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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER EXAMINATION SUMMER 2017
Subject Code: X51903 Date: 04/05/2017
Subject Name: Machine Design-I
Time: 02.30PM to 05.00PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Draw neat sketches wherever necessary.
5. Use of any design databook is not permissible.
Q.1

Answer Any one:
Explain manufacturing and assembly considerations in detail with neat sketches.
Explain design for casting and welding in detail with neat sketches.
07

Answer the following
Explain Contact Stresses giving suitable examples.
Write a detailed note on: Standardization and preferred numbers.
07
Q.2

State the advantages and disadvantages of the chain drive over belt drive.
Explain selection procedure for chain drive.
06

Decide No. of belts required for the drive from the following data.
Motor Power 20 kw Belt width 22 mm
Speed of Motor 1440 rpm Belt thickness 14 mm
Speed reduction 3 Belt area 236.67 mm2
Mass per meter length of belt 0.27 kg/m
Maximum allowable tension per belt 850 N
Coefficient of friction 0.20
Centre distance between the pulleys 2 x diameter of driven pulley
08
OR

The following data refers to flat belt drive:
Power to be transmitted 15 kW Motor speed 1440 r.p.m.
Speed of driven pulley 480 r.p.m. Density of belt material 950 Kg/ m3
Centre distance between two pulleys 810 mm
Approx.belt speed 20 m/sec Coefficient of friction=0.35
Modulus of elasticity for belt material 100 MPa
Permissible stress for belt material 2.25 Mpa Belt thickness 5 mm
Calculate pulley diameters length and width of the belt
08
Q.3

State and explain the factors affecting of Selection of anti-friction bearings.
07

Explain the Soderberg and Goodman's diagram with the help of neat sketches.
07
OR
2
Q.3

Explain the design procedure for journal bearing.
07

Explain different types of end closure used for cylindrical pressure vessels with neat sketches.
07
Q.4

Write a detailed note on: Design of disc springs (bellievele) with neat sketch.
05

The following data is given for the locomotive:
Load on rear axle of tractor of trolley 72000 N
Span 1200 mm Width of band 100 mm
No. of main leaves 3 Total no. of leaves 15
Ratio total depth to width 2 [σbend] for spring material 420 MPa
Thickness of leaf 10 mm G 0.84 x 105 MPa
σbending for pin material 120 MPa σbearing for pin material 10 MPa
Find width and thickness of the leaves.
09
OR
Q.4

Define Wahls' factor and its use in design of spring.
05

Calculate the dimensions of the helical compression spring used in spring operated relief valve for the following data.
Limiting mean coil diameter 40 mm,
Maximum operating pressure 1.25 MPa valve diameter 25 mm
Valve lift for pressure rise for 10% pressure rise is 3.5 mm
Maximum allowable stress 500 MPa
Spring index 6 Modulus of rigidity 8.34 ×104 MPa.
09
Q.5

Compare the simple band brake and differential band brake.
List and explain the friction materials used in clutch.
05

A single plate clutch having two pairs of contacting surfaces effective and the following specification:
Torque to be transmitted 531 N m Coefficient of friction 0.30
Outer diameter is limited to 270 mm
Permissible pressure for the lining 0.3 MPa
Permissible stress for shaft material 45 MPa
Assuming uniform axial wear, find inner dia. of friction disc and spring force required to keep the clutch engaged.
09
OR
Q.5

What is the importance of p-v products in brake design?
Explain the uniform wear concept used in clutch design.
05

The following data refers to a simple block brake (refer fig given below):
Torque capacity =15 N m Coefficient of friction 0.30
Maximum pressure for lining 1 MPa Width of block length of block
Find
The actuating force ii) Dimensions of the block iii) Resultant higed pin reaction iv) Rate of heat generated if brake drum rotates at 50 r.p.m.
09
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