Code No: V3215
Set No: 1
R07
III B.Tech. II Semester Su pplementary Examinations, November/December - 2012
DESI NG OF MECHINE MEMBERS-II
(Mechanical Engineering)
Time: 3 Hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
**
1
a) Explain briefly about
i) Full journal bearing ii) Fitted journal bearing
iii)Wedge film journal bearing.
b) The load on the journal bearing is 150 kN due to turbine shaft of 300 mm diameter
running at 1500 r.p.m. Determine the following : i) Length of the bearing if the
allowable bearing pressure is 1.6 N/mm2, and ii)Amount of heat to be removed by the
lubricant per minute if the bearing temperature is
60°C and viscosity of the oil at
60°C is 0.02 kg/m-s and the bearing clearance is 0.25 mm
[8+8M]
2
a) Design the Overhung Crankshaft when the crank is at an angle
of maximum
twisting moment?
b) The following section has been suggested for I-section connecting rod of a petrol
engine running at 2000r.p.m. The depth of the section is 25mm, the
width of the
flange is 40mm and the thickness of the flange and web 6mm. If the stroke of the
piston be 150mm, determine the maximum stress in the connecting rod if the length
connecting road be 300mm. The density of the material is 7800kg/m3
[8+8M]
3
Check the suitability of I-section 15mm × 12mm × 3mm for designing the connecting
rod in the case of single cylinder motor cycle engine of 40 mm bore and 50mm stroke
wherein the maximum pressure produced is 3.6 MPa and in which the connecting rod
is 4 times crank.
[16M]
4
a) Derive an expression for radius of neutral axis for T- section?
b) An open ring has T-section. It is subjected to a tensile load of 80kN
Fig. 1. Find the stresses at points P and Q.
Fig. 1
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as shown in
[8+8M]
Code No: V3215
R07
Set No: 1
5
Power of 60 kW at 650 r.p.m. is to be transmitted from an electric motor to
compressor shaft at 300 r.p.m. by V-belts. The approximate larger pulley diameter is
1500 mm. The approximate centre distance is 1650 mm, 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 350 mm2 and density 1000 kg / 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 300 mm from the nearest
bearing and is mounted on a shaft having a permissible shear stress of 40 MPa with
the help of a key. The shaft, the pulley and the key are also to be designed? [16M]
6
A pair of helical gears are to transmit 20 kW. The teeth are 20° stub in diametral
plane and have a helix angle of 45°. The pinion runs at 10,000 r.p.m. and has 80 mm
pitch diameter. The gear has 320 mm pitch diameter. If the gears are made of cast
steel having allowable static strength of 100 MPa; determine a suitable module and
face width from static strength considerations and check the gears for wear, given
σes = 618 MPa?
[16M]
7
a) Differentiate between differential screw and compound screw.
b) The lead screw of a lathe has square threads of 24 mm outside diameter and 5 mm
pitch. In order to drive the tool carriage, the screw exerts an axial pressure of 2.5 kN.
Find the efficiency of the screw and the power required to drive the screw, if it is to
rotate at 30 r.p.m. Neglect bearing friction. Assume coefficient of friction of screw
threads as 0.12.
[8+8M]
8 a) A bed is subjected to Torsional loading ,is constructed as a closed box type
structure. while a bed subjected to bending is constructed as an I -section. why? Give
mathematical proof to support your conclusion.
b) Write notes on stiffness and rigidity of machine tools.
[8+8M]
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Code No: V3215
R07
Set No: 2
III B.Tech. II Semester Supplementary Examinations, November/December - 2012
DESING OF MECHINE MEMBERS-II
(Mechanical Engineering)
Time: 3 Hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
**
1
a) Briefly explain the types of Journal bearings.
b) A bearing for a centrifugal pump has a diameter of 75 mm and a length of 120 mm.
The journal is machined so as to give a radial clearance of 0.0015 mm per mm radius.
The journal rotates at 1440 rpm and carries a total load of 10 kN. Oil is supplied with
a viscosity of 0.03 Pa-sec at the operating temperature. Determine the coefficient of
friction, the actual value of the bearing characteristic number, and the heat generated
in kJ/min
[4+12M]
2
a) What are various stresses induced in crank web?
b) The maximum connecting rod force on a steam engine running at 90 rpm is 70kN.
Determine the necessary size of the overhanging crank pin. Determine the diameter
of the crankshaft journal if the stroke is 0.90 m and distance between centerline of
bearing and pin is 0.36 m.
