Jawaharlal Nehru Technological University Kakinada 2009-2nd Sem B.Tech Code No: Q0303/R05 III Supplementary s, / DESIGN OF MACHINE MEMBERS-II ( Common to Mechanical Engineering and Production

Code No: Q0303/R05
III B.Tech II Semester Supplementary Examinations, Nov/Dec 2009
DESIGN OF MACHINE MEMBERS-II
( Common to Mechanical Engineering and Production Engineering)
Time: three hours
Max Marks: 80
ans any 5 ques.
All ques. carry equal marks

1. (a) describe the subsequent terms:
i. journal
ii. Eccentricity ratio.
(b) A bearing, supporting a power transmitting shaft, is subjected to 3000N radial
load and 45000N axial thrust. The shaft rotates at 400r.p.m and the expected
life of the bearing is 10,000hours. choose a suitable bearing, if the diameter of
the shaft is 40mm.
[2+14]

2. An engine with subsequent particulars is available: Piston diameter =75mm, Stroke of
piston =100mm, Length of connecting rod =200mm, Max explosion Pressure=2.45MPa,
maximum speed =2,500rpm, weigtht of reciprocating parts =1.125 kg, width of cap
=35mm,distance ranging from cap bolts=70mm, density of rod material =0.008kg/cm3.
Find
(a) The diameter and length of crank pin bearing if the permissible pressure is
7MPa and l/d ratio is 0.8.
(b) Size of the bolts if the stress in the cross part is not to exceed 42MPa. The
bolts may be designed to with stand maximum inertia force of the reciprocat-
ing parts at the end of the exhaust stroke.
(c) Thickness of the cap along the longitudinal axis of the connecting rod, if the
safe bending stress is 84MPa.
(d) Cross part of the connecting rod of mild steel forging I part.
(e) Necessary dimensions for small end allowing a bearing pressure of 14MPa. [16]

3. Design a Cast iron piston for a single acting 4 stroke engine for the subsequent
specifications.
Cylinder bore = 100mm, Stroke = 120mm, Maximum gas pressure = 5N/mm2,
Break mean effective pressure = 0.65N/mm2, Fuel consumption = 0.227kg/kW/hr,
Speed =2200 rev/min, presume suitable data.
[16]

4. A curved bar of rectangular section, initially unstressed, is subjected to bending
moment of 1400 N-m which tends to straighten the bar. The part is four cm wide
by five cm deep in the plane of bending, and the mean radius of curvature is 10 cm.
obtain the position of the neutral axis and magnitudes of the greatest bending stress
and draw a diagram to show approximately how the stress varies across the part.
[16]

5. (a) Derive an expression for the length of cross belt drive for at belts.
(b) Determine the percentage increase in power capacity made possible in chang-
ing over from a at belt to a V- belt drive. The diameter of at pulley is the
identical as the pitch diameter of the grooved pulley. The pulley rotates at the
identical speed as the grooved pulley. The coefficient of friction for the at belt
and V- belt is the identical and is equal to 0.35. The V- belt pulley groove angle
is 600. The belts are of the identical material, and have the identical cross-sectional
area. In every case, the angle of lap is 1600.
[8+8]

6. A helical cast steel gear with 400 helix angle has to transmit 80kW at 1800 rpm.
If the gear has 24 teeth, determine the necessary module, pitch diameter and face
width for 200 full depth. The static stress for cast steel may be taken as 56MPa.
The width of face may be taken as three times the normal pitch. What would be the
end thrust on the gear? The tooth factor for 20degree full depth involute gear may
be taken as 0.154-0.912/ no. of teeth.
[16]
7. (a) Name the devices in which a power screw forms a part; mentioning the appli-
cations of every.
(b) A double-threaded power screw, used for lifting the load, has a nominal di-
ameter of 32mm and pitch of 6mm. The coefficient of friction at the screw
threads is 0.12. Neglecting collar friction, compute
i. efficiency of the screw with square threads, and
ii. efficiency with ACME threads.
[6+10]
8. (a) elaborate the protecting devices for slide ways?
(b) A 4m long, 2m high and 0.3m wide lathe bed consists of 2 vertical walls
strengthened by perpendicular or diagonal stiffness. The thickness of the walls
is 70mm. While that of the stiffness is 45mm. compute the decreased bending
rigidity of the beds having perpendicular and diagonal stiffeners. [6+10]

Earning:   Approval pending.