Machine Elements in Mechanical Design FIFTH EDITION CHAPTER

Types of Belt Drives • Belt § Flexible power transmission element that seats tightly

Types of Belt Drives • Belt § Cog belts: applied to standard Vgrooved sheaves;

V-Belt Drives • V-Belt Drives § Pulley, with circumferential groove carrying belt, called a

V-Belt Drives • V-Belt Drives § Speed ratio between driving and driven sheaves inversely

V-Belt Drive Design • Drive Selection § Rated power of driving motor or prime

V-Belt Drive Design • Drive Selection § § Belt length Size of driving and

V-Belt Drive Design • Drive Selection § Number of belts § Initial tension on

V-Belt Drive Design • Design Data § Data: narrow-section belts: 3 V, 5 V,

Table 7 -1 V-Belt Service Factors 1 Machine Elements in Mechanical Design , Fifth

Table 7 -2 Belts (in) Standard Belt Lengths for 3 V, 5 V, and

V-Belt Drive Design • Design Data § Initial tension given a belt critical; ensures

Synchronous Belt Drives • Synchronous (Timing) Belts § Ribs or teeth across underside of

Table 7 -4 Drives Types and Sizes of Synchronous Belt Machine Elements in Mechanical

Chain Drives • Chain Drives § Chain: power transmission element; series of pin-connected links

Table 7 -5 U. S. Roller Chain Sizes Machine Elements in Mechanical Design ,

Table 7 -6 Ratings Metric Roller Chain Sizes and Strength Machine Elements in Mechanical

Table 7 -6 (continued) Strength Ratings Metric Roller Chain Sizes and Machine Elements in

Design of Chain Drives • Three Modes of Failure § Fatigue of link plates

Design of Chain Drives • Types of Data § Ratings based on speed of

Design of Chain Drives • Types of Data § Ratings are for a single

Design of Chain Drives • Rated Power for Sizes of Standard Chain Machine Elements

Table 7 -7 Horsepower Ratings—Single Strand Roller Chain No. 40 Machine Elements in Mechanical

Table 7 -8 Horsepower Ratings—Single Strand Roller Chain No. 60 Machine Elements in Mechanical

Table 7 -9 Horsepower Ratings—Single Strand Roller Chain No. 80 Machine Elements in Mechanical

Table 7 -10 Service Factor for Chain Drives Machine Elements in Mechanical Design ,

Design of Chain Drives • Lubrication § Essential lubrication provided for chain drives §

Table 7 -11 Recommended Lubricant for Chain Drives Machine Elements in Mechanical Design ,

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Machine Elements in Mechanical Design FIFTH EDITION CHAPTER 7 Belt Drives and Chain Drives Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Types of Belt Drives • Belt § Flexible power transmission element that seats tightly on set of pulleys or sheaves § Flat belt: simplest type; often made from leather or rubber-coated fabric § Synchronous (timing) belts: ride on sprockets having mating grooves into which the teeth on the belt seat Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Types of Belt Drives • Belt § Cog belts: applied to standard Vgrooved sheaves; greater flexibility and higher efficiency compared with standard belts § V-belt drive: widely used particularly in industrial drives and vehicular applications Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

V-Belt Drives • V-Belt Drives § Pulley, with circumferential groove carrying belt, called a sheave § Size of sheave indicated by its pitch diameter Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

V-Belt Drives • V-Belt Drives § Speed ratio between driving and driven sheaves inversely proportional to ratio of sheave pitch diameters § Design value of the ratio of tight side tension to slack side tension is 5. 0 for Vbelt drives. Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

V-Belt Drive Design • Drive Selection § Rated power of driving motor or prime mover § Service factor based on type of driver/driven load § Center distance § Power rating for one belt as a function of size and speed of smaller sheave Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

V-Belt Drive Design • Drive Selection § § Belt length Size of driving and driven sheaves Correction factor for belt length Correction factor for angle of wrap on smaller sheave Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

V-Belt Drive Design • Drive Selection § Number of belts § Initial tension on belt § Many design decisions depend on application and space limitations Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

V-Belt Drive Design • Design Data § Data: narrow-section belts: 3 V, 5 V, 8 V. § These sizes cover wide range of power transmission capacities. Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

V-Belt Drive Design • Design Data § Initial tension given a belt critical; ensures belt will not slip under design load Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Synchronous Belt Drives • Synchronous (Timing) Belts § Ribs or teeth across underside of belt § Teeth mate with grooves in driving and driven pulleys (sprockets) providing positive drive without slippage § Critical to operation of systems as printing, material handling, packaging, assembly Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Chain Drives • Chain Drives § Chain: power transmission element; series of pin-connected links § Provides for flexibility while enabling chain to transmit large tensile forces § Roller chain: roller on each pin provides low friction between chain and sprockets Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Table 7 -6 (continued) Strength Ratings Metric Roller Chain Sizes and Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Design of Chain Drives • Three Modes of Failure § Fatigue of link plates due to repeated application of tension in tight side of chain § Impact of rollers as they engage sprocket teeth § Galling between pins of each link and bushings on the pins Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Design of Chain Drives • Types of Data § Ratings based on speed of smaller sprocket; expected life of approximately 15, 000 hours § For a given speed, power capacity increases with number of teeth on sprocket § For given sprocket size, power capacity increases with increasing speed up to a point; then it decreases Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Design of Chain Drives • Types of Data § Ratings are for a single strand of chain. § Although multiple strands do increase power capacity, they do not provide direct multiple of single-strand capacity. § Ratings are for a service factor of 1. 0. Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved

Design of Chain Drives • Lubrication § Essential lubrication provided for chain drives § Petroleum-based lubricating oil similar to engine oil recommended § Manual or drip lubrication § Bath or disc lubrication § Oil stream lubrication Machine Elements in Mechanical Design , Fifth Edition Robert L. Mott Copyright © 2014 by Pearson Education, Inc. All Rights Reserved