Basic Mechanical Engineering -Mechanical Elements
- 1. Unit 1 Introduction to Mechanical Engg. Prof. S.R.Thorat Mechanical Engg. Department Sanjivani Collge of Engineering, Kopargaon 1 1. Mechanical Elements S.R. Thorat/BME/Unit-1/Mechanical Elements
- 4. 2.Axle • It is used to support rotating element pulleys, brakes. • It does not transmits torque but subjected to bending moment only. 4S.R. Thorat/BME/Unit-1/Mechanical Elements
- 5. 3.Key • A key is a mechanical element inserted between the shaft and hub or boss of the pulley to connect these together in order to prevent relative motion between them. • It is always inserted parallel to the axis of the shaft. • Keys are used as temporary fastenings and are subjected to considerable crushing and shearing stresses • material – Plain carbon steel • Material used for key is lesser strength than shaft material. 5S.R. Thorat/BME/Unit-1/Mechanical Elements
- 6. Classification- 1.Sunk keys 5. Kennedy Key 2. Saddle key 6. Tangent key 3. Round keys 4.Splines. 1.Sunk Key- The sunk keys are provided half in the keyway of the shaft and half in the keyway of the hub • Types of Sunk key 1 Rectangular sunk key 2. Square sunk key 3. Parallel sunk key 4. Gib-head key 6S.R. Thorat/BME/Unit-1/Mechanical Elements
- 7. 1 Rectangular sunk key 2. Square sunk key 3.Gib-head key 7S.R. Thorat/BME/Unit-1/Mechanical Elements
- 8. 2.Saddle keys • The saddle keys completely fits in key way provided in hub of rotating element. • Types- 1. Flat saddle key 2. Hollow saddle key 8 S.R. Thorat/BME/Unit-1/Mechanical Elements
- 10. 4.Coupling Coupling is used to connect two shafts or to couple driving shaft with driven shaft. Functions- 1. To provide the connection of shafts of different units such as a motor and generator and to provide disconnection for repairs or alternations. 2.To reduce the transmission of shock loads from one shaft to another. 3.To introduce protection against overloads. 10S.R. Thorat/BME/Unit-1/Mechanical Elements
- 11. Requirements of a Good Coupling- 1.It should be easy to connect or disconnect. 2. It should transmit the full power from one shaft to the other shaft without losses. 3.It should hold the shafts in perfect alignment. 11S.R. Thorat/BME/Unit-1/Mechanical Elements
- 12. 1.Rigid coupling 2. Flexible coupling 1.Flange coupling 2.Sleeve or muff coupling. 1.Universal coupling or Hooks Joint 2. Oldham coupling 12S.R. Thorat/BME/Unit-1/Mechanical Elements
- 13. 1.Flange coupling 13 Applications- Connection of electric motor to pump or compressor S.R. Thorat/BME/Unit-1/Mechanical Elements
- 14. 2.Sleeve or muff coupling 14S.R. Thorat/BME/Unit-1/Mechanical Elements
- 15. 1.Oldham coupling 2.Universal coupling or Hooks Joint 15S.R. Thorat/BME/Unit-1/Mechanical Elements
- 16. 5.Bearing • It is machine element supports moving element . • Function- 1.To provide support to the shaft 2. To permit free rotation of shaft with minimum friction. Classification – 1.Sliding contact Bearing i. Journal Bearing ii. Thrust Bearing 2. Rolling Contact Bearing i.Ball Bearing ii.Roller Bearing 16 S.R. Thorat/BME/Unit-1/Mechanical Elements
- 17. 1.Sliding Contact Bearing i. Journal Bearing ii. Thrust Bearing- 17S.R. Thorat/BME/Unit-1/Mechanical Elements
- 18. 2. Rolling Contact Bearing i. Ball Bearing- ii. Roller Bearing- 18S.R. Thorat/BME/Unit-1/Mechanical Elements
- 19. Ball Bearing 19 S.R. Thorat/BME/Unit-1/Mechanical Elements
- 20. 6. clutch • Clutch is mechanism used to transmit rotary motion from driving shaft to driven shaft as when required without stopping the driver shaft. • Function- i. When engaged transmit max power from engine shaft to gearbox i/p shaft . ii. When disengaged , allow driver to shift the transmission in various gear positions. iii. When disengaged, engine shaft should freely rotate without transmitting drive to wheels. 20 S.R. Thorat/BME/Unit-1/Mechanical Elements
- 21. Single Plate clutch 21S.R. Thorat/BME/Unit-1/Mechanical Elements
