machined job/machined job is made rough using a knurling tool.This rough surface of the machined component makes the of the person holding it to have better grip while working with it.Sometimes it is just for aesthetics.Sometimes it is also used to have better bonding with the other material that will be coated over the knurled machined component.
  19. The question"What is the advantage of providing bush in a bearing" The bush itself is a bearing that normally we call a bush bearing.Mainly we use bush bearing 1.Where one piece anti friction bearing can not be fitted like engine connecting rod big end bearing,large mill bearings bearings are 2.Bush bearings are cheaper than anti friction bearings. 3.Where bearing is to be accommodated in two pieces. although new anti friction bearings are coming in two pieces.. 4.Used in airfoil bearings in aircraft jet engines and industrial turbo blowers being the most efficient over anti friction bearings.for being maintenance free and highly energy efficient. However many bush bearings are being replaced with anti friction bearings for ease of maintenance and better life. Material of bush is normally a soft material like gunmetal,brass,white metal,Thermit metal,Teflon,cast iron,wood tec but these days we sometime use bearing made out of very hard material like Ni hard bearings.
  20. As Mr Karim has rightly answered,In second and fourth angle projection viewing and projected plane are different than that of first and third angle projection,There is possibility that the one projection may overlap the other one creating confusion to understand the drawing.
  21. There should not be any problem provided proper specification of s.s pipe is used.Stainless steel pipes can be rolled,welded like steel pipe.It is mainly the cost consideration that stainless steel is generally not used for cycle manufacturing.
  22. Normally in petrol engine,a spark is needed to ignite air/fuel mixture after each compression stroke to deliver power stroke.But that does not mean that engine will stop if few sparks are missing.In a multi cylinder petrol engine,the engine will continue to run even if there is no spark in one of the cylinder with a reduced efficiency.In turbojet engine(Used in aircraft),sparking is discontinued sometime depending upon operating parameter after the engine has been started using sparks. Few scooters do not have a battery to produce spark for the petrol engine.
  23. There are many cold welding epoxy available in the market to repair the bearing housing.You need to take certain precaution while carrying out the repair work. Since the plastic bearing housing is out of shape,you must locate the new bearing on shaft with the center line of the stator so that rotor rotates in alignment with the motor stator.Once you have located the new bearing and tried it manually to confirm trueness of the rotor with respect to stator,you can go ahead with epoxy filling.You may use some jel for coating over bearing outer race so that epoxy and bearing outer race do not join permanently with one another.
  24. So far I am able to understand your question,you would like to redirect compressor outlet air back to compressor suction port and if it is so, Air temperature will go on increasing effecting performance of compressor lubrication system,valves and all other components.Also,since air temperature will go on increasing,reducing it's density problem of partial vacuum will occur inside cylinder and the valves will not work properly as they are designed to work on particular pressure. But why do you want to recycle compressed air in the first place?
  25. Please let us have the problems.Hope this to be interesting.
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