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  1. Today
  2. Hi I'm new to this forum. I work in industry and am currently studying part time for my BEng aswell. We're doing a short design project based on powerscrew mechanics, and I was wondering if someone could shed some light on mechanics of horizontal powerscrews? Specifically, I'm having difficulty with the Torque required to move a load along a horizontal power screw. We've already done a vertical powerscrew, and the vertical calculations are all sorted (thanks to Shigley's Mechanical Design). I've used the information in that book to derive equations for Torque required for the horizontal powerscrew, but one comes out negative. I have trialled different FBDs and derivations but one always ends up negative. I've attached an image with a sketch of the scenario, in case I haven't explained it clearly enough. I've also attached my derivations of the horizontal power screw torque equations from FBDs. This document also contains the values I'm using, showing that Torque(right) comes out negative. I've checked everything I know to and am completely stuck! Any ideas?! Thanks in advance!
  3. Performance test of IC engine refers to testing performance parameters of the engine such as power output, fuel consumption, volumetric efficiency, torque, thermal efficiency, specific air consumption etc. to see whether the engine meets the specifications intended by the designer, this is done using an Engine test bed. An engine test bed is a device used to test, develop and characterise an engine.
  4. In a single cylinder in si engines the power stroke starts in which degree rotation of crankshaft

  5. "


    "I think the human race made a big mistake at the beginning of the industrial revolution, we leaped for the mechanical things, people need the use of their hands to feel creative." - Andre Norton"

    Feel free to reject all the products of the industrial revolution in your own life. Do not ride in automobiles, do not use electricity, do not use any machine of any type, and of goodness sakes, do not use a computer. Just go live in a cave or a mud hut, (no lumber, nails, screws, or glue allowed), burn only wood or cow chips, and do not eat anything cultivated or processed by machinery. This would be a good start, and then I'm sure you will find ways to improve on this beginning. Enjoy your life!!!


  6. Yesterday
  7. Shown here is the battery ignition system.there are others like magneto ignition systems and various other ignition methods.the battery is connected to primary winding via ignition switch which when turned on completes the there are breaker points in the circuit that is operated using a cam connected to the engine. This essentially determines the ignition timing.when the breaker points come into contact the current flows into the primary winding inducing a magnetic field in it.Now when the breaker points open the current flows into the capacitor. Now the primary winding induces a current in the wire which flows in same direction of primary current. Hence this helps in charging capacitor to a higher voltage than battery .now current starts flowing from capacitor and not the battery. This reverses the magnetic field in the primary winding.the sudden reversal induces a high voltage in secondary winding which then carries current to distributor.the distributor decides the time at which each spark plug must activate
  8. I feel that electric cars are the next revolution that is going to happen in automotive industry.this is because wide sources of energy is available that can be converted to electricity efficiently.Moreover the rapid improvement in battery technology with promotion of nano cell technology will the pave the path for these vehicles.Emissions will hence decrease when multiple renewable energy sources are used. Second, electric cars make less noise and are going to be more economical in future.they have fewer moving parts thus avoiding wastage of energy and leading to high efficiency. The electric cars don't require any power train units like gearbox thus enabling a single pedal drive.This will make the driving of a car simple.Just imagine a car with just one pedal and no gears to is phenomenal
  9. i am studying in Mechanical 4th semester. i wanna get into designing field, thought of learning courses such as CATIA, AUTO-CAD 2017 and AUTO-DESK INVENTOR. Is it preferred courses and can i get into these courses?? What is the topics which I have to Focus on??
  10. Last week
  11. 1.Refrigeration removes the heat from the enclosed space where as AC cools the air and the circulates in the enclosed space 2.Refrigeration does not cater to latent heat load i.e it does not have any control over humidity whereas AC caters both latent as well as sensible load so it has temperature as well as humidity control 3.Refrigeration has no control over air quality whereas AC has filters to improve air quality 4.Refrigeration does not involve circulation of air as it only works on heat absorption for phase change of refrigerant in vapour cycle where as AC cools the air in air handling unit (AHU) and then circulates it through the space . 5.Refrigerants used in AC are not Fluro Carbons are these have a higher Global warming and Ozone depletion potential i.e these are harmful to humans in case of leakage 6.Refrigeration does not cater to Human comfort i.e it is mostly used for storage and you wont find comfort in refrigerated space because of extremely low temp and humidity change . On other hand AC keeps a control of both humidity and temperature as per the comfort graph made by organisation which fix standard in this case .
  12. Refrigeration is a part of Air Conditioning. Air Conditioning can be divided into Refrigeration, Heating, Addition/Removal of Moisture, Air Purity Control and Air Distribution Control.The basic difference is that the Air Conditioner controls the humidity along with temperature while a Refrigerator controls the temperature.
  13. diesel engine uses fuel injector rather than spark plug.the fuel is burn automatically itself due to high temparature of air and compression of require low ignition temparature to burn yhe fuel.
  14. There's no need of spark plug in diesel engine it cmpress intake air to high degree temperature in the combustion during compression stroke whereas diesel fuel is spray by injector nozzle during the power stroke in to compressed air and ignited whereby pushing the engine downward, that's why we called diesel engines as self ignition engine.
  15. I can't make a CAD model for you but can help you in any particular problem. So please update your problem with more information. I will surely help you.
  16. "I think the human race made a big mistake at the beginning of the industrial revolution, we leaped for the mechanical things, people need the use of their hands to feel creative." - Andre Norton

