b)

0)

ಖ

0)

111124 Pages: 3

A 360 ० hydrodynamic journal bearing operates at 1200 rpm and carries a load of
5.5 ‏ءا‎ N. The journal diameter is 55 mm and length is 55 mm. The bearing is
lubricated with SAE 20 oil and the operating temperature of oil is 79°C. Assume
radial clearance as 0.025 mm and the attitude angle as 60°. Determine: (i) bearing
pressure, (ii) Attitude, (iii) minimum film thickness, (iv) heat generated, (v) heat
dissipated, if the ambient temperature is 25°C, and (vi) amount of artificial
cooling if necessary.
PART ‏تا‎

Answer any two full questions, each carries 15 marks.
A motor shaft rotating at 1440 rpm has to transmit 15 kW power to a low speed
shaft running at 500 rpm. A 20° pressure angle full depth involute system of gear
tooth is used. The pinion has 25 teeth. Both gear and pinion are made of cast iron
having allowable static strength of 55 MPa. Design a suitable spur gear drive and
check the design for dynamic load and wear.
State and explain law of gearing with a neat sketch.
Give an account on different modes of failure of gear tooth.
Explain why dynamic factors need to be considered in the design of gears.
A helical gear speed reducer is to be designed. The rated power of the speed
reducer is 75 kW at a pinion speed of 1200 rpm. The speed ratio is 3:1. For
medium shock conditions and 24 hr operation, design the gear pair. The teeth are

20° full depth involute in the normal plane and helix angle is 30°.

PART C
Answer any two full questions, each carries 20 marks.
Design a connecting rod of I cross section for an IC engine running at 1800 rpm

and developing a maximum pressure of 3.15 N/ mm’. The diameter of the piston
is 100 mm, mass of the reciprocating parts per cylinder is 2.25 kg, length of the
connecting rod is 380 mm, stroke of the piston is 190 mm and compression ratio
is 6:1. Take a factor of safety of 6 for the design. The maximum allowable
bearing pressure at big end and the small end are respectively 10 N/mm? and 15
N/mm?. The density of material of the rod may be taken as 8000 kg/m? and
allowable stress in the bolts as 85 N/mm? and in the cap as 80 N/mm’.

Explain why I section is usually preferred in the case of a connecting rod?

Page 2of 3

(15)

(15)

(7)
(4)
(4)
(15)

(16)

(4)