- 22. 7.Brakes • Brake is device with help of which artificial frictional resistance is applied to moving machine member in order to stop or retard the motion of a machine. • While performing this operation , brakes absorb kinetic energy of moving member . • Energy absorbed by brake is dissipated in the form of heat in surrounding air, so that excessive heating of brake lining does not takes place. 22S.R. Thorat/BME/Unit-1/Mechanical Elements
- 23. Disc Brake 23 S.R. Thorat/BME/Unit-1/Mechanical Elements
- 24. Unit 1 Introduction to Mechanical Engg. Prof. S.R.Thorat Mechanical Engg. Department Sanjivani Collge of Engineering, Kopargaon 1 2. Power Transmission Devices (Belt and Chain Drive) S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 25. Power Transmission Devices • Drives- It is mechanism used to transmit power and speed from prime mover to machine. • Flexible drive-Belt , rope, chain • Rigid Drive-Gears, cams, Clutch, coupling, 2 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 26. 1. Belt Drive • Used to transmit power from one shaft to another by means of pulleys which rotates at the same speed or different. • Power is transmitted by virtue of friction between belt and pulley surface • Power Transmitted depends on 1. Velocity of belt 2. Tension under which belt is placed on pulleys. 3. The arc of contact between the belt and smaller pulley. . . n D D t s p N d d t + = = = + 3 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 27. Flat Belt V Belt V Belt: The belt is having trapezoidal c/s. Used to transmit large amount of power when two pulleys are close to each other. Wedging action. Compact in construction. Multiple V drives - very large power. High speed reduction. Upto 7. Negligible Sleep, quiet in operation. Limitations:Low efficiency 80-96%, costlier. Applications: Blowers, compressors, drilling m/c, IC Engines Flat Belt: The belt is having rectangular c/s. • Used to transmit Moderate amount of power. • Puller distance is not more than 8m apart. • Pulley are provided with crowning to avoid coming off of the belt. • Relatively cheap and easy to maintain. • Efficiency about 98% • Limitations: Slip, Occupy more space, Not suitable for transmitting very high power, cannot used for short distances. • App: Industrial Applications – Floor mills, Stone crushers, pumps. 4 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 28. • Circular Belt or Rope Drive: • Circular in c/s. • Transmits large amount of power , Pulley dist 5m. • Pulleys are provided with grooves. Timing Belts: It is a toothed belt transmits power by means of teeth. Hence no slip. It uses toothed wheels or sprocket. Transmits power at constant speed ratio, Light weight, High efficiency 97-99%, Quieter in operation. Limitations: costlier, cannot transmit large power. Applications: To drive cam shaft from crank shaft, to position drives in machine tools, steeper motor drives. 5 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 29. Types of belt drives Open Belt Drive: Shafts are parallel and rotate in same direction. Lower side – Tight side and upper side – slack side. 6 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 30. • Cross Belt Drive: • Shafts are parallel and rotates in opposite direction. • Gives more angle of contact hence more frictional grip. • However at a point where belt crosses, it rubs against each other and causes wear and tear of belt thus reducing life. 7 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 31. • Compound Belt Drive: • Used when power is transmitted from one shaft to another through number of intermediate pulleys. • High reduction ratio. 8 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 32. Open Belt with Idler Pulley: It is used when shaft are parallel. Used when open belt cannot used due to small angle of contact on smaller pulley. It is used to obtain high velocity ratio. Tension can be adjusted by changing the position of the idler pulley. 9 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 33. • Multiple Belt Drive: • Used when power is transmitted from one shaft to the number of parallel shafts. 10 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 34. • Chain Drive: Consists of an endless chain wrapped around two sprockets wheels. • It consists of number of links connected with pin joint, while sprockets are toothed wheels. • Intermediate between gear and belt drives. 2. Chain Drive 11 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 35. Types of chain Drive 1.Hoisting Chain (Cranes) 2. Conveyer Chain 3.Power Transmitting Chain 12 S.R. Thorat/BME/Unit-1/Belt and Chain Drive
