1
Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER-VIII EXAMINATION WINTER 2018
Subject Code:X81902 Date: 15/11/2018
Subject Name: Machine Design-II
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1

Explain the following terms: (Any FOUR)
1. Helix angle
2. Cone centre
3. Lead angle
4. Pressure angle
5. Circular pitch
08

Explain the phenomenon of interference in involute gears. What are the conditions to be satisfied in order to avoid interference?
06
Q.2

List and explain the different causes of gear tooth failures and suggest possible remedies to avoid such failures.
07

Define formative or virtual number of teeth on a helical gear. Derive the expression used to obtain its value.
07
OR

A pair of mating carefully cut spur gears has 20° full depth of 4 mm module. The number of teeth on pinion and gears are 40 and 120, respectively. The face width is 40 mm. If the pinion and gear are made of steel with fb static 233 MPa and surface hardness of 300 BHN, calculate the safe power that can be transmitted when the pinion is run at 1200 rpm.
07
Q.3

How the bevel gears are classified? Explain with neat sketches.
07

Explain the various forces acting on worm and worm gears?
07
OR
Q.3

Explain the various stresses induced in the connecting rod.
07

Sketch a valve gear mechanism of horizontal internal combustion engine and label its various parts also discuss the materials commonly used for making the valve of an I. C. engine.
07
Q.4

Discuss about various section of connecting rod. Why "I" section is chosen for the connecting rod in the design of I. C. Engine?
07

A four stroke diesel engine has the following specifications
Brake power 5 kW;
Speed 1200 r.p.m.;
Indicated mean effective pressure 0.35 N mm2;
Mechanical efficiency 80
Determine
1. bore and length of the cylinder;
2. thickness of the cylinder head; and
3. Size of studs for the cylinder head.
Assume l/D ratio as 1.5 and safe tensile stress for cylinder head material as 42 MPa and for stud material as 65 MPa
07
OR
2
Q.4

A three stage gear box with twelve speeds is to be designed based on R10 series with minimum spindle speed of 125 rpm. The second stage consists of three speed steps. The electric motor is connected to the gear box through a belt drive and runs at 1440 rpm and transmits of 5 kW. Using standard spindle speeds,
Draw the structure and speed diagram for the arrangement.
Determine the ratio of the belt pulley diameters.
Determine the number of teeth on each gear of the gear box.
07

What is structure diagram? Explain the method of drawing structure diagram of gear box.
07
Q.5

Classify different types of conveyors. Explain construction and working of any one conveyor.
07

Explain wire ropes with its designation. State the advantages of wire ropes. How will you select the wire ropes?
07
OR
Q.5

Why trapezoidal section is used for hook? Draw a neat sketch of single hook and show the critical section on it.
07

Design a crane hook for lifting capacity of 5 tones. It is made from forged steel and has triangular section. Take permissible tensile stress 80 N/mm2 .Use data design book to standardize the dimension of hook.
07