tailieunhanh - Ebook Problems and solutions in mechanical engineerig: Part 2

(BQ) Part 2 book "Problems and solutions in mechanical engineering" has contents: Fundamental concepts, definitions and zeroth law, second law of thermodynamics, properties of steam and thermodynamics cycle, non concurrent force system, concurrent force system,. and other contents. | 216 / Problems and Solutions in Mechanical Engineering with Concept CHAPTER 10 APPLICATION OF FRICTION: BELT FRICTION Q. 1: What is belt? How many types of belt are used for power transmission? Sol: The power or rotary motion from one shaft to another at a considerable distance is usually transmitted by means of flat belts, Vee belts or ropes, running over the pulley. But the pulleys contain some friction. Types of Belts Important types of belts are: 1. Flat belt 2. V- belt Rectangular belt V-Belt Pulley (a) 3. Circular Belt (b) Pulley Circular belt (c) Fig Flat Belt The flat belt is mostly used in the factories and workshops. Where a moderate amount of power is to be transmitted, from one pulley to another, when the two pulleys are not more than 10m apart. V-Belt The V-belt is mostly used 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. Circular Belt or Rope The circular belt or rope is mostly used where a great amount of power is to be transmitted from one pulley to another, when the two pulleys are more than 5m apart. Application of Friction: Belt Friction / 217 Q. 2: Explain how many types of belt drive used for power transmission? Also derive their velocity ratio. Sol: There are three types of belt drive: (1) Open belt drive (2) Cross belt drive (3) Compound belt drive (1) Open Belt Drive When the shafts are arranged in parallel and rotating in the same direction, open belt drive is obtained. In the diagram , pulley 'A' is called as driver pulley because it is attached with the rotating shaft. Driven or Follower Pulley Drive Pulley Slack Side A B + + Tight Side Totating Shaft Fig Velocity Ratio (.) for Open Belt Drive K C N α A+ α x M E α B H F D Fig Consider a simple belt drive (., one driver and one follower) as shown in fig . 218 / Problems and Solutions in Mechanical Engineering with Concept Let D1 = Diameter .