- 36. Unit 1 Introduction to Mechanical Engg. Prof. S.R.Thorat Mechanical Engg. Department Sanjivani Collge of Engineering, Kopargaon 1 2. Power Transmission Devices (Gears) S.R. Thorat/BME/Unit-1/Gears
- 37. GEAR • Gear is toothed wheel which can transmit power and motion from one shaft to another shaft by means of successive engagement of teeth. • A gear is a component within a transmission device that transmits rotational force to another gear or device • Gear consist two wheels – Small –Pinion , large -Gear 2S.R. Thorat/BME/Unit-1/Gears
- 38. TYPES OF GEARS 1. According to the position of axes of the shafts. a. Parallel Axes Gear 1.Spur Gear 2.Helical Gear 3.Herring bone Gear b. Intersecting Axes Gear Bevel Gear c. Non-intersecting and Non-parallel Axes Gear worm and worm gears 3S.R. Thorat/BME/Unit-1/Gears
- 39. Spur Gear • Teeth is parallel to axis of rotation • Transmit power from one shaft to another parallel shaft • Applications- Machine tool gear box , Automobile gearbox, Watches 4S.R. Thorat/BME/Unit-1/Gears
- 40. Helical Gear • The teeth on helical gears are cut at an angle to the face of the gear . • This gradual engagement makes helical gears operate much more smoothly and quietly than spur gears . 5S.R. Thorat/BME/Unit-1/Gears
- 41. Herringbone gears • To avoid axial thrust, two helical gears of opposite hand can be mounted side by side, to cancel resulting thrust forces • Herringbone gears are mostly used on heavy machinery. 6S.R. Thorat/BME/Unit-1/Gears
- 42. Rack and pinion • Rack and pinion gears are used to convert rotation (From the pinion) into linear motion (of the rack) • Application- steering system on many cars 7S.R. Thorat/BME/Unit-1/Gears
- 44. Bevel gears • Bevel gears are useful when the direction of a shaft's rotation needs to be changed • They are usually mounted on shafts that are 90 degrees apart, but can be designed to work at other angles as well. • The teeth on bevel gears can be straight, spiral or hypoid • Applications- locomotives, automobiles, printing presses, railway track inspection machines, etc. 9S.R. Thorat/BME/Unit-1/Gears
- 45. Straight and Spiral Bevel Gears 10S.R. Thorat/BME/Unit-1/Gears
- 46. WORM AND WORM GEAR • Worm gears are used when large gear reductions are needed. • It is common for worm gears to have reductions of 20:1, and even up to 300:1 or greater • The worm can easily turn the gear, but the gear cannot turn the worm. • Applications- material handling and transportation machinery, machine tools, automobiles etc 11S.R. Thorat/BME/Unit-1/Gears
- 47. WORM AND WORM GEAR 12S.R. Thorat/BME/Unit-1/Gears
- 49. GEAR TRAINS • A gear train is combination of two or more gear which are used to transmit power and speed . • It is necessary when large speed reduction is required in small space. • it is used in watches , automobiles. Types- 1.Simple gear train 2.Compound gear train 3.Planetary gear train g g p p p g Z D n i Z d n = = = 14S.R. Thorat/BME/Unit-1/Gears
- 50. 1.Simple Gear Train • The most common of the gear train is the gear pair connecting parallel shafts. • Only one gear may rotate about a single axis • Number of intermediate gears odd , motion of driver and driven gear is same. • Number of intermediate gears even , motion of driver and driven gear is opposite. 15 S.R. Thorat/BME/Unit-1/Gears
- 51. 2.Compound Gear Train • For large velocities, compound arrangement is preferred • Two or more gears may rotate about a single axis 16S.R. Thorat/BME/Unit-1/Gears
- 52. Planetary Gear Train (Epicyclic Gear Train) 17S.R. Thorat/BME/Unit-1/Gears