GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER- IV (New) EXAMINATION - WINTER 2019
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Subject Code: 2141907 Date: 14/12/2019Subject Name: Machine Design & Industrial Drafting
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
- Attempt all questions.
- Make suitable assumptions wherever necessary.
- Figures to the right indicate full marks.
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MARKS
Q.1 (a) Explain Hole basis system and Shaft basis system. 03
(b) Explain selection and use of theories of failure. 04
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(c) Explain types of fit with suitable examples. 07
Q.2 (a) Compare compressive stress and crushing stress. 03
(b) Describe factor of safety. 04
(c) Design a spigot and socket type cotter joint to connect 07 two similar rods subjected to 75 kN axial loads in both the direction. For the rod as well as cotter material, shear stress is equal to 80 % of tensile stress. Tensile stress and crushing stress are 50 N/mm² and 100 N/mm² respectively. Determine (1) Diameter of rod (2) Diameter of spigot (3) Diameter of socket sleeve.
OR
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(c) A bell crank lever is to be designed to lift the load of 07 10 kN acting at the end of short arm of the lever. The length of short arm and long arm is 500 mm and 750 mm respectively. Allowable shear stress and tensile stress for lever and pin materials is 60 N/mm² and 80 N/mm² respectively. Allowable bearing pressure for pin material is 8 N/mm². For pin L/D=1.25. And for the rectangular cross section of the lever, ratio of height to width is 3. Determine: (1) dimension of the fulcrum pin (2) Dimension of lever.
Q.3 (a) Explain different types of supports. 03
(b) Define: (1) Pitch (2) Lead (3) Nominal diameter (4) Core 04 diameter for Power screw.
(c) A 400 mm long alloy steel rod is used to support an axial 07 compressive load of 65 kN. One end of rod is fixed and other end is free to support load. Assuming compressive yield strength 550 N/mm² and modulus of elasticity 210 GPa. Calculate diameter of rod by buckling consideration. Use Rankin’s formula with Rankin’s constant s = 1 /7500 and factor of safety is 3.5.
OR
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Q.3 (a) Explain different end condition of column. 03
(b) Define: (1) Pitch (2) Back Pitch (3) Diagonal Pitch (4) 04 Margin for Riveted joint.
(c) An I section 500 mm x 250 mm X 10 mm and 10 m 07 long is used as a strut with both ends fixed. Take young’s modulus E= 200 GPa. Calculate Euler’s critical load.
Q.4 (a) Compare between shaft, axle and spindle. 03
(b) List types of key with neat figure. 04
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(c) A muff coupling is used to connect two shafts rotating 07 at 300 rpm and transmitting 55 hp. Calculate: (1) Shaft diameter (2) Outside diameter of sleeve (3) Design of key. Assume permissible shear stress for shaft and key as 42 N/mm² and for cast iron sleeve as 15 N/mm².
OR
Q.4 (a) Classify coupling. 03
(b) Define : (1) Shaft (2) Key (3) Coupling (4) Axle 04
(c) Calculate the power transmission capacity of a muff 07 coupling having shaft diameter of 80 mm, muff diameter of 150 mm rotating at 150 rpm. Permissible shear stress for shaft and muff are 50 N/mm² and 10 N/mm² respectively.
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Q.5 (a) Illustrate surface roughness symbol and direction of lay 03 and their symbol.
(b) For single riveted lap joint, the plate thickness is 12 mm 04 and the pitch of the joint is 70 mm. Determine rivet diameter, tearing, shearing, and crushing efficiencies of the joint. Take Shear stress=60 N/mm², Crushing stress=100 N/mm², Tensile stress=80 N/mm².
(c) Analyze the force analysis for square threaded power 07 screw.
OR
Q.5 (a) Illustrate flatness, straightness and circularity with 03 symbol.
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(b) A circular shaft, 80 mm in diameter is welded to support 04 by means of a circumferential fillet weld. It is subjected to a torsion moment of 3000 N-m. Determine the size of weld, if the maximum shear stress in the weld is not to exceed 70 N/mm².
(c) Analyze different stresses during design of screw and 07 nut.
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