VARDHAMAN COLLEGE OF ENGINEERING
(AUTONOMOUS)
B. Tech VI Semester Regular Examinations, May 2018
(Regulations: VCE-R15)
DESIGN OF MACHINE MEMBERS-II
(Mechanical Engineering)
Date: 14 May, 2018 FN
Time: 3 hours
Max Marks: 75
Answer ONE question from each Unit
All Questions Carry Equal Marks
Unit I
1.
A hardened steel journal and a bronze backed babbit bearing is used to support a load of 4500 N at 600 rpm. An abundance of oil is supplied by means of oiling rings. The bearing is relieved for 20o from the normal to the load line. The oil used is ring-oiled bearing oil and its operating temperature is 70oC. Determine:
i. Diameter of journal and length of bearing
ii. Coefficient of friction by Mckee's equation
iii. Sommerfeld number
iv. Minimum film thickness
v. Heat generated
vi. Heat dissipated by the bearing based on projected area of the bearing
15M
2.

What is the significance of Bearing characteristic number and bearing modulus for journal bearing?
7M

A single row deep groove ball bearing No. 6002 is subjected to an axial thrust load of 1000N and a radial load of 2200 N. Find the expected life that 50% of the bearings will complete under this condition.
8M
Unit II
3.
A four stroke diesel engine has the following specifications: Brake power 5kW; Speed=1200r.p.m.; Indicated mean effective pressure=0.35 N/mm2; Mechanical efficiency=80 Determine:
i. Bore and length of the cylinder
ii. Thickness of the cylinder head
iii. Size of studs for the cylinder head
15M
4.
Design a cast iron piston for a single acting four stroke engine for the following data: Cylinder bore 100 mm; Stroke 125 mm; Maximum gas pressure 5N/mm2; Indicated mean effective pressure 0.75 N/mm2; Mechanical efficiency Fuel consumption 0.15 kg per brake power per hour; Higher calorific value of fuel 42 × 103 kJ/kg; Speed 2000r.p.m.Any other data required for the design may be assumed.
15M
Unit III
5.

State the assumptions made in deriving lewis equation.
3M

Design a pair of spur gears to transmit 20kW of power at a pinion speed of 1500rpm. The required velocity ratio 3.5:1 200 stub involutes tooth profile to be The static design stress for the pinion is 1000MPa and for the gear is 70Mpa pinion has 16 teeth. Determine the module, face width, and pitch circle diameter of the gears based on a service factor is 1.25.
12M
6.

Explain the design considerations for a gear drive.
3M

Two spur gears are to be used for a rock crusher drive and are to be of minimum size. The gears are to be designed for the following requirements. Power to be transmitted is 20kW; speed of pinion is 1200 rpm, velocity ratio is 3.5 tooth profile 20° stub Involutes. Determine module and face width for strength requirements.
12M
Cont…2
2
Unit IV
7.

What are Mitre gears?
3M

A 90º bevel gearing arrangement is to be employed to transmit 4 kW at 600r.p.m. from the driving shaft to another shaft at 200r.p.m. The pinion has 30 teeth. The pinion is made of cast steel having a static stress of 80MPa and the gear is made of cast iron with a static stress of 55MPa. The tooth profiles of the gears are of 141/2º composite form. Determine the module, face width and pitch diameters for the pinion and gears, from the standpoint of strength and check the design from the standpoint of wear. Take surface endurance limit as 630MPa and modulus of elasticity for the material of gears is EP 200 kN/mm2 and EG 80kN/mm2.
12M
8.

Explain the Formative or equivalent number of teeth for helical gear.
3M

Atriple threaded worm has teeth of 6 mm module and pitch circle diameter of 50mm. If the worm gear has 30 teeth of 14½° and the coefficient of friction of the worm gearing is 0.05, find.1. The lead angle of the worm, 2. Velocity ratio, 3. Centre distance, and 4. Efficiency of the worm gearing.
12M
Unit V
9.

Explain Acme or trapezoidal thread.
3M

A screw jack carries a load of 22kN. Assuming the coefficient of friction between screw and nut as 0.15, design the screw and nut. Neglect collar friction and column action. The permissible compressive and shear stresses in the screw should not exceed 42MPa and 28MPa respectively. The shear stress in the nut should not exceed 21MPa. The bearing pressure on the nut is 14 N/mm2. Also determine the effort required at the handle of 200 mm length in order to raise and lower the load. What will be the efficiency of screw?
12M
10.

What are the major stresses in a helical spring?
3M

Helical compression spring, made of circular wire, is subjected to an axial force that varies from 2.5kN to 3.5kN. Over this range lf force, the deflection of the spring should be approximately 5mm. The spring index can be taken as 5. The spring has square and ground ends. The spring is made of patented and cold drawn steel wire with ultimate tensile strength of 1050 N/mm2 and modulus of rigidity of 81370 N/mm2. The permissible shear stress for the spring wire should. Design the spring and calculate:
i. Wire diameter
ii. Mean coil diameter
iii. Number of active coils
iv. Total number of active turns