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Posted Date: 23 Jul 2009 Posted By: phanidra Member Level: Gold
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2009 Jawaharlal Nehru Technological University Mechanical Engineering Jntu Hyderabad,Code No: R05320305 , III B.Tech II Semester Regular Examinations, Apr/May 2009 ,DESIGN OF MACHINE MEMBERS-II Question paper
Code No: R05320305 Set No. 2
III B.Tech II Semester Regular Examinations, Apr/May 2009
DESIGN OF MACHINE MEMBERS-II
( Common to Mechanical Engineering and Production Engineering)
Time: 3 hours Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
? ? ? ? ?
1. (a) A 75mm journal bearing 100mm long is subjected to 2.5kN at 600r.p.m. If
the room temperature is 240C. What viscosity of oil should be used to limit
the bearing surface temperature at 550C. D/C=1000.
(b) A roller bearing is selected to withstand a radial load of 40kN and life of
1200hours at 600r.p.m. What load rating would you look for in searching
from manufacturers catalogue if it specifies load at speed 500r.p.m and life
3000hours. [8+8]
2. (a) What types of crankshafts are commonly used?
(b) A double acting steam engine has the following specifications:
Cylinder core=500mm
Piston stroke =750mm
Maximum pressure on piston=175N/cm2
Connecting rod length=140mm
Select suitable material and design the connecting rod. [4+12]
3. (a) What are the various types liners?
(b) Design a Aluminium piston for a single acting 4 Stroke petrol engine of the
following specifications :
Cylinder bore = 100mm
Stroke Length =120mm
Maximum gas pressure = 5MPa
Break mean effective Pressure =0.65MPa
Fuel Consumption = 0.17kg/bhp/min
Speed =220rpm
Assume suitable data if necessary. [2+14]
4. The dimensions of 100 kN Crane hook are shown in figure 4. Determine the stresses
at the inside and out side fibers of the hook on a horizontal diameter passing through
the center of curvature.5. Power of 70kWat 850 rpm is to be transmitted from an electric motor to compressor
shaft at 400 rpm by V-belts. The approximate larger pulley diameter is 1500mm.
The approximate center distance is 1650mm, and overload factor is to be taken as
1.5. Give a complete design of the belt drive. A belt with cross sectional area of
350mm2 and density 1000kg/m3 and having an allowable tensile strength 2 MPa
is available for use. The coefficient of friction between the belt and the pulley
may be taken as 0.28. The driven pulley is overhung to the extent of 300mm from
the nearest bearing and is mounted on a shaft having a permissible shear stress of
40MPa with the help of a key. The shaft, the pulley and the key are also to be
designed. [16]
6. A single stage helical gear reducer is to receive power from a 1440 r.p.m., 25kW
induction motor. The gear tooth profile is involute full depth with 20o normal
pressure angle. The helix angle is 23o, number of teeth on pinion is 20 and the gear
ratio is 3. Both the gears are made of steel with allowable beam stress of 90MPa
and hardness 250B.H.N.
(a) Design the gears for 20% overload carrying capacity from the standpoint of
bending strength and wear.
(b) If the incremental dynamic load of 8kN is estimated in tangential plane, what
will be the safe power transmitted by the pair at the same speed? [16]
7. (a) Explain the procedure of checking the design of a screw for buckling.
(b) A 50kN capacity screw jack consists of a square threaded steel screw, meshing
with a bronze nut. The nominal diameter is 70mm and the pitch is 10mm.
The permissible bearing pressure at the threads is 7N/mm2. Determine
i. the length of the nut and ii. the transverse shear stress induced in the nut. [6+10]
8. Design the head stock gear box of a lathe having arrangement for 12 spindle speeds
ranging from 40 to 1000 rev/min.
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