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Text Book of Machine Design Part 20

V-Belt and Rope Drives | CONTENTS c H A P T E R 20 V-Belt and Rope Drives 1. Introduction. 2. Types of V-belts and Pulleys. 3. Standard Pitch Lengths of V-belts. 4. Advantages and Disadvantages of V-belt Drive over Flat Belt Drive. 5. Ratio of Driving Tensions for V-belt. 6. V-flat Drives. 7. Rope Drives. 8. Fibre Ropes. 9. Advantages of Fibre Rope Drives. 10. Sheave for Fibre Ropes. 11. Ratio of Driving Tensions for Fibre Rope. 12. Wire Ropes. 13. Advantages of Wire Ropes. 14. Construction of Wire Ropes. 15. Classification of Wire Ropes. 16. Designation of Wire Ropes. 17. Properties of Wire Ropes. 18. Diameter of Wire and Area of Wire Rope. 19. Factor of Safety for Wire Ropes. 20. Wire Rope Sheaves and Drums. 21. Wire Rope Fasteners. 22. Stresses in Wire Ropes. 23. Procedure for Designing a Wire Rope. 20.1 Introduction We have already discussed that a h-belt is mostly used in factories and workshops where a great amount of power is to be transmitted from one pulley to another when the two pulleys are very near to each other. The h-belts are made of fabric and cords moulded in rubber and covered with fabric and rubber as shown in Fig. 20.1 a . These belts are moulded to a trapezoidal shape and are made endless. These are particularly suitable for short drives. The included angle for the h-belt is usually from 30 to 40 . The power is transmitted by the wedging The wedging action of the h-belt in the groove of the pulley results in higher forces of friction. A little consideration will show that the wedging action and the transmitted torque will be more if the groove angle of the pulley is small. But a small groove angle will require more force to pull the belt out of the groove which will result in loss of power and excessive belt wear due to friction and heat. Hence the selected groove angle is a compromise between the two. Usually the groove angles of 32 to 38 are used. 727 CONTENTS 728 A Textbook of Machine Design action between the belt and the F-groove in the pulley or sheave. A .