GTU BE/B.Tech 2017 Winter Question Papers || Gujarat Technological University
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Seat No.:
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Subject Code: 2171909
GUJARAT TECHNOLOGICAL UNIVERSITY
Enrolment No.
BE - SEMESTER-VII (NEW) EXAMINATION — WINTER 2017
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Subject Name: Machine Design
Date:18/11/2017
Time: 10.30 AM to 01.30 PM
Total Marks: 70
Instructions:
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- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
- Use of design data book is permitted.
| Q1 | (a) | Why dissimilar materials are used for worm and worm wheel?. | 04 |
| (b) | And explain the designation 4/29/10.6/2.5/50 used for the pair of worm and worm gear. | 07 | |
| (c) | Explain the followings: 1) Interference and undercutting of gears i1) Static and Dynamic load carrying capacity of rolling contact bearings | 03 | |
| Q2 | (a) | What are the major advantages of using geometric progression of for speed regulation in a gear box?. And explain the design procedure of 8-speed gear box- for machine tool application with the assumption of suitable-and necessary data. | 04 |
| (b) | How are the gears classified?. Explain the role of pressure angle in the gears. | 07 | |
| (c) | Explain different types of gear tooth failures | 07 | |
| Design a spur gear drive to transmit 30 HP at 900 r.p.m. Speed reduction ratio is 2.5 . Material for pinion and wheel are C.I steel and‘Cast Iron respectively. Take pressure angle of 20° . Design bending stress for pinion material is 85 N/mm? and surface endurance limit for pinion material is 620 N/mm?Z Take the following data for the given gears: Quality of the gears to be - Grade 12 Service factor, €, = 1.5 for light shock | |||
| OR | |||
| Design the bevel gear pair for the following specification using Carl Barth velocity factor and wear consideration: Power transmitted : 40 kW Input speed 1 360 rpm Reduction ratio 03 Shaft angle : 900 Application . Agitator | |||
| Q.3 | (a) | Give the classification of hydrodynamic bearings based on lubrication. | 03 |
| (b) | Explain the significance of L/D ratio and minimum oil-film thickness in hydrodynamic bearings. | 04 | |
| (c) | The following data is given for a 360° hydrodynamic bearings: Radial load : 3.1 kN Journal diameter : 50 mm Bearing length : 50 mm Journal speed : 1440 rpm Radial clearance : 50 microns Viscosity of lubricant : 25c¢P Density of lubricant : 860 kg /m’ Sp. Heat of lubricant : 1.76 kJ / kg °C Assuming that the total heat generated in the bearing is carried by the total oil flow in the bearing. Calculate: 1) Sommerfeld Number i1) Minimum oil-film thickness iii) The coefficient of friction iv) The power lost in friction v) The total flow rate of lubricant in liter /minute vi) Side leakage | 07 | |
| OR | |||
| (b) | What are the difference between Hydrodynamic and Hydrostatic bearings. | 03 | |
| (c) | Derive the “ Petroff’s equation with assumptions made there in. | 04 | |
| A Petroff’s sleeve bearing consists of a sleeve having a bore diameter of 100.1 mm and a length of 100 mm. A shaft having 100 mm diameter supports a load of 4000 N. A shaft runs at 2880 r.p.m in the sleeve. If the frictional torque on the shaft is 10 N-m, find 1) The absolute viscosity of lubrication i1) The bearing pressure ii1) The coefficient of friction and iv) The power lost in bearing. | |||
| Q4 | (a) | Define static and dynamic load carrying capacities of the rolling contact bearings. | 03 |
| (b) | Derive the equation for equivalent dynamic load for bearing under cyclic loads. | 04 | |
| (c) | A single-row deep groove ball bearing operated with the following work cycle. If the expected life of the bearing is 13000 hours with reliability of 90%. Calculate the dynamic load rating of the bearing and determine reliability of a system consisting of four such bearings. The work cycle is as follows: Gear | Axial | Radial | Radial | Thrust | Race Cs N % time load | load Factor | factor | rotation rpm engage (KN) | (KN) d 1 1.5 5 0.56 1.1 Inner 1.25 | 960 30 % I 073 |37 0.56 1.3 Outer 1.4 | 1440 | 40% I - - - - Outer - 720 30 % | 07 | |
| OR | |||
| Q.5 | (a) | Classify the rolling contact bearings. And explain how they are designated according to ISI code of practice. | 03 |
| (b) | Define the following terms: (1) Rating life of rolling contact bearings (i1) Median life (i) Equivalent dynamic load (iv) Reliability of bearing | 04 | |
| (c) | Establish the following relationship between the life and reliability of the rolling contact bearing; L log, Lo log, (R.,o) | 07 | |
| Q.5 | (a) | Why the cylinder liners are being used in I.C.Engine?. What are the desirable properties of the materials for the cylinder liners. | 03 |
| (b) | What are the functions of I.C.Engine piston ?. List the elements involved in the [.C.Engine piston. | 04 | |
| (c) | The following' data is given for the piston of a four-stroke diesel engine: Cylinder bore : 250 mm Material of piston rings : Gray C.I. Allowable tensile stress : 100 N/ mm? Allowable radial pressure on cylinder wall :0.03 MPa Thickness of piston head : 42 mm No. of piston rings : 4 Calculate: 1) Radial width of the piston rings i1) Axial thickness of the piston rings iii) Gap between the free ends of the piston rings before and after the assembly 1v) Width of the top land v) Width of the ring grooves vi)Thickness of the piston barrel | 07 | |
| OR | |||
| Q.5 | (a) | Whatare the basic objectives of material handling systems?. | 03 |
| (b) | What are the different types of ropes used in EOT cranes ?. | 04 | |
| (c) | How they are designated and selected in the hoisting mechanism. Design the following components of EOT cranes for the following requirements: Application : class—1I Load to be lifted : 8 tones Hoisting speed : 4m/ min Maximum lift of the load :12m (1) Select through design procedure a suitable wire rope (i1) Sheave in a snatch block assembly of crane. | 07 |
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