[8+8M]
3
Design a cast iron piston for a single acting four stroke engine from the following
data:
Cylinder bore
= 100mm
Stroke
= 120mm
Maximum gas pressure
= 5Mpa
Brake mean effective pressure
= 0.5Mpa
Fuel consumption
= 0.15kg/Brake power in kW/h
Speed
= 2200rpm
[16M]
4
Determine the maximum stress in the frame of the 100 kN punch press as shown
in the figure 1.
[16M]
Figure 1
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Code No: V3215
R07
Set No: 2
5
A rope drive is required to transmit 750 kW from a pulley of 1 m diameter running at
450 rpm. The safe pull in each rope is 2250 N and the mass of the rope is 1 kg/m
length. The angle of lap and the groove angle are 150 0 and 45 0 respectively. Find
the number of ropes required for the drive if the coefficient of friction between the
rope and the pulley is 0.3
[16M]
6
a) Explain the procedure of evaluating module and face width of the gear drive.
b) A pair of 4 diametra1 pitch, 200 full depth involute. Spur gears with a face width
of 60mm is made of steel having 400 HB. The pinion has 28 teeth and runs at 1200
rpm. The gear ratio is 4. What power can be transmitted as indicated by the Lewis
equation? Check for dynamic and wear loads. Assume σo = 210 MPa and σes = 70
Mpa
[8+8M]
7
A power screw having double start square threads of 25 mm nominal diameter and 5
mm pitch is acted upon by an axial load of 10 kN. The outer and inner diameters of
screw collar are 50 mm and 20 mm respectively. The coefficient of thread friction and
collar friction may be assumed as 0.2 and 0.15 respectively. The screw rotates at 12
r.p.m. Assuming uniform wear condition at the collar and allowable thread bearing
pressure of 5.8 N/mm2, find: i) the torque required to rotate the screw; ii) the stress in
the screw; and iii) the number of threads of nut in engagement with screw.?
[16M]
8
(a) What are the basic requirements of a machine tools?
(b) Explain the design procedure for Spindle
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[8+8M]
Code No: V3215
R07
Set No: 3
III B.Tech. II Semester Supplementary Examinations, November/December - 2012
DESING OF MECHINE MEMBERS-II
(Mechanical Engineering)
Time: 3 Hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
**
1
(a) A 100 mm long and 60 mm diameter journal bearing supports a load of 2500
N at 600 rpm. If the room temperature is 20oC, what should be the viscosity of
oil to limit the bearing surface temperature to 60oC? Diametral clearance =
0.06 mm. Energy dissipation coefficient based on the projected area of the
bearing = 210 W/m2/0C.
(b) A 250 × 250 mm bearing carries a load of 108 kN. The bearing rotates at
1500 rpm. The diametral clearance is 0.05 mm. For full journal bearing the power lost
in friction is 14.36 kW. Find the viscosity of the oil.
[8+ 8M]
2
Design a plain carbon steel centre crankshaft for a single acting four stroke single
cylinder engine for the following data: Bore = 400 mm ; Stroke = 600 mm ; Engine
speed = 200 r.p.m. ; Mean effective pressure = 0.5N/mm2; Maximum combustion
pressure = 2.5 N/mm2; Weight of flywheel used as a pulley = 50 kN; Total belt pull
= 6.5 kN. When the crank has turned through 35° from the top dead centre, the
pressure on the piston is 1N/mm2 and the torque on the crank is maximum. The ratio
of the connecting rod length to the crank radius is 5. Assume any other data required
for the design.?
[16M]
3
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:
(i) Bore and length of the cylinder ;
(ii) Thickness of the cylinder head ;
(iii) size of studs for the cylinder head.?
[16M]
4
The section of a crane hook is a rectangle 60 mm × 40 mm. The center of curvature of
the section is at a distance of 80 mm from the centroid of the section. A load of 15 kN
is acting through the center of curvature. Determine the maximum and minimum
bending stresses induced in the hook.
[16M]
5
a) What are factors that affect power transmission by a belt drive?
b) A V-belt drive consisting of two belts, operates on two pulleys of 0.3m and 0.45m
pitch diameters; the smaller pulley being the driver pulley. The centre distance of the
drive is 0.75m, and the groove angle of the pulley is 300. The cross-sectional area of
each belt is 510mm 2, and coefficient of friction is 0.25. The density of the belt
material is 1100kg/m3. The permissible stress for the belt material is 5N/mm2.
Determine the power that can be transmitted when the driver pulley is rotating at
1400rpm.
[4+12M]
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Code No: V3215
R07
Set No: 3
6
Design a spur gear drive required to transmit 45 kW at a pinion speed of 800 r.p.m.
The velocity ratio is 3.5 : 1. The teeth are 20° full-depth involute with 18 teeth on the
pinion. Both the pinion and gear are made of steel with a maximum safe static stress
of 180 MPa. Assume a safe stress of 40 MPa for the material of the shaft and key.
