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Text Book of Machine Design Part 21

Chain Drives | CONTENTS c H A P T E R 21 Chain Drives 1. Introduction. 2. Advantages and Disadvantages of Chain Drive over Belt or Rope Drive. 3. Terms Used in Chain Drive. 4. Relation Between Pitch and Pitch Circle Diameter 5. Velocity Ratio of Chain Drives. 6. Length of Chain and Centre Distance. 7. Classification of Chains. 8. Hoisting and Hauling Chains. 9. Conveyor Chains. 10. Power Transmitting Chains. 11. Characteristics of Roller Chains. 12. Factor of Safety for Chain Drives. 13. Permissible Speed of Smaller Sprocket. 14. Power Transmitted by Chains. 15. Number of Teeth on the Smaller or Driving Sprocket or Pinion. 16. Maximum Speed for Chains. 17. Principal Dimensions of Tooth Profile. 18. Design Procedure for Chain Drive. 21.1 Introduction We have seen in previous chapters on belt and rope drives that slipping may occur. In order to avoid slipping steel chains are used. The chains are made up of number of rigid links which are hinged together by pin joints in order to provide the necessary flexibility for wraping round the driving and driven wheels. These wheels have projecting teeth of special profile and fit into the corresponding recesses in the links of the chain as shown in Fig. 21.1. The toothed wheels are known as sprocket wheels or simply sprockets. The sprockets and the chain are thus constrained to move together without slipping and ensures perfect velocity ratio. These wheels resemble to spur gears. 759 CONTENTS 760 A Textbook of Machine Design Fig. 21.1. Sprockets and chain. The chains are mostly used to transmit motion and power from one shaft to another when the centre distance between their shafts is short such as in bicycles motor cycles agricultural machinery conveyors rolling mills road rollers etc. The chains may also be used for long centre distance of upto 8 metres. The chains are used for velocities up to 25 m s and for power upto 110 kW. In some cases higher power transmission is also possible. 21.2 Advantages and Disadvantages of Chain Drive over