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Q 1. Engines. Parts of an engine. 2 stroke engine Fuel:Petrol /alcohol/LPG/other gases Used in: L awnmower, chainsaws, strimmers. 4 stroke engine Fuel: Petrol/Diesel Used: I n cars, trucks etc. 4 stroke of an Engine . Induction stroke.

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  1. Q 1 Engines

  2. Parts of an engine 2 stroke engine Fuel:Petrol/alcohol/LPG/other gases Used in: Lawnmower, chainsaws, strimmers 4 stroke engine Fuel: Petrol/Diesel Used: In cars, trucks etc.

  3. 4 stroke of an Engine Induction stroke The inlet valve is open and the exhaust valve is closed. The piston is moving down the cylinder creating a partial vacuum. This causes the fuel mixtures, which is air and petrol, to flow into the cylinder Compression stroke The inlet and exhaust valves are closed. The piston is rising, compressing the mixture into the combustion chamber Power stroke The fuel mixture is ignited by a spark from the spark plug. The resulting combustion causes a huge increase in temperature and pressure. This forces the piston downwards. Both valves remain closed Exhaust stroke. The exhaust valve is open and the inlet valve is closed. The piston is rising, driving the burnt gases out through the exhaust valve.

  4. 2 stroke engine: Used for motor cycles and for small outboard engines for boats. As the piston moves upwards, the transfer and exhaust ports are covered and the inlet ports uncovered. The partial vacuum created below the piston cause the fuel mixture of air and petrol to flow into the crankcase. At the same time, the charge from the previous stroke is being compressed above the piston. At the end of the upward stroke the compressed fuel mixture is ignited by the spark plug. The rise in pressure caused by the combustion forces the piston down the cylinder. As it travels downwards, it compresses the mixture in the crankcase and uncovers the transfer and exhaust ports. This enables the compressed mixture to transfer to the top of the cylinder and the burnt gases to escape.

  5. Q 1 Electronics

  6. Q 1 Inventors

  7. Q 1 Terms

  8. Q 3 Lathe

  9. Parts of the lathe. Pic 2. Angles in the lathe. Pic 3. Tool heights Centre height is correct because: It ensures the work is cut to the center It maintains the correct rake and clearance angles It ensures good quality finish. Rake Angle – this angle facilitates the removal of the chip. Clearance Angle – this ensures that only the cutting edge of the tool comes into contact with the work.

  10. Drilling Produces a flat surface by using the cross slide to move the tool at right angles to the axis of rotation of the work. Using the tailstock to remove a hole from the centre of the piece. Taper turning The top slide is used for cutting the short taper. It is set to half the included angle of the taper and cuts are then made. Impressing serrations on articles to enable them to be gripped securely by hand. Parallel turning Parting off The tool moves parallel to the axis of the rotation of the work and cylindricalforms are produced. Removes the piece by using the cross slide to move the tool at right angles to the axis of rotation of the work.

  11. Q 3 Drill

  12. Cutting Speed Cutting speeds for tools are given in meters per minute. To calculate the spindle speeds the following formula can be used: N= S x 1000  x D Answer is given as rev/min. Where: N = Spindle speed in rev/min. S = Cutting speed in metres/min. D = Diameter of drill in millimetres/min. Calculate the drilling machine spindle speed in rev/min to drill a 6mm diameter hole in a material whose recommended cutting speed is 30m/mm.(take  = 3.) N= S x 1000  x D (rev/min) S = 30mm/m D = 6mm • = 3 N= (30) x 1000 = 30000 (3) x (6) 18 = 1666.66 = 1,667 rev/min to nearest revolution

  13. Q 4 Furnaces

  14. Type of furnaces Basic oxygen furnace Eclectic Arc Furnace Blast furnace

  15. Heat treatments Why do we use heat treatments? • Materials are heat treated to improve their mechanical properties. • Materials are heat treated to allow them to be worked, rolled or drawn. Heat treatment processes include – • Hardening - a piece of high carbon steel is heated to a cherry red. It is then quenched rapidly in water or oil to make the steel hard. The hard steel will also be brittle. Used in Cold chisels, drill bits, screw cutting taps and hacksaw blades. • Tempering – Used to toughen previously hardened steel. Heated uniformly below lower critical temperature. Cooled in air. • Annealing - Used to remove coarse grain structures in castings or forging. Heated above upper critical temperature. Cooled in air. • Normalising– Relieves stress and increased ductility. Heated above upper critical temperature. Cooled in furnace.

  16. Q 7 CNC MACHINES.

  17. CNC Lathe Control the movement of the tool Provides light for working Protects the user from flying objects Controls the movement of the tool Stops the machine in case of an emergency Holds the work in place Holds the tool in place Moves the tool perpendicular to the chuck Removes unwanted material

  18. Depth Gauge Micrometre Vernier calliper 2.75 19.55

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