[16M]
7
A screw press is to be exerted a force of 40kN. The unsupported length of the screw is
400mm. Nominal diameter of screw is 50mm. The screw has square threads with
pitch equal to 10mm. The material of the screw and nut are medium carbon steel and
cast iron respectively. For the steel used take ultimate crushing stress as 320MPa,
yield stress in tension or compression as 200MPa and that are in shear as 120Mpa.
Allowable shear stress for CI is 20MPa and allowable bearing pressure between screw
and nut 12N/mm2. E for steel=210kN/mm 2. Determine the factor of safety of screw
against failure. Find the dimension of the nut. What is the efficiency of the
arrangement? Take coefficient of friction between steel and Cast iron.[16M]
8
a) A bed is subjected to Torsional loading is constructed as a closed box type
structure, while a bed subjected to bending is constructed as an I -section. why? Give
mathematical proof to support your conclusion.
b) Write notes on stiffness and rigidity of machine tools
[8+8M]
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Code No: V3215
R07
Set No: 4
III B.Tech. II Semester Supplementary Examinations, November/December - 2012
DESING OF MECHINE MEMBERS-II
(Mechanical Engineering)
Time: 3 Hours
Max Marks: 80
Answer any FIVE Questions
All Questions carry equal marks
**
1
A ball bearing subjected to a radial load of 4000 N is expected to have a satisfactory life
of 12 000 hours at 720 r.p.m. with a reliability of 95%. Calculate the dynamic load
carrying capacity of the bearing, so that it can be selected from manufacturer's
catalogue based on 90% reliability. If there are four such bearings each with a reliability
of 95% in a system, what is the reliability of the complete system?
[16M]
2
a) Explain about the whipping stress in connecting rod ?
b) The following data refer to a 4S single cylinder vertical diesel engine.
Piston diameter = 125 mm
Stroke = 150 mm
Length of connecting rod = 800 mm
Maximum Gas pressure at 5% of stroke = 500 N/mm2
Speed of the engine = 1200 rpm
Weight of the reciprocating parts = 45N
Design stress for material used = 80 N/mm2
Design bearing stress = 10 N/mm2
Design stress for bolts = 35 N/mm2
Design a suitable connecting rod and check for stress due to inertia.
[16M]
3
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 = 5 N/mm2 ; Indicated mean
effective pressure = 0.75 N/mm2 ; Mechanical efficiency = 80% ; Fuel consumption = 0.15 kg
per brake power per hour ; Higher calorific value of fuel = 42 × 103 kJ/kg ; Speed = 2000 r.p.m.
Any other data required for the design may be assumed.?
[16M]
4
The over hung crank of an engine having a cylinder diameter of 250 mm and stroke 400
mm. The connecting rod is 5 times crank, the maximum explosion pressure in the
cylinder is 1.7 MPa and engine runs at 200 rpm. Assuming a suitable stress for the
material design the-over hung crank. Also calculate the maximum stress in the crank
arm when the crank is at 30o to the I.D.C position and the gas pressure is 0.8 MPa. Take
modulus of section for rectangular section as 0.269bt2
[16M]
5
Design a belt pulley for transmitting 10kW at 180 rpm. The velocity of the belt is not to exceed
10m/s, and the maximum tension is not to exceed 15N/mm width. The tension on the slack side
is one half of that on the tight side. Determine all the principal dimensions of the pulley. [16M]
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Code No: V3215
R07
Set No: 4
6
The following particulars of a single reduction spur gear are given : Gear ratio = 10 : 1;
Distance between centres = 660 mm approximately; Pinion transmits 500 kW at 1800 r.p.m.;
Involute teeth of standard proportions (addendum = m) with pressure angle of 22.5°;
Permissible normal pressure between teeth = 175 N per mm of width. Find :
(i)
The nearest standard module if no interference is to occur;
(ii) The number of teeth on each wheel;
(iii) The necessary width of the pinion; and
(iv) The load on the bearings of the wheels due to power transmitted. [16M]
7
The cross bar of a planner weighing 12 kN is raised and lowered by means of two
square threaded screws of 38 mm outside diameter and 7 mm pitch. The screw is made
of steel and a bronze nut of 38 mm thick. A steel collar has 75 mm outside diameter and
38 mm inside diameter. The coefficient of friction at the threads is assumed as 0.11 and
at the collar 0.13. Find the force required at a radius of 100 mm to raise and lower the
load.
[16M]
8
(a) What type of material is suitable for slide ways? Give some important properties.
(b) Write a design procedure for the slide ways.
[8+8M]
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