  17. There are so many differences in a refrigerator and an air conditioner. Broadly speaking, the major is in there operation a refrigerator only make things cooler while an air conditioner makes air good for us that includes controlling humidity removing dust and also controlling temperature. For more info you can go through this page
  18. The fact that it offers a high gear ratio is certainly an advantage, but that can also be achieved by other mechanisms. The major reason is that, under most circumstances, the worm drive can not be back driven. This is a major safety consideration for a hoist. DrD
  19. Go through this link
  20. please my group and I are working on a project that involves a foldable tent this is no ordinary tent but its kind of used frequently here in Ghana for funerals and our task is to make a foldable and portable tent that can resist all kinds of weather conditions image of the tent is attached for clarification
  21. Basic Dynamic Load Rating. The basic dynamic load rating (Cr) of a bearing with rotating inner ring and stationary outer ring is that load of constant direction and magnitude which a sufficiently large sample group of apparently identical bearings can endure for a basic rating life of one million revolutions.
  23. Darcy–Weisbach equation gives the value of head difference or in case of flow, loss of head in the turbulent flow through pipes due to frictional factors, this equation gives this in terms of all the measurable quantities and is derived from the equation of velocity profile. Head loss hf = ((P1 - P2)/(density x g)). Hence is of much importance in experimental works, dimensional analysis and model analysis of flows.
  24. Quality control refers to maintain quality during production on plant, such as if during production part does not meet the quality standards it will be rejected and further no production will be produced against rejected part but during Quality Assurance we check/inspect the quality requirements of old parts, plants and make sure that it is acceptable or not. For example, 2 or 3 years used part , after 3 years we assure its quality that its still fulfill the quality standard requirements.
  25. difference between square thread and v-thread in terms of strength


  26. hello guys.. I need your help about lathe cutting tools(tool-bit).how do we shape cutting tools? is there a specific degrees to use? to measure? I really need your help guys .

    cutting tools to make:

    -Right cut corner

    -Left cut side

    -square nose

    -right cut side

    -brass cutting

    -left cut

    -Round nose

    -right cut

    -left cut corner

    -thread cutting

  27. The rotation will be in a horizontal plane, and the axis is vertical. Am I right if I say that we want drag force instead of lift force? We want most dragforce in the 1. and 4. quadrant (as shown in the picture), seeing that the turbine rotates counter clockwise. The blades will be connected with bearings to ensure rotation for the blades are possible, so that in 1. and 4. quadrant the blades will be standing vertical to ensure a big surface area, and rotate in the 2. and 3. quadrant so that the dragforces are as small as possible in those quadrants. The power will be generated from a generator above water.
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